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06.21.2006, 11:34 AM
If i had a choice i'd run stuff at a max of about 60C, but it costs too much for manufacturers to bother. It's cheaper to deal with a few failures than to put a $1 heatsink on something that will be sold by the thousand or even the million.
To keep say 12 transistors running at about 40F over ambient, if there was a total dissipation of 240W, you would need a heatsink with a thermal resistance of 0.1c/w temperature rise. Passive cooling of that efficiency is amazingly expensive (a sink that big would be enourmous)
They have to have high heat tollerances, because in an application such as a small mobile device that has to handle a lot of current (such as a brushless ESC), yet be compact and lightweight, it's not always possible to keep it small and also running cool. The total thermal resistance of a sink on a brushless controller might be 2c/w if you were lucky, so if you dissipate 40W on it, it will be 80C over ambient!
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