High resistivity low b-value thermosensitive material, chip resistor and preparation method thereof

Abstract

This application relates to the field of thermistor materials technology, specifically disclosing a high resistivity, low B-value thermistor material, a chip resistor, and a method for preparing the same. The high resistivity, low B-value thermistor material provided in this application comprises a base material and 2-10% by weight of additives; the base material comprises Mn3O4, Co3O4, SrO, ZnO, and TiO2 in a weight ratio of (10-40):(5-15):(20-60):(5-10):(1-15); the additives comprise CaO, Fe2O3, and SiC in a weight ratio of (5-20):(10-50):(9-35); this application also provides a chip resistor made using the above-mentioned thermistor material. The chip resistor obtained in this application has high resistivity and a low B-value, which can meet the requirements for use in negative temperature coefficient thermistors.

Description

Technical Field

[0001] This application relates to the field of thermistor materials technology, specifically to a high resistivity, low B-value thermistor material, a chip resistor, and a method for preparing the same. Background Technology

[0002] In fields such as automotive electronics and aerospace, it is often necessary to achieve temperature measurement in a wider range of -40℃ to 150℃. Currently, most of the thermistor materials in negative temperature coefficient thermistors are made of oxides of transition metals Mn, Fe, Co, Ni, and Cu in different proportions. Their resistivity ranges from a few ohm-cm to several thousand ohm-cm, and their material constant (B value) is 2000-6000K. The corresponding thermistor element resistance value is a few ohms to several megaohms.

[0003] However, according to oxide semiconductor theory, the B value of a material and the activation energy ΔE satisfy the relationship B = ΔE / (2K) (where K is the Boltzmann constant, 8.62 × 10⁻⁶). -5 The activation energy ΔE is related to the resistivity ρ, specifically ρ = (1 / (N0eu))e^(ΔE / (2KT)), which can be derived as ρ = (1 / (N0eu))e^(B / T). This theory indicates that high resistivity materials are necessarily accompanied by high B values, and the two are positively correlated, which has become a technical bias in this field. While existing low-B-value thermistors can provide a smooth resistance-temperature change curve and simplify circuit design, they struggle to simultaneously achieve high resistance values, are prone to self-heating effects, and affect temperature measurement accuracy.

[0004] Therefore, it is necessary to develop a thermistor that combines high resistivity and low B value, which is the key to solving the problem of wide-temperature-range temperature measurement. Summary of the Invention

[0005] To overcome the problem that existing thermistor materials cannot simultaneously satisfy both high resistivity and low B-value, this application provides a thermistor material with high resistivity and low B-value, a chip resistor, and a method for preparing the same.

[0006] In a first aspect, this application provides a high resistivity, low B-value thermistor material, employing the following technical solution: A high resistivity, low B-value thermistor material, comprising a base material and 2-10% by weight of additives; The base materials include Mn3O4, Co3O4, SrO, ZnO and TiO2 in a weight ratio of (10~40):(5~15):(20~60):(5~10):(1~15); The additives include CaO, Fe2O3 and SiC in a weight ratio of (5~20):(10~50):(9~35).

[0007] This application provides a high-resistivity, low-B-value thermistor material. Through the selection and proportioning of raw materials, it achieves a synergistic balance between high resistivity and low B-value, overcoming the limitation of traditional materials where these two qualities cannot be simultaneously achieved. This provides a high-performance core material for wide-temperature-range temperature measurement applications. Specifically: In the base materials of this application, Mn3O4 serves as the core component of the thermistor matrix, providing the material with basic thermistor response capability; Co3O4 optimizes the thermistor characteristics by regulating electron migration efficiency; the addition of SrO and TiO2 in a specific ratio synergistically suppresses the increase in B-value while improving matrix stability; ZnO further fine-tunes the resistivity and temperature response sensitivity. The additives selected are CaO, Fe2O3, and SiC in specific proportions. CaO optimizes the crystal structure, Fe2O3 regulates carrier concentration, and SiC improves resistivity stability. By combining these three components in a specific ratio and adding them to the base material at a concentration of 2-10%, a synergistic regulatory effect is achieved. This enhances the high resistivity characteristics of the material while avoiding the problem of a surge in the B value as resistivity increases, perfectly meeting the core requirement of wide-temperature-range temperature measurement. In summary, this application achieves a synergistic balance between high resistivity and low B value in thermistor materials through the selection and proportioning of raw materials. The chip resistors prepared using this material exhibit excellent accuracy and stability, meeting the requirements of resistive temperature sensors in fields such as automotive electronics and aerospace.

