Re: Re[2]: [SI-LIST] : Decoupling capacitor selection & plac

Ravinder Ajmani (ajmani@us.ibm.com)
Fri, 31 Oct 1997 11:50:47 -0500

I have been studying the effects of increased power/ground capacitance =
on noise
and EMI, and also to determine if I can use this option to reduce the n=
umber of
capacitors on the board. I have used FR4 with thickness of 3 mils, and=
also
Zycon material, which is 2 mils thick but is still FR4, and hence doesn=
't
provide enough capacitance to make any significant difference. I have =
inquired
with our raw card fabricators and none could provide me any details abo=
ut high
dielectric constant material.
I will be interested in using the EmCap material in my experiment. I wi=
ll
appreciate if Todd can inform me who in California has the capability t=
o
fabricate boards with this material.

Regards, Ravinder
EMC & Signal Integrity Engineer
PCB Development and Design Department
Voice : (408) 256-7956 T/L : 276-7956 Fax : (408) 256-0550=

Email: ajmani@us.ibm.com

owner-si-list@silab.Eng.Sun.COM
10/29/97 05:11 AM
Please respond to owner-si-list@silab.Eng.Sun.COM @ internet

To:
cc: si-list@silab.Eng.Sun.COM @ internet
Subject: Re[2]: [SI-LIST] : Decoupling capacitor selection & placemen

How does everyone feel about power/ground distributed capacitance?=

Zycon originally developed ZBC2000 - a thin FR4 (.002") power/grou=
nd
core with a capacitance of ~500pf/sq in (usually 2 cores are used)=
-
as a decoupling capacitor replacement or adjunct.

HADCO and Polyclad have developed EmCap - a 0.004" Ceramic / FR4 e=
poxy
power/ground core with 2750pf/sq in - as the next generation.

I have been doing work to predict the ability of both these produc=
ts
to replace discrete capacitors in our customers boards and would l=
ike
to hear some honest thoughts and feedback.

FYI - I'm an EE working at HADCO. I work with the electrical issue=
s in
PWB - impedance, capacitance, layout, etc. - more or less in house=
SI.

Thanks!
Todd DeRego

=