ORAL REFERENCE: ICF10 0193OR FRACTURE TOUGHNESS TESTS FOR MICRO-SIZED SPECIMENS K. Takashima1, Y. Higo1 and M. V. Swain2 1 Precision and Intelligence Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan. 2 Faculty of Dentistry and Department of Mechanical & Mechatronic Engineering, The University of Sydney, Australian Technology Park, Everleigh NSW 1430, Australia. ABSTRACT A fracture toughness testing method appropriate to micro-sized specimens has been designed and fracture tests have been performed on micro-sized specimens for MEMS applications. Cantilever beam type specimens with dimensions of 10 x 10 x 50 µm3 were prepared from a Ni-P amorphous thin film and notches with different directions, which are perpendicular and parallel to the deposition growth direction, were introduced by focused ion beam machining. Fatigue pre-cracks were introduced ahead of the notches. Fracture tests were carried out using a newly developed mechanical testing machine for micro-sized specimens. Fracture behavior is different between the two types of specimens. KIC values were not obtained as the criteria of plane strain requirements were not satisfied for this size of the specimen, so that the provisional fracture toughness KQ values were obtained. The KQ value of the specimen with crack propagation direction being parallel to the deposition growth direction was 4.2 MPam1/2, while that with crack propagation direction being perpendicular to the deposition growth direction was 7.3 MPam1/2. These results suggest that the electroless deposited amorphous alloy thin film has anisotropic mechanical properties. It is necessary to consider the anisotropic fracture behavior when designing actual MEMS devices using electroless deposited amorphous films. KEYWORDS Fracture toughness, Thin film, Micro-sized specimen, MEMS, Anisotropy INTRODUCTION Microelectromechanical systems (MEMS) or microsized machines are under intensive development for utilization in many technological fields such as information and biomedical technologies. These MEMS devices are usually fabricated from a thin film deposited on a substrate by suitable surface micromachining techniques, and the micro-sized elements prepared from a thin film layer are used as mechanical components. The evaluation of fracture toughness of thin films is then extremely important to ensure the reliability of MEMS devices. In addition, micro-elements on MEMS devices are considered to be subjected to load in both the direction of “in-plane” and “out-of-plane” of the thin film. The fracture toughness values for both in-plane and out-of-plane directions are thus required for actual design of MEMS devices, as the fracture toughness of thin films prepared by sputtering or other
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