Low-resistance high-temperature-resistant conductive adhesive, preparation method, use method and photovoltaic module thereof

Abstract

The application provides a low-resistance high-temperature-resistant conductive adhesive as well as a preparation method, a use method and a photovoltaic module thereof, and relates to the technical field of electronic packaging materials. The low-resistance high-temperature-resistant conductive adhesive comprises, calculated based on the total mass of raw materials of the low-resistance high-temperature-resistant conductive adhesive as 100%, 45-60% of silver-coated ceramic powder, 10-20% of nano silver wire, 1-2% of silicon carbide whisker, 20-30% of polyimide resin and 0.1-0.5% of antioxidant. The base material of the polyimide resin is acetylene-terminated polyimide. The antioxidant comprises BHT. The conductive adhesive provided by the application can enable the material to maintain stable conductive performance and mechanical strength after long-term high-temperature aging, and is suitable for application scenarios such as photovoltaic modules which have strict requirements on weather resistance.

Description

Technical Field

[0001] This application relates to the field of electronic packaging materials technology, specifically to a low-resistance, high-temperature resistant conductive adhesive, its preparation method, application method, and photovoltaic module. Background Technology

[0002] In the field of electronic packaging, conductive adhesives are widely used as key interconnect materials in the packaging processes of electronic devices such as photovoltaic modules. Traditional conductive adhesives typically use pure silver powder as a conductive filler. While this offers excellent conductivity, it suffers from the problems of excessive silver content and high cost. To reduce silver usage, existing technologies have introduced alternatives using silver-plated polyethylene resin as the conductive filler. However, this approach has significant technical drawbacks: polyethylene resin, as a plastic matrix material, has a significantly higher coefficient of thermal expansion than metals, leading to a noticeable thermal expansion mismatch between it and the silver powder filler under high-temperature operating conditions. This difference in thermal expansion results in interfacial stress accumulation, particularly under high and low temperature cycling conditions, which can easily cause microcracks in the conductive filler layer. More seriously, under aging conditions such as high temperature and high humidity, the polyethylene resin matrix undergoes embrittlement and degradation, further exacerbating interfacial failure. These microstructural defects disrupt the integrity of the conductive network, leading to deterioration of conductive channels, abnormally high local current density, and ultimately a significant increase in the volume resistivity of the conductive adhesive, severely impacting the long-term reliability and output performance stability of electronic devices such as photovoltaic modules. In addition, the existing conductive adhesives are difficult to meet the stringent requirements of applications such as photovoltaic modules in terms of oxidation resistance and mechanical strength under high temperature conditions. Summary of the Invention

[0003] The purpose of this application is to provide a low-resistance, high-temperature resistant conductive adhesive, its preparation method, application method, and photovoltaic module, in order to solve the above-mentioned problems.

[0004] To achieve the above objectives, this application adopts the following technical solution: This application provides a low-resistance, high-temperature resistant conductive adhesive, the technical solution of which is as follows: A low-resistance, high-temperature resistant conductive adhesive, calculated based on the total mass of the conductive adhesive raw materials as 100%, includes: 45-60% silver-coated ceramic powder, 10-20% silver nanowires, 1-2% silicon carbide whiskers, 20-35% polyimide resin, and 0.1-0.5% antioxidant; The matrix material of the polyimide resin is acetylene-terminated polyimide; The antioxidants include BHT.

[0005] Furthermore, the silver-coated ceramic powder satisfies at least one of the following conditions: a. The raw material for silver-coated ceramic powder is ceramic particles with a particle size of 1-5 μm; the ceramic particles include at least one of Al2O3 and SiC; b. The particle size of the silver-coated ceramic powder is 1-10μm; c. The thickness of the silver coating on the silver-coated ceramic powder is 0.1-0.5 μm.

[0006] Furthermore, the matrix material of the polyimide resin is acetylene-terminated polyimide, and the molecular weight of the acetylene-terminated polyimide is 5000-20000; acetylene-terminated polyimide includes KH-500S.

[0007] Furthermore, at least one of the following conditions must be met: d. The total silver content in the conductive adhesive is 34.75-59%; e. The volume resistivity of the conductive adhesive is not higher than 1×10⁻⁶. -4 Ω·cm; f. The sheet resistance of the conductive adhesive is not higher than 200Ω / sq; g. The resistance change rate of the conductive adhesive after 1000 hours at 300℃ is no higher than 5%; h. The thermal decomposition temperature of the conductive adhesive is not lower than 500℃; i. The shear strength of the conductive adhesive is not less than 15 MPa; j. The elongation at break of the conductive adhesive shall not be less than 10%.

[0008] Furthermore, this application also provides a method for preparing the above-mentioned low-resistance, high-temperature resistant conductive adhesive, comprising: mixing silver-coated ceramic powder, silver nanowires, silicon carbide whiskers, polyimide resin, and antioxidant to obtain the adhesive.

[0009] Furthermore, the ceramic particles are subjected to a series of treatments, including roughening, chemical silver plating, and coupling agent treatment, to obtain silver-coated ceramic powder; and the powder must meet at least one of the following conditions: A. The roughening treatment includes: using a surface etchant to etch the ceramic particles; the surface etchant includes one of hydrofluoric acid and an alkaline solution, wherein the alkaline solution includes sodium hydroxide; B. Chemical silver plating treatment includes: reacting the roughened ceramic particles with a silver plating solution at 40-60℃ and pH 10-12 for 2-4 hours; the total mass of the silver plating solution is 100g, including: 8-12g / L AgNO3 97-99%, polyethylene glycol 1-3%; C. The silane coupling agent treatment includes: treating the chemically silver-plated ceramic particles with a silane coupling agent at 80-100℃ for 30-60 minutes; the silane coupling agent includes KH-550.

