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A new type of fatigue testing machine for micro-sized specimens for MEMS applications has been developed. This fatigue testing machine consists of a magnetostrictive actuator which is able to impart small displacements to a specimen upto 20 νm with resolution of 5 nm. The actuator is connected to a metal shaft and a diamond tip of 5 νm in radius is attached to the end of the shaft. Small displacements are applied to the specimen through the diamond tip. This makes it possible to construct a high stiffness loading fixture. The magnitude of load applied to the specimen is measured by a strain gauge type load cell with a load resolution of 10 νN. The specimen stage and load cell can be moved to adjust the loading position precisely by a stepping motor at a translation resolution of 0.1 νm. Cantilever beam type specimens with dimensions of 10 × 12 × 50 νm3 were prepared from a Ni-P amorphous thin film by focused ion beam machining. Very small cyclic load (ΔP = 0.1 - 40 mN) was able to be applied to the specimen successfully. This machine appears to be promising for evaluation of fatigue properties for micro-sized specimens for MEMS applications.

Fatigue life and fatigue crack propagation tests have been performed on microsized Ni-P amorphous alloy specimens to investigate the fatigue properties of this material. The material used was a Ni-11.5 wt%P amorphous thin film. The specimens tested were cantilever-beam-type specimen with dimensions of 30 × 12 × 50 µm 3 prepared by focused ion beam machining. Notches with a depth of 3 µm were introduced in some specimens. The entire set of fatigue tests was performed using a newly developed fatigue testing machine in air at room temperature under a constant load ratio of 0.1. The fatigue life curve was obtained for unnotched specimens, and the fatigue strength of the specimen was determined to be approximately one-third of the static bending strength. Fatigue crack propagation tests were performed using notched specimens. Fine equispaced markings were observed on the fatigue surface. These markings are aligned perpendicular to the crack growth direction, and are considered to be striations. Therefore, even in microsized amorphous alloys the crack is deduced to propagate by cyclic plastic deformation at the crack tip.

Development of micromachines and MEMS (microelectromechanical system) devices are making steady progress at present. The size of components used in these micromachines and MEMS devices is expected to be in the order of p m, and the mechanical properties of such materials may be different from those of bulk materials. Therefore, the evaluation of mechanical properties such as Young's modulus, tensile strength and fatigue properties is essential for the design of micromachines and MEMS devices. Young's modulus, fracture stress and hardness of thin films and small elements of silicon single crystals have been measured [la]. In addition to modulus and strength of such mimsized

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