Release 1.1.0

Barrel contacts for vias/THT pads (drill-wall ring injection, verified
against the analytic acosh spreading resistance), full solder-joint
modeling of every populated THT hole (lead conductor, solder fill,
one-sided pad coat, protruding-lead cone, exact pad shapes and DNP
flags read from KiCad), configurable cap-drill threshold, and README
model figures. The release now also attaches the docs/img figures.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.gitea/workflows/build-pcm.yml

@@ -35,11 +35,12 @@ jobs:
             dist/*.zip
             dist/metadata-registry.json
 
-      - name: Create release with the zip attached
+      - name: Create release with the zip, registry metadata and figures
         if: startsWith(github.ref, 'refs/tags/v')
         uses: akkuman/gitea-release-action@b8d9144f302c68610911db1aaf722708d5c02d94 # v1
         with:
           files: |
             dist/*.zip
             dist/metadata-registry.json
+            docs/img/*.png
           token: ${{ secrets.GITEA_TOKEN }}

README.md

@@ -11,6 +11,18 @@ potential, current density, and **power density**, reports **per-via
 currents** (via ampacity!) and total dissipation at a **selectable test
 current**. PNGs + a text summary are saved per run.
 
+![Current density on a two-layer demo net](docs/img/demo-current.png)
+*Real output on a synthetic two-layer net: current from a soldered
+THT-pad contact (V+, injected at the drill-wall ring) squeezes past a
+notch in the F.Cu pour, transfers through the stitching-via field into
+the B.Cu pour and leaves at the V− lug — per-via currents and the
+hottest via are reported.*
+
+![Potential on the two-layer demo net](docs/img/demo-potential.png)
+*The matching potential map with equipotential contour lines: they
+bunch where the field is strongest — nearly the whole 8.7 mV drop
+happens around the notch on F.Cu.*
+
 Uses the KiCad **IPC API** (`kicad-python` / `kipy`), not the deprecated
 SWIG API. Requires KiCad **10.0.1+**.
 
@@ -44,9 +56,10 @@ SWIG API. Requires KiCad **10.0.1+**.
    - **V+ rectangles on `User.1`**, **V− rectangles on `User.2`**
      (marker layers, configurable via `ELECTRODE_POS_LAYER` /
      `ELECTRODE_NEG_LAYER`), any number per side, axis-aligned;
-   - **pads** (real copper shape; through-hole pad contacts all layers,
-     SMD pad its own layer) — selected pads fill a side that has no
-     rectangles;
+   - **pads and vias** (SMD pad: real copper shape on its own layer;
+     through-hole pads and vias become **barrel contacts** — the current
+     enters at the drill wall on every spanned layer, see below) —
+     selected pads/vias fill a side that has no rectangles;
    - legacy: exactly 2 selected contacts with no marker rectangles still
      works; empty selection scans the whole board's marker layers.
 2. **Select the contacts**, click the **Fill Resistance** Ω button.
@@ -76,20 +89,46 @@ SWIG API. Requires KiCad **10.0.1+**.
   capped" checkbox** (default on, `VIAS_CAPPED`) the mouth carries a
   thin copper cap (`CAP_PLATING_UM = 15`, fab spec) on the **outer**
   layers and is an open hole on inner layers; unchecked, mouths are open
-  holes everywhere. Layer-to-layer the cap never matters at DC (it is in
+  holes everywhere. The fab caps only small vias: drills above the
+  dialog's **"capped up to drill"** threshold (default
+  `CAP_MAX_DRILL_MM = 0.5`) keep open mouths even with capping
+  selected. Layer-to-layer the cap never matters at DC (it is in
   parallel with the annular-ring contact, not in series) — the checkbox
   only affects in-plane conduction across outer-layer mouths. Sub-cell
   mouths scale their cells' sheet conductance by the true covered
   fraction (4×4 supersampling), so coarse grids see the correct small
-  perturbation instead of a whole-cell hole. THT-pad copper and drills
-  remain outside the model; at f > 0 the thickness scaling is applied
-  multiplicatively to the skin-corrected sheet conductance
+  perturbation instead of a whole-cell hole. Barrels are gathered in
+  **single-layer runs too** (drill mouths perforate a lone plane).
+  **THT pads are fully modeled**: their exact copper shapes (incl.
+  oblong pads, fetched from KiCad; the outer shape stands in for inner
+  rings) are stamped onto every included layer, and every **populated**
+  pad carries its full **soldered joint** on its SOLDER side (opposite
+  the component; the component-side pad face stays bare): the hole
+  holds the **component lead** (a cylinder of drill −
+  `THT_LEAD_CLEARANCE_MM`, resistivity `THT_LEAD_RHO_OHM_M`, copper by
+  default — raise it for brass/steel leads) **plus solder** in the
+  remaining annulus, both in parallel with the plating; the mouth
+  copper stays conducting (it stands in for the plug — conservative,
+  the plug is worth far more than the foil); the pad face gets the
+  average-thickness solder coat (exact pad shape) and the
+  protruding-lead cone (see barrel contacts below; on oblong pads the
+  cone tapers within the inscribed circle). Whether a hole is a via or
+  a THT pad, the owning footprint's side, and its **Do not populate**
+  flag are all read from KiCad — **DNP pads** get an **open hole** and
+  a plating-only barrel, no joint. At f > 0 the thickness scaling is
+  applied multiplicatively to the skin-corrected sheet conductance
   (approximation). Per layer a barrel attaches to
   the fill cell under it, or to the nearest copper cell within the pad
   footprint plus one grid cell — fills joined by **thermal-relief
   spokes** still connect; wider antipads do not, and the barrel bridges
   the layers above/below with the full barrel length. Barrels that reach
   fill on fewer than two layers carry no current and are reported.
+
+  ![How drilled holes are modeled — cross-section](docs/img/hole-model.png)
+  *The four hole types: capped small via, open large via, populated THT
+  pad with its full solder joint (lead ∥ solder ∥ plating in the hole,
+  one-sided pad coat, protruding-lead solder cone), and a DNP THT pad.*
+
 - The net's **traces** (straight and arc tracks, exact outline polygons
   incl. rounded ends) conduct together with the fills — dialog checkbox,
   on by default (`INCLUDE_TRACKS`). Traces narrower than
@@ -98,8 +137,9 @@ SWIG API. Requires KiCad **10.0.1+**.
   series resistance carries no discretization error and no cell-size
   tuning is needed for thin traces. 1D-modeled traces show potential,
   power density, and |J| (the true in-trace density from the link
-  currents, |ΔV|/(ρ·Δl)). Pad copper other than the selected
-  contacts is still **not** part of the conductor model.
+  currents, |ΔV|/(ρ·Δl)). THT pad copper is part of the conductor
+  (exact shapes, see above); **SMD** pad copper other than the
+  selected contacts is still **not**.
 - **Solder buildup on mask openings** (dialog checkbox, **off by
   default**; `INCLUDE_MASK_BUILDUP`): zones drawn on `F.Mask`/`B.Mask`
   are treated as mask openings that collect `SOLDER_THICKNESS_UM`
@@ -110,6 +150,28 @@ SWIG API. Requires KiCad **10.0.1+**.
   interface faces use harmonic-mean conductances. Buildup areas render
   tin-gray on the raster map; |J| in them is referenced to the
   conductance-equivalent copper thickness.
+- **Barrel contacts**: a selected **via or through-hole pad** injects at
+  the **drill-wall ring** on every layer the barrel spans — the current
+  physically enters through the lead/wire soldered into the hole, so
+  the spreading resistance across the pad and surrounding pour is part
+  of the result (both contact models; verified against
+  R = ρ/(π·t)·acosh(d/2a) for two circular contacts on a sheet). A
+  soldered **THT joint** additionally assumes the **hole is filled with
+  solder** (core in parallel with the plating) and the **pad face on
+  the solder side carries an average-thickness solder coat**
+  (`SOLDER_THICKNESS_UM`, 50 µm) over the modeled copper under the pad
+  shape — the solder side is the side opposite the component (taken
+  from the owning footprint; assumed `B.Cu` if it cannot be found),
+  and the component-side pad face stays bare. There the **clipped
+  lead protrudes** `THT_LEAD_PROTRUSION_MM` (1.5 mm, 0 = off)
+  and a **solder cone** wraps
+  it: full protrusion height at the drill wall, tapering linearly to
+  zero at the pad edge, applied as extra conduction-equivalent copper
+  per cell. The tall solder column at the wall pulls the joint
+  vicinity to lead potential — equivalent to extending the barrel wall
+  vertically — while the taper carries the radial spreading. To model
+  a probe pressed onto the pad face instead, draw a marker rectangle
+  over the pad.
 - **Contact models** (dialog / `CONTACT_MODEL`): default **uniform
   injection** — a conductor pressed on top feeds the current orthogonally
   with uniform surface density, so |J| ramps across the contact area
@@ -120,6 +182,12 @@ SWIG API. Requires KiCad **10.0.1+**.
   terminals (e.g. planes joined only through the bolted lugs), only the
   equipotential model is well-defined; the uniform model stops with an
   error instead of prescribing an arbitrary split.
+
+  ![The two contact models bracket a real contact](docs/img/contact-models.png)
+  *|J| around the same 3×3 mm contact under both models: the ideal
+  bonded lug crowds the current at the contact edges (no in-sheet
+  current inside an equipotential region), the pressed conductor ramps
+  it across the contact area.*
 - Fields are reported at the dialog's test current; power scales with I².
 - **Skin effect (f > 0)**: per-layer effective sheet resistance from the
   exact 1D foil-diffusion solution `Zs = τρ·coth(τt)`, `τ = (1+j)/δ`
@@ -158,6 +226,12 @@ SWIG API. Requires KiCad **10.0.1+**.
   uniform grid ≲ 0.03 %, with the power-balance identity intact. All
   fields are expanded back to the fine grid for the maps and reports.
 
+  ![Rasterized map with the adaptive mesh overlay](docs/img/demo-raster.png)
+  *The raster map of the demo net: quadtree leaves drawn on the copper
+  (fine at boundaries, electrodes, via mouths and pads; coarse blocks
+  in plane interiors), the tin-gray solder coat of the THT-pad contact
+  P1, and the via field with its pad copper.*
+
 ## Offline / development
 
 Every run writes `geometry_dump.json`; re-solve without KiCad:
@@ -188,7 +262,10 @@ filled in. To publish: upload the zip to a release, set `download_url`
 (and the `homepage` resource in `metadata.json`), then submit the
 registry copy as `packages/th.co.b4l.fill-resistance/metadata.json` in a
 merge request to <https://gitlab.com/kicad/addons/metadata>. Icons are
-regenerated with `python tools/gen_icons.py`.
+regenerated with `python tools/gen_icons.py`; the README figures in
+`docs/img/` with `.venv\Scripts\python.exe tools\gen_readme_figs.py`
+(real solver output on small synthetic boards, plus the hand-drawn
+hole cross-section).
 
 ## License
 

docs/RELEASING.md

@@ -0,0 +1,67 @@
+# Releasing a new version
+
+The PCM addon zip is built by CI (`.gitea/workflows/build-pcm.yml`).
+Every push to `main` builds it as a downloadable artifact; pushing a
+`v<version>` tag additionally creates a Gitea release with the zip
+attached. The release job checks that the tag matches `metadata.json`
+and fails on a mismatch.
+
+## Steps
+
+1. **Bump the version** in `metadata.json` — the single entry in
+   `versions` (plain `MAJOR.MINOR.PATCH`, no `v` prefix; the PCM schema
+   rejects anything else):
+
+   ```json
+   "versions": [
+       {
+           "version": "1.0.2",
+           "status": "stable",
+           "kicad_version": "10.0",
+           "runtime": "ipc"
+       }
+   ]
+   ```
+
+2. **Commit, tag, push** (tag = `v` + the manifest version):
+
+   ```powershell
+   git add metadata.json
+   git commit -m "Release 1.0.2"
+   git tag v1.0.2
+   git push
+   git push origin v1.0.2
+   ```
+
+3. **Verify**: the Actions run for the tag builds
+   `th.co.b4l.fill-resistance_<version>.zip` and publishes it at
+   <https://git.b4l.co.th/B4L/kicad-zone-resistance/releases>, together
+   with `metadata-registry.json`. The zip installs directly via
+   Plugin and Content Manager → *Install from File*.
+
+## Publishing to the official KiCad registry (optional)
+
+The attached `metadata-registry.json` already carries the release
+`download_url`, `download_sha256` and sizes. Submit it as
+`packages/th.co.b4l.fill-resistance/metadata.json` in a merge request
+to <https://gitlab.com/kicad/addons/metadata>. The registry keeps every
+published version: append the new entry to the `versions` array of the
+registry copy instead of replacing the previous one (the repo's own
+`metadata.json` only ever holds the current version —
+`tools/build_package.py` reads `versions[0]`).
+
+## Local build (no CI)
+
+```powershell
+python tools/build_package.py    # writes dist/<identifier>_<version>.zip
+```
+
+Pure stdlib — no venv needed. `dist/` is gitignored.
+
+## CI prerequisites (one-time, server side)
+
+- Actions enabled for the repo (Settings → Actions unit).
+- A runner registered with the `ubuntu-latest` label; the default
+  act_runner image works — the build needs only Python 3.
+- Workflow actions are pinned to commit SHAs; when bumping them, update
+  the SHA and the trailing version comment together.

