Many disagree with several reasons - in my opinion, none are good. I never
bond anything using 7628 preg. I use only more resin rich glass glass styles
facing copper or other 7628, except 7628.

Earl Moon
----- Original Message -----
From: ±è´Þ¿µ Â÷Àå ÀüÀÚ ÁõÆò°øÀåÇ°Áúº¸ÁõÆÀ <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, September 29, 1999 6:07 PM
Subject: [TN] Any Opinion?


> Dear Technetters ;
>
>    I'm experiencing somewhat strange defects on 6 layerered PCBs.
>   The defect itself is not actually strange one because I and everyone can
> easily find out it as a blister.
>   But the blister is only in the thin core laminate while there is not any
> one between bonding layers.
>   The thin core laminate is composed of two 7628 prepregs. The
manufactured
> quality was good.
>   Please let me describe more details about the 6 layered PCB.
>   The first layer contains parts of ground and signal patterns with
> adjacent 2 plies of 7628 bonding
>   prepreg to 2nd layer. Yes, the 2nd layer is the one copper of the thin
> core laminate and
>   this layer plays the signal role with seldom copper lines.
>   The third layer contains large copper area and it means this layer is
> power and ground.
>   I watched 14 PCBs which were rejected after reflow soldering process had
> blister only in the edge
>   or the near point to edge. The PCBs had no blister before reflow
> soldering process.
>   I couldn't believe that why the blister is only in the thin core
laminate
> and why it happened
>   after reflow process because the PCBs were noble ones that overcame
> severe heat shock through
>   HSAL process. Why does the blister be connected to the edge of the PCB?
>   Moreover I surprised at the fact that for three times in 2 years, our
> colleage has been experiencing
>   the same phenomena with the same construction PCBs with the other 3 PCB
> houses.
>   Please save me from the 'blister Ghost'.
>
>   Thanks for your attention and in advance.
>
>   Tal Young Kim
>   QA Dept.
>
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