LAUSR

To produce a fine, precise structure required in microelectronic-mechanical systems (MEMS), various methods have been proposed that depend on the type of material used. A recently developed production method of metal MEMS is diffusion bonding after laminating the metallic foil that had been shaped to planar form by etching.1,2) In the case of austenitic stainless steel, the high bonding temperature of approximately 1 200 K causes annealing of materials, resulting in a decrease in proof stress. Although this decrease should not be a serious problem for a component such as a heat exchanger, for components that include driving parts, such as a metal micro-pump, it might cause defects in the valve operation with low elasticity. Such high bonding temperature requires long heating and cooling times. Moreover, the components of the bonding apparatus must have high thermal resistance. These difficulties can be resolved by the development of a diffusion bonding method at lower temperature. For this study, we demonstrated the bonding of a severely plastic-deformed austenitic stainless steel at lower bonding temperature with solution treatment. Results revealed an ultra-fine grain size less than 1 μm in these bonded samples, which is expected that indicating high proof stress in the bonding components.