[0010] Further, the method for preparing the polyimide resin includes: mixing pyromellitic anhydride, a diamine monomer, and a polar solvent, and carrying out a polycondensation reaction to obtain a polyamic acid solution; subjecting the polyamic acid solution to imidization curing to obtain the polyimide resin; and satisfying at least one of the following conditions: D. The diamine monomer is a diamine monomer containing a phenylacetylene group; E. The polar solvent includes DMAc; F. The molar ratio of the pyromellitic anhydride and the diamine monomer is 1:0.95-1.05; G. The solid content of the polyamic acid solution is 10-15%; H. The conditions for the polycondensation reaction are: under nitrogen protection, reaction at 60-80℃ for 4-6 hours; I. The imidization curing is carried out by gradient heating, and the gradient heating conditions are as follows: First stage, heating from room temperature to 140-160℃ and holding for 0.9-1.1h; Second stage, heating to 240-260℃ and holding for 1.9-2.1h; Third stage, heating to 290-310℃ and holding for 0.9-1.1h.

[0011] Furthermore, this application also provides a method for using the above-mentioned low-resistance, high-temperature resistant conductive adhesive, which involves grinding the conductive adhesive particles and then placing them on a substrate, arranging them in a magnetic field, and then curing them at a low temperature.

[0012] Furthermore, at least one of the following conditions must be met: I. The particle size D50 of the ground conductive adhesive particles is no greater than 3μm; II. The magnetic field strength for the magnetic field orientation treatment is 50-100V / mm, and the treatment time is 10-20min; III. The conditions for low-temperature curing are: hot pressing at 150-200℃ for 10-30 minutes, with a pressure of 15-25MPa, and controlling the resin viscosity to 100-300cP.

[0013] Furthermore, this application also provides a photovoltaic module, including the aforementioned low-resistance, high-temperature resistant conductive adhesive.

[0014] Compared with the prior art, the beneficial effects of this application include: This application utilizes polyimide resin, whose rigid molecular chain structure allows it to withstand higher temperatures, and its coefficient of thermal expansion is similar to that of ceramic fillers, significantly reducing interfacial stress. Furthermore, the composite use of silver nanowires and silver-coated ceramic powder reduces silver content while maintaining conductivity through a three-dimensional network, overcoming the problem of insufficient conductivity of single fillers. This effectively solves the problem of increased resistivity in conductive adhesives due to thermal stress at high temperatures, while optimizing the conductive network through composite fillers maintains low resistance characteristics despite reduced silver content. This allows the material to maintain stable conductivity and mechanical strength even after long-term high-temperature aging, making it suitable for applications with stringent weather resistance requirements, such as photovoltaic modules.

[0015] The preparation method provided in this application solves the problem of resistivity degradation caused by insufficient thermal stability of matrix material in conductive adhesives under high temperature environment. It can achieve thermal expansion matching between conductive filler and resin matrix, thereby enhancing the structural stability of composite material under temperature changes. At the same time, the construction of multi-dimensional conductive network during the preparation process ensures the durability of conductive performance.

[0016] As can be seen from the above, the low-resistance, high-temperature resistant conductive adhesive, its preparation method, application method, and photovoltaic module provided in this application reduce the silver content through the synergistic effect of silver-coated ceramic powder and silver nanowires, optimize the thermal expansion matching by combining the polyimide resin matrix, and enhance the mechanical strength by silicon carbide whiskers. It has the advantages of reducing silver content, reducing thermal expansion mismatch, improving high-temperature oxidation resistance and mechanical strength. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0018] Figure 1 This is a photograph of the silver-coated ceramic powder prepared in Example 1. Figure 2 This is a photograph of the polyimide resin prepared in Example 1. Figure 3 This is a photograph of the conductive adhesive prepared in Example 1. Detailed Implementation

[0019] As used in this article: "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0020] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0021] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0022] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0023] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (where K is any number representing a multiplier). It is important to understand that, unlike parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0024] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0025] In existing technologies, when photovoltaic modules are subjected to high temperature and high humidity environments for extended periods, conductive adhesive materials need to possess both heat resistance and conductivity stability. Traditional conductive adhesives use silver-plated polyethylene resin as the matrix material. Although this reduces the silver content, polyethylene resin has a high coefficient of thermal expansion. During temperature cycling, this creates a thermal stress difference between the resin and the metal filler, leading to interfacial separation and the formation of microcracks. This structural defect can cause the conductive channels to break, resulting in increased resistivity and affecting the module's output performance.

[0026] To address the aforementioned issues, this application proposes a method that matches the coefficient of thermal expansion with the high-temperature resistance of the matrix material. Analysis of the thermal stability of different resin matrices revealed that polyimide materials exhibit excellent thermal decomposition temperature and dimensional stability. Further research showed that adjusting the combination of conductive fillers can optimize the continuity of the conductive network, while introducing reinforcing phase materials can suppress crack propagation. This leads to a technical approach using a high-temperature resistant resin as the matrix and composite conductive fillers working synergistically.

[0027] Therefore, in the first aspect, this application proposes a low-resistance, high-temperature resistant conductive adhesive, the total mass percentage of which is: 45-60% silver-coated ceramic powder, 10-20% silver nanowires, 1-2% silicon carbide whiskers, 20-35% polyimide resin, and 0.1-0.5% antioxidant; The matrix material of the polyimide resin is acetylene-terminated polyimide; The antioxidants include BHT (butylated hydroxytoluene).

