Composition and preparation of thick-film copper conductor sintered at different temperatures and different atmospheres

Abstract

The invention relates to composition and preparation of a thick-film copper conductor sintered at different temperatures and different atmospheres, and belongs to the field of chemical preparation. Comprising the following steps: mixing 65-85% of copper powder, 3.0%-15.0% of glass, 15.0%-35.0% of an organic adhesive and 0.1-1.5% of an additive which is one or more of titanium trioxide or stannous oxide, cuprous oxide and copper oxide, rolling into slurry, and sintering at 850-950 DEG C under the protection of nitrogen or ammonia gas to obtain a copper conductor. The medium-temperature copper paste is prepared by the following steps: mixing 60.0-85.0% of copper powder, 3.0-13.0% of glass, 8.0-25.0% of an organic adhesive and 0.2-1.6% of an additive which is one or more of titanium sesquioxide or stannous oxide, cuprous oxide and copper oxide, rolling into paste, and sintering at 450-650 DEG C under the protection of nitrogen or ammonia gas to obtain a copper conductor. The low-temperature copper paste is prepared by mixing 60.0-85.0% of copper powder, 3.0-13.0% of glass, 8.0-25.0% of an organic binder and 0.1-2.0% of an additive which can be one or more of elemental elements of magnesium, zinc, boron and phosphorus or one or more of nickel phosphide, nickel boride, copper phosphide and copper oxide, rolling the mixture into paste, and sintering the paste in air at 250-350 DEG C to obtain a copper conductor.

Description

Technical Field

[0001] The invention discloses an electronic information material produced by a chemical method, belonging to the field of chemical preparation. Background Art

[0002] Patent ZL87101846.2 utilizes an oxidizing atmosphere sintering process. Sintering at 550-700°C can achieve conductivity similar to that of silver conductors, but due to poor solderability, it has not been commercially applied. Copper paste sintered in a protective atmosphere has been industrially adopted both domestically and internationally. Due to copper's superior electrical properties compared to gold, it has been used in multilayer wiring. Tungsten-molybdenum paste processing is complex. Copper conductors have been used in semiconductor coolers, replacing silver conductors in piezoelectric ceramics, replacing silver and silver-palladium conductors in multilayer ceramic capacitor terminals, and replacing silver and silver-palladium electrodes in internal electrodes with nickel. In varistors, copper electrodes have largely replaced silver electrodes. In N-type crystalline silicon solar cells, the current process uses silver electrodes on both sides, resulting in high production costs and hindering the widespread adoption of green energy. To reduce costs, copper electrodes are being considered to replace silver electrodes. Using a protective atmosphere for sintering is inconvenient, and whether it will affect electrical performance is unknown. Therefore, it is expected that oxidizing atmosphere sintering will be developed. This summarizes the current status of copper-based thick-film conductors. Summary of the Invention

[0003] 1. The purpose of the present invention is to replace part of the precious metal thick film conductor paste with a copper thick film conductor paste sintered in a protective atmosphere and an oxidizing atmosphere.

[0004] 2. Technical solution ① A copper conductor paste sintered at 850-950°C in a protective atmosphere. Copper is the functional phase of this invention, and spherical or non-spherical copper powder can be used, with a purity of 99.8-99.95% and a particle size of 0.1-1.2 microns. The inorganic binder glass is composed of oxides of sodium, potassium, silicon, boron, calcium, barium, magnesium, zinc, copper, titanium, and tin, in the following proportions: potassium carbonate 0.1-1.0%, sodium oxide 0.5-1.0%, zinc oxide 0.1-5.0%, silicon dioxide 25.0-53.0%, copper oxide 8.0-15.0%, calcium oxide 0.2-1.0%, magnesium oxide 0.1%-1.0%, boron trioxide 5.0-10.0%, and bismuth trioxide 0.25%-50.0%, for a total of 100%. After mixing, the mixture is melted at 1200-1300°C, quenched in water, and crushed to obtain the product. The organic binder is the well-known ethyl cellulose dissolved in terpineol, butyl carbitol, and benzyl alcohol. The slurry is formulated as follows: 65-85% copper powder, 3.0%-15.0% glass, 15.0%-35.0% organic binder, and 0.1-1.5% additives of one or more of titanium dioxide, stannous oxide, cuprous oxide, or cupric oxide, for a total of 100%. The slurry is mechanically rolled. Sintering at 850-950°C under nitrogen or ammonia protection yields the copper conductor.

