Die attach is a typical process that induces thermal stress in the fabrication of microelectromechanical system (MEMS) devices. One solution to this problem is attaching a portion of the die to the package. In such partial die bonding, the lack of control over the spreading of the adhesive can cause non-uniform attachment. In this case, asymmetric packaging stress could be generated and transferred to the die. The performance of MEMS devices, which employ the differential outputs of the sensing elements, is directly affected by the asymmetric packaging stress. In this paper, we proposed a die-attach structure with a pillar to reduce the asymmetric packaging stress and the changes in packaging stress due to changes in the device temperature. To verify the proposed structure, we fabricated four types of differential resonant accelerometers (DRA) with the silicon-on-glass process. We confirmed experimentally that the pillar can control the spreading of the adhesive and that the asymmetric packaging stress is considerably reduced. The simulation and experimental results indicated that the DRAs manufactured using glass-on-silicon wafers as handle substrates instead of conventional glass wafers have a structure that compensates for the thermal stress.

The ring laser gyroscope (RLG), a representative type of optical gyroscope, exhibits a lock-in region in which very small angular velocity inputs cannot be measured due to backscattering from the mirrors. Generally, this lock-in effect is mitigated by applying a high-amplitude sinusoidal vibration to the gyro body. The mechanical device used to induce this sinusoidal vibration is referred to as a dither. Dithers vary in configuration depending on the size of the gyro; while single-axis dithers are applied to gyros with relatively large optical paths, a cluster dither—which simultaneously applies sinusoidal vibrations to three-axis gyroscopes—is used for those with smaller optical paths. Unlike in the single-axis dither, the gyro body is mounted on the cluster dither at a specific angle. Furthermore, while the dither fixing hole in a single-axis dither is located at the center of the gyro body, it is positioned on the periphery in a cluster dither. Consequently, the center of rotation for a cluster dither is located at the center of the dither itself, rather than coinciding with the center of the gyro body. To increase the natural frequency of the cluster dither with such a configuration, this paper proposes a design employing a partially tapered non-uniform and heterogeneous cantilever beam, rather than the uniform and homogeneous cantilever beam used in conventional single-axis dither spokes, and presents a corresponding natural frequency analysis method. The accuracy of the proposed natural frequency analysis method is validated through modeling and simulation (M&S) and through experimental testing of fabricated prototypes.

In this paper, to achieve the required angular velocity amplitude of a cluster dither used with an RLG having an optical path of approximately 10 cm, an equation for the angular velocity amplitude of the cluster dither was derived and the design variables affecting the angular velocity amplitude were analyzed theoretically. The analysis indicated that increasing the angular velocity amplitude requires optimization of the driving-PZT attachment position, reduction in the effective end mass, and consideration of the equivalent Q-factor of the dither structure. Based on the theoretical analysis, a cluster dither was designed and fabricated, and test evaluations were performed to validate the proposed angular velocity amplitude prediction method. The cluster dither was fabricated from SUS304 and employed spokes with a uniform geometry. Validation of the proposed angular velocity amplitude analysis and design method through M&S and test evaluation yielded a mean angular velocity amplitude prediction error of 4.1% relative to measured values when the equivalent Q-factor determined from testing was applied.