10 Jul
2016
10 Jul
'16
2:07 p.m.
On Sun, 10 Jul 2016, Paul Birkel wrote:
Stated Tothwolf tothwolf at concentric.net:
I'm not familiar with them used in DEC systems in that way, but the
problems with mixing tin and gold plated connectors is well documented.
Even the connector manufacturers warn against mixing different platings.
Another problem that can occur is because a gold surface is softer than
tin oxide, if the header pin is tarnished, mating the gold plated contact
with the header will not break the surface of the tin oxide. Tin oxide is
not a good conductor.
"Both contact surfaces must also be the same
material or tin oxide will
form on the surface of the gold plating and cause a major headache.
This was a serious problem with 486 and earlier Pentium PCs with 30 and
72 pin SIMMs and it led to a number of lawsuits."
Almost every DEC System Unit ("backplane") that I've ever seen uses
tinned-contacts, yet the Modules all use gold-plated fingers. How does that situation jibe with the SIMM
issue/experience?
Somewhere around here I still have some 4MB 30 pin SIMMs with gold plated
contacts that were used in tin plated sockets for several years. The
damage/contamination of the gold plated SIMM contacts is significant.