A kind of low contact resistance heat curing conductive adhesive and preparation method thereof

Abstract

The present invention discloses a low contact resistance heat-curing conductive adhesive and a preparation method thereof, and belongs to the technical field of solar cells. The heat-curing conductive adhesive of the present invention is composed as follows: (A) silver powder, silver-coated copper powder and a mixture of the two powders, (B) epoxy monomer and modified epoxy resin, (C) curing agent, (D) solvent, (E) rheological additive, and (F) phenolic hydroxyl compound. The present invention can realize a low contact resistance conductive adhesive that cures quickly at 200°C through the above composition, and can also achieve the goals of low volume resistance, moisture resistance, heat resistance, and good storage stability required for fine grid metallization electrodes for heterojunction batteries.

Description

Technical Field

[0001] The invention relates to a low-contact-resistance heat-curing conductive adhesive and a preparation method thereof, belonging to the technical field of solar cells. Background Art

[0002] Conductive thermosetting paste is widely used in touch display panels and electronic components by forming conductive electrode lines on the surface of flexible substrates such as PET, PI and other films, PCT boards, etc. through screen printing, dispensing wiring, micro-concave coating, and embossing wiring. The use of such thermosetting conductive paste only requires good adhesion and clear requirements for the lateral current conduction ability. Generally speaking, the smaller the body resistance of the wiring electrode formed by the conductive paste after thermal curing, the easier it is for the current to pass, but the longitudinal current conduction ability is not required.

[0003] In specific areas such as metallized heterojunction solar cells, conductive thermal curing paste is applied on the front and back of the monocrystalline silicon TCO blue film by screen printing to form metallized electrodes, thereby extracting the photocurrent. The light conversion efficiency of a heterojunction solar cell is inversely proportional to the series resistance Rs. The smaller the Rs, the higher the light conversion efficiency. Rs is mainly composed of the volume resistance of the metallized electrode itself and the longitudinal contact resistance of the interface between the metallized electrode grid line and the TCO blue film. Therefore, the thermal curing conductive paste used in heterojunction solar cells needs to have good current conduction capability at the interface between the longitudinal wiring electrode and the substrate surface.

[0004] The technical patent documents of the thermosetting conductive adhesive composition have been published: CN 111117539 A, CN 110136863A, and it is known that the composition thereof includes silver powder, silver-coated powder, and alloy powder as conductive powder, and epoxy resin monomer / modified epoxy resin and epoxy curing agents such as isocyanate, imidazole, amine, and acid anhydride as components of the thermosetting composition.

[0005] How to reduce the contact resistance is not mentioned in the prior art patent documents. Summary of the invention

[0006] [Technical problem to be solved by the invention]

[0007] As the requirements for heterojunction solar cells become increasingly stringent, the electrical performance centerline resistance, contact resistance, and reliability of moisture and heat resistance are all technical points that heterojunction thermosetting conductive pastes need to overcome.

[0008] The present invention is completed to solve such technical points, and its purpose is to provide a low contact resistance thermosetting conductive adhesive composition. Based on the existing technical points, such as using silver powder, silver-coated copper powder and alloy powder, combined with epoxy resin, an excellent low contact resistance, low volume resistance, and moisture and heat resistance thermosetting conductive adhesive for fine-grid metallized heterojunction batteries is obtained.

[0009] [Technical means used to solve the problem]

[0010] In order to solve the above problems, the present invention provides a thermosetting conductive adhesive, which is composed of (A) conductive powder, (B) epoxy resin, (C) curing agent, (D) solvent, (E) rheological additive, and (F) phenolic hydroxyl compound by adding phenolic hydroxyl compound as a component for reducing contact resistance.

[0011] In one embodiment of the present invention, the conductive powder (A) used is silver powder, silver-coated copper powder or a mixture thereof, and the powder may be ball powder or flake powder.

[0012] In one embodiment of the present invention, the (B) epoxy resin is one or at least one of alicyclic epoxy resin, bisphenol A epoxy resin, acrylic modified epoxy resin, polyester modified epoxy resin, and polyurethane modified epoxy resin.

[0013] In one embodiment of the present invention, the alicyclic epoxy resin can be CY-184 or 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexylcarboxylate (2021P). GY298.

[0014] In one embodiment of the present invention, the epoxy resin (B) may be CY-184, or CY-184 and GY 298 combination.

