Description

The D3PAK surface-mount power package accommodates silicon chips with dimensions up to 416 × 270 mils. Such chips, when housed in the TO-247 package, can dissipate up to 360W at a case temperature of 25°C. However, these same chips are limited to less than 7W at 25°C ambient, when housed in a D3PAK and soldered to a standard FR-4 printed circuit board (PCB). Clearly, any technique capable of boosting the D3PAK dissipation capability nearer to the TO-247 benchmark merits close attention.

This application note will compare the thermal performance of various mounting methods for the D3PAK including classic surface mount device (SMD) printed circuit board mounting; insulated metal substrate (IMS) mount down, with and without an attached heat sink; oven-fired ceramic substrate, with and without heat sink; and direct bonded copper (DBC) substrates, with and without heat sink.

The importance of optimized bonding will be explored, independent of the actual substrate used, covering choice of appropriate solder alloys and fluxes, as well as the layout of the interface metallization patterns to preclude voiding during reflow operations.

Finally, a relative cost versus performance evaluation will be presented on the various methods described in the paper.