Glass-coated copper powder, copper paste, copper electrode and preparation method thereof

Abstract

The present invention discloses a method for preparing glass-coated copper powder, comprising: adding a silicon-containing precursor, a boron-containing precursor, and an inorganic zinc salt to an organic solvent, mixing and dissolving them to obtain a zinc borosilicate glass sol solution; adding copper powder to the zinc borosilicate glass sol solution and mixing, then purging the volatilized organic solvent with a non-oxidizing gas to obtain zinc borosilicate gel-coated copper powder; calcining the zinc borosilicate gel-coated copper powder at 200-600°C for 3-6 hours, and obtaining zinc borosilicate glass-coated copper powder after cooling; no additional water is added during the preparation process, and the calcination is staged. The present invention also discloses a method for mixing the glass-coated copper powder with an organic polymer and an organic solvent to prepare a glass-coated copper slurry; and a method for coating the glass-coated copper slurry on a substrate and calcining it at 600-800°C to prepare a copper electrode. The glass-coated copper slurry prepared by the present invention has strong substrate adhesion; the copper electrode prepared by the present invention has low square resistance and strong resistance to electrical conductivity decay.

Description

Technical Field

[0001] The present invention relates to the field of electronic materials, and in particular to glass-coated copper powder, copper slurry, copper electrode and preparation methods thereof. Background Art

[0002] Copper powder and borosilicate glass are two key raw materials used in conductive copper pastes, widely used in electrodes for multilayer ceramic capacitors, integrated circuit signal transmission, and conductive layers in semiconductor packaging. Copper powder provides excellent conductivity, while borosilicate glass effectively bonds copper to other substrates after high-temperature calcination. However, traditional borosilicate glass requires melting at temperatures of 1,000 degrees Celsius or above, which consumes a lot of energy. Furthermore, it is difficult to fully wet and spread the copper powder surface during mixing and sintering. This results in poor adhesion of the prepared copper paste, and copper powder exposed to air easily oxidizes, increasing its resistance.

[0003] In order to solve the above technical problems, some researchers have proposed a sol-gel method. This method is more energy-saving and environmentally friendly, can prepare a glass system at a lower temperature, and can promote the uniform distribution and spreading of the glass phase and the copper phase. The prepared copper slurry has better substrate adhesion performance. For example, two patent application documents CN105957641A and CN107745119A disclosed by Tianjin University for coating copper powder using the sol-gel method were used to prepare barium zinc borosilicate and barium borosilicate sol-gel coated copper powder, respectively. The precursors used were ethyl orthosilicate, boric acid, barium acetate and zinc acetate, and the solvent was ethanol. It was necessary to add additional water and heat for hydrolysis. However, the sol-gel glass prepared by the water system has a large number of surface hydroxyl groups, which will affect the dielectric properties of the material and erode the copper powder. In order to remove the hydroxyl groups on the surface of the sol-gel glass, it is necessary to calcine for a long time, which has a high energy consumption. Furthermore, boric acid, a common boron precursor, evaporates rapidly at room temperature. Furthermore, sol-gel formation is a time-consuming reaction, and its volatilization can significantly distort the material composition ratio. Low-boiling-point solvents such as ethanol can also cause azeotropy, accelerating the distortion of the system's stoichiometric ratio. Furthermore, the glass coating of the barium zinc borosilicate and barium borosilicate sol-gel-coated copper powders prepared using the above method accounts for 2% to 9% of the copper powder's mass. The narrow range of glass coating thickness results in poor resistance to conductivity decay. Summary of the Invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a method for preparing glass-coated copper powder, copper paste, copper electrode by a water-free sol-gel method and the preparation method thereof.

[0005] In a first aspect, the present invention provides a method for preparing glass-coated copper powder, the method comprising the following steps:

[0006] A silicon-containing precursor, a boron-containing precursor and an inorganic zinc salt are added to an organic solvent, mixed and dissolved to obtain a zinc borosilicate glass sol solution; copper powder is added to the zinc borosilicate glass sol solution and mixed, and the organic solvent is volatized by sweeping with a non-oxidizing gas to obtain zinc borosilicate gel-coated copper powder; the zinc borosilicate gel-coated copper powder is calcined at 200-600°C for 3-6 hours, and after cooling, zinc borosilicate glass-coated copper powder is obtained; wherein, no additional water is added during the preparation process, and the calcination is a staged calcination.

