[SI-LIST] : RE: [SI-LIST] : RE: [SI-LIST] : 回复: [SI-LIST] : Parallel Plate Capacitance for Bypass

About this list Date view Thread view Subject view Author view

From: Dave Hoover (dhoover@mccurdy.com)
Date: Fri Mar 31 2000 - 08:10:02 PST


Those numbers are good. That would be for dielectric breakdown
voltage in the "Z" axis. The electrical strength is around
1300 Volts/mil. Two things to mention here: Surface layers
exposed or covered by soldermask are totally different on
this stuff. The IPC is very conservative with their design
charts on this. The other thing is plane to plane-for dielectrics
below .004" the standard hipot test at 1000 volts may damage
(pierce) the material(s). For example, .002" dielectrics can
pass 500 VDC hipot tests but may not survive 1000 VDC.

Groovy (aka, Dave Hoover)
-----Original Message-----
From: markku.rouvala@nokia.com [mailto:markku.rouvala@nokia.com]
Sent: Friday, March 31, 2000 1:05 AM
To: si-list@silab.eng.sun.com
Subject: [SI-LIST] : RE: [SI-LIST] : 回复: [SI-LIST] : Parallel Plate
Capacitance for Bypass

Rachild,

According to IPC -papers FR4 break voltage should be around
28kV/1mm=700V/mil.
I think the point is how homogenous the materials are, thickness changes in
lamination and possible 'gas-bubbles' in material, if we are talking about
MLB.

