Jack:

In addition to the galvanic effect, you have to worry about fretting corrosion. 
The tin that is exposed to the air will oxidize and produce tin oxide.  The 
micro-vibrations found in any office environment are suffient to allow growth of
this oxide surface between the gold and the tin-lead surface.  Eventually this 
corrosion will to an intermittent or an open situation.  It is extremely 
difficuilt to detect this problem since removing the device wipes it clean of 
the oxide and reinsertion shows no problem.  Bell Laboratories did some 
extensive studies in the early 1980s and this was then carried over as a 
requirement to the Bellcore Physical Design Requirements.

Harry


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______________________________ Reply Separator _________________________________
Subject: Re: assy:compatability gold vs tin/lead
Author:  [log in to unmask] at SMTPLINK
Date:    5/22/96 1:13 PM


     Good morning Jack!
        I have several articles in my references that describe both 
     acceptable use and disastrous use of tin/lead pins in gold sockets. I 
     think the key word you used is "potential". In the right environment 
     (moisture - not necessarily water) you will have problems because of 
     the galvanic effect of tin on gold. If things stay dry then you may 
     have no problems. For a battery to form you need two dissimilar metals 
     and an electrolyte - take away one of the three and you avoid 
     problems. Look at your environment and see if moisture would be a 
     concern. Also look at the ASM Metals Handbook Vol. 13 Corrosion for 
     additional information.
     
     
     Dave Hillman
     Rockwell Collins
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______________________________ Reply Separator _________________________________
Subject: assy:compatability gold vs tin/lead
Author:  [log in to unmask] at ccmgw1
Date:    5/22/96 11:11 AM


     
We have instances where tin/lead coated pins are inserted into gold plated 
sockets, etc.  Components even have gold/tin-lead or gold/tin interfaces, 
such as an IC socket with a gold contact with a tin sleeve.  Mil-Std-889B 
indicates gold as being incompatable with tin or tin/lead.  Has anyone 
looked into this issue and is there a potential for corrosion formation and 
associated problems?  Again, I just refereing to mechanical contact ( not 
soldering ).
     
Thanks,
Jack Tippit
Wilcox Electric
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