Hi,
We saw a similar occurence on polyimide boards wiht 2 oz plane layers a
while back. It was attributed it to a resin rich zone (no glass fibers went
into this gap) between the etched clearance in the plane layer and the pth
barrel. I seen to remember that the cracking was due to drilling stresses. I
don't remember all the details just the solution.  We ended up putting
non-functional pads in the plane layer. This allowed the drill to go through
copper rather than the resin.

Hope this helps.
Steph

*********************************************************
Stephan Meschter               [log in to unmask]
Lockheed Martin Control Systems  Phone  :(607)770-2332
600 Main Street, MD R52F         FAX    :(607)770-2056
Johnson City, NY 13790-1888      MARCALL: 8 * 255-2332
*********************************************************


> ----------
> From:         James A Larson[SMTP:[log in to unmask]]
> Reply To:     TechNet E-Mail Forum.;James A Larson
> Sent:         Monday, June 08, 1998 10:42 AM
> To:   [log in to unmask]
> Subject:      [TN] Radial Cracks on Cyanide Ester resin
>
> Has anybody experienced Radial Cracking as viewed from a
> horizontal section or Fishscale cracking as viewed from a
> vertical section using Cyanate Ester Resin.  This resin system
> is used to fill a 2 oz. copper plane layer in a 8 and 10 layer board.
>
> If so what parameters have you compensated for to help
> minimize this situation?
>
> We've modified  press parameters and drill parameters with
> minimal success.
>
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> 847-509-9700 ext.312
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>

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