Both the PDFN and the DPAK move heat through an exposed pad into the board, but they serve different current classes and pay different board costs. This guide compares the thermal numbers, the layout cost, and the assembly, and says when each package wins.
Leadless Packages Move Heat Through the Pad
The PDFN is a leadless package whose exposed bottom pad is the thermal exit, and the DPAK is a lead-frame package with a large tab that becomes an exposed pad. Both turn the PCB into the heatsink, and both depend on the board’s copper and vias—the difference is the scale: the DPAK’s larger tab needs more copper for a higher current class, and the PDFN’s smaller pad fits a more compact board.
The thermal philosophy is identical; the board contract is not. A PDFN on a proper pad and via grid performs like a small power package, and a DPAK on a starved board behaves like a bigger version of the same mistake.
The pad geometry also differs in the details: the PDFN’s pad is roughly the size of the die footprint, while the DPAK’s tab is a large exposed area that dominates the package’s bottom. The board design scales accordingly—the PDFN’s via grid fits a compact area, and the DPAK’s grid spreads across a larger pad with more vias and more copper.
The difference shows in the current the board must carry: the DPAK’s leads and tab carry 30 A class currents, so the copper width and the via count follow that current; the PDFN’s 10 A class needs a smaller but still deliberate board investment. The board cost and the current class move together.
Comparing RthJC: PDFN56 vs DPAK Numbers
| Package | Example part | RθJC | Typical class |
|---|---|---|---|
| PDFN56 | AMBRP10H100 | 3.0 °C/W | 10 A |
| DPAK (D2PAK) | AMBRB3045CT / AMBRB30200CT | 2.0 °C/W | 30 A |
The datasheet numbers are verified: the PDFN56 at 3.0 °C/W and the D2PAK at 2.0 °C/W. The difference reflects the larger die and tab of the D2PAK, and it is meaningful at the current each class serves—the D2PAK’s lower resistance is what lets it carry 30 A, and the PDFN’s higher resistance is acceptable at 10 A because the die is smaller.
The RthJC comparison also has a mounting caveat: both figures assume the pad is doing its job, and the real junction temperature depends on the board’s copper and vias. Two boards with the same package can differ by tens of degrees, which is why the comparison ends at the temperature measurement, not at the datasheet column.
Layout Cost: Vias, Copper, Solderability
The board cost follows the package: the PDFN needs a pad matched to its exposed area, a via grid, and controlled stencil apertures, on a small footprint; the DPAK needs a larger pad, a denser via grid, and more copper to carry 30 A. On a dense board the PDFN’s smaller footprint wins; on a power board with copper to spare, the DPAK’s lower RthJC wins.
The solderability also differs: the DPAK’s larger tab is easier to inspect with X-ray, while the PDFN’s smaller pad is more sensitive to stencil and void control. The assembly capability is part of the comparison.
The stencil design follows the pad size: the PDFN’s stencil opens a pattern of small apertures over its pad, and the DPAK’s opens a larger pattern with the same purpose—controlling solder volume and letting gas escape. The reflow profile is tuned for the largest package on the board, and the moisture handling follows the MSL class of each part.
Assembly and Inspection Considerations
Both packages hide their joints under the body, so X-ray is the inspection tool, and both follow the lead-free rules with the peak inside the package limit. The PDFN’s stencil is a pattern of small apertures to control solder volume; the DPAK’s stencil is larger but serves the same purpose. The thermal measurement at load closes the inspection for both.
The inspection acceptance also feeds the reliability story: a consistent void percentage and a stable case temperature across lots are the evidence that the thermal design survives production, and the same data the reliability review reads comes from the first-build and periodic samples.
When Each Package Wins
| Situation | Winner |
|---|---|
| Dense board, 5–10 A | PDFN |
| 20–40 A with board copper available | DPAK |
| Sealed compact module | PDFN |
| Power board with a thermal budget at 30 A | DPAK |
| Footprint-constrained automotive board | PDFN |
The table is the conclusion: the PDFN wins where the footprint and the current class are small, and the DPAK wins where the current demands the lower thermal resistance and the board can provide the copper.
The conclusion also has a migration angle: a design that outgrows the PDFN’s 10 A class moves to the DPAK, and the board’s copper budget grows with it; a design that shrinks the other way moves to the PDFN and frees the board. The two packages are rungs on the same board-level ladder.
The comparison also closes with the production angle: the PDFN’s smaller pad is more sensitive to the stencil and reflow process, while the DPAK’s larger tab is more forgiving but needs more copper and inspection. A plant’s existing process capability is part of the package decision, and the first-build X-ray and temperature data confirm the choice on the actual line.
The final word belongs to the measurement: the case temperature at the working current and ambient, taken on the assembled board, is the number that decides between the two packages. The datasheet columns start the comparison, and the thermocouple ends it.
The comparison also includes the current-class upgrade path: a 10 A PDFN design that grows to 20 A evaluates the DPAK, and the migration’s cost is the copper and the footprint change. The decision is revisited at each current class, because the package that won at 10 A is not automatically the winner at 30 A.
The production-volume angle closes the comparison: a high-volume design pays the board cost per unit, so the PDFN’s smaller copper budget compounds at scale, while a low-volume power board can afford the DPAK’s copper. The volume is part of the package math, read alongside the thermal numbers.
The reliability angle adds the final filter: the exposed-pad solder joint is the fatigue point in thermal cycling for both packages, and the larger DPAK joint and the smaller PDFN joint each have their own inspection and life data. The cycling article owns the method; the package comparison reads the joint data as part of the choice.
The package comparison also reads the assembly line’s capability: a plant experienced with large exposed pads handles the DPAK naturally, while a plant tuned for fine-pitch SMD prefers the PDFN, and the process data—first-pass yield, void rates, inspection throughput—is part of the decision. The engineering comparison and the manufacturing comparison land on the same table.
The final filter is the application’s thermal reality: a sealed 10 A module with no airflow is a PDFN design, and a ventilated 30 A power stage with copper to spare is a DPAK design. The two packages win where their heat paths match the enclosure, and the temperature measurement on the prototype is the tie-breaker that neither datasheet column can be.
Engineering note. The RthJC figures are datasheet-published for the AMBRP10H100 and the AMBRB D2PAK parts; the layout-cost and assembly comparisons are engineering guidance, and the final choice is confirmed with the case-temperature measurement at the working current and ambient.
Frequently Asked Questions
Which package has the lower thermal resistance?
The D2PAK, at 2.0 °C/W versus the PDFN56’s 3.0 °C/W—but the difference matters at the current each class serves, and the board copper must be there to use it.
Does the PDFN cool well enough for 10 A?
Yes, with a proper pad and via grid. The 3.0 °C/W path plus the board copper keeps a 10 A die within its envelope.
Why does the DPAK need more board copper?
Its 30 A class dissipates more heat, and the larger tab needs the copper and vias to move it. A starved DPAK behaves like a smaller package.
How do I inspect the joints?
With X-ray for voids and bridging, plus a thermal measurement at load. Both packages hide their joints under the body.
When should I choose the PDFN?
On dense, footprint-constrained boards at 5–10 A; the DPAK wins at 20–40 A where the board can provide the copper.
Conclusion
PDFN and DPAK share the exposed-pad philosophy and differ in scale: the PDFN wins the dense, low-current board, and the DPAK wins the high-current board with copper to spare. Compare the RthJC at the working class, price the board copper, and let the temperature measurement decide.
Compare the AMBRP10H100 and the AMBRB3045CT product pages on the Good-Ark site, and contact Good-Ark with your current class and board design for a package recommendation.