A low-temperature conductive paste for metal plate printing and its preparation method

Abstract

This invention discloses a low-temperature conductive paste for metal plate printing and its preparation method. The raw materials for preparing the low-temperature conductive paste include the following components in parts by weight: 68-83 parts conductive metal powder, 10-20 parts nanoparticles, 2-10 parts resin composite, and 1-3 parts additives. This invention achieves this by fully dispersing the nanoparticles in an organic system, adjusting the types and proportions of each component in the additives to improve the dispersion stability of the nanoparticles, pre-curing the nanoparticle-resin mixture at a certain temperature, and finally adding the conductive metal powder. The paste is then ground and filtered to produce a low-temperature conductive paste for metal plate printing. This paste is suitable for high-speed printing with metal screens, improves the thixotropic properties of the paste, ensures stable printing over long periods, and suppresses problems such as reduced mixing degree, unstable viscosity, poor printability, and large wet weight fluctuations during long-term continuous printing. Furthermore, it produces fine printed lines with excellent aspect ratio, while reducing wet weight and improving efficiency.

Description

Technical Field

[0001] This invention belongs to the field of conductive paste technology, specifically relating to a low-temperature conductive paste for metal plate printing and its preparation method. Background Technology

[0002] The manufacturing process of heterojunction solar cells is relatively simple, with only four core steps: cleaning and texturing, amorphous silicon thin film deposition, TCO film deposition, and metal electrode polarization. This helps improve production yield and reduces labor and maintenance costs. Heterojunction solar cells have good light stability, no PID and LID effects, and low degradation rate. The theoretical efficiency of heterojunction solar cells can reach 28.5%, with the highest recorded conversion efficiency of silicon heterojunction solar cells reaching 26.81%. Heterojunction solar cells are more suitable for stacking with perovskite solar cells, with greater potential for efficiency improvement. However, the current actual production line efficiency is around 25.5%, which is far from the theoretical value and laboratory records, leaving considerable room for improvement. With the full-scale mass production of Topcon and the gradual rise of BC solar cells, the actual production line efficiency of heterojunction solar cells has not shown a significant advantage over other technologies, resulting in a low market share and making it difficult for heterojunction solar cells to become a mainstream solar cell technology.

[0003] The mass production of heterojunction solar cells primarily utilizes screen printing for metallization. However, limitations stem from the conductivity mechanism of the paste, the organic system, and the powder itself. Low-temperature pastes are difficult to print on narrow-linewidth screens, resulting in high wet weight. Although the mass production of low-silver-content pastes such as silver-coated copper has significantly reduced metallization costs in the past two years, the wet weight remains high, necessitating further optimization of the heterojunction solar cell's profile and aspect ratio.

[0004] Metal mesh printing, with its fully open design and grooved using lasers and other methods, allows for narrower linewidths, resulting in narrower grid lines and reduced silver paste usage. Compared to traditional screen printing, fully open metal mesh printing can save approximately 20% of paste. The printed grid lines are highly uniform and flat, with a smoother surface compared to traditional screen printing, thus reducing grid resistance and increasing the battery's fill factor (FF). A higher fill factor allows the battery to output more stable power in applications, further improving overall performance. This is of great significance for cost reduction and efficiency improvement in heterojunction battery technology.

[0005] However, in practical applications, it has been found that low-temperature silver paste used in screen printing often results in printing quality problems such as grid line defects and nodules when directly applied to metal plates. This is especially true for low-silver content pastes, where the problems are even more severe and they cannot be used directly. Specialized research and development of low-silver content pastes for metal plates with high thixotropy, high plasticity, and high stability is necessary to ensure high-quality printing on metal plates, with grid lines that have good aspect ratios, flatness, good adhesion, and no powdering. Summary of the Invention

[0006] To address the problems in the prior art, the present invention aims to provide a low-temperature conductive paste for metal plate printing and its preparation method.

[0007] To achieve the above objectives and technical effects, the technical solution adopted by this invention is as follows: A low-temperature conductive paste for metal plate printing, wherein the raw materials for preparing the low-temperature conductive paste comprise the following components in parts by weight: 68-83 parts of conductive metal powder 10-20 parts of nano powder 2-10 parts of resin compound Additives 1-3 parts.

[0008] Furthermore, the particle size of the conductive metal powder satisfies the following conditions: D50 = 2.5-4μm, D100 ≤ 8μm, average particle size of 3-5μm, and tap density of not less than 4.5g / cc.

