Heinz,
Residual Cu/Sn on the edges could cause step plating.  A couple of things
come to mind to solve.
 Is your solder strip complete?  Can you double pass the part through the
stripper a second time
as a test?
Is your microetch step at mas.  Could you remove 80 uins or 2 microns
without imparing the
pads?
I am also aware of another situation where baking at 120 degrees C for one
hour solved the problem.
I don't know a good explanation for this but it maybe worth a test.
Hope this helps.

Marion Graybeal

----- Original Message -----
From: Heinz Mader <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, January 31, 2001 3:16 AM
Subject: [TN] electroless nickel gold stepplating problems


> Hallo outhere in th big pcb world
>
> We have a plating problem with PCB ,we plate full electroless nickel
> gold ,that means without solder mask.
> The problem is,.that from time to time we have stepplating of nickel
> This happens only on two types of boards,others boards we plate the same
> way and there it never happens stepplating.
> We work mith the Ronamerse SMT-Process from Shipley
>
> We have no problems with skip plating in selektiv nickel gold
>
> I hope for good ideas
>
> hopefull greetings from switzerland
>
> Heinz Mader
> Ascom AG
> CH 3000 Berne
> Switzerand
>
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