Single-component low-temperature curing silver paste capable of being stored at normal temperature and preparation method of single-component low-temperature curing silver paste

Abstract

According to the single-component low-temperature curing silver paste stored at normal temperature and the preparation method, polyhedral silver-coated copper powder and nano silver powder are compounded, the contact area between the powder is increased, the resistance is reduced, meanwhile, the characteristic that the nano silver powder can be molten at 180 DEG C is utilized, gaps between the powder are filled, part of colloid is driven away, and the resistivity is further reduced. A closed antimony salt cationic initiator is adopted to cure alicyclic epoxy resin, lower-temperature rapid curing is achieved, oxidation of silver-coated copper powder in the heating curing process is avoided, meanwhile, it is guaranteed that slurry has low viscosity, construction performance is ensured, and in addition, in order to avoid hindering of high metal powder filling on slurry curing, the construction efficiency is improved. The enclosed antimony salt is dissolved by alcohol and is uniformly dispersed in the whole slurry, so that the carrier resin is completely cured, and the problem of grid line pulverization is avoided. The method can be used for printing heterojunction (HJT) photovoltaic cells, laminated cells and flexible circuit boards, and can be industrially produced.

Description

Technical Field

[0001] The present invention relates to the technical field of low-temperature curing silver pastes, in particular to a one-component low-temperature curing silver paste for room-temperature storage and a preparation method thereof. Background Art

[0002] With the booming development of the photovoltaic industry, the HJT battery technology has been vigorously promoted due to its high efficiency. Because of its double-sided structure, the HJT has the advantages of high conversion efficiency and low light-induced attenuation rate. In addition, the production process is simple, and it has obvious advantages compared with Topcon batteries. However, low-temperature silver pastes with a sintering temperature of <250°C need to be coated on both the front and back, resulting in a high silver consumption. The cost accounts for 1 / 4 of the total battery cost, becoming one of the constraints for catching up with the development of Topcon batteries. Promoting continuous technological innovation of low-temperature silver pastes, technological upgrading and cost control have become two major bottlenecks that must be faced in the development of low-temperature silver pastes.

[0003] One of the major measures to reduce the cost of low-temperature silver paste is to use inferior metals to replace silver powder. Among them, copper powder has a resistivity similar to that of silver powder. However, as the particle size of copper powder decreases, the oxidation temperature gradually drops to 200 °C, resulting in a significant increase in resistivity, thus limiting the application of copper powder. To fully utilize the high conductivity and antioxidant properties of silver powder and the low cost and high conductivity of copper, the industry adopts a solution of coating silver on the surface of copper powder. However, on the market, all are spherical silver-coated copper powders with a rough surface, which increases the oil absorption rate. In addition, the spherical powder uses point contact, resulting in a high resistivity and making it difficult to actually replace silver powder. Currently, low-temperature curing conductive silver paste generally uses a single-component epoxy system with imidazole, dicyandiamide, or capsule-coated curing agents, and there are the following problems: 1. Processing: Imidazole or modified imidazole, dicyandiamide, and capsule-type curing agents are all solid powders with a large usage amount. When making a high solid content of conductive powder, the viscosity of the system is high, resulting in difficult dispersion and even deformation of the powder and rupture of the capsule curing agent; when the curing agent is released, the high viscosity will make it difficult to brush the paste, and the release of the capsule-type curing agent will cause the slurry to gradually gel, also increasing the system viscosity and increasing the construction difficulty. Using a solvent to reduce the slurry viscosity will cause a large number of voids in the conductive grid lines during the curing process, increasing the resistivity; 2. Curing temperature and efficiency: Imidazole and its modifiers, dicyandiamide have low curing efficiency during the curing process. Although increasing the temperature can shorten the curing time, it accelerates the oxidation of silver-coated copper powder and also causes the single-crystalline silicon wafer to be easily deformed; although the capsule-type curing agent has no problems with curing temperature and efficiency, the reliability of the capsule is not guaranteed, the usage amount is large, it is easy to cause blockage between metal powders and affect the adhesion, and it is easy to cause problems such as grid line dropping and poor compatibility with the TCO layer; 3. Storage: Imidazole and its modifiers and capsule-type curing agents, especially capsule-type curing agents, cannot achieve 100% coating. Although the reaction rate is slow at the set temperature, as the slurry is stored, the system viscosity gradually increases, affecting the construction performance. Although the industry now uses low-temperature refrigeration, which greatly improves the storage period of the slurry, the slurry needs to experience a 3-4-hour temperature recovery from refrigeration to activation. During the temperature recovery process, a large amount of moisture is easily agglomerated outside the slurry packaging and is easily brought into the slurry during the process of opening the slurry can, causing pores in the grid lines and accelerating the oxidation of silver-coated copper powder. The refrigeration method increases the investment in fixed equipment in the using factory, reduces production efficiency, and increases management costs. Summary of the Invention