[0028] Optionally, the amount of silver-coated ceramic powder can be 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, or any value between 45% and 60%; the amount of silver nanowires can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or any value between 10% and 20%; the amount of silicon carbide whiskers can be 1%, 1.1%, 1.2%, 1.3%. The percentages are 1%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, or any value between 1% and 2%; the amount of polyimide resin can be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, or any value between 20% and 35%; the amount of antioxidant can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or any value between 0.1% and 0.5%.

[0029] Among these, silver-coated ceramic powder refers to ceramic particles with a silver layer deposited on their surface. For example, using Al2O3 or SiC as the ceramic matrix, a silver layer is formed through a chemical plating process, reducing the amount of silver used and lowering the overall coefficient of thermal expansion through the ceramic phase. Silver nanowires refer to linear silver materials with diameters at the nanoscale, prepared for example by liquid-phase reduction, which can form a three-dimensional conductive network in a resin matrix. Silicon carbide whiskers refer to fibrous silicon carbide materials, prepared for example by vapor deposition, used to enhance the mechanical properties of materials and inhibit crack propagation. Polyimide resin refers to high-temperature resistant resins, represented by acetylene-terminated polyimide, whose molecular chain structure can withstand high-temperature environments. Antioxidants are additives that inhibit the oxidation of silver materials, used to delay the decay of conductivity.

[0030] Specifically, polyimide resin, as the matrix material, has a low coefficient of thermal expansion that matches the thermal expansion characteristics of silver-coated ceramic powder, reducing interfacial stress caused by temperature changes. Silver nanowires interlock within the matrix to form continuous conductive pathways, compensating for the high contact resistance of the silver-coated ceramic powder. Silicon carbide whiskers are interspersed between the resin and fillers, enhancing the material's shear strength through bridging. Antioxidants are adsorbed on the surface of the silver material, blocking oxygen from contacting the silver and thus maintaining the stability of the conductive network. The synergistic effect of these components ensures the conductive adhesive maintains stable resistivity even at high temperatures.

[0031] This application further proposes that the particle size of the silver-coated ceramic powder is 1-5 μm; the ceramic particles include at least one of Al2O3 and SiC; and the thickness of the silver coating is 0.1-0.5 μm.

[0032] Optionally, the particle size of the ceramic particles can be 1μm, 2μm, 3μm, 4μm, 5μm, or any value between 1 and 5μm; the thickness of the silver plating layer can be 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, or any value between 0.1 and 0.5μm.

[0033] The 1-5 μm particle size of the ceramic particles refers to the size range of the substrate material constituting the silver-coated ceramic powder. This size range can be controlled by ball milling and grading processes to balance specific surface area and filling density, ensuring efficient formation of the conductive network. The inclusion of at least one of Al2O3 and SiC in the ceramic particles indicates the selection of a high-hardness, high-thermal-conductivity ceramic material as the substrate material. Such materials reduce the difference in thermal expansion coefficients with the resin matrix. The 0.1-0.5 μm thickness of the silver plating layer refers to the coverage of the metal coating layer. This can be achieved through the coordinated control of silver nitrate concentration and reaction time in a chemical silver plating process, or through electroplating. This thickness range ensures conductive continuity while preventing plating cracking.

[0034] Specifically, in preparing silver-coated ceramic powder, Al2O3 or SiC particles of a specific size are selected as the substrate, such as 3μm Al2O3 microspheres, to ensure uniform dispersion within the resin matrix. During electroless silver plating, controlling the plating thickness to approximately 0.3μm ensures complete silver coating of the ceramic surface, forming a conductive path, while preventing excessively thick plating from peeling off due to thermal stress at high temperatures. Treatment of the ceramic particles with KH-550 silane coupling agent enhances the interfacial bonding with the polyimide resin, thereby reducing interfacial stress concentration caused by differences in thermal expansion.

[0035] This application further proposes that the matrix material of the polyimide resin is acetylene-terminated polyimide, and the molecular weight range of the acetylene-terminated polyimide can be set to 5000-20000.

[0036] Specifically, when acetylene-terminated polyimide is used as the resin matrix, the acetylene groups at the ends of its molecular chains undergo a thermal cross-linking reaction during curing, forming a dense three-dimensional cross-linked network. This structure can significantly reduce the coefficient of thermal expansion of the resin matrix, for example, reducing the difference in thermal stress between the resin and the silver-coated ceramic filler at high temperatures. Simultaneously, the high cross-linking density formed after curing of KH-500S resin helps improve the thermal decomposition resistance of the matrix material and prevents displacement of conductive fillers caused by resin softening under high-temperature conditions.

[0037] This application further proposes that: the total silver content in the conductive adhesive is 34.75-59%; and the volume resistivity of the conductive adhesive is not higher than 1×10⁻⁶. -4 Ω·cm; the thin-film resistance of the conductive adhesive is not higher than 200Ω / sq; the resistance change rate of the conductive adhesive after 1000h at 300℃ is not higher than 5%; the thermal decomposition temperature of the conductive adhesive is not lower than 500℃; the shear strength of the conductive adhesive is not lower than 15MPa; the elongation at break of the conductive adhesive is not lower than 10%.

[0038] Optionally, the total silver content in the conductive adhesive can be 34.75%, 35%, 36%, 37%, 38%, 9%, 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, or 59%, or any value between 34.75% and 59%; the volume resistivity of the conductive adhesive can be 0.2 × 10⁻⁶. -4 Ω·cm, 0.4×10 -4 Ω·cm, 0.6×10 -4 Ω·cm, 0.8×10 -4 Ω·cm, 1×10 -4 Ω·cm, or not higher than 1×10 -4The resistance of the conductive adhesive sheet can be any value in Ω·cm; the resistance of the conductive adhesive sheet can be 20Ω / sq, 40Ω / sq, 60Ω / sq, 80Ω / sq, 100Ω / sq, 120Ω / sq, 140Ω / sq, 160Ω / sq, 180Ω / sq, 200Ω / sq, or any value not exceeding 200Ω / sq.

