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fix(to220): standard 2.54mm lead pitch and KiCad TO-220-3 pads #791

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fix(to220): standard 2.54mm lead pitch and KiCad TO-220-3 pads #791

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b4ef69d
fix(to220): standard 2.54mm lead pitch and KiCad TO-220-3 pads
zkasuran Aug 8, 2026
db11e19
test(to220): add KiCad TO-220-4 parity test
zkasuran Aug 8, 2026
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56 changes: 38 additions & 18 deletions src/fn/to220.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -4,16 +4,21 @@ import {
type PcbSilkscreenPath,
length,
} from "circuit-json"
import { platedhole } from "src/helpers/platedhole"
import { mm } from "@tscircuit/mm"
import { platedHolePill } from "src/helpers/platedHolePill"
import { platedHoleWithRectPad } from "src/helpers/platedHoleWithRectPad"
import { z } from "zod"
import { type SilkscreenRef, silkscreenRef } from "../helpers/silkscreenRef"
import { base_def } from "../helpers/zod/base_def"

export const to220_def = base_def.extend({
fn: z.string(),
p: length.optional().default("5.0mm"),
id: length.optional().default("1.0mm"),
od: length.optional().default("1.9mm"),
// JEDEC TO-220 lead pitch is a fixed 0.1" (2.54mm), the same value the
// to220f sibling and KiCad TO-220-3_Vertical use.
p: length.optional().default("2.54mm"),
id: length.optional().default("1.1mm"),
od: length.optional().default("1.905mm"),
ph: length.optional().default("2mm"),
w: length.optional().default("13mm"),
h: length.optional().default("7mm"),
num_pins: z.number().optional(),
Expand All @@ -26,7 +31,7 @@ export const to220 = (
raw_params: To220Def,
): { circuitJson: AnyCircuitElement[]; parameters: any } => {
const parameters = to220_def.parse(raw_params)
const { id, od, w, h, string } = parameters
const { p, id, od, ph, w, h, string } = parameters

const numPins =
parameters.num_pins ??
Expand All @@ -36,17 +41,29 @@ export const to220 = (
const halfWidth = w / 2
const halfHeight = h / 2

const minPitch = 2.5
const maxHoleWidth = w * 0.4
const computedPitch = Math.max(minPitch, maxHoleWidth / (numPins - 1))

const plated_holes = Array.from({ length: numPins }, (_, i) => {
const x =
numPins % 2 === 0
? (i - numPins / 2 + 0.5) * computedPitch
: (i - Math.floor(numPins / 2)) * computedPitch
return platedhole(i + 1, x, holeY, id, od)
})
// Pins sit on the fixed 2.54mm pitch, not a value derived from the body
// width. Pin 1 gets a rectangular pad (polarity marker) and the rest are
// pill pads, mirroring KiCad's TO-220-3_Vertical land pattern.
const plated_holes: AnyCircuitElement[] = Array.from(
{ length: numPins },
(_, i) => {
const x =
numPins % 2 === 0
? (i - numPins / 2 + 0.5) * p
: (i - Math.floor(numPins / 2)) * p
if (i === 0) {
return platedHoleWithRectPad({
pn: 1,
x,
y: holeY,
holeDiameter: id,
rectPadWidth: od,
rectPadHeight: ph,
})
}
return platedHolePill(i + 1, x, holeY, mm(id), mm(od), mm(ph))
},
)

const silkscreenBody: PcbSilkscreenPath = {
type: "pcb_silkscreen_path",
Expand Down Expand Up @@ -103,7 +120,10 @@ export const to220 = (

const silkscreenRefText: SilkscreenRef = silkscreenRef(0, h / 2 + 0.6, 0.5)
const pinToeHalfSpanX =
Math.max(...plated_holes.map((hole) => Math.abs(hole.x))) + od / 2
Math.max(
...plated_holes.map((hole) => Math.abs((hole as { x: number }).x)),
) +
od / 2
const pinToeTopY = holeY + od / 2
const pinToeBottomY = holeY - od / 2
const courtyardHalfWidth = Math.max(
Expand Down Expand Up @@ -135,6 +155,6 @@ export const to220 = (
silkscreenRefText as AnyCircuitElement,
courtyard,
],
parameters: { ...parameters, p: computedPitch },
parameters: { ...parameters, p },
}
}
2 changes: 1 addition & 1 deletion tests/__snapshots__/to220_2.snap.svg
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@techmannih techmannih Aug 8, 2026

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Please add KiCad tests for the footprints you changed.

@zkasuran zkasuran Aug 8, 2026

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Added tests/kicad-parity/to220_4_kicad_parity.test.ts in db11e19, matching the to220_3 parity that was already in the PR. Against Package_TO_SOT_THT.pretty/TO-220-4_Vertical the copper matches KiCad exactly (avgRelDiff 0.00%) with courtyardDiffPercent 11.77%, the same residual body-outline delta as to220_3, so it reuses the same < 13 courtyard threshold and ships the SVG plus boolean-difference snapshots.

That gives KiCad parity for both fixed 2.54mm-grid variants (to220_3 and to220_4). I deliberately did not add parity for the other two changed footprints, because their KiCad references are not on a 2.54mm pitch and a passing assertion there would need a threshold that certifies nothing:

  • TO-220-2_Vertical is a 5.08mm land (the two outer leads of the frame), so the fixed 2.54mm part measures avgRelDiff 29.40% / courtyardDiffPercent 17.15% against it.
  • TO-220-5_Vertical is the 1.7mm Multiwatt land, so 2.54mm measures avgRelDiff 36.03% / courtyardDiffPercent 24.30%.

Both keep their render snapshots in tests/to220.test.ts. If you want real KiCad parity across every pin count I can follow up with a per-pin-count pitch (5.08mm for the 2-pin, 1.7mm for the 5-pin) so to220_2 and to220_5 land on their KiCad packages too. That is wider than #790, which is why I scoped this PR to the 2.54mm land. Happy to fold it in here or open a separate PR, your call.

bun test on the to220 files is green (9 pass) and bun run build succeeds.

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2 changes: 1 addition & 1 deletion tests/__snapshots__/to220_3.snap.svg
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