In a message dated 2/3/99 11:11:35 AM Pacific Standard Time, [log in to unmask]
writes:

<>

Hello Brian!

     I guess I'd give a shot at your questions seeing how there's no math
involved (BOY! Am I ever embarrassed!) But the first thing I'd ask is if their
solderpaste deposition is what it needs to be based on the pad sizes that are
used for the devices. If I may ask, how fine is this pitch? Is there
soldermask dams between the pads?

     As far as the parts shifting from "power loading", I've not been so lucky
to experience that, except for a time or two when I've had to hand load some
fairly populated proto's and the paste has dried quite a bit...you can deal
with the touch-up on just a few boards when that happens. It would seem to me
that as long as the paste isn't dry, and the part is placed accurately, and
deep enough into the paste (not just set on top of it) it really shouldn't
move even if there's a slight jolt here and there going down the conveyers...I
might hedge a little in my answer if the part is ceramic, or if it's a PLCC,
but QFP's usually stay where they're put...

Going from I/R to convection really should make things easier. It should be
the other way around, that is; he was experiencing bridges before with I/R,
but go away with convection...at least that's what I remember when we switched
ovens at one company I worked at. I've only had a chance to go through that
once, every place else I've worked used convection ovens exclusively.

I'd almost bet that it has something to do with the solderpaste deposition
and/or footprint of the part..

-Steve "I'm no math whiz" Gregory-

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