[0039] Secondly, this application also provides a method for preparing the above-mentioned low-resistance, high-temperature resistant conductive adhesive, comprising: mixing silver-coated ceramic powder, silver nanowires, silicon carbide whiskers, and polyimide resin to obtain the adhesive.

[0040] Specifically, when the four types of materials are mixed in a certain proportion, silver-coated ceramic powder serves as the main filler, providing basic conductivity. Silver nanowires form a continuous conductive network through overlapping, silicon carbide whiskers are interspersed between the fillers to enhance structural rigidity, and polyimide resin acts as a binder phase to encapsulate and fix the filler system. During the mixing process, a combination of mechanical stirring and ultrasonic dispersion is used to ensure that the silver nanowires are uniformly distributed on the surface of the ceramic powder, and the silicon carbide whiskers are oriented within the resin matrix, ultimately forming a composite conductive colloid with an interpenetrating network structure.

[0041] This application further proposes to obtain silver-coated ceramic powder by subjecting ceramic particles to a series of coarsening treatments, chemical silver plating treatments, and coupling agent treatments.

[0042] The roughening process includes etching the surface of ceramic particles using a surface etchant; the surface etchant includes one of hydrofluoric acid and an alkaline solution, wherein the alkaline solution includes sodium hydroxide.

[0043] Chemical silver plating involves reacting roughened ceramic particles with a silver plating solution at 40-60℃ and pH 10-12 for 2-4 hours. The total mass of the silver plating solution is 100%, including 8-12 g / L AgNO3 97-99% and polyethylene glycol 1-3%.

[0044] Optionally, the temperature for chemical silver plating can be 40℃, 45℃, 50℃, 55℃, 60℃, or any value between 40℃ and 60℃; the pH value can be 10, 11, 12, or any value between 10℃ and 12; and the reaction time can be 2h, 3h, 4h, or any value between 2h and 4h.

[0045] Optionally, the concentration of AgNO3 can be 8 g / L, 9 g / L, 10 g / L, 11 g / L, 12 g / L, or any value between 8 and 12 g / L; optionally, the amount of AgNO3 can be 97%, 98%, 99%, or any value between 97 and 99%; the amount of polyethylene glycol can be 1%, 2%, 3%, or any value between 1 and 3%.

[0046] The silane coupling agent treatment involves treating the chemically silver-plated ceramic particles with a silane coupling agent at 80-100℃ for 30-60 minutes; the silane coupling agent includes KH-550.

[0047] The roughening treatment involves increasing the surface roughness of ceramic particles through chemical etching. Specifically, hydrofluoric acid or alkaline solutions can be used to etch the surface of Al2O3 or SiC particles, forming a microscopic pit structure to enhance the adhesion of the subsequent silver layer. Chemical silver plating involves depositing a silver coating on the surface of ceramic particles through a reduction reaction in an alkaline environment. This can be achieved using a plating solution containing silver nitrate and polyethylene glycol, with the reaction time controlled at 80-100℃ to ensure a uniform silver layer covering the ceramic particles. Silane coupling agent treatment utilizes the amino groups in KH-550 molecules to form chemical bonds with the silver layer surface, while simultaneously cross-linking with the polyimide matrix during resin curing, thereby improving the interfacial bonding strength.

[0048] Specifically, after etching with hydrofluoric acid, ceramic particles develop a micron-scale rough structure on their surface. Subsequently, a continuous silver layer is formed through a reduction reaction of silver nitrate in a silver plating solution. Polyethylene glycol in the plating solution acts as a dispersant to inhibit the agglomeration of silver particles. After silver plating, the particles are treated with a silane coupling agent, forming an organic functional group layer on their surface. When subsequently mixed with polyimide resin, these functional groups can chemically react with the resin molecular chains, effectively reducing the difference in thermal expansion coefficients between the filler and the matrix.

[0049] This application further proposes a method of mixing pyromellitic anhydride, diamine monomer, and a polar solvent, followed by a polycondensation reaction to obtain a polyamic acid solution; then, the polyamic acid solution is subjected to imidization curing to obtain the polyimide resin; and the method satisfies at least one of the following conditions: The diamine monomer is a diamine monomer containing a phenylacetylene group; The polar solvent includes DMAc (N,N-dimethylacetamide). The molar ratio of the pyromellitic anhydride to the diamine monomer is 1:0.95-1.05; The solid content of the polyamic acid solution is 10-15%; Optionally, the solid content of the polyamic acid solution can be 10%, 11%, 12%, 13%, 14%, 15%, or any value between 10% and 15%.

[0050] The imidization curing is carried out by gradient heating, and the gradient heating conditions are as follows: heating from room temperature to 140-160℃ and holding for 0.9-1.1h; heating to 240-260℃ and holding for 1.9-2.1h; heating to 290-310℃ and holding for 0.9-1.1h.

[0051] Optionally, during the gradient heating process: in the first stage, the final temperature can be 140℃, 142℃, 144℃, 146℃, 148℃, 150℃, 152℃, 154℃, 156℃, 158℃, 160℃, or any value between 140℃ and 160℃; the holding time in the first stage can be 0.9h, 1h-1.1h, or any value between 0.9h and 1.1h; in the second stage, the final temperature can be 24℃. 0℃, 242℃, 244℃, 246℃, 248℃, 250℃, 252℃, 254℃, 256℃, 258℃, 262℃, or any value between 240℃ and 260℃; in the third stage, the endpoint temperature can be 290℃, 292℃, 294℃, 296℃, 98℃, 300℃, 302℃, 304℃, 306℃, 308℃, 310℃, or any value between 290℃ and 310℃.

