Hi:
        We are presently using electroless Ni/Immersion gold metallization
on our SMT PWBs. Our present requirements are:
>            A.  FINAL FINISH TO BE IMMERSION GOLD PLATING, 10 MICRO INCHES
> THICK
>                   MAXIMUM, OVER 6-9% PHOSPHORUS CONTAINING ELECTROLESS
> NICKEL PLATED
>                   BASE 0.0003 TO 0.0007 INCHES THICK OVER ELECTRO
> DEPOSITED COPPER.
>
One of our PWB suppliers intends to change their Electroless Nickel bath.
The current
phosphorous content of plated nickel is between 6% and 9%. The new bath will
produce phosphorous content between 9% and 12%.

        Reason: The higher phosphorous content prevents occurrences of
"black pad nickel" and also better resist excessive attack on the nickel by
Immersion Gold. So we expect to reduce, or even eliminate, rejections of
product due to excessive gold or for black nickel under gold.

Does the increased phosphorous content eliminate black pad nickel?
Is there going to be an effect on solderability or long term solder joint
life?
Will the PTH barrel become stronger and result in increased stress in the
connections between the inner plane and the PTH?

We are concerned that we may be trading one set of problems for another.

Thanks in advance for any help you can offer.




Steph

Stephan Meschter               [log in to unmask]
Lockheed Martin Control Systems  Phone  :(607)770-2332
600 Main Street, MD R52F         FAX    :(607)770-2056
Johnson City, NY 13790-1888      MARCALL: 8 * 255-2332

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