[0007] Preferably, the silicon-containing precursor, the boron-containing precursor and the inorganic zinc salt are added to the organic solvent for mixed dissolution by stirring and dissolving at room temperature. After the mixed dissolution, the mixture can be left to stand for 1-8 hours so that the silicon-containing precursor, the boron-containing precursor, the inorganic zinc salt and the organic solvent are fully mixed to form a uniform zinc borosilicate glass sol solution.

[0008] Optionally, the boiling points of the silicon-containing precursor and the boron-containing precursor are both higher than 165°C.

[0009] Optionally, the silicon-containing precursor may be tetraethyl orthosilicate and / or orthosilicic acid, the boron-containing precursor may be an alkyl borate, and the inorganic zinc salt may be zinc nitrate hexahydrate.

[0010] Optionally, the alkyl borate can be one or more of tripropyl borate, tributyl borate, dibutyl borate, monopentyl borate, and dipentyl borate.

[0011] Optionally, the inorganic zinc salt is an inorganic zinc salt soluble in an alcohol solvent or an alcohol ether solvent, preferably, zinc nitrate hexahydrate.

[0012] Optionally, the boiling point of the organic solvent is higher than 110°C.

[0013] Optionally, the organic solvent may be one or more of butanol, pentanol, ethylene glycol methyl ether, propylene glycol methyl ether, and propylene glycol ethyl ether.

[0014] Optionally, the molar percentages of the silicon-containing precursor, the boron-containing precursor, and the inorganic zinc salt in the total molar number of the three are in the range of 1-15%, 25-60%, and 35-60%, respectively.

[0015] Optionally, the particle size of the copper powder is 0.2-10 microns, and the mass of the copper powder is 4-99 times the total mass of the silicon precursor, the boron precursor and the inorganic zinc salt.

[0016] Optionally, copper powder can be added to the zinc borosilicate glass sol solution and the mixture can be stirred appropriately, and the volatile organic solvent and residual water can be swept out by a non-oxidizing gas such as nitrogen, so that the zinc borosilicate glass sol gradually changes into a viscous gel state and is evenly coated on the surface of the copper powder until no obvious liquid remains.

[0017] Optionally, the zinc borosilicate gel-coated copper powder is calcined at 200-600° C. for 3-6 hours in a non-oxidizing gas atmosphere.

[0018] Furthermore, the zinc borosilicate gel-coated copper powder is calcined at 200-600° C. for 3-6 hours using a staged calcination method. For example, it can be calcined at 200-300° C. for 1-2 hours and then calcined at 450-600° C. for 2-4 hours.

[0019] Optionally, the non-oxidizing gas is one of nitrogen, helium, neon, argon, krypton, and xenon, or a mixture of two or more of the above.

[0020] The present invention adopts an anhydrous system as a medium for the sol-gel reaction, triggering the hydrolysis of the precursor through the crystal water of the inorganic salt and the non-electrolytic hydroxyl group in the solvent, thereby avoiding corrosion of the copper powder and not requiring heating for hydrolysis. It has advantages that the sol-gel method prepared by the aqueous system does not have, and improves the simplicity, operability and repeatability of the process.

[0021] The present invention also maintains a stable material composition ratio by employing a high-boiling-point system. By using a high-boiling-point precursor and a relatively high-boiling-point organic solvent, distortion in the composition ratio caused by volatilization of the glass component can be effectively reduced. Furthermore, compared to existing technologies, the glass-coated copper powder prepared using the present invention has a wider range of glass mass to glass-coated copper powder mass ratio, up to 15%. This higher glass mass ratio effectively improves the resistance to electrical conductivity decay of the subsequently prepared copper slurry and copper electrodes.

[0022] In a second aspect, the present invention further provides a method for preparing a glass-coated copper paste, wherein the glass-coated copper powder prepared by the method of the first aspect of the present invention is mixed with an organic polymer and an organic solvent to prepare the glass-coated copper paste.

[0023] Optionally, the mixing can be centrifugal mixing or mechanical stirring. Centrifugal mixing can be performed at a speed of 1500-3000 rpm for 1-5 minutes. Mechanical stirring can be performed at a speed of 800-2000 rpm for 3-10 minutes using stirring paddles of various shapes.

[0024] Optionally, the mass percentages of the glass-coated copper powder, the organic polymer, and the organic solvent are 60-90%, 1-5%, and 9-35%, respectively.

