Kevin,

I'm not the SMT guy that most people on this forum are but ....

I would feel uncomfortable leaving a big fat Hersey's kiss of conductive
adhesive under your device....if you could pile it that high.  A large,
thick, section of conductive adhesives (at least the ones I have used for
[bare] die attach) will usually 'mud-crack' .  The conductive adhesives are
not necessarily thixotropic and therefore, may not give you the tall glob
that you desire.  I would be concerned about the potential for silver
migration later....

On the other hand, there are many non-electically conductive adhesives which
are very thixotropic and can very easily give you the large glob which I
believe you desire.

Both conductive and non-conductives are typically available in a snap cure
format, however, the non-conductives will have snap cures most suitable for
SMT types of work.  UV cures too.

Check out the Ablestiks and Loctites of the world

Steven Creswick - Gentex Corporation
Zeeland, MI - USA
-----Original Message-----
From: Kevin Syverson [mailto:[log in to unmask]]
Sent: Friday, April 04, 2003 10:33 AM
To: [log in to unmask]
Subject: [TN] Conductive Epoxy/Adhesive...


Good Morning TechNetters,

I am curious if anybody has experience using conductive epoxies/adhesives to
prevent movement of heavy surface mount devices during reflow (convection
oven, oxygen atmosphere).  We have some heavy double-stacked ceramic
capacitors in a 20 pin DIP package (J-lead configuration) that stand off the
circuit board approximately 0.125", which pretty much precludes the
possibility of using a standard SMT epoxy for securing the body of the
component to the board (at least I think so).  The components have very
narrow terminations with much larger (wider and longer) board lands, and the
parts are shifting off the pads a bit during reflow.  We are using OA solder
paste (Alpha WS609) and I would like to replace the paste on two opposing
leads with something to help secure the component during reflow.  Does
anybody have any experience or maybe some other ideas for this?

Thanks,

Kevin Syverson
Silicon Forest Electronics

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