Hi Maurice -
     
     Take a look at the solderability of the boards. You may have pads 
     where the nickel underplate has diffused to the pad surface via the 
     gold grain boundaries or porosity in the gold finish. Check out 
     "Assessment of Circuit Board Surface Finishes for Electronic Assembly 
     with Lead free Solders" by Dr.U. Ray, et all, SMI 96 Proceedings page 
     656 for more info.
     
     
     Dave Hillman
     Rockwell Collins
     [log in to unmask]
     


______________________________ Reply Separator _________________________________
Subject: ass- gold/Ni solder skips 
Author:  [log in to unmask] at ccmgw1
Date:    3/27/97 9:16 AM


Date 27/3/97
Subject ass- gold/Ni solder skips
>From Maurice Dore
To Tech net
     
                      ass: gold/Ni solder skips
Hi
I'm wave soldering a board with gold/nickel finish and I've recently seen 
some bizarre incidents of certain pads entirely not wetting, some with a 
slight degree of wetting and the majority showing very good wetting.
I have a gut feeling that it's related to variation of temperature in the 
solder bath but I really am not sure why its recently started happening.
     
Any opinions welcome.
Thanks in advance.
     
     
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