Three-dimensional routing for multilayer ceramic printed circuit boards

An efficient three-dimensional (3-D) routing technique is presented for multilayer ceramic printed circuit (PC) boards. The router can take account of via length as well as pattern length. In the first of the two steps involved, it searches in the direction of via depth from start and end points only. This is called two-and-a-half-dimension (2.5-D) routing. Step two combines 2-D and 3-D routing for wiring not covered in step one. This enables tens of thousands of wires to be routed at 99% effectiveness in less than four hours of CPU time, with all delay conditions satisfied.<>