Silver-coated copper powder, and preparation method and application thereof

Abstract

This invention belongs to the field of conductive materials technology, specifically relating to a silver-coated copper powder, its preparation method, and its application. A method for preparing silver-coated copper powder includes the following steps: S1, pretreating copper powder to obtain pretreated copper powder; S2, mixing the pretreated copper powder, reducing agent, additive, and solvent to obtain a copper powder mixture; the additive is dihydrogen phosphate and / or hydrogen phosphate; S3, mixing silver salt, complex, and solvent to obtain a silver complex solution; S4, mixing the copper powder mixture and the silver complex solution, reacting to obtain a silver-coated copper powder precursor; S5, post-treating the silver-coated copper powder precursor to obtain silver-coated copper powder. The addition of dihydrogen phosphate and / or hydrogen phosphate to the silver-containing reaction solution in this invention can lower the pH value of the copper powder mixture, improve the surface condition of the copper powder, and thus reduce the resistivity of the silver-coated copper powder.

Description

Technical Field

[0001] This invention belongs to the field of conductive materials technology, specifically relating to a silver-coated copper powder, its preparation method, and its application. Background Technology

[0002] Photovoltaic cells are one of the main forms of renewable energy power generation. In the manufacturing of photovoltaic cells, traditional silver paste uses pure silver, which is particularly expensive for heterojunction (HJT) cells that require double-sided silver coating. To reduce the cost of HJT cells, the photovoltaic industry has begun using silver-coated copper instead of pure silver powder as a raw material in photovoltaic cell manufacturing.

[0003] Silver-coated copper powder is a composite material consisting of a copper core encased in a silver coating. The copper core allows the silver-coated copper powder to retain the excellent electrical and thermal conductivity of copper, while the silver coating enhances the copper's oxidation resistance and thermal stability, making it more durable and reliable. Replacing silver powder with silver-coated copper powder can effectively reduce material costs.

[0004] Currently, the main methods for preparing silver-coated copper powder for photovoltaic cells include substitution method, chemical reduction method, and combination of substitution and chemical deposition. However, the performance of silver-coated copper powder prepared by these methods has not yet reached that of pure silver powder. In particular, the conductivity of silver-coated copper powder is lower than that of pure silver, which affects the photoelectric conversion efficiency of HJT cells. Summary of the Invention

[0005] To reduce the resistance of silver-coated copper powder, this application provides a silver-coated copper powder, its preparation method, and its application.

[0006] In a first aspect, this application provides a method for preparing silver-coated copper powder, which is achieved by the following technical solution:

[0007] A method for preparing silver-coated copper powder, the method comprising the following steps:

[0008] S1. Pre-treat the copper powder to obtain pre-treated copper powder;

[0009] S2. Mix the pretreated copper powder, reducing agent, additive and solvent described in step S1 to obtain copper powder mixture; the additive is dihydrogen phosphate and / or hydrogen phosphate.

[0010] S3. Mix the silver salt, complex, and solvent to obtain a silver complex solution;

[0011] S4. Mix the copper powder mixture from step S2 and the silver complex solution from step S3 to react and obtain the silver-coated copper powder precursor.

[0012] S5. Post-process the silver-coated copper powder precursor described in step S4 to obtain silver-coated copper powder.

[0013] In this invention, the copper powder used as the starting material is not limited. The conductive powder suitable for low-temperature conductive slurry is generally in the micrometer range, such as 0.1-50 micrometers, preferably 0.5-10 micrometers. The copper powder can be spherical, flake-shaped, or irregularly shaped.

[0014] Copper powder is easily oxidized in air, forming oxides on its surface. In this invention, in step S1, the pretreatment uses a dilute sulfuric acid aqueous solution to remove oxides and impurities from the surface of the copper powder. Pretreatment of the copper powder can reduce the oxygen content of the silver-coated copper powder.

[0015] The present invention demonstrates through experiments that adding dihydrogen phosphate and / or hydrogen phosphate to a copper powder mixture reduces the resistivity of silver-coated copper powder.

