FreeLists / si-list / [SI-LIST] Re: 0306 Capacitors

[Ken Hayden <khayden@xxxxxxxxxxxxxxxxxx>]

What about mounting 0306 (or other broadside capacitors) with 1 or more vias
within the pads, more or less eliminating the pad-layer annular ring inductance?
Would the mounted inductance then be determined by the via barrel inductance and
the spreading inductance of the plane to which the via attaches?  I would think 
in
this case that both the inductance of the via barrel and the spreading
inductactance into the plane would be inversely proportional to the via 
diameter.
-Ken Hayden

steve weir wrote:

> Istvan, yes if we change ID alone then your point is taken, but to do that
> means that we started out with an excessive OD, which is just the same as
> moving the via away from the device pad for no reason.  My assumption is
> that we would never use excessive OD annular rings.  So, ID and OD
> track.  Is there a good reason that we would not track ID and OD at the
> economic sweet spot of our fabrication capability?
>
> Regards,
>
> Steve
>
> At 10:24 AM 3/14/2004 -0500, Istvan NOVAK wrote:
> >Steve,
> >
> >I think I start to understand where we differ.  The ln(R)
> >term still refers to the cylinder itself.  My comment
> >referred to (but I probably was not clear about it) the
> >inductance of the pad between the cylinder of via to
> >the edge/periphery of the pad, or the connection line
> >of capacitor body, whichever is closer to the via
> >cylinder.  When the cylinder gets bigger, the horizontal
> >  inductance of the same pad gets lower.
> >
> >Regards,
> >Istvan
> >
> >
> >
> >
> >----- Original Message -----
> >From: "steve weir" <weirsp@xxxxxxxxxx>
> >To: "Istvan NOVAK" <istvan.novak@xxxxxxxxxxxxxxxx>
> >Cc: <si-list@xxxxxxxxxxxxx>
> >Sent: Saturday, March 13, 2004 9:41 PM
> >Subject: Re: [SI-LIST] Re: 0306 Capacitors
> >
> >
> > > Istvan, if we apply Biot-Savart, the inductance of the surface
> > > cross-section grows with diameter.   As we increase the diameter, the
> > > incremental area of each circumference slice gets bigger, helping
> > > inductance, but the radius also similarly increases.  We end-up
> >integrating
> > > dr/R which returns a natural log function.
> > >
> > > Regards,
> > >
> > >
> > > Steve.
> > > At 09:12 PM 3/13/2004 -0500, Istvan NOVAK wrote:
> > > >Steve,
> > > >
> > > >Assuming a square pad and a circular via in its center:
> > > >if we increase the diameter of the via, dont we have
> > > >a shorter distance from the edge of the pad to the via tube?
> > > >
> > > >Regards,
> > > >Istvan
> > > >
> > > >
> > > >----- Original Message -----
> > > >From: "steve weir" <weirsp@xxxxxxxxxx>
> > > >To: "Istvan NOVAK" <istvan.novak@xxxxxxxxxxxxxxxx>
> > > >Cc: <si-list@xxxxxxxxxxxxx>
> > > >Sent: Saturday, March 13, 2004 5:34 PM
> > > >Subject: [SI-LIST] Re: 0306 Capacitors
> > > >
> > > >
> > > > > Sure, looking from the connecting edge of the via pad to the center
> >where
> > > > > it meets the top of the tube, the inductance increases with the OD.
> >It is
> > > > > a pretty straightforward application of Biot-Savart.
> > > > >
> > > > > Regards,
> > > > >
> > > > >
> > > > > Steve.
> > > > > At 11:24 AM 3/13/2004 -0500, Istvan NOVAK wrote:
> > > > > >Steve,
> > > > > >
> > > > > >I am not sure I agree with your following statement in the context we
> > > >have
> > > > > >here
> > > > > >(connecting component pads to planes).  Can you elaborate?
> > > > > >
> > > > > >
> > > > > > > 1) A larger via radius increases the partial inductance on the
> >surface
> > > >by
> > > > > > > ln( radius ).
> > > > > > >
> > > > > >
> > > > > >Regards,
> > > > > >Istvan
> > > > >
> > > > >
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