Source: https://guthlabs.ai/docs/instruments/pcb-trace-width-calculator-ipc-2221/implementation/

instrument implementation / implementation-contract

# PCB Trace Width Calculator (IPC-2221) implementation

A source-bound implementation contract for PCB Trace Width Calculator (IPC-2221); deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t4-198

**Effect**: Computation or source lookup only

## Input and validation requirements

Zero allowed temperature rise produces a zero denominator and an undefined or unbounded required area; zero current produces a mathematically zero but physically unusable trace width; and literal negative-current handling can leave the real-number domain unless current magnitude is explicitly used.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "current_A": 2,
    "temperature_rise_C": 10,
    "copper_weight_oz": 1,
    "layer": "external"
  },
  "expected_outputs": {
    "cross_section_area_mil2": 42.39,
    "trace_width_mil": 30.76,
    "trace_width_mm": 0.7814
  },
  "working": "External k = 0.048. ΔT^0.44 = 10^0.44 ≈ 2.75423. Denominator = 0.048 × 2.75423 = 0.132203. A = (2 / 0.132203)^(1/0.725) = (15.1283)^1.37931 ≈ 42.39 mil². For 1 oz copper, thickness = 1 × 1.378 = 1.378 mil. Width = 42.39 / 1.378 ≈ 30.76 mil. Width in mm = 30.76 × 0.0254 ≈ 0.7814 mm."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/pcb-trace-width-calculator-ipc-2221/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/pcb-trace-width-calculator-ipc-2221/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/pcb-trace-width-calculator-ipc-2221/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`