[0016] In this invention, in step S5, the post-processing uses a surfactant containing oleophilic groups to treat the silver-coated copper powder precursor, which can change the surface properties of the silver-coated copper powder precursor from hydrophilic to oleophilic to hydrophobic, so that the silver-coated copper powder and the organic solvent in the conductive paste are fully mixed to obtain a uniform and fluid conductive paste, thereby improving the conductivity of the conductive paste.

[0017] In this invention, the surfactant containing lipophilic groups is a fatty acid and / or a fatty acid salt.

[0018] Preferably, in step S2, the mass ratio of the pretreated copper powder, reducing agent, additive and solvent is 1:(0.15-0.5):(0.01-0.5):(2-50).

[0019] Preferably, the mass ratio of the pretreated copper powder, reducing agent, additive and solvent is 1:(0.15-0.25):(0.3-0.5):(8-12).

[0020] In this invention, the dihydrogen phosphate salt includes, but is not limited to, sodium dihydrogen phosphate and potassium dihydrogen phosphate.

[0021] In this invention, the hydrogen phosphate salt includes, but is not limited to, disodium hydrogen phosphate and dipotassium hydrogen phosphate.

[0022] Preferably, the additive is a dihydrogen phosphate.

[0023] Preferably, the mass ratio of the pretreated copper powder, reducing agent, dihydrogen phosphate and solvent is 1:0.2:0.4:10.

[0024] Preferably, in step S2, the reducing agent is selected from one or more of hydrazine hydrate, hydroxylamine sulfate, formaldehyde, dimethylborane, glucose, sucrose, fructose, tartaric acid, sulfinic acid, thiocarboxylic acid, or ascorbic acid.

[0025] More preferably, the reducing agent is ascorbic acid.

[0026] Preferably, in step S3, the complex is selected from one or more of ethylenediamine, ammonia, citrate, tartrate, ethylenediaminetetraacetate, diethylenetriamine, triethylenetetraamine, tetraethylenepentamine, polyethylenepolyamine, N,N'-dibenzylethylenediamine diacetate and its esters, and N,N,N',N'-tetra(2-hydroxypropyl)ethylenediamine.

[0027] More preferably, the complex is ethylenediaminetetraacetic acid salt.

[0028] In this invention, the ethylenediaminetetraacetic acid salt includes, but is not limited to, any one of ethylenediaminetetraacetic acid tetrasodium, ethylenediaminetetraacetic acid disodium, ethylenediaminetetraacetic acid tetrapotassium, or ethylenediaminetetraacetic acid dipotassium.

[0029] Preferably, in step S3, the mass ratio of the silver salt, the complex, and the solvent is 1:(2.5-3.5):(25-40).

[0030] Secondly, this application provides a silver-coated copper powder, implemented using the following technical solution:

[0031] A silver-coated copper powder, wherein the silver-coated copper powder is prepared by the above-described preparation method.

[0032] Thirdly, this application provides an application of silver-coated copper powder, implemented using the following technical solution:

[0033] An application of silver-coated copper powder, wherein the silver-coated copper powder is used to produce silver-coated copper conductive paste.

[0034] In summary, the present invention has the following beneficial effects:

[0035] The addition of dihydrogen phosphate and / or hydrogen phosphate to the copper powder mixture of this invention can reduce the pH value of the copper powder mixture, reduce impurities on the copper surface of the silver-coated copper powder during the reaction process, and reduce the resistance of the silver-coated copper powder. This achieves a significant reduction in cost while improving the conductivity of the low-temperature curing conductive paste. Attached Figure Description

[0036] Figure 1 This is a SEM image of the silver-coated copper powder prepared in Example 1 of the present invention. Detailed Implementation

[0037] The present application will be further described in detail below with reference to the embodiments.

