Automatic flexible wire bonder for MEMS sensor packaging based on zoom lens system

Generally, wire bonder for Micro-electromechanical Systems (MEMS) packaging uses conventional IC packaging technique for reference, but because of various different sizes and patterns of MEMS specially trained technicians must be needed to adjust the parameters of wire bonder. To reduce the product cost and simultaneously obtain high product quality, a flexible wire bonder system for automated wire bonding of MEMS sensors is developed. A manual wire bonder is reconstructed and integrated with visual feedback system. High magnification optical microscope is usually used to get highly accurate position of MEMS sensors. However, the small field-of-view of optical microscope essentially limits workspace of the micromanipulator and the low depth-of-field makes it difficult to handle micro parts. A zoom microscope is chosen to gain multiple magnification images for coarse-to-fine micropositioning. With low magnification, objects can be identified and located coarsely. The precise position of objects can be calculated accurately with high magnification images. The auto-focusing process and image segmentation method based on focus measures are described. At last, the productivity of the flexible wire bonder is validated through a wire bonding experiment for MEMS pressure sensors.