[0009] Furthermore, the conductive metal powder is one or a combination of pure silver powder, pure copper powder, silver-coated copper powder, and alloy powder, and the alloy powder is one or a combination of tin-silver alloy powder, tin-bismuth-silver alloy, and tin-nickel alloy.

[0010] Furthermore, the average particle size of the nanoparticles is 300-500 nm, and the tap density is not less than 3.5 g / cc.

[0011] Furthermore, the nanopowder is one or a combination of several of nano-silver powder, nano-copper powder, and nano-silica.

[0012] Furthermore, the resin composite is prepared by mixing resin, curing agent and solvent in a mass ratio of (40-65):(2-8):(30-60).

[0013] Furthermore, the resin is a thermosetting resin; the curing agent is an imidazole compound; and the solvent is an organic solvent.

[0014] Furthermore, the thermosetting resin is one or a combination of several of epoxy resin, polyester resin, phenolic resin, urea-formaldehyde resin, polybutadiene resin, silicone resin, and acrylic resin; the imidazole compound is one or a combination of several of 1,3-diazacyclopentadiene, 2-methylimidazolium, 2-ethylimidazolium, 2-ethyl-4-methylimidazolium, and 1-cyanoethyl-2-phenylimidazolium; and the organic solvent is one or a combination of several of diethylene glycol butyl ether, diethylene glycol butyl ether acetate, dimethyl adipate, terpineol, divalent ester, butyl acetate, and ethylene glycol ethyl ether acetate.

[0015] Furthermore, the additives include dispersants, antistatic agents, coupling agents, and antioxidants, and the mass ratio is (0.2-1):(0.2-1):(0.2-1):(0.2-1).

[0016] This invention also discloses a method for preparing a low-temperature conductive paste for metal plate printing, comprising the following steps: 1) Preparation of nanopowder resin mixture The resin, curing agent, and solvent are mixed in a mass ratio of (40-65):(2-8):(30-60), and stirred at room temperature for 1-3 hours at a stirring rate of 800-1200 r / min. Then, nanopowder and additives are added, and stirring is continued for 1-3 hours at a stirring rate of 1000-1500 r / min. The mixture is then heated and stirred at 50-70℃ for 10-30 minutes at a stirring rate of 1000-1500 r / min, and cooled to room temperature to obtain a nanopowder resin mixture. 2) Mix the nano-powder resin mixture with conductive metal powder until uniform, grind and filter to obtain the desired low-temperature conductive paste for metal plate printing.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention discloses a low-temperature conductive paste for metal plate printing and its preparation method. The method involves fully dispersing nanoparticles in an organic system, adjusting the types and proportions of each component in the additives to increase the relative value of the zeta potential and improve the dispersion stability of the nanoparticles, pre-curing the nanoparticle-resin mixture at a certain temperature, and finally adding conductive metal powder. The paste is then ground and filtered to produce a low-temperature conductive paste suitable for metal plate printing. This paste is compatible with high-speed printing on metal screens, improves the thixotropic properties of the paste, ensures stable printing over long periods, produces fine lines with excellent aspect ratio, reduces wet weight, and improves efficiency. The nanoparticles themselves can be adjusted... The thixotropic properties of the paste are beneficial to the line shape of the printed grid lines, resulting in a higher aspect ratio. Pre-dispersion of nanoparticles improves the dispersibility and stability of the conductive metal powder, enhancing the stability of the paste during metal plate printing and suppressing problems such as reduced mixing degree, unstable viscosity, poor printability, and large wet weight fluctuations during long-term continuous printing. The efficient dispersion of nanoparticles fills the gaps between conductive metal powders to a certain extent, reducing the volume resistivity and contact resistance of the paste. Pre-curing reduces internal stress in the resin, minimizes internal defects in the cured paste, and improves the uniformity and stability of the resin material, which is beneficial to the conductivity and weather resistance of the cured electrode. Detailed Implementation

[0018] The present invention will now be described in detail so that its advantages and features can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0019] The following provides a brief overview of one or more aspects to offer a basic understanding of them. This overview is not an exhaustive summary of all conceived aspects, nor is it intended to identify key or decisive elements of all aspects, nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form to prepare for the more detailed descriptions that follow.

