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
SiliconForest
Electronics
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