Control System Design for Height Measurement of BGA Balls Based on Timed Automata

This paper presents a model, based on timed automata (TA), of a real-time control system to measure the heights of solder balls of ball grid arrays (BGAs) on a printed circuit board and to determine whether the BGAs pass the height inspection routine. The TA model is actually a network of five TA, namely User, Controller, Motion, Camera, and Light, synchronized through user-defined channels. The dynamics of system components are simplified by a time delay which can be determined through experiments or roughly by experience. The simulation and verification in UPPAAL show that the model works fine without deadlock, and procedures after user operations demonstrate proper timely cooperation among the automata. The main design of hardware and software for the control system based on the model is also given in this paper, which has been successfully implemented in our laboratory.