Microwave sintering has the characteristics of fast, sensitive, energy saving and efficiency, which has become an indispensable part in the preparation of NTC thermistor. Microwave sintering is to absorb microwave energy by coupling microwave directly with atoms or molecules inside the material, so as to heat the material itself, without heat conduction to heat up. In this way, microwave energy can be effectively used, energy consumption can be reduced, which can realize the rapid heating and cooling of the material. At the same time, due to the difference of dielectric constant, the absorption of microwave energy by different atoms or molecules is different, which can realize the selective heating of different components of the material and achieve the purpose of functional tailoring.

EXSENSE Electronics introduces a microwave sintering method of NTC thermistor material. The NTC thermistor material prepared by this method has the characteristics of small grain size, small pores and uniform distribution; Moreover, microwave sintering can effectively reduce the sintering temperature, sintering time and energy saving, greatly shorten the production cycle, and improve the production efficiency of NTC thermistor. The specific operation steps are as follows:

First, prepare NTC thermistor ceramic material of binary system or ternary system or quaternary transition metal oxide;

Second, use conventional co-precipitation method to make prepared NTC thermistor ceramic materials into raw body;

Third, put the raw body into the insulation body, then the whole insulation body is put into the multi-mode reaction chamber microwave sintering device, and the sintering is carried out under the power of less than 2.5 KW. In the sintering process, the temperature is raised to 1150℃±50℃ at 5~15℃/min, and the temperature is kept constant for 30 minutes. Then, after the temperature is cooled to 700℃ at 8℃/min, the microwave source is turned off for natural cooling, obtain the uniform and compact NTC thermistor material without cracking.

Fourth, in sintering, NiCrAl alloy pipe is used to shield microwave thermocouple temperature measurement, use computer to collect temperature values.

The microwave sintering method of NTC thermistor material has the following characteristics:

First, the 36 hours of conventional sintering process is shortened to 4 hours of microwave sintering process. The uniformity and consistency of the material are improved due to the microwave sintering is a whole heating process, and the consistency of the resistance value and B value is great. This process has the advantage of saving energy and time, and greatly shortens the process production cycle, so as to improve the production efficiency of NTC thermistor.

Second, the yield of NTC thermistor resistance within 1% is increased from 15%~45% of conventional sintering process to 50%~60% of microwave sintering process; The resistance value within 2% is increased from 60%~75% of conventional sintering process to 80%~85% of microwave sintering process, which improves the yield of high-precision components of NTC thermistor and thus improves the production efficiency.

Third, the material parameter B value can be adjusted within 2% by adjusting the heating rate under the premise of not changing the constant temperature and time, which can not be achieved by conventional sintering process.

EXSENSE Electronics Technology Co., Ltd. has been focusing on the production of NTC thermistor for 14 years, NTC thermistor researched and developed by EXSENSE Electronics, with high precision, rapid response, cost-effective, etc., which is widely used in cold chain transportation, smart home, medical equipment, new energy and other fields.