A New Solder Paste Inspection Device: Design and Algorithm

In this paper, we present an innovative design of a solder paste inspection device which can be practically integrated into existing solder paste printing machines. Since solder paste inspection systems usually occupy a large space in vertical direction, we designed a mirror box that can re-direct the transmission of fringe pattern. In this way, a new parallel solder paste inspection device with a significant reduction in the vertical constraint is developed. We also developed a hybrid weighting algorithm that applied the distance and fringe contrast to acquire the height of solder pastes. Furthermore, we developed an algorithm that generates the 2-D image from the fringe pattern images during the 4-steps algorithm. It gives benefit (time for solder paste inspection) to traditional approach that uses some special lighting systems to create the 2-D image. Experimental results show our device can inspect the 20mm times 20mm PCB area within 2 seconds and the maximum standard deviation for the average height is 3 mum.