Thermal Stress Analysis of Chip with Pressure Sensor Embedded in Accelerometer

The monolithic integrated sensing chip is developed not only to fulfill but expand more territories of applications, including consuming electronic devices and automotive application. Therein, the thermal stress generated during packaging process is an inevitable concern for reliability of chip. This study focuses on the thermal stress generated during the die-attached stage for microelectromechanical systems (MEMS) chip with a pressure sensor embedded in an accelerometer. The commercial software ANSYS was used to build finite element model of chip and to simulate the condition during the die-attached stage. The thermal stress distribution within the chip structure is discussed; especially, the adhesive between device and PCB is critical for package level reliability, to identify the relationship between various parameters of adhesive and the thermal stress, including material properties and thickness variation. The results from the finite element analysis indicate that the maximum von Mises stress of adhesive in device is more sensitive to Young's modulus than coefficient of thermal expansion (CTE) and Poisson's ratio. The maximum difference between higher and lower Young's modulus is over 3 times. Moreover, the thicker adhesive could reduce the maximum von Mises stress reduction of adhesive in chip. This study for the thermal stress analysis of chip by finite element model with variations of material properties and geometric parameter of adhesive could provide a suggestion of adhesive selection for these chips.