Heatsink Preparation

dhole

Member
2004-07-26 11:49 pm
Brighton
Hi There people

Still got the mumps..... but It keeps me behind the soldering iron.
So Ive got one channel of aleph 5 nearly ready. Its time to prepare the heatsinks for use.

The sinks are used (pulled out of a radio transmitter. There were devices attached but not quite in the right places. I will need to drill some holes and prepare the surfaces. The surface is quite smooth as I say they have had stuff mounted before. What sort of steps shuld I take to prepare the best finish ?
The sinks are aluminium (or aluminum?! I cant spell but Im not disleksik) I presume there is some sort of buffing compound and a special buffer material made from behind ear hair of female shrew. Could anyone advise please.
regards
dave
 
Sorry about the Mumps!

THe basic idea is that the better the contact patch between the heatsink and the device that warms up the better the cooling capability. So keeping that in mind I would give it a good sanding backed by a block of something that will give youa good flat surface. To start off with 1200 grit would be rather fun. More like a government makework project. Term to last 2 years to indefinite. No siree. I'd start out at 220 ( wet and dry paper ) and flaten with a bit of soapy water as a lubricant. If you want to go to 400 and up go for it. But you are really only cutting down the bumps made by drilling the new holes not getting it ready for a paint job!

Mark
 
Hi,
ensure all the little craters surrounding inevitable dings are removed.
Countersink all your tapped holes.
These steps are to ensure that the transistors are tight up against the heatsink and not sitting on top of all those mountain sized ripples, burrs, swarf etc.
You could try gluing the wet or dry to a flat surface (glass?) & then rubbing the heatsink on that. If you are really adventurous (no other life) try flatting the semis as well.