The TO-3P package is a three-lead plastic power package on a 5.45 mm lead pitch, with an exposed metal tab and a single ø3.2 mm mounting hole. Toshiba originated it, and Toshiba still defines it — there is no single JEDEC outline behind the name.

That matters because “TO-3P” covers at least three different envelopes. Below are the variants, the dimensions, and the torque window that keeps the package from deforming.

[IMAGE 1: side-by-side photograph of a TO-3P(L), a TO-3P(N) and a TO-220 on graph paper, tabs facing the camera | alt: “TO-3P package variants TO-3P(L) and TO-3P(N) compared with a TO-220”]

Key takeaways

• TO-3P is a vendor name. Toshiba’s 2SC5200 datasheet prints “―” against both JEDEC and JEITA.
• TO-3P(N) is registered — as JEITA SC-65. TO-3P(L) is not.
• The mounting hole is 3.2 mm, which will not take a 6-32 screw. Use M3.
• Measured minimum thermal resistance sits at 4 to 6 kgf·cm of torque; past that the package deforms and Rθjc rises again.
• The same 230 V / 15 A / 150 W die ships in both the large and small body. Package size does not track the headline rating.

TO-3P is a Toshiba package name, not a registered outline

Check Toshiba’s own datasheet for the 2SC5200, revision dated 2016-01-07. In the package block it lists JEDEC ―, JEITA ―, TOSHIBA 2-21F1A. Both industry registration fields are empty. The only authoritative identifier is Toshiba’s internal code.

The smaller variant is different. Toshiba’s package record for TO-3P(N) gives Toshiba code 2-16C1S and JEITA SC-65. So one variant carries a standards-body designation and the other does not.

Analog Devices sidesteps the problem by labelling its equivalent outline “3-Lead Plastic TO-3P (Similar to TO-247)” on drawing 05-08-1450 Rev A. That phrasing is doing real work: similar, not identical, and not interchangeable without checking the drawing.

The practical consequence is that a part marked TO-3P from one vendor is not guaranteed to match another vendor’s TO-3P. Diodes Incorporated publishes its own TO3P outline with an independent min/max table. Compare drawings, not names.

TO-3P package dimensions by variant

These envelopes come from Toshiba’s package records and from distributor listings for specific Toshiba devices.

Variant	Toshiba code	Registration	Width × Length × Height (mm)	Packing
TO-3P(L)	2-21F1S	None listed	20.0 × 26.0 × 5.0	Tray, 100 pcs
TO-3P(N)	2-16C1S	JEITA SC-65	15.5 × 20.0 × 4.5	Tube 25 / tray 100
TO-3PNIS (isolated)	—	—	15.8 × 21 × 5.0	—

The large body is roughly twice the footprint area of the small one. Height differs by only 0.5 mm, so a design that clears one usually clears the other vertically — the problem is board area and the mounting hole position, not headroom.

Mass follows size. Toshiba specifies 9.75 g typical for the 2SC5200 in TO-3P(L). For vibration-qualified assemblies that is a meaningful cantilever load on three leads if the tab is not bolted down.

Toshiba publishes STEP models for these packages and reference land patterns drawn to JEITA ET-7501 Level 3, which is the closest thing to a normative footprint you will find for TO-3P.

Mounting a TO-3P: one M3 screw, and a torque window

The tab has a single hole, nominally ø3.20 ±0.10 mm on the published outline. That is the first trap. A 6-32 screw is 3.5 mm across the threads and will not pass. Designers working in inch-standard shops routinely discover this only after tapping the heatsink.

Use an M3 screw. If the heatsink is already drilled and tapped 6-32, the options are to open out the tab hole, to use a clamp bar across the plastic body instead of a through-screw, or to redrill the sink.

Torque is the second trap, and onsemi has measured it. In AND9859/D, the minimum junction-to-case thermal resistance for TO3P and TO220 packages occurs at 4 to 6 kgf·cm. Beyond that range Rθjc rises again, which onsemi attributes to deformation of the package. Testing found no package cracking, no electrical failure, and no change in die delamination up to 7 kgf·cm, which the note treats as the ceiling.

Torque	Effect
Below 4 kgf·cm	Interface not fully closed; Rθjc higher than optimum
4–6 kgf·cm	Measured minimum Rθjc
6–7 kgf·cm	Rθjc rising again from package deformation
Above 7 kgf·cm	Beyond the tested ceiling

[IMAGE 2: exploded view of a TO-3P mounted to a heatsink — M3 screw, washer, insulating bushing, tab, thermal pad, heatsink | alt: “TO-3P package mounting stack with M3 screw, insulating bushing and thermal pad”]

Two further points. The tab is electrically live, normally tied to the collector or drain, so an isolating pad and shoulder bushing are needed against a grounded sink — or specify the isolated TO-3PNIS variant and skip the hardware. And because there is only one screw, the package pivots about it: the far end of the tab lifts under torque unless the sink is flat.

Same die, two bodies

Toshiba’s audio pair makes the point cleanly. The 2SC5200 ships in TO-3P(L); the 2SC5200N ships in TO-3P(N).

