Copper electrode slurry for annular strontium titanate piezoresistor and application of copper electrode slurry

Abstract

The invention relates to the technical field of electronic materials, and particularly discloses copper electrode paste for an annular strontium titanate varistor and application of the copper electrode paste, and the copper electrode paste for the annular strontium titanate varistor is prepared from the following components in percentage by mass: 82%-88% of copper conductive powder, 0.3%-0.5% of an inorganic glass binder, 11%-18% of an organic carrier and 0-0.3% of a dispersing agent. The copper electrode slurry for the annular strontium titanate piezoresistor can be stacked and sintered in nitrogen at 800-900 DEG C, the sintered copper electrode slurry is good in appearance and excellent in welding performance, the adhesive force between a copper layer and strontium titanate piezoresistor ceramic is high, ohmic contact is good, and the electrostatic capacity is high.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic materials, and particularly relates to a copper electrode paste for an annular strontium titanate varistor and its application. Background Art

[0002] The annular strontium titanate (SrTiO3) varistor is an electronic component based on strontium titanate material, which has unique non-linear volt-ampere characteristics, capacitance characteristics and annular structure, and is widely used in overvoltage protection, surge absorption and other occasions.

[0003] The annular strontium titanate varistor needs to be tinned by attaching a specific metal electrode on its surface, and is connected to the circuit through soldering to realize its electrical performance. At present, the vast majority of the electrode layers for annular strontium titanate varistor chips in the market are silver electrode layers. Silver is a precious metal, and its price has been high in recent years, highlighting the cost problem of annular strontium titanate varistors. In addition, the silver electrode process uses a bottom ohmic silver paste and a surface pure silver paste for matching printing, and finally sintered into a resistor. The two printing processes are relatively complex and the technical difficulty is high.

[0004] Compared with silver electrodes, copper electrodes have higher sintering requirements, but are low in cost, have good ohmic contact performance with the resistor ceramic body, are more solder-resistant, and have better performance. Therefore, mass production of copper electrodes will be the general trend.

[0005] In the patent with the application number 202110357141, after printing and sintering a copper electrode on the surface of the annular strontium titanate varistor ceramic body, tin plating is carried out. The tin plating process is friendly to the copper burning process and welding performance, but tin plating belongs to an additional process, with complex process and high technical difficulty.

[0006] The mass production of copper electrodes for annular strontium titanate varistors is mainly restricted by the following factors: First, at low temperature (<800°C) sintering, it is difficult for the copper layer to be dense, and the adhesion between the copper layer and the strontium titanate varistor substrate is difficult to meet the requirements; Second, at high temperature sintering (>900°C), the long-term stability of the commercially available nitrogen sintering furnace is difficult to meet the requirements; Third, at 800°C - 900°C sintering, due to the adhesion requirements, a certain proportion of glass powder needs to be added. As the addition amount of glass powder increases, chemical reactions or penetration phenomena are likely to occur at the interface between the copper layer and the substrate, and the ohmic contact deteriorates rapidly. Summary of the Invention

[0007] Based on this, the purpose of the present invention is to provide a copper electrode paste for an annular strontium titanate varistor and its application. The copper paste can be stacked and sintered in nitrogen at 800°C - 900°C. After sintering, it has good appearance, excellent welding performance, strong adhesion between the copper layer and the strontium titanate varistor ceramic, good ohmic contact and high static capacitance.

[0008] To achieve the above purpose, the present invention adopts the following technical solutions: The present invention first provides a copper electrode paste for a ring-shaped strontium titanate varistor, which is prepared from the following components by mass percentage: 82%-88% of copper conductive powder, 0.3%-0.5% of inorganic glass binder, 11%-18% of organic carrier, and 0-0.3% of dispersant.

[0009] As a further improvement of the above solution of the present invention, the inorganic glass binder is a combination of several of B2O3, Bi2O3, SiO2, ZnO, CaO, CuO, and Al2O3, and the particle size of each component is 500-1200 mesh.

[0010] As a further improvement of the above solution of the present invention, the mass percentage of each component in the inorganic glass binder is: 25%-35% of B2O3, 30%-40% of Bi2O3, 2%-5% of SiO2, 15%-25% of ZnO, 1%-10% of CaO, 16%-18% of CuO, and 4%-5% of Al2O3.

[0011] As a further improvement of the above solution of the present invention, the measured softening point of the inorganic glass binder is 600-650 °C.