[0004] In order to overcome the above-mentioned shortcomings of the prior art, the object of the present invention is a single-component low-temperature curing silver paste with normal-temperature storage and a preparation method thereof.

[0005] The technical solution adopted by the present invention to solve its technical problems is: A preparation method of a single-component low-temperature curing silver paste with normal-temperature storage, comprising the following steps:

[0006] (1) Powder dispersion and wetting:

[0007] Add absolute ethanol, then add a certain amount of polyhedral silver-coated copper powder and nano silver powder, and disperse them to obtain a uniform slurry. Then heat it to 80 °C and evacuate to remove the moisture and residual organic matter in the solvent and powder. Transfer the powder to a flipping mixing kettle, and then supplement terpene alcohol, polyethylene glycol, alicyclic epoxy resin, cationic thermal initiator alcohol solution, etc. that have been dehydrated, and conduct flipping dispersion and wetting until a smooth, mud-like grayish-black paste is obtained.

[0008] (2) Roll-rolling dispersion:

[0009] Put the above-mentioned mud-like black paste into roll-rolling dispersion until the paste completely turns into a slurry.

[0010] (3) Transfer the slurry to a stirring kettle, stir at 50 - 150 RPM while evacuating to remove air bubbles. After no visible bubbles are seen by the naked eye, press and package the material, and blow dry air over the packaging cans and then seal them with lids.

[0011] As a further improvement of the present invention: In the step (1), the particle size of the polyhedral silver-coated copper powder is 3 - 5 μm and 0.2 - 0.6 μm, and the particle size of the nano silver powder is 0.2 - 0.4 μm.

[0012] As a further improvement of the present invention: The ratio between polyhedral silver-coated copper powders is 3 - 5 μm polyhedral silver-coated copper powder: 0.2 - 0.6 μm polyhedral silver-coated copper powder = 125 - 15625.

[0013] As a further improvement of the present invention: The ratio between polyhedral silver-coated copper powder and nano silver powder is silver-coated copper powder: nano silver powder (0.2 - 0.3 μm) = 1: (1.89 - 1.91), and the silver mass fraction in the silver-coated copper powder is 30% - 60%.

[0014] As a further improvement of the present invention: In the step (1), the alicyclic epoxy is one or a mixture of 3,4-epoxycyclohexylmethyl 3',4'-epoxycyclohexanecarboxylate (CAS: 2386-87-0), bis(3,4-epoxycyclohexyl)methyl adipate (CAS: 3130-19-6), 3,4-epoxycyclohexyl methacrylate (CAS: 64630-63-3), poly[2-(epoxyethoxy)]-1,2-cyclohexanediol 2-ethyl-2-(hydroxymethyl)-1,3-propanediol ether (CAS: 244772-00-7).

[0015] As a further improvement of the present invention: In the step (1), the cationic thermal initiator is one of blocked triaryl sulfonium hexafluorophosphate, blocked triaryl iodonium hexafluorophosphate, and blocked diphenyl iodonium antimonate.

[0016] As a further improvement of the present invention: in the step (1), the deblocking temperature of the cationic thermal initiator is 70 - 80 °C, and 2-methyl-2,4-pentanediol is used for dissolution.

[0017] As a further improvement of the present invention: in the step (2), the roll gap is set to 30 - 50 μm for roll dispersion. After the paste is completely turned into a slurry, the roll gap is adjusted to 20 - 30 μm, and the slurry becomes finer; then the roll gap is adjusted to 10 - 15 μm, and the roll speed is 100 RPM.

