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
[log in to unmask]
_______________________________________________________________________________
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
     [log in to unmask]
     
     
     


______________________________ 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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