[0020] On one hand, this invention discloses a low-temperature conductive paste for metal plate printing, the raw materials for which are prepared include the following components in parts by weight: 68-83 parts of conductive metal powder 10-20 parts of nano powder 2-10 parts of resin compound Additives 1-3 parts.

[0021] In some embodiments, the particle size of the conductive metal powder satisfies: D50 = 2.5-4 μm, D100 ≤ 8 μm, average particle size of 3-5 μm, and tap density of not less than 4.5 g / cc.

[0022] The composition of the conductive metal powder is not specifically limited; it can be one or a combination of pure silver powder, pure copper powder, silver-coated copper powder, alloy powder, or other metal powders. The specific silver content of the silver-coated copper powder is not limited, and the alloy powder can be one or a combination of tin-silver alloy powder, tin-bismuth-silver alloy, tin-nickel alloy, etc. The morphology of the conductive metal powder is not specifically limited; it can be flake powder, spherical powder, dendritic powder, or other shapes.

[0023] In some embodiments, the average particle size of the nanoparticles is 300-500 nm, and the tap density is not less than 3.5 g / cc.

[0024] In some embodiments, the composition of the nanopowder is not specifically limited, and it can be one or a combination of several of nano silver powder, nano copper powder, and nano silica.

[0025] In some embodiments, the resin composite is prepared by mixing resin, curing agent, and solvent in a mass ratio of (40-65):(2-8):(30-60). A lower resin content results in poor adhesion to the substrate, while a higher content leads to higher resistance and poor conductivity. The amount of curing agent is adjusted appropriately based on the specific resin and type of curing agent; insufficient or excessive curing agent will prevent complete curing. Insufficient curing agent leads to prolonged curing time and decreased electrical, chemical, and heat resistance properties of the cured resin. Excessive curing agent interferes with the normal curing mechanism of the resin, resulting in the resin adhesive remaining sticky or unevenly cured. Therefore, the actual amounts of resin and curing agent are precisely matched. The solvent is used to dissolve the resin, ensuring uniform distribution of the resin in the slurry, providing a good dispersion environment for conductive metal powder and nanoparticles, and adjusting viscosity and printability.

[0026] In some specific embodiments, the resin used is a thermosetting resin. There are no particular limitations on the thermosetting resin; it can be one or a combination of several selected from epoxy resin, polyester resin, phenolic resin, urea-formaldehyde resin, polybutadiene resin, silicone resin, acrylic resin, etc. Preferably, it is an epoxy resin with a molecular weight preferably between 1000 and 2500, including bisphenol F type epoxy resin, polyphenolic glycidyl ether epoxy resin, aliphatic glycidyl ether epoxy resin, other glycidyl ether epoxy resins, alicyclic epoxy resins, epoxidized olefin epoxy resins, imide epoxy resins, silicone epoxy resins, polyester epoxy resins, etc.

[0027] In some specific embodiments, the curing agent is an imidazole compound; the imidazole compound is one or a combination of several of the following: 1,3-diazacyclopentadiene, 2-methylimidazolium, 2-ethylimidazolium, 2-ethyl-4-methylimidazolium, 1-cyanoethyl-2-phenylimidazolium.

[0028] In some specific embodiments, the solvent is an organic solvent, which is one or a combination of several selected from diethylene glycol butyl ether, diethylene glycol butyl ether acetate, dimethyl adipate, terpineol, divalent ester, butyl acetate, ethylene glycol ethyl ether acetate, etc. The boiling point is preferably 150-350℃.

[0029] In some embodiments, the additives include dispersants, antistatic agents, coupling agents and antioxidants, and the mass ratio is (0.2-1):(0.2-1):(0.2-1):(0.2-1).

[0030] In some specific embodiments, the dispersant is one or a combination of several of the following: sodium dodecylbenzenesulfonate, dodecyl acetic acid, polyester, alkylaryl phosphate, alkylbenzene sulfonate, dialkyl sulfosuccinate, polyoxyethylene alkylphenol ether, sorbitol alkylate, polyethylene glycol, polyethylene, polypropylene, polystyrene, polyacrylate, polyvinyl ester, polyacrylamide, polycarboxylate, poly(methacrylic acid) derivative, maleic anhydride copolymer, sodium polyacrylate, and polyvinyl alcohol.

