High-stability pressure-resistant NTC thermistor and preparation method thereof

Abstract

The application relates to the field of thermistors, in particular to a high-stability voltage-resistant NTC thermistor and a preparation method thereof. The high-stability voltage-resistant NTC thermistor comprises a porcelain sheet as a base body and electrode paste covering double surfaces of the porcelain sheet; raw materials of the porcelain sheet comprise, in mass parts, 55-70 parts of Mn3O4, 15-25 parts of NiO, 10-14 parts of CuO, 5-10 parts of SiO2, 1-3 parts of Al2O3, 0.5-2 parts of ZnO and 0.5-1 part of Nd2O3. The prepared NTC thermistor has good resistivity and B value, excellent aging resistance and stability, good voltage resistance and very excellent market prospect, and solves the key technical problems of the existing NTC thermistor.

Description

TECHNICAL FIELD

[0001] The application relates to the field of thermistors, in particular to a high-stability voltage-resistant NTC thermistor and a preparation method thereof. BACKGROUND

[0002] Thermistors are a kind of sensitive elements, and are divided into PTC (Positive Temperature Coefficient) thermistors and NTC (Negative Temperature Coefficient) thermistors according to different temperature coefficients. The typical feature of thermistors is temperature sensitivity, and different temperatures show different resistance values. The resistance value of a PTC thermistor is larger when the temperature is higher, and the resistance value of an NTC thermistor is smaller when the temperature is higher. They both belong to semiconductor devices.

[0003] The NTC thermistor is prepared by covering one or more layers of electrode paste on a porcelain body, and has the advantages of large temperature sensitivity coefficient, small volume and short response time, and is currently widely applied in the fields of electronic equipment, automobile accessories, transportation, medical equipment, household appliances, power equipment, testing instruments and the like.

[0004] However, the NTC thermistor in the prior art has the technical problems of high resistivity, unstable B value, poor self-stability and poor aging resistance. In order to solve the problem, the application provides a high-stability voltage-resistant NTC thermistor and a preparation method thereof. The NTC thermistor prepared by the application has excellent aging resistance and stability under the premise of good resistivity and B value, has good voltage resistance performance, has very excellent market prospect, and solves the key technical problems of the existing NTC thermistor. SUMMARY

[0005] In order to solve the above problems, the application provides a high-stability voltage-resistant NTC thermistor in the first aspect, which comprises a porcelain sheet as a base body and electrode paste covering the double surfaces of the porcelain sheet.

[0006] As a preferred scheme, the raw materials of the porcelain sheet comprise, in mass parts, 55-70 parts of Mn3O4, 15-25 parts of NiO, 10-14 parts of CuO, 5-10 parts of SiO2, 1-3 parts of Al2O3, 0.5-2 parts of ZnO and 0.5-1 part of Nd2O3.

[0007] As a preferred scheme, the mass ratio of Mn3O4, NiO, CuO, ZnO and Nd2O3 is (60-65):(20-24):(12-13):(1-1.5):0.8.

[0008] As a preferred solution, the mass ratio of the Mn3O4, NiO, CuO, ZnO and Nd2O3 is (62-64):(22-23):12:1.2:0.8.

[0009] As a preferred solution, the preparation method of the ceramic sheet comprises the following steps: S1: uniformly mixing Mn3O4, NiO, CuO, SiO2, Al2O3, ZnO and Nd2O3, and adding them into a wet ball mill for ball milling to obtain ceramic powder; S2: mixing the ceramic powder after ball milling with a binder to obtain ceramic particles; S3: after the ceramic particles are dry-pressed into a sheet, pre-sintering is performed at 800-900°C for 2-3h, and then sintering is continued at 1100-1200°C for 4-5h, and the ceramic sheet is obtained after completion.

[0010] As a preferred solution, the D50 of the ceramic powder in S1 is 2.5-8μm. 50 As a preferred solution, the D50 of the ceramic powder in S1 is 5-6.5μm.

[0011] As a preferred solution, the D50 of the ceramic powder in S1 is 2.5-8μm. 50 As a preferred solution, the D50 of the ceramic powder in S1 is 5-6.5μm.

