High oxidation resistance heterojunction silver-clad copper paste

Abstract

The invention discloses a highly antioxidant heterojunction silver-coated copper slurry and a preparation process thereof, comprising a carrier, the highly antioxidant silver-coated copper powder, spherical silver powder, an antioxidant, and a welding aid; the mass percentage of the highly antioxidant silver-coated copper powder is 30% to 92%, the mass percentage of the spherical silver powder is 0% to 50%, the antioxidant is added in an amount of 20 ppm to 500 ppm, the welding aid is added in an amount of 0.1% to 0.5%; and the balance is the carrier.

Description

Technical Field

[0001] The invention relates to the technical field of solar photovoltaic technology, and in particular to a highly oxidation-resistant heterojunction silver-clad copper slurry. Background Art

[0002] Against the backdrop of carbon peak and carbon neutrality, photovoltaic power generation as a clean energy has attracted people's attention. Among them, heterojunction solar cells have developed rapidly due to their outstanding advantages. The cell sheets of heterojunction cells can be made thinner, improving the utilization efficiency of crystalline silicon; from the perspective of energy consumption, the curing temperature of heterojunction silver paste is low and can be cured within 150-200°C; from the perspective of performance, heterojunction cells will not produce polarization phenomenon, have high light stability, and have a higher opening voltage, so heterojunction cells have higher photoelectric conversion efficiency.

[0003] Heterojunction solar cells are double-sided power generation cells. During the production process, silver paste is printed on both the front and back sides, and a large amount of silver paste is used. In addition, since heterojunction cells use low-temperature curing silver paste, the bulk resistivity of the paste is higher than that of high-temperature sintering silver paste. In order to achieve the same conductivity, during the production of heterojunction cells, a grid line silver paste with a thickness of 1000 nm is required to be printed.

[0004] The cost of silver paste in the production of heterojunction solar cells has remained high. Using silver-coated copper to replace silver powder to make paste can effectively reduce the production cost of heterojunction solar cells. Traditional silver-coated copper paste has a higher resistivity than pure silver paste, resulting in a lower conversion rate than pure silver paste; there is also the problem of poor battery reliability due to oxidation of exposed copper due to incomplete coating.

[0005] Therefore, it is necessary to provide a high oxidation resistance heterojunction silver-clad copper paste to solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to provide a high-oxidation-resistant heterojunction silver-clad copper slurry.

[0007] One of the technical solutions is as follows:

[0008] A highly antioxidant heterojunction silver-coated copper slurry comprises a carrier, the highly antioxidant silver-coated copper powder, spherical silver powder, an antioxidant, and a welding aid. The mass percentage of the highly antioxidant silver-coated copper powder is 30% to 92%, the mass percentage of the spherical silver powder is 0% to 50%, the antioxidant is added in an amount of 20 ppm to 500 ppm, and the welding aid is added in an amount of 0.1% to 0.5%; the balance is the carrier.

[0009] Furthermore, the carrier is composed of epoxy resin, solvent, epoxy curing agent, blocked isocyanate curing agent, and epoxy diluent. In terms of mass percentage, the epoxy resin is 1% to 10%, the epoxy curing agent is 0.1% to 3%, the blocked isocyanate curing agent is 1% to 5%, the epoxy diluent is 0.1% to 5%, and the solvent is the balance.

[0010] Furthermore, the high antioxidant silver-coated copper powder preferably has a D50 of 1.0 to 5.0 μm, and more preferably a D50 of 1.5 to 4.0 μm. If the particle size is too large, the prepared slurry will have problems with poor printing under the screen. If the particle size is too small, the slurry viscosity will be too high, and the slurry printing ink return effect will be poor. The addition amount of the high antioxidant silver-coated copper powder is preferably 30% to 92%, and more preferably 30% to 60%. Too much addition will result in excessive resistivity after the slurry is cured. If the addition amount is too little, the cost reduction will be small.

