[tinwhiskers] Re: Exemption on high temperature lead solder
- From: Engelmaier@xxxxxxx
- To: ed.parnagian@xxxxxxxxxxx, tinwhiskers@xxxxxxxxxxxxx
- Date: Tue, 26 Aug 2008 12:21:39 EDT
Hi Ed,
There are a number of possible and possibly interacting scenarios.
1) larger CPU chips are subject to larger 'global' and 'local' thermal
expansion mismatches-- using eutectic SnPb does help the 'global' mismatch and
there
is a design solution for the 'local' mismatch;
2) the higher soldering T's required for SAC solders produce larger 'global'
and 'local' thermal expansion mismatches--that is a direct fault of RoHS;
3) reduced solder joint thickness [to reduce overall package thickness]
produces higher cyclic SJ strains for the same 'global' expansion mismatch.
Werner
Future workshops:
Pb-Free Soldering Processes: Survival, Quality, Reliability, September 3,
Stockholm, Sweden
Reliability Issues with Lead-Free Soldering Processes, September 22,
Schaumburg
Failure Mode and Root Cause Analyses Reliability (Fatigue, Brittle Fracture,
ENIG), September 22, Schaumburg
Solder Joint Reliability: Parts 1 & 4, Oct. 9, Moscow, Russia
Solder Joint Reliability: Part 4, Oct. 17, Timisoara, Rumania
Solder Joint Reliability: Parts 1 & 4, Oct. 22, Tallinn, Estonia
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