You can look it up in an electronegativity chart for a quick "will these ruin each other" check.
I think a lot of this comes from the SIMM era in PCs, where folks were told to only use gold-flash SIMMs in gold sockets, and only tin plated SIMMs in tin plated sockets. Thanks, Jonathan On Fri, Aug 16, 2019 at 2:53 PM Paul Koning <paulkon...@comcast.net> wrote: > > > > On Aug 16, 2019, at 2:43 PM, systems_glitch via cctalk < > firstname.lastname@example.org> wrote: > > > > I'm sure DEC wouldn't have bothered with hard gold plating if their > > connectors were metallurgically incompatible :P The few busted DEC > > connectors I've replaced did indeed have selective gold plating on the > > contact surfaces. Most quality edge connector slots are similarly > > constructed. > > It's been a while and I never looked in depth, but it most definitely is > not true that gold is only compatible with gold. > > From what I remember, the detailed analysis involves an "electrochemical > series", which has metals like sodium at one end, copper closer to the > middle, and gold at or near the other end. Metals are compatible if their > potential value differs by less than a limit. The limit depends on the > environment; in an office you can have a larger limit than on a ship where > you have salt spray, or a tire factory with lots of SO2 in the air. > > There are also some twists; I think stainless steel is compatible with > many things thanks to the alloy ("stainless") properties. In fact, I think > the subject came up in connection with failure analysis of coin cell > battery holders. The battery cases are stainless steel; the question is > what contacts are acceptable. Gold is; there may be others but some things > that are used in the market are not good choices. > > paul > > > On Fri, Aug 16, 2019 at 2:27 PM ben via cctalk <email@example.com> > > wrote: > > > >> On 8/16/2019 12:13 PM, systems_glitch via cctalk wrote: > >>> Dwight, > >>> > >>> I spot check boards. I lack sufficiently sensitive instruments to > measure > >>> actual thickness (even on a surface plate, it's the same for ENIG as > hard > >>> gold with an 0.0001" indicator) but ENIG won't stand up to a few swipes > >>> with an ink eraser, whereas hard gold will stand up to it no problem. > The > >>> main issue I've seen, in buying other people's products and projects, > is > >>> board houses passing off ENIG as hard gold (and charging for it!) or > >>> claiming they're using "extra heavy ENIG" -- which of course isn't a > >> thing, > >>> because ENIG is an ion swap! > >>> > >>> Thanks, > >>> Jonathan > >> > >> Is gold plating the best thing? I thought that gold plating only works > >> best when matching other gold connections. > >> Ben. > >> > >> > >