[0012] As a further improvement of the above solution of the present invention, the organic carrier includes an organic solvent and a polymer thickener. The organic solvent is at least one of terpineol and fatty alcohol ester 12, and the polymer thickener is ethyl cellulose; the dispersant is at least one of dispersant ED116 and dispersant ED120.

[0013] As a further improvement of the above solution of the present invention, the particle size of the copper conductive powder is 1-2 μm.

[0014] The present invention also provides a method for preparing the copper electrode paste for a ring-shaped strontium titanate varistor as described above, which includes the following steps: stirring and mixing the copper conductive powder, inorganic glass binder, organic carrier, and dispersant in proportion to obtain a mixture, and grinding the mixture until a copper electrode paste for a ring-shaped strontium titanate varistor with a particle size ≤ 10 µm and uniform dispersion is obtained.

[0015] The present invention also provides an application of the copper electrode paste for a ring-shaped strontium titanate varistor as described above in preparing a metallization layer of a ring-shaped strontium titanate varistor.

[0016] As a further improvement of the above solution of the present invention, it includes the following steps: printing the copper electrode paste for a ring-shaped strontium titanate varistor on a ring-shaped strontium titanate varistor ceramic substrate by screen printing, drying, and then sintering in a mesh belt furnace under a nitrogen atmosphere.

[0017] As a further improvement of the above solution of the present invention, the oxygen content in the mesh belt furnace is 0 - 30 ppm; the sintering curve is to raise the temperature at a heating rate of 15 - 20 °C / min to 400 - 500 °C for degumming for 5 minutes, and then raise the temperature at a heating rate of 10 - 15 °C / min to 800 - 900 °C and keep it warm for 10 minutes.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The copper electrode paste for annular strontium titanate varistor provided by the present invention can greatly reduce the cost of metalization of annular strontium titanate varistor, has a wide firing range for copper electrodes, good firing appearance, excellent welding performance and adhesion, good ohmic contact, and high capacitance.

[0019] In the copper electrode paste for annular strontium titanate varistor provided by the present invention, the softening point of the inorganic glass binder is 600 - 650 °C, and the sintering range of the copper electrode is 800 - 900 °C. At 800 - 900 °C, the inorganic glass binder has been fully softened and has a relatively high viscosity, is not easy to penetrate the matrix, and can be better distributed between the copper electrode layer and the matrix. Description of the Drawings

[0020] Figure 1 is the high-temperature melting state diagram of inorganic glass binders with different formulations; Figure 2 is the effect diagram of the copper layer welding lead being pulled off; Figure 3 is the microscopic structure diagram of the copper layer at different sintering temperatures. Detailed Embodiments

[0021] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0023] Example 1 This embodiment provides a copper electrode slurry for an annular strontium titanate varistor, which includes the following raw materials by mass percentage: 82% copper conductive powder, 0.3% inorganic glass binder, 12.3% pine alcohol, 4.4% alcohol ester twelve, and 1% ethyl cellulose. Among them, the inorganic glass binder is prepared according to formula 1, and formula 1 includes the following raw materials by mass percentage: 29% B2O3, 30% Bi2O3, 4% SiO2, 15% ZnO, 2% CaO, 16% CuO, and 4% Al2O3.

[0024] The method for preparing the copper electrode slurry for the annular strontium titanate varistor of this embodiment comprises the following steps: S1. Preparation of inorganic glass binder: weigh each component in proportion and mix them mechanically, put them into a muffle furnace and heat them at 1100-1300°C until they are melted, keep them warm for 10 minutes, pour them into cold water for quenching, and then ball-mill them in an aqueous medium until the powder particle size is ≤10μm, and dry them at 120°C to obtain an inorganic glass binder, and the softening point is tested to be 600-650°C; S2. Preparation of an organic carrier: terpineol, alcohol ester twelve, ethyl cellulose are mixed in proportion, and then the mixed system is heated to 80-100 ° C and stirred to completely dissolve the ethyl cellulose to obtain an organic carrier; S3. Preparation of slurry: copper conductive powder, inorganic glass binder and organic carrier are mixed in proportion to obtain a mixture, and the mixture is ground on a three-roll grinder until a copper electrode slurry for annular strontium titanate varistor with a particle size of ≤10µm and uniform dispersion is obtained.

[0025] The appearance of the copper electrode slurry for the annular strontium titanate varistor prepared in this embodiment is: paste-like, bright red, uniform and fine, with a particle size of ≤10µm, a viscosity of 100-250Pa·s (25°C, 5rpm), and a sintering temperature of 800-900°C.

