A copper conductor paste composition for low temperature sintering under a protective atmosphere and a method of preparing the same

Abstract

This invention relates to the composition and preparation method of a copper conductor paste sintered at medium temperature under a protective atmosphere, belonging to the field of chemical preparation. The invention uses copper powder with a particle size of 0.1-1.0 μm and a purity of over 99.95% as the conductive phase, combined with self-made glass powder and an organic binder, to prepare the copper conductor paste. Sintering is completed at 480-750℃ under a nitrogen or ammonia protective atmosphere, forming a copper conductor with excellent conductivity and strong adhesion, which can directly replace traditional silver conductor pastes. By adjusting the composition of the glass powder and the organic system, this invention is adapted to three temperature ranges: 480-550℃, 550-650℃, and 650-750℃, respectively, and can be applied to devices such as fluorescent displays, varistors, thermistors, and heating elements for automotive rear window defrosting. This invention utilizes abundant and inexpensive copper to replace scarce and expensive silver, significantly reducing the manufacturing cost of electronic components and alleviating the shortage of silver resources, possessing significant economic value and promising industrial application prospects.

Description

Technical Field

[0001] This invention relates to a method for preparing electronic information materials—conductor pastes—using chemical methods, belonging to the field of chemical preparation technology. Background Technology

[0002] The electrodes or leads of most electronic components are made of precious metals, with silver being the most common. In recent years, the photovoltaic solar cell industry has developed rapidly, with cell technology evolving from P-type silicon to N-type silicon, and both the sun-facing and back electrodes are made of silver. my country's current photovoltaic industry capacity has reached over 650GW, consuming approximately 7,000 tons of silver annually. If the silver consumption of other electronic components worldwide is included, the total silver consumption is even greater. Statistics show that the world's annual silver production is approximately 30,000 tons. Silver is a by-product of other major minerals. my country's annual silver production is only 3,000-4,000 tons, resulting in a significant supply gap. For electronic component manufacturers, using base metals to replace silver has become an inevitable trend. When the price of silver reaches over 30,000 yuan per kilogram, using base metals can significantly reduce manufacturing costs. Copper has similar conductivity to silver, but copper is easily oxidized at high temperatures; nickel has slightly lower conductivity and also suffers from easy oxidation. To achieve the substitution of silver with base metals, copper and nickel must be sintered under a protective gas atmosphere (such as ammonia or nitrogen) during the sintering process of electronic components. The medium-temperature sintering described in this invention refers to a sintering process carried out within a temperature range of 480-750℃. This invention expands upon an existing patent application (application number: 202510776415.6), specifically completing sintering within the 480-750℃ temperature range under nitrogen and ammonia protective gas conditions. This sintering temperature range is suitable for a wide variety of electronic components, currently primarily using silver conductor paste. With the continuous rise in silver prices, the replacement of silver conductor paste with copper conductor paste has become imperative. Summary of the Invention

[0003] 1. This invention uses commercially available copper powder, adds self-made glass powder and organic binder, and processes it into copper paste. After printing the paste, it is sintered at 480-750℃ under a nitrogen and ammonia protective atmosphere to obtain copper conductor. This can replace the existing silver conductor paste, realize the replacement of precious metals with base metals, and reduce the manufacturing cost of electronic components.

[0004] 2. Technical Solution ① Sintering copper conductor paste at 480-550℃ (a) Commercially available copper powder, with a particle size of 0.1-1.0 micrometers and a purity of 99.95%; (b) Preparation of glass powder: H3BO3 5-15%, Bi2O3 75-90%, Al2O3 0.1-0.6%, SiO2 0.1-2%, with the total amount of all components being 100%. The raw materials are mixed evenly and placed in a porcelain crucible or corundum crucible, melted at 900-1000℃, and then quenched with water and pulverized to obtain glass powder; (c) Preparation of organic adhesive: Select one or two of ethyl cellulose, polyacrylic acid resin, and cellulose acetate, with a content of 3.0-8.0%; combine with terpineol, ethylene glycol monobutyl ether, diethylene glycol butyl ether, and butyl carbitol acetate, with contents of 40-50%, 30-40%, 10-20%, and 40-60% respectively, with the total amount of all components being 100%, and obtain the adhesive by heating and dissolving. (d) Copper paste preparation: 65-85% copper powder, 0.5-1.5% bismuth trioxide, 10.0-15.0% organic binder, and 5.0-10.0% glass powder, with the total amount of all components being 100%. The above components are mixed and rolled uniformly, and sintered at 480-550℃ under a nitrogen or ammonia protective atmosphere to obtain a copper conductor. This copper paste can be printed onto alumina substrates, window glass substrates, or other electronic components requiring soldering.