[0012] As a preferred solution, the binder is polyvinyl acetate.

[0013] As a preferred solution, the mass ratio of the ceramic powder and the binder is (80-100):(1-10).

[0014] As a preferred solution, the mass ratio of the ceramic powder and the binder is (90-100):(5-8).

[0015] As a preferred solution, the electrode paste comprises, in mass parts, 60-80 parts of silver micro-powder, 5-10 parts of glass powder, 1-5 parts of oxide, 10-25 parts of organic resin, 3-5 parts of auxiliary agent, and 40-55 parts of solvent.

[0016] As a preferred solution, the specific surface area of the silver micro-powder is 2-8m 2 / g.

[0017] As a preferred solution, the specific surface area of the silver micro-powder is 4-5m 2 / g.

[0018] As a preferred solution, the mass ratio of the silver micro-powder, the glass powder and the organic resin is (60-75):(7-9):(15-20).

[0019] As a preferred solution, the mass ratio of the silver micro-powder, the glass powder and the organic resin is (65-70):8:(18-20).

[0020] As a preferred aspect, the oxide is at least one of Bi2O3, ZnO, Ni2O3, CuO, and CoO.

[0021] As a preferred aspect, the oxide is Bi2O3and CuO.

[0022] As a preferred aspect, the mass ratio of Bi2O3and CuO is (3-4) : 1.

[0023] As a preferred aspect, the organic resin is a combination of acetyl cellulose and polyvinylpyrrolidone.

[0024] As a preferred aspect, the mass ratio of acetyl cellulose and polyvinylpyrrolidone is (4-5) : (2-2.5).

[0025] As a preferred aspect, the mass ratio of acetyl cellulose and polyvinylpyrrolidone is (4.2-4.5) : 2.

[0026] As a preferred aspect, the auxiliary agent is at least one of phosphoric acid ester and aryl phenol polyoxyethylene ether.

[0027] As a preferred aspect, the auxiliary agent is phosphoric acid ester.

[0028] As a preferred aspect, the phosphoric acid ester is at least one of NP phosphoric acid ester, 600 phosphoric acid ester, and TSP phosphoric acid ester.

[0029] As a preferred aspect, the phosphoric acid ester is NP phosphoric acid ester.

[0030] As a preferred aspect, the solvent is at least one of diethylene glycol butyl ether, benzyl alcohol, dimethyl carbonate, terpineol, and castor oil.

[0031] As a preferred aspect, the solvent is diethylene glycol butyl ether.

[0032] The application can form a stable and excellent dispersion carrier flow system in the silver electrode paste by using the above-mentioned selection of specific organic resins and the collocation of auxiliary agents and organic solvents. The specific selection of organic resins can not only provide the required consistency for constructing the carrier flow system in the system, but also further form good silver powder agglomeration sites by the organic resins. The sites can be well separated by the interaction of the auxiliary agents and the solvents, thereby avoiding excessive agglomeration. In the use process of the electrode paste, the silver powder can be better printed and dispersed on the substrate ceramic sheet, and a good connection effect is formed. The existence of the connection effect can ensure the connection strength and stability of the electrode layer and the ceramic sheet in the sintering process. Because of the existence of the barrier film, the exposure degree of the silver powder particles on the surface of the electrode paste can be greatly reduced, thereby ensuring that the surface has more resin components, so that a more uniform and smooth electrode surface is obtained in the process of forming a fixed surface, thereby having good voltage resistance.

[0033] As a preferred scheme, the glass powder, in terms of mass parts, comprises: 30-45 parts of Bi2O3, 20-25 parts of SiO2, 15-20 parts of Na2O, 1-5 parts of CaO, and 1-3 parts of Al2O3.

[0034] As a preferred scheme, the mass ratio of Bi2O3, SiO2, Na2O, CaO and Al2O3 is (33-42):(22-24):(16-20):(2-4):(2-3).

[0035] As a preferred scheme, the mass ratio of Bi2O3, SiO2, CuO, CaO and B2O3 is 40:23:(17-19):3.5:2.5.

