In the sapphire substrate processing, the first step is to remove the sapphire crystal rod with a diamond trepanning drill. The main process of sapphire cutting is to cut sapphire crystal by the diamond cutting edge at the top of the trepanning drill. The chip generated is discharged continuously through the chip removal channel of the trepanning drill, and finally, the crystal rod with the required size is obtained.
Due to the brittleness of sapphire, the precision of the diamond bit is very high in the nesting process. Generally, there are 2-inch (refers to the inner diameter of φ54mm, the same below), 4-inch (φ103mm), 6-inch (φ154mm) and 8-inch (φ204mm) bits corresponding to 2-inch, 4-inch, 6-inch and 8-inch of the substrate. At present, 2-inch trepanning drills have basically been domesticated, while 4-inch and more than 6-inch diamond trepanning drills still need to be imported.
Diamond casing drill belongs to a kind of thin-walled drill. One of the technical difficulties is how to control the bit accuracy, including the drill pipe accuracy, cutter head accuracy, welding accuracy and subsequent processing accuracy. The jitter exceeding the accuracy requirements will cause cracks in the crystal bar and affect the subsequent production. Moreover, with the development of sapphire substrates in the direction of the thinner and larger direction, the requirements of diamond trepanning drill are higher and higher.
Therefore, the development of a high-precision diamond bit is an urgent problem to be solved in the LED industry.