[0011] Furthermore, the amount of silver powder added is preferably 10% to 50%, more preferably 30% to 50%. If the amount added is too little, the resistivity of the slurry will be too high, and if the amount added is too much, the slurry cost will not be significantly reduced. The silver powder is preferably spherical silver powder, which is conducive to printing finer lines. The particle size of the selected silver powder is preferably D50 of 1.0 to 5.0 μm, more preferably 1.0 to 3.0 μm. The tap density of the selected silver powder is preferably 4.0 to 6.5 g / cm 3 , more preferably 5.5 to 6.2 g / cm 3 The specific surface area of ​​the selected silver powder is preferably 0.35 to 0.6 m 2 / g; more preferably 0.4 to 0.6 m 2 / g.

[0012] Furthermore, the antioxidant is preferably a nitrogen heterocyclic compound, such as benzotriazole, benzimidazole, 2-mercaptobenzimidazole, benzothiazole, mercaptobenzothiazole, 2-mercaptopyridine, and 2-hydroxypyridine; the amount of antioxidant added is preferably 20ppm to 500ppm, more preferably 20ppm to 300ppm. If the amount added is too much, the resistivity will increase. If the amount added is too little, the slurry will have insufficient antioxidant properties.

[0013] Furthermore, the welding aid is selected from small molecule alcohols, polyols, polyol esters and ether alcohol structures with a boiling point of 250-500°C; at 150-200°C, hydroxyl groups can effectively remove silver oxide on the surface of silver powder, thereby forming a weld between silver and silver particles, and after heating for a long time, such substances will evaporate, reducing the barriers between the silver interfaces and further promoting the weld between silver particles; substances with similar structures include: ethylene glycol, polyethylene glycol 200, polyethylene glycol 400, and 1,2,3-propylene glycol.

[0014] Furthermore, the epoxy resin type can be one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, aliphatic epoxy resin, polyester modified epoxy, polyurethane modified epoxy, acrylic modified epoxy; the solvent is an ester solvent, an alcohol solvent, an ether solvent, a ketone solvent with a boiling point between 190°C and 250°C, such as terpineol, butyl carbitol, butyl carbitol acetate, diethylene glycol dibutyl ether, dimethyl glutarate, dimethyl adipate, ethylene glycol butyl ether acetate, diacetone alcohol, isophorone; the epoxy curing agent is selected from phthalate, silane coupling agent, dicyandiamide, modified dicyandiamide, imidazole, modified One or more of imidazole, acid anhydride, boron trifluoride monoethylamine, amino resin, and cation; the epoxy diluent is a glycidyl ester or glycidyl ether type, such as ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, allyl glycidyl ether, resorcinol diglycidyl ether, octyl glycidyl ether, 2-toluene glycidyl ether, neopentyl glycol diglycidyl ether, polypropylene glycol diglycidyl ether, phenyl glycidyl ether, 1,4-cyclohexanedimethanol glycidyl ether, cyclohexane-1,2-diglycidyl ester, glycidyl methacrylate, glycidyl butyrate, and 4,5-epoxytetrahydrophthalic acid diglycidyl ester.

[0015] Furthermore, antioxidant silver-coated copper powder and spherical silver powder are dispersed in a carrier to obtain antioxidant heterojunction silver-coated copper paste; specifically, epoxy resin, solvent, epoxy curing agent, epoxy diluent, blocked isocyanate curing agent and antioxidant are mixed and dispersed to obtain a carrier, and then the above-mentioned antioxidant silver-coated copper powder and spherical silver powder are added and then centrifuged, three-roll milled and dispersed, and filtered to remove impurities to obtain antioxidant heterojunction silver-coated copper paste, which can be directly used for printing heterojunction solar cell electrodes after viscosity adjustment.

