Hi Poh,
Yes, studies like this have been done. Basically what kills the solder joints
on Alloy 42 TSOPs is the large global CTE-mismatch with FR-4, which depending
on the design details can be larger than a factor of 5 than the CTE-mismatch
between copper TSOPs and FR-4. The local CTE-mismatch between the Alloy 42
and the solder itself also does not help.
Using Appendix A of IPC-D-279, 'Design Guidelines for Reliable Surface Mount
Technology Printed Board Assemblies', you can determine the particular
difference for your situation and the resulting difference in cyclic lives,
which can be as large as a factor of 50. Of course, you can also engage my
services to estimate the reliability of your solder attachments on your
product for your application.

Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
23 Gunther Street                                In December:                                            Jasmine Run
Mendham, NJ  07945                                                                  Ormond Beach, FL  32174  USA
Phone & Fax: 973-543-2747                         Phone: 904-437-8747, Fax: 904-437-8737
E-mail: [log in to unmask]

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