[0018] The present invention also includes a one-component low-temperature curable silver paste stored at room temperature prepared by using the preparation method of a one-component low-temperature curable silver paste stored at room temperature described above, which includes the following components by weight percentage:

[0019] Alicyclic epoxy resin: 7% - 10%

[0020] Terpineol: 2% - 4.5%

[0021] Cationic thermal initiator: 0.1% - 0.2%

[0022] Composite conductive powder (silver-coated copper powder / nano silver powder): 80% - 85%

[0023] Defoaming agent: 0.02% - 0.1%

[0024] Wetting and dispersing agent: 0.03% - 0.2%

[0025] 2-Methyl-2,4-pentanediol: the balance.

[0026] As a further improvement of the present invention: it includes the following components by weight percentage:

[0027] Alicyclic epoxy resin: 5%

[0028] Alicyclic epoxy resin: 2%

[0029] Terpineol: 4.5%

[0030] Thermal cationic initiator: 0.2%

[0031] Composite conductive powder - silver-coated copper powder: 80%

[0032] Composite conductive powder - nano silver powder: 5%

[0033] Defoaming agent: 0.05%

[0034] Wetting and dispersing agent: 0.02%

[0035] 2-Methyl-2,4-pentanediol 3.3%.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows: The method of the present invention overcomes the problems that the low-temperature curing conductive silver paste needs to be stored at low temperature (0-10 °C), the curing temperature is >200 °C and it is easy to cause oxidation of silver-coated copper powder. It realizes room-temperature storage (room temperature - 50 °C), is convenient to use, easy to process, easy to form grid lines metallization, and has a low resistivity (<8*10 -6 Ω.cm). It is a new type of single-component low-temperature curing silver paste with the curing temperature reduced to 110-180 °C, ensuring that the HJT photovoltaic cell is not easily warped and deformed.

[0037] A preparation method of a low-temperature curing silver paste based on the stacking of compound polyhedral conductive powder and the curing of alicyclic epoxy resin by thermal cationic initiator is provided. The resistivity of the cured silver wire is tested and the morphology is characterized, verifying that this conductive silver paste has a low resistivity and stack height thixotropy. The room-temperature storage stability of the paste is tracked, showing that there is no abnormality in the low-temperature conductive silver paste for more than 8 months. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solution, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0039] Figure 1 It is a schematic diagram of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0041] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order other than those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0042] In the manufacturing process of HJT cells, a large amount of low-temperature silver paste is required. The cost of silver paste accounts for about one-fourth of the total cost of the cell, which has become one of the bottlenecks restricting the development of HJT cells. Therefore, reducing the cost of silver paste and improving the technology have become urgent problems to be solved in the industry. To reduce costs, one solution is to use inferior metals (such as copper powder) to replace silver powder. The resistivity of copper powder is similar to that of silver powder, but as the particle size of copper powder decreases, the oxidation temperature decreases, which leads to an increase in resistivity and limits the wide application of copper powder. The industry attempts to combine the high conductivity of silver and the low cost of copper by coating silver powder on the surface of copper powder. However, the silver-coated copper powder (spherical structure) used in the market has a rough surface, which increases the oil absorption rate and has a high resistivity, and cannot completely replace silver powder. Low-temperature silver paste generally uses epoxy resin as a carrier and combines silver, copper powder or silver-coated copper powder. Current curing agents are mostly imidazole-based, dicyandiamide, capsule-type curing agents, etc.; the curing agent is a solid powder, resulting in too high a viscosity of the slurry at high solid content, making it difficult to disperse and increasing the construction difficulty. In addition, the use of capsule-type curing agents may cause the slurry to gradually gel, increasing the use difficulty, and using solvents to reduce the viscosity will form voids during the curing process, affecting the conductivity. Some curing agents (such as imidazole and dicyandiamide) have low curing efficiency. Although the curing rate can be accelerated by increasing the temperature, it will cause the oxidation of silver-coated copper powder and affect the cell performance. Capsule-type curing agents cannot achieve 100% coating, and the viscosity of the slurry will increase during storage, affecting the construction performance. Although low-temperature refrigeration can extend the storage period, the warming process may cause moisture to enter, further exacerbating the oxidation problem of silver-coated copper powder; Low-temperature curing silver paste uses low-viscosity epoxy resin as a carrier, combined with various powders and curing agents. However, as the gate line size decreases, the particle size of the powder enters below 10 microns. Especially after adding silver-coated copper powder, the oxidation temperature of copper powder decreases, resulting in that this system cannot meet the requirements of current low-temperature curing conductive silver paste. In addition, the inconvenience and cost brought by the refrigerated storage method also exacerbate this problem.

