Hello Again Werner:
I sincerely appreciate your consideration of my proposal that coupons
specific to LF performance be considered as part of the PWB and PWA quality
lexicon. I apologize for the length of my response but I am very interested
in your continuing views on this subject. To that end I offer the following:
Specific to what would benefit coupons would offer, the clear directive
would be to have a clearly defined test methodology stating unequivocally
that the laminate will withstand the LF processes of the respective
assembler.
For this particular point, the obligation for LF compliance must first rest
with the laminate manufacturer. The spec sheets must be true in their
statements that the Tg and Td call outs are exactly as advertised and that
coupons from the particular lot be provided to the fabricator at time of
purchase.
Secondly, the fabricator must thusly provide coupons (if requested) for
customer review (much like the old mil-p-55110 as I recall) that would show
the boards have been laminated/processed correctly and will in fact
withstand the subsequent demands of LF soldering. This takes into account
the different types of laminate a customer may require for its end product
whether it is 2layer, multi-layer, flex or flex-rigid.
Lastly, and finally, the CM/OEM must also test their own specific process
using coupons provided from the same lot the fabricator used to ensure the
re-flow process is in line with the laminate's stated capabilities as
mentioned earlier.
There are two wild-cards at the assembly level...the type of components
utilized and the temperature required to re-flow them, and, the method of
re-flow (hot-air/IR/solder-reflow) utilized. However, that is why the
assembly resources would be well served to test these coupons prior to
assembly to ensure their particular process will not be outside the
parameters of that the designers designed in.
Therefore, It is my considered view that now more than ever a co-operative
engineering strategy be employed that includes fabricators and assemblers
when determining laminate choice within product design. This of course is
the "HARD WAY" which takes more time and probably some additional cost
however the pay-off will be substantial in quality product, reduced defects
and a happy customer.
In comparison, no one thought before today that oil recovered from oil
sands/shale could be done economically unless the price per barrel was at
$60/bbl. That is where oil is today; $60/bbl! and the USA has (as I have
read) over 150 years of oil sands reserves which is now being considered for
our future needs. In comparison, With the advent of RoHAS and LF, it may
finally be economical for the electronic designer and supplier to finally
come together for co-operative engineering as it has now become cost
effective to behave in this way.
Charlie McMahon
McMahon Sales Company
P.O. Box 1024
Windham, New Hampshire 03087
Tel: 603-432-3111
Fax: 603-432-6854
Cell: 603-401-4646
e-mail: [log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Tuesday, December 13, 2005 10:00 AM
To: [log in to unmask]
Subject: Re: [TN] Qualification of the Pb-free capable manufacturers
Hi Charlie,
Yes, that would serve. We have "PTH/PTV Reliability Coupons," "Registration
Coupons" and "SIR Coupons"--why not "Delamination Coupons." At this point,
it
is however not clear, at least to me, which PWB design features [lots of Cu,
little Cu, coupon size, etc.] are the most critical in terms of lamination.
But my question is as 'Why should the burden not be on the suppliers?'--they
control the properties of their materials and it should be part of their
data
sheets. Unfortunately, data sheets are made of very uncomplaining paper--I
have found data sheets from large 'reputable' suppliers giving CTE values of
FR-4
material as low as 11 ppm/C when the true CTE when we measured it was almost
double.
Why is it, that in our industry, most of the suppliers are part of the
problem rher than part of the solution?
With this 'Lead-Free' insanity and the lack of resources, we had better all
contribute or face the consequences.
Regards,
Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL 32174 USA
Phone: 386-437-8747, Fax: 386-437-8737, Cell: 386-316-5904
E-mail: [log in to unmask], Website: www.engelmaier.com
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