Ron, Ted, Earl & others,

     For more information on buried capacitance, please access
     www.hadco.com and click on the "Technology" button and then the "BC
     Design" button (www.hadco.com/bcdesign.htm).  Follow the links through
     the various sections of the BC Design Guide.

     Both "BC-2000" and "EmCap" are copper clad core materials that can be
     used to create distributed capacitance power/ground core pairs.
     BC-2000 (.002" thick ply of glass/epoxy dielectric) has a nominal bulk
     capacitance of 500 picofarads per sq.in.; EmCap (.004" thickness of
     ceramic filled epoxy) has a nominal bulk capacitance of 2.7 nanofarads
     per sq.in. At least 16 PWB fabricators are licensed to build boards
     using BC-2000 material. EmCap material will be similarly licensed.

     Please feel free to contact me off-line for further discussions.

     Dave Wolf, HADCO Field Engineer
     612/893-1466
     [log in to unmask]
______________________________ Reply Separator _________________________________
Subject: Re: [TN] Buried Capacitance
Author:  "Edwards; Ted A (AZ75)" <[log in to unmask]> at
SMTPLink-Hadco
Date:    7/31/98 11:21 AM

Saw a presentation on it when they were Zycon, of course now they are HADCO
The presentation showed 5 patents:
5079069
5155655
5161086
5261153
As I remember it; it is a sheet capacitance only.  I think there are design
implications as it I believe adds two layers to the board.  Perhaps someone
from  there could give a summary on the TechNet .
 ----------
From: [log in to unmask]
To: [log in to unmask]
Subject: [TN] Buried Capacitance
Date: Friday, July 31, 1998 7:05AM

Buried capacitance material is available from many major laminate, core,
and prepreg suppliers. There is a patent (number unknown to me) assigned
to the process and material. Several Zycon engineering personnel were
responsible for this invention. One is currently with Praegetzer as an
engineering executive (name also unknown to me) and provides technical
information about this material's use.

Simply, the material is a thin laminate with specified dielectric
thicknesses providing the required capacitance in impedance controlled
printed circuitry. At the design level, engineers and designers may
select the desired capacitance and design in the material. No special
considerations are necessary but for unique design needs. This is true
both at the design and fabrication level.

Earl Moon

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