Hi Steve - just add one more vote to the rest of the chorus for using xray
on a SPC basis. As others have mentioned we are using a "middle class"
system on a sampling basis to check for placement and solder density
aspects of the BGAs. The critical inspection point is the solder paste
print which is also on a sampling plan. One interesting aspect of having a
simplistic piece of xray equipment on the floor in a sampling mode (rather
than a mandated inline mode)  is that other issues can also be "checked"
very quickly (e.g. solderballs, slivers, foreign material, etc. ). Good
luck with the survey.

Dave Hillman
Rockwell Collins
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"Stephen R. Gregory" <[log in to unmask]> on 10/01/98 09:54:11 AM

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
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To:   [log in to unmask]
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Subject:  [TN] : Assy: Xray Utilization




Good Day All!

     I was asked a question by the GM the other day about X-ray that maybe
I
can get some input on. The higher ups have been thinking about whether or
not
we need to purchase an x-ray machine. We do have sources here in Silicon
Valley to take assemblies for x-ray...at anywhere from around $75.00 a
board,
up to what's called "minimum lot charges" of $750.00 by vendors that want
long
term contracts with you.

     We're a start-up contract assembly company, and just like any start-up
we
need to be pretty frugal until we get ourselves established. As most of you
are aware, BGA's are becoming pretty commonplace, micro-BGA use seems to be
rocketing...at least on the new designs I'm seeing. So that does create a
need
for x-ray, and I might add, as a process verification tool, not a process
control tool.

     The GM asked me a how often would I use the x-ray if we had one, and
with
the assumption that we've got our processes under control and are able to
set
a job up repeatably..."Good question..." I told him. He told me to think
about
it and give him my answer sometime this afternoon.

     So my question is, those of you that are rich enough to have x-ray,
how
do you utilize it? Random sampling plans? Or is it's use triggered by
something else? I know I would use it during the intial set-up of a
process,
but I'm not really sure how I would use it on mature processes. If I'm
doing
my job right, I've got the process that I verified during the initial
set-up
under control and being monitored, so why would I need xray?

Thanks in advance!!

-Steve Gregory-

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