Hi Jana,

It's strickly a matter of total cross sectional area. You can calculate based
on the real estate available and the number of holes you can place under the
device. Sum up the total cross sectional area of the copper in the holes. The
use of large area spreader pads at the termination of the holes helps to
distribute the thermal load. Another consideration may be the use of Thermally
conducting, but electrically insulating adhesives or prepreg to aid in heat
transfer to the ground or other thermally coducting plane. If I can be of
further assistance you can contact me by E-mail direct.

I hope this is of some help,

Les Connally,
[log in to unmask]

>  From: Jana Carraway <[log in to unmask]>, on 3/24/98 3:27 PM:
>  Good afternoon everybody.  Quick question:  which is better, lots of small
>  thermal vias, same number larger vias, or a few larger diameter thermal
>  vias?
>  We are setting up to do some thermal modeling, but I can't wait and I'm
>  "reading the last chapter" first!
>
>  Thank you for your help - Jana
>
>  Jana Carraway
>  Maxtek -- the Maxim/Tektronix Multichip Module facility
>  tel 503.627.2063, fax 503.627.4651
>  email [log in to unmask],  www.maxtek.com
>
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