On Fri, 26 Jan 2018 11:30:51 -0800, tabbypurr wrote:

====snip====


quite, the problem is something other than lack of gold. They're junk
grade stuff.

3.5mm is simply too small to be robust enough to last normal use. Again
gold is not the solution.

The whole point of gold plating contact surfaces is to improve
reliability of the galvanic connection. Gold plating achieves this in two
ways. The first and obvious way being the elimination of tarnishing which
would create a high contact resistance in the case of base metals. The
second, seemingly less obvious way, being the larger effective area of
contact due to Gold's malleability creating an electrical gasket effect
that improves electrical conductivity across the whole of the larger
contact area.

Unfortunately, due to the very high price of Gold, its use as a contact
plating material can significantly increase the BoM costing of any
component parts such as DB25 connectors, memory modules and ISA/PCI/PCIe
adapters cursed with connectors that have contact counts ranging upwards
of 25 and beyond so a compromise is applied in the form of extremely thin
platings which can be guaranteed only to be good for as little as a mere
25 insertion cycles!

An alternative compromise is the use of "Hard Gold Alloy" plating which
gives a much longer insertion cycles lifetime rating but at the expense
of the initial quality of contact resistance achievable with unalloyed
Gold platings. You retain the tarnish resistance but the price of that
wear resistance is that you lose a lot of the benefit of the electrical
gasket effect inherent with unadulterated gold plating. As a result, such
hard gold alloy platings are more susceptible to the effects of
contamination from air pollution (grease and dust).

Fortunately, this propensity to poor contact can be mitigated by
'exercising' the connector through a few insertion cycles (three or four
cycles seems to be the charm with memory modules and PC adapter cards -
especially beneficial when assembling a desktop PC from a complete set of
brand new component parts).

--
Johnny B Good