Conductive adhesive and application thereof

Abstract

The invention relates to the technical field of conductive adhesive films, and particularly discloses a conductive adhesive and application thereof. The conductive adhesive provided by the invention comprises the following raw material components in parts by mass: 100 parts of flexible resin containing carboxyl, 1-100 parts of carboxyl modified polyester containing naphthyl and 5-50 parts of epoxy resin, wherein the acid value of the flexible resin containing carboxyl is 1 to 50 mgKOH / g; the epoxy equivalent of the epoxy resin is 150 to 300 g / eq. Through reasonable design of the components and proportion, the conductive adhesive is applied to the conductive adhesive film, so that the conductivity, cohesiveness and heat resistance of the conductive adhesive film can be obviously improved, and the low-temperature storage time of the conductive adhesive film can be obviously prolonged; the conductive adhesive film provided by the invention has the advantages that the conduction resistance is less than 500m omega, the adhesive property is good, the 90-degree peel strength reaches 10N / cm or above, and the low-temperature storage time is long.

Description

A conductive adhesive and its application Technical Field

[0001] This invention relates to the field of conductive adhesive film technology, and more particularly to a conductive adhesive and its application. Background Technology

[0002] Conductive adhesive film is a type of lead-free bonding material that provides mechanical and electrical connections between components and circuit boards, and is one of the core packaging materials for wireless communication terminals. Conductive adhesive film is widely used in various electronic fields such as microelectronic packaging, multilayer printed circuit boards, and conductive line bonding, including in camera modules and LCD modules; in the electronics industry, conductive adhesive film has become an indispensable new material.

[0003] In recent years, driven primarily by the demands of 5G, the Internet of Things, artificial intelligence, and new energy, the electronics field has seen significant technological advancements in areas such as high-density circuitry and lightweight mobile devices, leading to a substantial increase in the quantity and diversity of thermoplastic circuit boards (PCBs). However, while thermoplastic PCB technology is relatively mature, market competition is intensifying. This places higher demands on the conductivity, adhesion, and storage stability of conductive adhesive films, which are difficult to achieve simultaneously using existing technologies. Currently, conductive adhesive films used in the market have a very short shelf life at room temperature and a low-temperature shelf life of no more than six months. Beyond this period, they deteriorate and fail before or during use, resulting in waste and increased costs. Therefore, providing a conductive adhesive to improve the conductivity, adhesion, and heat resistance of conductive adhesive films, and to extend their low-temperature storage time, is of great significance. Summary of the Invention

[0004] In view of this, the present invention provides a conductive adhesive and its application. The conductive adhesive provided by the present invention can significantly solve the problems of poor conductivity, adhesion, and heat resistance of existing conductive films, as well as their short low-temperature storage time.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows: The present invention provides a conductive adhesive comprising the following raw material components in parts by weight: 100 parts of a carboxyl-containing flexible resin, 1-100 parts of a naphthyl-containing carboxyl-modified polyester, and 5-50 parts of an epoxy resin; wherein the acid value of the carboxyl-containing flexible resin is 1-50 mgKOH / g; and the epoxy equivalent of the epoxy resin is 150-300 g / eq.

[0006] Compared to existing technologies, the conductive adhesive provided by this invention, when a carboxyl-containing flexible resin with a specific acid value is selected, can react with a specific epoxy resin to form a dense network structure, thereby improving the conductivity and adhesion of the conductive film. The naphthyl groups in the carboxyl-modified polyester can further improve the thermal stability of the conductive film, and their carboxyl groups can also improve component compatibility, thus improving conductivity. A specific mass of flexible resin in the carboxyl-containing flexible resin can balance the rigid skeleton formed by the epoxy resin, further synergizing with the carboxyl-modified polyester to prevent thermal deformation and brittleness of the conductive film, thereby improving its heat resistance. Under low-temperature conditions, the flexible segments in the carboxyl-containing flexible resin can inhibit molecular chain crystallization at low temperatures, and the naphthyl groups in the carboxyl-modified polyester can reduce the degree of freedom of molecular chain movement. Their carboxyl groups can also delay crosslinking time by forming van der Waals forces or hydrogen bonds with the epoxy groups of the epoxy resin, preventing excessively rapid crosslinking and thus improving low-temperature storage time. Furthermore, the specific epoxy resin has moderate reactivity, avoiding the problem of decreased conductive film performance under low-temperature conditions.