[0025] Optionally, the organic polymer is one or more of polyacrylate, ethyl cellulose, polyvinyl alcohol, and polyvinyl butyral ester, and the organic solvent is one or more of terpineol, diethylene glycol butyl ether, diethylene glycol butyl ether acetate, and lauryl alcohol ester.

[0026] The glass-coated copper paste prepared by the method provided by the second aspect of the present invention has strong substrate adhesion and strong resistance to conductivity decay.

[0027] In a third aspect, the present invention further provides a method for preparing a copper electrode, wherein the glass-coated copper paste prepared by the method of the second aspect of the present invention is coated on a substrate and calcined at 600-800° C. to prepare a copper electrode.

[0028] Optionally, the coating thickness is 20-150 microns.

[0029] Optionally, the calcination is performed at 600-800° C. in a non-oxidizing gas atmosphere.

[0030] Optionally, the calcination time is 1-4 hours.

[0031] Optionally, the substrate is made of ceramic, glass, silicon, silicon carbide or metal.

[0032] The copper electrode prepared by the method provided in the third aspect of the present invention has a low square resistance and strong resistance to conductivity decay. The increase in square resistance after being placed for 4 weeks is also very small. The square resistance can be measured using a testing equipment such as a four-probe resistance meter. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 shows a scanning electron micrograph of untreated nano-copper powder;

[0034] Figure 2 The scanning electron microscope image of the zinc-borosilicate glass-coated nano-copper powder prepared in Example 1 is shown, where the mass ratio of the zinc-borosilicate glass is 10%;

[0035] Figure 3 shows a scanning electron micrograph of untreated micronized copper powder;

[0036] Figure 4 The scanning electron microscope image of zinc borosilicate glass coated micron copper powder prepared in Example 2 is shown, where the mass ratio of zinc borosilicate glass is 10%;

[0037] Figure 5 The scanning electron microscope image of zinc borosilicate glass coated micron copper powder prepared in Example 3 is shown, and the mass ratio of zinc borosilicate glass is 15%. DETAILED DESCRIPTION

[0038] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that those skilled in the art may make several variations and improvements without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0039] The present invention is achieved through the following specific steps:

[0040] 1) Preparation method of anhydrous zinc borosilicate sol

[0041] Zinc borosilicate glass nanogel is formed in an organic solvent using organic precursors and inorganic salts. The organic precursors include high-boiling-point silicon-containing precursors and boron-containing precursors, wherein the boiling points of the silicon-containing precursor and the boron-containing precursor are both higher than 165°C, for example, the boiling point range is 165-240°C; the inorganic salt can be an inorganic zinc salt, and the organic solvent is a high-boiling-point alcohol or alcohol ether, wherein the boiling point of the alcohol or alcohol ether is both higher than 110°C, for example, the boiling point range is 110-140°C. Optionally, the silicon-containing precursor can be tetraethyl orthosilicate or tetrapropyl orthosilicate; the boron-containing precursor can be tripropyl borate or tributyl borate; the inorganic zinc salt is zinc nitrate hexahydrate or other inorganic zinc salt soluble in alcohol or alcohol ether organic solvents; the alcohol or alcohol ether can be one or more of butanol, amyl alcohol, ethylene glycol methyl ether, or propylene glycol methyl ether.

[0042] The specific steps are to add a silicon-containing precursor, a boron-containing precursor, and an inorganic zinc salt to an alcohol or alcohol ether solvent in a stoichiometric ratio, wherein the molar ratio of the silicon-containing precursor, the boron-containing precursor, and the inorganic zinc salt is 1-15% silicon-containing precursor, 25-60% boron-containing precursor, and 35-60% inorganic salt. The mass of the alcohol or alcohol ether solvent is 3-10 times the total mass of all precursors and the inorganic zinc salt. The mixture is stirred and dissolved at room temperature and allowed to stand for 1-8 hours.

[0043] 2) Preparation method of zinc borosilicate gel-coated copper powder

[0044] Copper powder with a particle size of 0.2-10 microns is added to the zinc borosilicate sol, with the mass of the copper powder being 4-99 times the combined mass of all precursors and inorganic zinc salts in the zinc borosilicate sol. Stirring may be used as appropriate, and a non-oxidizing gas, such as nitrogen, is used to purge the volatile organic solvent and any residual moisture, gradually transforming the zinc borosilicate sol into a viscous gel. The gel is then uniformly coated on the surface of the copper powder until no significant liquid remains. In the present invention, the non-oxidizing gas is a gas that does not chemically react with the copper powder at room temperature, such as nitrogen or an inert gas.