[0005] ② Copper conductor paste sintered at a medium temperature of 450-650°C in a protective atmosphere. Commercially available spherical copper powder with a purity of 99.8-99.95% and a particle size of 0.1-1.5 microns is used. The inorganic binder is composed of oxides of magnesium, barium, calcium, aluminum, boron, bismuth, silicon, copper, titanium, and tin. The ingredient ratio is: 0.1-1.0% magnesium oxide, 0.3-1.5% barium oxide, 0.1-1.0% calcium oxide, 10.0-20.0% boron trioxide, 50.0-70.0% bismuth trioxide, 5.0-10.0% silicon dioxide, and 1.0-3.0% aluminum oxide, for a total of 100%. After mixing, the mixture is melted at 1050-1150°C, quenched in water, and crushed. The organic binder is ethyl cellulose dissolved in terpineol, butyl carbitol, and benzyl alcohol. The slurry is prepared by mixing 60.0-85.0% copper powder, 3.0-13.0% glass, 8.0-25.0% organic binder, and 0.2-1.6% additives of one or more of titanium dioxide, stannous oxide, cuprous oxide, or cupric oxide, for a total of 100%. The slurry is then mechanically rolled to produce the copper conductor slurry. The copper conductor is then sintered at 450-650°C under nitrogen or ammonia protection to obtain the copper conductor.

[0006] ③ Copper conductor paste sintered in an oxidizing atmosphere at a low temperature of 250-350°C. Commercially available spherical copper powder with a purity of 99.9-99.99% and a particle size of 0.8-2.0 microns is used. The inorganic binder glass is composed of oxides of bismuth (or lead), tellurium, aluminum, sodium, silicon, molybdenum, and copper. The glass composition is: 45.0-55.0% bismuth trioxide (or lead oxide), 50.0-60.0% tellurium dioxide, 0.1-0.3% aluminum trioxide, 0.2-1.0% sodium oxide, 0.1-0.3% molybdenum trioxide, and 2.0-5.0% silicon dioxide, totaling 100%. After mixing, the mixture is melted at 600-750°C, water quenched, and crushed. The organic binder can be one or more of ethyl cellulose, nitrocellulose, acrylic resin, or cellulose acetate, with a content of 4.0-12.0%. 65.0% terpineol, 25.0% butyl carbitol, and 10.0% benzyl alcohol are added and dissolved to form the organic binder. The slurry is prepared as follows: 60.0-85.0% copper powder, 3.0-13.0% glass, and 8.0-25.0% organic binder. Additives can be magnesium, zinc, one or more of the boron and phosphorus elements listed in one of the inventor's invention patents ZL200610011001.1, ZL200610011050.5, and ZL200610048681.4, or nickel phosphide, nickel boride, copper phosphide, or copper oxide, with a content of 0.1-2.0% to form a total of 100%. After mixing, the mixture is rolled into a slurry and sintered in air at 250-350°C to produce the copper conductor.

[0007] 3. Advantages and positive effects compared with known technologies ① The three copper conductor pastes sintered at different temperatures described in this invention can replace existing precious metal conductor pastes, such as gold paste, silver paste, and silver-palladium paste. This conserves precious metals and reduces the cost of electronic components, resulting in significant economic benefits.

[0008] ② During sintering, in addition to nitrogen, ammonia can also be used as a protective atmosphere. Ammonia decomposes to create a reducing atmosphere, which protects copper. Alternatively, sintering can be performed in oxygen first, followed by reducing the surface copper oxide to copper in hydrogen.

[0009] ③ Titanium oxide or one or more compounds selected from stannous oxide, cuprous oxide, and cupric oxide are added to the copper pastes sintered at three different temperatures.

[0010] ④ Antioxidants such as magnesium, zinc, boron, phosphorus, nickel boride, nickel phosphide, copper phosphide and copper boride are added to the copper paste sintered in the air to meet the requirements of sintering the copper paste in an oxidizing atmosphere.

