Colin,

What you are describing is referred to as "Nickel Foot" that is the
extension of the deposit unto the laminate, creating bridging between  pads.

"Step Plating" is used to refer to different Ni thickness on the same pad
surface. Usually most of the pad would be plated with a uniform thickness and
there would be a lower thickness at the edges or the knee of the pad.

The Ni Foot problem may be due to residual copper that was not etched away
during circuitization, a cross section in that area could readily identify if
this is the case.

Another reason for the same defect could come from an out of control
chemical deposition process. An over active Ni bath due to one or more of the
following: pH out of control, temperature out of control, stabilizer not
replenished, drag in of catalyst into the bath.........etc.

Electroless Nickel/immersion Gold is a multi-step process. Attention must  be
given to ensure all process steps are as specified by the  supplier with
adequate rinsing between steps.

I hope this information is helpful.

Best  regards

George Milad
[log in to unmask]
National Accounts Manager  for Technology
Uyemura International Corporation
Technical Center
240  Town LIne Rd
Southington CT 06489
U S  A
(516) 901 3874 (mobile)
(860) 793-4011 (office)
(860) 793-4020  (fax)


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