I vote with Ian and Groovy Hoovy. 

This is a classic void. The copper edge is convex suggesting copper was depositing at the edge of an un-plate-able area. There was either no electroless or some resist where the void occurred. 

Since it is technically a "ring void" (thank you Chuck) I expect that there may have been a ring of resist residue from developing or a contaminated rinse. But if it is a 360° ring void how did it pass electrical test? I would call it a "half moon" void but that would be lunie.

It is not an etching void because if this were an etch-out the edge would be concave. 

It could not be a bubble because how could a bubble be so flat. It can't be two bubbles because small bubbles would rise to one side of the hole. 


Sincerely, 
Paul Reid 

Program Coordinator 
PWB Interconnect Solutions Inc. 
235 Stafford Rd., West, Unit 103 
Nepean, Ontario 
Canada, K2H 9C1 
613 596 4244 ext. 229 
Skype paul_reid_pwb 
[log in to unmask] <mailto:[log in to unmask]> 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Al Onderick
Sent: June 17, 2010 5:04 PM
To: [log in to unmask]
Subject: [TN] Thursday Quiz

What causes this ?

http://www.austinwoodsandwaters.com/open-via.jpg



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