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1995

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From:
"Jay Edwards" <[log in to unmask]>
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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  From: [log in to unmask] (R_R_HOLMES)
  Original-Date: Wed May 24 10:18:06 EDT 1995
  Phone: (804) 226-5114
  Subject: Re: single ply dielectric and "green" laminate
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  In-Reply-To: your message  of May 22 18:28:11 EDT 95
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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
 F



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