Hi Ed - 
     
     A question- you said "..had stress lines develop....after convection 
     reflow" - is that after some type of stress testing (thermal, etc.) or 
     literally right after the reflow process. If you are having "stressed" 
     solder joints right out of the reflow process I suspect that you have 
     a process problem or a board/layout design problem. The TechNet 
     traffic has shown that there are quite a few electronic manufacturers 
     that have/are experiencing cracking problems with Alloy 42 TSOPs as 
     part of the stress screening.
     
     
     Dave Hillman
     Rockwell Collins
     [log in to unmask]


______________________________ Reply Separator _________________________________
Subject: cracked solder joints with alloy 42 tsops
Author:  [log in to unmask] at ccmgw1
Date:    10/8/96 2:21 PM


   I would like to send or fill out over the phone a questioneer for all
users of tsops having alloy 42 leads who have experienced problems with 
stressed or cracked solder joints on pwas. We had stress lines  develop in 
solder joints after convection reflow when we had bulbous solder joints. 
Reducing stencil apertures to (19.7 mil pitch) 10 mil width with 50% length 
using a 6 mil thick stencil rather than an 8 mil stencil gave solder joints 
with heel fillets and a 50% toe fillet that survived the reflow process but 
they showed stress lines after wave soldering. Hand solder repair of cracked 
joints appeared to remedy the situation.
     
   E.Louis
   Lockheed Martin Corp.
   11 Federal St.
    OPS-2C
    Camden,N>J> 08102
    phone#:609-338-3508 
    fax #: 609-338-2575
     
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