[0052] Thirdly, this application provides a method for using a low-resistance, high-temperature resistant conductive adhesive, which involves grinding conductive adhesive particles and then placing them on a substrate, arranging them in a magnetic field, and then curing them at a low temperature.

[0053] Specifically, conductive adhesive particles are ground and uniformly distributed on the substrate surface. Under the influence of a magnetic field, silver nanowires and silicon carbide whiskers form a continuous conductive path along the magnetic field lines. Subsequently, by controlling the curing temperature and pressure, the polyimide resin is fully cross-linked, ultimately forming a three-dimensional structure with an oriented conductive network. In this process, the magnetic field alignment reduces random distribution defects of the conductive filler, while low-temperature curing suppresses the difference in thermal expansion between the resin and the filler.

[0054] Through the above-mentioned technical features, this application significantly improves the structural stability of conductive adhesive in high temperature and high humidity environments, reduces resistivity fluctuations caused by differences in thermal expansion, and enhances the continuity of conductive pathways through directional alignment technology, enabling the conductive adhesive to maintain stable electrical performance in photovoltaic modules over a long period of time.

[0055] This application further proposes that conductive adhesive particles are ground and then placed on a substrate, oriented by a magnetic field, and then cured at low temperature, satisfying at least one of the following conditions: The particle size D50 of the ground conductive adhesive particles is no greater than 3μm; The magnetic field strength for the magnetic field orientation treatment is 50-100V / mm, and the treatment time is 10-20min; The conditions for low-temperature curing are: hot pressing at 150-200℃ for 10-30 minutes, pressure of 15-25MPa, and control of resin viscosity at 100-300cP.

[0056] Optionally, the particle size D50 of the conductive adhesive particles can be 1μm, 2μm, 3μm, or any value between 1 and 3μm.

[0057] The magnetic field strength can be 50V / mm, 60V / mm, 70V / mm, 80V / mm, 90V / mm, 100V / mm, or any value between 50-100V / mm; the magnetic field duration can be 10min, 12min, 14min, 16min, 18min, 20min, or any value between 10-20min.

[0058] Optionally, the temperature for hot-press curing in low-temperature curing can be 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, or any value between 150℃ and 200℃; the hot-press curing time can be 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, or any value between 10 min and 20 min; the pressure can be 15 MPa, 16 MPa, 17 MPa, 18 MPa, 19 MPa, 20 MPa, 21 MPa, 22 MPa, 23 MPa, 24 MPa, 25 MPa, or any value between 15 MPa and 25 MPa; and the process is controlled.

[0059] The particle size D50 of no more than 3μm refers to the upper limit of the median particle size of the conductive adhesive particles. This can be controlled by a three-roll mill. Smaller particle sizes help improve the uniformity of particle dispersion on the substrate surface. The magnetic field strength of 50-100V / mm refers to the range of applied electromagnetic field strength. This can be adjusted using an electromagnetic generator. The magnetic field causes the conductive filler to align in a specific direction, forming a continuous conductive network. The hot-pressing temperature of 150-200℃ under low-temperature curing conditions refers to a range lower than the conventional polyimide curing temperature. This can be achieved using a hot-pressing device with segmented heating. Lower temperatures reduce the risk of resin thermal decomposition and lower interfacial thermal stress.

[0060] Specifically, the conductive adhesive particles are ground to a controlled particle size range, reducing agglomeration when spread on the substrate surface. Subsequently, a magnetic field treatment causes the silver nanowires and silver-coated ceramic powder to align along the magnetic field direction, forming a continuous conductive pathway. During low-temperature curing, the resin fills the gaps between particles under pressure, forming a dense structure. Simultaneously, the relatively low curing temperature prevents interfacial delamination due to differences in thermal expansion.

[0061] This application further proposes that photovoltaic modules include low-resistance, high-temperature resistant conductive adhesives.

[0062] Among them, the low-resistance, high-temperature resistant conductive adhesive refers to a composite material with silver-coated ceramic powder, silver nanowires, silicon carbide whiskers, and polyimide resin as the main components. Specifically, silver-coated Al2O3 or SiC ceramic particles can be used as conductive fillers, and the conductivity can be controlled by adjusting the thickness of the silver plating layer. The polyimide resin serves as the matrix material and adopts an acetylene-terminated structure to improve its temperature resistance.

[0063] Specifically, this conductive adhesive constructs a three-dimensional conductive network through the synergistic effect of silver-coated ceramic powder and silver nanowires. Silicon carbide whiskers enhance mechanical strength, and the polyimide resin matrix maintains structural integrity at high temperatures. In photovoltaic modules, the conductive adhesive is applied to the electrode connection points. Its low resistance ensures efficient current transmission, and its high-temperature resistance adapts to fluctuations in module operating temperature.

[0064] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0065] Example 1 This embodiment provides a low-resistance, high-temperature resistant conductive adhesive: Based on the total mass of conductive adhesive raw materials as 100%, it includes: 60% silver-coated ceramic powder, 10% silver nanowires, 1% silicon carbide whiskers, 28.9% polyimide resin, and 0.1% BHT.

[0066] The matrix material of the polyimide resin is acetylene-terminated polyimide with a molecular weight of 5000; the raw material of the silver-coated ceramic powder is Al2O3 particles with a particle size of 1μm, and the thickness of the silver plating layer is 0.3μm.