[0031] In some specific embodiments, the antistatic agent is one or a combination of several of the following: stearyltrimethyl quaternary ammonium hydrochloride, stearamide propyl hydroxyethyl quaternary ammonium nitrate, monofunctional type such as sodium nonylphenoxypropyl sulfonate (NP), polyfunctional type such as alkylbis(α-hydroxyethylamine phosphate), alkyl dicarboxymethyl ammonium acetate, and dodecyl dimethyl quaternary acetate.

[0032] In some specific embodiments, the coupling agent is one or a combination of several of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, 3-glycidyl etheroxypropyltrimethoxysilane, bis(triethanolamine)diisopropyltitanate, and neoalkoxytris(p-aminophenoxy)zirconia ester.

[0033] In some specific embodiments, the antioxidant is one or a combination of several of the following: 2,6-di-tert-butyl-p-cresol, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, N,N'-hexamethylene bis-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxyphenyl)isocyanate, 4-hydroxydodecanoic acid oxyaniline, tris(nonylphenyl) phosphite, and tris(2,4-di-tert-butylphenyl) phosphite.

[0034] On the other hand, the present invention also discloses a method for preparing a low-temperature conductive paste for metal plate printing, comprising the following steps: 1) Preparation of nanopowder resin mixture Resin, curing agent, and solvent are mixed in a mass ratio of (40-65):(2-8):(30-60) and stirred at room temperature for 1-3 hours at a stirring rate of 800-1200 r / min. Then, nanopowder and additives are added, and stirring is continued for 1-3 hours at a stirring rate of 1000-1500 r / min. The mixture is then heated and stirred at 50-70℃ for 10-30 minutes at a stirring rate of 1000-1500 r / min. After cooling to room temperature, a nanopowder resin mixture is obtained. Pre-curing at 50-70℃ can reduce the internal stress of the resin and reduce internal defects in the cured slurry. 2) Mix the nano-powder resin mixture with conductive metal powder until uniform, grind it 3-5 times through a three-roll mill, and filter it through a filter to obtain the low-temperature conductive paste required for metal plate printing.

[0035] Example 1 A low-temperature conductive paste for metal plate printing, the raw materials for which are prepared include the following components in parts by weight: 81 parts of conductive metal powder 13 parts of nano silver powder 9.8 parts of resin composite 1.1 parts of additives.

[0036] The conductive metal powder has an average particle size of 4μm and a tap density of 5g / cc.

[0037] The conductive metal powder includes 65 parts of silver-coated copper powder, 10 parts of pure silver powder, and 6 parts of tin-silver alloy powder.

[0038] The average particle size of the nano silver powder is 500 nm, and the tap density is 4 g / cc.

[0039] The resin composite was prepared by mixing resin, curing agent and solvent in a mass ratio of 50:8:40.

[0040] The resin consists of 1 part phenolic resin, 3 parts bisphenol F type epoxy resin, 0.7 parts organosilicon epoxy resin, and 0.3 parts polybutadiene resin.

[0041] The curing agent used is 0.8 parts of 2-ethyl-4-methylimidazole.

[0042] The solvent used is 3 parts diethylene glycol butyl ether acetate and 1 part dimethyl adipate.

[0043] Additives include dispersants, antistatic agents, coupling agents, and antioxidants.

[0044] The dispersant used is 0.3 parts of sodium dodecylbenzenesulfonate.

[0045] The antistatic agent used is 0.3 parts of alkyl dicarboxymethyl ammonium acetone.

[0046] The coupling agent consists of 0.1 parts of γ-aminopropyltrimethoxysilane and 0.2 parts of bis(triethanolamine)diisopropyltitanate.

[0047] The antioxidant used is 0.2 parts of 1,3,5-tris(3,5-di-tert-butyl-4-hydroxyphenyl) isocyanate.

[0048] A method for preparing a low-temperature conductive paste for metal plate printing includes the following steps: 1) Preparation of nanopowder resin mixture The resin, curing agent and solvent were mixed in a mass ratio of 50:8:40 and stirred at room temperature for 1 hour at a stirring rate of 1200 r / min. Then the nanopowder and additives were added and stirred for another hour at a stirring rate of 1500 r / min. The mixture was then heated and stirred at 70°C for 10 minutes at a stirring rate of 1500 r / min and cooled to room temperature to obtain the nanopowder resin mixture. 2) Mix the nano-powder resin mixture with conductive metal powder until uniform, grind it three times with a three-roll mill, and filter it through a filter to obtain the low-temperature conductive paste required for metal plate printing.

