Full solder joint at every populated THT pad, read from KiCad

No size-threshold guessing: whether a hole is a via or a THT pad
already comes from KiCad (board.get_vias vs drilled board.get_pads).
Every populated THT pad of the net now carries the complete joint the
contacts got: solder-filled barrel, average-thickness coat over a
pad-diameter disc on the outer layers, and the protruding-lead cone on
the side opposite its owning footprint. The footprint side and the
Do-not-populate flag are read from KiCad (footprint pads store absolute
positions, so owner lookup is an exact (x, y, number) map); DNP pads
stay plating-only with no joint. Contact pads are deduplicated by
barrel center so their cone/coat is never applied twice.

Barrels are now gathered in single-layer runs too: via rings and drill
mouths perforate a lone plane, THT joints stiffen it locally.

ViaLink gains solder_filled + protrusion_side (legacy dumps load with
the old every-THT-pad-filled semantics).

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

README.md

@@ -85,11 +85,18 @@ SWIG API. Requires KiCad **10.0.1+**.
   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
+  perturbation instead of a whole-cell hole. Barrels are gathered in
-  remain outside the model, but THT-pad **barrels are solder-filled**
+  **single-layer runs too** (drill mouths perforate a lone plane).
-  (a soldered component lead): the solder core (SAC305) conducts in
+  THT-pad copper and drills remain outside the model, but every
-  parallel with the plating annulus. At f > 0 the thickness scaling is
+  **populated THT pad** of the net carries its full **soldered
-  applied multiplicatively to the skin-corrected sheet conductance
+  joint**: a solder-filled barrel (SAC305 core in parallel with the
+  plating), the average-thickness solder coat over a pad-diameter disc
+  on the outer layers, and the protruding-lead cone on the side
+  opposite its footprint (see barrel contacts below). 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 stay plating-only
+  with 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

fill_resistance/board_io.py

@@ -23,7 +23,8 @@ from . import config
 from .errors import ApiVersionError, CandidateError, SelectionError
 from .geometry import (Electrode, LayerFill, Polygon, Problem, Rect,
                        SurfaceBuildup, TrackSeg, ViaLink,
-                       contact_solder_buildups, linearize_ring)
+                       contact_solder_buildups, linearize_ring,
+                       tht_joint_buildups)
 
 MASK_TO_COPPER = {"F.Mask": "F.Cu", "B.Mask": "B.Cu"}
 
@@ -180,29 +181,42 @@ def _pad_polygons(board: Board, pad: Pad, contact: str) -> list[Polygon] | None:
     return None
 
 
-def _tht_protrusion_side(pad: Pad, footprints) -> str:
+def _footprint_pad_map(footprints) -> dict:
-    """Outer layer where the clipped THT lead protrudes (tent + solder
+    """(x, y, number) -> owning FootprintInstance. Footprint pads are
-    cone): the side OPPOSITE the component. Footprint pads are stored
+    stored with absolute positions, so the lookup is exact."""
-    with absolute positions, so the owning footprint is matched by pad
+    out = {}
-    number + position. Unknown owner -> assume the component sits on
-    F.Cu (lead tents on B.Cu)."""
-    try:
     for fp in footprints or []:
+        try:
             for fpad in fp.definition.pads:
-                if fpad.number == pad.number \
+                out[(fpad.position.x, fpad.position.y, fpad.number)] = fp
-                        and fpad.position.x == pad.position.x \
+        except Exception:
-                        and fpad.position.y == pad.position.y:
+            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
-    print(f"note: no footprint found for pad {pad.number} - assuming its "
+    if not quiet:
-          f"lead protrudes on B.Cu")
+        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,
-                  footprints=None) -> Electrode:
+                  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,
@@ -245,7 +259,7 @@ def _to_electrode(board: Board, item, stackup: StackupInfo | None = None,
                      drill_nm=drill, pad_nm=_padstack_pad_nm(pad),
                      center=(pad.position.x, pad.position.y),
                      solder=drill > 0,
-                     protrusion_side=(_tht_protrusion_side(pad, footprints)
+                     protrusion_side=(_tht_protrusion_side(pad, pad_map or {})
                                       if drill > 0 else None))
 
 
@@ -282,9 +296,9 @@ def get_electrodes(board: Board, stackup: StackupInfo | None = None
     rects = [s for s in selection if isinstance(s, BoardRectangle)]
     pads = [s for s in selection if isinstance(s, (Pad, Via))]
     # protrusion-side lookup needs the owning footprints (THT pads only)
-    footprints = (board.get_footprints()
+    pad_map = (_footprint_pad_map(board.get_footprints())
                if any(isinstance(s, Pad) and _pad_drill_nm(s) > 0
-                         for s in pads) else None)
+                      for s in pads) else {})
 
     if not selection:
         allr = [s for s in board.get_shapes() if isinstance(s, BoardRectangle)]
@@ -320,7 +334,7 @@ def get_electrodes(board: Board, stackup: StackupInfo | None = None
                 f"only for a side that has none."
             )
         if pads:
-            pad_parts = [_to_electrode(board, p, stackup, footprints)
+            pad_parts = [_to_electrode(board, p, stackup, pad_map)
                          for p in pads]
             if not es1:
                 es1 = pad_parts
@@ -335,8 +349,8 @@ def get_electrodes(board: Board, stackup: StackupInfo | None = None
 
     items = rects + pads
     if len(items) == 2:
-        return ([_to_electrode(board, items[0], stackup, footprints)],
+        return ([_to_electrode(board, items[0], stackup, pad_map)],
-                [_to_electrode(board, items[1], stackup, footprints)],
+                [_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 "
@@ -503,16 +517,35 @@ 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():
+        net_pads = [pad for pad in board.get_pads()
-            if pad.net is None or pad.net.name != net_name:
+                    if pad.net is not None and pad.net.name == net_name
-                continue
+                    and _pad_drill_nm(pad) > 0]
-            drill = _pad_drill_nm(pad)
+        # populated (non-DNP) THT pads carry a soldered joint: filled
-            if drill <= 0:
+        # hole + coat + lead cone on the side opposite the component
-                continue
+        pad_map = (_footprint_pad_map(board.get_footprints())
-            barrels.append(ViaLink(x=pad.position.x, y=pad.position.y,
+                   if net_pads else {})
-                                   drill_nm=drill, z_top_nm=-1,
+        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),
+                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
 