[0067] This embodiment provides a method for preparing a low-resistance, high-temperature resistant conductive adhesive, the specific steps of which are as follows: 1.1 Preparation of silver-coated ceramic powder Roughening treatment: The surface of Al2O3 particles was etched with hydrofluoric acid at a temperature of 40℃ for 2 minutes. Chemical silver plating: The roughened Al2O3 particles were reacted with a silver plating solution at 50°C and pH 11 for 3 hours.

[0068] The total mass of the silver plating solution is 100, which includes: 8 g / L AgNO3 99% and polyethylene glycol 1%.

[0069] Coupling agent treatment: Al2O3 particles that have undergone chemical silver plating were reacted at 80℃ for 30h using KH-550.

[0070] The silver-coated ceramic powder obtained is as follows Figure 1 As shown.

[0071] 1.2 Preparation of polyimide resin Pyromellitic anhydride and 3,5-diaminophenylacetylene were mixed with DMAc at a molar ratio of 1:0.95 and subjected to a polycondensation reaction at 70°C for 5 hours to obtain a polyamic acid solution. The polyamic acid solution was then heated from room temperature to 150°C and held at this temperature for 1 hour; subsequently, the temperature was increased to 250°C and held for 2 hours; finally, the temperature was increased to 300°C and held for 1 hour. This yielded a polyimide resin, such as... Figure 2 As shown.

[0072] 1.3 Preparation of conductive adhesive The conductive adhesive is prepared by mixing silver-coated ceramic powder, silver nanowires, silicon carbide whiskers, polyimide resin, and antioxidants in a specific ratio. Figure 3 As shown.

[0073] This embodiment also provides a method for using a low-resistance, high-temperature resistant conductive adhesive, the steps of which are as follows: The particles were dispersed to a particle size of D50=2.5μm using a three-roll mill and coated onto a substrate. The conductive network was then optimized by magnetic field orientation alignment (field strength of 75V / mm, action time of 15 minutes).

[0074] Low-temperature curing: Hot-press curing at 175℃ for 20 minutes at a pressure of 20MPa promotes resin cross-linking and filler bonding. During the low-temperature curing process, the viscosity of the conductive agent system is controlled at 200cP.

[0075] Example 2 This embodiment provides a low-resistance, high-temperature resistant conductive adhesive: Based on the total mass of conductive adhesive raw materials as 100%, it includes: 45% silver-coated ceramic powder, 20% silver nanowires, 2% silicon carbide whiskers, 33% polyimide resin, and 0.5% BHT.

[0076] The matrix material of the polyimide resin is acetylene-terminated polyimide with a molecular weight of 20,000; the raw material of the silver-coated ceramic powder is Al2O3 particles with a particle size of 5μm, and the thickness of the silver plating layer is 0.3μm.

[0077] This embodiment provides a method for preparing a low-resistance, high-temperature resistant conductive adhesive, the specific steps of which are as follows: 1.1 Preparation of silver-coated ceramic powder Roughening treatment: The surface of Al2O3 particles was etched with hydrofluoric acid at a temperature of 60℃ for 2 minutes. Chemical silver plating: The roughened Al2O3 particles were reacted with a silver plating solution at 50°C and pH 11 for 3 hours.

[0078] The total mass of the silver plating solution is 100, which includes: 12 g / L AgNO3 97% and polyethylene glycol 3%.

[0079] Coupling agent treatment: Al2O3 particles that have undergone chemical silver plating were reacted at 100℃ for 60h using KH-550.

[0080] 1.2 Preparation of polyimide resin Pyromellitic anhydride and 3,5-diaminophenylacetylene were mixed with DMAc at a molar ratio of 1:1.05 and subjected to a polycondensation reaction at 80°C for 120 min to obtain a polyamic acid solution. The polyamic acid solution was then heated from room temperature to 150°C and held at that temperature for 1 h; subsequently, the temperature was increased to 250°C and held at that temperature for 2 h; and then increased to 300°C and held at that temperature for 1 h to obtain a polyimide resin.

[0081] 1.3 Preparation of conductive adhesive The silver-coated ceramic powder, silver nanowires, silicon carbide whiskers, polyimide resin, and antioxidants are mixed in a certain proportion to obtain the product.

[0082] This embodiment also provides a method for using a low-resistance, high-temperature resistant conductive adhesive, the steps of which are as follows: The particles were dispersed to a particle size of D50=2μm using a three-roll mill and coated onto a substrate. The conductive network was then optimized by magnetic field orientation alignment (field strength of 50V / mm, action time of 10 minutes).

[0083] Low-temperature curing: Hot-press curing at 150℃ for 30 minutes at a pressure of 20MPa promotes resin cross-linking and filler bonding. During the low-temperature curing process, the viscosity of the conductive agent system is controlled at 250cP.

[0084] Example 3 This embodiment provides a low-resistance, high-temperature resistant conductive adhesive: Based on the total mass of conductive adhesive raw materials as 100%, it includes: 55% silver-coated ceramic powder, 20% silver nanowires, 2% silicon carbide whiskers, 22.5% polyimide resin, and 0.5% BHT.

[0085] The matrix material of the polyimide resin is acetylene-terminated polyimide with a molecular weight of 20,000; the raw material of the silver-coated ceramic powder is Al2O3 particles with a particle size of 5μm, and the thickness of the silver plating layer is 0.3μm.

[0086] This embodiment provides a method for preparing a low-resistance, high-temperature resistant conductive adhesive, the specific steps of which are as follows: 1.1 Preparation of silver-coated ceramic powder Roughening treatment: The surface of Al2O3 particles was etched with hydrofluoric acid at a temperature of 60℃ for 2 minutes. Chemical silver plating: The roughened Al2O3 particles were reacted with a silver plating solution at 50°C and pH 11 for 3 hours.