[0026] Example 2 The difference between this embodiment and embodiment 1 is that the copper electrode slurry for the annular strontium titanate varistor of this embodiment includes the following component raw materials in percentage by mass: 85% copper conductive powder, 0.4% inorganic glass binder, 10% pine alcohol, 3.7% alcohol ester twelve, 0.8% ethyl cellulose, and 0.1% dispersant ED116.

[0027] The appearance of the copper electrode slurry for the annular strontium titanate varistor prepared in this embodiment is: paste-like, bright red, uniform and fine, with a particle size of ≤10µm, a viscosity of 100-250Pa·s (25°C, 5rpm), and a sintering temperature of 800-900°C.

[0028] Example 3 The difference between this embodiment and Embodiment 1 lies in that: the copper electrode paste for the annular strontium titanate varistor in this embodiment comprises the following component raw materials by mass percentage: 88% of copper conductive powder, 0.5% of inorganic glass binder, 4% of terpineol, 6.6% of ethyl carbitol acetate, 0.6% of ethyl cellulose, and 0.3% of dispersant ED120.

[0029] The appearance of the copper electrode paste for the annular strontium titanate varistor prepared in this embodiment: paste-like, bright red, uniform and delicate, particle size ≤ 10 µm, viscosity: 100 - 250 Pa·s (25 °C, 5 rpm), firing temperature is 800 - 900 °C.

[0030] Embodiment 4 The difference between this embodiment and Embodiment 1 lies in that: the copper electrode paste for the annular strontium titanate varistor in this embodiment comprises the following component raw materials by mass percentage: 85% of copper conductive powder, 0.4% of inorganic glass binder, 10% of terpineol, 3.7% of ethyl carbitol acetate, 0.8% of ethyl cellulose, and 0.1% of dispersant ED120; among them, the inorganic glass binder is prepared according to Formula 2, and Formula 2 comprises the following component raw materials by mass percentage: 28% B2O3, 33% Bi2O3, 2% SiO2, 10% ZnO, 4% CaO, 18% CuO, 5% Al2O3, and the measured softening point of the inorganic glass binder is 600 - 650 °C.

[0031] The appearance of the copper electrode paste for the annular strontium titanate varistor prepared in this embodiment: paste-like, bright red, uniform and delicate, particle size ≤ 10 µm, viscosity: 100 - 250 Pa·s (25 °C, 5 rpm), firing temperature is 800 - 900 °C.

[0032] Comparative Example 1 The difference between this comparative example and Embodiment 1 lies in that: the copper electrode paste for the annular strontium titanate varistor in this comparative example comprises the following component raw materials by mass percentage: 85% of copper conductive powder, 0.2% of inorganic glass binder, 10% of terpineol, 3.9% of ethyl carbitol acetate, 0.8% of ethyl cellulose, and 0.1% of dispersant ED116.

[0033] Comparative Example 2 The difference between this comparative example and Embodiment 1 lies in that: the copper electrode paste for the annular strontium titanate varistor in this comparative example comprises the following component raw materials by mass percentage: 85% of copper conductive powder, 0.6% of inorganic glass binder, 10% of terpineol, 3.5% of ethyl carbitol acetate, 0.8% of ethyl cellulose, and 0.1% of dispersant ED116.

[0034] Comparative Example 3 The difference between this comparative example and Example 1 is as follows: The copper electrode paste for the annular strontium titanate varistor in this comparative example comprises component raw materials in the following mass percentages: 85% copper conductive powder, 0.5% inorganic glass binder, 10% terpineol, 3.6% ethyl carbitol acetate, 0.8% ethyl cellulose, 0.1% dispersant ED116; wherein, the inorganic glass binder is prepared according to Formula III, and Formula III comprises component raw materials in the following mass percentages: 28% B2O3, 35% Bi2O3, 2% SiO2, 10% ZnO, 4% CaO, 18% CuO, 3% Al2O3.

[0035] Comparative Example 4 The difference between this comparative example and Example 1 is as follows: The copper electrode paste for the annular strontium titanate varistor in this comparative example comprises component raw materials in the following mass percentages: 85% copper conductive powder, 1% inorganic glass binder, 10% terpineol, 3.1% ethyl carbitol acetate, 0.8% ethyl cellulose, 0.1% dispersant ED120; wherein, the inorganic glass binder is prepared according to Formula III, and Formula III comprises component raw materials in the following mass percentages: 28% B2O3, 35% Bi2O3, 2% SiO2, 10% ZnO, 4% CaO, 18% CuO, 3% Al2O3.

