Bev

I couldn't give you a number. From the metallurgical side some nm are enough because then the solder and the substrate have alloyed. The problem is the maximum. From my feelings I would say that a thick IMC is not optimal for reliability. However, I have no facts and Werner pointed out that a thick IMC doesn't do any bad to reliability. On these inputs I would say that it is important to have an IMC because it is the indicator for a successful alloying of solder and substrate. The thickness seems to be not so important.
If I find some founds left over in LEADFREE by mid 2002 I will make some trials on that.


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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