DPAK TO-252 Footprint: Thermal Layout, DFM, and Assembly

DPAK / TO-252 is a power package package used for surface mount assembly, also seen labeled TO-252, DPAK, SC-63 variants. A dependable footprint follows the exact orderable-device drawing rather than the family name: nominal body About 6.5 × 6.1 mm excluding leads, overall span Often about 10 mm including leads, seated height Typically 2.2–2.5 mm, pitch About 2.28 mm between lead positions, pin count 2 or 3 leads plus large tab; center lead may be cropped, and exposed pad Large rear tab, electrically active.

Use the exact TO-252 lead option, tab dimensions, and manufacturer thermal board; cropped-center variants still need correct pad numbering.

Typical uses include MOSFETs, linear regulators, power diodes. TO-252/DPAK has lead-option and body variants; exact tab, pin, and thermal data come from the selected device.

• The broad tab carries most heat and often the MOSFET drain or regulator output, while two or three smaller leads establish the control and return pins.
• The large tab or thermal pad is commonly an electrical terminal as well as the main heat path; its net and land geometry come from the exact device drawing.

Route load current broadly through the tab and source/output pins, keep gate or feedback loops short, and spread heat into an intentional copper/via structure.

• Size copper and thermal vias from loss and temperature-rise calculations, keep current paths broad, and isolate heat-sensitive feedback or timing parts from the hot region.

Hand assembly is rated hard. Preheated board and reflow; high-power iron or hot air for rework. Watch for cold tab joint, solder voiding, and assuming drain/output tab identity.

• Segment tab paste, specify via fill or tenting, check copper-weight etch, and prevent solder starvation through open thermal vias.
• Large thermal lands often need segmented paste and a controlled via-fill strategy to avoid solder loss, floating, or excessive voiding.
• Verify copper weight, thermal relief policy, stencil thickness, and secondary-side mass limits with the chosen assembly process.

Inspection focus:

• Inspect visible leads, X-ray the tab when voiding matters, and measure voltage drop and case temperature at worst-case current.
• Inspect accessible leads, then use X-ray, electrical loading, and temperature measurements as appropriate because the most important thermal joint may be hidden.

Common mistakes:

• Connecting a DPAK tab to ground because another regulator used that convention can create a direct high-current short.
• Do not connect the tab by package habit; regulator outputs, transistor drains, and grounds can all occupy the large terminal in related outlines.

1. Before approving DPAK / TO-252, compare the exact orderable-device drawing with the library item: body range (About 6.5 × 6.1 mm excluding leads), terminal or lead span (Often about 10 mm including leads), pitch (About 2.28 mm between lead positions), pin count (2 or 3 leads plus large tab; center lead may be cropped), height (Typically 2.2–2.5 mm), and exposed-pad definition (Large rear tab, electrically active). Record the source drawing revision and every intentional courtyard, toe, heel, side, mask, or paste adjustment.
2. Treat the hard hand-solder rating as a prototype-planning input, not proof of production yield. Review cold tab joint, solder voiding, and assuming drain/output tab identity with the assembler, confirm that preheated board and reflow; high-power iron or hot air for rework is compatible with the build, and require the S1 connectivity gate plus relevant S2 geometry checks to pass against the released footprint and selected fabrication profile.

Manufacturing gate checks:

1. S1Pad count, numbering, and schematic parity. Tab net, cropped-lead numbering, copper necks, via process, clearances, and thermal assumptions are release-critical.
2. S1Thermal-pad net, vias, and copper necks. A wrong tab net is a short; an inadequate or paste-draining thermal land can also invalidate the device's power rating.
3. S2Courtyard and body clearance. The body, leads, placement tolerance, rework access, and nearby height limits all belong in the manufacturing review.