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# Algorithms for Perforated Power Planes

IP.com Disclosure Number: IPCOM000120731D
Original Publication Date: 1991-Jun-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 4 page(s) / 142K

IBM

Raver, N: AUTHOR

## Abstract

An important problem in package analysis deals with solid power/ground metal planes with perforations to allow vias to pass through them. For example, chip modules are connected to cards with vias. Similarly, the silicon carrier module uses vias to connect the C4 pads of the chip to the power/ground metal planes. See Fig. 1. The algorithms discussed in this article deal with calculating the inductance contribution of these perforations.

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Algorithms for Perforated Power Planes

An important problem in package analysis deals with solid
power/ground metal planes with perforations to allow vias to pass
through them.  For example, chip modules are connected to cards with
vias.  Similarly, the silicon carrier module uses vias to connect the
C4 pads of the chip to the power/ground metal planes.  See Fig. 1.
The algorithms discussed in this article deal with calculating the
inductance contribution of these perforations.

The normal approach to this type of problem is to break up the
metal involved into suitable small pieces and feed the geometric
descriptions of these pieces to a general-purpose inductance
calculation program, such as L3D. The break up into small pieces must
capture the current flow through the metal.  Around the perforations,
the current can only flow tangentially.  Away from the perforations,
the current can flow in any direction.  For discussion purposes, we
will assume the solid metal plane is parallel to the x-y plane and
that the penetrating vias are parallel to the z axis. The current in
the solid planes can flow anywhere in the x-y plane, but to
approximate this flow, the metal is broken into x pieces and y pieces
called bars.  It is common practice to model a solid plane with
overlapping x and y bars to approximate the current flow.  The
granularity of the bars is determined by the accuracy desired; the
more bars, the lengthier the calculation.  The bars used to...