[0045] 3) Preparation method of zinc borosilicate glass coated copper powder

[0046] The zinc-borosilicate gel-coated copper powder obtained by the above method is calcined at 200-300°C in a non-oxidizing atmosphere for 1-2 hours to volatilize any residual alcohol or alcohol ether solvents, as well as the ethanol, propanol, or butanol products produced by hydrolysis of the precursor during the preparation of the zinc-borosilicate gel. Calcination is then continued at 450-600°C for 2-4 hours to fully densify the zinc-borosilicate gel into a glassy state. After cooling, the zinc-borosilicate glass-coated copper powder is obtained, wherein the zinc-borosilicate glass accounts for up to 15% of the mass of the zinc-borosilicate glass-coated copper powder after calcination.

[0047] 4) Preparation method of copper slurry of zinc borosilicate glass coated copper powder

[0048] The specific steps include high-speed mixing of the zinc-borosilicate glass-coated copper powder, an organic polymer, and an organic solvent, wherein the mass ratio of the zinc-borosilicate glass-coated copper powder is 60-90%, the mass ratio of the organic polymer is 1-5%, and the mass ratio of the organic solvent is 9-35%. The organic polymer is one or more of polyacrylate, ethyl cellulose, polyvinyl alcohol, and polyvinyl butyral ester. The organic solvent is one or more of terpineol, diethylene glycol butyl ether, diethylene glycol butyl ether acetate, and lauryl ester. The high-speed mixing can be centrifugal mixing or mechanical stirring. The centrifugal mixing can be performed at a speed of 1500-3000 rpm for 1-5 minutes, and the mechanical stirring can be performed at a speed of 800-2000 rpm for 3-10 minutes using stirring paddles of various shapes.

[0049] 5) Usage and testing methods of copper paste

[0050] The prepared copper paste can be coated on a substrate with a coating thickness of 20-150 microns. After calcination at 600-800°C for 1-4 hours in a non-oxidizing gas atmosphere, a copper electrode is obtained. The substrate comprises ceramic, glass, silicon, silicon carbide or metal. The square resistance of the prepared copper electrode can be measured using a four-probe resistance meter. In the present invention, square resistance refers to "square resistance", that is, the resistance between two opposite sides of a square thin film conductive material.

[0051] The adhesion of the copper paste of the obtained copper electrode can be tested using the "tape method". Specifically, a 10×10=100 grid matrix is ​​drawn on the side of the tape containing glue, and each grid is a square with a length and width of 1 mm. The tape is attached to the copper electrode obtained by calcining the copper paste, and then the tape is torn off. The number of grids without copper adhesion in the 100 grids is counted. The more grids without copper adhesion, the stronger the adhesion of the copper paste on the substrate.

[0052] As can be seen from the above preparation process, the present invention utilizes an anhydrous system as the medium for the sol-gel reaction. Hydrolysis of the precursor is triggered by the crystalline water of the inorganic salt and the non-electrolytic hydroxyl groups in the solvent. No additional water is added during the preparation process, thus preventing corrosion of the copper powder. Furthermore, neither heating for hydrolysis nor calcination for removal of hydroxyl groups is required, resulting in a short calcination time and low energy consumption. Therefore, the present invention offers advantages not possessed by aqueous sol-gel methods, improving process simplicity, operability, and reproducibility.

[0053] The present invention also maintains a stable material composition ratio by employing a high-boiling-point system. By using a high-boiling-point precursor and a relatively high-boiling-point organic solvent, distortion in the composition ratio caused by volatilization of the glass component can be effectively reduced. The glass-coated copper powder prepared by the present method can have a glass mass-to-coated copper powder mass ratio of up to 15%. This high glass mass ratio effectively improves the resistance to electrical conductivity decay of the subsequently prepared copper slurry and copper electrodes.

[0054] In order to further illustrate the technical effects of the present invention, the inventors conducted multiple experiments.

[0055] Table 1 lists the parameters for preparing glass-coated copper powder in the relevant examples. Examples 1-5 all used tetraethyl orthosilicate as the silicon-containing precursor, tributyl borate as the boron-containing precursor, zinc nitrate hexahydrate as the inorganic zinc salt, and nitrogen as the non-oxidizing gas. Examples 1-3 used propylene glycol methyl ether as the organic solvent, while Examples 4-5 used butanol as the organic solvent.

