A workpiece descent type of multi-wire saw was used for processing of silicon wafers for a solar cell panel. This slicing method used a working fluid including abrasive grains, which is called a slurry. This slurry was carried to the processing area with wire and supplied in the processing area. The processing characteristics of a multi-wire saw were influenced by both slurry behavior and supply method. In this study, the slurry behavior in slicing grooves of a rectangular workpiece was observed with a high-speed video camera. The relationships between slurry behavior in the slicing grooves and slurry supply method at the workpiece with a descent type multi-wire saw are discussed.

View full abstract

To reduce kerf loss and wafer thickness, wire electric discharge machining (W-EDM) has been studied as a new method for slicing of polycrystalline silicon ingots. The EDM-affected layer with wire material on the sliced surface formed during W-EDM must be removed. In this study, a blasting process was applied to remove the affected layer. Aluminum oxide and silicon carbide grains 10 – 40μm in mean diameter were used as the blasting media. The results indicated that blasting with WA#1000 abrasive could remove the affected layer and also make the wafer surface smoother than that sliced with a multi-wire saw. Energy dispersive X-ray analysis indicated elimination of contamination by elements such as copper and oxygen on the blasted wafer. The etch rate of the blasted wafer was higher than that before blasting, and this result supported those of element analysis. A solar cell was fabricated from blasted silicon wafer sliced by W-EDM.

View full abstract

Mechanochemical superabrasive stone containing CeO₂ (i.e., cBN/CeO₂ stone), which oxidizes steel, was developed and its characteristics were evaluated through the superfinishing of bearing steels. Experiments showed that cBN/CeO₂ stone produced less subsurface damage and smaller compressive residual stress than cBN stone, and produced smooth surface with negative skewness because of the synergistic effect of the mechanical action of the cBN abrasive and chemical action of the CeO₂ abrasive. Those results indicate that cBN/CeO₂ stone can finish bearing steel surface with high wear resistance, fatigue strength, corrosion resistance, and sufficient oil dams.

View full abstract

To develop a conductive bond grinding wheel capable of efficiently grinding high-quality surfaces in ELID grinding, the fabrication conditions of a cast iron bond diamond grinding wheel using the SPS method were reviewed and grinding wheel characteristics were investigated. The grinding wheel was fabricated using cast iron powder and diamond abrasives with average grain diameters of 4μm and 12μm, respectively, with an SPS machine. Firing experiments indicated that high-strength cast iron bond diamond grinding wheels can be made under SPS conditions with a welding pressure of 600 MPa and firing temperature of 570°C. Grinding experiments of cemented carbide alloy and sapphire were conducted with the prototype grinding wheel, and the results showed that the grinding wheel is effective for creating high-quality surfaces for high-strength materials.

View full abstract

Recently, the demand for polishing pads that can be applied to a wide range of polishing conditions has increased rapidly. To meet these demands, the influence of the relative speed between the polishing pad and workpiece on the removal rate was discussed based on consideration of the lubrication conditions. Pad specifications for achieving high finishing efficiency were clarified and a structure-controlled polishing pad was developed based on these specifications. A series of finishing experiments for optical glass indicated that high finishing efficiency and good frictional characteristics were obtained under a wide range of pad rotational speed conditions.

View full abstract