Hi Pat -
     
     We are using the Sn43/Pb43/Bi14 alloy on one product with very good 
     success. The low melting point helps avoid some thermal shock issues 
     we have on the assembly. One word of caution - the Sn43/Pb43/Bi14 
     alloy forms a low melting point at approximately 95 C which causes the 
     solder joints to fall apart. In our application the product never goes 
     above 80C in its use environment so the use of the Sn43/Pb43/Bi14 
     alloy is feasible. Take a look at your product in its use environment 
     with the temperature excursions in mind to see if you will or will not 
     have problems. I would also recommend that you set up a specific 
     soldering process around the alloy to prevent it from accidentally 
     "migrating" to other areas of the manufacturing process.  Good Luck.
     
     
     Dave Hillman
     Rockwell Collins
     [log in to unmask]


______________________________ Reply Separator _________________________________
Subject: ASSY: Sn43/Pb43/Bi14 solder
Author:  [log in to unmask] at ccmgw1
Date:    7/9/97 8:43 AM


Hi there,
     
Is anynoby in PCB assemblers using Sn43/Pb43/Bi14 solder paste as primary 
or secondary process (to reflow heavy components on double-sided PCBs)??
     
Is it enough reliable. Having in mind that is it a non-eutectic alloy , will 
the rework be a challenge vs Sn63/Pb37 and how is the post-reflow inspection 
? What is the recommended surface finish of the PCB to achieve proper 
wetting results? Would HASL finish be acceptable to support or wett the 
solder? Is there intermetallic formation at the joint Pb/Sn/Bi and HASL 
finish? How is the strength between both?
     
I saw a article in the september 1996 publication of SMT MAGAZINE but I 
need comments from assemblers. If you have any documentations or documented 
works (qualification, reliability test results as thermal cycling, thermal 
shock, humidity cycling and X-section & surface analysis for that alloy vs 
Sn/Pb would be very appreciated.
     
I know that there is a lot of answers asked, thanks in advance for your 
responses and your sharing.
     
Regards.      =20
------------------------------------------------- 
Patrick Ducas
Process Quality Engineer=20
Matrox Electronic Systems Ltd
E-mail: [log in to unmask]
T=E9l:(514)969-6000 ext.2971   Fax:(514)685-3415 
-------------------------------------------------
   =09
     
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