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In Reply to: RE: TO-220 package wattage rating ? posted by pictureguy on April 25, 2016 at 20:18:10
"regardless of the amount of HEAT, Silicon devices can only withstand so high a temperature before malfunction."
Oh. You mean like I said when I said:
"The key parameter here is die temperature."
and
"As long as you keep die temperature in specified range you are all good. If you take the die temperature above what it is rated by the manufacturer to withstand then there are no guarantees about it's reliability and it's probably going to fail."
???
I guess it IS worth repeating!
Follow Ups:
Yes, sorry to simply 'repeat'.
Die cooling is somewhat of an art.
These days, the Drain can be the TOP of the die and is secured with a copper bus which is very heat and current conductive.
I was in semiconductor manufacture for 3 decades (more?) and saw a lot of stuff come and go. the main point with computer CPU is that Geomitries shrink and heat density goes way UP.
Thus the water cooler over clockers at the front of the pack.
Too much is never enough
Indeed the newer dual sided pqfn packages are really neat, both from a thermal perspective but also electrcally. The lead inductance on those is quite low and so also very exciting.
Though in this case the op is using to220s. I've never seen to220s with the dual sided cooling .
However it gets accomplshed, more cooling is the way to lower temps.
In many cases this could be something as simple as adding a better thermal interface material between the device and heatsink.in other cases the only way to get there is through more drastic measures such as adding more heat spreading, thermal mass or making what is already there work more efficiently.
Is it OK at this point to introduce 'safe operating area' and the idea of 'derate'?
The ESP article is as good a place to start as any.
Too much is never enough
It may indeed help illustrate the complexity of the situation at hand.
It's unfortunate no info about application, assumptions or goals were ever given by OP. It would be much easier to be helpful if there were more pointed details available.
I'm afraid we may only be sending deeper hole digging support down into the rabbit hole.
It's all good. Hopefully, though I'm a complete douche to put up with sometimes, my limited experience helps turn on an occasional light bulb. I know I have learned a great deal and very thankful for the cranky SOB's I've come across on this forum.
You make an interesting point.
When asked a question about device ratings and usage and such, RARELY is enough information given.
And the OP can or COULD read some data sheets so like was compared TO like.
I'm fairly certain that buried in all the documentation is some reasonable answer.
Too much is never enough
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