Source: https://guthlabs.ai/docs/instruments/pcb-via-current-capacity-calculator/mechanism/

instrument mechanism / verified-clean

# PCB Via Current Capacity Calculator mechanism

The inspectable method record for PCB Via Current Capacity Calculator, kept separate from implementation and qualification.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## 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

[01**Overview**](<https://guthlabs.ai/docs/instruments/pcb-via-current-capacity-calculator/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/pcb-via-current-capacity-calculator/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/pcb-via-current-capacity-calculator/qualification/>)

## 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`