Peiqi Ge

Monocrystalline silicon is an important material for processing electronic and photovoltaic devices. The fixed diamond wire sawing technology is the first key technology for monocrystalline silicon wafer processing. A systematic study of the relationship between the fracture strength, stress and breakage rate is the basis for thinning silicon wafers. The external vibration excitation of sawing machine and diamond wire lead to the transverse vibration and longitudinal vibration for silicon wafers. The transverse vibration is the main reason of wafer breakage. In this paper, a mathematical model for calculating breakage ratio of silicon wafer is established. The maximum stress and breakage ratio for as-sawn silicon wafers are studied. It is found that the maximum amplitude of the silicon wafers with the size of 156 mm × 156 mm × 0.2 mm was 160 μm during the diamond wire sawing process. The amplitude, maximum stress and breakage rate of the wafers increased with the increase of the cutting depth. The smaller the silicon wafer thickness, the larger of silicon wafer breakage ratio. In the sawing stage, the breakage ratio of the 156 mm × 156 mm section with a thickness of 0.15 mm of silicon wafers is 6%.

The third generation of superhard semiconductor materials, represented by single-crystal SiC, is used widely in microelectronics due to their excellent physical and mechanical properties. However, their high hardness and brittleness become the bottleneck of their development. Diamond wire saw (DWS) has become the mainstream tool for sawing hard and brittle crystal materials. However, the diamond abrasive is consolidated on the core wire through resin or electroplated nickel, and the holding strength is not high. When sawing superhard crystal materials, the efficiency is low. In order to improve the sawing efficiency of superhard crystal materials, it is of great significance to improve the wear resistance of wire saw and the holding strength of abrasive particles. Electro-spark deposition (ESD) can deposit electrode materials on the substrate with low heat input to achieve metallurgical bonding between metal materials. It can effectively improve the gripping strength of the abrasive grains. And the sawing ability of the wire saw to make the consolidated DWS by the ESD process. In this paper, the ESD equipment has been designed according to the characteristics of the ESDDWS process. The discharge gap size and electrode consumption are monitored in real-time by a single-chip microcomputer (SCM). Orthogonal experiments were carried out for the two motion modes. The effects of process parameters, such as (A) Grain size, (B) Abrasive content, (C) Pulse duration time, (D) Compacting pressure, (E) Current, (F) Electrode diameter, (G) Pulse interval time, (H) Reciprocating times, (I) Wire feed speed, on the quality of ESDDWS were analyzed. Through the extremum difference analysis, the optimal parameter combinations of ESDDWS were obtained. The results of the validation experiment are better than the original experimental results.

Due to their excellent physical and mechanical properties, third-generation super-hard semiconductor materials (such as SiC, GaN) are widely used in the field of microelectronics. However, due to its ultra-high hardness, the machining is very difficult, which has become the bottleneck of its development. The electro-spark deposition (ESD) process can deposit electrode materials on the substrate under the condition of low heat input to achieve metallurgical bonding between metal materials. And it can improve the wear resistance, corrosion resistance, and repair the size of the workpiece. It has been widely used in the field of surface modification engineering. It can effectively improve the bonding strength of the abrasive grains, and the sawing ability of the wire saw to make the consolidated diamond wire saw by the ESD process. Due to its thin matrix and poor thermal properties, the saw wire is easy to burning or even breaking in the manufacturing process. At present, the selection of pulse interval time in the ESD process is generally determined by the duty factor. However, the pulse interval time selected according to duty factor is difficult to meet the heat dissipation requirements of electro-spark deposition diamond wire saw (ESDDWS). In this paper, two kinds of motion modes of ESDDWS manufacturing are put forward, according to the manufacturing characteristics of ESDDWS. The boundary conditions of the continuous pulse discharge of ESDDWS are established. The thermal simulations of continuous pulse discharge of ESDDWS under two motion modes are analyzed. According to the simulation results, the basis of the value of pulse interval in the ESDDWS process is put forward. The effect of pulse interval time on the mechanical performance of the wire saw is analyzed experimentally. The results show that the discharge interval time selected base on the simulation results can ensure the continuous production of the ESDDWS.