[0007] Preferably, the conductive adhesive further comprises the following raw material components in parts by weight: 100-350 parts of conductive particles, 0.01-4 parts of non-microencapsulated curing agent, 0.5-15 parts of microencapsulated curing agent, and 0.01-10 parts of additives.

[0008] This invention further defines a conductive adhesive in which the conductivity, adhesion, and heat resistance of the conductive film can be significantly improved and the low-temperature storage time can be increased by determining the amount of each component.

[0009] Preferably, the conductive adhesive comprises the following raw material components in parts by weight: 100 parts of carboxyl-containing flexible resin, 10-90 parts of naphthyl-containing carboxyl-modified polyester, 5-40 parts of epoxy resin, 110-250 parts of conductive particles, 0.01-4 parts of non-microencapsulated curing agent, 0.5-12 parts of microencapsulated curing agent, and 0.01-10 parts of additives.

[0010] More preferably, the conductive adhesive comprises the following raw material components in parts by weight: 100 parts of carboxyl-containing flexible resin, 10-90 parts of naphthyl-containing carboxyl-modified polyester, 8-30 parts of epoxy resin, 120-200 parts of conductive particles, 0.05-3 parts of non-microencapsulated curing agent, 0.5-10 parts of microencapsulated curing agent, and 0.01-10 parts of additives.

[0011] Preferably, the acid value of the carboxyl-containing flexible resin is 5~30 mgKOH / g.

[0012] When the acid value of the carboxyl-containing flexible resin is <1mgKOH / g, it is not easy to react with epoxy resin, which affects the heat resistance of the conductive film. When the acid value of the carboxyl-containing flexible resin is >50mgKOH / g, it becomes too hard after curing, or the carboxyl-containing flexible resin cannot react with epoxy resin, which affects the adhesion and durability of the conductive film.

[0013] Preferably, the carboxyl-containing flexible resin includes at least one of carboxyl-containing polyester, carboxyl-containing polyamide, carboxyl-containing polyurethane, or carboxyl-containing nitrile rubber.

[0014] For example, the carboxyl-containing polyamide is selected from TAPE-826-4S of T&K TOKA Co., Ltd.; the carboxyl-containing polyurethane is selected from VYLON UR3500 of Toyobo Co., Ltd. of Japan; and the carboxyl-containing nitrile rubber is selected from NBR1072CGX of Zeon Co., Ltd. of Japan.

[0015] Preferably, the carboxyl-containing flexible resin is a carboxyl-containing polyester.

[0016] More preferably, the number-average molecular weight of the carboxyl-containing polyester is 5000~50000, and the glass transition temperature is -20~100℃.

[0017] Through research, the inventors discovered that when the number average molecular weight is <5000, the film-forming properties are poor; when the number average molecular weight is >50000, the resin has poor flowability during processing, both of which affect the performance of conductive adhesives. When the glass transition temperature of carboxyl-containing polyester is <-20℃, there may be a large amount of adhesive overflow. If the glass transition temperature of carboxyl-containing polyester is >100℃, the flowability during processing is poor, which can easily lead to poor conductivity of the film at the point of contact.

[0018] More preferably, the carboxyl-containing polyester is selected from VYLON ST5810 of Toyobo Co., Ltd. of Japan.

