RE: [SI-LIST] : Comment on Johnson's article

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From: Chris Cheng (hycheng@3pardata.com)
Date: Fri Nov 05 1999 - 19:17:12 PST


if you can afford a few more cents try IDC.
if you can afford a few more bucks try LICA.

> -----Original Message-----
> From: owner-si-list@silab.eng.sun.com
> [mailto:owner-si-list@silab.eng.sun.com]On Behalf Of Rick Brooks
> Sent: Friday, November 05, 1999 6:48 PM
> To: si-list@silab.eng.sun.com
> Subject: Re: [SI-LIST] : Comment on Johnson's article
>
>
> Has anybody ever tried 0508 caps (not 0805) with multiple
> trace/vias to the planes?
> It seems like a better idea for low inductance, but I don't know
> about the cost or availability.
>
> - Rick Brooks
>
>
>
>
> At 04:59 PM 11/05/1999 -0800, you wrote:
> >
> >> Date: Fri, 05 Nov 1999 16:39:47 -0800
> >> From: Howard Johnson <howiej@sigcon.com>
> >>
> >> If you want to achieve an even lower impedance, try smaller capacitors,
> >> or go with some of the more advanced packages (for
> >> example the new "IDT" package from AVX claims to
> >> deliver an installed inductance of 0.1 nH per component.)
> >>
> >> Best regards,
> >> Dr. Howard Johnson
> >
> >Most of the inductance is not in the capacitor but is in the pads
> >and vias to the power planes. Our studies show that the inductance
> >in the capacitor itself is between .2 and .4 nH for 0805 capacitors,
> >depending on the height. The mounting inductance usually ranges
> >from 0.3 to 2 nH depending on the depth of the vias to the power
> >planes and the spacing between vias.
> >
> >The cost of low inductance capacitors is not worth it unless you
> >are going to commit substantial board area for multiple vias to
> >the power planes and can tolerate the loss of wiring channels.
> >
> >best regards,
> >Larry Smith
> >Sun Microsystems
> >
> >
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