fill_resistance/board_io.py

@@ -11,7 +11,7 @@ from pathlib import Path
 
 from kipy import KiCad
 from kipy.board import Board
-from kipy.board_types import ArcTrack, BoardRectangle, Pad
+from kipy.board_types import ArcTrack, BoardRectangle, Pad, Via
 from kipy.proto.board.board_pb2 import BoardStackupLayerType
 from kipy.proto.board.board_types_pb2 import ZoneType
 from kipy.util.board_layer import (canonical_name, is_copper_layer,
@@ -22,7 +22,9 @@ import numpy as np
 from . import config
 from .errors import ApiVersionError, CandidateError, SelectionError
 from .geometry import (Electrode, LayerFill, Polygon, Problem, Rect,
-                       SurfaceBuildup, TrackSeg, ViaLink, linearize_ring)
+                       SurfaceBuildup, TrackSeg, ViaLink,
+                       contact_solder_buildups, linearize_ring,
+                       tht_joint_buildups)
 
 MASK_TO_COPPER = {"F.Mask": "F.Cu", "B.Mask": "B.Cu"}
 
@@ -179,7 +181,42 @@ def _pad_polygons(board: Board, pad: Pad, contact: str) -> list[Polygon] | None:
     return None
 
 
-def _to_electrode(board: Board, item) -> Electrode:
+def _footprint_pad_map(footprints) -> dict:
+    """(x, y, number) -> owning FootprintInstance. Footprint pads are
+    stored with absolute positions, so the lookup is exact."""
+    out = {}
+    for fp in footprints or []:
+        try:
+            for fpad in fp.definition.pads:
+                out[(fpad.position.x, fpad.position.y, fpad.number)] = fp
+        except Exception:
+            continue
+    return out
+
+
+def _pad_owner(pad: Pad, pad_map: dict):
+    return pad_map.get((pad.position.x, pad.position.y, pad.number))
+
+
+def _tht_protrusion_side(pad: Pad, pad_map: dict, quiet: bool = False) -> str:
+    """Outer layer where the clipped THT lead protrudes (tent + solder
+    cone): the side OPPOSITE the component. Unknown owner -> assume the
+    component sits on F.Cu (lead tents on B.Cu)."""
+    fp = _pad_owner(pad, pad_map)
+    if fp is not None:
+        try:
+            side = canonical_name(fp.layer)
+            return "F.Cu" if side == "B.Cu" else "B.Cu"
+        except Exception:
+            pass
+    if not quiet:
+        print(f"note: no footprint found for pad {pad.number} - assuming "
+              f"its lead protrudes on B.Cu")
+    return "B.Cu"
+
+
+def _to_electrode(board: Board, item, stackup: StackupInfo | None = None,
+                  pad_map: dict | None = None) -> Electrode:
     if isinstance(item, BoardRectangle):
         tl, br = item.top_left, item.bottom_right
         rect = Rect.normalized(tl.x, tl.y, br.x, br.y,
@@ -188,6 +225,22 @@ def _to_electrode(board: Board, item) -> Electrode:
         cy = (rect.y0 + rect.y1) / 2e6
         return Electrode(rect=rect, contact="all",
                          label=f"rect({cx:.1f},{cy:.1f})")
+    if isinstance(item, Via):
+        via: Via = item
+        x, y = via.position.x, via.position.y
+        drill = int(via.drill_diameter or 0) or _pad_drill_nm(via)
+        if drill <= 0:
+            raise SelectionError(
+                f"Selected via at ({x / 1e6:.2f}, {y / 1e6:.2f}) mm has no "
+                f"drill diameter - cannot use it as a contact.")
+        pad_nm = _padstack_pad_nm(via)
+        r = max(pad_nm, drill) // 2
+        rect = Rect.normalized(x - r, y - r, x + r, y + r, "via")
+        return Electrode(
+            rect=rect, contact="all", label=f"via({x / 1e6:.1f},{y / 1e6:.1f})",
+            drill_nm=drill, pad_nm=pad_nm, center=(x, y),
+            barrel_z=(_padstack_span(via.padstack, stackup)
+                      if stackup is not None else None))
     # Pad
     pad: Pad = item
     contact = _pad_default_contact(pad)
@@ -197,37 +250,56 @@ def _to_electrode(board: Board, item) -> Electrode:
     if box is None:
         raise SelectionError(f"Could not get the bounding box of {label}.")
     rect = _box2_to_rect(box, "pad")
+    drill = _pad_drill_nm(pad)
     return Electrode(rect=rect, contact=contact,
-                     polygons=_pad_polygons(board, pad, contact), label=label)
+                     polygons=_pad_polygons(board, pad, contact), label=label,
+                     # through-hole pad: current enters at the soldered
+                     # barrel; the joint is solder-filled + pad-coated,
+                     # with a solder cone around the protruding lead
+                     drill_nm=drill, pad_nm=_padstack_pad_nm(pad),
+                     pad_min_nm=_padstack_pad_min_nm(pad),
+                     center=(pad.position.x, pad.position.y),
+                     solder=drill > 0,
+                     protrusion_side=(_tht_protrusion_side(pad, pad_map or {})
+                                      if drill > 0 else None))
 
 
-def _net_hint_of(pads: list[Pad]) -> str | None:
-    for pad in pads:
-        if pad.net is not None:
-            return pad.net.name
+def _net_hint_of(items: list) -> str | None:
+    for item in items:
+        if item.net is not None:
+            return item.net.name
     return None
 
 
-def get_electrodes(board: Board
+def get_electrodes(board: Board, stackup: StackupInfo | None = None
                    ) -> tuple[list[Electrode], list[Electrode], str | None]:
     """Terminals from the selection. Each terminal may have MULTIPLE parts
     (all merged into one externally-bonded contact):
 
     - rectangles on ELECTRODE_POS_LAYER -> V+ parts, on ELECTRODE_NEG_LAYER
-      -> V- parts; selected pads fill a side that has no rectangles;
+      -> V- parts; selected pads/vias fill a side that has no rectangles;
     - no marker rectangles selected: legacy mode, exactly 2 items
-      (rects/pads, any layer) -> one part each;
+      (rects/pads/vias, any layer) -> one part each;
     - empty selection: board-wide scan of both marker layers.
+
+    Selected vias and through-hole pads become BARREL contacts: current
+    enters at the drill-wall ring (the soldered lead/wire), not the pad
+    face. Draw a marker rectangle over the pad instead to model a probe
+    pressed onto the pad face.
     """
     pos_l = config.ELECTRODE_POS_LAYER
     neg_l = config.ELECTRODE_NEG_LAYER
     scheme = (f"Draw V+ rectangle(s) on {pos_l} and V- rectangle(s) on "
-              f"{neg_l} (axis-aligned), and/or select pads for a side "
+              f"{neg_l} (axis-aligned), and/or select pads/vias for a side "
               f"without rectangles.")
 
     selection = list(board.get_selection())
     rects = [s for s in selection if isinstance(s, BoardRectangle)]
-    pads = [s for s in selection if isinstance(s, Pad)]
+    pads = [s for s in selection if isinstance(s, (Pad, Via))]
+    # protrusion-side lookup needs the owning footprints (THT pads only)
+    pad_map = (_footprint_pad_map(board.get_footprints())
+               if any(isinstance(s, Pad) and _pad_drill_nm(s) > 0
+                      for s in pads) else {})
 
     if not selection:
         allr = [s for s in board.get_shapes() if isinstance(s, BoardRectangle)]
@@ -258,12 +330,13 @@ def get_electrodes(board: Board
         es2 = [_to_electrode(board, r) for r in neg]
         if pads and es1 and es2:
             raise SelectionError(
-                f"Cannot assign the {len(pads)} selected pad(s): both marker "
-                f"layers already provide rectangles. Use pads only for a "
-                f"side that has none."
+                f"Cannot assign the {len(pads)} selected pad(s)/via(s): both "
+                f"marker layers already provide rectangles. Use pads/vias "
+                f"only for a side that has none."
             )
         if pads:
-            pad_parts = [_to_electrode(board, p) for p in pads]
+            pad_parts = [_to_electrode(board, p, stackup, pad_map)
+                         for p in pads]
             if not es1:
                 es1 = pad_parts
             else:
@@ -277,12 +350,13 @@ def get_electrodes(board: Board
 
     items = rects + pads
     if len(items) == 2:
-        return ([_to_electrode(board, items[0])],
-                [_to_electrode(board, items[1])], _net_hint_of(pads))
+        return ([_to_electrode(board, items[0], stackup, pad_map)],
+                [_to_electrode(board, items[1], stackup, pad_map)],
+                _net_hint_of(pads))
     raise SelectionError(
         f"The selection has {len(rects)} rectangle(s) (none on the marker "
-        f"layers) and {len(pads)} pad(s); without marker layers exactly 2 "
-        f"contacts are needed.\n{scheme}"
+        f"layers) and {len(pads)} pad(s)/via(s); without marker layers "
+        f"exactly 2 contacts are needed.\n{scheme}"
     )
 
 
@@ -416,6 +490,18 @@ def _padstack_pad_nm(item) -> int:
         return 0
 
 
+def _padstack_pad_min_nm(item) -> int:
+    """Smallest dimension of the (largest) copper pad of a padstack; 0
+    if unknown. Bounds the lead-cone taper on oblong pads: the cone
+    stays within the inscribed circle."""
+    try:
+        sizes = [min(int(l.size.x), int(l.size.y))
+                 for l in item.padstack.copper_layers]
+        return max(sizes) if sizes else 0
+    except Exception:
+        return 0
+
+
 def _padstack_span(padstack, stackup: StackupInfo) -> tuple[int, int]:
     """(z_top, z_bot) of the barrel; falls back to the full stack."""
     try:
@@ -444,19 +530,58 @@ def gather_barrels(board: Board, net_name: str,
                                z_bot_nm=z_bot, kind="via",
                                pad_nm=_padstack_pad_nm(via)))
     if config.INCLUDE_TH_PADS:
-        for pad in board.get_pads():
-            if pad.net is None or pad.net.name != net_name:
-                continue
-            drill = _pad_drill_nm(pad)
-            if drill <= 0:
-                continue
-            barrels.append(ViaLink(x=pad.position.x, y=pad.position.y,
-                                   drill_nm=drill, z_top_nm=-1,
+        net_pads = [pad for pad in board.get_pads()
+                    if pad.net is not None and pad.net.name == net_name
+                    and _pad_drill_nm(pad) > 0]
+        # populated (non-DNP) THT pads carry a soldered joint: filled
+        # hole + coat + lead cone on the side opposite the component
+        pad_map = (_footprint_pad_map(board.get_footprints())
+                   if net_pads else {})
+        unknown = 0
+        for pad in net_pads:
+            fp = _pad_owner(pad, pad_map)
+            unknown += fp is None
+            populated = True
+            if fp is not None:
+                try:
+                    populated = not fp.attributes.do_not_populate
+                except Exception:
+                    pass
+            barrels.append(ViaLink(
+                x=pad.position.x, y=pad.position.y,
+                drill_nm=_pad_drill_nm(pad), z_top_nm=-1,
                 z_bot_nm=stackup.z_bot_nm + 1, kind="pad",
-                                   pad_nm=_padstack_pad_nm(pad)))
+                pad_nm=_padstack_pad_nm(pad),
+                pad_min_nm=_padstack_pad_min_nm(pad),
+                solder_filled=populated,
+                protrusion_side=(_tht_protrusion_side(pad, pad_map,
+                                                      quiet=True)
+                                 if populated else None)))
+        if unknown:
+            print(f"note: {unknown} THT pad(s) without an identifiable "
+                  f"footprint - assumed populated, leads on B.Cu")
     return barrels
 
