Chen Feng: Application of Diamond Tools in Sapphire Processing

On May 20th, 2016, the three executive directors (expansion) meeting of the 5th China Superhard Materials Association was held in Wuhan New Beacon International Hotel. During the meeting, Chen Feng, deputy general manager of SINOMACH Seiko Co., Ltd. gave a speech entitled “Application of Diamond Tools in Sapphire Processing”. The speech report was explained in detail from four aspects: “Introduction to Sapphire”, “Sapphire Application Field”, “Diamond Tools in Sapphire Processing” and “Problems and Countermeasures in Sapphire Processing”.
The report points out that sapphire has high mechanical strength, high hardness and can withstand the decompression load during high-speed movement; it has good heat stability, high temperature resistance, can withstand the temperature shock caused by aerodynamic heating and height change, and the transmittance and refractive index do not follow the temperature. Significant changes occur; chemical stability, can withstand the corrosion of molten salt solution or corrosive gas, and not easy to deliquesce; high optical transmittance, can transmit ultraviolet to mid-infrared radiation; optical properties, optical scattering Small and uniform refractive index uniformity; can meet a large number of window requirements and many other excellent performance. With excellent performance, it is widely used in the following fields: 1, LED field, substrate materials, etc.; 2, window materials, watch dials, etc.; 3, wear-resistant materials, precision shafts and bearings; 4, aviation field, photoelectric window Etc.; 5, the field of defense, missile fairings, etc.; 6, medical equipment, laser radiation devices. According to the report, from the field of sapphire use, about 75% of sapphire is used in the field of substrate sheets, 10% is used in the field of optical products, 12% is used in the field of window products for electronic consumer products, and about 5% is used for national defense. Fairing, harmonics, etc. in the aerospace field. The process flow of sapphire substrate processing is: sapphire ingot--"crystal bar material--" head and tail cut--" outer diameter, crystal to flat research--"slice--" chamfered edge--"crude Grinding--"fine grinding--"CMP--" substrate sheet. The process of sapphire window processing is: single crystal growth - "掏 rod (diamond sleeve drill) - "cut square (diamond wheel or diamond line + free sand) - "slice -" rough grinding / fine grinding (Diamond Grinding Disc)--" Grinding and Polishing (Diamond Grinding Liquid, Polishing Liquid, Diamond Micro Powder, etc.)--"Second Section (Diamond Ultra-thin Cutting Wheel)--"Chamfering, Drilling and Contouring (Electroplating Diamond Grinding Head) )--"Detection--"Clean and dry--" window. When talking about "the problems and countermeasures in the processing of sapphire", the report pointed out that the refractory processing caused by high hardness and brittleness of sapphire and the high processing cost are the main problems. The processing cost of the total cost of sapphire production has stood at more than 55%. Taking a 2-inch 0.43 thick substrate as an example, the raw material cost is less than 20%, the processing cost is more than 55%, and the cost of the finished product after multi-line cutting is more than 90% is 16.5 yuan/piece (including the cost of the bar), and the rough grinding cost is 2.5. Yuan/Piece, the cost of fine grinding is 3 yuan/piece, the cost of rough casting is 2 yuan, and the cost of fine polishing is 2 yuan/piece. The overall cost after considering the yield is 30~35 yuan/piece. When it comes to "the problems and countermeasures in sapphire processing", the report gives the processing solutions for processing sapphire such as ultrasonic assisted machining, chemical mechanical processing, cold laser processing, plasma processing.
Among them, ultrasonic assisted machining is a processing method that applies ultrasonic vibration to a diamond tool or workpiece to obtain better processing performance on the basis of the relative movement of the tool and the workpiece.
Chemical mechanical processing is a process that combines chemical corrosion and machining of diamond tools. At present, chemical mechanical polishing (CMP) is relatively mature in sapphire processing. In sapphire cutting and grinding, we can also introduce this process. Sapphire has a large cutting depth and a high cutting temperature. However, higher cutting temperatures favor the sapphire chemical corrosion reaction. The progress of the chemical reaction helps to reduce the cutting temperature.
Laser processing uses "hot" laser beam cutting of microsecond short-pulse lasers; ultrashort pulse "cold" laser processing (so-called ultrashort pulse lasers have pulse durations of only a few picoseconds). "Sapphire does not produce microcracks or chipping when processing sapphire using the "hot" laser process. The "cold" processing of picosecond lasers results in higher trim quality and lower edge roughness. There is a need to further reduce the manufacturing costs of laser heads and laser processing and equipment, thereby driving the processing of the process in the sapphire industry.
Plasma processing is the processing of sapphire by the heat generated by the plasma arc. This processing method can process and cut very thin materials with high efficiency, but currently such processing equipment is expensive. Hydrogen ion cutting sheets are thinner, more economical, and more efficient, but they have not yet been fully commercialized and are the future of sapphire cutting technology.
The 6-inch sapphire substrate cut by Twin Creeks Technology's proton-injection stripping technology is 26 microns thick and 2 inches thick to 12 microns. At present, the thickness of the sapphire sheet produced by the wire cutting method is 600 microns. The 6 inch is up to about 1500 microns. The surface of the sapphire substrate formed by the gas stripping method has high flatness, and the subsequent process becomes easier. The Hyperion gas stripping method is bulky (single machine is the same room size), and the equipment investment is large, and the machine is in the experimental stage. Not sold in the market.
(This article was compiled by PPT and live recordings by Chen Feng, deputy general manager of SINOMACH Seiko Co., Ltd., "Application of Diamond Tools in Sapphire Processing", without the author's review.)

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