# Heat sink not an I-beam!



## DavidDymaxion (Dec 1, 2008)

I mounted my heat sink in my car, and then put the controller on it. Hmmm, that's funny, there is about 1 mm of air under one corner of the controller that didn't use to be there. I loosened the bolts holding the heat sink, and it relaxed to its previous flat state and the controller now was flat on the heat sink. Apparently my attaching the heat sink warped it a bit. A slight shift and a washer fixed things. So despite its beefy, I-beam like appearance, a heat sink does not have the strength of an I-beam!

Next time I might do a 3-point mount of the heat sink. As 3 points define a plane, that would guarantee it would not get a torque stress that might warp it (well, OK, not guarantee it but make it much less likely or much smaller). Another option would be to rubber mount it, so the rubber compliance would lessen torque on the heat sink.


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## piotrsko (Dec 9, 2007)

Since I used to do a LOT of exotic metal forming, I am thinking you got some stress relief going on. Might want to put the heat sink in a 300 degree oven for an hour, till golden brown and delicious (just kidding).

OTOH, could be your mounts were crooked.


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## DavidDymaxion (Dec 1, 2008)

I'm sure it was a case of the mounts not being in the same plane. Controller was flat before, and flat after I loosened, put in a washer, and retightened the mounts.


piotrsko said:


> Since I used to do a LOT of exotic metal forming, I am thinking you got some stress relief going on. Might want to put the heat sink in a 300 degree oven for an hour, till golden brown and delicious (just kidding).
> 
> OTOH, could be your mounts were crooked.


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