[0011] ⑤ The copper conductors sintered at three different temperatures have good electrical properties, are similar to silver conductors, have a copper-colored appearance, good solderability, and strong adhesion.

[0012] ⑥ After the application of this invention, the economic and social benefits are obvious.

[0013] ⑦ It can replace the complex process of tungsten-molybdenum slurry in semiconductor cooling sheets.

[0014] ⑧ Copper paste is mainly lead-free. To meet the electrical performance requirements, lead-containing paste can be used in crystalline silicon solar cell applications.

[0015] 9. The present invention uses a mixed resin as the resin component of the organic adhesive. DETAILED DESCRIPTION Example 1

[0016] ① Inorganic binder glass formula and preparation: 1.0% sodium carbonate, 0.5% calcium oxide, 0.5% barium oxide, 0.5% magnesium oxide, 5.5% aluminum oxide, 8.0% zinc oxide, 8.0% boron trioxide, 25.0% silicon dioxide, and 51.0% bismuth trioxide, totaling 100%. After mixing, melt in an alumina crucible at 1300°C, quench with water, and crush to obtain glass powder.

[0017] ② Organic binder preparation: ethyl cellulose 8.0%, terpineol 60.0%, butyl carbitol 35.0%, benzyl alcohol 15.0%, totaling 100%.

[0018] ③ The copper powder used is commercially available spherical copper powder with a purity of 99.9% and a particle size of 0.5 microns.

[0019] ④ Paste preparation: Copper powder 75.0%, glass powder 6.0%, copper oxide 1.0%, organic binder 18.0%, totaling 100%. After mixing, mechanical rolling is performed to obtain copper conductor paste. This is then screen-printed onto an alumina substrate, dried, and sintered at 900°C under nitrogen protection to obtain the copper conductor. Example 2

[0020] The preparation formula is the same as that in Example 1, and ammonia is used as protection during sintering.

[0021] The copper pastes obtained in the above two embodiments can be used as electrodes and conductors in multilayer wiring, multilayer ceramic capacitors, ceramic capacitors, piezoelectric ceramics, and semiconductor refrigerators. Example 3

[0022] ① Inorganic binder glass preparation: 0.2% magnesium oxide, 0.2% calcium oxide, 0.6% barium oxide, 2.0% aluminum oxide, 18.0% boron oxide, 11.0% silicon dioxide, and 68.0% bismuth oxide, totaling 100%. After mixing, melt in a porcelain crucible at 1050°C, quench with water, and crush to obtain glass powder.

[0023] ② Preparation of organic adhesive: 6.0% ethyl cellulose, 60.0% terpineol, 35.0% butyl carbitol, 15.0% benzyl alcohol are mixed, heated and dissolved to obtain the adhesive.

[0024] ③ The copper powder used is commercially available spherical copper powder with a purity of 99.9% and a particle size of 0.5 microns.

[0025] ④ Slurry preparation: Copper powder 75.0%, glass powder 4.0%, cuprous oxide 1.0%, organic binder 20.0%, totaling 100%. After mixing, mechanical rolling is performed to obtain a copper slurry. This is screen-printed onto an alumina substrate and sintered at 550°C under nitrogen to obtain a copper conductor. Example 4

[0026] The preparation formula is the same as that in Example 3, and ammonia protection is used during sintering.

[0027] The above copper paste can be used as electrodes or conductors in components such as varistors and window glass substrates. Example 5

[0028] ① Inorganic binder glass formula and preparation: 0.1% aluminum oxide, 0.5% sodium carbonate, 0.1% molybdenum oxide, 45.3% lead oxide, 54.0% tellurium dioxide, totaling 100%. After mixing, melt in a porcelain crucible at 700°C, cool, and crush to obtain glass powder.

[0029] ② Preparation of organic adhesive formula: 11.0% ethyl cellulose, 1.0% nitrocellulose, 70.0% terpineol, 20.0% butyl carbitol, 10.0% benzyl alcohol, mixed and dissolved to obtain an adhesive.

[0030] ③ Select commercially available spherical copper powder with a purity of 99.98% and a particle size of 0.8 microns.