Regards,

Markku

> -----Original Message-----
> From: EXT rachild.chen [mailto:rachel.chen@huawei.com.cn]
> Sent: Friday, March 31, 2000 6:44 AM
> To: si-list@silab.eng.sun.com
> Subject: [SI-LIST] : 回复: [SI-LIST] : Parallel Plate Capacitance for
> Bypass
>
>
> Who can tell me how much the break voltage of 5 mils FR4
> is?We have do a
> test.It will be break under 1500V.
> 5 mils is the littlest thickness of FR4.How much is it to
> support a
> 1500V break voltage?
>
> Regards,
>
> Rachild
>
> -----Original Message-----
> 发件人: Jerry Johnson <jjohnson@minn.teradyne.com>
> 收件人: si-list@silab.eng.sun.com <si-list@silab.eng.sun.com>
> 日期: 2000年3月30日 9:55
> 主题: Re: [SI-LIST] : Parallel Plate Capacitance for Bypass
>
>
> >Ron,
> >
> >Could be we're missing each other somehow.
> >
> >What I saw was Steve say that 5 mils of FR4 would yield ~200
> pF/square
> >inch.
> >
> >Then I thought you said "So, by extension, 2.2 mil dielectric. . .
> >should be
> >about 1000pf/in sq for FR4 . . ."
> >
> >That looked to me like you had taken [(5^2)/(2.2)^2] * 200 = 1033
> >pF/square inch.
> >
> >I commented that capacitance wasn't an inverse square
> relationship with
> >distance
> >between plates. I calculated more like [5/2.2] * 200 = 455 pF/square
> >inch.
> >
> >Perhaps I completely misunderstood your reasoning. If so, I'm sorry.
> >
> >Jerry Johnson
> >
> >Ron Miller wrote:
> >>
> >> Jerry
> >>
> >> maybe I am missing something or maybe we are not communicating
> >> well. The capacitance I am talking about would be an IC
> or a discrete
> >>
> >> device connected to power and ground. The capacitance would be
> >> somewhat limited by the quarterwave distance from that pin for any
> >> frequency of intrest, because above that distance the delay is too
> >> great for the capacitance to be of any effect.
> >>
> >> So, the 1 inch concern would roughly describe a circle
> with a 1/2 inch
> >>
> >> radius, which for FR4(velocity 170 ps/inch) or 85 ps.
> >>
> >> The frequency which has a quarterwavelength of 85 ps is
> 1/340ps=~3Ghz
> >> At 3 Ghz and below we get 200 pf per square inch, or about
> .27 ohms.
> >>
> >> Scaling from 3 Ghz, down in frequency we get higher Xc, but the
> >> effective
> >> capacitive area goes up. The limits are that several
> devices will be
> >> sharing
> >> the same capacitance and the board has dimensional limits
> so we must
> >> add capacitances. Scaling up in frequency, the effective
> capacitance
> >> goes
> >> down but so does the Xc.
> >>
> >> TRACES across a plane is an entirely different matter, and PLANE
> >> capacitance for the entire board is again a different matter.
> >>
> >> BOTTOM LINE:
> >> Capacitors below 200 pf in value are of little value for bypassing
> >> if you have 5 mil dielectric spacing power to ground.
> >>
> >> Ron Miller
> >>
> >>
> >> Gerald Johnson wrote:
> >>
> >> > Ron,
> >> >
> >> > Capacitance of planes is NOT a function of inverse square of
> >> > distance.
> >> > See thread in this list about a week ago. Well covered there.
> >> >
> >> > Valid to use inverse square distance for point source, not for
> >> > planes.
> >> >
> >> > Result, capacitance would be about (5/2.2)*200 = 454.6 pF if the
> >> > 100 pF per in^2 at 5 mils is correct.
> >> >
> >> > Jerry Johnson
> >> > Teradyne Inc.
> >> >
> >> > >Date: Mon, 27 Mar 2000 10:39:10 -0800
> >> > >From: Ron Miller <rmiller@Brocade.COM>
> >> > >To: si-list@silab.eng.sun.com
> >> > >Subject: Re: [SI-LIST] : Parallel Plate Capacitance for Bypass
> >> > >
> >> > >Thanks Steve, I knew it was somewhere around there.
> >> > >
> >> > >So, by extension, 2.2 mil dielectric, available at very
> little if
> >> > any
> >> > >extra cost should be about 1000pf/in sq for FR4
> >> > >and eliminatee the need for discrete capacitors below 1000 pf.
> >> > >
> >> > >ron
> >> > >
> >> > >"S. Weir" wrote:
> >> > >
> >> > >> Ron,
> >> > >>
> >> > >> 5 mils should yield about 200pF / in sq, before
> taking away for
> >> > vias.
> >> > >>
> >> > >> Regards,
> >> > >>
> >> > >>
> >> > >> Steve.
> >> > >> At 02:30 PM 3/24/2000 -0800, you wrote:
> >> > >>
> >> >
> >> > **** To unsubscribe from si-list or si-list-digest: send
> e-mail to
> >> > majordomo@silab.eng.sun.com. In the BODY of message put:
> UNSUBSCRIBE
> >> > si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
> >> > si-list archives are accessible at http://www.qsl.net/wb6tpu
> >> > ****
> >>
> >> --
> >> Ronald B. Miller _\\|//_ Signal Integrity Engineer
> >> (408)487-8017 (' 0-0 ') fax(408)487-8017
> >> ==========0000-(_)0000===========
> >> Brocade Communications Systems, 1901 Guadalupe Parkway,
> San Jose, CA
> 95131
> >> rmiller@brocade.com, rbmiller@sjm.infi.net
> >>
> >>
> >
> >**** To unsubscribe from si-list or si-list-digest: send e-mail to
> majordomo@silab.eng.sun.com. In the BODY of message put:
> UNSUBSCRIBE si-list
> or UNSUBSCRIBE si-list-digest, for more help, put HELP.
> >si-list archives are accessible at http://www.qsl.net/wb6tpu
> >****
> >
>

**** To unsubscribe from si-list or si-list-digest: send e-mail to
majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list
or UNSUBSCRIBE si-list-digest, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu
****

**** To unsubscribe from si-list or si-list-digest: send e-mail to majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu
****


About this list Date view Thread view Subject view Author view

This archive was generated by hypermail 2b29 : Thu Apr 20 2000 - 11:35:59 PDT