[0038] Example

[0039] Example 1 provides a silver-coated copper powder, the preparation steps of which are as follows:

[0040] S1. Take 100g of copper powder (product code 6B, average particle size of 3.7 micrometers, typical oxygen content of 0.39wt%) produced by Dowa Holdings (Group) Co., Ltd. of Japan, and place it in 500mL of 2wt% dilute sulfuric acid aqueous solution. Sonicate and stir for 15min to remove oxides and other impurities on the surface of the copper powder. Filter and wash twice with deionized water until pH neutral, so that the typical oxygen content is reduced to below 0.1wt%, and obtain pretreated copper powder.

[0041] S2. Take the pretreated copper powder obtained in step S1 and mix it with 15g ascorbic acid, 30g sodium dihydrogen phosphate and 800 mL deionized water. Stir for 10 minutes to obtain copper powder mixture.

[0042] S3. Take 28.4 g of silver nitrate and mix it with 700 mL of deionized water. Dissolve it completely to obtain a silver salt solution. Then add 70.9 g of tetrasodium ethylenediaminetetraacetate and mix it completely to obtain a silver complex solution.

[0043] S4. At a stirring rate of 300 rpm, the silver complex solution obtained in step S3 is added dropwise to the copper powder mixture obtained in step S2 at a rate of 50 mL / min, and the mixture is stirred at a stirring rate of 300 rpm for 30 min. After the silver complex solution has been completely added, the reaction is continued to be stirred for 10 min to precipitate. Then the supernatant is discarded and the mixture is washed 4 times with deionized water until the pH is neutral to obtain the silver-coated copper powder precursor.

[0044] S5. Take 5.3g of stearic acid, dissolve it in 300mL of ethanol, add it to the silver-coated copper powder precursor obtained in step S4, stir, filter, wash with ethanol 5 times, and vacuum dry in an oven at 70℃ for 6h to obtain silver-coated copper powder.

[0045] Example 2 provides a silver-coated copper powder, which differs from Example 1 only in that the preparation step S2 is as follows: take the pretreated copper powder obtained in step S1, and mix it with 25g ascorbic acid, 50g sodium dihydrogen phosphate and 1200mL deionized water, and stir for 10min to obtain a copper powder mixture.

[0046] Example 3 provides a silver-coated copper powder, which differs from Example 1 only in that the preparation step S2 is as follows: take the pretreated copper powder obtained in step S1, and mix it with 20g ascorbic acid, 50g sodium dihydrogen phosphate and 1000mL deionized water, and stir for 10min to obtain a copper powder mixture.

[0047] Example 4 provides a silver-coated copper powder, which differs from Example 3 only in that sodium dihydrogen phosphate is replaced by disodium hydrogen phosphate in equal quantities.

[0048] Example 5 provides a silver-coated copper powder, which differs from Example 3 only in that an equal mass of sodium dihydrogen phosphate is replaced with a mixture of sodium dihydrogen phosphate and disodium hydrogen phosphate, with a mass ratio of sodium dihydrogen phosphate to disodium hydrogen phosphate of 1:1.

[0049] Example 6 provides a silver-coated copper powder, which differs from Example 3 only in that the mass of sodium dihydrogen phosphate is 40g.

[0050] Example 7 provides a silver-coated copper powder, which differs from Example 6 only in that ascorbic acid and other substances are replaced by glucose.

[0051] Comparative Example

[0052] Comparative Example 1 provides a silver-coated copper powder, which differs from Example 1 only in that the mass of sodium dihydrogen phosphate in the copper powder mixture is replaced with deionized water.

[0053] Comparative Example 2 provides a silver-coated copper powder, which differs from Example 1 only in that sodium dihydrogen phosphate is replaced by sodium phosphate in equal quantities.

[0054] Comparative Example 3 provides a silver-coated copper powder, which differs from Example 1 only in that sodium dihydrogen phosphate is replaced by acetic acid by mass.

