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Plane Shift Measurement Method Utilizing Z-Axis Coupled Structures

IP.com Disclosure Number: IPCOM000007810D
Publication Date: 2002-Apr-24
Document File: 2 page(s) / 30K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that uses broadside impedance structures to accurately measure layer registration and movement in packaging and PCB fabrication. Benefits include the ability to measure plane shift in a non-destructive way.

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Plane Shift Measurement Method Utilizing Z-Axis Coupled Structures

Disclosed is a method that uses broadside impedance structures to accurately measure layer registration and movement in packaging and PCB fabrication. Benefits include the ability to measure plane shift in a non-destructive way.

Background

Currently, plane shift is measured by taking an open/short measurement of the concentric ring of a drilled hole, or by optical measurement.

General Description

The disclosed method uses two or more pairs of broad side impedance structures. By comparing the relative coupling of each trace combination, the movement of one plane relative to the other can be determined (see Figure 1). This can be done without knowing the impedance values, or the dielectric thickness, spacing, or constant.

Structures are made by placing two  or more conductive strips on each  plane. Conductive strips on the second plane are spaced differently than those on the first plane. The number of strips and the spacing between strips are selected based on the required measurement range and accuracy.

Advantages

The following are advantages of the disclosed method:

§         Better resolution in measurement sensitivity

§         Elimination of measurement errors due to drill inaccuracies

§         Ability to measure plane shift without damaging the product

§         Ability to combine the mechanical measurement coupon with the electrical/impedance 

      coupon.

Disclosed anonymously