[0005] ② Sintering copper conductor paste at 550-650℃ (a) Commercially available copper powder, with a particle size of 0.1-1.0 micrometers and a purity of 99.95%; (b) Glass powder preparation: H3BO3 10-25%, SiO2 2-5%, Bi2O3 65-75%, BaO 0.1-0.5%, MgO 0.1-0.2%, ZnO 0.1-2.0%, with the total amount of all components being 100%. The raw materials are mixed evenly and placed in a porcelain crucible or alumina crucible, melted at 1000-1100℃, and then water-quenched and crushed to produce powdered glass powder; (c) Preparation of organic binder: Same as the preparation process of organic binder for sintered copper conductor paste at 480-550℃; (d) Copper paste preparation: 60-80% copper powder, 4.0-10.0% glass powder, 0.5-2.0% Bi₂O₃, and 10.0-20.0% organic binder, with a total component weight of 100%. The components are mixed and rolled to form a copper paste, which is then screen-printed onto an alumina substrate and sintered at 550-650℃ under a nitrogen or ammonia protective atmosphere to obtain a copper conductor. This paste can replace silver paste for the fabrication of varistors and thermistors, exhibiting good solderability.

[0006] ③ Sinter copper conductor paste at 650-750℃.

[0007] (a) Commercially available copper powder, with a particle size of 0.1-1.0 micrometers and a purity of 99.95%; (b) Glass powder preparation: H3BO3 8.0-15.0%, SiO2 3.0-8.0%, Bi2O3 60.0-75.0%, Na2CO3 0.2-1.0%, ZnO 2.0-5.0%, CaO 0.1-0.8%, Al2O3 0.3-1.5%, BaO 0.1-0.5%, MgO 0.1-0.6%, and one of the four oxides TiO2, Co2O3, Ni2O3, and Fe2O3, with a content of 0.5-1.0%, and the total amount of all components is 100%. The raw materials are mixed evenly, placed in a porcelain crucible or alumina crucible, melted at 1100-1200℃, and then water-quenched and pulverized to obtain glass powder; (c) Preparation of organic binder: Same as the preparation process of organic binder for sintered copper conductor paste at 480-550℃; (d) Copper paste preparation: Copper powder 65.0-85.0%, glass powder 4.0-10.0%, Bi2O3 1.0-3.0%, organic binder 10.0-20.0%, total components 100%. The components are mixed evenly and rolled into copper paste, which is then screen-printed onto an Al2O3 substrate and sintered at 650-750℃ under a nitrogen or ammonia protective atmosphere to obtain a copper conductor. The copper paste prepared by this invention can be used in the heating element of the defrosting glass for automotive rear windows, replacing existing silver paste. The sintering process of the paste can be carried out simultaneously with the tempering process of the rear window glass. Depending on the manufacturer's requirements, different colors can be achieved by adding Ti, Co, Ni, and Fe oxides.