[0016] The second technical solution is:

[0017] A process for preparing a highly oxidation-resistant heterojunction silver-clad copper slurry comprises the following steps:

[0018] 1) Take silver-coated copper powder, which is obtained by liquid phase heat treatment of ordinary spherical or quasi-spherical silver-coated copper powder. The silver coating amount is 10% to 50%, and the particle size of the silver-coated copper powder is 1.5μm to 5μm;

[0019] 2) Firstly crush and disperse the spherical silver-coated copper powder with a particle size of 1.5 to 5 μm;

[0020] 3) Fully disperse the silver-coated powder in an organic solution with a boiling point > 200°C, heat to above 180°C under nitrogen protection, and stir for more than 2 hours;

[0021] 4) Separate the powder and wash it with ethanol;

[0022] 5) Adsorption of fatty acid protective agents;

[0023] 6) Low temperature drying at 50-70℃;

[0024] 7) The mixture is crushed and dispersed to obtain silver-coated copper powder with high oxidation resistance.

[0025] Furthermore, in step 2), the pulverizing and dispersing is performed by pulverizing the powder using a high-speed pulverizer with a rotation speed of >10000 r / min for more than 30 seconds; or the pulverizing and dispersing is performed by pulverizing the powder using a jet mill at an air inlet pressure of 0.5 MPa.

[0026] Furthermore, during the liquid phase heat treatment process in step 3), the powder is fully dispersed in the liquid phase, effectively preventing the phenomenon of powder agglomeration caused by the heat treatment process. The above treatment process is carried out in a nitrogen atmosphere, thereby preventing the silver-coated copper powder from oxidizing in the air. After the silver-coated copper powder undergoes liquid phase heat treatment, a transition layer of alloy structure is formed between the copper and the surface-coated silver, thereby improving the contact strength and density of the silver and copper. In addition, after the heat treatment, the defects and holes originally existing in the silver-coated copper powder will be recrystallized at high temperature and repaired, thereby improving the oxidation resistance of the silver-coated copper powder.

[0027] Furthermore, after cleaning, a layer of fatty acid protective agent is coated on the surface of the powder. The carboxyl group of the fatty acid will form chemical adsorption with the surface of the silver-coated copper powder, and the adsorption layer can further enhance the antioxidant properties of the silver-coated copper powder. After cleaning, a layer of fatty acid protective agent is coated on the surface of the powder to prevent the silver-coated copper powder from agglomerating during the drying process, thereby ensuring that the silver-coated copper powder has better dispersion.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1) After liquid phase heat treatment, the interface contact between the silver layer and the copper powder particles is made closer. Moreover, after heating treatment, the defects of the silver-coated copper powder are recrystallized and repaired, which improves the density of the surface of the silver-coated copper powder particles and thus improves the oxidation resistance of the silver-coated copper.

[0030] 2) Heterocyclic antioxidants with strong adsorption capacity on metal interfaces are added. These substances will form a dense chemical adsorption layer with the metal interface, thereby effectively preventing the oxidation of the metal interface. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is the slurry impedance test printed graphics.

[0032] Figure 2 It is silver-coated copper powder S3501 before liquid phase heat treatment.

[0033] Figure 3It is silver-coated copper powder C-4 after liquid phase heat treatment.

[0034] Figure 4 This is an electron microscope image of the "Example 4" formulation without a welding aid after baking.

[0035] Figure 5 This is an electron microscope image taken after baking the welding aid formula "Example 5".

[0036] Figure 6 This is a table of preparation parameters for silver-clad copper.

[0037] Figure 7 This is the specification table of silver-clad copper powder.

[0038] Figure 8 is the ratio of carrier A.

[0039] Figure 9 This is the raw material list of vector A.

[0040] Figure 10 This is one of the ingredient comparison tables.

[0041] Figure 11 This is the second printed record sheet.

[0042] Figure 12 This is the second ingredient comparison table.

