Mounting LM3875 on anodised surface

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If you really wanted to, you could lap the contact surface of the heatsink with progressively finer grades of wet-dry paper. This will remove the anodising and, if done properly, provide a flatter, smoother surface (read better thermal transfer) for the chip. All you need is a very flat surface like a pane of glass or, better yet, a toolmaker's granite surface plate. Start with 400 grit, then 600, 800 and finally 1000. Keep the paper wet with water and hold the heatsink firmly, flat on the paper on the surface plate. Move the heatsink in a circular fashion and change your grip on the heatsink by 90 degrees every so often.

Max
 
alleycat said:
I am considering using a piece of anodised aluminium plate as a heatsink for an LM3875TF. I was wondering if the anodising will have any significant effect on thermal transfer from the chip to the heatsink.

My company makes amplifiers and use an anodized strip of aluminum as the electrical insulator between the heatsink and the output devices. Anodizing is not conductive electrically and thermally far more conductive than a silpad or mica insulator.
 
Don't count on the anodizing to act as an insulator... bad juju. The aluminum isolators you see used have special anodizing, metal and processing.

Sil Pads work great and their cheap. Good heat sinking is more about having a resilient mounting scheme... like a strong spring or clip. Thermal cycling (expansion and contraction) has more to do with poor heat transfer than than insulators and goop.

:D ;)
 
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