You might try Loctite 3609 or Ciba Geigy 7275.  We have had some 
     success with these products curing before reflow in a similar 
     situation as yours.
     
     Linda Kenison
     Vicor
     (508)749-7570


______________________________ Reply Separator _________________________________
Subject: Assembly
Author:  [log in to unmask] at Internet
Date:    2/12/97 10:40 AM


I have an application where we are bonding leaded SMT parts (Ceramic & 
Plastic QFP and Flatpacks) using a contact adhesive (double-sided) tape 
because it is easy to apply and doesn't require a heat cure. 
Unfortunately, the tolerance stack up causes conditions where bonding 
cannot be assured.  Also, when these adhesive are subjected to the high 
temperature of the convection reflow oven the thickness increases 
temporarily causing the part to lift, the solder soldifies, and the tape 
thickness returns to it's original thickness.
     
We tried changing to a film adhesive, but have not been able to find one 
that could be cured during the reflow solder process.  The temperature 
profile is not sufficient to cure these materials and we can't subject 
the assembly to an oven cure because of the solder paste that has 
already been deposited.
     
Does anyone have an adhesive material that has been demonstrated to cure 
during a typical reflow solder profile, that comes in eather a preform 
or a dispensible paste/liquid?  Also, does anyone have a similar 
situation in which they solder the parts first and then inject adhesive 
through an access hole later, followed by a cure step?  If so, how has 
it worked out.  We don't like to add secondary processes, but I don't 
see much alternative.
     
Thanks,  Peter H. Cote
     
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