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Automatically Rerouting Wires on Printed Circuit Boards to Avoid Noise Coupling Problems

IP.com Disclosure Number: IPCOM000083905D
Original Publication Date: 1975-Aug-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 4 page(s) / 92K

Publishing Venue

IBM

Related People

Hunt, RL: AUTHOR [+4]

Abstract

Summary: During the process of routing printed wires on some printed-circuit (PC) boards, it is required that the wires coming into the open channel areas have to be jogged to a wider pitch to limit coupled noise buildup. A procedure has been hereafter developed to automate the process in design automation (DA) to ensure that the jogging is done according to engineering specifications.

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Automatically Rerouting Wires on Printed Circuit Boards to Avoid Noise Coupling Problems

Summary: During the process of routing printed wires on some printed-circuit (PC) boards, it is required that the wires coming into the open channel areas have to be jogged to a wider pitch to limit coupled noise buildup. A procedure has been hereafter developed to automate the process in design automation (DA) to ensure that the jogging is done according to engineering specifications.

The Problem. Suppose that a circuit design group has established that the allowable maximum noise coupling on PC planes is 86.8 mv. Fig. 1 shows the quiet line and the first four adjacent lines contributing coupled noise to the quiet line. The breakdown of total mv among these four lines is given in Table 1.

(Image Omitted)

However, suppose that an analysis, made by an electrical requirement group for board design, has shown that the noise can increase to 104 mv if the line pitch of 11.8 mils is used for the entire PC board. Suppose that it also has indicated that jogging to 24.6 mils in the open-channel area, maintains the maximum noise comparable with the original design noise of 86 mv. An example of jogging points is depicted in Fig. 2.

In other words, the jogging of wires coming into the open-channel area is necessary to keeping the coupled noise within the tolerable limit. The jogging problem presents a new challenge to DA in the following two areas:
A) How to describe the jogging points in the package. Since DA never had this problem before, a way has to be found to

identify these jogging points to the affected programs.

B) How to implement the actual jogging.

Analysis. Four basic requirements were first identified:

A) Since the size and type of boards varies, the physical locations of jogging points are different by part numbers.

Hence, it requires that the wag of recording has to be

rule-driven.

B) No new package description rule is preferable. However, existing rule macros are allowed to change.

C) The jogging process should be transparent to the user. This is especially true when manual embedding has to be done.

If the user is required to manually specify the jogging

points, the process will be very error prone.

D) The impact of jogging points to the existing programs has to be minimized.

In light of these requirements, a procedure was developed to solve the problems stated at the end of the preceding section. 1) The description of jogging points is to be implemented in a channel description rule written in assembler MACROS.

This approach satisfies requirements A and B.

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2) The actual jogging will be performed by a subroutine by

accessing the description of jogging in the rule. The

subroutine will be commonly used by the automatic wiring

program and the manual embedding program. This method

satisfies requirements C and...