[0008] 3. Advantages and positive effects compared with known technologies ① The present invention aims to replace expensive silver paste with inexpensive copper paste. Copper has similar conductivity to silver. By adjusting the type of binder and the composition of glass powder, and combining it with a protective atmosphere sintering process, copper can effectively replace silver, which has significant economic value. This technology is especially important in the context of a shortage of silver supply. ② 480-550℃ sintered copper paste. In this temperature range, silver paste is traditionally used. It is mainly suitable for fluorescent displays with window glass as the substrate, positive temperature coefficient thermistors with printed aluminum paste or silver paste for ohmic contact electrodes. Printed silver paste can realize lead wire soldering. The high price of silver has brought huge cost pressure to manufacturers, and there is an urgent need to use copper paste to replace silver paste. ③ 550-650℃ sintered copper paste. This type of product is mainly suitable for varistors with zinc oxide as the substrate. Existing products mainly use silver conductors as electrodes. Silver has excellent conductivity and can meet the requirements for lightning current impulse. Copper has similar conductivity to silver, so copper can replace silver, which will greatly reduce the cost and has important economic significance. ④ Copper paste sintered at 650-750℃: This type of paste is suitable for automotive rear window defrosters and is used for defogging. The heating element is made by sintering silver paste. In terms of process, after the silver paste is printed, it is sintered together with the tempered window glass. Each car uses about 10 grams of silver paste. Cars are now common in almost every household, and both fuel vehicles and new energy vehicles have defrosters. The amount of silver paste used per car has little impact on the cost. The main problem is the difficulty in supplying silver, so it is necessary to completely replace silver with copper to save resources. Detailed Implementation

[0009] Example 1: Preparation of copper sintering paste at 520℃ Commercially available copper powder with a particle size of 0.5 micrometers and a purity of 99.95% was used. Glass powder preparation: H3BO3 15.0%, SiO2 2.0%, Al2O3 0.5%, Bi2O3 82.5%, total amount of all components 100%. The raw materials are mixed evenly, placed in a porcelain crucible, and melted at 1000℃ for half an hour. After water quenching, pulverizing and drying, glass powder is obtained. Preparation of organic binder: Ethyl cellulose 6.0%, terpineol 55.0%, ethylene glycol monobutyl ether 10.0%, diethylene glycol monobutyl ether 20.0%, diethylene glycol monobutyl ether acetate 9.0%, total of all components 100%. Mix the raw materials evenly, heat and stir until completely dissolved; Copper paste preparation: Copper powder 73.0%, glass powder 7.0%, organic binder 20.0%, total components 100%. After the components are mixed evenly, the paste is rolled into copper paste using a rolling mill. Copper paste was screen-printed onto an alumina substrate and sintered at 520°C under a nitrogen protective atmosphere to obtain a copper conductor. Testing showed that the sheet resistance of the copper conductor was 2.2 mΩ / □ and the peel strength was greater than 20.0 N. This paste can be used in fluorescent panels with window glass as the substrate, and in electronic components that need to replace silver paste within this temperature range.

[0010] Example 2: Preparation of copper conductor sintered at 600℃ The copper powder used is the same as in Example 1; Glass powder preparation: H3BO3 15.0%, Bi2O3 74.0%, Al2O3 1.0%, BaO 1.5%, SiO2 8.0%, MgO 0.5%, with a total component weight of 100%. The raw materials were mixed evenly, placed in a porcelain crucible, melted at 1080℃, and then water-quenched and pulverized to obtain glass powder. Preparation of organic adhesive: Same as in Example 1; Copper paste preparation: 71.0% copper powder, 10.0% glass powder, 1.0% Bi₂O₃, and 18.0% organic binder, with a total component weight of 100%. The components are mixed and rolled to form a copper paste, which is then printed onto an Al₂O₃ substrate and sintered at 600℃ under ammonia atmosphere to obtain a copper conductor. Testing showed a sheet resistance of 2.3 mΩ / □, indicating good adhesion to the substrate. This copper paste can be used for fabricating varistor electrodes and electrodes for other electronic components within this temperature range.

[0011] Example 3: Preparation of copper conductor sintered at 680℃ The copper powder used is the same as in Example 1; Glass powder preparation: H3BO3 15.0%, Bi2O3 68.0%, SiO2 10.0%, ZnO 5.0%, Na2CO3 0.5%, CaO 0.5%, TiO2 1.0%, with a total component weight of 100%. The raw materials were mixed evenly, placed in a porcelain crucible, melted at 1130℃, and then water-quenched and crushed to obtain glass powder. Preparation of organic adhesive: Same as in Example 1; Copper paste preparation: Copper powder 70.0%, glass powder 12.0%, Bi2O3 1.0%, organic binder 17.0%, total components 100%. The components are mixed and rolled to form copper paste. Copper paste was screen-printed onto a glass substrate and sintered at 680℃ under a nitrogen protective atmosphere to obtain a copper conductor. The back of the conductor is light brown, and it exhibits good adhesion to the substrate. Testing showed a sheet resistance of 3.0 mΩ / □. This copper conductor can be used in automotive rear window defrosters as a replacement for silver paste, and can also be used to fabricate electrodes for other electronic components within this temperature range.

