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August 1998

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Subject:
Re: Open Vias
From:
"Kelly M. Schriver" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 18 Aug 1998 13:56:34 -0500
Content-Type:
text/plain
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text/plain (39 lines) 
Mark - I encountered this situation a number of years back and ended up using
a higher Tg laminate to reduce Z expansion during the HASL and  soldering
processes.  This change was preceeded by a considerable amount of expensive
TMA testing, etc.  Suggest you take a close look at your post solder
microsections - are the outer pads tilted?  Do the coupons or the circuit
boards show signs of pad edge separations on the vias?  Both of these
conditions are indicators of heavy expansion.

We are currently using vias drilled at .010" diameter in boards up to .085"
thick and 14 layers and are not experiencing the problems you describe.   Note
that we are using  laminates with a 180C or higher Tg.

If I can be of assistance, my PX is 256.882.4536.

Regards - Kelly

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