Measurement of mechanical properties of film material using out-of-plane micro-ESPI technique

Micro-mechanical properties for film material were measured by micro-strip bend test. Electrolytic copper foil 18 μm thick was used for preparation of two types of strip bend specimen 8 mm long in loading span and 1 and 2 mm wide, respectively. For these tests, a micro-strip bending system and an out-of-plane ESPI system were developed. Using these systems, bend load was applied to the specimen with an actuator controlled with the stroke resolution of 4.5 nm and out-of-plane deflection of the specimen during bend testing was subsequently measured by the out-of-plane ESPI system developed in compact and portable type. To quantitatively analyze the out-of-plane ESPI fringe patterns, four-bucket technique was used and unwrapped phase map was obtained. From the quantitative analysis of ESPI fringe, the out-of-plane deflection of the specimen was determined and the stress–strain relationship for this material was obtained. From the relationship, tensile properties, including elastic modulus and yielding strength and tensile strength, could be determined.