Hello Jeff,
We had similar components short time ago, and we create a grid in the
aperture of the stencil, similar to what Ivan suggested. The reflow pass
well, but after examine the component with X-ray we saw air trapped in
the solder (about 20% of the area). Thus, I suggest designing the pad on
the PCB the same way as the grid in the stencil.
Regards,
Gil Zilber
Technologist, Elta system Ltd.
Tel. +972-8-8577240
Mobile +972-54-4983222
http://www.iai.co.il/site/en/iai.asp?pi=17887
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Jeff Brown
Sent: Tuesday, November 22, 2005 7:46 AM
To: [log in to unmask]
Subject: [TN] Unusual soldering challenge
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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