Through <Manufacturing method of high-precision and high-reliability NTC thermistor Chips-1>, we can know that the manufacturing method of high-precision and high-reliability NTC thermistor chip can improve the 1% rate of finished products of chip, and the reliability has been improved obviously. The detailed steps for this method are as follows:
1) According to the chemical formula MnNiFeCoQO, weight corresponding metal oxides, mixed ball milling, calcine into thermosensitive ceramic pre-powder;
2) Mix the thermosensitive ceramic pre-powder and the nanoscale thermosensitive ceramic pre-powder to make the mixture evenly, and mix the mixture and water to make the slurry. Wherein, the percentage of nanoscale thermal ceramic pre-powder in the mixture is 5-75wt%, the water accounts for 20-30wt% of the mixture quality;
3) The slurry is pressurized and filtrated to form a raw billet, dry the raw billet, then isostatic press the raw billet;
4) Microwave sintering the billet obtained by step 3);
5) Cutting the billet after sintering, then electrode printing, doing the heat treatment in the protective gas atmosphere;
Among them, the molar ratio of metal ions in the nanoscale thermosensitive ceramic pre-powder is the same as the molar ratio of the metallic ion in chemical formula of step 1).
The nanoscale thermosensitive ceramic pre-powder is prepared in this way: according to the the molar ratio of the metallic ion in chemical formula of step 1), compound corresponding metal ion nitrate solution, so that the concentration of each metal ion is 0.5-1mol/l, adjust its PH=7, drying with ultrasonic spray, then calcine 2-6 hours at 400-500 ℃.
As shown in step 3), in the process that the slurry pressurized and filtrated to form a raw billet, is increasing pressure and excluding water at the same time. The conditions of isostatic pressure is: static pressure 100mpa~380mpa, dwell time 1~5min.
Microwave sintering: put the billet into the microwave oven, make temperature from room temperature to 900-1100 ℃ with speed 8-15℃/min, heat preservation 30-50mins, then cooling to 450-550 ℃ with speed 1-3℃/min.
As shown in step 5), the heat treatment process is: in the protective atmosphere, Cutting the billet after electrode printing, from room temperature to 550-850 ℃, heating rate is 0.5-15℃/min, then heat preservation 1-24 hours, then cooling to room temperature with speed 1-3℃/min.
The protective atmosphere is one of helium, neon gas, argon gas, krypton Gas, xenon and nitrogen.
The Q is one type of Al, Cu, ZR, 0≤t<1, x≥0, y≥0, z≥0, and 0<x+y+z<3.
This manufacturing method has the following advantages:
1. use the ultrasonic spray drying to obtain nanoscale powder, through the mixing of raw materials, at the same time with other process steps, reduce the sintering temperature of the raw billet, so that the final resulting billet is more compact;
2. use the method of the slurry pressurized and filtrated to form a NTC Thermistor raw billet;
3. microwave sintering technology is adopted, to achieve low temperature, fast and efficient sintering;
4. the specific heat treatment methods under the protective atmosphere is adopted.