Re: Q:Via Capacitance....Re: [SI-LIST] : Pass-through vias as BGA lands

Laurence Michaels (lmichael@techmail.gdc.com)
Tue, 9 Mar 1999 09:24:41 -0500

I'm assuming that D2 = annular ring diameter,
D1 = drill size, and T = Thickness.

Is that correct?
-- Laurence

Which physical characteristChandrakant Hemraj Sakharwade wrote:
>
> Daniel,
>
> The value of ~0.53 pF as given in "High-Speed Digital Design"
> is for a 16 mil via with 28 mil annular ring and 50 mil clearance
> hole in ground plane (for a 63 mil PCB thickness.)
>
> One can reestimate the capaciatance for other geometries
> (C = 1.41*er*T*D1/(D2-D1)).
>
> Microstrip with following geometry has 2.6 pF /inch
> (Width = 8 mil, height above ground plane = 6 mil,
> thickness = 2.37 mil, er = 4.5)
>
> Hope this helps.
>
> -Sakh
>
> Cadence Design Systems
>

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