Hi Jan,
You sure must have been looking under wrong headings in the TechNet archives,
because none of your listed suggestions pertain to or help with Au-plated
pads, and I know there is useful info in the archives.
Yes, 'gold embrittlement' or more correctly 'gold weakening' is a real—as in
solder joints can fail—defect. The dull appearance of your solder joints means
that AuSn intermetallic compounds (IMCs) have reached the surface. It also
means that your Au-plating was rather thick. Gold embrittlement will be a
factor with 4% or more of Au by weight in the solder. Your surface appearance
is an indication that you are likely to have more than that in your solder
joints. Unless you have an application, where bending of the PCA or vibration
or more than benign temperature cycling are not issues, you can expect solder
joint failures sooner than without the gold. These could be catastrophic
infant mortalities.
The only solution for pads plated with too much Au is to wash the Au off; I
take it you have gold plating because of some contact fingers, so you need
careful shielding of these fingers.

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]

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