Thermal Performance of MOSFETs

Thread Starter

mohtishamali

Joined Jul 9, 2021
55
God Day,

I am new in the field of power electronics and I would like to ask few very basic questions to learn something new from you. I have already read a lot on web about these questions but i would like to have a relatively simpler answer to these questions for my better understanding. My questions are:
What is difference between top side and bottom size cooling? For high power application , I have read that top sided cooling is preferred. Why is that?
Why SMD packages have better thermal performance as compared to through hole packages?
What are thermal via's on PCB and why it is important to connect thermal pads to these via's on PCB.
I will look forward to hear your valuable feedback.
Thanks
 

ronsimpson

Joined Oct 7, 2019
2,527
MOSFETs do not like to run hot.
Through hole parts can be bolted to a heatsink.
Most SMD do not have an option for adding a heatsink.
The PCB, coper carries away heat. It is best if coper in all layers moves the heat away.
Vias move the heat from the topside of the PCB to the bottom side. There is almost 2x better cooling with good vias.
 

dl324

Joined Mar 30, 2015
15,453
What is difference between top side and bottom size cooling? For high power application , I have read that top sided cooling is preferred. Why is that?
It would be helpful if you mentioned specific devices and packages.

If your top sided cooling comment is for SMD, some devices can't have heat sinks attached. For those devices, heat is primarily conducted away through the leads and package.
Why SMD packages have better thermal performance as compared to through hole packages?
It would be helpful if you cited some specific devices and packages.
What are thermal via's on PCB and why it is important to connect thermal pads to these via's on PCB.
Again, specific examples would generate better answers. In general, thermal vias will transfer heat to the bottom side of the board better than the board material alone.
 
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