Hi Jana,

Be careful of placing the holes so close together, You don't want to destroy
the integrity of the laminate. This spacing is encroaching upon the general
spacing between the warp and fill dimensions of the glass weave. I took a quick
look at the comparable cross sectional areas for a .5 by .5 inch square area
using the hole dimensions and spacing you provided. If the copper thickness in
the respective holes is constant, the small holes provide a marginally greater
cross section. In my look at the numbers, It did not seem to buy very much area
and the ease in drilling the larger holes, would probably be to your advantage.
I would be interested in what your calculations indicate.

Lots of luck,
Les

>  From: Jana Carraway <[log in to unmask]>, on 3/25/98 10:07 AM:
>  Les, what distance between holes?  I am using .010" distance, edge to edge,
>  to
>  calculate how many holes I can place in the rectangular copper area, and
>  from
>  there total copper area small vias vs larger holes.  We are doing the
>  calculations for 0.008" vias and 0.035" holes.
>
>  Thanks 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
>
>
>  "Leslie O. Connally" <[log in to unmask]> Wrote:
>  |
>  | Jim,
>  |  I agree with one exception, If we are talking about the
>  | same number of holes,
>  | the larger holes will yield the greater cross sectional
>  | area. If more small
>  | holes are placed on a smaller grid, then the greater area
>  | can be accomodated.
>  |
>  | Cheers,
>  | Les Connally
>  |
>  | >  From: Jim Marsico 516-595-5879 <[log in to unmask]>,
>  | on 3/25/98 10:13 AM:
>  | >  Whichever yields the most cross sectional area of
>  | copper will give you the
>  | >  best
>  | >  thermal performance, therefore, more small holes would
>  | be the best scenario.
>  | >  We, in fact require vias to be plated with .002" of
>  | copper for thermal
>  | >  reasons.
>  | >
>  | >
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