Hi Siggi,
>The customer is looking for a statement from us about reliability issues if
>the go to lead free (15 year warranties).
>His concern is that the results on the test board's are not fully comparable
>to the reality.
>
>What is your recommendation:
>Which test should be used Twist and Bending, T cycles, T shock....
***We do not have a creep-fatigue model or acceleration factors for
LF-solders. Thus, the only way to warrant 15 years is to T-cycle according to
SM-785 and IPC-9701 relatively close to the T-extremes experienced in the
field. LF-solders have an even more complex creep-fatigue behavior than Sn/Pb
solders.
>What is the most critical think according to your opinion (brittle fracture
of BGA solder joints because of mechanical bending ?)
*** If the BGA interfaces are the weak link yes, but it depends on the
largest CTE-mismatch in you PCA.
>Would you change land and stencil design?
***I have seen no indication for this.
>Which standards would you use to qualify the PCBA for the product?
***IPC-9701

Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL  32174  USA
Phone: 904-437-8747, Fax: 904-437-8737
E-mail: [log in to unmask], Website: www.engelmaier.com

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