Susan: We have built product similar to this using a process called
"Selective First Gold". The Ni/Au feature(keypad, LCD pad, rotary switch
etc,)is plated directly onto the electroless Cu. Sometimes these Au features
contain vias which require a full build up of plated Cu in the hole. To
accomplish this the Au feature is covered with plating resist except in the
via area where it is opened up with a pad and overplated with Cu during the
primary circuit Cu pattern plate operation.

The cross section of the finished hole would be: els Cu 50u", Ni
electroplate 200u", Au electroplate 25u", Cu electroplate 1200u".

We have not experienced any reliability issues for these products based on
this style of construction.


Regards

Michael Barmuta

Staff Engineer

Fluke Corp.

Everett Wa.

425-356-6076
-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Monday, July 26, 1999 8:20 AM
To: [log in to unmask]
Subject: [TN] NI/AU UNDER BETWEEN COPPER


I just looked at a product where the manufacturer has managed to
overplate nickel/gold with copper.  This occurs on the surface conductors
and also in holes.

I have looked in the design and board documents, but cannot find anything
that addresses the reliability of such a condition.  I know putting a
"meltable"
material between layers of copper can wreak havoc, but what about
ni/au?

Susan Mansilla
Robisan Lab

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