Wee

In LEADFREE we finished our reflow- production tests about 3 Months ago and we also soldered CSP's with SnAgCu bumps with SnPb. Metallurgically there  was no problem. The SnPb solder diffused win the SnAgCu and it was actually quite tricky to prepare the micro sections in a way to see the alloying of the two. Long term reliability is still a subject. Slow comparative thermal cycling test in our lab where we soldered SnAgCu solder on SnPb showed no influence of the combination on crack growth.
I cant tell you any more at the moment. We are still in the analysis of the solder joints. After that we will start thermal cycling tests that will hopefully shed some light on the degradation behaviour under alternating thermal load.

Best regards

Günter 

EMPA
Swiss Federal Institute for Materials Testing and Research
Centre for Reliability
Guenter Grossmann,  Senior Engineer

8600 Duebendorf
Switzerland

Phone: xx41 1 823 4279
Fax :     xx41 1823 4054
mail:     [log in to unmask]

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