[0043] Figure 13 This is the second printed record sheet. DETAILED DESCRIPTION

[0044] A method for preparing silver-coated copper oxide silver powder comprises the following steps: crushing and dispersing the silver-coated copper powder, and using a liquid phase heat treatment method to form the silver-coated copper powder into a more compact surface with fewer defects; and

[0045] Step 1: The purchased silver-coated copper powder is crushed and dispersed using an airflow crushing device or an airflow mill. Dry nitrogen is used in the process to prevent the powder from absorbing moisture and agglomerating, which results in poor crushing and dispersion of the powder inside the agglomerates. The air pressure is 0.05-0.5 MPa. If the air pressure is too low, the impact force between the powders is insufficient and there is no obvious crushing effect. If the air pressure is too high, the powder will break, resulting in changes in particle size.

[0046] Step 2: Disperse 500g of crushed and dispersed silver-coated copper powder in 1000g~5000g of ethylene glycol, stir for 0.5~2h, and then heat to 150~200℃ in nitrogen and continue stirring for 0.5~4h; if the amount of dispersion medium is too small, the powder cannot be fully dispersed in the medium, resulting in agglomeration during heat treatment; if the heat treatment time is not enough, the surface density of the silver-coated copper is insufficient, resulting in insignificant improvement in oxidation resistance.

[0047] Step 3: After the above heat-treated silver-coated copper powder is allowed to settle, the bottom powder is separated and washed with ethanol 1 to 3 times; 0.5 to 5 g of dodecanoic acid is dissolved in 10 to 50 g of ethanol, and the dodecanoic acid solution is added to the washed silver-coated copper powder. The mixture is stirred and dispersed in a stirring disperser for 15 to 120 minutes to ensure that the surface of the silver-coated copper powder is fully coated with dodecanoic acid.

[0048] Step 4: Dry the silver-coated copper paste coated with lauric acid at 40-70°C. Excessively high temperatures can cause oxidation and agglomeration of the powder. The dried silver-coated copper powder is then pulverized and dispersed for use in slurry preparation.

[0049] The following silver-coated copper powders were prepared according to the above method. The preparation parameters are as follows: Figure 6 The parameters of the silver-coated copper powder are as follows: Figure 7 The specifications of the silver-coated copper powder are shown in the table. The electron microscope image of the original silver-coated copper powder is shown in the table. Figure 2 As shown; the electron microscope image of the silver-coated copper powder C-4 after heat treatment is as follows Figure 3 shown.

[0050] in:

[0051] The preparation of the carrier is also included: weighing 15 to 30 parts of epoxy resin, 10 to 25 parts of isocyanate curing agent, 5 to 10 parts of epoxy diluent, 1 to 5 parts of epoxy curing agent, 0.1 to 0.5 parts of antioxidant, 5 to 15 parts of welding aid, and 30 to 45 parts of solvent, and then using a centrifugal disperser for centrifugal dispersion, the centrifugal speed is 1000 r / min, the centrifugal dispersion time is 3 minutes, and the carrier A is obtained; according to the above carrier preparation method, a reference Figure 8 Several groups of carriers shown, raw materials used to prepare the carriers Figure 9 As shown:

[0052] The method also includes the preparation of silver paste: taking 8 parts of carrier A, adding 46 parts of silver-coated copper powder, stirring evenly, then adding 46 parts of spherical silver powder, stirring evenly to obtain a slurry, and then centrifugally dispersing the slurry with a centrifugal disperser at a centrifugal speed of 1200 r / min and a centrifugal time of 2 minutes. After the centrifugal dispersion of the slurry is completed, the slurry is further ground and dispersed using an Eckart three-roll grinder, and the ground silver paste is filtered using a mesh of 400 mesh or more to remove impurities to obtain a finished silver paste.

[0053] To test:

[0054] 1) Particle size test: Use Malvern 3000 laser particle size analyzer for measurement. The measuring medium is deionized water. The sample size is 30 mg. Add 0.025 g Tween-80 and 10 g ethanol and ultrasonically disperse for 5 minutes. Once the particle size analyzer is ready, pour the ultrasonically dispersed sample into the analyzer for testing. After the measurement, the D50 average value can be directly read.

