An Automatic Routing System for High Density Multilayer Printed Wiring Boards

Recent advances in the packaging technology of microelectronics have changed the design rules for printed wiring boards (PWB's) such that the number of wiring tracks between adjacent pins of an ordinary dual in line package (DIP) is allowed to be two or more, and the number of signal layers to be laminated is often required to be four or more. When the packaging density or scale of a PWB augments to such an extent, conventional routing schemes are confronted with various difficulties. The present paper describes a new routing system which can cope with such high density PWB's, for which the maximum numbers of layers to be laminated, circuit modules to be mounted, and signal nets are admitted up to 16, 2,000 and 4,000, respectively. The system described operates on a PDP 11/34 computer coupled with a TEKTRONIX 4014 graphics terminal. A set of implementation results are also shown to reveal how much the described system contributes to the reduction of time and labor incurred in laying out multilayer PWB's of high density.