OT(ish) - delivery from eBay of small electronic components

[Roger Hayter]

I don't know either, but I suspect the process costs more than the material cost.

[Roger Hayter]

I think it does on very high speed ones, where a change in resistance creates discontinuity, leading to reflection and inability to accurately measure transitions. Don't forget that high speed digital signals or

*not* binary at the physical layer, but more like RF digitial signals, multi-level and phase dependent. !0GBe for instance.

[Johnny B Good]

====snip====

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).

[alan_m]

Unless the box is hermetically sealed then a corrosive atmosphere that affects the plugs is likely to kill the internal electronic components.

[alan_m]

But you can introduce problems when you solder to gold plated pins.

[RJH]

On 26/01/2018 21:15, Roger Hayter wrote: snip Don't forget that high speed digital signals or

JOOI, in what way are they not binary?

[tabbypurr]

it's only useful if your connectors have an otherwise inadequate mating sur face area.

a very different situation to signal connectors

NT

[tabbypurr]

In almost all cases it just corrodes the surface of the wiring. Paper caps are to some extent suseptible to damp though.

NT

[Roger Hayter]

They are binary as far as the computer at each end is concerned, but they are carried over the copper pairs (or fibre, but we are talking about gold contacts!) as multi-level signals, effectively analogue signals.

[RJH]

Ooooh, didn't know that! Not sure what I thought happened, mind.

Presumably it gets unpacked at either end with no change to the data - is the 'cost' some very minor latency perhaps?

The paper is way over my head, but thanks anyways. References to FEC seem to be relevant, but I'm not sure.

[Roger Hayter]

The main point I was making was that we now get the very most out of our copper for digital signals, to the point that they are as critical for good contacts as low level analogue signals. In fact, more so because of transmission line effects. Any intrinsic robustness of digital signals has been traded for frankly incredible (to someone trying to get up to 30MHz out of a pentode fifty years ago) bandwidths.