Hi TechNet!
     
     It sounds like the flux in your solder paste is loosing its suspension 
     properties because of the shearing action during deposition onto your 
     assembly. The flux in solder paste isn't suppose to do that (unless 
     you formulate it too)! I suggest conducting the basic material tests 
     on your paste (viscosity, slump, tack) and also contacting the solder 
     paste vendor. This "spreading" of the flux element of the solder paste 
     has been reported on in the literature (and I have observed it too) 
     but the solder paste flux was breaking down leading to solder defects. 
     Good luck.
     
     
     Dave Hillman
     Rockwell Collins
     [log in to unmask]
     


______________________________ Reply Separator _________________________________
Subject: assy:spreading of paste flux
Author:  [log in to unmask] at ccmgw1
Date:    11/23/96 9:33 AM


Date : 23/11/96 16:56
Msg From: PROCESS ENGINEERING
hello,
we are facing a problem of spreading of paste flux (water soluble 
paste)  on either side of the pad just after printing (contact 
printing using 6 mil laser cut stencil). This is clearly observed 
under 4x magnification, particularly for 20 mil pitch component.
     
     
is there any flux spread test for solder paste .
     
regards
     
nalin
     
altos india ltd.
altos india ltd.
     
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