coolingheatthermal
I'm in final step of a project an I need some advice about what heat evacuation profile should I use to place three fans for cooling, I have four alternatives as shown in the diagram but I don't know which will achieve the best performance in terms of cooling.
Just a fan blowing over the PCB won't be sufficient; a TO-263 doesn't have good thermal contact with the air surrounding it. I would solder this
heatsink over the FET. Like I said in another answer earlier today an SMD loses much more heat through conduction than through convection, but the heatsink has better convection loss thanks to its larger surface. The heatsink mounts over the SMD, not on it.
Heat transfer will occur via the PCB's copper, so increase the TO-263's pad so that the heatsink shares it.
Wikipedia: "The glass bulb of a general service lamp can reach temperatures between 200 and 260 °C (392 and 500 °F). Lamps intended for high power operation or used for heating purposes will have envelopes made of hard glass or fused quartz."
Assuming the glass reach those temperature ranges, the metal should be near that too.
Best Answer
That depends on what the "best performance" is, and in any case the exact answer would require a calculation for which many inputs are unknown.
Empirically, you'll want to remove the air right after it passes over hotter components, and blowing work better than sucking because of air turbulence which favors heat exchange. So the typical arrangement (which I've seen in every laptop I have opened) looks like this: