PCB Via Current Capacity Calculator mechanism

Model scope

The supplied spec is insufficient to verify the claimed IPC-2221 implementation. The four vectors are conditional checks for the explicitly stated provisional formula I = 0.024 × ΔT^0.44 × [π × t × (D + t)]^0.725 with dimensions in mils. Before release, specify the exact IPC-2221 equation and constants, define all diameter and plating terms, enforce input constraints, and document whether the result is continuous DC current for an isolated internal via or a via connected to planes and traces.

• The specification does not provide an explicit formula, exponent values, coefficient, or IPC-2221 constant set, so the claimed calculation cannot be verified.
• The phrase "similar exponent form to trace calc" is ambiguous and does not establish that the IPC-2221 conductor formula is valid for a plated via barrel.
• A via thermal model generally requires more than via diameter, plating thickness, temperature rise, and via count; board stackup, copper-plane connections, via length, thermal paths, and ambient conditions may materially affect capacity.
• Multiplying per-via current by via count assumes identical vias, equal current sharing, adequate spacing, and no thermal or electrical coupling; those constraints are not specified.
• The term "via diameter" is ambiguous: it could mean finished hole diameter, drill diameter, barrel outside diameter, or pad diameter.
• The calculator claims "max current," but an empirical thermal estimate should be labeled as an approximate continuous-current estimate unless transient behavior and allowable operating conditions are defined.

Units and conventions

• The conditional test vectors use the common IPC-2221-style empirical form I = 0.024 × ΔT^0.44 × A^0.725 for internal copper, with I in amperes, ΔT in °C, and A in square mils.
• For these conditional vectors, via barrel conductive cross-sectional area is assumed to be A = π × t × (D + t), where D is finished hole diameter and t is plating thickness, both in mils.
• Metric dimensions in the fourth vector are converted using 1 mil = 0.0254 mm before applying the assumed formula.
• Via count is assumed to be a positive integer and array current is assumed to equal count × per-via current under perfect equal sharing.
• The coefficient and geometry assumptions are provisional because the supplied specification does not identify the exact IPC-2221 equation or constants.

Inspectable vector

One of 4 source-bound review vectors:

{
  "inputs": {
    "via_diameter_mil": 20,
    "plating_thickness_mil": 1,
    "delta_T_C": 10,
    "via_count": 1
  },
  "expected_outputs": {
    "max_current_per_via_A": 1.378,
    "max_current_array_A": 1.378
  },
  "working": "A = π × t × (D + t) = 3.14159265 × 1 × (20 + 1) = 65.9734 mil². ΔT^0.44 = 10^0.44 = 2.75423. A^0.725 = 65.9734^0.725 ≈ 20.8469. I_via = 0.024 × 2.75423 × 20.8469 = 1.378 A. I_array = 1 × 1.378 = 1.378 A."
}

Failure boundary

BREAK_CLAIMED · SELF_FLAGGED

The model has an undefined real-valued result for negative delta_T, and the supplied specification omits the IPC constant selection, dimensional units, and any thermal-environment branch input. Consequently, identical numeric entries can produce materially different results or NaN unless the calculator validates and disambiguates them.

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche4/tranche4-results.json
• BOUNDARY_HAZARD_CATALOG.json