As one of the refine functional ceramics, the micro-structure and macro-performance such as mechanics and electricity of NTC thermal semiconductor ceramics, depend to a large extent on the characteristics of powder raw materials, such as particle size, shape, uniformity, chemical composition, etc.. In recent years, the IT industry has developed rapidly, automotive and home appliance products have put forward higher requirements for the consistency and reliability of NTC thermistor.
In order to produce high-quality NTC thermistor, one of the keys is to achieve ultra-pure, ultra-refine and uniform of powder raw materials. EXSENSE Electronics Technology Co., Ltd. introduces an NTC thermal powder, which is prepared by comprehensive control of co-precipitation reaction pH value, temperature, reactant concentration and adding an appropriate amount of surfactant. It greatly improves the repeatability, consistency and stability of thermistor materials. In the mass production of NTC thermistor, the yield, interchangeability, stability and reliability of thermistor are improved. The preparation method of the powder is as follows:
First, the 1.0 M ionic mixed solution prepared of 3 moles AR manganous nitrate, nickel nitrate, magnesium nitrate, aluminium nitrate, the mole percentage of each component is manganese: nickel: magnesium: aluminum = 35: 20: 30: 5-15;
Second, the 1.5 M precipitant solution prepared of 8 moles AR ammonium bicarbonate, the solution is adjusted to pH 7.0 with ammonia solution, and surfactant with weight percentage of 0.5% PEG molecular weight of 400 and 0.5% PEG molecular weight of 1500 are added to the precipitator;
Third, when the reaction temperature is 30℃, the ionic mixed solution is evenly added into the precipitant under intense agitation to make the co-precipitation reaction occur;
Fourth, after the co-precipitation reaction completed, the precipitate is washed with deionized water for 3 times, and the precursor powder is obtained by dehydration and filtration with anhydrous ethanol;
Fifth, after grinding, the precursor powder is decomposed at 400℃ for 2 hours and pre-sintered at 650℃ for 2 hours;
Sixth, the NTC thermistor ceramic material is prepared by cold isostatic pressing at 2.0MPa/cm2 after the powder is pre-molded and sintered at 1150℃ for 2 hours;
Seventh, NTC thermistor chip is obtained by slicing ceramic material by conventional technique, printing electrode layer on both sides;
Eighth, NTC thermistor is obtained by epoxy resin coating process.