PRODUCT CATEGORIES

Vacuum Heat Treatment Furnace

Vacuum Sintering Furnace

Vacuum Brazing Furnace

Quartz Tube Vacuum Heat Treatment Process

1. Principle

In the production of photovoltaic infrared detectors, a closed-tube diffusion method is generally used to form a p-n junction. This method is to pack the product and the diffusion source into a quartz tube to a certain degree of vacuum, and then seal it with a hydrogen-oxygen flame. Into the diffusion furnace for diffusion. Therefore, the vacuum degree inside the quartz tube directly affects the quality of the p-n junction, and also directly affects the success or failure of the infrared device. Since the gas molecules on the inner surface of the quartz tube are mainly water vapor, CO2, O2, N2, and Ar, when the quartz tube is evacuated, the adsorbed gas is desorbed from the inner wall of the quartz tube, and its desorption capacity is affected by factors such as pressure and temperature. Influence. The lower the pressure, the higher the desorption. When the pressure reaches–a fixed value, because the adsorption rate and desorption rate of the gas on the surface of the quartz tube reach a dynamic balance, the vacuum inside the quartz tube will no longer increase at this time. As the temperature increases, the desorption rate of the gas on the inner wall of the quartz tube also increases until the next dynamic equilibrium is reached. Therefore, if the quartz tube is degassed at a high temperature for a certain period of time, the gas adsorbed on the inner surface layer will be desorbed more completely, so as to achieve the purpose of obtaining a high vacuum.

2. Cleaning Process

Before the vacuum heat treatment of the quartz tube, the necessary chemical cleaning must be carried out. First soak the quartz tube in a detergent solution of 5 coffees for 30 minutes, and then rinse it with deionized water; then put in a 4.8% hydrogen sulphuric acid solution towel without soaking for 45 minutes, rinse with deionized water and put it in 80C Dry it in an oven and load it into a vacuum system for vacuum heat treatment.

3. Process Data

Table 1 lists the data after vacuum heat treatment under different conditions.

	Heating rate (℃/min)	Degassing temperature (℃)	Degassing time (h)	Vacuum degree after degassing (Pa)	Cooling rate (℃/min)	Pressure after keeping at 100℃ for 48h (Pa)
1	–		96	1.50×10-⁶	–	–
2	2.5	100	48	1.25×10-⁶	–	1.25×10-⁶
3	2.5	250	48	1.15×10-⁶	2.0	8.15×10-⁷
4	2.5	400	48	9.50×10-⁷	2.0	7.95×10-⁷
5	2.5	500	48	8.45×10-⁷	2.0	4.50×10-⁷
6	2.5	600	48	8.50×10-⁷	2.0	4.53×10-⁷
7	2.5	700	48	8.55×10-⁷	2.0	4.51×10-⁷
8	When the quartz tube is not installed, the background positive force of the system is: 4.15×10-⁷Pa

Table 1 Data of vacuum heat treatment under different conditions

It can be seen from the above data that under the same 48h vacuum heat treatment, as the degassing temperature increases, the vacuum degree after degassing becomes better and better. This is because the higher the degassing temperature, the more thoroughly the gas on the surface of the inner wall of the quartz tube will be desorbed. However, when the temperature is higher than 500°C, the adsorbed gas has been basically desorbed. Compared with the vacuum heat treatment at 500°C, the pressure after degassing at 600°C and 700°C is no longer significantly reduced. This shows that the vacuum heat treatment at 500°C for 48 hours has basically desorbed the gas adsorbed on the inner wall surface. In addition, it can be seen from Table 1 that when the vacuum system is not loaded with quartz tube, the pressure is 4.15×10-7Pa, which can be considered as the ultimate pressure that the system can reach. After 500℃, 600℃, 700℃. After 48 hours of degassing, the temperature was lowered to 100°C and the pumping continued for 48 hours. The pressure reached about 4.50×10-7Pa, which was close to the limit pressure of the system. It shows that the vacuum heat treatment conditions of 500℃.48h are more suitable for the vacuum heat treatment of quartz tubes.