A Route Optimization Problem in Electrical PCB Inspections: Pickup and Delivery TSP-Based Formulation

This paper discusses a new route optimization for inspecting printed circuit boards (PCBs). In inspections of PCBs, a number of PCBs arrayed on a plane are tested by a probe in some order or sequence. Since the length of an inspection route depends on the order or sequence that the probe visits and tests each of PCBs, the finding of best visiting order or sequence is quite important in order to reduce the PCB inspection time. Recently, due to the miniaturization of PCBs, the procedure of “alignment” has become necessary before the electrical test, which means that there is a precedence constraint between alignment and test. This paper models a PCB inspection route optimization problem with alignment operations as a class of pickup and delivery traveling salesman problem (PDTSP) which is a mixed 0–1 integer programming problem. An efficient heuristic algorithm is proposed to solve the problem with a practical computational time. The proposed algorithm is installed into real PCB inspection machines that have been widely used in the world. Cost reduction effects for PCB inspection factories are discussed.