[0012] This invention uses abundant copper to replace scarce silver, thereby significantly reducing the cost of raw materials and component manufacturing while ensuring the performance of electronic components meets the required standards.

Claims

1. A copper conductor paste composition and preparation method for medium-temperature sintering under a protective atmosphere, characterized in that: The formula for copper conductor paste sintering at 480-550℃ under a protective atmosphere is as follows: 65-85% copper powder, 0.5-1.5% bismuth trioxide, 10.0-15.0% organic binder, and 5.0-10.0% glass powder. The total amount of all components is 100%. After mixing, the paste is rolled into a paste. The copper powder is commercially available, with a particle size of 0.1-1.0 micrometers and a purity of 99.95%. The inorganic adhesive glass formulation is as follows: H3BO3 5-15%, Bi2O3 75-90%, Al2O3 0.1-0.6%, SiO2 0.1-2%, with the total amount of all components being 100%. The organic binder is selected from one or two of ethyl cellulose, polyacrylic acid resin, and cellulose acetate, with a content of 3.0-8.0%; it is combined with terpineol, ethylene glycol monobutyl ether, diethylene glycol butyl ether, and butyl carbitol acetate, with contents of 40-50%, 30-40%, 10-20%, and 40-60%, respectively, and the total amount of all components is 100%. The formula for copper conductor slurry sintered at 550-650℃ under a protective atmosphere is as follows: 60-80% copper powder, 4.0-10.0% glass powder, 0.5-2.0% Bi2O3, and 10.0-20.0% organic binder. The total amount of all components is 100%. The mixture is rolled into a slurry. The copper powder is commercially available, with a particle size of 0.1-1.0 micrometers and a purity of 99.95%. The inorganic binder glass formulation is as follows: H3BO3 10-25%, SiO2 2-5%, Bi2O3 65-75%, BaO 0.1-0.5%, MgO 0.1-0.2%, ZnO 0.1-2.0%, with the total amount of all components being 100%. The organic binder is prepared using the same process as the organic binder for sintered copper conductor paste at 480-550℃. The formula for copper conductor slurry sintered at 650-750℃ under a protective atmosphere is as follows: copper powder 65.0-85.0%, glass powder 4.0-10.0%, Bi2O3 1.0-3.0%, organic binder 10.0-20.0%, with the total amount of all components being 100%. After mixing, the mixture is rolled into a slurry. The copper powder is commercially available, with a particle size of 0.1-1.0 micrometers and a purity of 99.95%. The inorganic binder glass formulation is as follows: H3BO3 8.0-15.0%, SiO2 3.0-8.0%, Bi2O3 60.0-75.0%, Na2CO3 0.2-1.0%, ZnO 2.0-5.0%, CaO 0.1-0.8%, Al2O3 0.3-1.5%, BaO 0.1-0.5%, MgO 0.1-0.6%, and one of the four oxides TiO2, Co2O3, Ni2O3, and Fe2O3 is selected, with a content of 0.5-1.0%, and the total amount of all components is 100%. The organic binder is prepared using the same process as the organic binder for sintering copper conductor paste at 480-550℃.

2. The composition and preparation method of a copper conductor paste sintered at medium temperature under a protective atmosphere according to claim 1, characterized in that: Copper conductor paste sintered in a protective atmosphere at 480-550℃ can be printed on the surface of alumina substrates, window glass substrates, or other electronic components that require soldering. Copper conductor paste sintered in a protective atmosphere at 550-650℃ can be printed on alumina substrates and used in the fabrication of varistors and thermistors, and has good solderability. Copper conductor paste sintered at 650-750℃ under a protective atmosphere can be printed on alumina substrates and used in heating elements for defrosting glass in automotive rear windows.