[0056] Table 1

[0057]

[0058]

[0059] Table 2 lists the parameters for the glass-coated copper paste and copper electrode preparation methods in the relevant examples. In Examples 1-5, the organic polymer used was ethyl cellulose, the organic solvent used was a mixture of diethylene glycol butyl ether and diethylene glycol butyl ether acetate, and the non-oxidizing gas used was nitrogen. In Examples 1-3, the substrate material was silicon, while in Examples 4-5, the substrate material was copper.

[0060] Table 2

[0061]

[0062] Example 1

[0063] Use 1.12g of tetraethyl orthosilicate, 2.46g of tributyl borate, 4.78g of zinc nitrate hexahydrate, add it into 50g of propylene glycol methyl ether solution and mix for 10 minutes until there is no precipitation and the solution is clear and transparent, and let it stand for 6 hours. Figure 1 ) was added to the solution and stirred under nitrogen purge for 4 hours until all the solvent evaporated to obtain a viscous gel-coated copper powder. The gel-coated copper powder was calcined at 300 ° C for 1 hour under nitrogen atmosphere, then heated to 550 ° C for 2 hours and cooled to obtain zinc borosilicate glass-coated copper powder ( Figure 2 ), wherein the mass ratio of zinc borosilicate glass to zinc borosilicate glass coated copper powder is 10%.

[0064] 8 g of the obtained zinc borosilicate glass-coated nano-copper powder was weighed, mixed with 0.9 g of diethylene glycol butyl ether, 0.9 g of diethylene glycol butyl ether acetate and 0.2 g of ethyl cellulose, and mixed in a high-speed centrifugal mixer at 2000 rpm for 2 minutes to obtain a copper slurry.

[0065] The copper paste was evenly coated on the surface of a 99.9999% silicon wafer using a 75-micron scraper, calcined at 650°C for 2 hours in a nitrogen atmosphere, and then cooled to obtain a silicon wafer and copper electrode structure.

[0066] The sheet resistance of the copper electrode was measured to be 23.5 microohms using a four-probe resistance meter. After four weeks in air, the sheet resistance was 38.9 microohms. The copper paste adhesion of the copper electrode was measured using the tape method using 3M 610 tape, and the number of grids with no copper adhesion was 82.

[0067] Example 2

[0068] The specific preparation method is the same as that of Example 1, except that the nano copper powder used in Example 1 is changed to copper powder with a particle size of 1-10 microns, i.e., 1000-10000 nano copper powder ( Figure 3 ), the obtained zinc borosilicate glass coated copper powder ( Figure 4 ), wherein the mass ratio of zinc borosilicate glass to zinc borosilicate glass coated copper powder is 10%.

[0069] The sheet resistance of the copper electrode was measured to be 22.1 microohms using a four-probe resistance meter. After four weeks in air, the sheet resistance was 26.4 microohms. The copper paste adhesion of the copper electrode was measured using the tape method using 3M 610 tape, with the number of grids without copper adhesion being 100.

[0070] Example 3

[0071] The specific preparation method is the same as that of Example 1, except that the nano copper powder used in Example 1 is changed to copper powder with a particle size of 1-10 microns, i.e., 1000-10000 nano copper powder, and the mass is changed to 28.3 g. The obtained zinc borosilicate glass coated copper powder with thickened coating layer ( Figure 5), wherein the mass ratio of zinc-borosilicate glass to zinc-borosilicate glass-coated copper powder is 15%.

[0072] The sheet resistance of the copper electrode was measured to be 29.2 microohms using a four-probe resistance meter. After four weeks in air, the sheet resistance was 38.9 microohms. The copper paste adhesion of the copper electrode was measured using the tape method using 3M 610 tape, with the number of grids without copper adhesion being 100.

[0073] Example 4

[0074] 0.55g of tetraethyl orthosilicate, 3.65g of tributyl borate, and 4.71g of zinc nitrate hexahydrate were added to 50g of butanol solution and mixed for 20 minutes until there was no precipitation and the solution was clear and transparent, and then allowed to stand for 8 hours. 50g of copper powder with a particle size of 200-1000 nanometers was added to the solution, and the solution was stirred under nitrogen for 4 hours until all the solvent evaporated to obtain a viscous gel-coated copper powder. The gel-coated copper powder was calcined at 300°C for 1 hour under a nitrogen atmosphere, then heated to 570°C for 2 hours and cooled to obtain zinc borosilicate glass-coated copper powder.

