Re: Heatsinks

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>

Hi,

In many cases, one can just find thick scrap plate aluminum and tap some 
holes in it.  All the fancy fins and such help, but just being bolted to a 
big chunk of Al does 80% of the job.  It "needs" a "flat" surface, 
otherwise when you bolt the device down it might make a cracking noise 
:-(   Also, the holes for mounting need to be well deburred so there are 
not edges that might hold the gap open.  Ideally, if the device to sink gap 
is about 0.0005 inch, you are home free.  If it is 0.005 inch, your are 
dead no matter what...  Big copper plate IGBTs are more forgiving.  Blow 
air onto it for about a 10X increase in thermal dissipation...  Water cool 
for 50X...

Those fancy heat sinks are expensive due to the flat machined surfaces and 
the well tapped mounting holes.  But if you look around, you can find flat 
aluminum pretty easily at scrap yards.  Just drill big holes and use bolts 
too...  I simple auto machine shop might true the surfaces cheap if you 
talk to them.

Cheers,

         Terry - "Mr. Thermal" (retired)


At 12:42 PM 9/22/2004, you wrote:
>Sometimes you can find some good deals at 
><http://www.hosfelt-dot-com/>http://www.hosfelt-dot-com/
>You could also try ebay.
>Cheers,
>John
>
>Tesla list <tesla-at-pupman-dot-com> wrote:
>Original poster: "Chris Swinson"
>
>HI all,
>
>Does anyone know wheres a good place to try for large heatsinks ? the ones
>ive seen so far cost a small fortune :(
>
>cheers,
>chris