Network layout procedure for printed - circuit design

This paper describes a heuristic solution procedure for laying out the conductors of a printed circuit on the two sides of a plate of nonconducting material. There must be no overlap between conductors on the same side of the plate as they are uninsulated. For certain layouts it is necessary to drill holes in the plate and pass conductors through the holes to avoid overlap. The problem is to identify the layout which requires the minimum number of holes. The solution procedure uses a computer subroutine in conjunction with an iconic model of the plate. The subroutine is based on a method of Nicholson¹ which attempts to lay out a given circuit on one side of a plate to minimize the number of overlaps. The iconic model of the plate used in this research consisted of a pair of plastic sheets, representing the two sides of the plate, overlaid one on top of the other. The nodes and connections were drawn on them with felt-tip pens. The procedure is iterative and takes advantage of the fact that the problem can be viewed in terms of graph theory. The procedure is suitable for an interactive computer terminal system. Computational experience is limited but encouraging. However there is no guarantee that solutions produced by the procedure will be optimal in the sense that an absolute minimum number of holes will be required to be drilled.