[0036] As a preferred scheme, the preparation method of the glass powder comprises the following steps: S1: heating to 800-900 DEG C, adding the required raw materials of the glass powder for smelting to obtain a glass solution; S2: rapidly cooling the glass solution in 0-5 DEG C cold water to obtain glass particles, grinding and ball milling the glass particles, and then drying and passing through a 300-mesh sieve to obtain the glass powder.

[0037] As a preferred scheme, the preparation method of the electrode paste comprises the following steps: mixing the required raw materials of the electrode paste, mixing and stirring at a speed of 200-300 r / min, ultrasonic treatment at a power of 400-600 W for 3-4 h after stirring is completed, and then obtaining the electrode paste.

[0038] The second aspect of the present application provides a preparation method of the high-stability voltage-resistant NTC thermistor, which comprises the following steps: flattening the prepared ceramic sheet, then printing electrode paste on both sides of the ceramic sheet, high-temperature sintering, and obtaining the high-stability voltage-resistant NTC thermistor after the thickness of the electrode after sintering is 4-6 mu m.

[0039] As a preferred solution, the sintering temperature of the high-temperature sintering is 750-800 DEG C.

[0040] The present application has the following beneficial effects:

[0041] 1. The high-stability voltage-resistant NTC thermistor provided by the present application has excellent aging resistance, stability, voltage resistance and market prospect under the premise of good resistivity and B value, and solves the key technical problems of the existing NTC thermistor.

[0042] 2. The high-stability voltage-resistant NTC thermistor provided by the present application can form a stable and excellent dispersion carrier flow system in the silver electrode paste through the selection of specific organic resins and the matching of auxiliary agents and organic solvents; the specific selection of the organic resins can not only provide the required consistency for constructing the carrier flow system, but also further form good silver powder agglomeration sites through the organic resins, and the sites can be well separated by the interaction of the auxiliary agents and the solvents, thereby avoiding excessive agglomeration and better printing and dispersion in the base ceramic sheet during the use of the electrode paste, and forming a good connection effect; the existence of the connection effect can ensure the connection strength and stability of the electrode layer and the ceramic sheet during the sintering process, and because of the existence of the separation film, the exposure degree of the silver powder particles on the surface of the electrode paste can be greatly reduced, thereby ensuring that the surface has more resin components, so that a more uniform and smooth electrode surface is obtained during the formation of the fixed surface.

[0043] 3. The high-stability voltage-resistant NTC thermistor provided by the present application has a simple preparation method, simple equipment operation, simple raw materials, and can effectively reduce the raw material cost of the existing NTC resistor, does not involve complex chemical reactions, and can effectively reduce the equipment maintenance and labor cost in large-scale production in the later period, and has very excellent market prospect. DETAILED DESCRIPTION

[0044] The technical solutions in the above summary of the application will be further described and demonstrated in the following specific embodiments. The following examples are only actual examples for illustrating and explaining the content of the technical solutions in the specification, and should not limit the scope of the claims of the present application. Any technical product based on the technical solutions described in the summary of the application should be covered in the scope of the present application.

[0045] In the following examples, the raw materials are commercially available products or can be prepared by methods well known to those skilled in the art, unless otherwise specified.

[0046] Example 1

[0047] The first aspect of the example 1 provides a high-stability pressure-resistant NTC thermistor, which comprises a ceramic sheet as a substrate, and electrode paste covering both surfaces of the ceramic sheet.

[0048] The raw materials of the ceramic sheet, in terms of mass parts, include 64 parts of Mn304, 22 parts of NiO, 12 parts of CuO, 6 parts of Si02, 2 parts of Al203, 1.2 parts of ZnO, and 0.8 parts of Nd203.

[0049] The preparation method of the ceramic sheet comprises the following steps: S1: uniformly mixing Mn304, NiO, CuO, Si02, Al203, ZnO, and Nd203, and adding them into a wet ball mill for ball milling to obtain ceramic powder; S2: mixing the ceramic powder after ball milling with a binder to obtain ceramic particles; S3: after the ceramic particles are dry-pressed into a sheet, pre-sintering is performed at 850°C for 2.5h, and then sintering is continued at 1200°C for 4.5h, and the ceramic sheet is obtained after completion.

[0050] The D 50 The particle size is 6μm.