[0008] In one specific implementation, the weight ratio of Mn3O4, Co3O4, SrO, ZnO and TiO2 in the base materials can also be 10:15:60:5:15, 30:10:30:5:10, 40:5:42:10:7, 20:13:40:10:5, 20:13:50:10:5, 20:13:60:10:5, 40:5:30:10:3 or 40:5:20:10:1.

[0009] Optionally, in the base material, the weight ratio of SrO to TiO2 is (8~12):1.

[0010] In this application, SrO, as the main component of the matrix, provides a stable crystal structure, and its high weight percentage lays the foundation for the material's basic resistivity. TiO2, as a functional dopant, can influence the B-value by adjusting the material's activation energy. Experimental research in this application revealed that further controlling the ratio of the two components within the range of (8~12):1 achieves the optimal crystal doping effect. TiO2 can be uniformly embedded in the SrO-constructed lattice, avoiding both excessively high TiO2 content leading to lattice distortion (avoiding an abnormally high B-value) and insufficient TiO2 content preventing effective control of the activation energy (ensuring the B-value remains at a low level).

[0011] In some embodiments, the weight ratio of SrO to TiO2 can be (3-4):1, (3-6):1, (3-8):1, (3-10):1, (3-12):1, (4-6):1, (4-8):1, (4-10):1, (4-12):1, (6-8):1, (6-10):1, (6-12):1, (8-10):1, (8-12):1, or (10-12):1 In one specific implementation, the weight ratio of SrO to TiO2 can also be 4:1, 3:1, 6:1, 8:1, 10:1 or 12:1.

[0012] Optionally, the weight ratio of CaO, Fe2O3 and SiC in the additive is (10~15):(20~40):20.

[0013] Optionally, the amount of the additive added is 3-5% of the total amount of the base material.

[0014] Secondly, this application provides a chip resistor made of a high resistivity, low B-value thermistor material.

[0015] Thirdly, this application provides a method for preparing a chip resistor, comprising the following steps: premixing and primary ball milling, pre-calcination, secondary ball milling, granulation and pressing, and sintering; In the first and second ball milling steps, water, ethanol and grinding balls are added to the mixture for grinding; the weight ratio of the mixture, water, ethanol and grinding balls is 1:(0.3-0.8):(0.1-0.5):(1.3-1.5).

[0016] Optionally, the pre-firing temperature is 800-900℃ and the pre-firing time is 5-8h.

[0017] Optionally, the sintering process is as follows: heating to 450-550℃ at a rate of 0.3-0.5℃ / min and holding for 50-90min; then heating to 780-820℃ at a rate of 8-12℃ / min and holding for 50-90min; then heating to 1080-1150℃ at a rate of 5-8℃ / min and holding for 3-6h; finally cooling to 780-820℃ at a rate of 0.3-0.8℃ / min and then naturally cooling to room temperature in the furnace before removal.

[0018] Optionally, the amount of the binder added is 20-30% of the powder mass, and the binder is a polyvinyl alcohol solution and / or carboxymethyl cellulose.

[0019] Fourthly, this application provides a resistive temperature sensor, including a temperature-sensing element made of a chip resistor.

[0020] In summary, this application has the following beneficial effects: 1. This application uses Mn3O4, Co3O4, SrO, ZnO, and TiO2 in a weight ratio of (10~40):(5~15):(20~60):(5~10):(1~15) as base materials, and CaO, Fe2O3, and SiC in a weight ratio of (5~20):(10~50):(9~35) as additives, which can achieve a material constant B value as low as 1219-1359K and a room temperature resistivity ρ 25 With chip resistors ranging from 2.88 to 4.27 KΩ, these chip resistors provide high-performance core materials for wide-temperature-range temperature measurement scenarios and can be used to manufacture negative temperature coefficient thermistors, showing great application prospects.

[0021] 2. This application further controls the weight ratio of SrO and TiO2 in the base material to be in the range of (8~12):1, and the weight ratio of CaO, Fe2O3 and SiC in the additives to be in the range of (10~15):(20~40):20. The resulting chip resistor material constant B value can be as low as below 1300K and the room temperature resistivity ρ 25 It can reach 3.5 KΩ or higher. Detailed Implementation

[0022] This application provides a high resistivity, low B-value thermistor material, comprising a base material and 2-10% by weight of additives; the base material comprises Mn3O4, Co3O4, SrO, ZnO, and TiO2 in a weight ratio of (10-40):(5-15):(20-60):(5-10):(1-15); the additives comprise CaO, Fe2O3, and SiC in a weight ratio of (5-20):(10-50):(9-35). Further, in the base material, the weight ratio of SrO to TiO2 is (8-12):1; in the additives, the weight ratio of CaO, Fe2O3, and SiC is (10-15):(20-40):20; the amount of additives added is 3-5% of the total amount of the base material.

