Werner,

Would this also fracture the via fill material? I've seen fractured vias before, caused by thermal expansion of the copper, but never one where the via fill material is also fractured and yet the PCB is not affected at all.

Franklin

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier /*
Sent: Tuesday, March 18, 2008 9:45 PM
To: [log in to unmask]
Subject: Re: [TN] How much stress is needed?

Hi Franklin,
You describe a classic via barrel crack—comes from the thermal expansion 
mismatch between the ED copper and the PCB resin in the z-direction during the 
soldering processes [the hotter the worse—read lead-free] [you should be taking 
my workshop on the subject at IPC EXPO/APEX on the morniong of March 31.

Regards,
Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL 32174 USA
Phone: 386-437-8747, Cell: 386-316-5904
E-mail: [log in to unmask], Website: www.engelmaier.com



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