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February 1997

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From:
"ddhillma" <[log in to unmask]>
Date:
Wed, 05 Feb 97 11:56:20 cst
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     Good Morning!
     
     Send me your fax number and I'll send you the Pb/Sn/Ag ternary phase 
     diagram (are you sure you really want to read it!). Do you want a 
     particular isotherm? I understand the direction you are coming from 
     for the melting point but I think the practicality of it is a stretch. 
     To have some predictability you would need the "system" which would be 
     the composition of the added solder plus the base solder to be fairly 
     set, solder volume quantities fixed, temperatures involved stable, etc 
     - none of these factors are easily controllable on the manufacturing 
     floor and/or would cost quite a bit to be controllable. Also depending 
     on how long the solder joint is in the liquid state you would have 
     several diffusion reactions occurring simultaneously which would be 
     really fun to predict! Consider soldering to a gold surface - if the 
     solder joint composition moves toward the gold/tin side of the ternary 
     you would expect the melting point to go up but folks solder to gold 
     everyday on product without having a problem. Let me know your fax 
     number and Good Luck!
     
     
     Dave Hillman
     Rockwell Collins
     [log in to unmask]


______________________________ Reply Separator _________________________________
Subject: ASY: Alloy contamination
Author:  [log in to unmask] at ccmgw1
Date:    2/5/97 10:38 AM


     
     
     
     Here's one for the metallurgist. I have been unable to locate a 
     Pb93.5/Sn5/Ag1.5 (305C liquidus; 309C solidus) ternary phase diagram 
     to date. I have been told that one of the technical issues is simply 
     soldering to SnPb plated and/or SnPb hot-dipped coated components with 
     this PbSnAg solder will realize a drop in the melting point. My 
     question is how much ? Assuming, for instance a lead finish 
     composition of Sn63/Pb37 with solder coat thickness of 3 to 4 mils or 
     a CERDIP package with leads that are 100% Sn electroplated (200 to 
     500micons).
     
     
     
     
     
     
     
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