1906	 Automated Printed Circuit Routing with a Stepping Aperture	 A computer program for routing interconnections on a two-sided printed circuit board with a regular pattern of lines pins terminals and vias feed-through holes is described. In this program each interconnection is given a planned routing-typically down from the upper pin through a via and horizontally to the lower pin. From the top a virtual aperture i.e. a long horizontal slit is stepped down the board. The planned routing is the basis for rerouting interconnections within the aperture to resolve conflicts for lines and vias below the aperture and to maximize the effective line usage. If a conflict has not been resolved before the aperture arrives at the lower pin interconnections are deleted to resolve the conflict. Extensions of this technique to the control of crosstalk between routed interconnections and to the problem of obtaining percent interconnect are also discussed. routing printed circuit interconnections aperture stepping aperture computer program circuit board lines vias pins