[0049] Example 2 A low-temperature conductive paste for metal plate printing, the raw materials for which are prepared include the following components in parts by weight: 79 parts of conductive metal powder 15 parts of nano silver powder 9.8 parts of resin composite One part of the auxiliary agent.

[0050] The conductive metal powder has an average particle size of 5μm and a tap density of 5g / cc.

[0051] The conductive metal powder consists of 11 parts pure silver powder and 68 parts silver-coated copper powder.

[0052] The average particle size of the nano silver powder is 500 nm, and the tap density is 6 g / cc.

[0053] The resin composite was prepared by mixing resin, curing agent and solvent in a mass ratio of 50:8:40.

[0054] The resin comprises 1 part phenolic resin, 0.7 parts organosilicon epoxy resin, 0.3 parts polybutadiene resin, and 3 parts bisphenol F type epoxy resin.

[0055] The curing agent used is 0.8 parts of 2-ethyl-4-methylimidazole.

[0056] The solvent used is 3 parts diethylene glycol butyl ether acetate and 1 part dimethyl adipate.

[0057] Additives include dispersants, antistatic agents, coupling agents, and antioxidants.

[0058] The dispersant used is 0.2 parts of sodium dodecylbenzenesulfonate.

[0059] The antistatic agent used is 0.3 parts of alkyl dicarboxymethyl ammonium acetone.

[0060] The coupling agent consists of 0.1 parts of γ-aminopropyltrimethoxysilane and 0.2 parts of bis(triethanolamine)diisopropyltitanate.

[0061] The antioxidant used is 0.2 parts of 1,3,5-tris(3,5-di-tert-butyl-4-hydroxyphenyl) isocyanate.

[0062] A method for preparing a low-temperature conductive paste for metal plate printing includes the following steps: 1) Preparation of nanopowder resin mixture The resin, curing agent and solvent were mixed in a mass ratio of 50:8:40 and stirred at room temperature for 3 hours at a stirring rate of 800 r / min. Then, nanopowder and additives were added and stirred for another 3 hours at a stirring rate of 1000 r / min. The mixture was then heated and stirred at 50°C for 30 minutes at a stirring rate of 1000 r / min and cooled to room temperature to obtain a nanopowder resin mixture. 2) Mix the nano-powder resin mixture with conductive metal powder until uniform, grind it 5 times through a three-roll mill, and filter it through a filter to obtain the low-temperature conductive paste required for metal plate printing.

[0063] The rest is the same as in Example 1.

[0064] Example 3 A low-temperature conductive paste for metal plate printing, the raw materials for which are prepared include the following components in parts by weight: 73 parts of conductive metal powder 18 parts of nano silver powder 9.8 parts of resin composite One part of the auxiliary agent.

[0065] The conductive metal powder consists of 5 parts pure silver powder and 68 parts silver-coated copper powder.

[0066] The resin composite was prepared by mixing resin, curing agent and solvent in a mass ratio of 50:8:40.

[0067] The resin comprises 1 part phenolic resin, 0.7 parts organosilicon epoxy resin, 0.3 parts polybutadiene resin, and 3 parts bisphenol F type epoxy resin.

[0068] The curing agent used is 0.8 parts of 2-ethyl-4-methylimidazole.

[0069] The solvent used is 3 parts diethylene glycol butyl ether acetate and 1 part dimethyl adipate.

[0070] Additives include dispersants, antistatic agents, coupling agents, and antioxidants.

[0071] The dispersant used is 0.2 parts of sodium dodecylbenzenesulfonate.

[0072] The antistatic agent used is 0.3 parts of alkyl dicarboxymethyl ammonium acetone.

[0073] The coupling agent consists of 0.1 parts of γ-aminopropyltrimethoxysilane and 0.2 parts of bis(triethanolamine)diisopropyltitanate.

[0074] The antioxidant used is 0.2 parts of 1,3,5-tris(3,5-di-tert-butyl-4-hydroxyphenyl) isocyanate.

[0075] A method for preparing a low-temperature conductive paste for metal plate printing includes the following steps: 1) Preparation of nanopowder resin mixture The resin, curing agent and solvent were mixed in a mass ratio of 50:8:40 and stirred at room temperature for 2 hours at a stirring rate of 1000 r / min. Then, nanopowder and additives were added and stirred for another 2 hours at a stirring rate of 1300 r / min. The mixture was then heated and stirred at 60°C for 20 minutes at a stirring rate of 1300 r / min and cooled to room temperature to obtain a nanopowder resin mixture. 2) Mix the nano-powder resin mixture with conductive metal powder until uniform, grind it 4 times through a three-roll mill, and filter it through a filter to obtain the low-temperature conductive paste required for metal plate printing.