[0087] The total mass of the silver plating solution is 100, which includes: 12 g / L AgNO3 97% and polyethylene glycol 3%.

[0088] Coupling agent treatment: Al2O3 particles that have undergone chemical silver plating were reacted at 100℃ for 60h using KH-550.

[0089] 1.2 Preparation of polyimide resin Pyromellitic anhydride and 3,5-diaminophenylacetylene were mixed with DMAc at a molar ratio of 1:1.05 and subjected to a polycondensation reaction at 80°C for 120 min to obtain a polyamic acid solution. The polyamic acid solution was then heated from room temperature to 150°C and held at that temperature for 1 h; subsequently, the temperature was increased to 250°C and held at that temperature for 2 h; and then increased to 300°C and held at that temperature for 1 h to obtain a polyimide resin.

[0090] 1.3 Preparation of conductive adhesive The silver-coated ceramic powder, silver nanowires, silicon carbide whiskers, polyimide resin, and antioxidants are mixed in a certain proportion to obtain the product.

[0091] This embodiment also provides a method for using a low-resistance, high-temperature resistant conductive adhesive, the steps of which are as follows: The particles were dispersed to a particle size of D50=2μm using a three-roll mill and coated onto a substrate. The conductive network was then optimized by magnetic field orientation alignment (field strength of 50V / mm, action time of 10 minutes).

[0092] Low-temperature curing: Hot-press curing at 150℃ for 30 minutes at a pressure of 20MPa promotes resin cross-linking and filler bonding. During the low-temperature curing process, the viscosity of the conductive agent system is controlled at 250cP.

[0093] Comparative Example 1 This comparative example provides a conventional conductive adhesive: The conductive particles are pure silver particles. The silver content is 85%. The resin material is epoxy resin.

[0094] The conductive adhesive has a Tg point of 85℃ and can withstand a temperature of 80℃ for a long time.

[0095] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the silver-coated ceramic powder was replaced with silver-coated copper particles, and the silver content was 50%. After long-term damp heat aging, there is a potential difference between copper and silver, the silver is corroded, the resistance of the conductive adhesive increases, and the change rate is 300%.

[0096] Comparative Example 3 The difference between Comparative Example 2 and Example 1 is that the silver-coated ceramic powder was replaced with conductive ceramic particles, the silver content was 15%, and the volume resistivity was 16.5%. The conductive adhesive had less contact with silver powder and a volume resistivity of 200 Ω·cm.

[0097] The performance information of the conductive adhesives provided in the examples and comparative examples is shown in Table 1.

[0098] Table 1. Conductive Adhesive Performance Information

[0099] As shown in Table 1: Silver content: Examples 1-3: Calculated based on the previously established model (silver content in silver-coated ceramic powder approximately 42.15% + percentage of silver nanowires). The silver content in all examples is significantly lower than that in Comparative Example 1.

[0100] Comparative Example 2: The silver content of the silver-coated copper particles is 50%, but its silver layer is easily corroded.

[0101] Comparative Example 3: Silver comes from only 20% of the silver nanowires, which is the lowest silver content, but it cannot form an effective conductive network.

[0102] Volume resistivity: Examples 1-3: All reached extremely low levels (10 -5 The resistance is on the same order of magnitude and very close to each other, demonstrating the adjustability and effectiveness of the formulation. The slight differences stem from the degree of optimization of the conductive network structure. Higher silver nanowire content tends to result in lower resistance, but Example 1 exhibits the lowest resistance due to the highest concentration of silver-coated powder and abundant contact points.

[0103] Comparative Example 1: Pure silver filler has the lowest resistivity, but the highest cost.

[0104] Comparative Example 2: Copper coated with silver has decent conductivity, but not as good as pure silver, so its resistivity is slightly higher.

[0105] Comparative Example 3: The ceramic particles are non-conductive, and a small amount of silver nanowires cannot form a continuous circuit. The resistivity is extremely high, and the process is completely ineffective.

[0106] Thermal decomposition temperature / long-term temperature resistance: Examples 1-3: Core Advantages. Polyimide resins, especially acetylene-terminated crosslinked types, have thermal decomposition temperatures far exceeding 500°C, thus achieving long-term temperature resistance up to 300°C.

[0107] Comparative Examples 1-3: The thermal decomposition temperature of epoxy resin matrix is ​​usually 300-400℃, and the glass transition temperature is even lower. Therefore, the long-term temperature resistance is limited to about 80℃, which is much lower than that of the present invention.

[0108] Mechanical properties: Examples 1-3: The polyimide matrix itself has high strength and toughness, and with the reinforcement of silicon carbide whiskers, it exhibits excellent mechanical properties.

[0109] Comparative Examples 1-2: The mechanical properties of the epoxy resin matrix are acceptable, but not as good as those of high-performance polyimide.

[0110] Comparative Example 3: A large amount of insulating ceramic filler disrupted the continuity of the matrix, resulting in the worst mechanical properties.

[0111] Aging resistance: Examples 1-3: The excellent stability of polyimide, combined with the effect of antioxidants, ensures stable performance after high-temperature aging.

[0112] Comparative Example 1: Epoxy resin is easily degraded under high temperature and high humidity.

[0113] Comparative Example 2: Electrochemical corrosion is a fatal flaw, leading to a sharp deterioration in performance.

[0114] Comparative Example 3: The conductive network itself is imperfect, and any environmental change may cause it to fail.

[0115] Cost reduction extent: Based on the cost of the pure silver epoxy conductive adhesive in Comparative Example 1. Examples 1-3: The amount of silver used was significantly reduced. Although polyimide resin is more expensive than epoxy resin, the overall cost still saw a significant reduction of ~44-50%.

