Reliability analysis of sandwich microdisplay packaging using an integrated interferometry system

This article presents the reliability study of sandwich microdisplay packaging using an integrated interferometry system. In a microdisplay die with a gaseous cavity, the hermeticity of the microdisplay die can be tested non-destructively and the leak rate quantitatively checked to 10^-7 ccatm/s by creating a pressure difference between the cavity and an external vacuum chamber. The warpage changes in the face and base plates resulting from the differential pressure was measured real-time simultaneously by the Twyman-Green and Newton Rings laser interferometry methods. Finite element analysis predicted warpage and stress distributions in the wafer package, as well as identified the key effects of the properties of components used in post wafer level packaging. The effect of elastic modulus of die attach materials on the reduction of stress and warpage build-up was studied. Failure mechanisms resulting from warpage stress were also discussed. The hermeticity and warpage analysis for sandwich microdisplay packaging contributes to the design, material selection and reliability testing of the microdisplay packages.