 
+def gather_tht_pad_copper(board: Board, net_name: str
+                          ) -> dict[tuple[int, int], list[Polygon]]:
+    """(x, y) -> exact copper shape(s) of every drilled (THT) pad on the
+    net. The annular-ring copper conducts on every layer the barrel
+    spans, so build_problem stamps these onto each included layer. One
+    API call per pad; the outer-layer shape stands in for the inner
+    rings (approximation - inner rings are usually the same or
+    smaller)."""
+    shapes: dict[tuple[int, int], list[Polygon]] = {}
+    for pad in board.get_pads():
+        if pad.net is None or pad.net.name != net_name \
+                or _pad_drill_nm(pad) <= 0:
+            continue
+        polys = _pad_polygons(board, pad, "all")
+        if polys:
+            shapes[(pad.position.x, pad.position.y)] = polys
+    return shapes
+
+
 # --- top level ----------------------------------------------------------------
 
 def build_problem(board: Board, net: str, layer_names: list[str],
@@ -465,7 +590,8 @@ def build_problem(board: Board, net: str, layer_names: list[str],
                   buildups: dict[str, list[Polygon]] | None = None,
                   extra_cu_um: float | None = None,
                   tracks: dict | None = None,
-                  vias_capped: bool | None = None) -> Problem:
+                  vias_capped: bool | None = None,
+                  cap_max_drill_mm: float | None = None) -> Problem:
     per_layer = fills.get(net, {})
     per_layer_tracks = (tracks or {}).get(net, {})
     layers = []
@@ -490,7 +616,19 @@ def build_problem(board: Board, net: str, layer_names: list[str],
             f"Net {net} has no fill on any of the selected layers "
             f"({', '.join(layer_names)})."
         )
-    vias = gather_barrels(board, net, stackup) if len(layers) > 1 else []
+    # barrels matter on a single layer too: via rings + drill mouths
+    # perforate the plane, THT joints locally stiffen it
+    vias = gather_barrels(board, net, stackup)
+    # THT pad copper is part of the conductor: stamp the exact pad
+    # shapes onto every included layer (the barrel spans the stack)
+    pad_shapes = (gather_tht_pad_copper(board, net)
+                  if any(v.kind == "pad" for v in vias) else {})
+    if pad_shapes:
+        extra = [poly for polys in pad_shapes.values() for poly in polys]
+        for layer in layers:
+            layer.polygons = list(layer.polygons) + extra
+        print(f"{len(pad_shapes)} THT pad shape(s) stamped on every "
+              f"included layer")
     included = {l.layer_name for l in layers}
     buildup_list = [
         SurfaceBuildup(layer_name=name, polygons=polys)
@@ -502,7 +640,7 @@ def build_problem(board: Board, net: str, layer_names: list[str],
           + (f", solder buildup on "
              f"{', '.join(b.layer_name for b in buildup_list)}"
              if buildup_list else ""))
-    return Problem(
+    problem = Problem(
         board_path=board.name or "",
         net_name=net,
         rho_ohm_m=config.RHO_CU_OHM_M,
@@ -522,7 +660,34 @@ def build_problem(board: Board, net: str, layer_names: list[str],
         vias_capped=(vias_capped if vias_capped is not None
                      else config.VIAS_CAPPED),
         cap_plating_nm=int(config.CAP_PLATING_UM * 1000),
+        cap_max_drill_nm=int((cap_max_drill_mm if cap_max_drill_mm is not None
+                              else config.CAP_MAX_DRILL_MM) * 1e6),
+        tht_protrusion_nm=int(config.THT_LEAD_PROTRUSION_MM * 1e6),
+        tht_lead_clearance_nm=int(config.THT_LEAD_CLEARANCE_MM * 1e6),
+        tht_lead_rho_ohm_m=config.THT_LEAD_RHO_OHM_M,
     )
+    solder_layers = contact_solder_buildups(problem)
+    if solder_layers:
+        sides = sorted({e.protrusion_side
+                        for e in problem.electrodes1 + problem.electrodes2
+                        if e.solder and e.protrusion_side})
+        cone = (f", {config.THT_LEAD_PROTRUSION_MM:g} mm lead + solder cone "
+                f"on {', '.join(sides)}"
+                if sides and problem.tht_protrusion_nm > 0 else "")
+        print(f"THT contact(s): solder-filled hole + "
+              f"{config.SOLDER_THICKNESS_UM:g} um average solder coat on the "
+              f"pad face ({', '.join(solder_layers)}){cone}")
+    tht_joint_buildups(problem, pad_shapes)
+    n_joint = sum(1 for v in problem.vias
+                  if v.kind == "pad" and v.solder_filled)
+    n_dnp = sum(1 for v in problem.vias
+                if v.kind == "pad" and not v.solder_filled)
+    if n_joint or n_dnp:
+        print(f"{n_joint} populated THT pad joint(s): lead + solder in the "
+              f"hole, coat + cone on the solder side"
+              + (f"; {n_dnp} DNP pad(s): open hole, plating-only"
+                 if n_dnp else ""))
+    return problem
 
 
 if __name__ == "__main__":
@@ -533,7 +698,7 @@ if __name__ == "__main__":
     out = Path(sys.argv[1]) if len(sys.argv) > 1 else Path("geometry_dump.json")
     _, board = connect()
     stackup = get_stackup_info(board)
-    es1, es2, net_hint = get_electrodes(board)
+    es1, es2, net_hint = get_electrodes(board, stackup)
     if any_zone_unfilled(board):
         refill(board)
     fills = gather_net_fills(board)

fill_resistance/config.py

@@ -28,7 +28,25 @@ VIAS_CAPPED = True              # filled + capped vias (dialog checkbox):
                                 # Ring/pad copper of vias is modeled either
                                 # way; THT-pad copper/drills are not.
 CAP_PLATING_UM = 15.0           # cap plating thickness (fab spec)
-INCLUDE_TH_PADS = True          # plated through-hole pads stitch layers too
+CAP_MAX_DRILL_MM = 0.5          # fab caps only small vias: drills above this
+                                # stay open even with VIAS_CAPPED
+                                # (dialog-settable)
+INCLUDE_TH_PADS = True          # plated through-hole pads stitch layers too;
+                                # their holes are modeled solder-filled (a
+                                # soldered component lead), so the solder core
+                                # conducts in parallel with the plating
+THT_LEAD_PROTRUSION_MM = 1.5    # clipped THT lead protrusion on the side
+                                # opposite the component: a solder cone of
+                                # this height at the drill wall (tapering to
+                                # zero at the pad edge) wraps the lead of
+                                # every populated THT pad. 0 = no cones
+THT_LEAD_CLEARANCE_MM = 0.25    # hole diameter minus lead diameter (fab
+                                # rule): a lead cylinder of drill - this
+                                # conducts inside every solder-filled hole
+THT_LEAD_RHO_OHM_M = 1.68e-8    # lead material resistivity: copper leads/
+                                # wires; brass ~6.4e-8, phosphor bronze
+                                # ~1.1e-7, copper-clad steel higher - raise
+                                # this if your components use such leads
 SKIN_SIDES = 1                  # skin-effect field config: 1 = plane facing a
                                 # return plane (conservative), 2 = isolated foil
 

fill_resistance/dialog.py

@@ -37,6 +37,7 @@ class Selection:
     extra_cu_um: float = 0.0
     include_tracks: bool = True
     vias_capped: bool = True
+    cap_max_drill_mm: float = 0.5
     adaptive: bool = False
 
 
@@ -73,6 +74,11 @@ class _Dialog(QDialog):
         self.capped_check.setChecked(config.VIAS_CAPPED)
         form.addRow("Vias:", self.capped_check)
 
+        self.cap_drill_edit = QLineEdit(f"{config.CAP_MAX_DRILL_MM:g}")
+        self.cap_drill_edit.setEnabled(config.VIAS_CAPPED)
+        self.capped_check.toggled.connect(self.cap_drill_edit.setEnabled)
+        form.addRow("Capped up to drill [mm]:", self.cap_drill_edit)
+
         self.adaptive_check = QCheckBox(
             "adaptive cells (coarsen plane interiors; faster on large "
             "boards, corrected to ≲0.1 % of the uniform grid)")
@@ -205,6 +211,11 @@ class _Dialog(QDialog):
             extra_cu = number(self.extracu_edit, "Extra Cu")
             if extra_cu < 0:
                 raise ValueError("Extra Cu must be ≥ 0 µm.")
+        cap_max_drill = config.CAP_MAX_DRILL_MM
+        if self.capped_check.isChecked():
+            cap_max_drill = number(self.cap_drill_edit, "Capped up to drill")
+            if cap_max_drill <= 0:
+                raise ValueError("Capped-up-to drill must be > 0 mm.")
 
         def contact(box: QComboBox) -> str:
             t = box.currentText()
@@ -222,6 +233,7 @@ class _Dialog(QDialog):
                          extra_cu_um=extra_cu,
                          include_tracks=self.tracks_check.isChecked(),
                          vias_capped=self.capped_check.isChecked(),
+                         cap_max_drill_mm=cap_max_drill,
                          adaptive=self.adaptive_check.isChecked())
 
     def _try_accept(self) -> None:

fill_resistance/geometry.py

@@ -17,7 +17,7 @@ from pathlib import Path
 
 import numpy as np
 
-JSON_SCHEMA_VERSION = 5
+JSON_SCHEMA_VERSION = 6
 
 
 @dataclass(frozen=True)
@@ -93,16 +93,39 @@ class TrackSeg:
 
 @dataclass
 class Electrode:
-    """One PART of a current-injection terminal: a drawn rectangle or a
-    selected pad. A terminal (V+ or V-) is a LIST of parts, all merged
-    into one equipotential contact (externally bonded). `polygons`
-    (board nm) is the exact copper shape when known (pads); None means
-    the rectangle itself is the shape. `contact` = 'all' or a layer
-    name: which included layers this part touches."""
+    """One PART of a current-injection terminal: a drawn rectangle, a
+    selected pad, or a selected via. A terminal (V+ or V-) is a LIST of
+    parts, all merged into one equipotential contact (externally
+    bonded). `polygons` (board nm) is the exact copper shape when known
+    (pads); None means the rectangle itself is the shape. `contact` =
+    'all' or a layer name: which included layers this part touches.
+
+    drill_nm > 0 marks a BARREL contact (selected via or through-hole
+    pad): the current physically enters through the plated barrel (the
+    lead/wire soldered into the hole), so the contact cells are the
+    copper ring at the drill wall, not the whole pad face. `solder`
+    additionally models a soldered THT joint: the hole is filled with
+    solder and the pad face on the SOLDER side (protrusion_side,
+    opposite the component) carries an average-thickness solder coat
+    (Problem.solder_thickness_nm over `polygons`) plus the
+    protruding-lead cone."""
     rect: Rect                                # bounding box (labels/summary)
     contact: str = "all"
     polygons: list[Polygon] | None = None
     label: str = "rect"
+    drill_nm: int = 0                         # >0: barrel contact
+    pad_nm: int = 0                           # pad diameter (search bound;
+                                              # largest dimension if oblong)
+    pad_min_nm: int = 0                       # smallest pad dimension (cone
+                                              # taper bound); 0 = pad_nm
+    center: tuple[int, int] | None = None     # drill center; None = rect center
+    barrel_z: tuple[int, int] | None = None   # (z_top, z_bot); None = full stack
+    solder: bool = False                      # soldered THT joint (see above)
+    protrusion_side: str | None = None        # outer layer where the clipped
+                                              # lead protrudes (opposite the
+                                              # component): a solder cone
+                                              # wraps it there, see
+                                              # Problem.tht_protrusion_nm
 
 
 @dataclass
@@ -116,16 +139,43 @@ class ViaLink:
     z_bot_nm: int
     kind: str = "via"                         # "via" | "pad"
     pad_nm: int = 0                           # pad/annular diameter; 0 = unknown
+                                              # (oblong pads: LARGEST dimension,
+                                              # used as a search bound)
+    pad_min_nm: int = 0                       # smallest pad dimension (bounds
+                                              # the lead-cone taper on oblong
+                                              # pads); 0 = same as pad_nm
+    solder_filled: bool = False               # populated THT pad: the hole
+                                              # holds lead + solder (in parallel
+                                              # with the plating); False for
+                                              # vias and DNP footprints
+    protrusion_side: str | None = None        # populated THT pad: outer layer
+                                              # where the clipped lead tents
+                                              # (solder cone), opposite the
+                                              # component side
 
     def spans(self, z_nm: int) -> bool:
         return self.z_top_nm - 1 <= z_nm <= self.z_bot_nm + 1
 
     def barrel_resistance(self, length_nm: int, rho_ohm_m: float,
-                          plating_nm: int) -> float:
+                          plating_nm: int,
+                          solder_rho_ohm_m: float | None = None,
+                          lead_nm: float = 0,
+                          lead_rho_ohm_m: float | None = None) -> float:
         """Barrel segment resistance over length_nm: thin-wall annulus of
-        plating around the drill."""
-        area_m2 = math.pi * (self.drill_nm * 1e-9) * (plating_nm * 1e-9)
-        return rho_ohm_m * (length_nm * 1e-9) / area_m2
+        plating around the drill. With solder_rho_ohm_m the hole holds a
+        soldered THT joint: the component lead (a cylinder of lead_nm
+        diameter, resistivity lead_rho_ohm_m) and the solder filling the
+        remaining annulus conduct in parallel with the plating."""
+        ga = math.pi * (self.drill_nm * 1e-9) * (plating_nm * 1e-9) \
+            / rho_ohm_m                       # conductance-area [m^2/ohm-m]
+        if solder_rho_ohm_m is not None:
+            r_core = max(self.drill_nm / 2.0 - plating_nm, 0.0) * 1e-9
+            r_lead = min(lead_nm * 1e-9 / 2.0, r_core)
+            if lead_rho_ohm_m is not None and r_lead > 0:
+                ga += math.pi * r_lead * r_lead / lead_rho_ohm_m
+            ga += math.pi * (r_core * r_core - r_lead * r_lead) \
+                / solder_rho_ohm_m
+        return (length_nm * 1e-9) / ga
 
