The working temperature of the diffusion furnace is generally hundreds of degrees to thousands of degrees, and the furnace temperature is required to be kept warm to the specified time within a certain control range, and the diffusion process curve is multi-step. Temperature has a decisive influence on the process parameters of the diffusion furnace, so the accuracy of the temperature control directly affects the product quality and also affects the production efficiency of the diffusion furnace.
The diffusion furnace is essentially a resistance heating furnace, and there are two main factors that affect its temperature control accuracy. First of all, the temperature-controlled thermocouple of the diffusion furnace is used for a long time, which is easy to produce errors; Secondly, diffusion furnace temperature control methods are usually regulated by analog and digital adjustment instruments, or by microcontroller and PLC for furnace temperature control, but these control methods have some inherent shortcomings that lead to errors. In order to reduce the above two errors, improve the consistency of electronic device parameters and product yield, the diffusion furnace must be regularly tested and calibrated.
The common temperature of the diffusion furnace is between 400~1200°C, and we use S type thermocouple, which are characterized by stable thermoelectric properties and strong oxidation resistance, should be used in oxidizing or inert atmospheres. In order to further ensure the accuracy of the measurement data, the S-type thermocouple used is checked once before and after use, and its average value is taken to correct the furnace temperature measurement value.
When measuring the length of the constant temperature zone and the parameters of the constant temperature accuracy, the single-end whole-process one-time measurement method is adopted, and the measurement system is connected. After the furnace temperature rises to the temperature specified by the process and is stable, the working end of the thermocouple moves along the axis in the furnace tube to measure the temperature value of each point in the temperature zone. When moving the thermocouple, use a tape measure to measure the distance the thermocouple moves every 10 cm, and the thermocouple should move at a speed of less than or equal to 2 cm per minute. When measuring the temperature value, each point is measured for 5min, and the whole process is measured at one time, and the data measured from the inside to the outside is taken as the assessment basis, and the original record is recorded.