[0015] In one embodiment of the present invention, the curing agent (C) is 1,3-di-tert-butyl imidazole tetrafluoroborate. Its structure is shown in formula (1):

[0016]

[0017] Among them, the two tert-butyl groups in the structure of the curing agent compound can bring greater steric hindrance. The network-like cross-linked polymer formed after thermal curing with the epoxy monomer can improve the brittleness of the epoxy resin. At the same time, it has the characteristic of strong oil solubility, so that the cured product can maintain good reliability in high temperature and high humidity environments.

[0018] In one embodiment of the present invention, the (D) solvent is a common solvent for conductive paste, such as terpineol, diethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, etc., or a mixed solvent.

[0019] In one embodiment of the present invention, the (D) solvent is specifically a mixed solvent of diethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, dimethyl malonate, alcohol ester dodecahydrate, ethylene glycol butyl ether, and triethylene glycol methyl ether, and the volume ratio is fixed at 4:1:1:0.5:2:1.5.

[0020] In one embodiment of the present invention, the (E) rheological additive is a combination of any one or more of a thixotropic agent, a leveling agent, a dispersant, and a lubricant.

[0021] In one embodiment of the present invention, the (E) rheological additive is specifically a combination of BYK111, TEGO410 and RM2020, with a mass ratio of 1:2:2.

[0022] In one embodiment of the present invention, the structure of the (F) phenolic hydroxy compound is as shown in formula (2):

[0023]

[0024] Wherein, R is a C1-C5 alkyl group, a C1-C5 alkyl group substituted with a hydroxyl group, or a C1-C5 alkyl group substituted with a C2-C6 ester group, and the Arabic numerals in the formula are the positions of the hydroxyl groups, wherein the number of the hydroxyl groups is 2-5.

[0025] In one embodiment of the present invention, the hydroxy-substituted C1-C5 alkyl group is C1-C5 alkyl-OH. 2 CH 2 OH, -CH 2 OH.

[0026] In one embodiment of the present invention, the C1-C5 alkyl substituted with a C2-C6 ester group is C1-C5 alkyl-O-COR', and R' is independently selected from C1-5 alkyl. 2 OC(=O)CH 3 、-CH 2 CH 2 OC(=O)CH 3 .

[0027] In one embodiment of the present invention, the following are mixed in proportions by weight: (A) 90-95 parts of conductive powder, (B) 1-5 parts of epoxy resin, (C) 0.1-0.5 parts of curing agent, (D) 1-5 parts of solvent, (E) 0.1-1 parts of rheological additive, and (F) 0.1-0.5 parts of phenolic hydroxyl compound.

[0028] In one embodiment of the present invention, the proportions by weight are: (A) 93 parts of conductive powder, (B) 3.5 parts of epoxy resin, (C) 0.3 parts of curing agent, (D) 2.4 parts of solvent, (E) 0.5 parts of rheological additive, and (F) 0.3 parts of phenolic hydroxyl compound.

[0029] In one embodiment of the present invention, (A) conductive powder is selected from any one or more of pure silver ①, pure silver ②, pure silver ③, silver-coated copper ①, silver-coated copper ②, silver-coated copper ③, and silver-coated copper ④.

[0030] In one embodiment of the present invention, (A) conductive powder is preferably silver-coated copper ③, silver-coated copper ④, a combination of pure silver ③ and pure silver ①, and a combination of pure silver ② and silver-coated copper ④.

[0031] In one embodiment of the present invention, the mass ratio of the combination of pure silver ③ and pure silver ① is 1.5:1.

[0032] In one embodiment of the present invention, the mass ratio of the combination of pure silver ② and silver-clad copper ④ is 1.5:1.

[0033] In one embodiment of the present invention, preferably, the thermosetting conductive adhesive is composed of (A) 93 parts of conductive powder, (B) 3.5 parts of epoxy resin, (C) 0.3 parts of curing agent, (D) 2.4 parts of solvent, (E) 0.5 parts of rheological additive, and (F) 0.3 parts of phenolic hydroxyl compound in proportion by weight; wherein (A) the conductive powder is a mixture of pure silver ③ and pure silver ① in a mass ratio of 56:37, silver-coated copper ③, silver-coated copper ④, or a mixture of pure silver ② / silver-coated copper ④ in a mass ratio of 56:37; (B) the epoxy resin is 0.3 parts of curing agent, (D) 2.4 parts of solvent, (E) 0.5 parts of rheological additive, and (F) 0.3 parts of phenolic hydroxyl compound. The resin is an alicyclic epoxy resin, or a combination of an alicyclic epoxy resin and a bisphenol A epoxy resin; (C) the curing agent is 1,3-di-tert-butyl imidazole tetrafluoroborate; (D) the solvent is a mixed solvent of diethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, dimethyl malonate, alcohol ester dodecahydrate, ethylene glycol butyl ether, and triethylene glycol methyl ether, with a volume ratio of 4:1:1:0.5:2:1.5; (E) the rheological additive is a combination of any one or more of a thixotropic agent, a leveling agent, a dispersant, and a lubricant; (F) the phenolic hydroxy compound is R is a C1-C5 alkyl group, a C1-C5 alkyl group substituted with a hydroxyl group, or a C1-C5 alkyl group substituted with a C2-6 ester group.