[0043] To solve the above problems, the present application provides a conductive silver paste that can be stored at room temperature and cured at low temperature, and has a resistivity of 10-6Ω. This paste has the advantages of room temperature storage, low temperature curing, low resistivity, easy processing, and ready-to-use. The implementation method is as follows: Polyhedral silver-coated copper powder and nano silver powder are compounded. While increasing the contact area between powder particles to reduce resistance, the property that nano silver powder can melt at 180°C is utilized to fill the gaps between powder particles and expel part of the colloid, further reducing the resistivity. In addition, a blocked stibonium salt cation initiator is used to cure the alicyclic epoxy resin to achieve rapid curing at a lower temperature, avoiding the oxidation of silver-coated copper powder during the heating curing process, and at the same time ensuring that the paste has a low viscosity to ensure the construction performance. In addition, to avoid the hindrance of high metal powder filling to the curing of the paste, alcohol is used to dissolve the blocked stibonium salt and uniformly disperse it throughout the paste to ensure the complete curing of the carrier resin and prevent the problem of grid line powdering. Thus, the development bottleneck in the current industry of being unable to have both cost reduction and low resistivity of the paste is solved. The conductive silver paste prepared by this method has low cost, excellent performance, and convenient processing; it can be used for printing heterojunction (HJT) photovoltaic cells, tandem cells, and flexible circuit boards, and can be industrially produced.

[0044] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: A single-component low-temperature curing silver paste for room temperature storage and its preparation method. A preparation method of a single-component low-temperature curing silver paste for room temperature storage includes the following steps:

[0045] (1) Powder dispersion and wetting:

[0046] Add absolute ethanol, then add a certain amount of polyhedral silver-coated copper powder and nano silver powder, disperse to obtain a uniform paste, then heat to 80°C and evacuate to remove the moisture and residual organic matter in the solvent and powder. Transfer the powder to a flipping mixing kettle, and then supplement dehydrated pine oil alcohol, polyethylene glycol, alicyclic epoxy resin, cationic thermal initiator alcohol solution, etc., and perform flipping dispersion and wetting until a smooth mud-like grayish-black paste is obtained;

[0047] (2) Roll rolling dispersion:

[0048] Put the above-mentioned mud-like black paste into roll rolling dispersion until the paste completely becomes slurry;

[0049] (3) Transfer the paste to a stirring kettle, stir at 50 - 150 RPM while evacuating to remove air bubbles. After no visible air bubbles are seen, press and package, and blow dry air on the packaging can and then seal it.

[0050] A single-component low-temperature curing silver paste for room temperature storage includes the following components by weight percentage:

[0051] Alicyclic epoxy resin: 7% - 10%

[0052] Terpineol: 2% - 4.5%

[0053] Cationic thermal initiator: 0.1% - 0.2%

[0054] Composite conductive powder (silver-coated copper powder / nano silver powder): 80% - 85%

[0055] Defoamer: 0.02% - 0.1%

[0056] Wetting and dispersing agent: 0.03% - 0.2%

[0057] 2-Methyl-2,4-pentanediol: the balance.