 
@@ -550,7 +583,9 @@ 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)
     included = {l.layer_name for l in layers}
     buildup_list = [
         SurfaceBuildup(layer_name=name, polygons=polys)
@@ -597,6 +632,15 @@ def build_problem(board: Board, net: str, layer_names: list[str],
         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)
+    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): solder-filled hole + "
+              f"coat + lead cone"
+              + (f"; {n_dnp} DNP pad(s) plating-only" if n_dnp else ""))
     return problem
 
 

fill_resistance/geometry.py

@@ -134,6 +134,14 @@ class ViaLink:
     z_bot_nm: int
     kind: str = "via"                         # "via" | "pad"
     pad_nm: int = 0                           # pad/annular diameter; 0 = unknown
+    solder_filled: bool = False               # populated THT pad: the hole is
+                                              # solder-filled (core 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
@@ -227,6 +235,38 @@ def contact_solder_buildups(problem: Problem) -> list[str]:
     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) -> list[str]:
+    """Solder coat of the net's populated STITCHING through-hole pads
+    (ViaLink kind 'pad' with solder_filled): one pad-diameter disc per
+    outer layer - the exact pad shape is unknown for non-contact pads,
+    and the coat intersects the modeled copper at raster time anyway.
+    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}
+    outer = [n for n in ("F.Cu", "B.Cu") if n in included]
+    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.pad_nm <= v.drill_nm or (v.x, v.y) in contacts:
+            continue
+        disc = _disc_polygon(v.x, v.y, v.pad_nm / 2.0)
+        for name in outer:
+            problem.buildups.append(
+                SurfaceBuildup(layer_name=name, polygons=[disc]))
+            touched.append(name)
+    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."""
@@ -485,7 +525,11 @@ 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)),
+                    # 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=(

fill_resistance/raster.py

@@ -238,9 +238,10 @@ def rasterize_stack(problem: Problem, h_nm: float) -> RasterStack:
 
 
 def _paint_lead_fillets(stack: RasterStack, problem: Problem) -> None:
-    """Protruding THT leads of soldered barrel contacts: the clipped
+    """Protruding THT leads (barrel contacts AND the net's populated
-    lead sticks tht_protrusion_nm out of the hole on the side opposite
+    stitching through-hole pads): the clipped lead sticks
-    the component, wrapped by a solder cone - full protrusion height at
+    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
@@ -254,18 +255,32 @@ def _paint_lead_fillets(stack: RasterStack, problem: Problem) -> None:
     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 not (e.solder and e.drill_nm > 0 and e.protrusion_side):
+        if e.drill_nm <= 0:
-            continue
-        li = index.get(e.protrusion_side)
-        if li is None or e.pad_nm <= e.drill_nm:
             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
-        ra, rb = e.drill_nm / 2.0, e.pad_nm / 2.0
+        seen.add((int(x), int(y)))
+        if e.solder and e.protrusion_side:
+            jobs.append((x, y, e.drill_nm, 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_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))

fill_resistance/solver.py

@@ -178,12 +178,13 @@ def _barrel_links(stack: RasterStack, problem: Problem
             length = problem.layers[lb].z_nm - problem.layers[la].z_nm
             if length <= 0:
                 continue
-            # THT pads carry a soldered component lead: the hole is
+            # populated THT pads carry a soldered component lead: the hole
-            # solder-filled, the core conducts in parallel with the plating
+            # is solder-filled, the core conducts 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.kind == "pad" else None))
+                                  if via.solder_filled else None))
             links.append((vi, la, ia, ja, lb, ib, jb, r_dc))
     return links, dead
 

tests/test_barrel_contacts.py

@@ -9,7 +9,8 @@ import pytest
 from fill_resistance import raster, solver
 from fill_resistance.geometry import (Electrode, Polygon, ViaLink,
                                       contact_solder_buildups, load_problem,
-                                      save_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)]
@@ -195,6 +196,72 @@ def test_lead_fillet_lowers_resistance(monkeypatch):
     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: coat discs on the outer layers and a cone on its protrusion
+    side; a DNP pad gets neither."""
+    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()
+
+    q = prob(populated=False)
+    assert tht_joint_buildups(q) == []
+    r_bare, s2 = _solve(q, 0.1)
+    assert s2.thick_scale is None and s2.buildup is None
+    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_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))

tests/test_capping.py

@@ -50,11 +50,9 @@ 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)
-    ref = _two_layer(kind="pad")
+    # a bare 'pad' barrel (solder_filled defaults False) is plating-only,
-    # 'pad' barrels are solder-filled; kill the core so the reference
+    # exactly like the via's
-    # barrel matches the via's plating-only resistance exactly
+    r_ref, _ = _solve(_two_layer(kind="pad"), 0.1)
-    ref.solder_rho_ohm_m = 1e30
-    r_ref, _ = _solve(ref, 0.1)
     assert r_cap.R_ohm == pytest.approx(r_ref.R_ohm, rel=1e-9)