janik
06c62e04f8
DC/AC resistance, power dissipation, and via/injection-area currents of copper zone fills. KiCad 10 IPC-API plugin (kicad-python/kipy): multi-layer via-coupled FDM solver, multi-part terminals via User.1/User.2 marker layers, pads as contacts, uniform-injection and equipotential contact models, per-foil skin effect, optional solder/copper buildup on mask openings. 54-case test suite incl. exact analytic references. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
107 lines
4.2 KiB
Python
107 lines
4.2 KiB
Python
"""Solder/mask-opening buildup tests. Uniform-coverage and split-coverage
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strips are 1D-exact, validating the harmonic-mean face weights and the
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parallel-sheet conductance model to solver precision."""
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import numpy as np
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import pytest
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from fill_resistance import raster, solver
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from fill_resistance.geometry import (Polygon, SurfaceBuildup, load_problem,
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save_problem)
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from tests.util import NM, make_problem, ring_mm, sigma_s, strip_problem
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RHO_CU = 1.68e-8
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RHO_SN = 1.32e-7
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def _with_buildup(p, polys_mm, layer="F.Cu", solder_um=50.0, extra_um=0.0):
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p.buildups = [SurfaceBuildup(
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layer_name=layer,
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polygons=[Polygon(outline=ring_mm(pts)) for pts in polys_mm])]
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p.solder_thickness_nm = int(solder_um * 1000)
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p.solder_rho_ohm_m = RHO_SN
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p.extra_cu_nm = int(extra_um * 1000)
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return p
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def _solve(problem, h_mm):
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stack = raster.rasterize_stack(problem, h_mm * NM)
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e1, e2 = raster.electrode_masks(stack, problem)
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return solver.run_solve(problem, stack, e1, e2, 1.0,
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contact_model="equipotential"), stack
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def _sigma_buildup(solder_um=50.0, extra_um=0.0):
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return solder_um * 1e-6 / RHO_SN + extra_um * 1e-6 / RHO_CU
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def test_full_coverage_exact():
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"""Buildup over the whole strip: uniform parallel sheet, exact."""
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plain = strip_problem(length=50, width=10, e_len=5)
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covered = _with_buildup(strip_problem(length=50, width=10, e_len=5),
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[[(0, 0), (50, 0), (50, 10), (0, 10)]])
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r0, _ = _solve(plain, 0.5)
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r1, stack = _solve(covered, 0.5)
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sig = sigma_s() + _sigma_buildup()
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assert r1.R_ohm == pytest.approx(81 / 20 / sig, rel=1e-9)
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assert r1.R_ohm < r0.R_ohm
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assert stack.buildup is not None and stack.buildup.any()
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def test_half_coverage_series_exact():
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"""Buildup over the right half: plain faces + one harmonic-mean
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interface face + buildup faces in series, exact."""
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p = _with_buildup(strip_problem(length=50, width=10, e_len=5),
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[[(25, 0), (50, 0), (50, 10), (25, 10)]])
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res, _ = _solve(p, 0.5)
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s1 = sigma_s()
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s2 = s1 + _sigma_buildup()
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r_row = 40 / s1 + (s1 + s2) / (2 * s1 * s2) + 40 / s2
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assert res.R_ohm == pytest.approx(r_row / 20, rel=1e-9)
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def test_buildup_only_over_hole_is_inert():
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"""Solder wets copper only: an opening over a hole changes nothing."""
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holed = [([(0, 0), (50, 0), (50, 10), (0, 10)],
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[[(20, 2), (30, 2), (30, 8), (20, 8)]])]
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plain = make_problem(holed, rect1_mm=(0, 0, 5, 10),
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rect2_mm=(45, 0, 50, 10))
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masked = _with_buildup(
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make_problem(holed, rect1_mm=(0, 0, 5, 10),
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rect2_mm=(45, 0, 50, 10)),
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[[(21, 3), (29, 3), (29, 7), (21, 7)]]) # strictly inside the hole
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r0, _ = _solve(plain, 0.5)
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r1, _ = _solve(masked, 0.5)
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assert r1.R_ohm == pytest.approx(r0.R_ohm, rel=1e-12)
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def test_extra_copper_helps_more_than_solder():
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base = strip_problem(length=50, width=10, e_len=5)
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solder_only = _with_buildup(strip_problem(length=50, width=10, e_len=5),
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[[(0, 0), (50, 0), (50, 10), (0, 10)]])
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with_cu = _with_buildup(strip_problem(length=50, width=10, e_len=5),
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[[(0, 0), (50, 0), (50, 10), (0, 10)]],
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extra_um=70.0)
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r0, _ = _solve(base, 0.5)
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r1, _ = _solve(solder_only, 0.5)
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r2, _ = _solve(with_cu, 0.5)
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assert r2.R_ohm < r1.R_ohm < r0.R_ohm
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# 50 um SAC solder ~ 6.4 um Cu: expect a modest (<15%) improvement
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assert r1.R_ohm > 0.85 * r0.R_ohm
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# +70 um Cu roughly halves R (2x thickness + solder)
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assert r2.R_ohm < 0.55 * r0.R_ohm
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def test_json_v4_roundtrip(tmp_path):
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p = _with_buildup(strip_problem(), [[(0, 0), (50, 0), (50, 10), (0, 10)]],
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extra_um=35.0)
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f = tmp_path / "d.json"
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save_problem(p, f)
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q = load_problem(f)
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assert len(q.buildups) == 1 and q.buildups[0].layer_name == "F.Cu"
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assert q.solder_thickness_nm == 50_000
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assert q.extra_cu_nm == 35_000
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assert q.solder_rho_ohm_m == pytest.approx(RHO_SN)
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r_p, _ = _solve(p, 0.5)
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r_q, _ = _solve(q, 0.5)
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assert r_q.R_ohm == pytest.approx(r_p.R_ohm, rel=1e-12)
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