Hi Zoran -
     
     Many of the users in the ANSIJ-STD-003 PWB solderability committee who 
     have experience with immersion Au/Ni finishes have reported that a 
     "good" immersion Au/Ni finish should last 12 months under typical 
     storage conditions. The critical part of the equation seems to be 
     finding a finish supplier understands their immersion gold chemistry 
     and that does a good job of process control. Also take a look at "Fine 
     Pitch Surface Mount Technology Assembly with Pb free low Residue 
     Solder Paste", I. Artaki, Soldering and Surface Mount Technology, May 
     1995, page 27 - it may be helpful. Good Luck.
     
     
     Dave Hillman
     Rockwell Collins
     [log in to unmask]
     


______________________________ Reply Separator _________________________________
Subject: ASSY:Au/Ni Coated Boards
Author:  [log in to unmask] at ccmgw1
Date:    5/28/97 9:08 PM


     
Dear Technetters
We have some printed circuit boards with gold over nickel coating which   
are experiencing solderability problems, ie very poor wetting. I have   
heard that this may be due to nickel migration through the gold over   
time. The boards are approximately 6 Months old. Is there a particular   
shelf life for this type of coating before we need to dump the boards?.
     
Regards
Zoran Raich
Process Engineer
NetComm (Aus) Ltd
(+612) 9878 7394
[log in to unmask]  
     
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