[0023] This application provides a chip resistor made using the above-mentioned high resistivity, low B-value thermistor material, the preparation method of which includes the following steps: (1) Premixing and primary ball milling: Add the mixture of base materials and additives into a ball mill jar, and add water, ethanol and grinding balls for primary ball milling. The grinding time is 7-10 hours, and then dry at 100-150℃.

[0024] (2) Pre-calcination: The ball-milled mixed powder is pre-calcined at 800-900℃ for 5-8 hours; (3) Secondary ball milling: Add water, ethanol and grinding balls to the pre-calcined mixture for secondary ball milling for 2-3 hours, and then dry at 100-150℃; (4) Granulation and tableting: Add 20-30% by weight of binder to the mixed powder after secondary ball milling, and manually form powder with a particle size of 80-150 mesh; then use a tableting machine to press the powder to a density of 2.5-3 g / cm³. 3 A blank sheet with a diameter of 54mm and a thickness of 100mm; (5) Sintering: Place the blanks in a ceramic bowl and sinter them in a box furnace. The sintering process is as follows: heat up to 450-550℃ at a rate of 0.3-0.5℃ / min and hold for 50-90min; then continue to heat up to 780-820℃ at a rate of 8-12℃ / min and hold for 50-90min; continue to heat up to 1080-1150℃ at a rate of 5-8℃ / min and hold for 3-6h; finally, cool down to 780-820℃ at a rate of 0.3-0.8℃ / min and then let it cool down naturally to room temperature before taking it out. (6) Post-processing: Silver paste electrodes are printed on both sides of the sintered chip using a 150-mesh screen, and then baked at 200-250℃ for 25-35 min and reduced at 820-850℃ for 20-30 min to obtain the chip resistance.

[0025] In steps (1) and (3), the weight ratio of the mixture, water, ethanol and grinding balls is 1:(0.3-0.8):(0.1-0.5):(1.3-1.5).

[0026] All raw materials, reagents, solvents, etc. used in this application are commercially available.

[0027] The present application will be further described in detail below with reference to embodiments and performance testing. Examples 1-8

[0028] Examples 1-8 each provide a chip resistor.

[0029] The difference in the above embodiments is that the weight ratio of each raw material in the base material is as shown in Table 1 below.

[0030] The chip resistor fabrication method provided in Examples 1-8 includes the following steps: (1) Premixing and primary ball milling: The mixture of base materials (as shown in Table 1 below) and additives was added to a ball mill jar, and water, ethanol and grinding balls were added for primary ball milling for 8 hours. Then it was dried at 120°C. The weight ratio of the mixture, water, ethanol and grinding balls was 1:0.5:0.3:1.5. The additives were CaO, Fe2O3 and SiC in a weight ratio of 15:30:20. The amount of additives added was 4% of the base materials. (2) Pre-calcination: The ball-milled mixed powder was pre-calcined at 850℃ for 6 hours; (3) Secondary ball milling: Water, ethanol and grinding balls are added to the pre-calcined mixture for secondary ball milling for 2 hours, and then dried at 120°C; the weight ratio of the mixture, water, ethanol and grinding balls is 1:0.5:0.3:1.5. (4) Granulation and tableting: Add 20% by weight of binder (10wt% polyvinyl alcohol solution) to the mixed powder after secondary ball milling, and manually form powder with a particle size of 80-150 mesh; then use a tableting machine to press the powder to a density of 2.8 g / cm³. 3 A blank sheet with a diameter of 54mm and a thickness of 100mm; (5) Sintering: Place the blank in a ceramic bowl and put it into a box furnace for sintering. The sintering process is as follows: heat up to 500℃ at a rate of 0.4℃ / min and hold for 60min; then continue to heat up to 800℃ at a rate of 10℃ / min and hold for 60min; continue to heat up to 1120℃ at a rate of 6℃ / min and hold for 4h; finally, cool down to 800℃ at a rate of 0.5℃ / min and then let it cool down naturally to room temperature before taking it out. (6) Post-processing: Silver paste electrodes are printed on both sides of the sintered chip using a 150-mesh screen, and then baked at 230℃ for 30 min and reduced at 840℃ for 25 min to obtain the chip resistance.

