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-   -   Mounting LM3875 on anodised surface (http://www.diyaudio.com/forums/chip-amps/72326-mounting-lm3875-anodised-surface.html)

alleycat 22nd January 2006 08:04 AM

Mounting LM3875 on anodised surface
 
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.

Upupa Epops 22nd January 2006 08:13 AM

Anodising make thermal transfer little bit worse, but in practical case it is free... be calm ... ;)

peranders 22nd January 2006 04:12 PM

Anodised aluminium is the normal surface for a heatsink you know.

alleycat 23rd January 2006 06:26 AM

Thank you for the reassuring replies. I asked this question because I have only seen heatsinks with anodising on the finned side and a machined surface for mounting components on the other.

Nordic 23rd January 2006 06:39 AM

Well if it bothers you... stick some sanding paper to a flat piece of glass with woodglue (so you can pull it off later) then use this as a sanding block to wear though the anodised part....

Way too much effort.

maxro 23rd January 2006 06:40 AM

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

maxro 23rd January 2006 06:41 AM

Dang simultaneous posters!

Max

peranders 23rd January 2006 07:00 AM

Quote:

Originally posted by alleycat
Thank you for the reassuring replies. I asked this question because I have only seen heatsinks with anodising on the finned side and a machined surface for mounting components on the other.
Perfect :nod: What more could you ask for?

Nordic 23rd January 2006 08:43 AM

Great minds think alike and all that...

speaker 24th January 2006 01:11 AM

Re: Mounting LM3875 on anodised surface
 
Quote:

Originally posted by alleycat
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.


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