 
 @dataclass
@@ -147,6 +197,23 @@ class Problem:
     vias_capped: bool = True                  # filled+capped vias: thin cap
     cap_plating_nm: int = 15_000              # over outer-layer mouths;
                                               # False = open mouths
+    cap_max_drill_nm: int = 500_000           # fab caps only small vias:
+                                              # drills above this stay open
+                                              # even with vias_capped
+    tht_protrusion_nm: int = 1_500_000        # clipped THT lead protrusion:
+                                              # a solder cone of this height
+                                              # at the drill wall (tapering
+                                              # to zero at the pad edge)
+                                              # wraps the lead on each solder
+                                              # contact's protrusion_side;
+                                              # 0 disables the cones
+    tht_lead_clearance_nm: int = 250_000      # hole minus lead diameter (fab
+                                              # rule): the lead cylinder of
+                                              # drill - this conducts inside
+                                              # every solder-filled hole
+    tht_lead_rho_ohm_m: float = 1.68e-8       # lead material resistivity
+                                              # (copper; brass ~6.4e-8,
+                                              # copper-clad steel higher)
 
     @property
     def layer_names(self) -> list[str]:
@@ -173,6 +240,66 @@ class Problem:
         return int(x.min()), int(y.min()), int(x.max()), int(y.max())
 
 
+def contact_solder_buildups(problem: Problem) -> list[str]:
+    """Soldered THT-joint contacts: the pad face on the SOLDER side (the
+    protrusion side, opposite the component - the component-side face
+    stays bare) is covered in solder of average thickness
+    solder_thickness_nm. Adds one SurfaceBuildup there for every
+    `solder` electrode's pad shape (the buildup machinery intersects
+    with actual copper at raster time). Returns the affected layer
+    names. Called once when the problem is built."""
+    included = {l.layer_name for l in problem.layers}
+    touched = []
+    for e in problem.electrodes1 + problem.electrodes2:
+        if not e.solder or not e.polygons \
+                or e.protrusion_side not in included:
+            continue
+        problem.buildups.append(
+            SurfaceBuildup(layer_name=e.protrusion_side,
+                           polygons=list(e.polygons)))
+        touched.append(e.protrusion_side)
+    return sorted(set(touched))
+
+
+def _disc_polygon(x_nm: float, y_nm: float, r_nm: float,
+                  n: int = 32) -> Polygon:
+    th = np.linspace(0.0, 2.0 * math.pi, n, endpoint=False)
+    return Polygon(outline=np.round(np.stack(
+        [x_nm + r_nm * np.cos(th), y_nm + r_nm * np.sin(th)],
+        axis=1)).astype(np.int64))
+
+
+def tht_joint_buildups(problem: Problem,
+                       shapes: dict | None = None) -> list[str]:
+    """Solder coat of the net's populated STITCHING through-hole pads
+    (ViaLink kind 'pad' with solder_filled), on the pad's SOLDER side
+    (the protrusion side, opposite the component; the component-side
+    face stays bare). `shapes` maps (x, y) to the exact pad polygons
+    (fetched from KiCad); pads without one fall back to a pad-diameter
+    disc. Contact pads are skipped: contact_solder_buildups already
+    coats them with the exact pad shape. Returns the affected layer
+    names."""
+    included = {l.layer_name for l in problem.layers}
+    contacts = {e.center for e in problem.electrodes1 + problem.electrodes2
+                if e.drill_nm > 0 and e.center is not None}
+    touched = []
+    for v in problem.vias:
+        if v.kind != "pad" or not v.solder_filled \
+                or (v.x, v.y) in contacts \
+                or v.protrusion_side not in included:
+            continue
+        polys = (shapes or {}).get((v.x, v.y))
+        if polys is None:
+            if v.pad_nm <= v.drill_nm:
+                continue
+            polys = [_disc_polygon(v.x, v.y, v.pad_nm / 2.0)]
+        problem.buildups.append(
+            SurfaceBuildup(layer_name=v.protrusion_side,
+                           polygons=list(polys)))
+        touched.append(v.protrusion_side)
+    return sorted(set(touched))
+
+
 def _arc_params(start, mid, end) -> tuple[float, float, float, float, float] | None:
     """Circle through three points: (cx, cy, r, a0, sweep) with a0 the
     start angle and sweep signed; None if the points are collinear."""
@@ -321,6 +448,13 @@ def _electrode_to_json(e: Electrode) -> dict:
         "label": e.label,
         "polygons": (None if e.polygons is None
                      else [_poly_to_json(poly) for poly in e.polygons]),
+        "drill_nm": e.drill_nm,
+        "pad_nm": e.pad_nm,
+        "pad_min_nm": e.pad_min_nm,
+        "center": (None if e.center is None else list(e.center)),
+        "barrel_z": (None if e.barrel_z is None else list(e.barrel_z)),
+        "solder": e.solder,
+        "protrusion_side": e.protrusion_side,
     }
 
 
@@ -331,6 +465,15 @@ def _electrode_from_json(d: dict) -> Electrode:
         label=d.get("label", "rect"),
         polygons=(None if d.get("polygons") is None
                   else [_poly_from_json(pd) for pd in d["polygons"]]),
+        drill_nm=int(d.get("drill_nm", 0)),
+        pad_nm=int(d.get("pad_nm", 0)),
+        pad_min_nm=int(d.get("pad_min_nm", 0)),
+        center=(None if d.get("center") is None
+                else (int(d["center"][0]), int(d["center"][1]))),
+        barrel_z=(None if d.get("barrel_z") is None
+                  else (int(d["barrel_z"][0]), int(d["barrel_z"][1]))),
+        solder=bool(d.get("solder", False)),
+        protrusion_side=d.get("protrusion_side"),
     )
 
 
@@ -369,6 +512,10 @@ def problem_to_json(p: Problem) -> dict:
         "extra_cu_nm": p.extra_cu_nm,
         "vias_capped": p.vias_capped,
         "cap_plating_nm": p.cap_plating_nm,
+        "cap_max_drill_nm": p.cap_max_drill_nm,
+        "tht_protrusion_nm": p.tht_protrusion_nm,
+        "tht_lead_clearance_nm": p.tht_lead_clearance_nm,
+        "tht_lead_rho_ohm_m": p.tht_lead_rho_ohm_m,
     }
 
 
@@ -415,7 +562,12 @@ def problem_from_json(d: dict) -> Problem:
             ViaLink(x=int(vd["x"]), y=int(vd["y"]), drill_nm=int(vd["drill_nm"]),
                     z_top_nm=int(vd["z_top_nm"]), z_bot_nm=int(vd["z_bot_nm"]),
                     kind=vd.get("kind", "via"),
-                    pad_nm=int(vd.get("pad_nm", 0)))
+                    pad_nm=int(vd.get("pad_nm", 0)),
+                    pad_min_nm=int(vd.get("pad_min_nm", 0)),
+                    # older dumps: every THT pad counted as solder-filled
+                    solder_filled=bool(vd.get(
+                        "solder_filled", vd.get("kind", "via") == "pad")),
+                    protrusion_side=vd.get("protrusion_side"))
             for vd in d["vias"]
         ],
         electrodes1=(
@@ -442,6 +594,10 @@ def problem_from_json(d: dict) -> Problem:
         ],
         vias_capped=bool(d.get("vias_capped", True)),
         cap_plating_nm=int(d.get("cap_plating_nm", 15_000)),
+        cap_max_drill_nm=int(d.get("cap_max_drill_nm", 500_000)),
+        tht_protrusion_nm=int(d.get("tht_protrusion_nm", 1_500_000)),
+        tht_lead_clearance_nm=int(d.get("tht_lead_clearance_nm", 250_000)),
+        tht_lead_rho_ohm_m=float(d.get("tht_lead_rho_ohm_m", 1.68e-8)),
     )
 
 

fill_resistance/main.py

@@ -33,7 +33,7 @@ def main() -> None:
         try:
             kicad, board = board_io.connect()
             stackup = board_io.get_stackup_info(board)
-            es1, es2, net_hint = board_io.get_electrodes(board)
+            es1, es2, net_hint = board_io.get_electrodes(board, stackup)
             if board_io.any_zone_unfilled(board) or config.ALWAYS_REFILL:
                 board_io.refill(board)
             fills = board_io.gather_net_fills(board)
@@ -95,7 +95,8 @@ def main() -> None:
                 buildups=(buildups if selection.include_buildup else None),
                 extra_cu_um=selection.extra_cu_um,
                 tracks=(tracks if selection.include_tracks else None),
-                vias_capped=selection.vias_capped)
+                vias_capped=selection.vias_capped,
+                cap_max_drill_mm=selection.cap_max_drill_mm)
             outdir = report.make_output_dir(board_io.board_dir(board))
         except ApiError as e:
             raise UserFacingError(f"KiCad API error: {e}")

fill_resistance/raster.py

@@ -232,9 +232,76 @@ def rasterize_stack(problem: Problem, h_nm: float) -> RasterStack:
                     _paint_ring(stack, hole, False, pmask)
                 stack.buildup[li] |= pmask
         stack.buildup &= stack.masks        # solder wets exposed copper only
+
+    _paint_lead_fillets(stack, problem)
     return stack
 
 
+def _paint_lead_fillets(stack: RasterStack, problem: Problem) -> None:
+    """Protruding THT leads (barrel contacts AND the net's populated
+    stitching through-hole pads): the clipped lead sticks
+    tht_protrusion_nm out of the hole on the side opposite the
+    component, wrapped by a solder cone - full protrusion height at
+    the drill wall, tapering linearly to zero at the pad edge. Modeled
+    as extra conduction-equivalent copper via stack.thick_scale: the
+    tall solder column next to the wall pulls those cells to lead
+    potential (equivalent to extending the barrel wall vertically), the
+    taper carries the radial spreading. At f > 0 the factor multiplies
+    the skin-corrected sheet conductance, like the via mouths
+    (approximation)."""
+    H = problem.tht_protrusion_nm
+    if H <= 0:
+        return
+    ny, nx = stack.shape2d
+    h = stack.h_nm
+    index = {name: li for li, name in enumerate(stack.layer_names)}
+
+    # one cone per joint: contact electrodes first (exact data), then the
+    # net's populated stitching THT pads, skipping the contacts' barrels
+    jobs = []
+    seen = set()
+    for e in problem.electrodes1 + problem.electrodes2:
+        if e.drill_nm <= 0:
+            continue
+        if e.center is not None:
+            x, y = e.center
+        else:
+            x = (e.rect.x0 + e.rect.x1) / 2.0
+            y = (e.rect.y0 + e.rect.y1) / 2.0
+        seen.add((int(x), int(y)))
+        if e.solder and e.protrusion_side:
+            # oblong pads: taper to the inscribed circle (conservative)
+            jobs.append((x, y, e.drill_nm, e.pad_min_nm or e.pad_nm,
+                         e.protrusion_side))
+    for v in problem.vias:
+        if v.kind == "pad" and v.solder_filled and v.protrusion_side \
+                and (v.x, v.y) not in seen:
+            jobs.append((v.x, v.y, v.drill_nm, v.pad_min_nm or v.pad_nm,
+                         v.protrusion_side))
+
+    for x, y, drill_nm, pad_nm, side in jobs:
+        li = index.get(side)
+        if li is None or pad_nm <= drill_nm:
+            continue
+        ra, rb = drill_nm / 2.0, pad_nm / 2.0
+        j0 = max(0, math.floor((x - rb - stack.x0_nm) / h))
+        j1 = min(nx, math.floor((x + rb - stack.x0_nm) / h) + 1)
+        i0 = max(0, math.floor((y - rb - stack.y0_nm) / h))
+        i1 = min(ny, math.floor((y + rb - stack.y0_nm) / h) + 1)
+        if i0 >= i1 or j0 >= j1:
+            continue
+        xs = stack.x0_nm + (np.arange(j0, j1) + 0.5) * h - x
+        ys = stack.y0_nm + (np.arange(i0, i1) + 0.5) * h - y
+        r = np.sqrt(ys[:, None] ** 2 + xs[None, :] ** 2)
+        t_sn = H * np.clip((rb - r) / (rb - ra), 0.0, 1.0)
+        t_eq = t_sn * (problem.rho_ohm_m / problem.solder_rho_ohm_m)
+        factor = 1.0 + t_eq / problem.layers[li].thickness_nm
+        if stack.thick_scale is None:
+            stack.thick_scale = np.ones(stack.masks.shape)
+        m = stack.masks[li, i0:i1, j0:j1]
+        stack.thick_scale[li, i0:i1, j0:j1] *= np.where(m, factor, 1.0)
+
+
 def _via_span(problem: Problem, via) -> list[int]:
     return [li for li, layer in enumerate(problem.layers)
             if via.spans(layer.z_nm)]
@@ -268,15 +335,22 @@ def _apply_via_mouths(stack: RasterStack, problem: Problem) -> None:
     """Drill-mouth treatment, area-weighted per cell (4x4 supersampling):
     capped vias carry a cap_plating-thin copper cap over the mouth on the
     OUTER layers, uncapped vias (and inner layers either way) get an open
-    hole. Fully swallowed cells leave the mask; partially covered cells
-    keep a thickness-scaled sheet conductance via stack.thick_scale."""
+    hole. The fab caps only small vias: drills above cap_max_drill_nm
+    stay open even with vias_capped. THT pad mouths: populated pads are
+    solder-filled - the mouth copper stays and stands in for the plug
+    (conservative: the plug's solder is worth far more than the foil);
+    DNP pad holes are cut open on every layer. Fully swallowed cells
+    leave the mask; partially covered cells keep a thickness-scaled
+    sheet conductance via stack.thick_scale."""
     ny, nx = stack.shape2d
     h = stack.h_nm
     outer = {li for li, n in enumerate(stack.layer_names)
              if n in ("F.Cu", "B.Cu")}
     sub = (np.arange(4) + 0.5) / 4.0
     for via in problem.vias:
-        if via.kind != "via" or via.drill_nm <= 0:
+        if via.drill_nm <= 0:
+            continue
+        if via.kind == "pad" and via.solder_filled:
             continue
         r = via.drill_nm / 2.0
         j0 = max(0, math.floor((via.x - r - stack.x0_nm) / h))
@@ -296,11 +370,12 @@ def _apply_via_mouths(stack: RasterStack, problem: Problem) -> None:
         if stack.thick_scale is None:
             stack.thick_scale = np.ones(stack.masks.shape)
         for li in _via_span(problem, via):
-            if problem.vias_capped and li in outer:
+            if via.kind == "via" and problem.vias_capped and li in outer \
+                    and via.drill_nm <= problem.cap_max_drill_nm:
                 ratio = min(problem.cap_plating_nm
                             / problem.layers[li].thickness_nm, 1.0)
             else:
-                ratio = 0.0
+                ratio = 0.0                 # open hole (also DNP THT holes)
             s = 1.0 - cov * (1.0 - ratio)
             gone = s <= 1e-9
             stack.masks[li, i0:i1, j0:j1] &= ~gone
@@ -399,26 +474,88 @@ def _electrode_cells2d(stack: RasterStack, e: Electrode) -> np.ndarray:
     return _rect_cells(stack, e.rect)
 
