Manufacturing method of high-precision and high-reliability NTC thermistor chip

[0043] Example 1:

[0044] Use an analytical balance to accurately weigh 405.2g of trimanganese tetroxide, 457.04g of nickel oxide, 599.30g of ferric oxide, and 39.42g of aluminum oxide. The above mixture was ball-milled and mixed for 20h, dried, crushed and calcined at 950℃ for 2h, and then again Ball mill for 20h to obtain traditional coarse particle powder (the particle size of the powder is 1-5μm). According to the same molar ratio of metal ions, nickel nitrate, manganese nitrate, iron nitrate and aluminum nitrate were mixed into a 0.7mol/L aqueous solution, adjusted to pH=7 with ammonia water, ultrasonic spray-dried under stirring, and calcined at 450℃ for 4h to obtain Nano powder. Weigh 375g of this nano-powder and add it to the coarse-grained powder, add deionized water while stirring to make a slurry, where the added amount of water accounts for the mixed powder (ie the above-mentioned nano-powder + coarse-grained powder) 的25wt%. Press the mud in a filter press molding mold, press and hold the pressure 10Mpa for 2min, make a cylinder with a diameter of 52mm and a height of 16mm, bake at 100°C for 1h, then put it into a cold isostatic press for 300Mpa compression 2min. Then heat up from room temperature to 1050°C at a rate of 10°C/min in a microwave oven, hold for 30 minutes, then cool down to 500°C at 2°C/min, and then cool to room temperature naturally to obtain a ceramic block; use a slicer to cut the ceramic body A wafer with a thickness of 0.3mm and a diameter of 52mm is formed; silver is printed on the wafer, and then heat treated at 800°C: the prepared wafer is heated to 800°C at a heating rate of 5°C/min, and based on this The heat is kept for 24 hours, and then cooled to room temperature at a rate of 2°C/min. During the entire heat treatment process, argon gas is introduced as a protective atmosphere; then a dicing machine is used to cut into 0.8×0.8mm chips.

[0045] Randomly select 60 thermistor chips obtained by this method, and measure their resistance at 25℃. Compared with the thermistor chips prepared by the traditional method, the resistance of the chip made by the new process is within 10KΩ±1% The pass rate is 95.7%, while the pass rate within ±1% of the traditional method is 75.3%, that is, the resistance pass rate has been greatly improved. Divide the 60 chips into two parts. After soldering and packaging, one half is aged in an oven at 110°C for 1000 hours, and the other half is subjected to thermal shock 1000 times in a tank at -30~100°C. The resistance changes before and after the test are measured. The rates of change were 0.36% and 0.344%, while the values ​​of the traditional method were 0.92% and 1.09%. It can be seen that the use of the new technology can greatly improve the resistance accuracy and reliability of the NTC thermistor chip.

[0046] In this embodiment, the thermistor chip prepared according to the traditional method for comparison is prepared as follows:

[0047] 1) Use an analytical balance to accurately weigh 506.4g of trimanganese tetroxide, 571.21g of nickel oxide, 749.01g of ferric oxide, and 49.27g of aluminum oxide. The above mixture was ball milled and mixed for 20h, dried, crushed and calcined at 950℃ for 2h. Then ball mill again for 20 hours to obtain coarse particle powder (the particle size of the powder is 1-5μm);

[0048] 2) Put the above powder at 40Kg/cm 2 Perform briquetting at a pressure of 10min, and perform cold isostatic pressing on the formed bulk material, hold the pressure at 400MPa for 10min, and then sinter at a high temperature of 1250℃ for 3h;

[0049] 3) Use a slicer to cut the sintered ceramic body into discs with a thickness of 0.3mm and a diameter of 52mm; print silver on the discs, and age the resulting thermistor disc material at a temperature of 110°C for 1000 hours.

[0050] figure 1 It is a TEM image of the nano powder prepared in this example.

[0051] Example 2:

[0052] Using an analytical balance, accurately weigh 385.1g of trimanganese tetroxide, 146.48g of nickel oxide, 499.30g of ferric oxide, and 500.31g of cobalt oxide. The above mixture was ball-milled and mixed for 20h, dried, crushed and calcined at 850℃ for 2h, and then again Ball mill for 20h to obtain traditional coarse particle powder (the particle size of the powder is 1-5μm). According to the same molar ratio of metal ions, nickel nitrate, manganese nitrate, ferric nitrate and cobalt nitrate were prepared into a 0.7mol/L aqueous solution, adjusted to pH=7 with ammonia water, ultrasonic spray drying was carried out under stirring, and then calcined at 500℃ for 4h to obtain Nano powder. Weigh 689g of this nano-powder and add it to the coarse-grained powder. Add deionized water while stirring. The added amount of water accounts for 25wt% of the mixed powder (ie, the above-mentioned nanopowder + coarse-grained powder). Press the mud in a filter press molding mold, press and hold the pressure for 2min, make a cylinder of φ52mm, 16mm in height, bake at 100°C for 1h, then put it into a cold isostatic press at 250Mpa for 2min . Then heat up from room temperature to 1000°C at a rate of 10°C/min in a microwave oven, keep the temperature for 30 minutes, then cool down to 500°C at 2°C/min, and then naturally cool to room temperature to obtain a ceramic block; use a slicer to cut the ceramic body A wafer with a diameter of 52mm and a thickness of 0.4mm is formed; silver is printed on the wafer, and then heat-treated after firing at 800°C: that is, the prepared sheet is heated to 750°C at a heating rate of 5°C/min, and based on this It is kept for 20 hours, and then cooled to room temperature at a rate of 2°C/min. During the entire heat treatment process, argon gas is introduced as a protective atmosphere; then a dicing machine is used to cut into chips with a size of 0.7×0.7 mm.