[0051] The binder is polyvinyl acetate, which is purchased from the high-quality polyvinyl acetate product sold by Wuhan Kangqiong Biomedicine Co., Ltd.

[0052] The mass ratio of the ceramic powder and the binder is 92:8.

[0053] The raw materials of the electrode paste, in terms of mass parts, include 68 parts of silver powder, 8 parts of glass powder, 4 parts of oxide, 18 parts of organic resin, 4 parts of auxiliary agent, and 50 parts of solvent.

[0054] The specific surface area of the silver powder is 5m 2 / g, which is purchased from the corresponding silver powder product sold by Huizhou Tenghui Technology Co., Ltd.

[0055] The oxide is Bi203and CuO, and the mass ratio of the two is 3:1.

[0056] The organic resin is a combination of acetyl cellulose and polyvinyl pyrrolidone, and the mass ratio of the two is 4.4:2. The acetyl cellulose is purchased from the acetyl citric acid tributyl cellulose resin product sold by Wuhan Kanos Technology Co., Ltd.; the polyvinyl pyrrolidone is polyvinyl pyrrolidone K90.

[0057] The adjuvant is NP phosphate; the solvent is diethylene glycol butyl ether.

[0058] The raw materials for the glass powder include, in parts by mass, 40 parts of Bi2O3, 23 parts of SiO2, 18 parts of Na2O, 3.5 parts of CaO, and 2.5 parts of Al2O3.

[0059] The method for preparing the glass powder includes the following steps: S1: heating to 900 ℃ and adding raw materials required for the glass powder to perform melting, to obtain a glass solution; S2: placing the glass solution into 5 ℃ cold water to rapidly cool to obtain glass particles, and performing ball milling on the glass particles, followed by drying and passing through a 300-mesh sieve, to obtain the glass powder.

[0060] The method for preparing the electrode paste includes the following steps: mixing raw materials required for the electrode paste, mixing and stirring at a rotation speed of 200 r / min, and performing ultrasonic treatment at a power of 500 W for 4 h after completion of the stirring, to obtain the electrode paste.

[0061] The second aspect of the embodiment provides a method for preparing the high-stability voltage-resistant NTC thermistor, and the method includes the following steps: flattening the prepared ceramic sheet, then printing the electrode paste on both surfaces of the ceramic sheet, and performing high-temperature sintering at 800 ℃, so that the thickness of the electrode after sintering is 5 μm, and the high-stability voltage-resistant NTC thermistor is obtained after completion.

[0062] Embodiment 2

[0063] The first aspect of the embodiment 2 provides a high-stability voltage-resistant NTC thermistor, which includes a ceramic sheet as a substrate, and an electrode paste covering both surfaces of the ceramic sheet.

[0064] The raw materials for the ceramic sheet include, in parts by mass, 60 parts of Mn3O4, 20 parts of NiO, 13 parts of CuO, 6 parts of SiO2, 2 parts of Al2O3, 1.5 parts of ZnO, and 0.8 parts of Nd2O3.

[0065] The method for preparing the ceramic sheet includes the following steps: S1: uniformly mixing Mn3O4, NiO, CuO, SiO2, Al2O3, ZnO, and Nd2O3, and adding the mixture into a wet ball mill to perform ball milling, to obtain ceramic powder; S2: mixing the ceramic powder after the ball milling with a binder to obtain ceramic particles; and S3: drying and pressing the ceramic particles into a sheet, then performing pre-sintering at 850 ℃ for 2.5 h, and then continuing to perform sintering at 1200 ℃ for 4.5 h, to obtain the ceramic sheet.

[0066] The D 50 The particle size is 6 μm.

[0067] The binder is polyvinyl acetate, which is purchased from the high-quality polyvinyl acetate product sold by Wuhan Kangqiong Biomedicine Co., Ltd.

[0068] The mass ratio of the ceramic powder and the adhesive is 92:8.

[0069] The electrode paste includes, in mass parts, 68 parts of silver micropowder, 8 parts of glass powder, 4 parts of oxide, 18 parts of organic resin, 4 parts of auxiliary agent, and 50 parts of solvent.