 
+def _barrel_ring2d(stack: RasterStack, e: Electrode,
+                   mask2d: np.ndarray) -> np.ndarray:
+    """Contact cells of a barrel electrode on one layer: the copper ring
+    at the drill wall (cell centers within one cell of radius drill/2),
+    where the lead/wire soldered into the hole actually meets the layer.
+    If rasterization or an antipad leaves no copper there, fall back to
+    the nearest copper ring within the pad footprint (+1 cell of slop) -
+    the same search bound as the solver's barrel attachment."""
+    ny, nx = stack.shape2d
+    h = stack.h_nm
+    if e.center is not None:
+        x, y = e.center
+    else:
+        x = (e.rect.x0 + e.rect.x1) / 2.0
+        y = (e.rect.y0 + e.rect.y1) / 2.0
+    r = e.drill_nm / 2.0
+    rw = max(e.pad_nm, e.drill_nm + 300_000) / 2.0 + h
+    out = np.zeros((ny, nx), dtype=bool)
+    j0 = max(0, math.floor((x - rw - stack.x0_nm) / h))
+    j1 = min(nx, math.floor((x + rw - stack.x0_nm) / h) + 1)
+    i0 = max(0, math.floor((y - rw - stack.y0_nm) / h))
+    i1 = min(ny, math.floor((y + rw - stack.y0_nm) / h) + 1)
+    if i0 >= i1 or j0 >= j1:
+        return out
+    xs = stack.x0_nm + (np.arange(j0, j1) + 0.5) * h - x
+    ys = stack.y0_nm + (np.arange(i0, i1) + 0.5) * h - y
+    d = np.sqrt(ys[:, None] ** 2 + xs[None, :] ** 2)
+    m = mask2d[i0:i1, j0:j1]
+    ring = m & (np.abs(d - r) <= h)
+    if not ring.any():
+        dc = np.where(m & (d <= rw), d, np.inf)
+        dmin = dc.min()
+        if np.isfinite(dmin):
+            ring = dc <= dmin + h              # e.g. thermal-spoke tips
+    out[i0:i1, j0:j1] = ring
+    return out
+
+
+def _part_mask3d(stack: RasterStack, problem: Problem,
+                 el: Electrode) -> np.ndarray:
+    """(L, ny, nx) contact cells of one electrode part: the barrel-wall
+    ring on every spanned layer for via/THT-pad contacts, else the
+    part's shape ∩ copper on its contact layer(s)."""
+    part = np.zeros_like(stack.masks)
+    if el.drill_nm > 0:
+        for li, name in enumerate(stack.layer_names):
+            if el.contact not in ("all", name):
+                continue
+            if el.barrel_z is not None:
+                z = problem.layers[li].z_nm
+                if not (el.barrel_z[0] - 1 <= z <= el.barrel_z[1] + 1):
+                    continue
+            part[li] = _barrel_ring2d(stack, el, stack.masks[li])
+        return part
+    cells2d = _electrode_cells2d(stack, el)
+    for li, name in enumerate(stack.layer_names):
+        if el.contact in ("all", name):
+            part[li] = cells2d & stack.masks[li]
+    return part
+
+
 def electrode_masks(stack: RasterStack, problem: Problem
                     ) -> tuple[np.ndarray, np.ndarray]:
     """Terminal mask = OR over its parts; part = shape ∩ copper on the
-    part's contact layer(s). contact 'all' = every included layer (bolted
-    lug / through pad); a layer name = that layer only. Every part must
-    individually land on copper (clear feedback). V+/V- must not overlap;
-    touching is checked later, only for the equipotential contact model."""
+    part's contact layer(s), or the barrel-wall ring for via/THT-pad
+    contacts (current enters through the soldered barrel, not the pad
+    face). contact 'all' = every included layer (bolted lug / through
+    pad); a layer name = that layer only. Every part must individually
+    land on copper (clear feedback). V+/V- must not overlap; touching is
+    checked later, only for the equipotential contact model."""
     def build(parts: list[Electrode], which: str) -> np.ndarray:
         e = np.zeros_like(stack.masks)
         for el in parts:
-            cells2d = _electrode_cells2d(stack, el)
-            part = np.zeros_like(stack.masks)
-            for li, name in enumerate(stack.layer_names):
-                if el.contact == "all" or el.contact == name:
-                    part[li] = cells2d & stack.masks[li]
+            part = _part_mask3d(stack, problem, el)
             if not part.any():
+                where = ("near its barrel (drill-wall ring / pad footprint)"
+                         if el.drill_nm > 0 else
+                         "(or is smaller than one grid cell)")
                 raise ElectrodeError(
                     f"A {which} contact part ({el.label}) does not overlap "
                     f"any copper of the selected fill on contact layer(s) "
-                    f"'{el.contact}' (or is smaller than one grid cell)."
+                    f"'{el.contact}' {where}."
                 )
             e |= part
         if not e.any():
@@ -446,11 +583,7 @@ def electrode_partition(stack: RasterStack, problem: Problem
         out = []
         claimed = np.zeros_like(stack.masks)
         for el in parts:
-            cells2d = _electrode_cells2d(stack, el)
-            m = np.zeros_like(stack.masks)
-            for li, name in enumerate(stack.layer_names):
-                if el.contact == "all" or el.contact == name:
-                    m[li] = cells2d & stack.masks[li]
+            m = _part_mask3d(stack, problem, el)
             m &= ~claimed
             claimed |= m
             out.append((el.label, m))

fill_resistance/solver.py

@@ -178,8 +178,16 @@ def _barrel_links(stack: RasterStack, problem: Problem
             length = problem.layers[lb].z_nm - problem.layers[la].z_nm
             if length <= 0:
                 continue
-            r_dc = via.barrel_resistance(length, problem.rho_ohm_m,
-                                         problem.plating_nm)
+            # populated THT pads carry a soldered component lead: lead
+            # cylinder (drill minus the fab clearance) + solder annulus
+            # in parallel with the plating (DNP pads and vias stay
+            # plating-only)
+            r_dc = via.barrel_resistance(
+                length, problem.rho_ohm_m, problem.plating_nm,
+                solder_rho_ohm_m=(problem.solder_rho_ohm_m
+                                  if via.solder_filled else None),
+                lead_nm=max(via.drill_nm - problem.tht_lead_clearance_nm, 0),
+                lead_rho_ohm_m=problem.tht_lead_rho_ohm_m)
             links.append((vi, la, ia, ja, lb, ib, jb, r_dc))
     return links, dead
 

fill_resistance/standalone.py

@@ -42,6 +42,10 @@ def main(argv=None) -> int:
     ap.add_argument("--uncapped", action="store_true",
                     help="treat vias as uncapped (open drill mouths on "
                          "all layers)")
+    ap.add_argument("--cap-max-drill", type=float, default=None,
+                    metavar="MM",
+                    help="cap only vias with drill <= this [mm]; larger "
+                         "drills stay open (default: from the dump)")
     ap.add_argument("--extra-cu-um", type=float, default=None,
                     help="override the added copper in mask openings [um]")
     ap.add_argument("--force-iterative", action="store_true",
@@ -68,6 +72,8 @@ def main(argv=None) -> int:
         problem.buildups = []
     if args.uncapped:
         problem.vias_capped = False
+    if args.cap_max_drill is not None:
+        problem.cap_max_drill_nm = int(args.cap_max_drill * 1e6)
     if args.extra_cu_um is not None:
         problem.extra_cu_nm = int(args.extra_cu_um * 1000)
     if args.layers:

metadata.json

@@ -2,7 +2,7 @@
     "$schema": "https://go.kicad.org/pcm/schemas/v2",
     "name": "Fill Resistance",
     "description": "DC/AC resistance of copper zone fills and traces between two contacts, single- or multi-layer with via coupling; current and power density maps.",
-    "description_full": "Computes the DC or AC resistance of copper zone fills and traces between two contacts (marker rectangles on User.1/User.2 and/or selected pads), single- or multi-layer: the chosen net's fills and tracks are solved as coupled finite-difference sheets linked by the net's via and through-hole-pad barrels; traces narrower than the grid become exact 1D resistor chains, and an adaptive multi-resolution grid (fine at features, coarse plane interiors, deferred-corrected) keeps large boards fast.\n\nShows per-layer rasterized maps, potential, current density and power density, reports per-via currents (via ampacity) and total dissipation at a selectable test current. At a user-set frequency the exact 1D foil/barrel skin-effect correction is applied (AC results are a rigorous lower bound). PNGs, a text summary and a re-solvable geometry dump are saved per run.\n\nNote: the first load builds the plugin's Python environment (numpy, scipy, pyamg, matplotlib, PySide6) and can take several minutes.",
+    "description_full": "Computes the DC or AC resistance of copper zone fills and traces between two contacts (marker rectangles on User.1/User.2 and/or selected pads/vias), single- or multi-layer: the chosen net's fills and tracks are solved as coupled finite-difference sheets linked by the net's via and through-hole-pad barrels. Selected vias/THT pads inject at the drill-wall barrel, and every populated THT hole carries its full solder joint (component lead, solder fill, one-sided pad coat and protruding-lead cone) with exact pad shapes and do-not-populate flags read from KiCad; traces narrower than the grid become exact 1D resistor chains, and an adaptive multi-resolution grid (fine at features, coarse plane interiors, deferred-corrected) keeps large boards fast.\n\nShows per-layer rasterized maps, potential, current density and power density, reports per-via currents (via ampacity) and total dissipation at a selectable test current. At a user-set frequency the exact 1D foil/barrel skin-effect correction is applied (AC results are a rigorous lower bound). PNGs, a text summary and a re-solvable geometry dump are saved per run.\n\nNote: the first load builds the plugin's Python environment (numpy, scipy, pyamg, matplotlib, PySide6) and can take several minutes.",
     "identifier": "th.co.b4l.fill-resistance",
     "type": "plugin",
     "author": {
@@ -17,7 +17,7 @@
     },
     "versions": [
         {
-            "version": "1.0.1",
+            "version": "1.1.0",
             "status": "stable",
             "kicad_version": "10.0",
             "runtime": "ipc"

