Etching copper powder and preparation method thereof, composite conductive powder, conductive slurry and preparation and application thereof

Abstract

The invention discloses etching copper powder and a preparation method thereof, composite conductive powder, conductive paste and application. The etched copper powder is prepared from spherical copper powder through controllable chemical etching, the ratio of the specific surface area of the etched copper powder to the original copper powder is larger than or equal to 1.2, and the surface of the etched copper powder is provided with a nanoscale defect structure. The etching copper powder is compounded with a small amount of silver-copper alloy powder to form composite conductive powder, and the content of the etching copper powder is larger than 50 wt%. On the basis, low-temperature curing resin or high-temperature glass powder is selected as a binding phase, and the copper-based conductive paste suitable for a heterojunction cell low-temperature curing process and a TOPCon cell high-temperature sintering process can be prepared respectively. The conductive activity and oxidation resistance of the copper powder are effectively improved through etching, the synergistic effect of the alloy powder is combined, the use amount of precious metal is remarkably reduced, meanwhile, the obtained electrode has high conductivity, strong adhesive force and excellent environmental stability, and a key cost-reducing material solution is provided for efficient photovoltaic cells.

Description

Technical Field

[0001] This invention relates to the field of nanomaterials technology, specifically to an etched copper powder and its preparation method, a composite conductive powder, a conductive paste, and their preparation and application. Background Technology

[0002] Crystalline silicon solar cells are the mainstream technology in the photovoltaic industry, among which heterojunction (HJT) and tunnel oxide passivated contact (TOPCon) cells have become key development directions due to their high conversion efficiency. However, these two cell structures place drastically different and stringent requirements on the electrode paste: For high-temperature junction thermoelectric (HJT) cells, which employ low-temperature (<200℃) deposition of amorphous silicon thin films, the electrodes must be fabricated at low temperatures (typically <250℃) to achieve good ohmic contact and conductivity. Currently, low-temperature curing silver paste is commonly used, but the high cost of silver powder severely restricts the cost reduction of HJT cells. If ordinary copper powder is used directly, its smooth surface and low activity make it difficult to form an effective conductive network at low temperatures, and the oxides on the surface of copper powder cannot be reduced at low temperatures, resulting in extremely high electrode resistivity, which fails to meet the application requirements.

[0003] For TOPCon batteries, the back electrode needs to penetrate the ultra-thin tunneling oxide layer and form a strong ohmic contact with the polycrystalline silicon layer during high-temperature (>750℃) sintering process. Traditional high-temperature silver paste has good performance but is expensive. Ordinary copper paste is easily oxidized at high temperatures, has insufficient sintering activity, and is difficult to achieve effective interface corrosion and contact formation, often leading to increased contact resistance and decreased parallel resistance, which in turn causes battery efficiency degradation.

[0004] In existing technologies, to reduce the amount of silver used, some studies have attempted to directly incorporate copper powder into the slurry or to perform simple surface coating treatment on the copper powder. However, these methods have failed to fundamentally resolve the core contradiction between the poor connectivity of copper powder at low temperatures and its susceptibility to oxidation and low sintering activity at high temperatures. Summary of the Invention

[0005] This invention addresses the fundamental shortcomings of existing technologies where copper powder is directly used in photovoltaic cell electrodes—difficulty in forming effective conductive connections at low temperatures and easy oxidation and insufficient sintering activity at high temperatures—aiming to provide a novel copper-based conductive material system. Specific objectives include: providing an etchable copper powder with high specific surface area, high surface activity, and excellent intrinsic oxidation resistance; providing a controllable and repeatable preparation method for this etchable copper powder; providing a high-performance composite conductive powder composed of the aforementioned etchable copper powder as the core and a small amount of alloy powder; and based on this composite conductive powder, providing two copper-based conductive pastes suitable for low-temperature curing of HJT cells and high-temperature sintering processes of TOPCon cells, respectively; fundamentally solving the cost, performance, and reliability challenges of copper paste in photovoltaic applications, and providing a key material solution for cost reduction and efficiency improvement in high-efficiency crystalline silicon cells.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides an etching copper powder, which is obtained by controlled surface etching of spherical copper powder, wherein the ratio of the specific surface area of ​​the etching copper powder to the specific surface area of ​​the spherical copper powder before etching is ≥1.2. Preferably, the sphericity of the spherical copper powder is ≥0.9, and the particle size distribution span is ≤0.6, to ensure the uniformity of the raw material and the uniformity of the etching effect.

