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Originally Posted by Voodoochile
Epoxy a penny to the tab if you can't find a clip-on sink...
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I was (and am) dubious about this.
A heat sink only helps to the extent that it improves heat transfer from the heat source to another medium belonging to someone else, thereby making it Not Our Problem. The room's air is a popular choice among engineers, because the engineer doesn't pay the A/C bill.
For passive heat sinks, the only way to improve heat transfer is to add surface area. So the question is, how much does a penny change the surface area of a TO-220 part? Considering just the metal parts (the plastic doesn't conduct heat well enough to matter), very roughly speaking, it doubles the surface area. Now, you get full benefit of that
only if there is no thermal resistance between the penny and the IC. That isn't going to happen, so I suspect most of the benefit is wiped out, especially if you use something with poor thermal conductivity like epoxy.
You know, if you have a hot enough iron, you could literally solder a penny to a TO-220's tab. That would probably save this idea.
Needless to say, a penny's worse than useless for any bigger package.