Tdg Company Large Size Sapphire Crystal Growth Of C To Control System Design And Implementation

It is relatively easy to growing crystal along A-axis that the natural growth direction of sapphire. Also it is the general direction for current domestic crystal growing. Sapphire is most widely used in the LED market, but the orientation of LED substrate material is C-plane, so we need to core the A-axis ingot crosswise. On this situation, material utilization is low because of the columnar bubbles in the center of the A-axis ingot. Most mainstream crystal growing method at home and abroad is kyropoulos method(KY).However, it depends on the skills of operators,and the degree of equipment automation is low, high skill operators can make high quality sapphire ingot, but the poor quality ingot made by inexperienced operators always be scrapped. Due to uneven level of operators, the qualification rate of crystal growing is unstable.The study of the thesis is about the technique and technology of growing big dimension crystal in C-axis, and designed the control system. The main research contents is:1, Propose a new heating mode, based on the study of C-plane large-size sapphire crystal structure and thermal heating design. Using the double heater system of sides and bottom instead of the single-cage heater to enhance the crucible melt temperature uniformity; Optimize the thermal field structure by transform the heat shield into 45-degree angle, it reduces the vertical temperature gradient inside the crystal and the probability of crystal upper cracking; Using the new insulation materials(zirconia fibers) to improve temperature uniformity which can save about 20% of energy consumption.2,Study on automatic control of single crystal sapphire furnace growing big dimension crystal in C-axis. The control of crystal straight equal is the core of automatic control system, it is mainly influenced by temperature and micro-pulling speed, accurate control of the temperature of the crucible is the key. Use computer control technology and MSP430F149 SCM controller to get feedback value with the help of thermocouple sensor A / D conversion. Use feedback value and set value’ PID calculation to get the control volume, so as to control the temperature of the crucible effectively.3, The control system include the temperature control unit and micro-pulling unit.Every unit includes data acquisition, parameter setting, PID control module, circuit output control module, curve setting and PC serial communication unit. The measurement modules send analog voltage to SCM as the real-time data of the sapphire straight diameter; SCM converts the analog voltage into the digital data that control system can read; SCM calculate the real-time control data with procedures nonlinear incremental PID control algorithm, through the way of combining real-time acquisition of diameter and a pre-set diameter. Then use the data to change the output drive DC, adjust micro-pulling speed, ensure the sapphire ingot diameter meet the pre-set value, with D/A control circuit and power amplifier circuit.