# TO package (through-hole)

A through-hole transistor, regulator or diode package standing on the board, built from the maker's package drawing. These are the JEDEC outlines that every maker builds:

| `package` | Leads | Body (W x thickness x height) | Source |
|---|---|---|---|
| `TO-220AB` | 3, 2.54 pitch | 10.16 x 4.45 x 15.09 (tab included) | Vishay Siliconix 92506 |
| `TO-220AC` | 2, 5.08 apart | 10.31 x 4.45 x 15.05 (tab included) | Vishay Semiconductors 95221 |
| `TO-247AC` | 3, 5.46 pitch | 15.70 x 5.02 x 20.55 | Vishay Siliconix 91360 |
| `TO-92` | 3 straight, 1.27 pitch | 4.83 x 3.68 x 4.83 | TI LP0003A |
| `TO-18` | 3, on a Ø 2.54 circle | flange Ø 5.58, can Ø 4.74, 4.83 high | Central Semiconductor TO-18 |
| `TO-18-2` | 2, 2.54 apart | as `TO-18` | Central Semiconductor TO-18 2-Lead |

Lead 1 is at the origin and the leads run along +X. The moulded front faces -Y (on the TO-92, the flat face), and the metal tab or exposed copper is at the back (+Y).

- **TO-220 and TO-247.** The leads' shoulders rest on the board (the XY plane), and the leads continue their full length L down through it.
- **TO-92.** The body sits 1.5 above the board (TI's reference seating plane).
- **TO-18.** The flange sits on the board. Leads 1 and 3 are 2.54 apart along +X, and lead 2 is 1.27 off that line along -Y. The tab is at 45°, beside lead 1.

`detail = "simple"` leaves out the leads.

## Source

Each table gives a minimum and a maximum. The part uses the middle of the two, except where noted. `part.py` holds every table as read.

- **Vishay Siliconix, "TO-220AB (High Voltage)"**, Package Information, document 92506, revision 30-Sep-2024 (DWG 6031), from vishay.com.
  - Page 1, drawing: front, side and back views and section F-F.
  - Page 2, table (mm): A 4.25–4.65, A1 1.20–1.34, A2 2.563–2.92, b 0.71–0.91, b2 1.14–1.78, c 0.46–0.61, D 14.32–15.86, D1 8.39–8.79, D2 12.20–12.80, E 9.96–10.36, E1 8.14–8.74, E2 0.59–0.69, e 2.54, e1 5.08, H1 6.30–6.70, L 13.40–14.40, L1 3.65–4.05, ØP 3.60–3.80, Q 2.54–2.94.
- **Vishay Semiconductors, "TO-220AC"**, Outline Dimensions, document 95221, revision 16-Jan-2026, from vishay.com. The drawing and table use the same letters. Here e1 is 4.88–5.28, the spacing of the two leads, and E2 is 0.76 max. The outline conforms to JEDEC TO-220AC.
- **Vishay Siliconix, "TO-247AC (High Voltage)"**, Package Information, document 91360, revision 07-Sep-2026, from vishay.com. The part uses version 1 (facility code 9) with its nominal values:
  - A 5.02, A1 2.41, A2 1.27, b 1.20, b2 2.00, b4 3.00, c 0.50, D 20.55, D1 16.76, D2 0.66, E 15.70, E1 14.02, E2 4.91, e 5.46, L 15.15, L1 4.06, ØP 3.61, ØP1 7.19 (ref), Q 5.50.
  - The package reference is JEDEC TO-247, variation AC.
- **Texas Instruments, LP0003A "TO-92 - 5.34 mm max height"**, drawing 4215214/C 04/2025 (ti.com/lit/pdf/msot002), straight lead option, page 1:
  - body 4.44–5.21 wide, 4.32–5.34 high and 3.17–4.19 deep;
  - the round back 2.03–2.67 from the leads, and the flat face at least 3.43 wide;
  - leads 0.38–0.55 x 0.35–0.43, at 1.27 ±0.13 pitch, 12.7 min long;
  - the seating plane (1.5) typical below the body;
  - reference JEDEC TO-226, variation AA.
- **Central Semiconductor, "Package Details - TO-18"** (REV R1, R0 21-June 2004) and **"TO-18 2-Lead Case"** (REV R0, 13-March 2013), from centralsemi.com.
  - Table (mm): A flange Ø 5.31–5.84, B can Ø 4.52–4.95, C flange 0.76 max (used as is), D height 4.32–5.33, E lead length 12.70 min (used as is), F lead Ø 0.41–0.48, G 2.54 (the lead circle, or the 2-lead part's spacing), H 1.27 (3 leads), and tab width 0.91–1.17 and tab length 0.71–1.22 at 45° (I and J; on the 2-lead sheet, H and J).
  - Both sheets' material sheets give a Kovar header and leads and a nickel-plated iron-alloy can.