tests/test_barrel_contacts.py

@@ -0,0 +1,338 @@
+"""Barrel (via / through-hole pad) contact tests: current enters at the
+drill-wall ring, not the pad face, and soldered THT joints carry a
+solder-filled hole plus an average-thickness solder coat on the pad."""
+import math
+
+import numpy as np
+import pytest
+
+from fill_resistance import raster, solver
+from fill_resistance.geometry import (Electrode, Polygon, ViaLink,
+                                      contact_solder_buildups, load_problem,
+                                      problem_from_json, problem_to_json,
+                                      save_problem, tht_joint_buildups)
+from tests.util import NM, make_problem, rect_mm, ring_mm
+
+PLATE20 = [(0, 0), (20, 0), (20, 20), (0, 20)]
+
+
+def _barrel(x_mm, y_mm, drill_mm, pad_mm=0.0, solder=False, polygons=None):
+    r = max(pad_mm, drill_mm) / 2
+    return Electrode(
+        rect=rect_mm((x_mm - r, y_mm - r, x_mm + r, y_mm + r)),
+        contact="all", label=f"via({x_mm},{y_mm})",
+        drill_nm=int(drill_mm * NM), pad_nm=int(pad_mm * NM),
+        center=(int(x_mm * NM), int(y_mm * NM)), solder=solder,
+        polygons=polygons)
+
+
+def _disc(x_mm, y_mm, r_mm, n=64) -> Polygon:
+    ang = np.linspace(0, 2 * np.pi, n, endpoint=False)
+    return Polygon(outline=ring_mm(
+        [(x_mm + r_mm * np.cos(a), y_mm + r_mm * np.sin(a)) for a in ang]))
+
+
+def _solve(p, h_mm, model="equipotential"):
+    stack = raster.rasterize_stack(p, h_mm * NM)
+    e1, e2 = raster.electrode_masks(stack, p)
+    return solver.run_solve(p, stack, e1, e2, 1.0, contact_model=model), stack
+
+
+def test_ring_cells_at_drill_wall():
+    """The contact cells of a barrel electrode form a ring at the drill
+    wall (one-cell tolerance), not the pad face."""
+    p = make_problem([(PLATE20, [])],
+                     rect1_mm=(0, 0, 1, 20), rect2_mm=(19, 0, 20, 20))
+    p.electrodes1 = [_barrel(10, 10, drill_mm=1.0, pad_mm=1.6)]
+    stack = raster.rasterize_stack(p, 0.1 * NM)
+    e1, _ = raster.electrode_masks(stack, p)
+    ii, jj = np.nonzero(e1[0])
+    xs = stack.x0_nm + (jj + 0.5) * stack.h_nm - 10 * NM
+    ys = stack.y0_nm + (ii + 0.5) * stack.h_nm - 10 * NM
+    d = np.hypot(xs, ys)
+    assert len(ii) >= 8
+    assert (np.abs(d - 0.5 * NM) <= stack.h_nm + 1).all()
+    # far fewer cells than the full 1.6 mm pad disc
+    assert len(ii) < 0.5 * math.pi * (0.8 * NM / stack.h_nm) ** 2
+
+
+def test_two_barrel_contacts_match_acosh():
+    """Two equipotential circular contacts of radius a, centers d apart,
+    on a large sheet: R = rho/(pi t) * acosh(d / 2a). The barrel-ring
+    contact must reproduce the analytic spreading resistance."""
+    t_um, rho = 70.0, 1.68e-8
+    plate = [(0, 0), (80, 0), (80, 60), (0, 60)]
+    p = make_problem([(plate, [])], rect1_mm=(0, 0, 1, 1),
+                     rect2_mm=(79, 59, 80, 60), t_um=t_um, rho=rho)
+    p.electrodes1 = [_barrel(30, 30, drill_mm=2.0)]
+    p.electrodes2 = [_barrel(50, 30, drill_mm=2.0)]
+    res, _ = _solve(p, 0.15)
+    r_ref = rho / (math.pi * t_um * 1e-6) * math.acosh(20e-3 / (2 * 1e-3))
+    assert res.R_ohm == pytest.approx(r_ref, rel=0.08)
+
+
+def test_barrel_includes_pad_spreading_resistance():
+    """Injecting at the barrel wall (0.5 mm ring) sees the spreading
+    resistance the whole-pad-face contact (2.4 mm equipotential disc)
+    short-circuits: R_barrel > R_pad_face."""
+    p1 = make_problem([(PLATE20, [])],
+                      rect1_mm=(0, 0, 1, 20), rect2_mm=(19, 0, 20, 20))
+    p1.electrodes1 = [_barrel(10, 10, drill_mm=1.0, pad_mm=2.4)]
+    r_barrel, _ = _solve(p1, 0.1)
+
+    p2 = make_problem([(PLATE20, [])],
+                      rect1_mm=(0, 0, 1, 20), rect2_mm=(19, 0, 20, 20))
+    p2.electrodes1 = [Electrode(rect=rect_mm((8.8, 8.8, 11.2, 11.2)),
+                                contact="all", label="pad face",
+                                polygons=[_disc(10, 10, 1.2)])]
+    r_face, _ = _solve(p2, 0.1)
+    assert r_barrel.R_ohm > r_face.R_ohm * 1.05
+
+
+def test_ring_fallback_nearest_copper():
+    """Antipad bigger than the drill: no copper at the wall ring, the
+    contact falls back to the nearest copper ring inside the pad
+    footprint (e.g. thermal-spoke tips / hole edge)."""
+    hole = [(10 + 1.2 * np.cos(a), 10 + 1.2 * np.sin(a))
+            for a in np.linspace(0, 2 * np.pi, 64, endpoint=False)]
+    p = make_problem([(PLATE20, [hole])],
+                     rect1_mm=(0, 0, 1, 20), rect2_mm=(19, 0, 20, 20))
+    p.electrodes1 = [_barrel(10, 10, drill_mm=0.6, pad_mm=4.0)]
+    res, stack = _solve(p, 0.1)
+    e1, _ = raster.electrode_masks(stack, p)
+    ii, jj = np.nonzero(e1[0])
+    d = np.hypot(stack.x0_nm + (jj + 0.5) * stack.h_nm - 10 * NM,
+                 stack.y0_nm + (ii + 0.5) * stack.h_nm - 10 * NM)
+    assert len(ii) >= 8
+    assert (d >= 1.2 * NM - stack.h_nm).all()
+    assert (d <= 1.2 * NM + 2.5 * stack.h_nm).all()
+    assert np.isfinite(res.R_ohm) and res.R_ohm > 0
+
+
+def test_solder_filled_barrel_resistance():
+    """THT joints: the solder core conducts in parallel with the plating.
+    Exact parallel-area formula, and a sanity ratio for a 1 mm drill."""
+    v = ViaLink(x=0, y=0, drill_nm=1_000_000, z_top_nm=-1, z_bot_nm=1)
+    rho, sn = 1.68e-8, 1.32e-7
+    r_plain = v.barrel_resistance(1_600_000, rho, 18_000)
+    r_fill = v.barrel_resistance(1_600_000, rho, 18_000,
+                                 solder_rho_ohm_m=sn)
+    ga = math.pi * 1e-3 * 18e-6 / rho
+    ga += math.pi * (0.5e-3 - 18e-6) ** 2 / sn
+    assert r_fill == pytest.approx(1.6e-3 / ga, rel=1e-12)
+    assert 1.5 < r_plain / r_fill < 4.0
+
+
+def test_contact_solder_coat():
+    """A soldered THT contact adds an average-thickness solder buildup
+    over the pad face on its SOLDER side only (opposite the component),
+    lowering the spreading resistance vs the bare barrel contact."""
+    def prob():
+        p = make_problem([(PLATE20, [])],
+                         rect1_mm=(0, 0, 1, 20), rect2_mm=(19, 0, 20, 20))
+        p.electrodes1 = [_barrel(10, 10, drill_mm=1.0, pad_mm=2.4,
+                                 solder=True, polygons=[_disc(10, 10, 1.2)])]
+        p.electrodes1[0].protrusion_side = "F.Cu"
+        return p
+
+    # solder side not among the included layers -> no coat there
+    q = prob()
+    q.electrodes1[0].protrusion_side = "B.Cu"
+    assert contact_solder_buildups(q) == []
+
+    p = prob()
+    assert contact_solder_buildups(p) == ["F.Cu"]
+    assert len(p.buildups) == 1 and p.buildups[0].layer_name == "F.Cu"
+    r_coat, stack = _solve(p, 0.1)
+    assert stack.buildup is not None and stack.buildup.any()
+
+    r_bare, _ = _solve(prob(), 0.1)          # helper not called: no coat
+    assert r_coat.R_ohm < r_bare.R_ohm
+
+
+def test_lead_fillet_profile():
+    """The protruding-lead solder cone paints thick_scale with the exact
+    per-cell formula: 1 + H*clip((rb-r)/(rb-ra), 0, 1)*(rho_cu/rho_sn)/t
+    on copper of the protrusion side; nothing elsewhere."""
+    p = make_problem([(PLATE20, [])],
+                     rect1_mm=(0, 0, 1, 20), rect2_mm=(19, 0, 20, 20))
+    p.electrodes1 = [_barrel(10, 10, drill_mm=1.0, pad_mm=2.4, solder=True)]
+    p.electrodes1[0].protrusion_side = "F.Cu"
+    stack = raster.rasterize_stack(p, 0.1 * NM)
+    assert stack.thick_scale is not None
+    ny, nx = stack.shape2d
+    jj, ii = np.meshgrid(np.arange(nx), np.arange(ny))
+    r = np.hypot(stack.x0_nm + (jj + 0.5) * stack.h_nm - 10 * NM,
+                 stack.y0_nm + (ii + 0.5) * stack.h_nm - 10 * NM)
+    ra, rb, H = 0.5 * NM, 1.2 * NM, p.tht_protrusion_nm
+    t_eq = H * np.clip((rb - r) / (rb - ra), 0, 1) \
+        * (p.rho_ohm_m / p.solder_rho_ohm_m)
+    expect = np.where(stack.masks[0],
+                      1.0 + t_eq / p.layers[0].thickness_nm, 1.0)
+    assert np.allclose(stack.thick_scale[0], expect, rtol=1e-12)
+    # 1.5 mm of solder at the wall ~ 191 um copper: factor ~ 3.7 on 70 um
+    assert stack.thick_scale[0].max() > 3.0
+
+    p.electrodes1[0].protrusion_side = None    # e.g. via contact: no cone
+    s2 = raster.rasterize_stack(p, 0.1 * NM)
+    assert s2.thick_scale is None
+
+
+def test_lead_fillet_lowers_resistance(monkeypatch):
+    """The cone shorts the joint vicinity: R(with cone) < R(coat-less
+    bare barrel); the adaptive grid pins the cone cells fine and
+    matches the uniform grid."""
+    def prob(protrude=True):
+        p = make_problem([(PLATE20, [])],
+                         rect1_mm=(0, 0, 1, 20), rect2_mm=(19, 0, 20, 20))
+        p.electrodes1 = [_barrel(10, 10, drill_mm=1.0, pad_mm=2.4,
+                                 solder=True)]
+        p.electrodes1[0].protrusion_side = "F.Cu"
+        if not protrude:
+            p.tht_protrusion_nm = 0
+        return p
+
+    r_cone, _ = _solve(prob(), 0.1)
+    r_bare, _ = _solve(prob(protrude=False), 0.1)
+    assert r_cone.R_ohm < r_bare.R_ohm
+
+    from fill_resistance import config
+    monkeypatch.setattr(config, "ADAPTIVE_CELLS", True)
+    r_ada, _ = _solve(prob(), 0.1)
+    assert r_ada.R_ohm == pytest.approx(r_cone.R_ohm, rel=2e-3)
+
+
+def _pad_link(populated=True):
+    return ViaLink(x=10 * NM, y=10 * NM, drill_nm=1_000_000, z_top_nm=-1,
+                   z_bot_nm=1, kind="pad", pad_nm=2_400_000,
+                   solder_filled=populated,
+                   protrusion_side="F.Cu" if populated else None)
+
+
+def test_stitching_pad_joint():
+    """A populated THT pad on the net (not a contact) gets the full
+    joint: solder-side coat, cone, and a conducting (plugged) mouth;
+    a DNP pad gets an open hole and nothing else."""
+    def prob(populated=True):
+        p = make_problem([(PLATE20, [])],
+                         rect1_mm=(0, 0, 1, 20), rect2_mm=(19, 0, 20, 20))
+        p.vias = [_pad_link(populated)]
+        return p
+
+    p = prob()
+    assert tht_joint_buildups(p) == ["F.Cu"]
+    assert len(p.buildups) == 1
+    r_joint, stack = _solve(p, 0.1)
+    assert stack.thick_scale is not None and stack.thick_scale.max() > 3.0
+    assert stack.buildup is not None and stack.buildup.any()
+    assert stack.masks[0][stack.cell_of(10 * NM, 10 * NM)]   # plugged mouth
+
+    q = prob(populated=False)
+    assert tht_joint_buildups(q) == []
+    r_bare, s2 = _solve(q, 0.1)
+    assert s2.buildup is None
+    assert not s2.masks[0][s2.cell_of(10 * NM, 10 * NM)]     # DNP: open hole
+    assert r_joint.R_ohm < r_bare.R_ohm
+
+
+def test_cone_not_doubled_at_contact():
+    """A contact THT pad also appears in the net's pad list (ViaLink):
+    the cone and coat must be applied once, not squared/stacked."""
+    p = make_problem([(PLATE20, [])],
+                     rect1_mm=(0, 0, 1, 20), rect2_mm=(19, 0, 20, 20))
+    p.electrodes1 = [_barrel(10, 10, drill_mm=1.0, pad_mm=2.4, solder=True,
+                             polygons=[_disc(10, 10, 1.2)])]
+    p.electrodes1[0].protrusion_side = "F.Cu"
+    p.vias = [_pad_link()]
+    assert contact_solder_buildups(p) == ["F.Cu"]
+    assert tht_joint_buildups(p) == []       # contact center is skipped
+    stack = raster.rasterize_stack(p, 0.1 * NM)
+    wall = 1.0 + p.tht_protrusion_nm \
+        * (p.rho_ohm_m / p.solder_rho_ohm_m) / p.layers[0].thickness_nm
+    assert stack.thick_scale.max() == pytest.approx(wall, rel=1e-12)
+
+
+def test_lead_in_barrel_resistance():
+    """Populated hole: plating || lead cylinder || solder annulus, with
+    the lead clipped to the plating bore."""
+    v = ViaLink(x=0, y=0, drill_nm=1_000_000, z_top_nm=-1, z_bot_nm=1)
+    rho, sn = 1.68e-8, 1.32e-7
+    r_solder = v.barrel_resistance(1_600_000, rho, 18_000,
+                                   solder_rho_ohm_m=sn)
+    r_lead = v.barrel_resistance(1_600_000, rho, 18_000,
+                                 solder_rho_ohm_m=sn,
+                                 lead_nm=750_000, lead_rho_ohm_m=rho)
+    rl, rc = 0.375e-3, 0.5e-3 - 18e-6
+    ga = math.pi * 1e-3 * 18e-6 / rho
+    ga += math.pi * rl ** 2 / rho + math.pi * (rc ** 2 - rl ** 2) / sn
+    assert r_lead == pytest.approx(1.6e-3 / ga, rel=1e-12)
+    assert r_lead < r_solder
+    # a lead wider than the bore is clipped to it
+    r_big = v.barrel_resistance(1_600_000, rho, 18_000,
+                                solder_rho_ohm_m=sn,
+                                lead_nm=2_000_000, lead_rho_ohm_m=rho)
+    ga2 = math.pi * 1e-3 * 18e-6 / rho + math.pi * rc ** 2 / rho
+    assert r_big == pytest.approx(1.6e-3 / ga2, rel=1e-12)
+
+
+def test_oblong_pad_cone_uses_inscribed_dim():
+    """Oblong pads: the cone tapers to the inscribed circle (pad_min),
+    never past it, so the long pad axis is not overstated sideways."""
+    p = make_problem([(PLATE20, [])],
+                     rect1_mm=(0, 0, 1, 20), rect2_mm=(19, 0, 20, 20))
+    p.vias = [_pad_link()]
+    p.vias[0].pad_min_nm = 1_600_000          # 2.4 mm max, 1.6 mm min
+    stack = raster.rasterize_stack(p, 0.1 * NM)
+    ii, jj = np.nonzero(stack.thick_scale[0] != 1.0)
+    d = np.hypot(stack.x0_nm + (jj + 0.5) * stack.h_nm - 10 * NM,
+                 stack.y0_nm + (ii + 0.5) * stack.h_nm - 10 * NM)
+    assert len(d) and d.max() < 0.8 * NM
+
+
+def test_stitching_coat_exact_shape():
+    """When KiCad supplies the exact pad polygon, the coat uses it
+    instead of the pad-diameter disc (oblong pads stay honest)."""
+    p = make_problem([(PLATE20, [])],
+                     rect1_mm=(0, 0, 1, 20), rect2_mm=(19, 0, 20, 20))
+    p.vias = [_pad_link()]
+    shape = _disc(10, 10, 0.9)
+    assert tht_joint_buildups(p, {(10 * NM, 10 * NM): [shape]}) == ["F.Cu"]
+    assert p.buildups[0].polygons[0] is shape
+
+
+def test_vialink_solder_json():
+    p = make_problem([(PLATE20, [])],
+                     rect1_mm=(0, 0, 1, 20), rect2_mm=(19, 0, 20, 20))
+    p.vias = [_pad_link()]
+    d = problem_to_json(p)
+    q = problem_from_json(d)
+    assert q.vias[0].solder_filled is True
+    assert q.vias[0].protrusion_side == "F.Cu"
+    # legacy dumps without the flag: THT pads counted as solder-filled,
+    # vias as plating-only
+    del d["vias"][0]["solder_filled"], d["vias"][0]["protrusion_side"]
+    q = problem_from_json(d)
+    assert q.vias[0].solder_filled is True
+    assert q.vias[0].protrusion_side is None
+    d["vias"][0]["kind"] = "via"
+    assert problem_from_json(d).vias[0].solder_filled is False
+
+
+def test_barrel_electrode_json_roundtrip(tmp_path):
+    p = make_problem([(PLATE20, [])],
+                     rect1_mm=(0, 0, 1, 20), rect2_mm=(19, 0, 20, 20))
+    p.electrodes1 = [_barrel(10, 10, drill_mm=0.6, pad_mm=1.2, solder=True,
+                             polygons=[_disc(10, 10, 0.6)])]
+    p.electrodes1[0].barrel_z = (-1, 1_600_001)
+    p.electrodes1[0].protrusion_side = "B.Cu"
+    p.tht_protrusion_nm = 1_200_000
+    f = tmp_path / "d.json"
+    save_problem(p, f)
+    q = load_problem(f)
+    e = q.electrodes1[0]
+    assert e.drill_nm == 600_000 and e.pad_nm == 1_200_000
+    assert e.center == (10 * NM, 10 * NM)
+    assert e.barrel_z == (-1, 1_600_001)
+    assert e.solder is True and len(e.polygons) == 1
+    assert e.protrusion_side == "B.Cu"
+    assert q.tht_protrusion_nm == 1_200_000

