I'm designing a board with some MOSFETs that dissipate a fair amount of power. The best device (low Rds and low Qg) available in this scenario would run at 30W max. This is available in D2PAK and TO-220.
What is the preferred option for cooling D2PAK at those power levels? Some of the options:
SMD stamped heatsinks on the drain pad, straddling the device (like these goofy things). Aavid 7109D resistance from mounting surface to air is 2.75C/W at 400fpm and 2C/W at 800fpm, this seems marginal in this case (since the connection between heatsink and device is thin copper conducting sideways).
thermal vias under device and a big heatsink epoxied to the board on the other side (one per device, not isolated)
thermal vias under device and a big aluminum plate heatsink on the back of the whole board (isolated with a pad)
aluminum core pcb or extreme thickness copper pcb. I'm guessing this makes the boards significantly more expensive, and prototyping more difficult. A metal core board would still need to connect to a heatsink somewhere, or the board would have to be extra big to give it enough heatsinking ability.
multiple devices to reduce dissipation per device. this almost seems cheaper than a complex cooling solution.
give up on using SMD and use TO-220 where <1C/W is fairly easy :) some concern about manufacturability in this case.