[0019] Preferably, the carboxyl-modified polyester containing naphthyl groups comprises the following preparation steps: S1, mixing non-naphthalenedicarboxylic acid, non-naphthalenediol, naphthalene-containing monomer and a first catalyst uniformly, and reacting at 180~260℃ and -0.02~-0.1MPa to obtain a hydroxyl prepolymer; S2, mixing the hydroxyl prepolymer, solvent, chain extender and second catalyst, and then reacting at 70~80℃ to obtain the carboxyl-modified polyester containing naphthyl groups.

[0020] The method for preparing carboxyl-modified polyesters containing naphthyl groups provided by this invention has mild and controllable reaction conditions, no complicated post-processing steps, and is suitable for mass production.

[0021] Preferably, in S1, the naphthalene-containing monomer includes at least one of 2,7-dihydroxynaphthalene, 2,6-naphthalenedicarboxylic acid, or dimethyl 2,6-naphthalenedicarboxylic acid.

[0022] Preferably, in S1, the reaction time is 8-10 hours.

[0023] Preferably, in S1, the non-naphthalene glycol includes at least one of dimer linoleyl alcohol, hexanediol, 1,4-butanediol, ethylene glycol, neopentyl glycol, or 2,2′-oxodiethanol.

[0024] Preferably, in S1, the non-naphthalenedicarboxylic acid includes at least one of terephthalic acid, adipic acid, dimer linoleic acid, sebacic acid, or dodecanoic acid.

[0025] Preferably, in S1, the first catalyst includes at least one of tetrabutyl titanate or dibutyltin oxide.

[0026] Preferably, in S1, the molar ratio of the non-naphthalenedic acid, the non-naphthalenediol, the naphthalene-containing monomer, and the first catalyst is 100:(90~110):(0.1~10):(0.05~0.5).

[0027] Preferably, in S2, the chain extender includes at least one of aromatic tetrahydroxy dianhydride, aliphatic tetrahydroxy dianhydride, or alicyclic tetrahydroxy dianhydride.

[0028] More preferably, in S2, the chain extender includes at least one of pyromellitic anhydride, methyltetrahydrophthalic anhydride, or cyclopentadienoic dianhydride.

[0029] Preferably, in S2, the solvent includes at least one of toluene or butanone.

[0030] More preferably, in S2, the solvent comprises toluene and butanone in a mass ratio of 1:(0.2~1.2).

[0031] Preferably, in S2, the second catalyst comprises at least one tertiary amine or a tertiary amine derivative.

[0032] More preferably, in S2, the second catalyst includes at least one of triethylamine, dimethylcyclohexylamine, or bis(dimethylaminoethyl) ether.

[0033] Preferably, in S2, the reaction time is 20-36 hours.

[0034] Preferably, in S2, the mass ratio of the hydroxyl prepolymer, solvent, second catalyst and chain extender is 100:(80~120):(0.01~0.1):(1~5).

[0035] Preferably, the epoxy equivalent of the epoxy resin is 150~250 g / eq.

[0036] Preferably, the epoxy resin includes at least one of bisphenol epoxy resin, phenolic epoxy resin, or alicyclic epoxy resin.

[0037] More preferably, the epoxy resin is a phenolic epoxy resin.

[0038] More preferably, the phenolic epoxy resin is SQCN700-1 from Shandong Shengquan New Material Co., Ltd.

[0039] Preferably, the median particle size of the conductive particles is 1~50μm.

[0040] The inventors discovered through research that when the median particle size of conductive particles is <1μm, the conductive particles are not easy to connect, which easily leads to poor conductivity; if the median particle size of conductive particles is >50μm, the conductive particles are not easy to move, resulting in poor conductivity.

[0041] More preferably, the median particle size of the conductive particles is 3~30μm.

[0042] More preferably, the conductive particles include at least one of silver powder, copper powder, nickel powder, silver-coated copper powder, or silver-coated nickel powder.

[0043] For example, the conductive particles may be spherical, dendritic, fibrous, or chain-like; preferably dendritic.