tests/test_capping.py

@@ -9,10 +9,13 @@ from tests.util import NM, make_multilayer
 
 
 def _two_layer(width_mm=5.0, drill_mm=0.3, pad_mm=0.6, kind="via",
-               capped=True, cap_um=15.0, hole_mm=None):
+               capped=True, cap_um=15.0, hole_mm=None,
+               cap_max_drill_mm=10.0):
     """10 x width strip on both (outer-named) layers, e1 left on F.Cu,
     e2 right on B.Cu, one via mid-strip. Optionally a circular hole in
-    the F.Cu fill around the via (ring-bridging scenario)."""
+    the F.Cu fill around the via (ring-bridging scenario). The cap-drill
+    threshold defaults to 10 mm here (= every drill capped) so the tests
+    exercise the mouth treatment itself; the threshold has its own test."""
     y = width_mm / 2
     strip = [(0, 0), (10, 0), (10, width_mm), (0, width_mm)]
     holes = []
@@ -31,6 +34,7 @@ def _two_layer(width_mm=5.0, drill_mm=0.3, pad_mm=0.6, kind="via",
     p.vias[0].pad_nm = int(pad_mm * NM)
     p.vias_capped = capped
     p.cap_plating_nm = int(cap_um * 1000)
+    p.cap_max_drill_nm = int(cap_max_drill_mm * NM)
     return p
 
 
@@ -46,7 +50,13 @@ def test_cap_at_foil_thickness_is_identity():
     so the result equals the feature-off reference (a 'pad'-kind barrel,
     which skips rings and mouths) with the mouth fully inside copper."""
     r_cap, _ = _solve(_two_layer(capped=True, cap_um=70.0), 0.1)
-    r_ref, _ = _solve(_two_layer(kind="pad"), 0.1)
+    ref = _two_layer(kind="pad")
+    # populated pads skip rings and mouths; kill the lead + solder core
+    # so the reference barrel matches the via's plating-only resistance
+    ref.vias[0].solder_filled = True
+    ref.solder_rho_ohm_m = 1e30
+    ref.tht_lead_clearance_nm = 10 ** 9
+    r_ref, _ = _solve(ref, 0.1)
     assert r_cap.R_ohm == pytest.approx(r_ref.R_ohm, rel=1e-9)
 
 
@@ -90,14 +100,31 @@ def test_subcell_mouth_perturbs_gently():
     assert r_solid.R_ohm <= r_open.R_ohm <= 1.05 * r_solid.R_ohm
 
 
+def test_cap_drill_threshold():
+    """Drills above cap_max_drill_nm stay open even with capping on: a
+    2 mm drill over a 0.5 mm threshold behaves exactly like uncapped,
+    while a threshold above the drill restores the cap."""
+    kw = dict(drill_mm=2.0, pad_mm=2.6)
+    r_big, s_big = _solve(_two_layer(capped=True, cap_max_drill_mm=0.5,
+                                     **kw), 0.25)
+    r_open, s_open = _solve(_two_layer(capped=False, **kw), 0.25)
+    assert r_big.R_ohm == pytest.approx(r_open.R_ohm, rel=1e-12)
+    assert int(s_big.masks.sum()) == int(s_open.masks.sum())
+
+    r_cap, _ = _solve(_two_layer(capped=True, cap_max_drill_mm=2.1,
+                                 **kw), 0.25)
+    assert r_cap.R_ohm < r_open.R_ohm
+
+
 def test_capping_json_roundtrip(tmp_path):
     from fill_resistance.geometry import load_problem, save_problem
-    p = _two_layer(capped=False, cap_um=12.0)
+    p = _two_layer(capped=False, cap_um=12.0, cap_max_drill_mm=0.8)
     f = tmp_path / "d.json"
     save_problem(p, f)
     q = load_problem(f)
     assert q.vias_capped is False
     assert q.cap_plating_nm == 12_000
+    assert q.cap_max_drill_nm == 800_000
     r_p, _ = _solve(p, 0.25)
     r_q, _ = _solve(q, 0.25)
     assert r_q.R_ohm == pytest.approx(r_p.R_ohm, rel=1e-12)

