ABSTRACT
A planar routing workspace, whether a hybrid or multichip module substrate or a circuit card, consists of stacks of conduction sheets sandwiched between insulation sheets. The conduction sheet is either a ground plane, a power plane, or a signal layer. The etched space between two parallel neighboring signal paths in a signal layer is called the clearance. This chapter introduces various search techniques using maze searching, line searching, and gridless searching. Maze searching involves gridding the workspace to measure the length of a path by the number of grids trans versed. The grid size is chosen to accommodate the path width, the clearance between parallel paths, and the vias. The original Lee's router was employed to find a shortest path connecting a terminal pair in a single layer. Lee's router is referred to as a wave-propagation method, because the method simulates a propagating wave from a radar station.