[0044] Preferably, the non-microencapsulated curing agent includes at least one of thiol compounds, aromatic amines, fatty amines, imidazoles, imidazole adducts, or polyamides.

[0045] More preferably, the thiol compound includes at least one of 2,2-bis(mercaptomethyl)-1,3-propanediol or 3-mercapto-2,2-bis(mercaptomethyl)-1-propanol.

[0046] More preferably, the aromatic amine includes at least one of 4,4-diaminodiphenyl sulfone or m-phenylenediamine.

[0047] More preferably, the fatty amine includes at least one of ethylenediamine, hexamethylenediamine, or isophoronediamine.

[0048] More preferably, the imidazole includes at least one of 2-methylimidazolium, undecylimidazolium, heptadecanylimidazolium, 2-ethyl-4-methylimidazolium, or diphenylimidazolium.

[0049] More preferably, the imidazole adduct is prepared by reacting 2-methylimidazolium with bisphenol A type epoxy resin.

[0050] For example, the reaction of the imidazole adduct includes the following steps: heating 2-methylimidazolium and bisphenol A type epoxy resin to 60°C and reacting for 4-6 hours, then heating to 80°C and reacting for 2-4 hours, and cooling to room temperature for later use.

[0051] For example, the mass ratio of 2-methylimidazole to bisphenol A type epoxy resin is 0.5:100.

[0052] It should be further noted that the bisphenol A type epoxy resin is bisphenol A type epoxy resin E-51.

[0053] More preferably, the polyamide comprises Huntsman Aradur 115.

[0054] Preferably, the D50 particle size of the microcapsule curing agent is 0.3~14μm.

[0055] If the particle size D50 of the microcapsule curing agent is less than 0.3 μm, the capsules are not easy to break, and insufficient curing is likely to occur; if the particle size D50 of the microcapsule curing agent is greater than 14 μm, the microcapsules break unevenly, which in turn leads to uneven curing and affects the performance of the conductive adhesive; more preferably, the D50 particle size of the microcapsule curing agent is 1~10 μm.

[0056] Preferably, the core material of the microcapsule curing agent includes at least one of imidazole or imidazole adducts.

[0057] More preferably, the microcapsule curing agent is selected from Asahi Kasei Corporation's HX-3742 or Asahi Kasei Corporation's HX-3941HP.

[0058] Preferably, the mass ratio of the non-microencapsulated curing agent to the microencapsulated curing agent is (1:300) to (400:100).

[0059] The inventors discovered through research that if the ratio is too high or too low, it will affect the function of the conductive adhesive film, thereby reducing its adhesion and low-temperature storage time.

[0060] More preferably, the mass ratio of the non-microencapsulated curing agent to the microencapsulated curing agent is (1:150) to (100:100).

[0061] Preferably, (mass of non-microencapsulated curing agent + mass of microencapsulated curing agent) / mass of epoxy resin = 1%~40%.

[0062] It should be further noted that the terms "non-microencapsulated curing agent," "microencapsulated curing agent," and "epoxy resin" all refer to the quantity added.

[0063] If the amount of non-microcapsule curing agent + microcapsule curing agent / epoxy resin is too small, glue overflow is likely to occur; if the amount of non-microcapsule curing agent + microcapsule curing agent / epoxy resin is too large, it will reduce the conductivity of the conductive film and its low-temperature storage time.

[0064] It should be further noted that the additives include at least one of flame retardants, defoamers, antioxidants, silane coupling agents, or rheology modifiers.

[0065] The specific components of each additive are not listed here; selection can be made using conventional techniques mastered by those skilled in the art.

[0066] The method for preparing the conductive adhesive includes the following steps: S1, adding the carboxyl-containing flexible resin, the naphthyl-containing carboxyl-modified polyester and the epoxy resin to a solvent, and then adding conductive particles, a non-microencapsulated curing agent, a microencapsulated curing agent and additives to obtain the conductive adhesive.

