No disagreement here...
jk
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Douglas O. Pauls
Sent: Friday, December 17, 2004 9:16 AM
To: [log in to unmask]
Subject: Re: [TN] solder mask/conformal coating compatability
Joyce,
Yes, I do extractions on actual product. It is non-destructive. I compare
it to the product specific burn in test results. Over time I get a good
feel for how clean our various products are and how that translates into
functional performance.
I draw a distinction between lab based tests that most of us use for
materials compatibility testing, and product-specific life tests or burn in
tests. My lab based tests can usually be done cheaply and off-line, giving
me some measure of comfort that when these materials are used together on
expensive product, they will work. Perhaps it is our conservative nature
as a hi-rel OEM, but we would not dream of making a significant material
change without manufacturing some test units and doing qualification tests.
When I was a consultant, I lost track of the number of times a manufacturer
took two "known good" materials and produced horrid product because the
process was screwy. As Gregg Klawson points out, there are not guarantees
that Product A works with Product B in a manufacturing process. That is
why you must verify a material change on actual product.
Doug Pauls
"Joyce Koo"
<[log in to unmask]
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12/16/2004 04:08 <[log in to unmask]>,
PM <[log in to unmask]>
cc
Please respond to Subject
<[log in to unmask] RE: [TN] solder mask/conformal
com> coating compatability
Doug,
are you telling me you do not do the ionic extraction on the real assembly?
sufficient cleanliness test? use needles extract the liquid from
underneath
the components (low profile new components only) for IR? I would avoid do
any test possible on the assembly... except non-destructive: like
extraction...But, as you possibly right, what I like is not
"respected"...If
you got burned by organometallic catalyst activated coating, you will be
able to get some clean assembly with good adhesion...
Things get messed up when someone want standardize all conformal coat cross
different products...lets just don't go there...
jk
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Douglas O. Pauls
Sent: Thursday, December 16, 2004 3:34 PM
To: [log in to unmask]
Subject: Re: [TN] solder mask/conformal coating compatability
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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