---------- Forwarded message ----------
Date: Wed, 6 Sep 95 14:17 CDT
From: Crawford, John A. <[log in to unmask]>
To: TechNet-request <[log in to unmask]>
Subject: RE: Ni contamination


Following from the EMPF in Indianapolis:  Jeff Kukelhan, our solderability 
expert prepared this suggestion.
My guess is that the insulative substance is nickel oxide.  It is very 
tenacious, and gives nickel some of its
corrosion resistant properties.  You might have them try spot plating the 
area in question with gold or palladium.
These are corrosion resistant, relatively soft, and make excellent 
electrical contacts.

If you would like to discuss this you can phone the EMPF HelpLine at 
317.226.5616. We can do an analysis for you within our frame of 16 hours 
free consulting and determine exactly what the contaminant is if you prefer.
 ----------
From: TechNet-request
To: Technet
Subject: Ni contamination
Date:  6 Sep 95 10:41AM

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Subject: Ni contamination
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I manage a captive PWB shop that produces 4,000 square feet per week of
double sided plated thru hole product from .062 FR-4 copper laminate.  Our
product is a bit uncommon in that it has about .0004 inch hard nickel plated
over the copper traces.  Thru testing, we find a VERY thin layer (maybe 150
angstroms) of some contaminate that affects the surface conductivity when it
is used as a switch half with a stainless steel snap dome.  Using a
Scotchbrite pad to burnish the surface provides a solution, but I would like
to know the source of the substance and how to prevent it in the original
process.  Any ideas on the subject?


Have it analyized. Try Auget (OJ) testing. You'll probably find that one of
your post Ni Plate processes is depositing the film and producing the
contaminate. Nickel is also prone to passivation when it's alone and left
exposed for some time or exposed to thermal excursions. (eg, high temp 
bakes)


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                Dave Hoover              (408) 728-6677
                Senior Process Engineer  (408) 728-1728 Fax
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