[0076] The rest is the same as in Example 1.

[0077] Example 4 The difference between this embodiment and Embodiment 1 is that the low-temperature conductive paste for metal plate printing disclosed in this embodiment is prepared by the following components in parts by weight: 79 parts of conductive metal powder 14 parts of nano powder 9.8 parts of resin composite One part of the auxiliary agent.

[0078] The conductive metal powder has an average particle size of 3μm and a tap density of 6g / cc.

[0079] The conductive metal powder consists of 11 parts pure silver powder and 68 parts silver-coated copper powder.

[0080] The average particle size of the nanoparticles is 300 nm, and the tap density is 5 g / cc.

[0081] The nanopowder consists of 13.7 parts of nano silver powder and 0.3 parts of nano silica.

[0082] A method for preparing a low-temperature conductive paste for metal plate printing includes the following steps: 1) Preparation of nanopowder resin mixture The resin, curing agent and solvent were mixed in a mass ratio of 50:8:40 and stirred at room temperature for 3 hours at a stirring rate of 800 r / min. Then, nanopowder and additives were added and stirred for another 3 hours at a stirring rate of 1000 r / min. The mixture was then heated and stirred at 50°C for 30 minutes at a stirring rate of 1000 r / min and cooled to room temperature to obtain a nanopowder resin mixture. 2) Mix the nano-powder resin mixture with conductive metal powder until uniform, grind it 5 times through a three-roll mill, and filter it through a filter to obtain the low-temperature conductive paste required for metal plate printing.

[0083] The rest is the same as in Example 2.

[0084] Example 5 The difference between this embodiment and Embodiment 1 is that the low-temperature conductive paste for metal plate printing disclosed in this embodiment is prepared by the following components in parts by weight: 79 parts of conductive metal powder 15 parts of nano powder 9.8 parts of resin composite One part of the auxiliary agent.

[0085] The nanopowder consists of 14.5 parts of nano silver powder and 0.5 parts of nano silica.

[0086] The rest is the same as in Example 2.

[0087] After the additive components in the slurry used in Examples 1-5 were added to the resin system dispersed by nanopowder, the measured Zeta values ​​were 33mv, 35mv, 38mv, -30mv, and -32mv, respectively, and the absolute values ​​were all higher than 30mv.

[0088] The printing plates used in Examples 1-5 were all steel mesh.

[0089] The conductive pastes used in Examples 6-10 correspond to those used in Examples 1-5, respectively. The screen printing plates used in Examples 6-10 were all nickel screens.

[0090] The difference between Comparative Example 1 and Example 1 is that the preparation method of the conductive paste in Comparative Example 1 includes the following steps: Resin, curing agent, and solvent were mixed in a mass ratio of 50:8:40. Then, nanoparticles, additives, and conductive metal powder were added and mixed thoroughly. The mixture was then ground three times using a three-roll mill and filtered to obtain the desired low-temperature conductive paste for metal plate printing. The rest was the same as in Example 1.

[0091] The difference between Comparative Example 2 and Comparative Example 1 is that the printing screens used are different.

[0092] The difference between Comparative Example 3 and Example 1 is that the printing screen used is different.

[0093] The testing and evaluation methods for conductive pastes are as follows: 1. Viscosity Viscosity was tested using a Bollerfeld viscometer at a rotation speed of 10 revolutions per minute for 4 minutes. 2. Resistivity test The resistance across the sintered electrode body was measured using a four-probe ohmmeter. 3. Ohmic contact resistance test The conductive paste is printed onto the heterojunction solar cell through a metal plate and then dried and cured. The contact resistance is measured using a contact resistance device. 4. Printing quality assessment It has a good appearance, no flakes, broken grids, nodes, or false printing, and can guarantee continuous printing for a long time with stable wet weight. 5. Measurement of wet weight of grid wire The wet weight of the grid lines is determined by measuring the weight change of the battery cells before and after printing on the same screen using an electronic scale. 6. Linearity test after curing. The morphology of the grid lines after curing was measured by electron dot microscopy, and their height and width were measured to calculate their aspect ratio. 7. Electrical performance testing Solar simulator, 25℃, M1.5 spectrum, 1KW / m 2 .

