Here’s an interesting little article about the consequences of clogged cooling (heatsink) fins.
A heatsink (area extender) is fine if it’s working as intended. That is that its extended surface area is well ventilated such that the beneficial effects of the large surface area outweigh the fact that you’ve stuck a large solid obstruction on something that’s hot. If the fin surfaces suffer particulate build-up, especially to the extent whereby the air flow channels between the fins fill up, then all you’ve done is to do a better job of insulating the hot object you’re trying to cool. You’re now worse off than having no heatsinking fins at all.
Check out the discussion thread on John Parry’s recent blog entry which is relevant to this issue as well.
22nd July Nottingham