[0034] In one embodiment of the present invention, the preparation method of the above-mentioned thermosetting conductive adhesive comprises:

[0035] First, (B) epoxy resin, (D) solvent, (C) curing agent, (E) rheological additive, and (F) phenolic hydroxyl compound are fully dispersed under stirring of a mechanical stirrer to obtain an organic carrier; then (A) conductive powder is added and blended, and after stirring, it is fully ground with a three-roll grinder to obtain a thermosetting conductive adhesive.

[0036] The present invention also provides a method for reducing the contact resistance of the heat-curing conductive adhesive, which is to add a phenolic hydroxyl compound as a modifier to reduce the contact resistance.

[0037] In one embodiment of the present invention, the specific process of reducing the contact resistance of the thermosetting conductive adhesive is as follows: (B) epoxy resin and (D) solvent, (C) curing agent, (E) rheological additive, (F) phenolic hydroxyl compound are fully dispersed under stirring of a mechanical stirrer to obtain an organic carrier; then (A) conductive powder is added to blend, stirred and then fully ground with a three-roll grinder.

[0038] The present invention also provides an electrode containing the above-mentioned thermosetting conductive adhesive.

[0039] The present invention also provides application of the above-mentioned thermosetting conductive adhesive or the above-mentioned electrode in the field of solar cells.

[0040] Effects of the Invention

[0041] The present invention can realize a low contact resistance conductive adhesive that cures quickly at 200° C. through the above structure, and can also achieve the goals of low volume resistance, moisture resistance, heat resistance, and good storage stability required for fine grid metallization electrodes for heterojunction batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic diagram of a method for evaluating the toughening effect of different curing agents in the thermosetting conductive adhesive compositions of the examples and comparative examples of the present application.

[0043] Figure 2 It is a grid line pattern used for testing and evaluating the contact resistance between the thermosetting conductive adhesive and the TCO blue film in the embodiments and comparative examples of this application specification.

[0044] Explanation of symbols: 10 a laser grooved glass plate for coating conductive adhesive; 20 a laser grooved grid line pattern for contact resistance test and evaluation; 30 a laser grooved line resistance test and evaluation circuit pattern. DETAILED DESCRIPTION

[0045] In order to illustrate the present invention in more detail, the physical properties, contact resistance, and line resistance tests and evaluations of the conductive adhesives in the following examples and comparative examples are carried out as follows.

[0046] [(A) Silver powder, silver-coated copper powder and a mixture of the two]

[0047] According to the low contact resistance conductive adhesive composition of the present invention, the (A) silver powder, silver-coated copper powder and a mixture of the two powders can be used in different amounts and specifications to produce a conductive adhesive with low silver content and excellent conductivity.

[0048] The silver-coated copper powder in the present invention is a conductive powder obtained by coating a layer of silver film on the surface of the copper powder by a reduction plating method, a displacement plating method, etc. In addition, the silver coverage is calculated based on the mass of 100g of the silver-coated copper, wherein the silver content is at least greater than 10%. Too low silver content will have the risk of copper leakage, resulting in poor reliability of heterojunction solar cells.

[0049] The average particle size D50 of the silver powder of the present invention is preferably in the range of 0.3 to 5 μm, and the tap density is preferably in the range of 3 to 7 g / cm3. It can be a ball powder or a flake powder, or a combination thereof.

[0050] Specifically, when the silver powder is in the form of spherical powder, the particle size is preferably less than 1 μm. When the particle size is greater than 1 μm, the gap between the conductive powder and the TCO velvet surface cannot be tightly filled, thereby increasing the contact resistance. When the silver powder is in the form of flake powder, the preferred particle size is 2 to 3 μm. When the particle size D50 is less than 2 μm, the overlap area between the conductive powders is reduced, and the body resistance tends to increase. When the particle size D50 is greater than 3 μm, the requirements for fine line printing are not met, and there is a risk of silver powder blocking the screen. The conductive glue composed of the silver powder has poor ink absorption during screen printing, resulting in uneven metallized grid lines and increased difficulty in the lateral passage of current.

