From: Bob Lewandowski (Bob.Lewandowski@Vixel.com)
Date: Fri Aug 18 2000 - 11:10:13 PDT
Have you read the patent on this? He appears to be seeking coverage for almost any
configuration of PCB that makes a capacitor. Duhh!?! Dielectric thickness from "about 0.5 to
about 50 mils", and dielectric constant "of at least about 4 ". Also dielectrically "filled
polytetrafluoruethylene" somebody better tell 3M that the Episilam material that they made in
the late '70s is in violation of this 1998 patent!
Larry Smith wrote:
> Martin - The most important thing about Hadco material is the patent.
> When it comes right down to it, there is nothing special about the 2
> mil FR4 material, except for maybe some handling techniques and room
> cleanliness. Somehow, 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. ...I am way out
> side of my expertise (SI gone to law), so I think I better quit here...
> Larry Smith
> Sun Microsystems
> > Date: Thu, 17 Aug 2000 07:57:41 +0100
> > From: "Martin J Thompson" <Martin.J.Thompson@trw.com>
> > To: <firstname.lastname@example.org>
> > Subject: RE: [SI-LIST] : Decoupling capacitors (again!)
> > Larry, another question on buried capacitance...
> > What is it about Hadco's material that allows you to get 2mils separation? Can this not
> be achieved with straight FR-4?
> > Thanks,
> > Martin
> > <snipped for context>
> > >>> Larry Smith <Larry.Smith@Eng.Sun.COM> 16 August 2000 23:55:52 >>>
> > It turns out that the spreading inductance of power planes
> > spaced 4 mils apart will give you roughly 20 mOhms at 100 MHz. We are
> > using Hadco 'buried capacitance' planes that are 2 mils apart in many
> > of our products to get lower impedance.
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