Good day TechNet!
I'm looking for recommendations today.  I need an adhesive that I can dot
dispense on circuit boards (Dispense head on a GSM-1) and cure in the same
oven profile as a solder paste reflow profile.  I've got a couple of parts
that need a bit of extra grip on the board (for vibration resistance).  The
parts are SMT paste attached, so the glue will have to cure at the same
time as the paste reflows.

*Graham, I recommend that you NOT take this approach.  At CSL, we saw a
number of cases where this practice caused metal migration and other
assorted failures under SMT components.  The problem lies in the fact that
at one point you have a semi-cured plastic material (the adhesive) and hot
flux residues from the paste.  They can combine to form a non-removable
residue or undesirable changes in topology of the adhesive structure.  In
addition, a solder reflow profile may be much more aggressive than those
recommended by the adhesive manufacturer for adhesive cure.  If you cure
the adhesive too fast, you can get a skinning effect on the adhesive,
entrapping volatiles that then blast their way out other places, leaving
voids to suck in flux residues.  For whichever adhesive you pick, look at
the recommended cure profile and compare to your reflow profile.

Doug Pauls
Rockwell Collins

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