Multilayer printed wiring board and method of measuring characteristic impedance

Abstract

A multilayer printed wiring board having a compact test coupon formed on each of the signal wiring layers is provided, and accurate and efficient method of characteristic impedance measurement for each signal wiring layer is realized. The test coupon is constituted by a plurality of linear parts extending parallel to each other and folded-back parts mutually connecting the linear parts. A through hole is provided for serially connecting the respective test coupons of the signal wiring layers adjoining each other. Two measuring pads, one is connected to one end of the serially connected test coupons and another is connected to the ground layer, are also provided. The measurement is performed by applying a step pulse between two measuring pads and measuring voltages of reflection waves from the serially connected test coupons.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary features and advantages of the present invention will become apparent from the following detailed description when taken with the accompanying drawings in which:

FIG. 1 is a plan view showing a wiring pattern of a test coupon formed on each signal wiring layer in a multilayer printed wiring board according to an embodiment of the present invention;

FIG. 2 is an exploded perspective view schematically showing the multilayer printed wiring board according to the embodiment of the present invention;

FIG. 3A is a plan view showing details of a corner part of the test coupon shown in FIG. 1;

FIG. 3B is a plan view showing details of measuring pads of the test coupon shown in FIG. 1;

FIG. 4 shows an observation waveform of an oscilloscope measured by the TDR method using a conventional test coupon;

FIG. 5 shows an observation waveform of the oscilloscope measured by the TDR method using the test coupon according to the present embodiment;

FIG. 6 is a plan view showing the conventional test coupon; and

FIG. 7 is a perspective view of the conventional test coupon disclosed in Japanese Patent Laid-Open No. 8-46306.

Claims

1. A multilayer printed wiring board having a plurality of signal wiring layers and at least one ground layer, comprising: a test coupon for measuring impedance, which is formed on each of the signal wiring layers;a through hole which serially connects the respective test coupons of the signal wiring layers adjoining each other;a measuring pad which is connected to one end of the serially connected test coupons; anda measuring pad which is connected to the ground layer.

2. The multilayer printed wiring board according to claim 1, wherein the test coupon of each of the signal wiring layers is constituted by a plurality of linear parts extending parallel to each other and folded-back parts mutually connecting the plurality of linear parts.

3. The multilayer printed wiring board according to claim 2, wherein the folded-back part is constituted by a plurality of bending parts, and a bending angle of each of the bending parts is 45° or less.

4. A method of measuring characteristic impedance of a plurality of signal wiring layers of a multilayer printed wiring board having the plurality of signal wiring layers and at least one ground layer, comprising: forming a test coupon for measuring impedance on each of the signal wiring layers;serially connecting the test coupons of the respective signal wiring layers;applying a step pulse between a measuring pad connected to one end of the serially connected test coupons and a measuring pad connected to the ground layer; andmeasuring voltages of reflection waves from the serially connected test coupons.

5. The method of measuring characteristic impedance according to claim 4, wherein the test coupon of each of the signal wiring layers is constituted by a plurality of linear parts extending parallel to each other and folded-back parts mutually connecting the plurality of linear parts.

6. The method of measuring characteristic impedance according to claim 5, wherein the folded-back part is constituted by a plurality of bending parts, and a bending angle of each of the bending parts is 45° or less.

7. A multilayer printed wiring board in which a test coupon is formed in a signal wiring layer, wherein the test coupon is constituted by a plurality of linear parts extending parallel to each other and folded-back parts mutually connecting the plurality of linear parts.

8. The multilayer printed wiring board according to claim 7, wherein the folded-back part is constituted by a plurality of bending parts, and a bending angle of each of the bending parts is 45° or less.