[0031] ④ Slurry preparation: Copper powder 90.0%, glass 0.7%, copper oxide 0.1%, nickel boride 0.1%, copper phosphide 0.1%, organic binder 9.0%, totaling 100%. After mixing, the mixture is mechanically rolled into a slurry, printed on an alumina substrate, and sintered in air at 300°C to produce a copper conductor.

[0032] This fine line printing can be used as an electrode in crystalline silicon solar cells.

Claims

1. A composition and preparation of a thick film copper conductor sintered at different temperatures and in different atmospheres, characterized by: (1) Formula of copper conductor paste sintered in protective atmosphere at high temperature of 850-950℃: 65-85% copper powder, 3.0%-15.0% inorganic binder glass, 15.0%-35.0% organic binder, additives are one or more of titanium oxide or stannous oxide, cuprous oxide, and cupric oxide, with a content of 0.1-1.5%, totaling 100%, mixed and rolled into paste; The copper powder is commercially available spherical or non-spherical copper powder with a purity of 99.8-99.95% and a particle size of 0.1-1.2 microns; The inorganic adhesive glass formula is as follows: potassium carbonate 0.1-1.0%, sodium oxide 0.5-1.0%, zinc oxide 0.1-5.0%, silicon dioxide 25.0-53.0%, copper oxide 8.0-15.0%, calcium oxide 0.2-1.0%, magnesium oxide 0.1%-1.0%, boron trioxide 5.0-10.0%, bismuth trioxide 0.25%-50.0%, the total amount is 100%; The organic binder is the well-known ethyl cellulose dissolved in terpineol, butyl carbitol, and benzyl alcohol solvents; (2) Formula of copper conductor paste sintered in protective atmosphere at medium temperature of 450-650℃: 60.0-85.0% copper powder, 3.0-13.0% inorganic binder glass, 8.0-25.0% organic binder, and additives of one or more of titanium oxide, stannous oxide, cuprous oxide, and cupric oxide, with a content of 0.2-1.6%, totaling 100%, mixed and rolled into paste; The copper powder is a commercially available spherical copper powder with a purity of 99.8-99.95% and a particle size of 0.1-1.5 microns; The inorganic binder glass formula: magnesium oxide 0.1-1.0%, barium oxide 0.3-1.5%, calcium oxide 0.1-1.0%, boron trioxide 10.0-20.0%, bismuth trioxide 50.0-70.0%, silicon dioxide 5.0-10.0%, aluminum oxide 1.0-3.0%, a total of 100%; The organic binder is the well-known ethyl cellulose dissolved in terpineol, butyl carbitol, and benzyl alcohol solvents; (3) Formula of copper conductor paste sintered in an oxidizing atmosphere at low temperature of 250-350℃: 60.0-85.0% copper powder, 3.0-13.0% inorganic binder glass, 8.0-25.0% organic binder, additives can be one or more elemental elements of magnesium, zinc, boron, phosphorus or one or more of nickel phosphide, nickel boride, copper phosphide, copper oxide, with a content of 0.1-2.0%, totaling 100%, mixed and rolled into paste; The copper powder is a commercially available spherical copper powder with a purity of 99.9-99.99% and a particle size of 0.8-2.0 microns; The inorganic adhesive glass formula is: bismuth trioxide 45.0-55.0% (or lead oxide), tellurium dioxide 50.0-60.0%, aluminum trioxide 0.1-0.3%, sodium oxide 0.2-1.0%, molybdenum trioxide 0.1-0.3%, silicon dioxide 2.0-5.0%, totaling 100%; The organic binder can be one or more of ethyl cellulose, nitrocellulose, acrylic resin, and cellulose acetate, with a content of 4.0-12.0%, and 65.0% of terpineol, 25.0% of butyl carbitol, and 10.0% of benzyl alcohol are added, with a total amount of 100%.

2. The method of claim 1, wherein: (1) The high-temperature copper conductor slurry is sintered at 850-950°C under nitrogen or ammonia protection to obtain the copper conductor; (2) Medium-temperature copper conductor slurry is sintered at 450-650°C under nitrogen or ammonia protection to obtain copper conductor; (3) The low-temperature copper conductor slurry is sintered in air at 250-350℃ to obtain a copper conductor.