aluminum heatsink anodizing
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From: Phil Allison on 18 Dec 2008 21:47 "Jamie Morken" > > Does an anodized or painted aluminum heatsink perform better thermally > than a bare aluminum heatsink for the situation of to-220 components > attached to the heatsink with sil-pads? ** When you need good heatsink performance with TO220 pack devices - avoid sil-pads entirely !!!!!! Use thin, mica insulators with a smear of white (usually zinc oxide loaded ) thermal grease each side - not only does this conduct heat much better but mica will not *compress* over time like sil-pads do and result in your mounting bolts becoming so loose you can rotate them with your fingers. This loss of crucial pressure ruins the performance of the heatsinking. That said, a black anodised heatsink radiates IR energy much better than a silvery one - so it will generally be a few degrees cooler. ..... Phil
From: Eeyore on 18 Dec 2008 22:33 Phil Allison wrote: > "Jamie Morken" > > > > Does an anodized or painted aluminum heatsink perform better thermally > > than a bare aluminum heatsink for the situation of to-220 components > > attached to the heatsink with sil-pads? > > ** When you need good heatsink performance with TO220 pack devices - avoid > sil-pads entirely !!!!!! > > Use thin, mica insulators with a smear of white (usually zinc oxide loaded ) > thermal grease each side - not only does this conduct heat much better but > mica will not *compress* over time like sil-pads do and result in your > mounting bolts becoming so loose you can rotate them with your fingers. > > This loss of crucial pressure ruins the performance of the heatsinking. > > That said, a black anodised heatsink radiates IR energy much better than a > silvery one - so it will generally be a few degrees cooler. Better hint. Don't use TO-220 for serious power and use pressure clips instead of screws. Screws used with devices with a single mounting hole lead to the awful scenario documented in AN1040 Fig 1 ! http://www.onsemi.com/pub_link/Collateral/AN1040-D.PDF Graham
From: Adrian Tuddenham on 19 Dec 2008 04:40 NoSPAM <unknown(a)nospam.org> wrote: >... At the temperatures normally found with > semiconductor electronics, radiation heat transfer is usually negligible. A point not often appreciated is the possible heat gain when a heatsink is operated in bright sunshine. A surface finish which is a poor radiator/absorber of radiant heat will work better in those circumstances. I have expeienced this problem with portable P.A. amplifiers used outdoors. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk
From: Phil Allison on 19 Dec 2008 04:46 "Adrian Tuddenham" > > A point not often appreciated is the possible heat gain when a heatsink > is operated in bright sunshine. A surface finish which is a poor > radiator/absorber of radiant heat will work better in those > circumstances. ** Only a complete dope would not find some way to shade the heatsink from direct sunlight on a hot day. ...... Phil
From: IanM on 19 Dec 2008 07:35
Phil Allison wrote: > "Adrian Tuddenham" >> A point not often appreciated is the possible heat gain when a heatsink >> is operated in bright sunshine. A surface finish which is a poor >> radiator/absorber of radiant heat will work better in those >> circumstances. > > > ** Only a complete dope would not find some way to shade the heatsink from > direct sunlight on a hot day. > ..... Phil I think you've just defined a 'roadie' :-) The only question is what's he doped on? |