On Thu, Nov 29, 2018 at 11:52 AM Eric Smith <spacewar at gmail.com> wrote:
Sure, but that's just 0.05 to 0.125 microns of
ENIG (electroless nickel
immersion gold). That's not intended for mating surfaces, and will wear
away after only a small number of connector cycles.
For reliable edge fingers you need "hard gold" (AKA "hard electrolytic
gold"), which is 0.75 to 2 microns of gold electroplated over 3 to 6
microns of nickel.
I can't find any figures for ENIG, but hard gold is expected to last for
300 to 1000 mating cycles, depending on the plating thickness. Since ENIG
has about 1/15 as much gold, one might expect it to last 20 to 60 mating
cycles at most. Possibly fewer since there's not only a lot less gold (and
less nickel), but also a different application process not engineered to
support surface mating.