Colin,

Are you referring to a UV bump of the solder mask? If so what type of solder
mask are you using? Different solder masks react differently to UV,
especially after post cure. If you would like to discuss, I would be happy
to assist. There are many processing techniques involved in successful
processing of Ni/Au.

Regards,
Bob Metcalf
949-709-2544

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Colin McVean
Sent: Wednesday, March 23, 2005 12:27 PM
To: [log in to unmask]
Subject: [TN] Nickel Gold "step" plating


Hi to all,



We've just completed a batch of Polyimide multilayer PCB's and Ni/Au'd
as our solderable finish.

We have noticed that the Ni/Au has plated onto and around the pads, and
joined up some quad pack pads.

I seem to recall something about Zinc Octanoate acid leaching out from
the surface of the Polyimide, which acts as a catalyst for the solution
to get a grip and plate onto what is bare substrate, or have I got the
wrong end of a long stick?

Would a UV bump lock the substrate surface prior to the finish, or are
there other remedies? (we already IR bake resist at upto 150oC prior to
the application of Ni/Au)



Colin McVean

Production Manager

Artetch Circuits Limited

Tel: 01903 725365




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