[0031] Table 1 shows the proportions of the base materials in the chip resistors provided in Examples 1-8. Examples 9-13

[0032] Examples 9-13 each provide a chip resistor.

[0033] The difference between the above embodiment and embodiment 5 is that the weight ratio of each raw material in the base material is as shown in Table 2 below.

[0034] Table 2. Weight ratio of each raw material in the additives of Examples 5 and 9-13 Comparative Example 1

[0035] Comparative Example 1 provides a chip resistor.

[0036] The difference between the above embodiment and embodiment 5 is that the base materials are Mn3O4, Co3O4, SrO, ZnO and TiO2 in a weight ratio of 50:13:10:20:20. Comparative Example 2

[0037] Comparative Example 2 provides a chip resistor.

[0038] The difference between the above embodiments and Embodiment 5 is that the base materials are Mn3O4, Co3O4, ZnO and TiO2 in a weight ratio of 70:13:10:5. Comparative Example 3

[0039] Comparative Example 3 provides a chip resistor.

[0040] The difference between the above embodiments and Embodiment 5 is that the base materials are Mn3O4, Co3O4, NiO, ZnO and TiO2 in a weight ratio of 20:13:50:10:5; Comparative Example 4

[0041] Comparative Example 4 provides a chip resistor.

[0042] The difference between the above embodiments and Embodiment 5 is that the additives are CaO, Fe2O3 and SiC in a weight ratio of 30:10:5. Comparative Example 5

[0043] Comparative Example 5 provides a chip resistor.

[0044] The difference between the above embodiment and embodiment 5 is that the additive is CaO and SiC in a weight ratio of 30:15. Comparative Example 6

[0045] Comparative Example 6 provides a chip resistor.

[0046] The difference between the above embodiment and embodiment 5 is that the additive is CaO and Fe2O3 in a weight ratio of 30:15. Comparative Example 7

[0047] Comparative Example 7 provides a chip resistor.

[0048] The difference between the above embodiments and Embodiment 5 lies in the method of fabricating the chip resistor, which is as follows: The method for fabricating the chip resistor provided in Comparative Example 7 includes the following steps: (1) Premixing and primary ball milling: The mixture of base materials and additives is added to a ball mill jar, and water and grinding balls are added for primary ball milling. The milling time is 8 hours, and then it is dried at 120°C. The weight ratio of the mixture, water and grinding balls is 1:0.8:1.5. (2) Granulation and tableting: Add 20% by weight of binder (10% polyvinyl alcohol solution) to the ball-milled mixed powder, and manually form powder with a particle size of 80-150 mesh; then use a tableting machine to press the powder to a density of 2.8 g / cm³. 3 A blank sheet with a diameter of 54mm and a thickness of 100mm; (3) Sintering: Place the blank in a ceramic bowl and put it into a box furnace for sintering. The sintering process is as follows: heat up to 500℃ at a rate of 0.4℃ / min and hold for 60min; then continue to heat up to 800℃ at a rate of 10℃ / min and hold for 60min; continue to heat up to 1120℃ at a rate of 6℃ / min and hold for 4h; finally, cool down to 800℃ at a rate of 0.5℃ / min and then let it cool down naturally to room temperature before taking it out. (4) Post-processing: Silver paste electrodes are printed on both sides of the sintered chip using a 150-mesh screen, and then baked at 230℃ for 30 min and reduced at 840℃ for 25 min to obtain the chip resistance. Performance testing experiment

[0049] Chip resistors were prepared according to Examples 1-13 and Comparative Examples 1-7, with 100 copies of each prepared in parallel. The material constant B value and resistivity were measured and the average value was taken. The results are shown in Table 3 below.

[0050] (1) B value: The chip resistor was placed in a high-precision oil bath at 25℃ and 85℃ to stabilize its resistance value, and then the thermistor index B value of the chip resistor was calculated; refer to GB / T 6663.1-2007; (2) Resistivity ρ 25 To stabilize the resistance value of the chip resistors, place them in a 25℃ high-precision oil bath, referring to GB / T1410-2006.

