[SI-LIST] Re: Capacitors arrays. worth it or not?
- From: steve weir <weirsi@xxxxxxxxxx>
- To: "Hill, John" <jhill@xxxxxxxxxx>,<Mark.Randol@xxxxxxxxxx>, "si-list" <si-list@xxxxxxxxxxxxx>
- Date: Mon, 22 May 2006 23:27:07 -0700
John, you've got it. The vertical orientation makes for N very small
cavities all acting in parallell. Hence, the secondary resonance
occurs at a much higher frequency.
Regards,
Steve.
At 01:50 PM 5/22/2006, Hill, John wrote:
>Steve,
>
>I'm sorry to be a little thick on this issue, but I may be getting the
>two orientations confused. If I understand you correctly, the following
>is true:
>
>It is Edie currents that keep the current concentrated in the lower
>plates of a capacitor when the capacitor is mounted horizontally, which
>we are defining as having the plates parallel to the board. This creates
>a resonate cavity under the part.
>
>When the capacitor is mounted with the plates perpendicular to the board
>the current flows through all the plates.
>
>Is this correct?
>
>John
>
>
>
>
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>-----Original Message-----
>
>From: steve weir [mailto:weirsi@xxxxxxxxxx]
>Sent: Monday, May 22, 2006 2:41 PM
>To: Hill, John; Mark.Randol@xxxxxxxxxx; si-list
>Subject: Re: [SI-LIST] Re: Capacitors arrays. worth it or not?
>
>John, when the plates of a cap are parallel to the planes, eddy
>currents block field penetration to the upper plates through the
>cavity. The field still goes around the terminal metalization. This
>makes a resonant cavity.
>
>Steve.
>At 10:50 AM 5/22/2006, Hill, John wrote:
> >Mark,=20
> >
> >We have uploaded an application note from American Technical Ceramics
> >concerning placing capacitors vertical and horizontal. The URL is:
> >
> >http://si-list.org/files/tech_files/ATC%20select_cap_wireless.pdf
> >
> >I have also sent an e-mail to the application engineer about the issue
> >of eddy currents limiting the field. The data in the application note
> >does not look like it supports the idea and I do not understand the
> >physics.=20
> >
> >John
> >
> >
> >=20
> >
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> >a particular recipient. If you are not the intended recipient(s), or
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> >intended recipient(s), you are hereby notified that any disclosure, =
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>=
> >information is prohibited and may be unlawful. When addressed to Takata
>=
> >customers or vendors, any information contained in this e-mail is =
> >subject to the terms and conditions in the governing contract, if =
> >applicable. If you have received this communication in error, please =
> >immediately notify us by return e-mail, permanently delete any =
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> >---------------------------------------
> >-----Original Message-----
> >
> >From: si-list-bounce@xxxxxxxxxxxxx
>[mailto:si-list-bounce@xxxxxxxxxxxxx]
> >On Behalf Of Mark Randol
> >Sent: Monday, May 22, 2006 10:33 AM
> >To: si-list
> >Subject: [SI-LIST] Re: Capacitors arrays. worth it or not?
> >
> > > -----Original Message-----
> > > From: si-list-bounce@xxxxxxxxxxxxx=3D20
> > > [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Jerry Martinson
> > >=3D20
> > > I've always wondered how discrete cap performance is affected=3D20
> > > if the caps plates are parallel with the underlying plane or=3D20
> > > if they are perpendicular. I'd think that having them rolled=3D20
> > > 90 degrees
> > > (perpendicular) might make them perform better in some=3D20
> > > regions. I wonder how this would extend to arrays and=3D20
> > > whether arrays are configured rolled or not. Does anyone=3D20
> > > know? =3D20
> >
> >American Technical Ceramics (ATC) used to recommend 'vertical'
>placement
> >of their porcelain caps for just this reason. I've seen it make
>several
> >100MHz's of difference in the measured resonance frequency. That was
>on
> >a relatively thick 2 layer PCB, so on a board with a thinner component
> >to ground layer spacing this could be more significant <guess>. I
> >didn't find it on their web site, but here is their link.
> >
> >http://www.atceramics.com/
> >
> >Now how much of this was due to plate coupling to the substrate, or
> >reduced effective capacitance and inductance because of current
>crowding
> >towards the new 'bottom' of all the plates, beats me. It seems to me
>in
> >the horizontal orientation, the upper plates would have slightly more
> >inductance due to the greater loop area. Which effect dominates,
> >capacitance or inductance? =3D20
> >
> >The problem at the time was fixed, so we didn't investigate further.
> >
> >--
> >Mark Randol, RF Evaluation & Application Engineer
> >Not speaking for my company, etc
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