Many of our customers are using the old MIL-STD-275 to specify gold
thickness for Hard Gold. They are ordering this because they are doing both
wafer and package testing at the die and device level. So, we are seeing 50
to 100 uin of gold over nickel. It hasn't been much of an issue because we
build most of the boards by hand soldering methods.
We are starting to see components in the parts list for these assemblies
that cannot be installed with hand soldering methods.
When we solder with printed paste and reflow methods we see dull, grainy
joint that are clearly contaminated with gold.
When we hand solder this condition is not evident. (I believe the condition
may actually be worse because the dissolved gold is more concentrated near
the bottom of the fillet. But, that is another discussion).

Does any one have a rule of thumb for the maximum thickness of electroplated
gold on land patterns intended to receive SMT components . . . say, 0402
passives or MLFs?



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