| Summary: | 碩士 === 義守大學 === 機械與自動化工程學系碩士班 === 96 === The study is to examine how picosecond laser affects the microstructure of the thin silicon wafer. Traditionally diamond cutters are chosen to cut grooves on the silicon wafers. The method, if applied carelessly, would cause cracks at the cutting edges. In addition, extra material will be needed to compensate the material lost at the place of cut (street width). The etching process can also be chosen. But it is time consuming and the cleaning afterward is prone to cause environmental pollution. Nanosecond laser is another option. Yet its high energy density will cause large heat affect zone which is detrimental to the cutting edge. On the contrary picosecond laser uses photochemical ablation for material removal.Not much heat is generated while machining. The effect of changing its frequencies, cutting speeds, energy density, and focus points on the quality of machining processes, which include making blind holes, grooving, and planning, is studied. Surface roughness is the chosen index for machining quality. After extensive test, the following parameters are found to be best suited for machining silicon wafer: focus 1.66mm, frequency 100KHz, feed 50mm/s, energy density 1000 pulse/mm. The resulting surface roughness is Ra=0.09μm.
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