[0036] Comparative Example 5 The difference between this comparative example and Example 1 is as follows: The copper electrode paste for the annular strontium titanate varistor in this comparative example comprises component raw materials in the following mass percentages: 85% copper conductive powder, 2% inorganic glass binder, 9% terpineol, 3.2% ethyl carbitol acetate, 0.7% ethyl cellulose, 0.1% dispersant ED120; wherein, the inorganic glass binder is prepared according to Formula III, and Formula III comprises component raw materials in the following mass percentages: 28% B2O3, 35% Bi2O3, 2% SiO2, 10% ZnO, 4% CaO, 18% CuO, 3% Al2O3.

[0037] Comparative Example 6 The difference between this comparative example and Example 1 is as follows: The copper electrode paste for the annular strontium titanate varistor in this comparative example comprises component raw materials in the following mass percentages: 85% copper conductive powder, 0.5% inorganic glass binder, 10% terpineol, 3.6% ethyl carbitol acetate, 0.8% ethyl cellulose, 0.1% dispersant ED120; wherein, the inorganic glass binder is prepared according to Formula IV, and Formula IV comprises component raw materials in the following mass percentages: 31% B2O3, 30% Bi2O3, 2% SiO2, 10% ZnO, 4% CaO, 15% CuO, 5% Al2O3.

[0038] Comparative Example 7 The difference between this comparative example and Example 1 is as follows: The copper electrode paste for the ring-shaped strontium titanate varistor in this comparative example comprises component raw materials in the following mass percentages: 85% copper conductive powder, 1% inorganic glass binder, 10% terpineol, 3.1% ethyl carbitol acetate, 0.8% ethyl cellulose, 0.1% dispersant ED120; wherein, the inorganic glass binder is prepared according to Formula 4, and Formula 4 comprises component raw materials in the following mass percentages: 31% B2O3, 30% Bi2O3, 2% SiO2, 10% ZnO, 4% CaO, 15% CuO, 5% Al2O3.

[0039] Comparative Example 8 The difference between this comparative example and Example 1 is as follows: The copper electrode paste for the ring-shaped strontium titanate varistor in this comparative example comprises component raw materials in the following mass percentages: 85% copper conductive powder, 0.5% inorganic glass binder, 10% terpineol, 3.6% ethyl carbitol acetate, 0.8% ethyl cellulose, 0.1% dispersant ED116; wherein, the inorganic glass binder is prepared according to Formula 5, and Formula 5 comprises component raw materials in the following mass percentages: 26% B2O3, 30% Bi2O3, 4% SiO2, 15% ZnO, 2% CaO, 19% CuO, 4% Al2O3.

[0040] Comparative Example 9 The difference between this comparative example and Example 1 is as follows: The copper electrode paste for the ring-shaped strontium titanate varistor in this comparative example comprises component raw materials in the following mass percentages: 85% copper conductive powder, 0.5% inorganic glass binder, 10% terpineol, 3.6% ethyl carbitol acetate, 0.8% ethyl cellulose, 0.1% dispersant ED116; wherein, the inorganic glass binder is prepared according to Formula 6, and Formula 6 comprises component raw materials in the following mass percentages: 29% B2O3, 28% Bi2O3, 4% SiO2, 15% ZnO, 2% CaO, 16% CuO, 6% Al2O3.

[0041] The formulas of the inorganic glass binders in the above examples and comparative examples are shown in Table 1.

[0042] Table 1 Formulas of Inorganic Glass Binders (Mass Percentages)

[0043] The inorganic glass binders with different formulas are respectively melted at high temperature to obtain the Figure 1 described high-temperature melting state diagram. From Figure 1It can be seen that at 750 °C, the inorganic glass binders corresponding to Formulas 1 to 4 have a good molten state, while the inorganic glass binders corresponding to Formulas 5 and 6 do not soften; at 850 °C, the inorganic glass binders corresponding to Formulas 1 and 2 have a high molten viscosity, the inorganic glass binders corresponding to Formulas 3 and 4 have a low molten viscosity and serious softening-state flow, and the inorganic glass binders corresponding to Formulas 5 and 6 do not soften sufficiently.

[0044] The component ratios of the copper electrode paste for the annular strontium titanate varistor in the above examples and comparative examples are shown in Table 2.