[0055] 2) High-temperature heat loss test: Take a 3-5g sample, calcine it in a muffle furnace at 750℃ for 15 minutes, cool it to room temperature, weigh it and calculate the weight loss. The result is divided by the sample size to obtain the high-temperature heat loss, which is expressed as a percentage. Multiple parallel measurements are required, and the average is taken.

[0056] 3) Specific surface area: The specific surface area was measured using an automatic surface analyzer from Micromeritics, USA, in accordance with the standard "GB / T19587-2017 Determination of the specific surface area of ​​solid substances by the gas adsorption BET method". The average value was taken after multiple measurements.

[0057] 4) Tap density test: Use a tap density meter to measure the density 2000 times and take the average value after multiple measurements.

[0058] 5) Viscosity test: Use an Anton Paar rheometer to measure at 25°C. The data measured at 10 inverse seconds is the required viscosity value. The viscosity of the silver paste should be controlled between 80,000 cp and 130,000 cp. If the viscosity of the silver paste is too low, the silver paste printing will easily cause diffusion problems. If the viscosity of the silver paste is too high, the silver paste will block the screen and prevent good printing.

[0059] 6) Resistivity test: Print the silver paste into Figure 1 The pattern shown in the figure was baked at 180℃ for 30 minutes, then taken out and the thickness of the 30μm wide line was tested using a KEYENCE 3D laser scanner. The resistance of the 30μm wide line was measured using a resistance meter or milliohm meter. The line length was 10cm, and then the resistivity of the silver paste was calculated according to the resistivity calculation formula.

[0060]

[0061] ρ: resistivity of 30μ line, unit: Ωcm;

[0062] S: The average cross-sectional area of ​​the measured 30μm line, in μm 2

[0063] R: the average value of the measured thin wire resistance, unit Ω;

[0064] L: The measured length of the thin wire is a constant value of 10 cm.

[0065] 7) Ring test: Place the substrate sample printed with silver paste in an 85%HR / 85℃ ring tester for 500 hours of ring test. Then take it out and measure the resistivity increase of 30μm wide lines, expressed as a percentage.

[0066] 8) High and low temperature cycle test: Place the substrate sample printed with silver paste in a -40℃ / 85℃ high and low temperature cycle tester and perform 200 high and low temperature cycle tests. After the test, measure the resistivity increase of 30μm wide lines and express it as a percentage. Example 1

[0067] 8.0 g of carrier A-0 was added to 46.0 g of heat-treated silver-coated copper powder C-1 and 46.0 g of spherical silver powder FE-88312-K. After stirring and mixing, the mixture was centrifuged at 1200 rpm for 1 min, and then dispersed using an Eckart three-roll mill. Finally, the mixture was filtered through a 500-mesh steel wire filter to remove impurities, thereby obtaining a slurry of Example 1. Figure 10 shown.

[0068] The viscosity of the silver-coated copper paste was measured by Anton Paar rheometer at 10 inverse seconds. Then, a 360 mesh, 15 μm thick latex film and 21 Newton tension steel screen was used for printing to produce specific patterns such as Figure 1 After that, bake it at 200℃ for 10 minutes, then use a resistance meter to measure the resistance of the specific line, use a Keyence 3D microscope to measure the cross-sectional area of ​​the line, and then calculate the corresponding resistivity. Example 2

[0069] Take 8.0g of carrier A-0, add 46.0g of heat-treated silver-coated copper powder C-2 and 46.0g of spherical silver powder FE-88312-K, and prepare the slurry according to the above slurry preparation method; the measurement items and methods are the same as in Example 1. Example 3

[0070] Take 8.0g of carrier A-0, add 46.0g of heat-treated silver-coated copper powder C-3 and 46.0g of spherical silver powder FE-88312-K, and prepare the slurry according to the above slurry preparation method; the measurement items and methods are the same as in Example 1. Example 4

[0071] Take 8.0g of carrier A-0, add 46.0g of heat-treated silver-coated copper powder C-4, 46.0g of spherical silver powder FE-88312-K, and prepare the slurry according to the above slurry preparation method; the measurement items and methods are the same as those in Example 1. The electron microscope image of the silver paste prepared in Example 4 after printing into lines and drying is as follows Figure 4 .