[0007] Secondly, the present invention provides a method for preparing the above-mentioned etching copper powder. The method includes the following steps: Spherical copper powder is dispersed in an etching solution containing an etchant, and a chemical etching reaction is carried out at a temperature of 10-60°C. After the reaction is completed, the copper powder is separated, washed, and dried to obtain the etched copper powder. To achieve controllable etching and obtain an ideal surface structure, the key process parameters are limited to: the concentration of the etchant in the etching solution is 0.01-1 mol / L, the liquid-to-solid ratio of the etching solution to the spherical copper powder is (3-10) mL:1g, and the chemical etching reaction time is 20-120 minutes. The etchant is a compound that can promote the oxidative dissolution or complexation dissolution of the copper powder, preferably one or more of ammonium persulfate, hydrogen peroxide, dilute nitric acid, acetic acid, or ethylenediaminetetraacetic acid.

[0008] Thirdly, the present invention provides a composite conductive powder.

[0009] The composite conductive powder comprises silver-copper alloy powder and the aforementioned etching copper powder, wherein the content of etching copper powder is greater than 50 wt% based on the total weight of the composite conductive powder. This composite powder combines the high activity of the etching copper powder with the synergistic reinforcing effect of the silver-copper alloy powder. Preferably, the silver content in the silver-copper alloy powder is 10-50 at.%. More preferably, based on the total weight of the composite conductive powder, it comprises 90-99.9 wt% etching copper powder and 0.1-10 wt% of the aforementioned silver-copper alloy powder.

[0010] Fourthly, the present invention provides two conductive slurries based on the above-mentioned composite conductive powder.

[0011] Both conductive slurries suitable for heterojunction (HJT) and tunnel oxide passivated contact (TOPCon) batteries contain a binder phase, an organic carrier, and the aforementioned composite conductive powder, wherein the total content of the composite conductive powder is ≥70 wt% by weight of the slurry. The difference lies in the binder phase system: Low-temperature curing slurry: The binder phase is a low-temperature curing resin (such as epoxy resin or phenolic resin), suitable for HJT battery processes. Its typical formulation contains, by weight: 75-90% composite conductive powder, 1-8% low-temperature curing resin, and 9-20% organic carrier.

[0012] High-temperature sintering slurry: The binder phase is glass powder (such as Bi2O3-B2O3-ZnO system, PbO-B2O3-SiO2 system or lead-free phosphate system), suitable for TOPCon battery process. Its typical formulation contains, by weight: 70-92% composite conductive powder, 1-5% glass powder and 7-25% organic carrier.

[0013] The organic carrier can be selected from high-boiling-point solvents, such as terpineol, butyl carbitol, and Texanol™ (trimethylpentanediol monoisobutyrate); or low-boiling-point solvents, such as acetone, butyl acetate, and turpentine. The choice of solvent must be compatible with the slurry system (low-temperature curing or high-temperature sintering) and subsequent processes (curing or sintering temperature). The organic carrier further contains organic solvents and necessary additives, including dispersants. The dispersant is used to ensure uniform and stable dispersion of the conductive powder and can be a polyester-type or polyurethane-type polymeric dispersant (number-average molecular weight approximately 5,000-20,000), or a phosphate ester surfactant. Its addition amount is typically 0.5-2.0 wt% of the total mass of the conductive powder.

