16 Aug
2019
16 Aug
'19
11:56 a.m.
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.
>
>