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December 2004

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Subject:
From:
"Douglas O. Pauls" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Thu, 16 Dec 2004 14:34:08 -0600
Content-Type:
text/plain
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text/plain (60 lines)
Joyce,
I must disagree with your position that materials compatibility testing
should not be done on production hardware.  In my opinion, it is a serious
oversight if you do NOT do such testing.   Most testing is done on flat
boards, like the B-24 or B-25A, because such substrates are cheap, easily
available, have industry standard evaluation criteria, and do not take up
time on production equipment.  I might take a B-25A board, made by my
chosen fabricator (Collins Printed Circuits to put in a shameless plug),
apply my chosen mask, run through my chosen reflows, fluxes and cleaning,
coat it and test.  That may be enough if all my boards are dead flat, but
ours here have these nasty 3D objects called components that give rise to
all kinds of variations (err. or so I've heard happens elsewhere).  Being a
hi-rel hi-mix shop, there is an incredible array of profiles and function.
How can you assure that your material set works on a product family or
verify that a change in materials or processes is not detrimental unless
you fully check out form fit and function on actual product?

Doug Pauls




             Joyce Koo
             <[log in to unmask]
             com>                                                       To
             Sent by: TechNet          [log in to unmask]
             <[log in to unmask]>                                          cc

                                                                   Subject
             12/16/2004 12:44          Re: [TN] solder mask/conformal
             PM                        coating compatability


             Please respond to
             [log in to unmask]
                    om






material compatiability study should not be done at production level.  Why
you are doing it on the populated board? If you done the work at front (in
the design stage as part of material selection), you should not see the
need
to do it at production level.
Why?
                               jk

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