[0053] Randomly select 60 thermistor chips obtained by this method, and measure their resistance at 25℃. Compared with the thermistor chips prepared by the traditional method, the resistance of the chip made by the new process is within 10KΩ±1% The pass rate is 85.9%, while the pass rate within ±1% of the traditional method is 55.1%, that is, the resistance pass rate has been greatly improved. Divide the 60 chips into two parts. After soldering and packaging, one half is aged in an oven at 150℃ for 100h, and the other half is subjected to thermal shock 1000 times in a -30~100℃ tank, and the resistance changes before and after the test are measured. The rates of change were 0.56% and 0.42%, while the values ​​of the traditional method were 0.86% and 1.36%. It can be seen that the use of the new technology can greatly improve the resistance accuracy and reliability of the thermistor chip.

[0054] In this embodiment, the thermistor chip prepared according to the traditional method for comparison is prepared as follows:

[0055] 1) Use an analytical balance to accurately weigh 558.40g of trimanganese tetroxide, 212.40g of nickel oxide, 723.98g of ferric oxide, and 725.44g of cobalt oxide. Ball mill and mix the above mixture for 20h, dry, crush and calcinate at 850℃ for 2h, Then ball mill again for 20 hours to obtain coarse particle powder (the particle size of the powder is 1-5μm);

[0056] 2) Put the above powder at 40Kg/cm 2 Perform briquetting at a pressure of 10min, and perform cold isostatic pressing on the formed bulk material, hold the pressure at 400MPa for 10min, and then sinter at a high temperature of 1250℃ for 3h;

[0057] 3) Use a slicer to cut the sintered ceramic body into discs with a thickness of 0.4mm and a diameter of 52mm; print silver on the discs, and age the resulting thermistor disc materials at a temperature of 110°C for 1000h.

[0058] figure 2 It is a TEM image of the nano powder prepared in this example.

[0059] Example 3:

[0060] Using an analytical balance, accurately weigh 420.2g of trimanganese tetroxide, 487.04g of cobalt oxide, 499.30g of ferric oxide, and 40.40g of aluminum oxide. The above mixture was ball milled and mixed for 20h, dried, crushed and calcined at 1000℃ for 2h, and then again Ball mill for 20h to obtain traditional coarse-grained powder (the particle size of the powder is 1-5μm). According to the same molar ratio of metal ions, cobalt nitrate, manganese nitrate, iron nitrate and aluminum nitrate were prepared into a 0.7mol/L aqueous solution, adjusted to pH=7 with ammonia water, ultrasonic spray drying was carried out under stirring, and calcined at 500℃ for 4h to obtain Nano composite powder. Weigh 506.2g of this nano-powder and add it to the coarse-grained powder. Add deionized water while stirring. The added amount of water accounts for 25wt% of the mixed powder (ie the above-mentioned nano-powder + coarse-grained powder) . Press the mud in a filter press forming mold, press and hold the pressure for 2min, make a cylinder of φ52mm, 16mm in height, bake at 100℃ for 1h, then put it into a cold isostatic press for 320Mpa for 2min . Then heat up from room temperature to 1000°C at a rate of 10°C/min in a microwave oven, keep the temperature for 30 minutes, then cool down to 500°C at 2°C/min, and then naturally cool to room temperature to obtain a ceramic block; use a slicer to cut the ceramic body A wafer with a thickness of 0.25mm and a diameter of 52mm is formed; silver is printed on the wafer, and then heat-treated after being burnt at 800°C: that is, the prepared sheet is heated to 750°C at a heating rate of 5°C/min, and then Basically, it is kept for 20 hours, and then cooled to room temperature at a rate of 2°C/min. During the entire heat treatment process, helium gas is introduced as a protective atmosphere; then a dicing machine is used to cut into a chip with a size of 0.7×0.7mm.

[0061] Randomly select 60 thermistor chips obtained by this method, and measure their resistance at 25℃. Compared with the thermistor chips prepared by the traditional method, the resistance of the chip made by the new process is within 50KΩ±1% The pass rate is 93.2%, and the pass rate within ±1% of the traditional method is 76.1%, that is, the pass rate of resistance has been greatly improved. Divide the 60 chips into two parts. After soldering and packaging, one half is aged in an oven at 110°C for 1000 hours, and the other half is subjected to thermal shock 1000 times in a tank at -30~100°C, and the resistance changes before and after the test are measured. The rate of change is 0.316% and 0.352%, while the traditional method is 0.86% and 0.93%. It can be seen that the use of the new technology can greatly improve the resistance accuracy and reliability of the thermistor chip.

[0062] In this embodiment, the thermistor chip prepared according to the traditional method for comparison is prepared as follows:

[0063] 1) Use an analytical balance to accurately weigh 567.27 g of trimanganese tetroxide, 657.50g of nickel oxide, 674.06g of ferric oxide, and 54.54g of aluminum oxide. Ball mill and mix the above mixture for 20h. After drying, crush and calcinate at 1000℃ for 2h. Then ball mill again for 20 hours to obtain coarse particle powder (the particle size of the powder is 1-5μm);

[0064] 2) Put the above powder at 40Kg/cm 2 Perform briquetting at a pressure of 10min, and perform cold isostatic pressing on the formed bulk material, hold the pressure at 400MPa for 10min, and then sinter at a high temperature of 1250℃ for 3h;

[0065] 3) Use a slicer to cut the sintered ceramic body into discs with a thickness of 0.25mm and a diameter of 52mm; print silver on the discs, and age the resulting thermistor disc material at 110°C for 1000h.

[0066] image 3 It is a TEM image of the nano powder prepared in this example.