Rate dependent material properties of an OFHC copper film

Abstract

The material properties of OFHC(Oxygen Free High thermal Conductivity) film with a thickness of 0.1 mm was evaluated at the strain-rates ranging from 0.001/s to 500/s using High-Speed Material Micro-Testing Machine(HSMMTM). The high strain-rate material properties of thin films are important especially for evaluation of structural reliability of micro-formed parts and MEMS products. The high strain-rate material testing methods of thin films, however, are not yet thoroughly established while testing methods of larger specimens for electronics, auto-body, train, ship and ocean structures has been well-established. For evaluation, a HSMMTM has been newly developed to conduct high-speed tensile tests of thin films. The machine developed has a capacity of sufficiently high tensile speed with an electromagnetic actuator, a novel gripping mechanism and an accurate load measurement system. The OFHC copper film shows high strain-rate sensitivity in terms of the flow stress, the fracture elongation and strain hardening. They increase as the tensile strain-rate increases. The quantitative comparison would provide material data at high strain-rates for design and analysis of micro-appliances and micro-equipments.