How the letters are read:

- **TO-220 and TO-247.** A2 (TO-247: A1) runs from the leads' back face to the back of the package. The leads' shoulders (b2, b4) are L1 long. On the TO-220, the metal tab is A1 thick: E wide above the moulding (H1 = D - D1), and E1 wide down the back to D2 below the top. On the TO-247, the exposed copper (D1 x E1, from D2 below the top) is taken as A2 thick, the dimension drawn at the back face. The TO-247's side slots are Ø E2, at Q below the top, the same height as the hole.
- **TO-92.** The body is a round of Ø W, cut flat at the depth T, with the leads K in front of the round back.
- **TO-18.** The tab length J is read as reaching beyond the flange's edge.

**Proportions, for looks only.** The drawings show these but don't dimension them:

- The TO-220 tab's side notches, E2 deep, are 1.4 high, from 1.4 to 2.8 below the top, as drawn.
- Not modelled: the TO-220AC's cut-off middle lead, the TO-220's ejector dimple, the TO-247's copper ring ØP1, and the bodies' 5° draft and small radii.
- Every lead's shoulder narrows to the lead in one step.
- Materials are for looks and a rough mass:
  - The mouldings are epoxy. Nylon (PA6) is the nearest material in the list.
  - The TO-220 tab and the TO-247 pad are copper, and the leads are tinned copper.
  - The TO-18 header and leads are Kovar (8.36), so nickel (8.9), the nearest in the list. Its can is steel.

## Catalogue models

The reference models were measured against the drawings, and each falls inside the drawing's tolerances:

- **TO-220-3_Vertical.** 10.26 wide, 4.46 thick and 15.07 high with the tab. Leads 0.86 x 0.53 with 1.46 shoulders at 2.54. The leads' back face is 2.90 from the back.
- **TO-220-2_Vertical.** The same body, with leads at 0 and 5.08.
- **TO-247-3_Vertical.** 15.90 wide (E max 15.87, so 0.03 over), 5.03 thick and 20.7 high. Leads 1.20 with shoulders 2.03 and 3.00 at 5.45.
- **TO-92 and TO-92_Inline.** 4.83 wide, 3.75 deep. Leads at 1.27, with the flat face 1.33 in front of the leads and the round back 2.42 behind them.
- **TO-18-3.** Flange Ø 5.84, can Ø 4.95 and leads Ø 0.48 (the drawing's maximums). Lead 2 is 1.27 off the line of leads 1 and 3, and the tab is at 45° beside lead 1.

The reference models stand their bodies at different heights above the board: the TO-92 at 2.5 and the TO-18 at about 5. The drawings don't give these, so this part uses the drawings' own seating.

So these map: TO-220-3_Vertical (TO-220AB), TO-220-2_Vertical (TO-220AC), TO-247-3_Vertical (TO-247AC), TO-92 and TO-92_Inline (TO-92), TO-18-3 (TO-18) and TO-18-2 (TO-18-2).

These stay "no table read yet" (`COVERAGE.md`):

- the TO-92 models with leads formed to 2.54 (`_Wide`). TI's formed leads are 2.4 to 2.9 apart, with a land pattern of 2.6.
- the horizontal (bent-lead) models. The drawings give straight leads only.
- the other packages in the family: TO-126, TO-218, TO-220F, TO-220-4/5/11, TO-251, TO-262, TO-264, TO-3, TO-3P, TO-5, TO-8, TO-11, TO-39, TO-46 and TO-52, the TO-92 variants (L, S, Mini, Flat, 2-lead), and the windowed and lensed cans.