Buried Capacitance

Howard W. Johnson (howiej@olympic-tech.com)
Mon, 3 Jun 1996 12:10:41 -0700

One point I have heard expressed from my clients
is that, while the *total* buried capacitance
between a full-sized VCC-GND plane structure
may look impressive, the *effective* amount of
capacitance within a circle of say, 1/10 nS of
a chip (that is the area within which the
capacitance has a chance of affecting the
signals associated with a 1-ns rising edge)
is not as impressive. I have also heard
objections based on (rather vague) manufacturing
concerns having to do with reliability.

>Return-Path: <dla@pyramid.com>
>Errors-To: si-admin@silab.Eng.Sun.COM
>Errors-To: si-admin@silab.Eng.Sun.COM
>From: "Don Abernathey" <dla@pyramid.com>
>Date: Fri, 31 May 1996 16:15:21 -0700
>To: si-list@silab.Eng.Sun.COM
>Subject: Buried Capacitance
>
>Hello!
>
>About four or five years ago Zycon Corp began licensing it's buried
>capacitance technology to other PCB manufacturers. The technology was
>simple, a very thin (~2mil) layer of FR4 sandwiched by 1oz copper
>layers. The technology received a somewhat lukewarm reception in the
>industry as the max capacitance per square inch was way lower than
>what people needed for the mean operating frequency and device
>technologies then in vogue. It required about 3 BC stacks to achieve a
>usable capacitance (usable means that all the .001uf and .01uf caps
>went away). I think Zycon showed a technology roadmap where the dielectric
>constant of the laminate material continued to increase over time.
>
>Has anyone out there used BC? Can you give me a little update, from a
>user's perspective, of where BC is going? I would really like to know
>if the qualifications of the higher dielectric laminate materials ever
>finished, or if the FR4 laminate is all they have. Any negative
>experiences with BC? (I ask this because people are always afraid of
>power/ground plane shorts). Any hassles getting the PCB fab yields
>stabilized? Any experience on the usability in general?
>
>Any and all feedback is welcome.
>
>
>
>*************************
>Thank you |
> Don Abernathey |
>(503)690-6234 |
>dla@pyramid.com |
>*************************
>
>
>
_________________________________________________
Howard W. Johnson, Olympic Technology Group, Inc.
U.S. tel (206) 556 0800 // fax 206 881 1491 // email howiej@olympic-tech.com