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January 2001

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Subject:
Circumfrential Void
From:
Sandy Kumar <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 25 Jan 2001 16:14:08 -0600
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I am looking for information on the possible causes of circumfrential voids (occuring inside the hole barrel), that I am seeing in the cross sections of multilayer FR4 boards with 10 mil holes with aspect ratio of 10. After drilling, these boards go through Blackhole graphitic carbon / Cu flash / image / Cu pattern plate with Sn as etch resist / strip dry film, etch Cu and strip the Sn/ LPI and HAL.

I would like to find out the cause for these voids. I deeply appreciate any valuable advice on how to fix this problem.

Thanks.
Sandy

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