Chris,
I also agree that it looks like it was burnt at the corner, then plated
over. It's no surprise that such a corner would be more prone to
cracking; the burnt volume is almost completely lacking in mechanical
strength, and the "nodular" nature of plating under the burn area will
create stress risers. It looks to me like the crack started at one of
these stress risers and propagated through the underlying plating.
The smoking gun here is that the overlying plating is undamaged.

Fritz

-----Original Message-----
From: IPC-600-6012 [mailto:[log in to unmask]] On Behalf Of Chris
Mahanna
Sent: Monday, August 16, 2010 12:19
To: [log in to unmask]
Subject: [IPC-600-6012] opinion poll

Hi Everyone,

Attached is a picture of a thru-hole corner after thermal stress.  The
plating is pulse.  I believe the corner was 'burnt' because of the
geometry of the (conformant) negative etchback.  All the corners show
burn; some show blisters; only this one cracked.

In your opinion, what are the non-conformance(s) if any?


Thanks

Chris

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