[0014] Fifthly, the present invention provides a general preparation method for the above-mentioned conductive slurry, which involves mixing composite conductive powder, binder phase and organic carrier, and then dispersing and rolling to obtain a uniform slurry.

[0015] Sixthly, the present invention provides the application of the above-mentioned conductive paste in the preparation of photovoltaic cell electrodes, particularly for the preparation of back electrodes for heterojunction (HJT) cells or TOPCon cells. When applied to the preparation of back electrodes for heterojunction (HJT) cells, the paste is printed onto the HJT cell and then cured at 200-220°C for 15 minutes; when applied to the back electrodes for TOPCon cells, the paste is printed and then rapidly sintered at a peak temperature of 780-820°C.

[0016] Compared with the prior art, the technical solution provided by the present invention has the following significant advantages: This invention utilizes controlled chemical etching of copper powder to create nanoscale pits, pores, or stepped defect structures in situ on the surface of spherical copper powder. These structures significantly increase the specific surface area (specific surface area ratio ≥ 1.2), providing more active sites and contact interfaces. Simultaneously, during etching, some copper ions are redeposited on the surface or form a dense passivation layer with anions in the etchant (such as sulfate, nitrate, EDTA coordination groups, etc.). This layer effectively inhibits further oxidation of the copper powder during subsequent processing and use. This composite structure of "defect + passivation" enhances both conductivity and environmental stability, giving the etched copper powder both high surface activity and excellent intrinsic oxidation resistance, fundamentally overcoming the inherent shortcomings of ordinary copper powder.

[0017] A composite conductive powder composed of etched copper powder and a small amount of silver-copper alloy powder promotes close contact during low-temperature curing due to the etched structure; during high-temperature sintering, the alloying elements segregate to inhibit oxidation and promote ohmic contact. Based on the same core composite powder, by simply changing the binder phase system (resin / glass powder), pastes suitable for two completely different processes—HJT low-temperature curing and TOPCon high-temperature sintering—can be derived, demonstrating high technical versatility and greatly expanding the application range. The prepared conductive paste has good printability, and the electrodes formed after curing / sintering exhibit high density, strong adhesion, and low resistivity. Furthermore, the conductive paste uses inexpensive copper as the main material and a low amount of precious silver, significantly reducing the overall cost compared to pure silver paste. Attached Figure Description

[0018] Figure 1 Electron micrograph of the original copper powder; Figure 2 Electron micrograph of etched copper powder; Figure 3 For comparison of cross-sectional SEM images of the slurries prepared in Comparative Example 1(a) and Example 1(b) after sintering. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to embodiments. The following embodiments are for illustrative purposes only and should not be considered as limitations on the present invention.

[0020] Unless otherwise stated, the materials used in the preparation examples, embodiments, application examples, and tests of this invention are as follows: Spherical copper powder (purchased from Jiyuan Xinghan New Material Technology Co., Ltd.): purity ≥99.5%, average particle size D50 0.5-5.0μm (preferably 3.0μm), sphericity ≥0.9, particle size distribution span Span ≤0.6, specific surface area 0.5-1.5m². 2 / g.

[0021] Copper etching agents: ammonium persulfate (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., AR, ≥98%), dilute nitric acid (purchased from Suzhou Jiading Chemical Technology Co., Ltd.), ethylenediaminetetraacetic acid (purchased from Shanghai Maclean Biochemical Technology Co., Ltd., reagent grade, 99.5%), etc., all of which are analytical grade or higher purity.

[0022] Silver-copper alloy powder: prepared by liquid-phase chemical reduction method, with Ag content of 10-50 at.% and average particle size of 20-100 nm, and has an Ag-Cu solid solution structure.

[0023] Resin: The low-temperature curing resin is epoxy resin or phenolic resin, and its epoxy value / hydroxyl value and other parameters meet the standards of conventional electronic grade resin.

[0024] Glass powder: Bi2O3-B2O3-ZnO, PbO-B2O3-SiO2 or lead-free phosphate system, with a softening point range of 400-600℃.

