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Date: | Mon, 16 Dec 96 09:45:22 EST |
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Dave,
Very valid points!
Technet,
I would like to add one finding pertaining to solderability of electroless
nickel - gold: Most have assumed the Phosphorus level is a major contributor to
the solderability of this surface finish. Experiments completed in my past life
have demonstrated that the nickel application process removes a portion of the
copper, placing trace amounts of copper into the bath. Upon saturation, the
copper is then re-depositied embedded in the nickel. The embedded copper
oxidizes, making the surface unsolderable. Varying the levels of Phosphorus did
not effect the solderability or yields during high volume experiments!
Allen Hertz
Racal-Datacom
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_______________________________________________________________________________
Subject: Re: solderability test for ENIG PCB finish
Author: [log in to unmask]
Date: 12/15/96 12:04 PM
Good Morning TechNet!
Your method of conducting a solderability test should not change just
because you are not using a tin/lead finish! I suggest using one of
the tests in ANSIJ-STD-003. With the emergence of the new alternative
finishes (e.g. gold, silver, palladium) the specifications are still
playing catch-up but the basic test methods are still applicable. You
may need to change a dwell time because of dissolution rates (e.g.
palladium) or may want to use a different flux because of your process
(e.g. OSP type finishes) - work with your pwb vendor to have an
acceptable test procedure both groups can use. I only have one
reference in my pile of papers that discusses the relationship of
solderability and E nickel but it's pretty good. Try:
"Factors Influencing Solderability Of Electroless Ni-P Deposits", Jing
Fang, Plating & Surface Finishing, pages 44-47, July 1992.
Good Luck
Dave Hillman
Rockwell Collins
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______________________________ Reply Separator _________________________________
Subject: solderability test for ENIG PCB finish
Author: [log in to unmask] at ccmgw1
Date: 12/13/96 10:44 PM
Dear Technetters,
What is a quick, easy & effective way of assessing
solderability/ wettability of a PCB with electroless nickel/immersion gold
(ENIG) finish? How does phosphorus content in the Ni deposits affect
solderability? Will a lower %P content in Ni be more prone to
passivation/oxidation & thus affecting solderability??
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