A high performance linear motor drive for integrated circuit´s leads inspection system

The advancement of microelectronics has resulted in the continuing increase in the lead counts and tighter lead pitches of the integrated circuit. Consequently, the leads have become inherently more fragile. To ensure that the lead form meets the PCB assembly requirements, vision based lead inspection system is often used. In this paper, the authors present the motion control system of a prototype vision based lead inspection system. To achieve high performance, the system uses a permanent magnet DC linear motor as the actuator. This eliminates the needs of mechanical means such as lead screws that are used in the conventional rotary drive. To obtain high performance and robustness, a discrete time sliding mode controller has been developed for closed loop position control. The proposed approach results in fast and accurate servo response with a positioning accuracy of 1 μm and a speed of more than 1.5 m/s. Some experimental results are presented