GW-DEC-1: A New DEC Prototyping Board

[systems_glitch]

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 <paulkoning at comcast.net> wrote:

>
>
> > On Aug 16, 2019, at 2:43 PM, systems_glitch via cctalk <
> cctalk at classiccmp.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 <cctalk at classiccmp.org>
> > 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.
> >>
> >>
>
>