[0067] This invention provides the application of the above-mentioned conductive adhesive in conductive films.

[0068] The conductive adhesive provided by this invention, through the rational design of its composition and ratio, when applied to conductive adhesive films, can significantly improve the conductivity, adhesion, heat resistance, and low-temperature storage time of the conductive adhesive films. The conductive adhesive films provided by this invention have a conductivity of less than 500mΩ, good adhesion performance, a 90° peel strength of over 10N / cm, and a long low-temperature storage time. Attached Figure Description

[0069] Figure 1 is a schematic diagram of the conductive adhesive film provided in the effect example; Figure 2 is a schematic diagram of the cross-sectional stack of the conductive adhesive film provided in the effect example after processing and application; 1 is the conductive adhesive layer, 2 is the release layer, 3 is the polyester film, 4 is the SUS304 steel strip, 5 is the grounding hole, and 6 is the flexible circuit board. Detailed Implementation

[0070] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0071] In this invention, the carboxyl-containing flexible resin is VYLON ST5810 from Toyobo Co., Ltd., Japan; the epoxy resin is SQCN700-1 from Shandong Shengquan New Material Co., Ltd.; the conductive particles are silver-coated copper powder with a median particle size of 6 μm, purchased from Guangzhou Yinfeng Metal Technology Co., Ltd.; the non-microencapsulated curing agent is 2-methylimidazole; the microencapsulated curing agent is HX-3742 from Asahi Kasei Corporation; the additive is Shin-Etsu KBM-403, purchased from Shin-Etsu Chemical Co., Ltd.; and the naphthalene-containing epoxy resin is HP-4700 from DIC Corporation.

[0072] Unless otherwise specified, the raw materials and reagents used in this invention are all conventional commercially available products; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0073] Example 1 This example provides a conductive adhesive comprising the following: 100 parts of a carboxyl-containing flexible resin, 5 parts of a naphthyl-containing carboxyl-modified polyester, 5 parts of epoxy resin, 110 parts of conductive particles, 0.02 parts of a non-microencapsulated curing agent, 1 part of a microencapsulated curing agent, and 1 part of an additive; the preparation method of the naphthyl-containing carboxyl-modified polyester includes the following steps: S1, terephthalic acid, hexanediol, 2,7-dihydroxynaphthalene, and tetrabutyl titanate are mixed uniformly in a molar ratio of 100:100:0.1:0.2 and reacted at 250°C and -0.02 MPa for 8 hours to obtain a hydroxyl prepolymer; S2, the hydroxyl prepolymer, solvent, pyromellitic anhydride, and triethylamine are mixed in a mass ratio of 100:100:0.1:1 and then reacted at 80°C for 20 hours to obtain a naphthyl-containing carboxyl-modified polyester; the solvent includes toluene and methyl ethyl ketone in a mass ratio of 1:1.

[0074] The preparation method of the above-mentioned conductive adhesive includes the following steps: S1, mixing the weighed components evenly to obtain the conductive adhesive.

[0075] Example 2 This example provides a conductive adhesive, comprising 100 parts of a carboxyl-containing flexible resin, 90 parts of a naphthyl-containing carboxyl-modified polyester, 20 parts of epoxy resin, 270 parts of conductive particles, 1 part of a non-microencapsulated curing agent, 4 parts of a microencapsulated curing agent, and 1 part of an additive; the preparation method of the naphthyl-containing carboxyl-modified polyester includes the following steps: S1, adipic acid, 1,4-butanediol, 2,6-naphthalenedicarboxylic acid, and dibutyltin oxide are mixed evenly in a molar ratio of 100:90:5:0.4 and reacted at 180°C and -0.06 MPa for 10 h to obtain a hydroxyl prepolymer; S2, the hydroxyl prepolymer, solvent, pyromellitic anhydride, and dimethylcyclohexylamine are mixed in a mass ratio of 100:80:0.05:3 and then reacted at 80°C for 30 h to obtain a naphthyl-containing carboxyl-modified polyester; the solvent includes toluene and methyl ethyl ketone in a mass ratio of 1:1.