[0055] Performance testing

[0056] Conductivity tests were conducted on the silver-coated copper powders provided in Examples 1-7 and Comparative Examples 1-3. The test steps were as follows: First, a low-temperature conductive paste was prepared using the silver-coated copper powder (6.5g of bisphenol A epoxy resin NPEL-128, 2.8g of triethylenetetramine, 4.0g of butylcarbamate, 0.2g of BYK110 dispersant, and 87g of silver-coated copper powder were weighed, and the above raw materials were mixed at high speed and rolled into a fineness of less than 8μm using a three-roll mill to obtain low-temperature conductive pastes). The paste was printed on an alumina substrate in a serpentine pattern, dried at 100°C for 1 hour, and then cured at 250°C for 20 minutes. After curing, the resistance of the serpentine lines was measured, and the test data are shown in Table 1.

[0057] Among them, the bisphenol A epoxy resin NPEL-128 was purchased from Wanqing Chemical Technology Co., Ltd.; the BYK110 dispersant was purchased from BYK in Germany.

[0058] Table 1 Test data of Examples 1-7 and Comparative Example 1

[0059] sample Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Comparative Example 1 Comparative Example 2 Comparative Example 3 Resistance (mΩ / square) 4.6 4.3 4.2 4.5 4.3 4.0 4.1 6.2 6.5 5.4

[0060] The following details this application based on the test data in Table 1.

[0061] Comparing the experimental results of Example 1 with those of Comparative Examples 1-3, it can be seen that the addition of dihydrogen phosphate and / or hydrogen phosphate to the copper powder mixture of the present invention reduces the resistance of silver-coated copper powder.

[0062] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing silver-coated copper powder, characterized in that, The preparation method includes the following steps: S1. Pre-treat the copper powder to obtain pre-treated copper powder; S2. Mix the pretreated copper powder, reducing agent, additive and solvent described in step S1 to obtain copper powder mixture; the additive is dihydrogen phosphate and / or hydrogen phosphate. S3. Mix the silver salt, complex, and solvent to obtain a silver complex solution; S4. Mix the copper powder mixture from step S2 and the silver complex solution from step S3 to react and obtain the silver-coated copper powder precursor. S5. Post-process the silver-coated copper powder precursor obtained in step S4 to obtain silver-coated copper powder; in step S2, the mass ratio of the pre-treated copper powder, reducing agent, additive and solvent is 1:(0.15-0.5):(0.01-0.5):(2-50); in step S3, the mass ratio of the silver salt, complex and solvent is 1:(2.5-3.5):(25-40).

2. The method for preparing silver-coated copper powder according to claim 1, characterized in that, The mass ratio of the pretreated copper powder, reducing agent, additive and solvent is 1:(0.15-0.25):(0.3-0.5):(8-12).

3. The method for preparing silver-coated copper powder according to claim 2, characterized in that, The additive is dihydrogen phosphate; the mass ratio of the pretreated copper powder, reducing agent, dihydrogen phosphate and solvent is 1:0.2:0.4:

10.

4. The method for preparing silver-coated copper powder according to claim 1, characterized in that, In step S2, the reducing agent is selected from one or more of the following: hydrazine hydrate, hydroxylamine sulfate, formaldehyde, dimethylborane, glucose, sucrose, fructose, tartaric acid, sulfinic acid, thiocarboxylic acid, or ascorbic acid.

5. The method for preparing silver-coated copper powder according to claim 1, characterized in that, In step S3, the complex is selected from one or more of ethylenediamine, ammonia, citrate, tartrate, ethylenediaminetetraacetic acid, diethylenetriamine, triethylenetetraamine, tetraethylenepentamine, polyethylenepolyamine, N,N'-dibenzylethylenediamine diacetic acid and its esters, and N,N,N',N'-tetra(2-hydroxypropyl)ethylenediamine.

6. A method for preparing silver-coated copper powder according to any one of claims 1-5, characterized in that, The silver content of the silver-coated copper powder is 5-40 wt%.

7. A silver-coated copper powder, characterized in that, The silver-coated copper powder is prepared by the preparation method according to any one of claims 1-6.

8. An application of the silver-coated copper powder as described in claim 7, characterized in that, The silver-coated copper powder is used to produce silver-coated copper conductive paste.

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