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September 2004

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Subject:
From:
"Tempea, Ioan" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Tempea, Ioan
Date:
Wed, 1 Sep 2004 10:46:39 -0400
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text/plain (34 lines)
Hi Technet,

I have this application: a 1.100" x 1.100", regular FR4 PCB, that has to be
solder bumped on one side and has SMT components on the other side. The PCBs
to bump are not singulated, but in panels 18-up. Once bumped and
depanelized, the bumped PCBs will be soldered like a BGA on top of another
FR4 PCB. The standoff between the main PCB and the VCO shall not be higher
than 0.022", therefore 0.022" is the max height of the bumps after
collapsing. The minimum standoff has no physical restriction, but the higher
the better, easier to wash. The pads that have to be bumped are approx.
0.075" in diameter, same as the pads on the main PCB, a count of 52 per PCB.

Do you have any experience with this kind of operation?

I will probably use a thick stencil, according to the area ratio
calculations it should be about 0.028" thick. According to my stencil
supplier, it is doable, they can get the foil.

Any experiences with thick stencils? What about the paste, will it slump?
Shall I cut 100% of pad dimension, or need a reduction?

Thanks,
Ioan

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