[0076] The preparation method of the above-mentioned conductive adhesive includes the following steps: S1, mixing the weighed components evenly to obtain the conductive adhesive.

[0077] Example 3 This example provides a conductive adhesive, comprising the following: 100 parts of a carboxyl-containing flexible resin, 5 parts of a naphthyl-containing carboxyl-modified polyester, 40 parts of epoxy resin, 200 parts of conductive particles, 2.8 parts of a non-microencapsulated curing agent, 10 parts of a microencapsulated curing agent, and 1 part of an additive; the preparation method of the naphthyl-containing carboxyl-modified polyester includes the following steps: S1, based on a molar ratio of 100:110:8:0.4, dimeric linoleic acid, dimeric linoleic acid... Oleyl alcohol, dimethyl 2,6-naphthalenedicarboxylate, and dibutyltin oxide were mixed evenly and reacted at 200℃ and -0.1MPa for 10h to obtain a hydroxyl prepolymer; S2, the hydroxyl prepolymer, solvent, pyromellitic anhydride, and dimethylcyclohexylamine were mixed in a mass ratio of 100:120:0.02:5 and then reacted at 80℃ for 30h to obtain a carboxyl-modified polyester containing naphthyl groups; the solvent included toluene and methyl ethyl ketone in a mass ratio of 1:1.

[0078] The preparation method of the above-mentioned conductive adhesive includes the following steps: S1, mixing the weighed components evenly to obtain the conductive adhesive.

[0079] Example 4 This example provides a conductive adhesive comprising the following: 100 parts of a carboxyl-containing flexible resin, 90 parts of a naphthyl-containing carboxyl-modified polyester, 20 parts of epoxy resin, 270 parts of conductive particles, 1 part of a non-microencapsulated curing agent, 4 parts of a microencapsulated curing agent, and 1 part of an additive; The preparation method of the naphthyl-containing carboxyl-modified polyester includes the following steps: S1, terephthalic acid, hexanediol, 2,7-dihydroxynaphthalene, and tetrabutyl titanate are mixed uniformly in a molar ratio of 100:100:0.1:0.2 and reacted at 250°C and -0.02 MPa for 8 hours to obtain a hydroxyl prepolymer; S2, the hydroxyl prepolymer, solvent, pyromellitic anhydride, and triethylamine are mixed in a mass ratio of 100:100:0.1:1 and then reacted at 80°C for 20 hours to obtain a naphthyl-containing carboxyl-modified polyester; the solvent includes toluene and methyl ethyl ketone in a mass ratio of 1:1.

[0080] The preparation method of the above-mentioned conductive adhesive includes the following steps: S1, mixing the weighed components evenly to obtain the conductive adhesive.

[0081] Comparative Example 1 differs from Example 3 in that the content of the microcapsule curing agent is increased to 15 parts; the remaining components and preparation methods are the same as in Example 3.

[0082] Comparative Example 2 differs from Example 3 in that the content of the non-microcapsule curing agent is increased to 5 parts; the remaining components and preparation methods are the same as in Example 3.

[0083] Comparative Example 3 differs from Example 1 in that it does not contain a non-microencapsulation curing agent; the remaining components and preparation methods are the same as in Example 1.

[0084] Comparative Example 4 differs from Example 3 in that: no microcapsule curing agent is added; the remaining components and preparation methods are the same as in Example 3.

[0085] Comparative Example 5 differs from Example 1 in that it does not contain carboxyl-modified polyester with naphthyl groups; the remaining components and preparation methods are the same as in Example 1.

[0086] Comparative Example 6 differs from Example 1 in that the carboxyl-modified polyester containing naphthyl groups is replaced with an equal amount of HP-4700 from DIC Corporation containing naphthalene ring epoxy resin; the remaining components and preparation methods are the same as in Example 1.

