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Date: | Thu, 8 Jun 95 13:38:27 EDT |
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Good Afternoon,
I am appending the following for a fellow engineer in my dept. that
does not have the capability to append directly. I will forward any
and all responses to Mr. Ayotte - Thx. In Advance...Jay Edwards
-------------
With respect to the attached ATT response; what I am wondering is:
- what are the voltage applications for the products that ATT
uses single sheet prepregs in?
- is this true for signal/signal, signal/power and power/power
applications?
- what are the reliability requirements for the products this
is being used in (0.1 ppm/KPOH or 10 ppm/KPOH or higher)?
- is this consumer products, games and toys or mainframe?
- what prepreg thickness/thinness does ATT use?
Any and all information is greatly appreciated. Thanks in
advance Stephen Ayotte, IBM MD Quality Engineer
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Subject: Re: single ply dielectric and "green" laminate
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AT&T has been using single ply B-stage for several years and is in the process
of converting all product to single sheet. We have seen no reliability
problems, and believe that a single ply is as reliable as two plies. We are in
the process of converting all products to single sheet (5 mil, 6 mil, 8 mil 10
mil). We also make PCMCIA cards with 2.8 mil single sheet glass.
The only real risk with single sheet glass is the possibility that a
dielectric void could bridge layer to layer through the glass cloth. With
modern PWB processes this is a limited risk. In addition, in some cases, a
tight weave single sheet glass provides a tighter barrier than two sheets of
an open weave. The only field problem that I remember actually occured with
two sheets of an open weave (1080 glass).
In conclusion, AT&T believes that single sheet constructions are very reliable
and we are using them in most of our products.
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Subject: single ply dielectric and "green" laminate
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To what extent has the PCB industry changed to single ply for pre-preg as
opposed to core which has been available in single ply for a long time. What
are the fears about single ply pre-preg? Are 2 plies really better than 1
thickone?
What are the attitudes towards so called "green laminate"? Is it simply a case
of eliminating bromine, is it vital to meet UL V- 0 if the alternative could
have such an impact on the environment?
These questions were prompted by a major user of PCBs in Europe.
George Wheadon Nelco UK
.. º /NO SUBJECT
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