The trick
is to establish where and when the void occurred; poor metalization (black-hole
in this case), poor electroplating, or poor Sn(pb?) plating and thus an etched
void.
Shop
history and a keen read of the micro-sections will provide the biggest clues.
Ian
-----Original
Message-----
From: TechNet
[mailto:[log in to unmask]]On Behalf Of Sandy
Kumar
Sent: Thursday, January 25, 2001
5:14 PM
To: [log in to unmask]
Subject: [TN] Circumfrential Void
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