[0025] Organic carrier solvents: terpineol (purchased from Shanghai Maclean Biochemical Technology Co., Ltd., reagent grade, 99.5%), butyl acetate (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., AR, ≥99%), butyl carbitol (purchased from Shanghai Maclean Biochemical Technology Co., Ltd., ≥99%), etc., with purity ≥99% and water content <0.5%. Other additives: dispersant (purchased from BYK Chemical, DISPERBYK-102), leveling agent (purchased from BYK Chemical, DISPERBYK-333), etc., are commonly used products in the field of electronic materials.

[0026] Preparation of silver-copper alloy powder Nano-silver-copper alloy powder was prepared by liquid-phase chemical reduction.

[0027] Preparation Example 1: A mixed aqueous solution of silver nitrate (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., AR, ≥99.8%) and copper nitrate (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., copper nitrate trihydrate) was prepared, controlling the Ag:Cu atomic ratio to be 3:7. Under nitrogen protection, ascorbic acid (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., AR, ≥99%) as a reducing agent and polyvinylpyrrolidone (PVP) (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., average molecular weight 10000, K13-18) as a dispersant were added to the solution, and the mixture was vigorously stirred at 1200 rpm to generate Ag30Cu70 nano-alloy particles. After the reaction was completed, the particles were centrifuged, washed, and dried to obtain nano-silver-copper alloy powder with an average particle size of approximately 50 nm.

[0028] Preparation Example 2: A mixed aqueous solution of silver nitrate and copper nitrate was prepared, with an atomic ratio of Ag:Cu of 2:8. Under a protective atmosphere, ascorbic acid (a reducing agent) and polyvinylpyrrolidone (PVP) (a dispersant) were added to the solution, and the mixture was vigorously stirred at 1200 rpm to generate Ag20Cu80 nano-alloy particles. After the reaction was completed, the particles were centrifuged, washed, and dried to obtain nano-silver-copper alloy powder with an average particle size of approximately 50 nm.

[0029] Etching copper powder and its preparation Example 1

[0030] 100 g of spherical copper powder with an average particle size of 3.0 μm, sphericity ≥ 0.9, and particle size distribution span ≤ 0.6 was weighed and dispersed in 500 mL of 0.1 mol / L ammonium persulfate aqueous solution. The mixture was mechanically stirred in a 30℃ constant temperature water bath for 60 minutes to carry out a chemical etching reaction. After the reaction, the spherical copper powder was separated, washed three times with deionized water by centrifugation, and dried in a 60℃ vacuum drying oven for 6 hours to obtain etched copper powder. BET specific surface area testing showed that the specific surface area of ​​the original spherical copper powder was 0.8 m². 2 / g, the specific surface area of ​​the etched copper powder is 1.2m². 2 / g, specific surface area ratio is 1.5. (Refer to...) Figure 1 and Figure 2 Before etching, the copper powder particles are spherical and have a smooth surface. After etching, a distinct micro-etched structure is formed on the surface of the copper powder. Example 2

[0031] 100 g of the same spherical copper powder as in Example 1 was weighed and dispersed in 500 mL of a 0.05 mol / L dilute nitric acid solution. The solution was mechanically stirred in a 30°C water bath for 40 minutes. Post-treatment was the same as in Example 1 to obtain etched copper powder. Specific surface area testing showed that the specific surface area of ​​the etched copper powder was 1.1 m². 2 / g, with a specific surface area ratio of 1.38. Example 3

[0032] 100 g of spherical copper powder, identical to that in Example 1, was weighed and dispersed in 500 mL of a 0.2 mol / L EDTA aqueous solution. The solution was mechanically stirred in a 50°C water bath for 90 minutes. Post-treatment was the same as in Example 1 to obtain etched copper powder. Specific surface area testing showed that the specific surface area of ​​the etched copper powder was 1.05 m². 2 / g, with a specific surface area ratio of 1.31.

