Hi Jan!
     
     I can't begin to list the bismuth references that would help you out 
     but I can fill in some info. Bismuth solders have been used around the 
     industry for a long time. Most of the uses have been in select 
     applications and not on a broad scale. Roger Wild of IBM lead the 
     charge with implementing a wave soldering operation with 42Sn/58Bi and 
     I think it was Unisys in Minneapolis that was doing a similar process 
     on a huge (30 some layer) computer mother board. I have not heard of 
     any other "mass" operations. One drawback of using a Bi alloy is that 
     if you solder to a surface that contains lead (Pb) you have a chance 
     of forming a Pb/Sn/Bi phase that melts at 96C resulting in 
     "hotshortness" which makes the solder joints go to pieces. The NCMS 
     Lead Free Study that will be published soon has some great information 
     on the performance of Bi alloys with both thermal cycling and process 
     data. I can't disclose those results prior to the release of their 
     report but let's just say bismuth can cause you some serious problems 
     under different conditions. I know of several applications of alloys 
     50Sn/40Pb/10Bi and 43Pb/43Sn/14Bi that are working very well but one 
     caveat - the max temperature the assembly is exposed to is 95C. Give 
     me a call and we can discuss the topic of Bi further.
     
     
     Dave Hillman
     Rockwell Collins
     [log in to unmask]
     319-295-1615
     


______________________________ Reply Separator _________________________________
Subject: ASSY: Bismuth Solder
Author:  [log in to unmask] at ccmgw1
Date:    7/30/96 5:39 PM


     
We have a customer who wants to use Bismuth solder (20% bismuth, 40% tin, 
40%lead) on one of our products.  He wants to solder a stranded wire to a 
thin silver surface (commercial job) and believes that the lower melting 
temp of bismuth solder will aid his process (we normally recommend SN62). 
  He asks if I know of any problems with bismuth attacking silver. (if it 
has any sulphur in it, it will).  I have never used bismuth solder and don't 
recall reading anything recently about it.  Has anyone had any experience 
with it and what are the drawbacks if any??   Thanks.
     
Jan Satterfield
Edo Corp
[log in to unmask]
(801) 486-7481 ext 315
     
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