[0051] Table 3 Performance test results of chip resistors obtained in Examples 1-13 and Comparative Examples 1-7

[0052] According to the test results in Table 3, the B value of the chip resistor obtained in Examples 1-13 is 1219-1359K, and ρ 25 The resistance of the first chip was 2.88-4.27 KΩ; however, the proportions of the raw materials in the base material of Comparative Example 1 were poor, resulting in a chip resistance with a B value as high as 1865 KΩ and ρ. 25The resistance is only 2.17KΩ; in Comparative Example 2, the base material lacks SrO, resulting in a chip with a resistance (B) as high as 2310KΩ and a resistance (ρ). 25 The resistance is only 1.05KΩ; in Comparative Example 3, the base material was replaced with NiO, and the resulting chip resistance had a B value as high as 1982KΩ, ρ 25 The resistance was only 2.43KΩ; in Comparative Example 4, the ratio of raw materials in the additives was poor, resulting in a chip resistance with a B value as high as 1753KΩ and ρ. 25 The resistance was only 2.89 KΩ; in Comparative Example 5, the additive lacked Fe2O3, resulting in a chip resistance with a B value as high as 1897 KΩ and ρ. 25 The resistance is only 2.35KΩ; in Comparative Example 6, the additive lacks SiC, resulting in a chip resistance with a B value as high as 1921KΩ and ρ. 25 The resistance was only 2.28 KΩ; the preparation method of Comparative Example 7 lacked secondary ball milling and ethanol-assisted grinding, resulting in poor powder mixing uniformity and a chip resistance B value as high as 1678 KΩ, ρ 25 The resistance is only 3.02 kΩ. Therefore, this application demonstrates that by using Mn3O4, Co3O4, SrO, ZnO, and TiO2 in a weight ratio of (10~40):(5~15):(20~60):(5~10):(1~15) as base materials and CaO, Fe2O3, and SiC in a weight ratio of (5~20):(10~50):(9~35) as additives, it is possible to obtain a low material constant B value and a high room temperature resistivity ρ. 25 The chip resistor can be used to manufacture negative temperature coefficient thermistors, and has a promising application prospect.

[0053] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A high resistivity, low B-value thermistor material, characterized in that, This includes the base material and 2-10% of its weight in additives; The base materials include Mn3O4, Co3O4, SrO, ZnO and TiO2 in a weight ratio of (10~40):(5~15):(20~60):(5~10):(1~15); The additives include CaO, Fe2O3 and SiC in a weight ratio of (5~20):(10~50):(9~35).

2. The high resistivity, low B-value thermistor material according to claim 1, characterized in that, In the base material, the weight ratio of SrO to TiO2 is (8~12):

1.

3. The high resistivity, low B-value thermistor material according to claim 1, characterized in that, In the additive, the weight ratio of CaO, Fe2O3 and SiC is (10~15):(20~40):

20.

4. The high resistivity, low B-value thermistor material according to claim 1, characterized in that, The amount of the additive added is 3-5% of the total amount of the base material.

5. A chip resistor, characterized in that, It is prepared using the high resistivity, low B-value thermistor material as described in any one of claims 1-4.

6. The method for preparing a chip resistor as described in claim 5, characterized in that, Includes the following steps: Premixing and primary ball milling, pre-calcination, secondary ball milling, granulation and tableting, sintering; In the first and second ball milling steps, water, ethanol and grinding balls are added to the mixture for grinding; the weight ratio of the mixture, water, ethanol and grinding balls is 1:(0.3-0.8):(0.1-0.5):(1.3-1.5).

7. The method for preparing a chip resistor according to claim 6, characterized in that, The pre-firing temperature is 800-900℃, and the pre-firing time is 5-8 hours.

8. The method for preparing a chip resistor according to claim 6, characterized in that, The sintering process is as follows: the temperature is increased to 450-550℃ at a rate of 0.3-0.5℃ / min and held for 50-90 min; then the temperature is increased to 780-820℃ at a rate of 8-12℃ / min and held for 50-90 min; then the temperature is increased to 1080-1150℃ at a rate of 5-8℃ / min and held for 3-6 h; finally, the temperature is decreased to 780-820℃ at a rate of 0.3-0.8℃ / min and then allowed to cool naturally in the furnace to room temperature before being removed.

9. The method for preparing a chip resistor according to claim 6, characterized in that, The amount of binder added is 20-30% of the powder mass, and the binder is a polyvinyl alcohol solution and / or carboxymethyl cellulose.

10. A resistive temperature sensor, characterized in that, It includes a temperature-sensing element made of the chip resistor as described in claim 5.

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