Hi Max -
     
     Gold and tin do mix in solder! The solubility of gold in tin is quite 
     high and the reaction happens very fast (the gold doesn't 
     evaporate).Give me a call off-line and I can give you some data 
     sources showing the mechanics of what happens. Your right - there are 
     military (and commercial) studies showing the problem with gold in the 
     solder joint but the mechanism of what happens is different than what 
     you described.
     
     
     Dave Hillman
     Rockwell Collins
     [log in to unmask]


______________________________ Reply Separator _________________________________
Subject: RE: ASSY: Pre-tinning of Gold Leads
Author:  [log in to unmask] at ccmgw1
Date:    1/15/97 10:23 AM


Gold and Tin do not mix in Solder.  In fact, studies done by the 
military actually show a degradation in reliability for gold plated 
parts that have been soldered into a board.  My guess is that when the 
vendor tins the gold leads, the gold evaporates and you would be hard 
pressed to find any of it even if you scraped the tin off.  Therefore, 
the guidelines that I would follow would be the industry standard on the 
thickness of tin plated leads of components
     
Hope this helps
Max Bernhardt
Woodward Governor Co.
     
 ----------
From: Rajan, Sanjay
To: technet
Subject: ASSY: Pre-tinning of Gold Leads 
Date: Tuesday, January 14, 1997 1:45PM
     
     
Technetters
     
We use a lot of components that come with gold plated
leads (gull wing, J-leaded, castellations..).  We are currently 
asking our vendors to pre-tin these leads if possible and one 
such vendor wants to know the exact mil-spec that he can
look up to know the thickess of the tinning that is required.
     
Can anyone point me to the exact document that spits out 
recommended tinning thicknesses based on the thickness 
of the gold on the lead??
     
Thank you
________________________________________________ 
Sanjay Rajan        RF Communications Division 
Harris Corporation  Product Design Engineering 
1680 University Avenue   Phone:    (716) 242-3923 
Rochester, NY 14610 Fax: (716) 242-3174 
________________________________________________
     
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