Evaluation of microfracture toughness and microcracking with notch tip radius of Si film structure for microactuator in hard disk drives

The technologies developed for macroscale testing are not necessarily applicable to evaluate the mechanical properties of structures with dimensions comparable to those of typical microsystems such as sensors and actuators. An electrostatically actuated test device was designed to evaluate microfracture at sharp notch of Si film structures used for microactuators in hard disk drives (HDDs). The test device employs a notched beam that is fully integrated with an electrostatic actuator. This allows tests without the need of external loading instruments and without influences from external sources. Using the proposed test device, the apparent microfracture toughness of Si thin film was analyzed by considering the notch tip radius effect. Below the critical notch tip radius, the apparent fracture toughness is similar to intrinsic toughness measured by a precracked test device. Microcrack initiation near the notch was detected from the shift in the resonant frequency, which is related to the stiffness change.