[0075] 7g of the zinc-borosilicate glass-coated copper powder was weighed with 1.4g of butyl diglycol, 1.3g of butyl diglycol acetate, and 0.3g of ethyl cellulose. The mixture was mixed in a high-speed centrifugal mixer at 2000 rpm for 2 minutes to obtain a copper slurry. The slurry was evenly applied to the surface of a 99.99% copper sheet using a 150-micron scraper. The copper sheet was then calcined at 750°C in a nitrogen atmosphere for 2 hours and cooled.

[0076] The sheet resistance of the copper electrode was measured to be 1.7 microohms using a four-probe resistance meter, and 8.9 microohms after four weeks in air. The copper paste adhesion to the copper electrode was measured using the tape method using 3M 610 tape, and the number of grids with no copper adhesion was 94.

[0077] Example 5

[0078] The specific preparation method is the same as that of Example 4, except that the nano copper powder used in Example 4 is changed to copper powder with a particle size of 1-10 microns, i.e., 1000-10000 nano copper powder, and the substrate is changed to a ceramic sheet (the ceramic sheet is selected from Fulu Chemical A6).

[0079] The sheet resistance of the copper electrode was measured to be 11.0 microohms using a four-probe resistance meter. After four weeks in air, the sheet resistance was 15 microohms. Adhesion testing was not performed because the ceramic disc was too brittle and easily broke during the tape test.

[0080] The protection content of the present invention is not limited to the above embodiments. Without departing from the spirit and scope of the present invention, changes and advantages that can be thought of by those skilled in the art are included in the present invention and are protected by the appended claims.

[0081] Comparative Example 1

[0082] 1.12g of tetraethyl orthosilicate, 0.66g of boric acid, and 4.78g of zinc nitrate hexahydrate were added to 25g of propylene glycol methyl ether solution and 25g of water, mixed for 10 minutes until there was no precipitation and the solution was clear and transparent, and allowed to stand for 6 hours. 50g of copper powder with a particle size of 200-1000 nanometers was added to the solution, purged with nitrogen for 4 hours, and stirred until all the solvent evaporated to obtain a viscous gel-coated copper powder. The gel-coated copper powder was calcined at 300°C for 1 hour under a nitrogen atmosphere, then heated to 550°C and calcined for 2 hours and cooled to obtain zinc borosilicate glass-coated nano-copper powder.

[0083] 8g of the zinc-borosilicate glass-coated nano-copper powder was weighed with 0.9g of butyl diglycol, 0.9g of butyl diglycol acetate, and 0.2g of ethyl cellulose. The mixture was mixed in a high-speed centrifugal mixer at 2000 rpm for 2 minutes to produce a copper slurry. The copper slurry was evenly applied to the surface of a 99.9999% silicon wafer using a 75-micron scraper. The wafer was then calcined at 650°C in a nitrogen atmosphere for 2 hours and cooled to produce a silicon wafer and copper electrode structure.

[0084] The sheet resistance of the copper electrode was measured using a four-probe resistance meter to be 48.7 microohms. After four weeks in air, the sheet resistance was 70.7 microohms. The copper paste adhesion of the copper electrode was measured using the tape method using 3M 610 tape, and the number of grids with no copper adhesion was 74.

[0085] Comparative Example 2

[0086] 0.32g of silicon dioxide, 0.72g of boric acid, and 4.78g of zinc nitrate hexahydrate were melted at 1100°C for 2 hours, quenched at room temperature, and ground with zirconium beads to obtain zinc borosilicate glass powder with a particle size of 3-10 microns. 50g of copper powder with a particle size of 1-10 microns, 7.5g of diethylene glycol butyl ether, 7.5g of diethylene glycol butyl ether acetate, and 1.7g of ethyl cellulose were weighed and mixed. The mixture was then mixed in a high-speed centrifugal mixer at 2000 rpm for 2 minutes to obtain a copper slurry. The copper slurry was evenly applied to the surface of a 99.9999% silicon wafer using a 75-micron scraper. The wafer was then calcined at 650°C in a nitrogen atmosphere for 2 hours and cooled to obtain a silicon wafer and copper electrode structure.

