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# Determining Printed Circuit Wiring [Paths]

IP.com Disclosure Number: IPCOM000076818D
Original Publication Date: 1972-Apr-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 3 page(s) / 42K

IBM

## Related People

Raymond, TC: AUTHOR

## Abstract

In laying out the circuits on a printed-circuit board, a common approach to the wiring problem is to determine the location of brackets, each of which interconnect or terminate at two pins or vias, so that no two brackets interfere or short with each other. To solve this problem, it is convenient to look at a row or column of pins and vias one row at a time. Two questions arise for each row or column:

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Determining Printed Circuit Wiring [Paths]

In laying out the circuits on a printed-circuit board, a common approach to the wiring problem is to determine the location of brackets, each of which interconnect or terminate at two pins or vias, so that no two brackets interfere or short with each other. To solve this problem, it is convenient to look at a row or column of pins and vias one row at a time. Two questions arise for each row or column:

1) Can a given set of brackets in the same row be wired without interfering?

2) Given a set of brackets in the same row that do not interfere, can an additional bracket be routed without interfering?

Depending on the approach to the total wiring problem, only one of the above questions requires an answer. For example, one approach is to postulate a set of brackets for every connection without regard to interference. Then those brackets which cause shorting or interference must be removed and new paths found for them. Another approach is to answer question 2, for each connection in turn, thereby building up a set of noninterfering brackets. The answers or approaches suggested by both questions can be obtained using the following method.

First, define two brackets as interfering if they partially overlap each other. In examples a, b, c and d, example (a) shows interference. Examples b and c do not interfere. Example d is problem dependent. There is no interference if sharing the common connection is allowed. Otherwise, there is interference. Second, a mathematical graph can be constructed from a set of brackets. Each bracket is considered a vertex of the graph. A line or edge is drawn between two vertices if the brackets represented by the vertices interfere, in accordance with the definition discussed in the first step.

This method will be more apparent using a specific example. In example e, the problem is to connect pins of like number by brackets. Graph f may be constructed as follows:

First, assume a bracket between points 1 in example e. For the graph then, a vertex numbered 1 is made. Relative to this bracket 1, all other brackets are tested to determine whether or not they interfere with bracket 1. Proceeding from left to right, we find that bracket 7 interferes. Therefore, a vertex 7 can be placed on a graph and a line drawn between the two. Similarly, we find that vertex 6, can be drawn and connected to vertex 1. None of the other brackets interfere with 1. We can then proceed to test the next nu...