[0072] Comparative Example 1

[0073] Take 8.0g of carrier A-0, add 46.0g of original silver-coated copper powder S-3501 and 46.0g of spherical silver powder FE-88312-K, and prepare the slurry according to the above slurry preparation method; the measurement items and methods are the same as in Example 1.

[0074] Comparative Example 2

[0075] Take 8.0g of carrier A-0, add 46.0g of heat-treated silver-coated copper powder C-5 and 46.0g of spherical silver powder FE-88312-K, and prepare the slurry according to the above slurry preparation method; the measurement items and methods are the same as in Example 1.

[0076] See Figure 2 、 Figure 3 , it can be seen from the comparison between the two that after heat treatment, the surface of the silver-coated copper powder is obviously smoother and denser; comparing the specific surface areas of C-1 to C-4 and S-3501, the specific surface area of ​​the silver-coated copper powder decreases after heat treatment, which also shows that the silver-coated copper powder shows fewer defects and improved density after heat treatment; because the A-0 carrier does not add welding aids, the slurry does not produce welding, so the resistivity is relatively large, such as Figure 4 As shown in the figure, by comparing the resistance change rate of the 30μm line after the ring test for 500H and the temperature cycle for 200H, it can be seen that the resistance stability of the slurry prepared by the heat-treated silver-coated copper powder is significantly improved, indicating that the oxidation resistance of the slurry has been improved; the original silver-coated copper powder used in Comparative Example 1 was not crushed and dispersed, and the silver-coated copper powder in Comparative Example 2 was not coated with the protective agent lauric acid after heat treatment. The 15μm open lines of both had poor ink filling problems, and it was impossible to print complete lines without broken grids. Figure 11 Printed record sheet. Example 5

[0077] Take 8.0 g of carrier A-1, add 46.0 g of heat-treated silver-coated copper powder C-4 and 46.0 g of spherical silver powder FE-88312-K, and prepare the slurry according to the above slurry preparation method; the measurement items and methods are the same as in Example 1. Example 6

[0078] Take 8.0 g of carrier A-2, add 46.0 g of heat-treated silver-coated copper powder C-4 and 46.0 g of spherical silver powder FE-88312-K, and prepare the slurry according to the above slurry preparation method; the measurement items and methods are the same as in Example 1. Example 7

[0079] Take 8.0g of carrier A-3, add 46.0g of heat-treated silver-coated copper powder C-4 and 46.0g of spherical silver powder FE-88312-K, and prepare the slurry according to the above slurry preparation method; the measurement items and methods are the same as in Example 1.

[0080] Comparative Example 3

[0081] Take 8.0 g of carrier A-2, add 92.0 g of spherical silver powder FE-88312-K, and prepare the slurry according to the above slurry preparation method; the measurement items and methods are the same as in Example 1.

[0082] Comparative Example 4

[0083] Take 8.0g of carrier A-2, add 92.0g of unheat-treated silver-coated copper original powder S-3501, and prepare the slurry according to the above slurry preparation method; the measurement items and methods are the same as in Example 1.

[0084] Comparative Example 5

[0085] Take 8.0 g of carrier A-2, add 60.0 g of heat-treated silver-coated copper powder C-4 and 32.0 g of spherical silver powder FE-88312-K, and prepare the slurry according to the above slurry preparation method; the measurement items and methods are the same as in Example 1.

