Barbara,

Cleaning under BGAs is delicate business.  While DI water is an effective
cleaning agent for water soluble fluxes, you can get better cleaning results
using a low-concentration cleaning solution.  The cleaning agent helps in
three ways: 1) it will only help in removing non-ionic contaminants that the
DI water will not 2) it will help dissolve / loosen contaminants via
chemical vs mechanical action, and 3) it will help reduce surface tension of
the cleaning solution which is very helpful in getting flushing under low
standoff components like BGA's.  Much of the cleaning action is a fine
balance between the high pressure impingement and the low pressure high-flow
that helps flooding under components.  Lot's of industry debate on this...
You should perform an ionic cleanliness test as a minimum to verify your
cleaning effectivity.


Kevin Glidden
Manufacturing Engineer
Astronics Luminescent Systems Inc.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Barbara Burcham
Sent: Friday, November 03, 2006 10:41 AM
To: [log in to unmask]
Subject: [TN] What to do with a 9 pin .5mm BGA?

We have a 9 pin x .5mm BGA that reguires connection as shown.

The pins are tied together as shown. The soldermask on our first run was
encrouched onto the pads.

This caused the pads to have a eliptical shape instead of a nice round
shape. We did have to do some hand rework on some of

these (arg..boo. hiss).

Questions

1.      Anyone have experience with these that can share what you are doing
for successful fab and assembly?
2.      We are using de-ionized water and water soluable flux to clean
these. Is this the best way to get these cleaned under the part?




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