Research on Force-Frequency Coefficient of Square Quartz Crystal With Encapsulation Body

Because the square quartz crystal is very sensitive and easily affected by the environment, it needs to be encapsulated to maintain the performance of the sensor. However, the characteristics of its encapsulation structure will change the boundary conditions of the crystal, which makes it difficult to determine the sensitivity and measurement range of the sensor. In order to solve this problem, the relationship between the force-frequency coefficient and the stiffness of the encapsulation structure is established and verified by finite element analysis, and experiments are presented in this article. The experiment shows that the encapsulation structural stiffness and the force-frequency coefficient of the crystal are equivalent, so the design results of the encapsulation structural stiffness can be used to express the force-frequency coefficient of the sensor. In addition, SEM analysis was used to verify that the structural characteristics of the encapsulation were better when the thickness of the adhesive was thinner, and the influence of the thickness of epoxy and AuSn on the sensor performance was analyzed by FEA.