[0045] Table 2 Component ratios of the copper electrode paste in the examples and comparative examples (mass percentage)

[0046] Application Example (1) The copper electrode pastes of Examples 1-4 and Comparative Examples 1-9 were used to prepare the metallization layer of the annular strontium titanate varistor: the prepared copper paste was printed on the annular strontium titanate varistor substrate by screen printing, dried at 150 °C and then fired in a mesh belt furnace, with the oxygen content in the furnace controlled at 0-30 ppm. The sintering process was as follows: in a nitrogen atmosphere, heated to 500 °C at a heating rate of 15 °C / min and held at the 500 °C degumming zone for 5 min, then heated to 850 °C at a heating rate of 15 °C / min and held at 850 °C for 10 min to obtain the copper metallization samples of the annular strontium titanate varistor.

[0047] The obtained samples were subjected to the pull-off test of the copper layer welded lead. The pull-off effect of the copper layer welded lead is as Figure 2 shown. It can be seen from Figure 2 that in Comparative Example 1 and Comparative Example 9, the copper layer was pulled off by the lead, and the bonding strength was poor; in the samples of Comparative Example 3 and Comparative Example 7, a small amount of ceramic matrix was pulled off, and the bonding strength was average; in Example 1 and Example 4, a large amount of ceramic matrix was directly pulled off by the lead, and the film layer bonding strength was reliable.

[0048] The obtained samples were subjected to the adhesion (N / mm 2 ) test, and the test results are shown in Table 3; the obtained samples were subjected to the test of the electrostatic capacitance value (nF), and the test results are shown in Table 4.

[0049] Table 3 Test results of the adhesion (N / mm 2 ) of the samples

[0050] Table 4 Test results of the electrostatic capacitance value (nF)

[0051] As can be seen from the results in Table 3, the adhesion of the copper paste samples in Examples 1-4, Comparative Example 2, Comparative Example 4, and Comparative Example 5 is ≥ 8 N / mm 2 , meeting the index requirements. In Comparative Example 1, the addition amount of the inorganic glass binder is small, resulting in a low adhesion of the sample; in Comparative Examples 3, 6, and 7, the proportion of copper or aluminum elements in the inorganic glass binder is small, resulting in a small melting viscosity of the glass at 800-900 °C, serious penetration into the ceramic matrix, and an inappropriate addition amount, resulting in a low adhesion of the sample; in Comparative Examples 8 and 9, the proportion of copper and aluminum elements in the inorganic glass binder is large, the softening point of the glass powder is high, the glass does not melt at 800-900 °C, and the adhesion of the copper paste sample is poor.

[0052] As can be seen from Table 4, the electrostatic capacitance values of the copper electrode pastes in Examples 1-4 are ≥ 105 nF, meeting the index requirements; the samples in Comparative Examples 1, 3, and 6-9 have poor binding force and low electrostatic capacitance; although the binding force in Comparative Examples 2, 4, and 5 is relatively good, the addition amount of the inorganic glass binder is large, and during sintering at 800-900 °C, the chemical reaction at the interface between the glass and the matrix is too sufficient, resulting in poor ohmic contact of the sample.

[0053] According to the results in Table 3 and Table 4, compared with Example 1: in Comparative Example 1, due to the small addition amount of the inorganic glass binder, the pull-off force is small and the electrostatic capacitance shifts slightly; in Comparative Example 2, the addition amount of the inorganic glass binder is large, the adhesion of the sample is relatively good, but the electrostatic capacitance decreases significantly; in Comparative Example 3, the aluminum element in the inorganic glass binder is less, the adhesion of the sample is slightly poor, and the electrostatic capacitance decreases slightly; in Comparative Example 4, the aluminum element in the inorganic glass binder is less and the addition amount of the inorganic glass binder is high, the adhesion of the sample is normal, but the electrostatic capacitance decreases; in Comparative Example 5, the aluminum element in the inorganic glass binder is less and the addition amount of the inorganic glass binder is high, the adhesion of the sample is excellent, but the electrostatic capacitance decreases severely; in Comparative Example 6, the copper element in the inorganic glass binder is less, the adhesion of the sample is small, and the electrostatic capacitance decreases slightly; in Comparative Example 7, the copper element in the inorganic glass binder is less and the addition amount of the inorganic glass binder is high, the adhesion of the sample is small, and the electrostatic capacitance is small; in Comparative Example 8, the copper element in the inorganic glass binder is more, the adhesion of the sample is poor, and the electrostatic capacitance is small; in Comparative Example 9, the aluminum element in the inorganic glass binder is more, the adhesion of the sample is poor, and the electrostatic capacitance decreases severely.