[0058] A one-component low-temperature curing silver paste for room-temperature storage and its preparation method provided by the present invention adopt a compound polyhedral conductive powder, which has high thixotropy and excellent packing ability, ensuring the precise printing of grid lines. During the grid line printing process, the silver paste can achieve a stacking effect close to 90°, avoiding the burr and filament problems that easily occur in traditional silver pastes, and significantly improving the production quality; the one-component low-temperature curing conductive silver paste can be stored at room temperature for more than 8 months; the manufacturing process is simple and controllable, and the rejection rate is low; the initial curing temperature of the paste is 110 - 150°C for rapid curing, and it reaches 180°C for 2 minutes for rapid metallization. Compared with the traditional curing temperature above 200°C, the energy consumption during the curing process is significantly reduced, and the oxidation problem of silver-coated copper powder is effectively reduced, thereby improving the stability and conductive performance of the silver paste.

[0059] As an embodiment of the present invention, the particle size of the polyhedral silver-coated copper powder of specification 1 is 3 - 5μm, the particle size of the polyhedral silver-coated copper powder of specification 2 is 0.2 - 0.6μm, the particle size of the nano silver powder is 0.2 - 0.4μm, and the ratio between the polyhedral silver-coated copper powders: polyhedral silver-coated copper powder (3 - 5μm): polyhedral silver-coated copper powder (0.2 - 0.6μm) = 125 - 15625 (mass ratio); the ratio between the polyhedral silver-coated copper powder and the nano silver powder: silver-coated copper powder: nano silver powder (0.2 - 0.3μm) = 1:(1.89 - 1.91) (mass ratio); the silver mass proportion in the silver-coated copper powder is 30% - 60%;

[0060] The alicyclic epoxy is one or a mixture of several of 3,4-epoxycyclohexylmethyl 3',4'-epoxycyclohexanecarboxylate (CAS: 2386-87-0), bis(3,4-epoxycyclohexylmethyl) adipate (CAS: 3130-19-6), 3,4-epoxycyclohexyl methacrylate (CAS: 64630-63-3), poly[2-(epoxyethanyl)]-1,2-cyclohexanediol 2-ethyl-2-(hydroxymethyl)-1,3-propanediol ether (CAS: 244772-00-7). Among them, poly[2-(epoxyethanyl)]-1,2-cyclohexanediol 2-ethyl-2-(hydroxymethyl)-1,3-propanediol ether exceeds 10% of the total epoxy resin.

[0061] The cationic thermal initiator is one of blocked triaryl sulfonium hexafluorophosphate, blocked triaryl iodonium hexafluorophosphate, and blocked diphenyl iodonium antimonate. The deblocking temperature is 70 - 80 °C, and it can complete curing with the above-mentioned alicyclic epoxy at 110 °C - 120 °C within 10 minutes. 2-Methyl-2,4-pentanediol is used for dissolution.

[0062] Among them, all raw materials are commercially available.

[0063] The mass ratio (125 - 15625) of polyhedral silver-coated copper powder of specification 1 to specification 2 ensures the coordinated combination of the two powders, further optimizing the conductivity and packing property of the paste. The fine-particle-size silver-coated copper powder can fill the gaps between the larger-particle-size powders, thus improving the overall conductivity and stability of the silver paste. The mass ratio of silver-coated copper powder to nano silver powder is 1:(1.89 - 1.91), and this ratio ensures the balance of silver-coated copper powder and nano silver powder in terms of conductivity. The addition of nano silver powder can further improve the conductivity of the paste, while silver-coated copper powder reduces the overall cost and provides good antioxidant performance. The silver mass proportion in the silver-coated copper powder is between 30% and 60%. The setting of this ratio can control the cost of the material while ensuring conductivity and antioxidant property. The proportion of silver is high enough to ensure excellent conductivity, and at the same time, the addition of copper powder effectively reduces the cost, meeting the market demand.

[0064] Using cationic thermal initiators such as blocked triaryl sulfonium hexafluorophosphate, with a deblocking temperature of 70 - 80 °C, this choice can ensure precise temperature control during the curing process and can quickly complete curing (within 10 minutes) at 110 °C - 120 °C. This fast-curing characteristic reduces the curing time and improves production efficiency. Using 2-methyl-2,4-pentanediol as the dissolution solvent can not only effectively dissolve the initiator but also adjust the viscosity of the paste, making it more stable during use, facilitating operation, and improving the accuracy and consistency of grid line metallization.

