班級:碩研奈米一甲 學號:MA31V206 姓名:黃宗偉 授課教師:戴子堯 教授 燒結金剛石作為混合型放電研磨工具用於碳化矽的微機械加工上 Sintered diamond as a hybrid EDM and grinding tool for the micromachining of single-crystal SiC 班級:碩研奈米一甲 學號:MA31V206 姓名:黃宗偉 授課教師:戴子堯 教授

目錄 引言 金剛石混合型刀具的方案 實驗步驟 放電加工的結果 (1)表面形貌 (2)下層材料結構 (3)拉曼光譜與奈米壓痕深度

目錄 微細研磨的結果 (1)表面形貌的變化 (2)拉曼光譜分析 (3)刀具表面的變化 (4)刀具橫向進給的影響 6. 總結

一、引言(Introduction) SiC is very difficult to machine Currently, SiC is finished by chemomechanical polishing (CMP) SiC is electrically conductive, meaning it can be finished by electrical discharge machining

一、引言(Introduction) In this study, we attempted the EDM of SiC using sintered diamond (polycrystalline diamond, PCD) as a tool electrode. After EDM shaping, the same PCD tool was used to grind the electrical discharge machined (EDMed) surface and to remove both the subsurface damage and recast layer formed during EDM.

二、金剛石混合型刀具的方案 (Scheme of PCD hybrid tool ) PCD is a composite of diamond grains sintered with a metallic binder such as Co. In this study, after EDM, the PCD electrode was used directly as a grinding wheel for finishing the EDMed surface and removing the SSD layer

三、實驗步驟(Experimental procedures ) PCD RODS 90% 平均尺寸0.5um的鑽石顆粒 10% 作為金屬黏著劑的鈷 thermal conductivity 290 W/(m K) workpiece (single-crystal SiC wafer) Mohs hardness 9 thermal conductivity 370 W/(m K) melting point 2730℃ sublimation point 2830℃ 放電加工的電壓 轉速 70-110V 3000rpm Z軸進 給速度 Y軸進 總研磨 深度 0.1 (um/s) 2.5-25 10um

四、放電加工的結果(Results of micro-EDM ) (1)表面形貌 Fig.SEM images of EDMed SiC surfaces at (a) 70 V and (b) 110 V, showing an increase in surface crater size and depth with voltage.

四、放電加工的結果(Results of micro-EDM ) (2)下層材料結構 Fig. 3.Cross-sectional SEM images of EDMed surfaces at (a) 70 V and (b) 110 V, showing an increase in recast layer thickness with voltage.

四、放電加工的結果(Results of micro-EDM ) (3)拉曼光譜與奈米壓痕深度 Fig. 4. Raman spectra of the SiC wafer (a) before EDM and (b) after EDM. 加工前硬度 再鑄層硬度 經由奈米壓痕深度 測試得到的硬度 3.52x104Nmm2 1.97x104Nmm2

Fig. 5. Schematics of (a) material removal in EDM and (b) topographical and structural changes in both PCD and SiC.

五、微細研磨的結果(Results of micro-grinding) (1)表面形貌的變化 Fig.SEM images of the bottoms (a, c) and fringes (b, d) of EDMed cavities after plunge grinding. The voltages used in EDM were (a, b) 110 V and (c, d) 70 V.

五、微細研磨的結果(Results of micro-grinding) (2)拉曼光譜分析 Fig.Raman spectra of the workpiece surface after grinding, showing a typical SiC structure without Si or C allotropes.

五、微細研磨的結果(Results of micro-grinding) (3)刀具表面的變化 Fig.SEM images of the surface of the PCD tool (a) after EDM and (b) after grinding.

五、微細研磨的結果(Results of micro-grinding) (4)刀具橫向進給的影響 Fig9.Micrographs of (a) an EDMed cavity and (b) an EDMed and then mill-ground cavity by introducing a traverse tool feed.

Fig.Three-dimensional topographies of the bottom surfaces of the cavities shown in Fig9., (a) without and (b) with grinding.

Fig.Comparison of surface roughness resulting from different process steps using the PCD hybrid tool versus CMP.

六、結論(Conclusions ) PCD was used as a hybrid tool for micro-scale EDM and grinding of single-crystal SiC. EDM created a thick recast layer where SiC decomposed into C and Si, leading to significant surface softening.

六、結論(Conclusions ) During EDM, diamond grains began to protrude out of the PCD tool surface by the electrical discharge dressing effect, which greatly improved the tool’s subsequent ductile grinding performance. Mill grinding after EDM using the hybrid tool with a traverse tool feed enabled complete removal of the EDM-induced recast layer with a nanometer-scale surface finish (Ra = 1.85 nm)

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