[0033] Conductive paste and its preparation Application Examples 1-3: Application Examples 1-3 all involve a low-temperature curing conductive paste for HJT batteries and its preparation. Raw materials were weighed according to the formula in Table 1. The composite conductive powder, low-temperature curing resin, and organic carrier were mixed, initially dispersed using a planetary mixer, and then rolled three times using a three-roll mill to obtain a uniform and fine low-temperature curing conductive paste suitable for HJT batteries.

[0034] Table 1. Formulation of Low-Temperature Curing Conductive Slurry for HJT Batteries

[0035] Low-temperature curing resin was selected as the binder phase, specifically epoxy resin (epoxy value approximately 0.48 eq / 100g, purchased from Hangzhou Wuhuigang Adhesive Co., Ltd., bisphenol A type epoxy resin (E51)); the organic carrier was composed of butyl acetate and dispersant mixed at a weight ratio of 9:1, wherein the dispersant was purchased from BYK Chemical, DISPERBYK-102.

[0036] Compare and contrast with example 1-2: Comparative Application Examples 1-2 are based on Application Example 1. In Comparative Application Example 1, an equal amount of unetched raw copper powder is used to replace the composite conductive powder, and in Comparative Application Example 2, an equal amount of unetched raw copper powder is used to replace the etched copper powder.

[0037] Application Example 4-6: Application Examples 4-6 all involve a high-temperature curing conductive paste for TOPcon batteries and its preparation. Raw materials were weighed according to the formula in Table 2. The composite conductive powder, glass powder, and organic carrier were mixed, initially dispersed using a planetary mixer, and then rolled three times using a three-roll mill to obtain a uniform and fine high-temperature curing conductive paste suitable for TOPcon batteries.

[0038] Table 2. Formulation of TOPcon battery high-temperature curing conductive paste

[0039] The bismuth-based lead-free glass powder has the following composition: Bi2O3 65wt%, B2O3 20wt%, ZnO 10wt%, SiO2 5wt%; softening point is about 480℃; average particle size D50 is about 1.5μm.

[0040] Compare and contrast with example 3-4: Comparative Application Examples 3-4 are all based on Application Example 4. In Comparative Application Example 3, an equal amount of unetched raw copper powder is used to replace the composite conductive powder, and in Comparative Application Example 4, an equal amount of unetched raw copper powder is used to replace the etched copper powder.

[0041] Performance Tests and Results To objectively evaluate the technical effects of the present invention, resistivity testing, wet weight detection, HJT cell photoelectric conversion efficiency testing, TOPcon cell photoelectric conversion efficiency testing, and bare cell DH experiment were performed on the battery cell samples obtained in the embodiments and comparative examples, as detailed below: (1) Electrode volume resistivity test: Conductive paste was printed and cured / sintered on HJT / TOPcon solar cells (oxygen content controlled at 2000ppm in nitrogen sintering furnace, baked at 120℃ for 2min; peak temperature of HJT solar cells was 210℃ for 15min; peak temperature of TOPcon solar cells was 800℃ for 20min) to form a strip-shaped conductive film with uniform thickness and consistent width (thickness approximately 12μm, width approximately 1mm). The average thickness (t) and average width (w) of the conductive film cross-section were measured using a scanning electron microscope (SEM). Using a four-probe resistance meter (Keithley 2400 series source meter), four equally spaced metal probes were pressed against the surface of the conductive film along its length. A constant current (I) was applied to the two outer probes, and the voltage drop (V) between the two inner probes was measured. Sheet resistance was calculated using the formula (Rs = (π / ln2) × (V / I)), and then converted to volume resistivity (Ω·cm) using the formula (ρ = Rs × t × (W / s), where s is the probe spacing). Five different locations were measured on each conductive film, and three films were measured on each sample. The final result was the average value.

