Hi Jerry -
     
     The reference I have always used is the ASM Metals Handbook, Volume 8, 
     8th edition, titled Metallography, Structures, and Phase Diagrams. 
     Look on page 330. The binary phase diagram for tin/lead shows the 
     eutectic at 61.9% Sn. This diagram is credited to M. Hansen 
     "Constitution of Binary Alloys", 2nd edition. I know that within the 
     last year ASM has put out a much heralded revision to Pearson's phase 
     diagram compilation that corrected many of the binary phase diagrams 
     but I don't think that they found any errors in the Sn/Pb diagram. Hey 
     TechNet - anyone else know of a different published eutectic point?
     
     
     Dave Hillman
     Rockwell Collins
     [log in to unmask]


______________________________ Reply Separator _________________________________
Subject: Re: Sub: Solder Paste Plastic or Eutectic
Author:  [log in to unmask] (Jerry Cupples) at ccmgw1
Date:    11/23/96 2:25 PM


Dave, you said:
     
     
>     The true
>     eutectic for tin/lead is 61.9%tin/38.1%lead (183C)- everyone calls 
>     63/37 or 60/40 eutectic but they are really near eutectic alloys.
     
Hmmm.  I have seen dozens of references which show 63.0%/37.0% to be the 
eutectic composition for tin-lead binary alloys, and this is the first time 
I've seen otherwise.
     
Anybode got a new edition of Hansen? I'd like to see confirmation, 
otherwise I'll keep my solder post as close as possible to 63% tin. We'd 
all be able to save some money if you are!
     
     
regards,
     
Jerry Cupples
Interphase Corporation
Dallas, TX USA
http://www.iphase.com
     
     

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