[0070] The specific surface area of the silver micropowder is 5 m 2 / g, which is purchased from a corresponding silver micropowder product sold by Huizhou Tenghui Technology Co., Ltd.

[0071] The oxide is Bi2O3 and CuO, and the mass ratio of the two is 3:1.

[0072] The organic resin is a combination of acetyl cellulose and polyvinyl pyrrolidone, and the mass ratio of the two is 4.4:2. The acetyl cellulose is purchased from an acetyl citric acid tributyl ester cellulose resin product sold by Wuhan Kanos Technology Co., Ltd.; and the polyvinyl pyrrolidone is polyvinyl pyrrolidone K90.

[0073] The auxiliary agent is NP phosphate; and the solvent is diethylene glycol butyl ether.

[0074] The glass powder includes, in mass parts, 35 parts of Bi2O3, 22 parts of SiO2, 16 parts of Na2O, 2 parts of CaO, and 2 parts of Al2O3.

[0075] The preparation method of the glass powder includes the following steps: S1: heating to 900℃ and adding raw materials required for the glass powder to perform melting, to obtain a glass solution; S2: placing the glass solution into 5℃ cold water to rapidly cool to obtain glass particles, and performing ball milling on the glass particles, and then drying and passing through a 300-mesh sieve, to obtain the glass powder.

[0076] The preparation method of the electrode paste includes the following steps: mixing raw materials required for the electrode paste, and performing mixing and stirring at a rotation speed of 200 r / min, and after completion of the stirring, performing ultrasonic treatment at a power of 500 W for 4 h, and after completion, obtaining the electrode paste.

[0077] The second aspect of the embodiment provides a preparation method of the high-stability pressure-resistant NTC thermistor, and the preparation method includes the following steps: flattening the prepared ceramic sheet, then printing the electrode paste on both sides of the ceramic sheet, and performing high-temperature sintering at 800℃, and the thickness of the electrode after sintering is 5 μm, and after completion, obtaining the high-stability pressure-resistant NTC thermistor.

[0078] Comparative Example 1

[0079] The specific implementation of the comparative example is basically the same as that of Embodiment 1, and the only difference is that the raw materials of the ceramic sheet include, in mass parts, 80 parts of Mn3O4, 20 parts of NiO, 13 parts of CuO, 6 parts of SiO2, and 2 parts of Al2O3.

[0080] Comparative Example 2

[0081] The specific embodiment of the present comparative example is basically the same as that of Example 1, except that the electrode paste is prepared from raw materials including, in parts by mass, 60 parts of silver micropowder, 20 parts of glass powder, 1 part of oxide, 10 parts of organic resin, 2 parts of auxiliary agent, and 65 parts of solvent.

[0082] Comparative Example 3

[0083] The specific embodiment of the present comparative example is basically the same as that of Example 1, except that the glass powder is prepared from raw materials including, in parts by mass, 55 parts of Bi2O3, 22 parts of SiO2, 10 parts of CuO, and 1 part of CaO.

[0084] Comparative Example 4

[0085] The specific embodiment of the present comparative example is basically the same as that of Example 1, except that the organic resin is a combination of acetyl cellulose and polyvinylpyrrolidone at a mass ratio of 1.2:3.

[0086] Comparative Example 5

[0087] The specific embodiment of the present comparative example is basically the same as that of Example 1, except that the ceramic powder in S1 has a D 50 The particle size is 2.5 μm.

[0088] Performance Evaluation

[0089] 1. Resistivity and B value: The NTC thermistors prepared in Examples and Comparative Examples are placed in a 25°C thermostat for resistance testing, and after measuring the resistance at 25°C, they are placed in a 90°C thermostat for high-temperature resistance testing. The resistivity of the NTC thermistors is calculated from the two resistance values, and the measured results are averaged over 10 tests and recorded in Table 1.

[0090] 2. Aging resistance: The NTC thermistors prepared in Examples and Comparative Examples are aged at 125°C in 75% humidity air for 1000 hours, and their resistivity is again tested by the method of Performance Evaluation 1. The increase in resistivity relative to the corresponding resistivity in Performance Evaluation 1 is calculated, and the measured results are averaged over 10 tests and recorded in Table 1.

