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November 2005

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Subject:
From:
Jeff Brown <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Jeff Brown <[log in to unmask]>
Date:
Tue, 22 Nov 2005 16:46:22 +1100
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Hi Everyone,

We have a problem with a fairly unique component that requires soldering
to a PCB. I'm really hoping that someone has seen this before as it
looking really awkward.

The component is mounted on a piece of fiberglass about 25mm x 16mm. The
footprint consists of a ground pad which takes up 95% of the area, and
four signal pads with 0.5mm clearance from the ground pad. 

The manufacturer recommends a grid of stenciled paste for the ground pad
due to the large area, but we are concerned that if the paste melts from
the outside edges in, then it will at a minimum result in flux
entrapment, and at worst, the trapped flux will boil and lift the
component, or move the molten solder causing shorts to the signal pads.

I imagine that even if we used solid paste pattern that this would
probably only make the problem worse.

Or are we just being overly pessimistic?

Any thoughts on options would be gratefully received...  Currently
wondering about the possibility of applying BGA balls to the package so
that there is some clearance between the board and the component.

If anyone is interested, I can send the component datasheet to them
directly.

Thank you all in advance

Jeff Brown and Josh Vear
EOS Space Systems

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