Lee

I haven't any data so far to support any claim that lead free solder alloys are more or less reliable than Tin-Lead alloys. However, looking at data published so far that I am aware of I would like to make the following comments:
- Most of the lead free alloys creep slower than tin-lead
- It is not correct to conclude that because of this fact the lead free alloys are more reliable that tin-lead .
- Temperature cycling tests run so far are highly accelerated (steep ramps, short dwell time). The fact that in these tests the lead free alloys show a better performance does in my opinion not say that they have a better resistance than tin-lead. Primarily they show that tin- lead sees more strain during each cycle of the test.

I hope I can provide some comparative data by the end of this year. We made some PCB's with LCCC's ( 24 connectors pure tin) on FR4 with some lead free alloys ( SnAgCu, Castin, SnZn, SnAg, SnPbAg ) and right now they are in a slow thermal cycling test ( -20°C, 120°C; ramp 2- 4°C/min, dwell time 30 min at -20°C, 10 min at 120°C).

Best regards

Guenter

Guenter Grossmann

Swiss Federal Institute for Materials Testing and Research EMPA
Centre for Reliability
8600 Duebendorf
Switzerland

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

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