Steve,
We're
concerned about the solder wicking through to the other side and presenting
"balls" of solder on the second side. This is a 120mil thick PCB and would
take a bunch of extra print strokes to fil the via, then the stencil won't
gasket and would probably be damaged when printing second side, damage by
squeege blades. I like the prevailing opinion:
REDESIGN.
Mark
Hi
Mark,
I hope you've seen my pictures and seen what happened with me.
But something you might try that I didn't think of when I ran my ten boards,
is to do a double print stroke when printing the board...this may "force" some
of the paste down inside the via and give it a bit of additional paste to fill
down inside the via so that it doesn't suck so much from the fillet... maybe
worth a try.
-Steve Gregory-
Group,
I have a challenging assembly that I need some of
your combined professional experience to resolve.
I have been
presented a 120mil-thick polyamide (sp?) dbl-sided PCB, gold finish with the
majority of the C's&R's being 0402's, some 20mil QSOP and TSOP,
QFP. That's somewhat challenging in itself but to compound matters,
there are MANY instances of vias in the SMT pads. The vias go through
the PCB and are NOT tented/plugged. Many of these vias are on only one
side of 2-terminal parts. I don't have the complete set of gerbers and
drill drawing so I can't determine the drill size of these vias.
Is
there ANYTHING I can do at this stage of the game to produce a quality
product in terms of stencil design, reflow profile, etc? The customer
is aware of the potential problems this presents. Their primary
concern is the solder wicking through to the other side. Mine too, in
addition to solder-starving and tomb stoning.
Your thoughts are
appreciated. Oh yeah, of course it's R/F.
Mark
Charlton
Engineering Manager
MSI of Central Florida, Inc.
7703
Technology Drive Ste. 102
Melbourne, FL 32904
(321) 725-0626
x.24
(321) 725-0627
fax
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