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List:       classiccmp
Subject:    =?UTF-8?Q?Re=3A_34_pin_Card_Edge_=E2=80=9CMale_to_Male=E2=80=9D_Connector?=
From:       Eric Smith via cctalk <cctalk () classiccmp ! org>
Date:       2018-11-29 19:00:06
Message-ID: CAFrGgTQH+RAovTw+C6+0zd4gp+MToG-MyFNAJxqb07DSWHTGXQ () mail ! gmail ! com
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On Thu, Nov 29, 2018 at 11:52 AM Eric Smith <spacewar@gmail.com> wrote:

> Sure, but that's just 0.05 to 0.125 microns of ENIG (electroless nickel
> immersion gold). That's not intended for mating surfaces, and will wear
> away after only a small number of connector cycles.
>
> For reliable edge fingers you need "hard gold" (AKA "hard electrolytic
> gold"), which is 0.75 to 2 microns of gold electroplated over 3 to 6
> microns of nickel.
>

I can't find any figures for ENIG, but hard gold is expected to last for
300 to 1000 mating cycles, depending on the plating thickness. Since ENIG
has about 1/15 as much gold, one might expect it to last 20 to 60 mating
cycles at most. Possibly fewer since there's not only a lot less gold (and
less nickel), but also a different application process not engineered to
support surface mating.
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