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