Structural reliability of SU-8 material for MEWS application

Mechanical properties of SU-8 over the range of temperature, -50 to 250°C, were measured. Traditional tension test is performed with the dog-bone specimens using microfabrication techniques. The bulk properties such as elastic modulus, Poisson's ratio and tensile strength are obtained in various temperatures. Bulge test is performed using SU-8 membrane constrained by silicon wafer. Pressure is applied to the membrane, and by analyzing the deflection of membrane, the elastic modulus and residual stress of SU-8 thin film are acquired. The relationship between applied pressure and deflection is obtained by changing some geometric parameters such as membrane thickness and diameter. The interfacial fracture toughness between SU-8 and silicon will measured using the membrane structure. The interfacial toughness obtained from the experiments will be compared with the strain energy release rate from finite element analysis, and the failure analysis at the interface under the actual thermal fatigue environment will be investigated using a numerical model.