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November 2004

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Subject:
From:
"David D. Hillman" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Wed, 10 Nov 2004 08:01:20 -0600
Content-Type:
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Hi Steve! Reballed area array components (BGAs, CSPs, FCs) are also
appropriate for Class 3 products provided a strict procedure is followed.
We have created an internal process procedure, using either preforms or
mini-soldersphere placement equipment, to reball components that are
critical in terms of cost or schedule. Issues such as moisture content,
thermal processing impact, ESD,  and solderability need to be addressed in
the procedure but utilizing reballed area array components is achievable
for the Class 3 world too.

Dave Hillman
Rockwell Collins
[log in to unmask]




Hi Les!

There are a number of systems out there for BGA re-balling. Some use
mini-stencils to print paste, or flux on to the BGA, then use a template to
locate
the spheres on to the BGA pads.

Then there is a system that utilizes BGA pre-forms that have the  spheres
imbedded into a water-soluble paper for whatever pattern BGA you  have that
makes
things pretty easy:

_http://www.winslowautomation.com/bga.asp_
(http://www.winslowautomation.com/bga.asp)

This link will detail to you all the steps that are used to  re-ball a BGA.
They also perform this as a service.

That being said, for class 3 product, I would be a little hesitant to use
re-balled BGA's, because of all the thermal cycles that the part is going
to be
subjected to. The first cycle is the intial reflow cycle during assembly.
Then  the part is going to be removed, the second cycle. The BGA's pads
will need
to  be cleaned-up to remove the old solder so that new spheres can be
attached, a  third cycle. The spheres will then need to be attached, a
fourth cycle.
Then the  device will have to be attached to the assembly once again, a
fifth
cycle.

I know that with some of the latest Xilinx BGA's where the cost can make
you
cr*p your pants ($2500+), wanting to salvage them becomes a real
consideration. But, with all the thermal cycles that you will be putting
these  parts
through during the re-balling and BGA re-attachment process, I  would be
hesitant
depending on them during critical applications where  their function is
vital.

All the above is for eutectic sphere BGA re-balling. For high lead content
spheres (such as those on Ceramic BGA's), I have no knowledge. I do know
that
the previous link I provided, will direct you to the same  re-balling
service
that offers that as well...it's not cheap.

The only time I have re-balled BGA's and used them is with class 2
commercial product... never with class 3.

-Steve Gregory-

November  9, 2004

We have an OEM who has some de-laminated PWA'S with some BGA'S  installed.
He wants to salvage the parts and have them re-balled.   I have no direct
experience in this area.  How does one re-ball a  BGA?  What types of BGA
can be
re-balled?  What are the pros and  cons on re-balling?  Is this an
acceptable
repair method for Class 3  product?

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