tools/gen_readme_figs.py

@@ -0,0 +1,317 @@
+"""Generate the README model figures in docs/img/.
+
+    .venv\\Scripts\\python.exe tools\\gen_readme_figs.py
+
+Real solver output wherever possible: the demo-board maps (raster map
+with the adaptive mesh, current density) and the contact-model
+comparison come straight from the plugin's own pipeline on small
+synthetic boards; only the hole-anatomy cross-section is drawn by hand.
+"""
+import sys
+from pathlib import Path
+
+import numpy as np
+
+ROOT = Path(__file__).resolve().parents[1]
+sys.path.insert(0, str(ROOT))
+
+from fill_resistance import config  # noqa: E402
+
+config.INTERACTIVE = False
+
+import matplotlib  # noqa: E402
+
+matplotlib.use("Agg", force=True)
+
+from fill_resistance import plots, raster, solver  # noqa: E402
+from fill_resistance.geometry import (Electrode, LayerFill, Polygon,  # noqa: E402
+                                      Problem, Rect, ViaLink,
+                                      contact_solder_buildups)
+
+import matplotlib.pyplot as plt  # noqa: E402
+
+plt.switch_backend("Agg")
+plots.INTERACTIVE_BACKEND = None      # save-only: no window panels
+
+NM = 1_000_000
+OUT = ROOT / "docs" / "img"
+
+COPPER = plots._COPPER
+SOLDER = plots._SOLDER
+LEAD = "#5c6570"
+CORE = "#ccd6b3"                      # FR-4
+FILLER = "#eae5dc"                    # non-conductive via fill
+INK = plots._INK
+
+
+def _poly(pts_mm, holes_mm=()) -> Polygon:
+    ring = lambda pts: np.asarray(  # noqa: E731
+        [[int(x * NM), int(y * NM)] for x, y in pts], dtype=np.int64)
+    return Polygon(outline=ring(pts_mm),
+                   holes=[ring(h) for h in holes_mm])
+
+
+def _rect(x0, y0, x1, y1, layer="User.1") -> Rect:
+    return Rect.normalized(int(x0 * NM), int(y0 * NM),
+                           int(x1 * NM), int(y1 * NM), layer)
+
+
+def _disc(x_mm, y_mm, r_mm, n=64) -> Polygon:
+    ang = np.linspace(0, 2 * np.pi, n, endpoint=False)
+    return _poly([(x_mm + r_mm * np.cos(a), y_mm + r_mm * np.sin(a))
+                  for a in ang])
+
+
+def _solve(problem, h_mm, i_test=10.0, model=None):
+    stack = raster.rasterize_stack(problem, int(h_mm * NM))
+    e1, e2 = raster.electrode_masks(stack, problem)
+    p1, p2 = raster.electrode_partition(stack, problem)
+    res = solver.run_solve(problem, stack, e1, e2, i_test,
+                           contact_model=model, parts1=p1, parts2=p2)
+    return res, stack, e1, e2
+
+
+# --- demo board: 2 layers, notched F.Cu pour, half-size B.Cu pour, ----
+# --- a soldered THT-pad contact and a stitching-via field -------------
+
+def demo_problem() -> Problem:
+    # F.Cu: full pour with a notch from the top edge down to y=6 - the
+    # current from the left contact must squeeze through the channel
+    top = _poly([(0, 0), (40, 0), (40, 22), (13, 22), (13, 6),
+                 (10, 6), (10, 22), (0, 22)])
+    # B.Cu: pour on the right half only - vias must carry the transfer
+    bot = _poly([(18, 0), (40, 0), (40, 22), (18, 22)])
+    z_bot = int(1.6 * NM)
+    vias = [ViaLink(x=int(x * NM), y=int(y * NM), drill_nm=300_000,
+                    z_top_nm=-1, z_bot_nm=z_bot + 1, pad_nm=600_000)
+            for x in (20.5, 24.5, 28.5, 32.5, 36) for y in (3, 7, 11, 15, 19)]
+    tht = Electrode(
+        rect=_rect(3.4, 9.9, 5.6, 12.1), contact="F.Cu",
+        label="THT pad (4.5, 11)", drill_nm=1_000_000,
+        pad_nm=int(2.2 * NM), pad_min_nm=int(2.2 * NM),
+        center=(int(4.5 * NM), int(11 * NM)), solder=True,
+        protrusion_side="F.Cu", polygons=[_disc(4.5, 11, 1.1)])
+    lug = Electrode(rect=_rect(37.5, 3, 39.5, 19, "User.2"),
+                    contact="B.Cu", label="lug")
+    p = Problem(
+        board_path="synthetic", net_name="DEMO",
+        rho_ohm_m=1.68e-8, plating_nm=18_000,
+        layers=[LayerFill("F.Cu", 70_000, 0, [top]),
+                LayerFill("B.Cu", 70_000, z_bot, [bot])],
+        vias=vias, electrodes1=[tht], electrodes2=[lug],
+        thickness_source="override")
+    contact_solder_buildups(p)
+    return p
+
+
+def gen_demo_maps():
+    p = demo_problem()
+    res, stack, e1, e2 = _solve(p, 0.05)
+    figs = [
+        (plots.fig_raster(stack, e1, e2, p, res), "demo-raster"),
+        (plots.fig_current(res, stack, e1, e2, p), "demo-current"),
+        (plots.fig_potential(res, stack, e1, e2, p), "demo-potential"),
+    ]
+    plots.save_and_show(figs, OUT, show=False)
+
+
+# --- contact models: equipotential vs uniform injection ---------------
+
+def gen_contact_models():
+    plate = [(0, 0), (24, 0), (24, 18), (0, 18)]
+    r_ohm, zooms = {}, {}
+    # uniform grid: the coarse adaptive leaves would pixelate the |J| zoom
+    config.ADAPTIVE_CELLS = False
+    for model in ("equipotential", "uniform"):
+        p = Problem(
+            board_path="synthetic", net_name="DEMO",
+            rho_ohm_m=1.68e-8, plating_nm=18_000,
+            layers=[LayerFill("F.Cu", 70_000, 0, [_poly(plate)])],
+            vias=[],
+            electrodes1=[Electrode(rect=_rect(4.5, 7.5, 7.5, 10.5))],
+            electrodes2=[Electrode(rect=_rect(22, 1, 23.5, 17, "User.2"))],
+            thickness_source="override")
+        res, stack, _, _ = _solve(p, 0.05, model=model)
+        h_mm = stack.h_nm / NM
+        j = res.Jmag[0] * 1e-6                       # A/mm^2
+        x0, y0 = stack.x0_nm / NM, stack.y0_nm / NM
+        c0, c1 = int((2 - x0) / h_mm), int((13 - x0) / h_mm)
+        r0, r1 = int((3 - y0) / h_mm), int((15 - y0) / h_mm)
+        zooms[model] = (j[r0:r1, c0:c1],
+                        (x0 + c0 * h_mm, x0 + c1 * h_mm,
+                         y0 + r1 * h_mm, y0 + r0 * h_mm))
+        r_ohm[model] = res.R_ohm
+    config.ADAPTIVE_CELLS = True
+
+    vmax = float(np.percentile(
+        zooms["equipotential"][0][np.isfinite(zooms["equipotential"][0])],
+        99.0))
+    fig, axes = plt.subplots(1, 2, figsize=(9.5, 4.2), sharey=True,
+                             layout="constrained")
+    titles = {"equipotential": "equipotential (ideal bonded lug):\n"
+                               "|J| crowds at the contact edges",
+              "uniform": "uniform injection (pressed conductor):\n"
+                         "|J| ramps across the contact"}
+    for ax, model in zip(axes, ("equipotential", "uniform")):
+        data, extent = zooms[model]
+        cmap = matplotlib.colormaps[config.CMAP_CURRENT].copy()
+        cmap.set_bad(plots._BG)
+        im = ax.imshow(data, cmap=cmap, vmin=0, vmax=vmax, origin="upper",
+                       extent=extent, interpolation="nearest")
+        ax.add_patch(plt.Rectangle((4.5, 7.5), 3, 3, fill=False,
+                                   ec="white", ls="--", lw=1.0))
+        ax.set_title(f"{titles[model]}\nR = {r_ohm[model] * 1e3:.3f} mΩ",
+                     fontsize=9, color=INK)
+        ax.set_xlabel("x [mm]", fontsize=8)
+        ax.tick_params(labelsize=8, colors=INK)
+    axes[0].set_ylabel("y [mm]", fontsize=8)
+    cb = fig.colorbar(im, ax=axes, shrink=0.85)
+    cb.set_label("|J| [A/mm²] @ 10 A", fontsize=9)
+    fig.suptitle("The two contact models bracket a real contact:  "
+                 "R$_{equipotential}$ ≤ R$_{real}$ ≤ R$_{uniform}$",
+                 fontsize=10, color=INK)
+    fig.savefig(OUT / "contact-models.png", dpi=config.DPI,
+                facecolor="white", bbox_inches="tight")
+    plt.close(fig)
+    print(f"saved {OUT / 'contact-models.png'}")
+
+
+# --- hole anatomy: hand-drawn cross-section of the four hole types ----
+
+CORE_T = 1.6          # substrate thickness [drawing units ~ mm]
+FOIL_T = 0.18         # foil thickness, exaggerated
+PLATE_W = 0.12        # barrel plating, exaggerated
+CAP_T = 0.07          # via cap
+COAT_T = 0.1          # pad-face solder coat
+Y_TOP = CORE_T + FOIL_T
+
+
+def _board_segment(ax, x0, x1):
+    ax.add_patch(plt.Rectangle((x0, 0), x1 - x0, CORE_T, fc=CORE, ec="none"))
+    for y in (CORE_T, -FOIL_T):
+        ax.add_patch(plt.Rectangle((x0, y), x1 - x0, FOIL_T,
+                                   fc=COPPER, ec="none"))
+
+
+def _barrel(ax, xc, drill):
+    for s in (-1, 1):
+        x = xc + s * drill / 2 - (PLATE_W if s > 0 else 0)
+        ax.add_patch(plt.Rectangle((x, -FOIL_T), PLATE_W,
+                                   CORE_T + 2 * FOIL_T, fc=COPPER,
+                                   ec="none"))
+
+
+def _label(ax, text, xy, xytext, ha="left"):
+    ax.annotate(text, xy, xytext=xytext, fontsize=7.5, color=INK, ha=ha,
+                va="center",
+                arrowprops=dict(arrowstyle="-", color=INK, lw=0.7,
+                                shrinkA=2, shrinkB=1))
+
+
+def gen_hole_anatomy():
+    fig, ax = plt.subplots(figsize=(12.5, 5.2), layout="constrained")
+    holes = [(3.0, 0.7), (10.0, 1.6), (17.5, 1.6), (25.0, 1.6)]
+    edges = [0.0]
+    for xc, d in holes:
+        edges += [xc - d / 2, xc + d / 2]
+    edges.append(28.5)
+    for x0, x1 in zip(edges[::2], edges[1::2]):
+        _board_segment(ax, x0, x1)
+    for xc, d in holes:
+        _barrel(ax, xc, d)
+
+    # 1: small via, filled + capped
+    xc, d = holes[0]
+    ax.add_patch(plt.Rectangle((xc - d / 2 + PLATE_W, -FOIL_T),
+                               d - 2 * PLATE_W, CORE_T + 2 * FOIL_T,
+                               fc=FILLER, ec="none"))
+    for y in (Y_TOP, -FOIL_T - CAP_T):
+        ax.add_patch(plt.Rectangle((xc - d / 2 - 0.12, y), d + 0.24, CAP_T,
+                                   fc=COPPER, ec="none"))
+    _label(ax, "cap, CAP_PLATING_UM (15 µm)\non both outer mouths",
+           (xc, Y_TOP + CAP_T), (xc, 3.3), ha="center")
+    _label(ax, "non-conductive fill", (xc, 0.8), (5.6, -0.9))
+
+    # 2: big via, mouth open
+    xc, d = holes[1]
+    _label(ax, "open mouth: covered cells\nremoved, sub-cell mouths\n"
+               "scale the sheet conductance",
+           (xc, Y_TOP - FOIL_T / 2), (xc, 3.2), ha="center")
+
+    # 3: populated THT pad - full solder joint
+    xc, d = holes[2]
+    lead_w = d - 0.5                      # drill - clearance, exaggerated
+    pad_r = 1.7
+    prot = 1.5
+    sn_edge = "#7d8791"                   # delineate solder sub-shapes
+    # solder fill between plating and lead
+    for s in (-1, 1):
+        x0 = xc + s * lead_w / 2 if s > 0 else xc - d / 2 + PLATE_W
+        ax.add_patch(plt.Rectangle((x0, -FOIL_T),
+                                   d / 2 - PLATE_W - lead_w / 2,
+                                   CORE_T + 2 * FOIL_T, fc=SOLDER,
+                                   ec="none"))
+    # pad-face coat, solder side only
+    ax.add_patch(plt.Rectangle((xc - pad_r, Y_TOP), 2 * pad_r, COAT_T,
+                               fc=SOLDER, ec=sn_edge, lw=0.5))
+    # solder cone: protrusion height at the wall -> 0 at the pad edge
+    for s in (-1, 1):
+        wall = xc + s * lead_w / 2
+        ax.add_patch(plt.Polygon(
+            [(wall, Y_TOP + prot), (wall, Y_TOP + COAT_T),
+             (xc + s * pad_r, Y_TOP + COAT_T)],
+            closed=True, fc=SOLDER, ec=sn_edge, lw=0.5))
+    # lead: through the hole, protruding on top, component below
+    ax.add_patch(plt.Rectangle((xc - lead_w / 2, -2.05), lead_w,
+                               2.05 + Y_TOP + prot, fc=LEAD, ec="none"))
+    ax.add_patch(plt.Rectangle((xc - 1.5, -2.75), 3.0, 0.7,
+                               fc="#8a8f96", ec="none"))
+    ax.text(xc, -2.4, "component", fontsize=7.5, color="white",
+            ha="center", va="center")
+    _label(ax, "clipped lead protrudes\nTHT_LEAD_PROTRUSION_MM (1.5 mm)",
+           (xc + lead_w / 2, Y_TOP + prot - 0.2), (xc + 3.4, 4.15))
+    _label(ax, "solder cone: full height at the\nwall, tapers to 0 at the "
+               "pad edge", (xc - (lead_w / 2 + pad_r) / 2, Y_TOP + 0.7),
+           (13.6, 4.2), ha="center")
+    _label(ax, "pad-face solder coat (50 µm),\nSOLDER side only",
+           (xc - pad_r + 0.2, Y_TOP + COAT_T / 2), (12.9, 2.35),
+           ha="center")
+    _label(ax, "solder-filled hole: lead ∥ solder ∥ plating\n"
+               "lead ⌀ = drill − THT_LEAD_CLEARANCE_MM",
+           (xc - d / 2 + PLATE_W + 0.07, 0.5), (12.3, -1.5), ha="center")
+    _label(ax, "component side:\npad face stays bare",
+           (xc + pad_r - 0.3, -FOIL_T), (xc + 4.0, -1.05))
+
+    # 4: DNP THT pad
+    xc, d = holes[3]
+    _label(ax, "open hole on every layer,\nplating-only barrel, no joint",
+           (xc, 0.8), (xc + 1.3, -2.45), ha="center")
+
+    for (xc, _), title in zip(holes, (
+            "via ≤ cap-drill\n(capped)", "via > cap-drill\n(open)",
+            "THT pad, populated\n(read from KiCad)", "THT pad, DNP")):
+        ax.text(xc, 5.6, title, fontsize=9, color=INK, ha="center",
+                va="top", fontweight="bold")
+
+    handles = [plt.Rectangle((0, 0), 1, 1, fc=c) for c in
+               (COPPER, SOLDER, LEAD, CORE, FILLER)]
+    fig.legend(handles, ("copper (foil / plating / pad)", "solder",
+                         "component lead", "FR-4", "non-conductive fill"),
+               loc="outside right center", fontsize=8, framealpha=0.95)
+    ax.set_title("How drilled holes are modeled — cross-section "
+                 "(vertical scale exaggerated)", fontsize=11, color=INK)
+    ax.set_xlim(-0.3, 29.0)
+    ax.set_ylim(-3.1, 5.7)
+    ax.set_aspect("equal")
+    ax.axis("off")
+    fig.savefig(OUT / "hole-model.png", dpi=config.DPI,
+                facecolor="white", bbox_inches="tight")
+    plt.close(fig)
+    print(f"saved {OUT / 'hole-model.png'}")
+
+
+if __name__ == "__main__":
+    OUT.mkdir(parents=True, exist_ok=True)
+    gen_hole_anatomy()
+    gen_contact_models()
+    gen_demo_maps()