Development of alignment inspection system for ball grid array packaging

The ball grid array (BGA) has become one of the most popular packaging alternatives for high I/O devices in the industry with many advantages: high interconnection density and less packaging space and so on. In these days, the size of chip becomes small and the size of ball grid also becomes small, so the process of BGA alignment becomes more important and difficult. In this paper, the BGA alignment system before the oven process step is managed. The main difficult of inspecting the BGA alignment is that the substrate is always tilted due to irregular carrier size and in-line process. In this paper, to overcome this problem, tilt angle of substrate is measured by phase measuring profilometry (PMP), and then the compensated alignment offset calculation algorithm is suggested. The performance of our system is checked by a series of real experiments.