[0087] The sheet resistance of the copper electrode was measured to be 24.3 microohms using a four-probe resistance meter. After four weeks in air, the sheet resistance was 56.5 microohms. The copper paste adhesion of the copper electrode was measured using the tape method using 3M 610 tape, with the number of grids without copper adhesion being 100.

[0088] Table 3

[0089]

[0090] As shown in Table 3, the present invention's method for preparing glass-coated copper powder, copper paste, and copper electrodes can produce copper electrodes with low sheet resistance and strong resistance to conductivity decay. Even after four weeks of storage, the increase in sheet resistance is minimal. Furthermore, compared to the hydrogel sol method, the copper paste prepared by the present invention exhibits strong adhesion to the substrate, making it less likely for the copper paste to fall off the copper electrode.

Claims

1. A method for preparing glass-coated copper powder, characterized in that: The method comprises the following steps: Adding a silicon-containing precursor, a boron-containing precursor and an inorganic zinc salt into an organic solvent, mixing and dissolving them, and obtaining a zinc borosilicate glass sol solution, wherein the boron-containing precursor is an alkyl borate; adding copper powder to the zinc borosilicate glass sol solution and mixing, and then purging the volatile organic solvent with a non-oxidizing gas to obtain zinc borosilicate gel-coated copper powder; calcining the zinc borosilicate gel-coated copper powder at 200-600° C. for 3-6 hours, and cooling to obtain zinc borosilicate glass-coated copper powder; Wherein, no additional water is added during the preparation process, and the calcination is a staged calcination.

2. The method for preparing glass-coated copper powder according to claim 1, wherein: The boiling points of the silicon-containing precursor and the boron-containing precursor are both higher than 165°C.

3. The method for preparing glass-coated copper powder according to claim 2, wherein: The silicon-containing precursor is tetraethyl orthosilicate and / or orthosilicic acid, and the alkyl borate is one or more of tripropyl borate, tributyl borate, dibutyl borate, monopentyl borate, and dipentyl borate.

4. The method for preparing glass-coated copper powder according to claim 1, wherein: The inorganic zinc salt is an inorganic zinc salt soluble in an alcohol organic solvent or an alcohol ether organic solvent.

5. The method for preparing glass-coated copper powder according to claim 4, wherein: The inorganic zinc salt is zinc nitrate hexahydrate.

6. The method for preparing glass-coated copper powder according to claim 1, wherein: The organic solvent is an alcohol or alcohol ether organic solvent with a boiling point higher than 110°C.

7. The method for preparing glass-coated copper powder according to claim 1, wherein: The molar percentages of the silicon-containing precursor, the boron-containing precursor and the inorganic zinc salt in the total molar number of the three are in the range of 1-15%, 25-60% and 35-60% respectively.

8. The method for preparing glass-coated copper powder according to claim 1, wherein: The particle size of the copper powder is 0.2-10 microns, and the mass of the copper powder is 4-99 times the total mass of the silicon precursor, the boron precursor and the inorganic zinc salt.

9. The method for preparing glass-coated copper powder according to claim 1, wherein: The zinc borosilicate gel-coated copper powder is calcined at 200-600° C. for 3-6 hours, comprising: In a non-oxidizing gas atmosphere, the zinc borosilicate gel-coated copper powder is calcined at 200-300° C. for 1-2 hours, and then calcined at 450-600° C. for 2-4 hours.

10. A method for preparing glass-coated copper paste, characterized in that: The method comprises the following steps: The glass-coated copper powder prepared by any method of claims 1-9 is mixed with an organic polymer and an organic solvent to prepare a glass-coated copper slurry, wherein the mass percentages of the glass-coated copper powder, the organic polymer and the organic solvent are 60-90%, 1-5% and 9-35% respectively.

11. A method for preparing a copper electrode, characterized in that: The method comprises the following steps: The glass-coated copper paste prepared by the method of claim 10 is coated on a substrate and calcined at 600-800° C. for 1-4 hours in a non-oxidizing gas atmosphere to form a copper electrode, wherein the substrate is made of one of ceramic, glass, silicon or metal.

12. A glass-coated copper powder, characterized in that: The glass-coated copper powder is prepared by any one of the methods of claims 1-9.

13. A glass-coated copper powder as claimed in claim 12, characterized in that: The mass ratio of glass in the glass-coated copper powder is 10-15%.

14. A glass-coated copper paste, characterized in that: The glass-coated copper paste is prepared by the method according to claim 10.

15. A copper electrode, characterized in that: The copper electrode is prepared by the method according to claim 11.

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