[0051] [(B) Epoxy monomer and modified epoxy resin]

[0052] The (B) epoxy monomer and modified epoxy resin used in the low contact resistance thermosetting conductive adhesive of the present invention can be selected from alicyclic epoxy monomers. In order to achieve good conductivity, modified epoxy resins with heat shrinkage can be listed. The preferred modified epoxy resin contains a polyester structure, or an acrylic and polyurethane structure.

[0053] The specific type and structure of the alicyclic epoxy monomer are not particularly limited, but the epoxy equivalent of the preferred epoxy resin monomer is in the range of 80 to 200 g / Eg, more preferably between 100 and 150 g / Eg. Such epoxy resin monomers can be purchased from the market, such as Daicel 2021P, Synasia S-06E, S-21, S-27, S-28, S-100, S-100A, S-101, S-221, Huntsman CY 184, CY 179-1, but not limited thereto.

[0054] Specific examples of heat shrinkable modified epoxy resins include: GY 298, DY 965, 695, A102, but not limited thereto. In order to obtain sufficient conductivity, the selected modified epoxy resin can be one or a combination thereof.

[0055] [(C) Curing agent]

[0056] The present invention innovatively uses 1,3-di-tert-butyl imidazole tetrafluoroborate as a curing agent for the epoxy system composition, and its amount can be added according to the epoxy equivalent in the composition. Excessive addition or small addition cannot achieve good conductivity. In addition, in order to formulate conductive adhesive compositions with different flexibility, according to different application scenarios, such as flexible substrate PET, isocyanate compounds can also be appropriately used in combination. The isocyanate compounds used are not specifically limited, and can be one or a combination of hexamethylene diisocyanate, isophorone diisocyanate, hydrogenated xylene diisocyanate, etc.

[0057] [(D) Solvent]

[0058] The solvent (D) is a common solvent for conductive paste, and its purpose is to adjust the viscosity and fluidity of the conductive adhesive. The type of the solvent is not specifically limited and can be one of terpineol, diethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, etc., or a mixed solvent.

[0059] [(E) Thixotropic agent, leveling agent, dispersant, lubricant composition]

[0060] The thixotropic agent, leveling agent, dispersant and lubricant composition can be added to the conductive adhesive in appropriate amounts according to specific application scenarios, and the usage amount accounts for 0.1 to 2 g (100 g of conductive adhesive) of the weight of the conductive adhesive. The preferred thixotropic agent is liquid or paste, and examples include BYK-410, BYK-R60, BYK-R607, RM-2020, etc. The leveling agent, dispersant and lubricant are common ink additives, and examples include alcohol ester dodecahydrate, TEGO 410, TEGO 270, EFKA 3600, BYK347, dimethyl silicone oil, squalane, and they can be used alone or in combination.

[0061] [(F) Phenol hydroxy compound]

[0062]

[0063] Wherein R is 1 to 5 alkyl groups or alkyl alcohols or alkyl esters, preferably -CH 2 CH 2 OH, -CH 2 OH, -CH 2 O(C=O)R', -CH 2 CH2 O(C=O)R', (R' is C1-5 alkyl).

[0064] The Arabic numerals in the formula are the positions of the hydroxyl groups, and the number of the hydroxyl groups can be 2 to 5. The preferred positions of the hydroxyl groups are 2, 3, and 4; more preferably, 3 and 4; the hydroxyl groups at other positions have little effect on the adhesion of the conductive adhesive, and the number of the hydroxyl groups is preferably 2 to 5; more preferably, 2 to 3; more hydroxyl groups may lead to excessive viscosity of the conductive adhesive, affecting printing.

[0065] There is no specific restriction on the amount of the phenolic hydroxy compound used. The preferred amount is 0.01-1% of the total weight of the conductive adhesive, and the more preferred amount is 0.02-0.5%. The appropriate amount helps to improve the adhesion between the conductive adhesive and the substrate while meeting the low contact resistance, and will not affect the viscosity of the conductive adhesive, thereby affecting the printability.

