Hi Werner,

I would like to clarify this point with you:-
>I do not know where the notion
>of "Cu diffuses into the Au" or that"Ni acts as a barrier layer to
prevent the
>formation of CuAu intermetallics" comes from, but that is not the case.

If this is not true, then I too have been guilty of giving out
misinformation. The solderability of a gold on copper surface
deteriorates for some reason and I thought this was due to copper
migrating into the gold to the surface. This also causes contact
resistance to rise on edge connectors even with significantly thicker
gold deposits on copper. The plating of Nickel on the copper reduces
this and it would seem that the Nickel does act as a barrier. If this is
not the reason then what is the mechanism, and why do we need to plate
nickel on edge connectors?

Best Regards
Paul Gould
[log in to unmask]
Isle of Wight,UK

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