Good Morning!
     
     Your supplier seems to have lost the recipe and I agree with you - 
     your tolerances are reasonable and your vendor should be able to meet 
     them. A gold/nickel finish would work for your press fit pins because 
     you typically do one-and-done insertion - you make a good 
     metallurgical connection and leave it alone. If you were going to do 
     several connect/disconnects and/or had low insertion forces I would be 
     concern about leaving oxide/metal debre that would later cause 
     electrical problems.
     
     
     Dave Hillman
     Rockwell Collins
     [log in to unmask]


______________________________ Reply Separator _________________________________
Subject: FAB:Electroless Ni/Immersion Au & press-fit connectors
Author:  [log in to unmask] at ccmgw1
Date:    11/21/96 6:27 PM


Our principle product uses a 14"x17", .125 thick, 8 layer backplane with 48 
press fit connectors. Its currently specified as SM over reflow solder. Our 
PCB supplier has performed wonderfully in the past, but we are now receiving 
some boards with out of spec finished holes (spec .033 +.002/-.003). Cross 
sectioning shows the problem to be extra, irregular solder buildup in the 
holes. They are suggesting we should spec SMOBC to help the problem. Another 
new vendor we are talking with is recommending a Ni/Au process. My feeling 
is the original vendor produced very satisfactory product for 3 yrs, and 
should be able to continue to do so. However, I'd like to take this 
opportunity to do some investigation. I have a few questions:
     
1. Is anyone out there using Ni/Au on boards with press-fit connectors?
2. Would anyone venture an opinion on impedance differences that would exist 
between the three processes? 
3. Does our current spec seem unreasonable or difficult to manufacture? 
4. What about if the hole was specified as .033 +/- .002?
     
Thanks!
Michael Branning
Avtec, Inc.
4335 Augusta Hwy
Gilbert, SC 29054
(803) 892-2181
(803) 892-3715 FAX
[log in to unmask]
     
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