[0091] Table 1 Performance Evaluation Test

[0092] Example Resistivity (Ω·□mm) Rate of change of resistivity (%) Example 1 60.4 0.228 Example 2 61.1 0.241 Comparative Example 1 64.2 0.279 Comparative Example 2 63.3 0.289 Comparative Example 3 62.9 0.288 Comparative Example 4 64.1 0.281 Comparative Example 5 64.7 0.290

[0093] From the data results of the examples and comparative examples of the present application and Table 1, it can be seen that Examples 1 and 2 can achieve excellent results in terms of resistivity and aging resistance / stability, etc. by using the essential technical solutions defined in the present application, which is mainly because the specific ceramic chip and electrode paste raw material scheme in the present application enhances the bonding strength of the electrode raw material and the ceramic chip and the dispersion uniformity thereof. Comparative Examples 1-5 are significantly inferior to Examples 1-3 in the corresponding performance tests because they do not use the essential technical solutions, which further proves the importance of the technical solutions defined in the present application for its technical effects.

Claims

1. A high-stability voltage-resistant NTC thermistor, characterized by: The high-stability voltage-resistant NTC thermistor comprises a ceramic sheet as a base body and electrode paste covering both surfaces of the ceramic sheet; The raw materials of the ceramic sheet, in mass parts, consist of 55-70 parts of Mn3O4, 15-25 parts of NiO, 10-14 parts of CuO, 5-10 parts of SiO2, 1-3 parts of Al2O3, 0.5-2 parts of ZnO and 0.5-1 part of Nd2O3; The mass ratio of the Mn3O4, NiO, CuO, ZnO and Nd2O3 is (60-65):(20-24):(12-13):(1-1.5):0.8; The preparation method of the ceramic sheet comprises the following steps: S1: uniformly mixing Mn3O4, NiO, CuO, SiO2, Al2O3, ZnO and Nd2O3, and ball milling in a wet ball mill to obtain ceramic powder; S2: mixing the ceramic powder after ball milling with a binder to obtain ceramic particles; S3: dry pressing the ceramic particles into a sheet, pre-sintering at 800-900 DEG C for 2-3 hours, then continuing sintering at 1100-1200 DEG C for 4-5 hours, and obtaining the ceramic sheet after completion; The D50 of the ceramic powder in S1 50 The particle size is 6-8 μm. The binder is polyvinyl acetate; The mass ratio of the ceramic powder and the binder is (80-100):(1-10); The raw materials of the electrode paste, in mass parts, consist of 60-80 parts of silver micro powder, 5-10 parts of glass powder, 4-5 parts of oxide, 10-25 parts of organic resin, 3-5 parts of additive and 40-55 parts of solvent; The oxide is Bi2O3 and CuO; the mass ratio of the Bi2O3 and CuO is (3-4):1; The organic resin is a combination of acetyl cellulose and polyvinyl pyrrolidone; the mass ratio of the acetyl cellulose and polyvinyl pyrrolidone is (4-5):(2-2.5); The raw materials of the glass powder, in mass parts, consist of 30-45 parts of Bi2O3, 20-25 parts of SiO2, 15-20 parts of Na2O, 1-5 parts of CaO and 1-3 parts of Al2O3.

2. The high-stability voltage-resistant NTC thermistor according to claim 1, characterized in that: The specific surface area of the silver micropowder is 2-8 m 2 / g.

3. The high-stability voltage-resistant NTC thermistor according to claim 2, characterized in that: The mass ratio of the silver micro powder, glass powder and organic resin is (60-75):(7-9):(15-20).

4. The high-stability voltage-resistant NTC thermistor according to claim 1, characterized in that: The additive is at least one of phosphate ester and aryl phenol polyoxyethylene ether.

5. The high-stability voltage-resistant NTC thermistor according to claim 4, characterized in that: The solvent is at least one of diethylene glycol butyl ether, benzyl alcohol, dimethyl carbonate, terpineol and castor oil.

6. A method for preparing a high-stability pressure-resistant NTC thermistor according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: flattening the prepared ceramic sheet, then printing the electrode paste on both surfaces of the ceramic sheet, high-temperature sintering, and obtaining the electrode with a thickness of 4-6 microns after sintering.