Ultra-precision grinding of 4H-SiC wafer by PAV/PF composite sol-gel diamond wheel

To eliminate the deep scratches on the 4H-SiC wafer surface in the grinding process, a PVA/PF composite sol-gel diamond wheel was proposed. Diamond and fillers are sheared and dispersed in the polyvinyl alcohol-phenolic resin composite sol glue, repeatedly frozen at a low temperature of −20°C to gel, then 180°C sintering to obtain the diamond wheel. Study shows that the molecular chain of polyvinyl alcohol-phenolic resin is physically cross-linked to form gel under low-temperature conditions. Tested by mechanical property testing machines, microhardness tester, and SEM. The results show that micromorphology is more uniform, the strength of the sol-gel diamond wheel is higher, the hardness uniformity is better than that of the hot pressing diamond wheel. Grinding experiments of 4H-SiC wafer were carried out with the prepared sol-gel diamond wheel. The influence of grinding speed, feed rate, and grinding depth on the surface roughness was investigated. The results showed that by using the sol-gel diamond wheel, the surface quality of 4H-SiC wafer with an average surface roughness Ra 6.42 nm was obtained under grinding wheel speed 7000 r/min, grinding feed rate 6 µm/min, and grinding depth 15 µm, the surface quality was better than that of using hot pressing diamond wheel.

Theoretical Derivation of Mean Cutting-Point Space of Grinding Wheel

In a surface grinding process, a successive cutting-point space of grinding wheel affects the maximum abrasive grain depth of cut, which is a major factor affecting grinding characteristics such as the grinding forces and temperature. These characteristics degrade the productivity and machining accuracy. Therefore, we have to clearly define the successive cutting-point space. There are, however, few reports on the derivation method of the theoretical formula since abrasive grains inside the wheel are randomly distributed. This study aimed to theoretically derive the mean cutting-point space and to clarify the successive cutting-point space. We proposed a new derivation method for the mean cutting-point space, which was measured by mapping the diamond wheel surface using an EPMA. The theoretically derived mean cutting-point space was then compared with the measurement results.