[0065] The temperature during the curing process is set to 110°C - 150°C for initial curing, and then rapid metallization is carried out at 180°C for 2 minutes. This can achieve rapid curing and metallization while ensuring a low curing temperature. This optimized curing process can ensure the metallization effect of the silver wires, improve the conductivity, and avoid wafer warping or deformation caused by high temperature. Through this optimized ratio, the resistivity of the paste can be maintained at <8*10 -6 Ω.cm, showing excellent conductive performance. At the same time, the silver paste has good stacking property, and can achieve a stacking effect close to 90°, avoiding the burr phenomenon in grid line printing.

[0066] As an embodiment of the present invention, in step (2), the roll gap is set to 30 - 50 microns, and the above-mentioned muddy black paste is put in for roll dispersion. After the paste is completely turned into a slurry, the roll gap is adjusted to 20 - 30 microns and rolled once, and the slurry becomes finer; then the roll gap is adjusted to 10 - 15 microns, the roll speed is 100 RPM, and a doctor blade fineness gauge is used for detection until the particle size < 10 microns is qualified.

[0067] As an embodiment of the present invention, a one-component low-temperature curing silver paste for ambient temperature storage comprises the following components by weight percentage:

[0068] Alicyclic epoxy resin (TTA-21P) 5%

[0069] Alicyclic epoxy resin (TTA-3150) 2%

[0070] Terpineol 4.5%

[0071] Thermal cationic initiator: 0.2%

[0072] Composite conductive powder (silver-coated copper powder) 80%

[0073] Composite conductive powder (nano silver powder) 5%

[0074] Defoamer (A530) 0.05%

[0075] Wetting and dispersing agent (9076) 0.02%

[0076] 2-Methyl-2,4-pentanediol 3.3%

[0077] The resistivity of the one-component low-temperature curing silver paste prepared using the above ratio is 1.1 mΩ·cm after curing.

[0078] The following are the test data of the one-component low-temperature curing silver paste prepared by using the preparation method of the one-component low-temperature curing silver paste of the present invention for ambient temperature storage:

[0079]

[0080]

[0081] According to the resistivity data analysis:

[0082] Maximum Minimum Average Maximum percentage change Radial non-uniformity 3.6 3.35 3.45 7.46％ 7.19％

[0083] The main functions of the present invention:

[0084] The curing temperature is reduced to 110 - 180°C, far lower than the >200°C required for traditional silver paste curing, thus effectively avoiding the problem that silver-coated copper powder is prone to oxidation at high temperatures. While curing at low temperature, the structural stability of the HJT photovoltaic cell during the manufacturing process is ensured; it has a low resistivity (<8×10^-6 Ω·cm), ensuring excellent electrical conductivity and being suitable for the grid line metallization process of high-efficiency photovoltaic cells. The conductive silver paste with low resistivity improves the electrical conductivity of the battery, thereby optimizing the conversion efficiency of the battery. The compound polyhedral conductive powder is used, which has high thixotropy and excellent packing performance, ensuring that the silver paste can achieve a stacking effect of nearly 90° during the grid line printing process, without burrs, ensuring the printing accuracy and metallization quality. The slurry shows no abnormality after being stored at room temperature for more than 8 months, indicating excellent storage stability. This means that the silver paste has a long shelf life, is suitable for large-scale production and storage, and can effectively reduce the scrap rate caused by slurry failure during the production process. The preparation method provided by the present invention is simple and controllable, the slurry is stable during the operation process, is not easy to deform or gel, reduces the complexity during the production process, improves the production efficiency, and has a low scrap rate.

[0085] In summary, after those of ordinary skill in the art read the documents of the present invention, all other corresponding transformation schemes made without creative mental labor according to the technical solutions and technical concepts of the present invention shall fall within the scope protected by the present invention.