[0066] [Applications of low contact resistance thermosetting conductive adhesive]

[0067] The low contact resistance thermosetting conductive adhesive according to the present invention can be used for electronic components requiring high-precision electrode wiring, heterojunction solar cells, thin-film electrodes, electroluminescence, etc. The preferred application scenario is heterojunction solar cells, and is further suitable for use in the front and back fine grid metallization electrodes of heterojunction solar cells.

[0068] Testing and evaluation methods

[0069] [Evaluation method for toughness of conductive adhesive]

[0070] Use 125μm thick high temperature resistant PET as the substrate, as shown in the figure Figure 1 As shown, a layer of the heat-curable conductive adhesive of the embodiment or the comparative example is coated on the surface of the flexible PET substrate with a doctor blade. The slurry PET film is then heated at 200° C. for 10 minutes in a hot air blast drying oven to cure the conductive adhesive. The obtained embodiment and comparative sample are folded in the middle of the PET film, and the toughness of the sample is evaluated according to the maximum bendable angle.

[0071] [Determination of conductivity of conductive adhesive]

[0072] Use the heat-curing conductive adhesive of the embodiment or the comparative example, apply it on Figure 2The surface of the glass substrate shown in the figure has a laser grooved circuit on the glass substrate, so the conductive glue will be tightly filled in the groove after scraping. As long as a TCO blue film is placed under the glass substrate, the conductive glue will form a good contact with the TCO surface. This method is different from the traditional screen printing method for preparing wiring circuits. The latter has a large difference in the line type of the electrode circuit left by printing due to the different rheological properties of the slurry. The measured line resistance and contact resistance cannot be accurately determined. The laser grooved glass substrate involved in the present invention has a fixed groove pattern, and the conductive glue automatically fills the groove through the groove area during the scraping process. Then it is cured at a temperature of 200°C for 10 minutes to obtain an electrode circuit 20 for contact resistance measurement and an electrode circuit 30 for testing line resistance, and the results are accurate. The line resistance of the embodiment and the comparative example is measured using a multimeter, and the contact resistance is measured using a four-probe TLM method.

[0073] The material information of each type of powder involved in the present invention is as follows:

[0074]

[0075] The structural information of different phenolic hydroxyl compounds (component (F)) involved in the present invention is as follows:

[0076]

[0077]

[0078]

[0079] Example 1-15 Preparation method of low contact resistance conductive adhesive

[0080] According to the components and their proportions shown in Table 1, the epoxy resin (B), the solvent (D), the curing agent (C), the rheological additive (E), and the phenolic hydroxyl compound (F) are first fully dispersed under stirring with a mechanical stirrer to obtain an organic vehicle; then an appropriate amount of the organic vehicle is weighed and blended with the conductive powder (A), and after stirring, the mixture is fully ground with a three-roll grinder to obtain a thermosetting conductive adhesive.

[0081] Wherein, the curing agent (C) is: 1,3-di-tert-butylimidazolium tetrafluoroborate.

[0082] The solvent (D) is a mixed solvent of diethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, dimethyl malonate, alcohol ester dodecahydrate, ethylene glycol butyl ether, and triethylene glycol methyl ether, and the volume ratio is fixed at 4:1:1:0.5:2:1.5.

[0083] The rheological additives (E) are all: BYK111, TEGO410, RM2020, a fixed mixture in a weight ratio of 1:2:2.

[0084] The other components are shown in Table 1.

[0085] Table 1

[0086]

[0087]

[0088] Comparative Example 1

[0089] The solvent, rheological additive and curing agent are the same as those in Example 3, and the others are as shown in Table 2.

[0090] Table 2

[0091]

[0092] Comparative Example 2

[0093] The solvent and rheological additive were the same as those in Example 3, and the curing agent was replaced by isopropyl imidazole tetrafluoroborate; the others were as shown in Table 3.

[0094] Table 3

[0095]

[0096] Performance Test:

[0097] A portion of the conductive adhesive prepared above was scraped on a laser grooved glass substrate, and the rest was stored at room temperature for 10 days before testing the corresponding electrical properties and viscosity changes. After the conductive adhesive was scraped and cured, the conductivity was tested and then placed in a double 85°C weathering test chamber to test the moisture and heat resistance. The specific results are shown in Table 4.

[0098] Table 4

[0099]

[0100]

[0101] Herein, "10-day viscosity change%" refers to the percentage of the ratio of the difference between the viscosity of the conductive adhesive after 10 days and the initial viscosity to the initial viscosity.