[0086] See Figure 12 、 13 The resistivity of Example 5 is significantly lower than that of Example 4. The reason is that after adding the welding aid, low-temperature welding occurs during the slurry baking process. Figure 4 The following is a scanning electron microscope image of the slurry film layer after drying in Example 4. There is no fusion welding between the powders. Figure 5 The scanning electron microscope image of the slurry film layer after drying in Example 5 is shown. Significant welding occurs between the powders, and adhesion channels are formed between the powders, thereby effectively improving the conductive effect and improving the oxidation resistance. After 500 hours of ring testing and 200 hours of temperature cycling, the resistance change rate of the 30μ line is significantly reduced. Comparing Example 5, Example 6, and Example 7, it is found that after further adding an antioxidant, the resistance change rate of the line after 500 hours of ring testing and 200 hours of temperature cycling is further reduced, reaching the level of a pure silver formula, as shown in Comparative Example 3. This shows that the antioxidant further improves the oxidation resistance of the slurry, thereby preventing the increase of resistance. However, if the addition amount is too much, the resistivity of the slurry will be too high, as shown in Example 7. If the formula directly uses the unheated silver-coated copper powder S-3501, the slurry resistivity is large and the oxidation resistance is not satisfactory, as shown in Comparative Example 4. If the amount of heat-treated silver-coated copper powder used in the slurry is increased, the oxidation resistance can be satisfied, but the resistivity of the slurry is too high.

[0087] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the inventive concept of the present invention, which all fall within the scope of protection of the present invention.

Claims

1. A highly oxidation-resistant heterojunction silver-clad copper paste, characterized by: The invention comprises a carrier, high-antioxidation silver-coated copper powder, spherical silver powder, an antioxidant, and a welding aid; the mass percentage of the high-antioxidation silver-coated copper powder is 30% to 92%, the mass percentage of the spherical silver powder is 10% to 50%, the added amount of the antioxidant is 20ppm to 500ppm, the added amount of the welding aid is 0.1% to 0.5%; the balance is the carrier; The highly antioxidant silver-coated copper powder is prepared by the following method: Spherical silver-coated copper powder with a particle size of 1.5 to 5 μm is first crushed and dispersed; Disperse the silver-coated powder fully in an organic solution with a boiling point > 200°C, heat to above 180°C under nitrogen protection, and stir for more than 2 hours; The powder was separated and washed with ethanol; Adsorption of fatty acid protective agents; Dry at low temperature of 50-70℃; Then the powder is crushed and dispersed to obtain highly antioxidant silver-coated copper powder; The antioxidant is a nitrogen heterocyclic compound, and the added amount of the antioxidant is 20ppm to 500ppm.

2. The highly oxidation-resistant heterojunction silver-clad copper paste according to claim 1, characterized in that: The carrier is composed of epoxy resin, solvent, epoxy curing agent, blocked isocyanate curing agent and epoxy diluent. The percentage by mass is 1% to 10% of epoxy resin, 0.1% to 3% of epoxy curing agent, 1% to 5% of blocked isocyanate curing agent, 0.1% to 5% of epoxy diluent, and the solvent is the balance.

3. The highly oxidation-resistant heterojunction silver-clad copper slurry according to claim 2, characterized in that: The D50 of high oxidation resistance silver-coated copper powder is 1.0~5.0μm.

4. The highly oxidation-resistant heterojunction silver-clad copper slurry according to claim 3, characterized in that The selected silver powder particle size D50 is 1.0-5.0 μm; the selected silver powder tap density is 4.0-6.5 g / cm 3 ; The specific surface area of ​​the selected silver powder is 0.35~0.6m 2 / g.

5. The highly oxidation-resistant heterojunction silver-clad copper paste according to claim 4, characterized in that: The welding auxiliary agent is selected from polyols, polyol esters and alcohol ether compounds with a boiling point of 250-500°C.

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