Hi Tom! Well, the appropriate answer would be "it depends" (cha-ching, 
Doug Pauls gets another Diet Mt. Dew). In general, mixed metallurgy 
systems are not as reliable as a non-mixed metallurgy system. The more 
severe the product use environment, the more impact a mixed metallurgy 
system has on the overall product integrity. I recommend you look thru the 
IPC APEX and SMTAI Conference proceedings for the last couple of years - 
there have been a number of good papers documenting the interaction of 
SAC305 and SN100C. You can compare those test results and test conditions 
to your product use environment to see if mixing is appropriate. The NASA 
DoD Leadfree Solder consortia is investigating a number of mixed 
metallurgy situations using a wide variety of tests (vibration, thermal 
cycle, drop shock, etc.) and should be reporting some of those results in 
the next few months. Good Luck.

Dave Hillman
Rockwell Collins
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Tom Burek <[log in to unmask]> 
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02/16/2009 12:28 PM
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[TN] Lead Free solder compatibility






Hello technetters,
I have a lead free solder question.  If I have a PCB with a SN100C finish 
and hand solder a component using  a tin Silver solder (SN96.5AG03 Cu.5), 
is there a possibility of creating a joint that may be less reliable, 
perhaps more brittle?

Thank you


Tom Burek, CID+

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