Hi Badri,
Your 'Subject' line says: "Delamination of lead free PCBs," but your problem 
has nothing to do with delamination.
You have in fact 2 problems not related to any delamination.
(1) the thickness of the inner-layer traces is not thick enough according to 
specifications and your customer belives that the current carrying [not 
voltage] capacity of the 35 micron tracks is insufficient for their use. Whether or 
not this is in fact true is immaterial—the PCBs have not been manufactured to 
spec.
No salvage for these PCBs.
(2) there are discontinuities in the PCB interconnects on over 50% of the PCBs
—you do not give any details on the responsible failure mode. This could be 
either because of via barrel cracking or inner-layer (post) separation—no way 
of knowing without x-sections.
No salvage for these PCBs.

ACTION ITEMS:
(1) Do a failure mode analysis—this will tell you what needs fixing.
(2) From (1) you can tell whether the design is adequate for Pb-free 
soldering or whether the root cause is production quality [track thickness and/or 
other reasons]. 
If it is a design/specification issue, you may want to get my White Paper 
"Recommendations for PCB FAB Notes and Specifications in Printed Circuit Board 
Drawings for SnPb and Lead-Free Soldering Assemblies, the Qualification of PCB 
Shops and Activities to Assure Continued Quality."
If it is a quality issue, fix it.



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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