Method for manufacturing high-precision NTC thermistor chip

Abstract

The invention discloses a method for manufacturing a high-precision NTC thermistor chip. The method comprises a step 1) of weighing corresponding metal oxides according to a chemical formula Mn3-x-y-zNixFeyCozQtO4, performing mixing ball-milling, low-temperature calcination, ball-milling crushing and high-temperature calcination, and obtaining thermal sensitive ceramic powder; a step 2) of performing ball-milling on the thermal sensitive ceramic powder, adding an organic binder, and performing drying, pelleting and sieving to obtain formed powder; a step 3) of performing dry pressing and isostatic pressing on the formed powder, and obtaining formed briquette; a step 4) of adding the formed briquette into an atmosphere furnace, performing sintering in the weak oxidizing atmosphere, and obtaining agglomerate; a step 5) of cutting the agglomerate into slices, coating the slices with silver or gold electrodes, performing heat treatment, cutting the slices into required sizes, and obtaining the high-precision NTC thermistor chip. The decomposition of FeMnNiO4 is restrained by controlling oxygen partial pressure in the sintering process, ingredient segregation is reduced by introducing low-temperature calcination before presintering, the production process is controlled easily, the chip resistance and B value pass rate are high, and the reliability is high.

Description

technical field [0001] The invention relates to a manufacturing method of a high-precision NTC thermistor chip. Background technique [0002] Negative temperature coefficient (NTC) thermistors refer to electronic ceramic materials whose resistance decreases with increasing temperature, and are widely used in temperature sensors to measure temperature. In recent years, with the rapid development of science and technology, people have higher and higher requirements for the temperature measurement accuracy and temperature control accuracy of NTC thermistor chips. Nickel element has the characteristics of reducing material resistivity and B value at the same time, and it is not easy to cause NTC thermistor aging like Cu element, so it can be conveniently added to the NTC thermistor formula as the main component to adjust the NTC thermal resistance. The resistivity and material constant B value of the varistor. However, due to the variable valence state of Ni, NiO will be decom...

AI Technical Summary

Problems solved by technology

Therefore, when the Ni content in the NTC thermistor formula system is relatively high, a more stringent sintering process is required, which results in a resistivity ρ of 2 to 25kΩ·cm, B 25 / 85 NTC thermistor chips with a temperature of 3200 ~ 3600K are difficult to obtain

[0003] At present, there are mainly the following methods for producing NTC thermistor chips that meet the above requirements: 1) Ingots are made by combining dry pressing and cold isostatic pressing. , to obtain the NTC thermistor chip, this method limits the addition of Ni element, the pass rate of 1% product resistance value of the chip is low, in order to ensure that the pass rate of 1% product resistance value after scribing can reach more than 80%, the Ni element Generally, the addition amount shall not exceed 10at%. When the addition amount of Ni element is relatively large, due to the significant difference in the composition and microstructure of the outer layer and the core of the ceramic, it is easy to cause the resistivity to change in the radial or longitudinal direction, resulting in product qualification rate. Low; 2) Wet forming is directly made into thin slices, and after sintering, electrodes are applied, seasoned, and diced to obtain NTC thermistor chips. This method has low production efficiency. In order to ensure the thickness uniformity of the thin slices, it may be necessary to increase the grinding process. further reduces efficiency

Both of the above two methods put forward relatively strict requirements on the sintering temperature, holding time and cooling speed in the sintering process. Even if the sintering process parameters change slightly, the target resistivity, B value and finished product qualification rate may not be obtained.

[0004] In addition, most of the process routes used in the existing methods are: mixing ball milling, pre-calcination, secondary ball milling, forming, sintering, and subsequent chip making. There will be certain composition segregation in the process of secondary ball milling, which will affect the subsequent resistance value and B value uniformity of the material system