Extraction of Thermal Packaging Stress via Intrinsic Silicon on Glass Stress Measurement

Prediction and measurement of MEMS packaging stress are challenging due to the complex material stack. We decompose the thermal packaging stress of Silicon-on-Glass (SoG) sensors by referencing regularly mounted dies to a no die-attach sensor in this work, for the first time. We employ a 3x3 capacitive strain gauge array and measure the intrinsic stress of an SoG sensor over a 60°C temperature range. We show that the intrinsic SoG normal strain is tensile (~0.2-0.25 µStrain/X’) since Si CTE is lower than glass. The die-attaches (silver-filled epoxy and stiff AuSn solder) increase the shear and normal strain up to 10X and 2X, respectively, and cause strain nonuniformity and hysteresis over temperature.