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January 1998

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Subject:	Re: Gold Plating Question
From:	Jerry Cupples <[log in to unmask]>
Reply To:	TechNet Mail Forum.
Date:	Wed, 7 Jan 1998 09:42:05 -0600
Content-Type:	text/plain
Parts/Attachments:	text/plain (56 lines)

James Mitchell said:

>I am looking for guidance on choosing gold plating thicknesses and
>plating processes for circuit board edge fingers.  For example: What are
>the recommendations for circuit board edge fingers that will be inserted
>into a connector and removed 10 times verses a installation/removal
>cycle of 50 times?

Consider also the service environment, anticipated product life, and
desired contact impedance.

Electroplated gold typically has porosity problems. At thinner (say <30
uinches) the base metal or barrier, (typically nickel underplate) can be
oxidized, and that metal/metal oxide will eventually diffuse through the
pores and up to the surface.

If you expect to retain very low resistances over a long time, my
suggestion is 30 uin gold over 100 uin nickel.

See also IPC-6012 Qualification and Performance Standard for Rigid Printed
Boards. I think it calls for 0.8 um Au over 2.5 um Ni (class 2 product) and
1.3 um over 2.5 um for class 3. I'm guessing Diebold would not want class 1.

My impression is that the board vendors charge more for amounts which would
require them to change the setup on their tab plating line. I believe you
will find that 30 uin is a very standard callout, and there is not so much
to be saved by specifying less. Everything I say applies to FR-4 plated
through hole type US computer grade boards.


regards,


Jerry Cupples
Interphase Corporation
Dallas, TX USA
http://www.iphase.com

regards,

Jerry Cupples
Interphase Corporation
Dallas, TX

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