Novel shear strength evaluation of MEMS materials using asymmetrical four-point bending technique

This paper describes a novel shear testing technique for MEMS materials based on an Asymmetrical Four-Point Bending (AFPB) method [1]. This research has newly developed a shear tester and a AFPB test specimen that are able to apply simple shear stress loading to a micro single crystal silicon (SCS) specimen with “U” shaped notches (U-notches), in order to estimate shear strength and to observed fracture behavior for the SCS specimens under shear stressing. Consequently, we have, for the first time, succeeded in evaluating the shear strength and shear strain of SCS on a microscale. Averaged shear modulus of SCS was obtained 53.7 GPa in [112] direction on (110) plane, which was close to theoretical value. The shear strength of SCS ranged from 1.0 to 1.3 GPa. The fracture behavior under the shear stressing was observed. The crack initiated on the slip plane at the bottom of U-notches, whereas it propagated perpendicularly to the maximum principal stress direction predicted by FEM.