[0102] The process of measuring the moisture and heat resistance is as follows: the conductive adhesive is transferred to the TCO blue film through the laser grooved glass substrate, and the initial line resistance R of the conductive adhesive is tested. 1 And contact resistance Rc 1 Then, the TCO blue film with the electrode circuit printed with conductive glue was placed in a constant temperature and humidity chamber at 85℃ and 85% humidity. After 10 days, the line resistance R 2 And contact resistance Rc 2 , when the line resistance (R 2 -R1 ) / R 1 >5% is considered unqualified; 5% to 2% is considered fair; and less than 2% is considered excellent. 2 -Rc 1 ) / Rc 1 >5% is considered unqualified; 5% to 2% is considered fair; and below 2% is considered excellent.

[0103] In view of the comparative examples and the embodiments, adding a specific suitable curing agent has an obvious moisture and heat resistance effect and can solve the moisture and heat resistance problem; and adding a phenolic hydroxyl compound can reduce the contact resistance.

[0104] According to the above invention, metal powder with low silver content can be appropriately selected to be used in combination with the conductive adhesive composition of the present invention for metallization of heterojunction solar cells, thereby achieving the purpose of cost reduction.

[0105] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A heat-curing conductive adhesive, characterized in that: By adding a phenolic hydroxyl compound as a component for reducing contact resistance, the composition is as follows: (A) conductive powder, (B) epoxy resin, (C) curing agent, (D) solvent, (E) rheological additive, and (F) phenolic hydroxyl compound; The (A) conductive powder is a mixture of pure silver ③ and pure silver ① in a mass ratio of 56:37, pure silver ①, pure silver ②, or pure silver ③, and the (B) epoxy resin is an alicyclic epoxy resin; Alternatively, the (A) conductive powder is silver-coated copper ③, silver-coated copper ④, or a mixture of pure silver ② / silver-coated copper ④ in a mass ratio of 56:37, and the (B) epoxy resin is a combination of alicyclic epoxy resin and bisphenol A epoxy resin, and the mass ratio of alicyclic epoxy resin to bisphenol A epoxy resin is 2.5:1; The material information of each powder type is as follows: The (C) curing agent is 1,3-di-tert-butyl imidazole tetrafluoroborate, and its structure is shown in formula (1): The structure of the (F) phenolic hydroxy compound is shown in formula (2): Wherein, R is a C1-C5 alkyl group substituted with a hydroxyl group, or a C1-C5 alkyl group substituted with a C2-C6 ester group, and the Arabic numerals in the formula (2) are the positions of the hydroxyl groups, wherein the number of hydroxyl groups is 2; According to the weight ratio, (A) conductive powder 90-95 parts, (B) epoxy resin 1-5 parts, (C) curing agent 0.1-0.5 parts, (D) solvent 1-5 parts, (E) rheological additive 0.1-1 parts, (F) phenolic hydroxyl compound 0.1-0.5 parts.

2. The heat-curing conductive adhesive according to claim 1, characterized in that: (D) The solvent is a mixed solvent of diethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, dimethyl malonate, alcohol ester dodecahydrate, ethylene glycol butyl ether, and triethylene glycol methyl ether, with a volume ratio of 4:1:1:0.5:2:1.5; (E) The rheological additive is a combination of any one or more of a thixotropic agent, a leveling agent, a dispersant, and a lubricant.

3. A method for preparing the heat-curing conductive adhesive according to any one of claims 1 to 2, characterized in that: include: First, (B) epoxy resin, (D) solvent, (C) curing agent, (E) rheological additive, and (F) phenolic hydroxyl compound are fully dispersed under stirring of a mechanical stirrer to obtain an organic carrier; then (A) conductive powder is added and blended, and after stirring, it is fully ground with a three-roll grinder to obtain a thermosetting conductive adhesive.

4. A method for reducing the contact resistance of a thermally cured conductive adhesive, characterized in that: Adding phenolic hydroxyl compounds as modifiers reduces contact resistance; The method comprises the following steps: according to the components in claim 1, (B) epoxy resin, (D) solvent, (C) curing agent, (E) rheological additive and (F) phenolic hydroxy compound are fully dispersed under stirring of a mechanical stirrer to obtain an organic carrier; then (A) conductive powder is added and blended, and after stirring, the mixture is fully ground with a three-roll grinder.

5. An electrode, characterized in that: Contains the heat-curing conductive adhesive according to any one of claims 1 to 2.

6. Use of the thermosetting conductive adhesive according to any one of claims 1 to 2 or the electrode according to claim 5 in the field of solar cells.

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