Re: Heatsinks

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

Original poster: "Mark Broker" <mbroker-at-thegeekgroup-dot-org> 

Aavid-Thermalloy and R-Theta have a very nice selection of online 
whitepapers, guides, references, and programs.  R-Theta, last I was there, 
had a very nice online finite element applet to test your "thermal 
solutions."  The extrusions I got from R-Theta were not machined but did 
have a surface flat enough for Steve Ward to mount two IGBT bricks to with 
no further prep work. :)

For short duty cycle I agree with Terry.  For higher duty cycles I'd shoot 
for something with fins and a fan.

Best regards

Mark Broker
Chief Engineer, The Geek Group


On Wed, 22 Sep 2004 21:55:49 -0600, Tesla list <tesla-at-pupman-dot-com> wrote:

>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)