Stress-Minimized Packaging of Inertial Sensors by Double-Sided Bond Wire Attachment

This paper presents a novel approach for low-stress packaging of microelectromechanical system (MEMS)-based gyroscopes. The proposed approach makes use of conventional ball-stitch wire bonding. The gyroscope die is attached exclusively by means of bond wire connections between the package frame, and the top and bottom surfaces of the die. The process enables the electrical connection of metal pads on the top and the bottom side of the MEMS die within the same process. No adhesives, glue, or solder is used for the die attach. The stiffness of the proposed die attach is evaluated by scanning laser Doppler vibrometry. White-light interferometry is used to investigate stress in the die that is induced by the die attach. The bond wire attachment is compared with conventional single-sided die attach using two types of commercially available adhesives. It was found that the proposed packaging system exhibits multiple resonance modes and displays a dependence on the amount of bond wires. White-light interferometry reveals a centered bow across the die and shows low-induced stresses compared with conventionally attached dies using epoxy adhesives.