| Research Abstract |
Much attention has been paid to a development of micro-sensors and micro-actuators on the order of sub-millimeter size (around 0.01-1mm), which are necessary for micro electrical/mechanical system (MEMS) such as a micro-machine. In this study, we developed a powder jet process, which is one of applications of abrasive jet machining. In this process, micro-particles ( φ 0.1-several μm), which are accelerated by a carrier gas, impinge with a high velocity and accumulate onto a substrate under vacuum or atmospheric condition, and forms thick film. Though the deposition rate is large enough to manufacture a functional structure of sub-millimeter size, there are problems that the deposition rate and mixture ratio, which are related to form accuracy and a density of the structure, are unstable. This is because a mixing and blasting mechanism of carrier gas and micro-particle is inadequate. Last year, we have developed the powder jet device that can blast micro-particles quantitatively and in
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termittently under vacuum condition, and experimented with the device. However, because there are various limitations under vacuum condition, taking practical use into consideration, powder deposition under atmospheric condition is more useful than under vacuum condition. Thus, a possibility of a powder deposition under atmospheric condition was confirmed. Next, we investigated a transition diameter of a particle, at which the mechanism changes from a material removal to a deposition. Furthermore, influences of blasting conditions such as blasting velocity and pressure, and matrials of powers and workpiece material on adhesive strength of formed thick film were investigated. The results of the experiments show that the transition diameter of particle is about 2.0μm and a smaller particle shows an adhesion phenomena when blasting alumina or silicon carbide particles to glass or silicon substrate under atmospheric pressure. And deposition height became stationary after several seconds and reached 20-120μm in thickness. And it becomes clear that kinetic energy of blasted particles and hardness of a substrate workpiece have a large influence on adhesive characteristics. In addition, we suggest a new evaluation method of mechanical properties of the film from a difference of micro-hardness and dynamic hardness values. In this method, the hardness of the formed film on a silicon substrate is bigger than on a glass. Furthermore, it is confirmed that electronic industry materials, such as PZT or ferrite, can be deposited under atmospheric pressure. Less
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