Re: [SI-LIST] : Decoupling capacitors (again!)

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From: Ritchey Lee (leeritchey@earthlink.net)
Date: Sun Aug 27 2000 - 15:37:52 PDT


What printed Circuit Board shop do use?

Lee

Kon, Hon Lee wrote:

> We do design high speed multilayer PCB of up to 16 layers and we normally
> use 5mils as the core between the PWR and GND plane. We use multiple Vcc-GND
> planes to provide multiple plane capacitance and interdigitated. However, we
> have not tried using any dielectric thinner than 3mils as our PCB board
> house advicing us not to use it because of leakage and potential shorts due
> to the thin prepreg. Special material would have to be used similar to those
> used in buried capacitance board which cost a lot more than normal PCB. - my
> 2cents
>
> Thank you.
>
> Regards
> HL Kon
> Hardware Development Engineer
> iNTEL Test Tooling Operations Malaysia
>
>
> -----Original Message-----
> From: Ritchey Lee [mailto:leeritchey@earthlink.net]
> Sent: Wednesday, August 23, 2000 11:38 PM
> To: Barry Ma
> Cc: Larry.Smith@eng.sun.com; si-list@silab.eng.sun.com
> Subject: Re: [SI-LIST] : Decoupling capacitors (again!)
>
> I design lots of high speed multilayer PCBs. I use 3 mils between power
> planes to achieve maximum plane capacitance. You can do this reliably so
> long as you do you stackup so that the dielectric between the power planes
> is the prepreg material.
>
> Lee
>
> Barry Ma wrote:
>
> > Larry,
> >
> > Thanks a lot for your great note! It is very helpful.
> >
> > You mentioned small spacing between pwr and gnd planes in the PCB a couple
> of times in the discussion. I'd like to add my 2 cents.
> >
> > In addition to enough capacitance between pwr and gnd planes for high
> frequencies noise to go through, the small spacing also makes it possible
> for limited decoupling capacitors to be shared by different gates. This is
> another important reason why much less numbers of decap can practically work
> than calculated numbers.
> >
> > You suggested 5 mil or so spacing, Prof. Todd Hubing asked for at least <
> 10 mil. Is there any articles giving quantitative description about the
> criteria?
> >
> > Thanks.
> > Best Regards,
> > Barry Ma <bma@anritsu.com>
> > ANRITSU www.anritsu.com
> > Morgan Hill, CA 95037
> > Tel. 408-778-2000 x 4465
> > _______________________________________________________________________
> >
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