random fun fact we learned yesterday: the gold in ENIG finished boards is not there to be the thing that the solder wets and sticks to, it's only there to protect the nickel (which is a metal with very good wettability)
the gold layer in ENIG isn't as thin as it is to save cost, though that's part of it--it's intended to completely dissolve into the solder, exposing fresh nickel for the solder to wet
-F
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one reason for the nickel is as a barrier layer between the gold and copper, yes, because otherwise you get copper-gold intermetallics that can cause problems, but the other reason is to provide a very wettable surface under the gold for the solder to stick to
copper is even more wettable than nickel, but it dissolves into solder very quickly
-F