[0042] (2) Wet weight test of the auxiliary material The weight change of a single cell before and after printing was detected using the differential method. For HJT cell paste, the wet weight of the auxiliary grid electrode was measured; for TOPCon cell paste, the wet weight of the back seed layer and the single back conductive layer were measured respectively. Five cells were measured consecutively for each paste, and the average value was taken.

[0043] (3) Photovoltaic conversion efficiency test of HJT solar cells Using a high-precision screen printing machine (from Maiwei), the paste was printed at a speed of 400 mm / s (325 mesh screen, squeegee pressure 0.4-0.6 MPa) onto the specified grid pattern on the back of a standard HJT solar cell. The cell was then placed in a chain sintering furnace and cured at a peak temperature of 210°C for 15 minutes to form electrodes. The cured cell was then placed on a test platform with the temperature controlled at 25°C. An AAA-grade solar simulator (spectral AM 1.5G, irradiance 1000 W / m²) was used. 2 The entire surface of the solar cell was uniformly irradiated. A digital source meter (SMU) was connected to the positive and negative terminals of the cell. Under simulated illumination, a voltage scan was performed from short-circuit voltage to open-circuit current, with current measured simultaneously to plot a complete current-voltage (IV) curve. The maximum power point (Pmax = Imax × Vmax) was found on the IV curve. The efficiency was calculated using the formula: photoelectric conversion efficiency η = Pmax / (incident irradiance × total cell area) × 100%. Twenty cells were prepared for each slurry, and the efficiency was measured separately. The arithmetic mean was taken as the reported value.

[0044] (4) TOPCon cell photoelectric conversion efficiency test Using a high-precision screen printing machine (from Maiwei), the paste was printed onto the back grid lines of a standard TOPCon cell at a printing speed of 500 mm / s (screen mesh count 325, squeegee pressure 0.4-0.6 MPa). The cells were then placed in a rapid sintering furnace and sintered at a peak temperature of 800°C. The efficiency measurement procedure was exactly the same as the HJT cell efficiency measurement described above (standard test conditions: 25°C, AM 1.5G, 1000 W / m). 2 Twenty solar cells were prepared using each type of slurry, and the average efficiency was taken.

[0045] (5) Die storage stability test The initial photoelectric conversion efficiency (EPC) of the printed and cured / sintered solar cells (without module encapsulation, i.e., "bare cells") was measured under standard test conditions and denoted as η0. The cells were then placed in a dry, light-protected experimental environment at room temperature (25°C). The cells were left in this environment for 30 days (720 hours). The cells were then removed, and their EPC was measured again under standard test conditions and denoted as ηt. The efficiency degradation rate was calculated as Δη = (η0 - ηt) / η0 × 100%. A lower degradation rate indicates better environmental reliability of the electrodes.

[0046] The test results are recorded in Tables 3-1 and 3-2. Table 3-1. Performance Test Results (Part 1)

[0047] Table 3. Performance Test Results (Part Two)

[0048] The data in the table above shows that: The electrode resistivity of Comparative Examples 1 and 3 (pure, unetched copper powder) was extremely high, demonstrating that unmodified copper powder, due to its smooth surface, low activity, and susceptibility to oxidation, cannot be directly used as an effective conductive phase. In stark contrast, all examples employing surface-etched copper powder showed a 2-3 order of magnitude reduction in resistivity. This directly proves that controlled chemical etching is the decisive step in imparting conductive activity to copper powder, enabling its use in high-performance pastes.

[0049] Furthermore, in Examples 1-3 (HJT system) and Examples 4-6 (TOPCon system), significant results were achieved using different etchants (such as ammonium persulfate, dilute nitric acid, and EDTA), demonstrating that the method of the present invention has good compatibility with different types of etchants. Among them, the copper powder etched with ammonium persulfate (Examples 1 and 4) exhibited the best overall performance (such as the lowest resistivity and the highest conversion efficiency) in their respective systems, providing a clear direction for the optimal selection of etchants in specific application scenarios.