Claims

1. A method for preparing a single-component low-temperature curing silver paste stored at room temperature, characterized in that: The following steps are involved: (1) Powder dispersion and wetting: Anhydrous ethanol is added, and then a certain amount of polyhedral silver-coated copper powder and nano silver powder are added to disperse to obtain a uniform slurry, and then heated to 80°C and evacuated, and the powder is transferred to a tumbling mixing kettle, and then added with dehydrated pinene alcohol, polyethylene glycol, alicyclic epoxy resin, and cationic thermal initiator alcohol solution, and tumbling, dispersing and wetting are performed until a muddy gray-black paste with a smooth surface is obtained; (2) Roller dispersion: Add the above muddy black paste and roll it to disperse it until the paste becomes slurry; (3) Transfer the slurry to a stirring kettle and perform vacuum degassing while stirring at 50-150 RPM until no bubbles are visible to the naked eye. Then press the material into packages and blow dry air through the packaging cans before sealing them.

2. The method for preparing a single-component low-temperature curing silver paste stored at room temperature according to claim 1, characterized in that: In the step (1), the particle sizes of the polyhedron silver-coated copper powder are 3-5 μm and 0.2-0.6 μm, and the particle size of the nano silver powder is 0.2-0.4 μm.

3. The method for preparing a single-component low-temperature curing silver paste stored at room temperature according to claim 2, characterized in that: The ratio of the polyhedron silver-coated copper powder is 3-5 μm polyhedron silver-coated copper powder: 0.2-0.6 μm polyhedron silver-coated copper powder = 125-15625.

4. The method for preparing a single-component low-temperature curing silver paste stored at room temperature according to claim 3, characterized in that: The ratio of the polyhedron silver-coated copper powder to the nano silver powder is silver-coated copper powder: nano silver powder (0.2-0.3 μm)=1:(1.89-1.91).

5. The method for preparing a single-component low-temperature curing silver paste stored at room temperature according to claim 1, characterized in that: In the step (1), the alicyclic epoxy is one or a mixture of 3,4-epoxycyclohexylcarboxylic acid-3',4'-epoxycyclohexyl methyl ester (CAS: 2386-87-0), bis(3,4-epoxycyclohexyl)methyl)adipate (CAS: 3130-19-6), 3,4-epoxycyclohexyl methacrylate (CAS: 64630-63-3), poly[2-oxiranyl]-1,2-cyclohexanediol 2-ethyl-2-(hydroxymethyl)-1,3-propylene glycol ether) (CAS: 244772-00-7).

6. The method for preparing a single-component low-temperature curing silver paste stored at room temperature according to claim 1, characterized in that: The cationic thermal initiator in step (1) is one of blocked triarylsulfonium hexafluorophosphate, blocked triaryliodonium hexafluorophosphate and blocked diphenyliodonium antimonate.

7. The method for preparing a single-component low-temperature curing silver paste stored at room temperature according to claim 6, characterized in that: In the step (1), the deblocking temperature of the cationic thermal initiator is 70-80° C., and 2-methyl-2,4-pentanediol is used for dissolution.

8. The method for preparing a single-component low-temperature curing silver paste stored at room temperature according to claim 7, characterized in that: In the step (2), the roller distance is set to 30-50 microns for roller dispersion. When the paste is completely transformed into a slurry, the roller distance is adjusted to 20-30 microns, and the slurry becomes finer. The roller distance is then adjusted to 10-15 microns and the roller speed is 100 RPM.

9. A single-component low-temperature curing silver paste stored at room temperature prepared by the method for preparing a single-component low-temperature curing silver paste stored at room temperature according to any one of claims 1 to 8, characterized in that: The composition includes the following weight percentages: Alicyclic epoxy resin: 7% to 10% Terpineol: 2% to 4.5% Cationic thermal initiator: 0.1%~0.2% Composite conductive powder (silver-coated copper powder / nano silver powder): 80%~85% Defoaming agent: 0.02%~0.1% Wetting and dispersing agent: 0.03%~0.2% 2-Methyl-2,4-pentanediol: balance.

10. The single-component low-temperature curing silver paste stored at room temperature according to claim 9, characterized in that: The composition includes the following weight percentages: Cycloaliphatic epoxy resin: 5% Cycloaliphatic epoxy resin: 2% Terpineol: 4.5% Thermal cationic initiator: 0.2% Composite conductive powder-silver coated copper powder: 80% Composite conductive powder-nano silver powder: 5% Defoamer: 0.05% Wetting and dispersing agent: 0.02% 2-Methyl-2,4-pentanediol 3.3%.

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