[0094] The test results are shown in Table 1.

[0095] Table 1 As shown in Table 1, Examples 1-10 confirm that the slurry prepared by pre-curing after nanoparticle dispersion is compatible with metal screen printing and exhibits good printability. Comparative Examples 1-2, however, did not first prepare the nanoparticle-resin mixture before mixing and stirring it with conductive metal powder, and lacked pre-curing. Although the differences in line resistance and contact resistance were not significant, the poor powder dispersion may have led to poor cell appearance during metal plate printing, resulting in issues such as uneven cell size and uneven thickness, posing a greater risk and failing to demonstrate the efficiency advantages of metal plate printing.

[0096] Any parts or structures not specifically described in this invention can be made using existing technologies or products, and will not be elaborated upon here.

[0097] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A low temperature conductive paste for printing of metal plates, characterized in that, The raw materials for preparing the low-temperature conductive paste include the following components in parts by weight: 68-83 parts of conductive metal powder 10-20 parts of nano powder 2-10 parts of resin compound Additives 1-3 parts.

2. A low temperature conductive paste for printing on metal plates according to claim 1, characterized in that, The conductive metal powder has the following particle size requirements: D50 = 2.5-4μm, D100 ≤ 8μm, average particle size of 3-5μm, and tap density of not less than 4.5g / cc.

3. A low temperature conductive paste for printing on metal plates according to claim 1 or 2, characterized in that, The conductive metal powder is one or a combination of pure silver powder, pure copper powder, silver-coated copper powder, and alloy powder, and the alloy powder is one or a combination of tin-silver alloy powder, tin-bismuth-silver alloy, and tin-nickel alloy.

4. The low temperature conductive paste for printing of metal plate according to claim 1, wherein, The nanoparticles have an average particle size of 300-500 nm and a tap density of not less than 3.5 g / cc.

5. The low temperature conductive paste for printing on metal plate according to claim 1 or 4, characterized in that, The nanopowder is one or a combination of several of the following: nano silver powder, nano copper powder, and nano silica.

6. A low temperature conductive paste for printing on metal plates according to claim 1, characterized in that, The resin composite was prepared by mixing resin, curing agent and solvent in a mass ratio of (40-65):(2-8):(30-60).

7. A low temperature conductive paste for printing on metal plates according to claim 6, characterized in that, The resin is a thermosetting resin; the curing agent is an imidazole compound; and the solvent is an organic solvent.

8. A low-temperature conductive paste for metal plate printing according to claim 7, characterized in that, The thermosetting resin is one or a combination of several of epoxy resin, polyester resin, phenolic resin, urea-formaldehyde resin, polybutadiene resin, silicone resin, and acrylic resin; the imidazole compound is one or a combination of several of 1,3-diazacyclopentadiene, 2-methylimidazolium, 2-ethylimidazolium, 2-ethyl-4-methylimidazolium, and 1-cyanoethyl-2-phenylimidazolium; the organic solvent is one or a combination of several of diethylene glycol butyl ether, diethylene glycol butyl ether acetate, dimethyl adipate, terpineol, divalent ester, butyl acetate, and ethylene glycol ethyl ether acetate.

9. A low-temperature conductive paste for metal plate printing according to claim 1, characterized in that, The additives include dispersants, antistatic agents, coupling agents and antioxidants, and the mass ratio is (0.2-1):(0.2-1):(0.2-1):(0.2-1).

10. A method for preparing a low-temperature conductive paste for metal plate printing according to any one of claims 1-9, characterized in that, Includes the following steps: 1) Preparation of nanopowder resin mixture The resin, curing agent, and solvent are mixed in a mass ratio of (40-65):(2-8):(30-60), and stirred at room temperature for 1-3 hours at a stirring rate of 800-1200 r / min. Then, nanopowder and additives are added, and stirring is continued for 1-3 hours at a stirring rate of 1000-1500 r / min. The mixture is then heated and stirred at 50-70℃ for 10-30 minutes at a stirring rate of 1000-1500 r / min, and cooled to room temperature to obtain a nanopowder resin mixture. 2) Mix the nano-powder resin mixture with conductive metal powder until uniform, grind and filter to obtain the desired low-temperature conductive paste for metal plate printing.

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