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This paper describes a tensile test of Su-8 to investigate the size effect on mechanical properties. The Su-8 is often used in micro-electro-mechanical systems(MEMS) devices. A non-contact position measuring system based on the principle of capacitance micrometry with 0.1㎚ resolution for displacement measurement was used. The tensile tests were performed using the developed tester and specimen. The specimen were made with dimensions of 2000㎛ long, 2 kinds of thickness, 9, 11㎛ and 3 kinds of width, 50, 100 and 150㎛. Behaviors of Su-8 have the 3kinds of stress-strain curve, showing characteristics brittle, ductile and polymer. However, it was found that the mechanical properties of Su-8 did not have an effect on thickness and width.
This paper presents high cycle fatigue properties of an Al-3%Ti thin film, used in a RF (radio-frequency) MEMS switch for a mobile phone and also describes new test method for obtaining static and dynamic characteristics of thin film and reliability evaluation method on MEMS device with thin film developed by authors. Durability should be ensured for such devices under cycling load. Therefore, with the proposed specimen and test procedure, tensile and fatigue tests were performed to obtain mechanical and fatigue properties. The specimen was made with dimensions of 1000㎛ long, 1.0㎛ thickness, and 3 kinds of width, 50, 100 and 150㎛. High cycle fatigue tests for each width were also performed, from which the fatigue strength coefficient and the fatigue strength exponent were found to be 193㎫ and ?0.02319 for 50㎛, 181㎫ and ?0.02001 for 100㎛, and 164㎫ and ?0.01322 for 150㎛, respectively. We found that the narrower specimen is, the longer fatigue life of Al-3%Ti is and the wider specimen is, the more susceptible to stress level fatigue life of Al-3%Ti was.
Mechanical property evaluation of micrometer-sized structures is necessary to help design reliable microelectromechanical systems(MEMS) devices. Most material properties are known to exhibit dependence on specimen size and such properties of microscale structures are not well characterized. This paper describes techniques developed for tensile testing of materials used in MEMS. Epi-polycrystalline silicon is currently the most widely used material, and its tensile strength has been measured as 1.52GPa. We have developed an uniaxial testing machine for testing microscale specimen using electro-magnetic actuator. The field magnet and the moving coil taken from an audio-speaker were utilized as the components of the actuator. Structure of specimen was designed and manufactured for easy handling and alignment. In addition to the static tensile tests, new techniques and procedures for measuring strength are described.
Reliability problem in inkjet printhead, one of MEMS, is also very important. To eject an ink drop, temperature of heater must be high so that ink contacting with surface reaches above 280℃ on the instant. Its heater is embedded in the thin multi-layer in which several materials are deposited. MEMS processes are the main sources of residual stresses development. Residual stress is one of the factors reducing the reliability of MEMS devices. We measure residual stresses of single layers that consist of multiplayer. FE analysis is performed using design of experiment(DOE). Transient analysis for heat transfer is performed to get a temperature distribution. And then static analysis is performed with the temperature distribution obtained by heat transfer analysis and the measured residual stresses to get a stress distribution in the structure. Although the residual stress is bigger than thermal stress, thermal stress is more influential on fatigue life.
It is well known that the targeted fuel efficiency could only be achieved by more than 40% reduction of the vehicle weight through improved design and extensive utilization of lightweight materials. In order to obtain the goal of the weight reduction of automobiles, the researches about lighter and stronger spring link have been studied without sacrificing the safety of automotive components. In this study, the weight reduction design process of spring link could be proposed based on the variation of von-Mises stress contour by substituting an aluminum alloys (A356) having tensile strength of 245 MPa grade instead of SAPH440 steels. In addition, the effect of the stress and stiffness on shape variations of the spring link were examined and compared carefully. It could be reached that this approach could be well established and be contributed for light-weight design guide and the safe design conditions of the automotive spring link development.
In this work, a testing system was developed to improve the reliability of print head and some print heads were tested. The print head developed is a thermally driven monolithic inkjet print head that consists of dome-shaped ink chambers, thin film nozzle guides and poly-silicon heaters of an omega shape integrated on the top surface of each chamber. The testing system developed can automatically detect a failure of heater using Wheatstone bridge circuit. We tested various models to develop more reliable print head. The thicker the heat transfer layer was, the longer the life of print head was. The thicker the heat insulation layer was, the longer the life of print head was.
This paper presents a novel experimental method to investigate the strength of material, Al-3 Ti, which is commonly used in RF(radio frequency) microelectromechanical systems(MEMS) switch. The experimental method involves the development of a new tensile loading system. A non-contact position measuring system based on the principle of capacitance micrometry with 0.1㎚ resolution for displacement measurement. And new specimen was designed and fabricated to easily manipulate, align and grip a thin-film for a tensile test. The material used in this study was Al-3 Ti thin film, which was used in RF switch. The thickness of the thin film is 1.1 m and 3 kinds of width were tested to get mechanical properties.