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

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From: Michael Khusid ([email protected])
Date: Thu Aug 17 2000 - 12:16:34 PDT


Based on my experience with prepreg vendors, it is practically next to
impossible to define the prepreg thickness. First of all, the material is
not of identicaly thickness, and second, the material changes properties
during the manufacturing process. The story is only slightly better with
cores. Normally, I've seen tolerances up to plus/minus 1 mil on the <10 mil

Another thing, the manufacturer may be the best person to know the actual
thickness of the material after fabrication, and that's really what
designers care about. I would be surprised if any material vendor can claim
after-fabrication thickness accuracy to 0.1 mil, that's why I would be
surprised if any vendors sells different materials for 1.8 and 2 mils

Mike Khusid
Sitara Networks

> -----Original Message-----
> From: Barry Ma [mailto:[email protected]]
> Sent: Thursday, August 17, 2000 2:05 PM
> To: [email protected]
> Subject: RE: [SI-LIST] : Decoupling capacitors (again!)
> On Thu, 17 August 2000, Larry Smith wrote:
> > Zycon (bought by Hadco) got a patent on this
> > concept. Right now, anybody who uses 2 mil FR4 between power planes
> > must consider their legal position with this patent. ...
> ---------
> How about 2.2 or 1.8 mil?
> Barry


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