Pin Assignment on a Printed Circuit Board

The design of a Printed Circuit Board is complete when the board is routed. All effort prior to activating the router is aimed at insuring successful routing, often involving the following steps: 1) Assigning elements to packages (this is known as the assignment problem). 2) Placing the packages on the board (the placement problem). 3) Assigning the connections of the nets to specific pins on the packages (the pin assignment problem). Each of these steps is designed to help produce a routable board. This paper describes a method of solving the pin assignment problem that achieves routability of the board by reducing prospective wire crossings. Routability is improved by ordering the nets to be assigned to a specific set of pins according to their location relative to this set of pins, and then assigning them, in this order, to the nearest available pin.