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November 2000

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Subject:
From:
Mike Fenner <[log in to unmask]>
Reply To:
Mike Fenner <[log in to unmask]>
Date:
Mon, 27 Nov 2000 17:10:26 -0000
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Nigel, The usual cause of poor solderability of Au over Nickel is
passivation of the nickel.
The most common reason for this - assuming boards are not out of
time - is the Au being too thin or porous.
The next most common is the nickel is already passivated at the time
of application of the Au.

[Keep in mind the Au plating does not enhance the solderability of the
Ni, the best it can do is keep the Ni in the same condition as when it
was applied.  The worst it can do is to shield the Ni from any
attempts to correct the problem.]

In either case I am not sure what you can do, other than to understand
your supplier's problems. At the risk of sounding a little harsh why
do you want to take this problem on anyway? The boards are either to
your specification and functional requirements or they aren't. You
naturally have a spec which calls out optimum plating thicknesses and
you have a solderability test included to ensure functionality, so
what do you need to do if work is found to be out of spec or
non-functional and non-correctable?

Mike


----- Original Message -----
From: "Burtt, Nigel" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, November 27, 2000 10:16 AM
Subject: [TN] Ni/Au solderabilty


> Anyone out there got more than their fair share of problems with
> solderability on PCBs with electroless Ni/Au surface finish at the
moment?
>
> We have had problems before from a supplier, with Ni/Au boards
poorly dried
> after the final rinse and others with copper contamination in the
acid clean
> bath, but this looks like it might be a new cause. Phosphorous
content does
> not seem to be relevant.
>
> Thanks
>
>
> Nigel Burtt

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