[0050] This invention lies not only in the use of etched copper powder alone, but also in the synergistic effect produced by its combination with trace amounts of silver-copper alloy powder. Comparing Comparative Example 2 (unetched copper powder + alloy powder) and Example 1 (etched copper powder + alloy powder), it is evident that while the resistivity and efficiency of the former are improved compared to pure copper powder, they are still significantly inferior to the latter. This indicates that a synergistic effect beyond simple physical mixing occurs between the nano-silver-copper alloy powder and the etched copper powder, which possesses a high specific surface area and active surface. This synergistic effect is also significant in the high-temperature TOPCon system (Comparative Example 4 vs. Example 4), jointly promoting effective ohmic contact formation and oxidation protection during sintering.

[0051] This invention, based on a copper powder slurry, achieved conversion efficiencies of 24.1%-24.5% in HJT cells and 25.5%-25.9% in TOPCon cells, both significantly better than the corresponding unetched comparative examples, reaching or approaching commercial levels. The same core composite conductive powder, by simply adjusting the binder phase (low-temperature resin or high-temperature glass powder), can be adapted to the low-temperature curing process of HJT and the high-temperature sintering process of TOPCon, demonstrating the high versatility and strong adaptability of the technical solution. After 30 days of storage at room temperature, the efficiency decay rate of all embodiments was ≤0.05%, far lower than the alloy-containing but unetched comparative example (≥0.09%), proving that the special structure formed on the copper powder surface by the etching process endows it with excellent intrinsic oxidation resistance and long-term environmental stability. The printing wet weight data of all embodiments were stable and comparable to the comparative examples, indicating that the slurry of this invention has good rheological properties and printability, and is easy to achieve stable production on existing production lines.

[0052] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A copper etching powder, characterized in that: It is made by surface etching of spherical copper powder, wherein the ratio of the specific surface area of ​​the etched copper powder to the specific surface area of ​​the spherical copper powder is ≥1.

2.

2. The etching copper powder according to claim 1, characterized in that: The spherical copper powder has a sphericity ≥ 0.9 and a particle size distribution span value Span ≤ 0.

6.

3. The method for preparing the etching copper powder according to claim 1 or 2, characterized in that, Includes the following steps: The spherical copper powder is dispersed in an etching solution and subjected to a chemical etching reaction at a temperature of 10-60°C. After the reaction is completed, the copper powder is separated, washed, and dried to obtain the etched copper powder. The etching solution contains an etchant with a concentration of 0.01-1 mol / L, the liquid-to-solid ratio of the etching solution to the spherical copper powder is (3-10) mL:1 g, and the chemical etching reaction time is 20-120 minutes.

4. The preparation method according to claim 3, characterized in that: The surface etching is performed in an etching solution containing at least one copper etchant.

5. The preparation method according to claim 4, characterized in that: The copper etching agent is selected from one or more of ammonium persulfate, hydrogen peroxide, dilute nitric acid, acetic acid, or ethylenediaminetetraacetic acid.

6. A composite conductive powder, characterized in that: It comprises silver-copper alloy powder and etching copper powder as described in claim 1 or 2; the content of etching copper powder is >50 wt% based on the total weight of the composite conductive powder.

7. The composite conductive powder according to claim 6, characterized in that: The composite conductive powder contains 90-99.9 wt% etching copper powder and 0.1-10 wt% of the silver-copper alloy powder, based on the total weight of the powder.

8. A conductive paste, characterized in that: It comprises a binder phase, an organic carrier, and the composite conductive powder as described in claim 6 or 7; the binder phase is a low-temperature curing resin or glass powder, and the content of the composite conductive powder is ≥70% based on the total weight of the conductive slurry.

9. The method for preparing the conductive paste according to claim 8, characterized in that: The composite conductive powder, binder phase and organic carrier are mixed, dispersed and rolled to obtain a uniform slurry.

10. The application of the conductive paste according to claim 8 in the preparation of photovoltaic cell electrodes.

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