[0116] Comparative Example 2: Costs were reduced, but at the cost of unstable performance.

[0117] Comparative Example 3: The cost reduction was the largest, but the product was unusable due to excessively high resistance and had no practical value.

[0118] In summary, the present invention (Examples 1-3) has successfully achieved a significant reduction in silver content and cost while comprehensively surpassing traditional conductive adhesives (Comparative Example 1) and other alternatives (Comparative Examples 2 and 3) in terms of overall performance (conductivity, temperature resistance, mechanical properties, and reliability), especially in terms of high-temperature reliability.

[0119] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0120] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A low-resistance, high-temperature resistant conductive adhesive, characterized in that, Based on the total mass of the raw materials of the conductive adhesive being 100%, it includes: 45-60% silver-coated ceramic powder, 10-20% silver nanowires, 1-2% silicon carbide whiskers, 20-35% polyimide resin, and 0.1-0.5% antioxidant; The matrix material of the polyimide resin is acetylene-terminated polyimide; The antioxidants include BHT.

2. The low-resistance, high-temperature resistant conductive adhesive according to claim 1, characterized in that, The silver-coated ceramic powder satisfies at least one of the following conditions: a. The raw material for the silver-coated ceramic powder is ceramic particles, and the particle size of the ceramic particles is 1-5μm; The ceramic particles include at least one of Al2O3 and SiC; b. The particle size of the silver-coated ceramic powder is 1-10 μm; c. The thickness of the silver coating on the silver-coated ceramic powder is 0.1-0.5 μm.

3. The low-resistance, high-temperature resistant conductive adhesive according to claim 1, characterized in that, The molecular weight of the acetylene-terminated polyimide is 5000-20000.

4. The low-resistance, high-temperature resistant conductive adhesive according to any one of claims 1-3, characterized in that, At least one of the following conditions must be met: d. The total silver content in the conductive adhesive is 34.75-59%; e. The volume resistivity of the conductive adhesive is not higher than 1×10⁻⁶. -4 Ω·cm; f. The sheet resistance of the conductive adhesive is not higher than 200Ω / sq; g. The resistance change rate of the conductive adhesive after 1000 hours at 300℃ is no higher than 5%; h. The thermal decomposition temperature of the conductive adhesive is not lower than 500℃; i. The shear strength of the conductive adhesive is not less than 15 MPa; j. The elongation at break of the conductive adhesive is not less than 10%.

5. A method for preparing a low-resistance, high-temperature resistant conductive adhesive according to any one of claims 1-4, characterized in that, include: The silver-coated ceramic powder, the silver nanowires, the silicon carbide whiskers, the polyimide resin, and the antioxidant are mixed together to obtain the product.

6. The preparation method according to claim 5, characterized in that, The ceramic particles are subjected to a series of treatments, including roughening, chemical silver plating, and coupling agent treatment, to obtain the silver-coated ceramic powder; and the powder satisfies at least one of the following conditions: A. The roughening treatment includes: using a surface etchant to perform surface etching on the ceramic particles; the surface etchant includes one of hydrofluoric acid and an alkaline solution, wherein the alkaline solution includes sodium hydroxide; B. The chemical silver plating process includes: reacting the roughened ceramic particles with a silver plating solution at 40-60°C and pH 10-12 for 2-4 hours; Based on a total mass of 100% for the silver plating solution, it comprises: 8-12 g / L AgNO3 97-99%, and polyethylene glycol 1-3%; C. The coupling agent treatment includes: treating the ceramic particles that have undergone the chemical silver plating treatment with a silane coupling agent at 80-100°C for 30-60 minutes; The silane coupling agent includes KH-550.

7. The preparation method according to claim 6, characterized in that, The preparation method of the polyimide resin includes: A polyamic acid solution is obtained by mixing pyromellitic anhydride, a diamine monomer, and a polar solvent and carrying out a polycondensation reaction; the polyamic acid solution is then subjected to imidization curing to obtain the polyimide resin; and at least one of the following conditions is met: D. The diamine monomer is a diamine monomer containing a phenylacetylene group; E. The polar solvent includes DMAc; F. The molar ratio of the pyromellitic anhydride and the diamine monomer is 1:0.95-1.05; G. The solid content of the polyamic acid solution is 10-15%; H. The conditions for the polycondensation reaction are: under nitrogen protection, reaction at 60-80℃ for 4-6 hours; I. The imidization curing is carried out by gradient heating, and the gradient heating conditions are as follows: First stage, heating from room temperature to 140-160℃ and holding for 0.9-1.1h; Second stage, heating to 240-260℃ and holding for 1.9-2.1h; Third stage, heating to 290-310℃ and holding for 0.9-1.1h.

8. A method of using the low-resistance, high-temperature resistant conductive adhesive according to any one of claims 1-4, characterized in that, The conductive adhesive particles are ground and then placed on a substrate, oriented by a magnetic field, and then cured at low temperature.

9. The method of use according to claim 8, characterized in that, At least one of the following conditions must be met: I. The particle size D50 of the ground conductive adhesive particles is no greater than 3μm; II. The magnetic field strength for the magnetic field orientation arrangement treatment is 50-100V / mm, and the treatment time is 10-20min; III. The conditions for low-temperature curing are: hot pressing at 150-200℃ for 10-30 minutes, pressure of 15-25MPa, and controlling the viscosity of the conductive agent system to 100-300cP.

10. A photovoltaic module, characterized in that, Including the low-resistance, high-temperature resistant conductive adhesive as described in any one of claims 1-4.

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