Hi Rob,

     I guess the first question would be what type of epoxy are you using? If
it's loctite, and it's 3609, the strength at high temperatures passes the test
they use to qualify it as a SMT adhesive for wave soldering, but there are
other loctite epoxy formula's that have much higher percentages of the cure
strength at elevated temperatures than 3609 does...the reason I jumped on 3609
first is because that's what a lot of people use.

     At 150 degrees C., 3609 only has about 10% of it's normal cure
strength...enough to qualify as a SMT adhesive, but may not be enough for your
application. I imagine that little puppy you're putting on the backside gets a
little hotter, a lot quicker than a regular ol' resistor or capacitor does...
does solder wet to the whole component? Maybe the wetting forces are enough to
overcome what little strength is there.

     3612, and 3614 are two formula's that retain near 70% of it's cure
strength at 150 C., but it's designed for stenciling according to Loctite
spec's...so it may not perform well if dispensed. By the way, you can check
all the spec's at Loctite's WEB page;

www.loctite.com

     One last comment, there must be a reason that you're using iron/nickle
jumpers huh? High power or something like that? But if there's no special
reason, just use zero ohm resistors...or even better yet, if you can change
the board there's two ways you can put something there to avoid having to
place anything there at all.  One way, is that if you have to place a jumper
at almost all of the jumper locations on the assembly, why not design a trace
in to connect the two pads and then use an exacto knife or a dremel to
configure the few jumpers that ARE supposed to be open.

     One other idea is to design the two jumper pads close enough together and
in such a way that they bridge when they go across the wave, but won't bridge
if some epoxy is dispensed and cured at the centroid or a apex of whatever
pattern you want to put there...they could be pads, or some sort of trace
pattern. At least you wouldn't have to worry about putting a part there...

                                                Just a few thoughts...

                                                   -Steve Gregory-

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