Parameter	2SC5200 — TO-3P(L)	2SC5200N — TO-3P(N)
VCEO	230 V	230 V
IC	15 A	15 A
PC at Tc = 25 °C	150 W	150 W
fT	30 MHz	30 MHz
Tj max	150 °C	150 °C
Body envelope	20.0 × 26.0 × 5.0 mm	15.5 × 20.0 × 4.5 mm

Identical headline ratings in bodies of very different size. Do not infer capability from the package footprint, and do not assume a TO-3P(N) part is the lesser device because the can is smaller.

Note also what the datasheet does not give: there is no explicit Rθ(j-c) line. You derive it from the ratings. With Tj = 150 °C, Tc = 25 °C and PC = 150 W, Rθ(j-c) works out to 0.83 °C/W.

Worked example: what a board-mount heatsink actually supports

The 150 W figure assumes the case is held at 25 °C. No real heatsink does that. Work the actual budget instead.

Take a 2SC5200 on a board-mount vertical extrusion — Aavid lists one at 7 °C/W for TO3P, TO-218 and TO-220 packages. Ambient 45 °C. Budget the junction to 110 °C rather than the rated 150 °C, leaving a 65 °C rise.

Stack the path: 0.83 °C/W junction-to-case, roughly 0.5 °C/W for a greased non-isolated interface, and 7 °C/W sink-to-ambient. Total 8.33 °C/W.

Allowable dissipation is 65 / 8.33 = 7.8 W.

That is the honest number for a PCB-mounted sink: under 8 W, against a 150 W headline. Reaching even 40 W needs the whole stack down near 1.6 °C/W, which means a chassis-sized extrusion or forced air. Size the heatsink to the dissipation, then check the current rating — never the reverse.

Five mounting mistakes

Assuming 6-32 fits. The hole is 3.2 mm. Specify M3 at the drawing stage, before the heatsink is machined.

Torquing by feel. Past about 6 kgf·cm you are making the thermal path worse, not better, and the damage is invisible.

Trusting the tab to be isolated. On a standard TO-3P the tab is the collector or drain. Only the TO-3PNIS variant is internally isolated.

Ignoring the single-screw pivot. One fastener plus an out-of-flat sink lifts the far end of the tab off the surface, exactly where the die sits.

Substituting on package name alone. TO-3P(L) and TO-3P(N) have different footprints, and different vendors’ TO-3P drawings do not match. Check the outline drawing for the specific orderable part.

Frequently asked questions

Is TO-3P the same as TO-247?

Not identical. Analog Devices describes its TO-3P outline as “similar to TO-247,” and both share a 5.45 mm lead pitch, but the body dimensions differ between vendors and between TO-3P variants. Treat them as mechanically comparable, not drop-in, and compare the two outline drawings before committing a footprint.

What is the difference between TO-3P and TO-3PN?

Size and registration. TO-3P(L) measures 20.0 × 26.0 × 5.0 mm with Toshiba code 2-21F1S and no listed JEITA or JEDEC designation. TO-3P(N) measures 15.5 × 20.0 × 4.5 mm, carries Toshiba code 2-16C1S, and is registered as JEITA SC-65. Electrical ratings can be identical across both.

What size screw does a TO-3P use?

M3. The published mounting hole is ø3.20 ±0.10 mm, which is too small for a 6-32 screw. Recommended torque is 4 to 6 kgf·cm, where onsemi measured minimum junction-to-case thermal resistance; 7 kgf·cm is the tested upper limit before deformation concerns.

What transistors come in a TO-3P package?

Toshiba’s 2SC5200 and complementary 2SA1943 audio output pair use TO-3P(L), and their TTC5200 and TTA1943 successors use the same body. Toshiba IGBTs such as the GT30J341 and DTMOS-series MOSFETs use TO-3P and TO-3P(N). Second sources including Diodes Incorporated publish their own TO-3P outlines.

What to do next

If you are laying out an existing TO-3P part, pull the outline drawing for that exact orderable number rather than a generic TO-3P footprint, and design the mounting for an M3 screw at 4 to 6 kgf·cm. If the heatsink is a shared inch-standard part, resolve the fastener conflict on paper before anything is machined.

If you are choosing a package for a new design, TO-3P is a reasonable pick where you need a one-screw through-hole power package and the die is offered in it. Where footprint standardisation across vendors matters more, a JEDEC-registered TO-247 outline removes the ambiguity that “TO-3P” carries.

External references

• Toshiba TO-3P(N) package data
• Toshiba TO-3P(L) package data
• Toshiba 2SC5200 datasheet, 2016-01-07
• Analog Devices 3-lead plastic TO-3P outline, LTC DWG 05-08-1450 Rev A
• Diodes Incorporated TO3P package outline

Proposed internal links

• [INTERNAL LINK: TO-247 package → TO-247 package dimensions and mounting]
• [INTERNAL LINK: TO-220 package → TO-220 package guide]
• [INTERNAL LINK: junction-to-case thermal resistance → thermal resistance fundamentals for power design]
• [INTERNAL LINK: heatsink selection → heatsink sizing for through-hole power devices]
• [INTERNAL LINK: package registration → JEDEC, JEITA and vendor package naming explained]