[0054] It can be seen that the addition amount of the inorganic glass binder in the copper electrode paste of the present invention has a great influence on the adhesion and electrostatic capacitance of the sample. The introduction of copper and aluminum elements in the formula of the inorganic glass binder promotes the ohmic contact characteristics of the product, but the proportion should be appropriate.

[0055] (2)Sinter the copper electrode paste of Example 2 at different temperatures to prepare a metallized layer of annular strontium titanate varistor, and perform adhesion (N / mm 2 ) test on the obtained samples. The test results are shown in Table 5.

[0056] Table 5 Adhesion (N / mm 2 ) test results after sintering at different temperatures

[0057] As can be seen from Table 5, when the copper electrode paste of Example 2 is sintered at 800 - 900 °C, the adhesion of the paste sample ≥ 8 N / mm 2 , all meeting the index requirements; when the copper electrode paste of Example 2 is sintered at 750 °C, the density of the copper layer is poor, the glass addition amount is small, and the adhesion of the sample is low; the microstructures of the copper layers after the copper electrode paste of Example 2 is sintered at 750 °C and 850 °C are as Figure 3 shown. As can be seen from Figure 3 , at 750 °C, the microstructure diagram of the copper layer shows that the copper layer is relatively loose; while at 850 °C, the copper grains grow significantly, and the density of the copper layer is high. It can be seen that the sintering temperature of the sample in the embodiment of the present invention cannot be lower than 800 °C. At 750 °C, the adhesion is small and the capacitance drops significantly. If the sintering temperature is too low, the density of the copper layer is poor and the adhesion is difficult to guarantee.

[0058] In summary, the appearance of the copper electrode paste for annular strontium titanate varistor prepared by the present invention: paste-like, bright red, uniform and delicate, particle size ≤ 10 µm, viscosity: 100 - 250 Pa·s (25 °C, 5 rpm), firing temperature is 800 - 900 °C; film thickness: 5 - 15 µm; adhesion: ≥ 8 N / mm 2 ; ohmic contact: good, capacitance ≥ 105 nF.

[0059] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0060] The above-described embodiments only represent several implementation manners of the present invention. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A copper electrode paste for a ring-shaped strontium titanate varistor, characterized in that, It is prepared from the following components by mass percentage: 82% - 88% of copper conductive powder, 0.3% - 0.5% of inorganic glass binder, 11% - 18% of organic carrier, and 0 - 0.3% of dispersant.

2. The copper electrode paste for the annular strontium titanate varistor according to claim 1, wherein The inorganic glass binder is a combination of several of B2O3, Bi2O3, SiO2, ZnO, CaO, CuO, and Al2O3, and the particle size of each component is 500 - 1200 mesh.

3. The copper electrode paste for the annular strontium titanate varistor according to claim 2, characterized in that, The mass percentage of each component in the inorganic glass binder is: 25% - 35% of B2O3, 30% - 40% of Bi2O3, 2% - 5% of SiO2, 15% - 25% of ZnO, 1% - 10% of CaO, 16% - 18% of CuO, and 4% - 5% of Al2O3.

4. The copper electrode paste for the annular strontium titanate varistor according to claim 1, characterized in that, The measured softening point of the inorganic glass binder is 600 - 650 °C.

5. The copper electrode paste for the annular strontium titanate varistor according to claim 1, wherein, The particle size of the copper conductive powder is 1 - 2 μm.

6. The copper electrode paste for the annular strontium titanate varistor according to claim 1, wherein The organic carrier includes organic solvent and polymer thickener. The organic solvent is at least one of terpineol and fatty alcohol ester 12, and the polymer thickener is ethyl cellulose; and / or, the dispersant is at least one of dispersant ED116 and dispersant ED120.

7. Application of the copper electrode paste for annular strontium titanate varistor as described in any one of claims 1 - 6 in the preparation of the metallization layer of annular strontium titanate varistor.

8. The application according to claim 7, wherein It includes the following steps: Print the copper electrode paste for annular strontium titanate varistor on the annular strontium titanate varistor ceramic substrate by screen printing. After drying, put it into a mesh belt furnace and sinter in a nitrogen atmosphere.

9. The application according to claim 8, characterized in that, The oxygen content in the mesh belt furnace is 0 - 30 ppm; the sintering curve is to raise the temperature at a heating rate of 15 - 20 °C / min to 400 - 500 °C for degumming for 5 min, and then raise the temperature at a heating rate of 10 - 15 °C / min to 800 - 900 °C and hold for 10 min.

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