[0087] In the effect example, the conductive adhesive film provided in Examples 1-4 and Comparative Examples 1-3 was coated onto the release layer of the carrier film, dried at 40°C for 5 min, and then dried at 80°C for 3 min. The thickness of the conductive adhesive layer was 60±5 μm.

[0088] The heat resistance, adhesive overflow, adhesion, conductivity, and storage properties of the conductive adhesive film prepared above were evaluated as follows: Heat resistance: The conductive adhesive film was cut into sample strips with a width of 1 cm and a length of 10 cm. The exposed conductive adhesive side was adhered to the nickel layer of a 1.5 cm wide and 15 cm long SUS304 steel strip (commercially available SUS304 steel strip with a thickness of 0.1~0.4 mm and a nickel layer of 1~3 μm thickness on the surface of the steel strip). The conductive adhesive film and the SUS304 steel strip were pressed together using a roller press at 140℃, 0.6 MPa, and 0.3 m / min. After peeling off the carrier film, a 1.5 cm wide strip was covered. Copper foils measuring 1 cm in diameter and 15 cm in length were hot-pressed at 180℃, 2 MPa, and 3 min, and then heated in an electric furnace at 160℃ for 60 min to obtain evaluation samples. The samples were then immersed in lead-free solder baths at 265℃ and 288℃ for 30 s, respectively. After removal, the samples were visually inspected for bubbling, and the bubbling condition was used as an indicator. Heat resistance was evaluated according to the following criteria: ○: Good (no bubbling when immersed in lead-free solder baths at 265℃ and 288℃); △: Satisfactory (no bubbling when immersed in lead-free solder baths at 265℃, bubbling when immersed in lead-free solder baths at 288℃); ×: Unsatisfactory (bubbling when immersed in lead-free solder baths at 265℃ and 288℃).

[0089] Adhesive overflow: The conductive adhesive film prepared in each embodiment and comparative example was cut into sample strips with a width of 1 cm and a length of 10 cm. The exposed conductive adhesive side was attached to the nickel layer of a SUS304 steel strip with a width of 1.5 cm and a length of 15 cm (commercially available SUS304 steel strip with a thickness of 0.1~0.4 mm and a nickel layer with a thickness of 1-3 μm on the surface of the steel strip). The conductive adhesive film and the SUS304 steel strip were rolled together using a roller press at 140°C, 0.6 MPa, and 0.3 m / min. After cutting the metal plate with conductive adhesive into 5mm*12mm dimensions using a stamping machine, the carrier film is peeled off, and the conductive adhesive side is attached to the polyimide film (manufactured by Toray DuPont). Then, they are hot-pressed at 180°C, 2MPa, and 3min, followed by heating in a 160°C electric furnace for 60min to obtain the evaluation sample. The evaluation sample is observed using a magnifying glass with a magnification of 100-500x. The amount of conductive adhesive flowing from around the SUS304 steel strip (the maximum width between the edge of the SUS304 steel strip and the edge of the conductive adhesive) is measured, and the measured value is used as an indicator. The adhesive overflow is evaluated according to the following evaluation criteria: ◎: Excellent (overflow ≤ 100μm); ○: Good (overflow ≤ 150μm); △: Satisfactory (overflow ≤ 200μm); ×: Unsatisfactory (overflow > 200μm).

[0090] Adhesion: The conductive adhesive film was cut into sample strips 1cm wide and 10cm long. The exposed conductive adhesive side was adhered to the nickel layer of a 1.5cm wide and 15cm long SUS304 steel strip (commercially available SUS304 steel strip with a thickness of 0.1~0.4mm and a nickel layer of 1~3μm thickness on the surface). The conductive adhesive film and SUS304 steel strip were pressed together using a roller press at 140℃, 0.6MPa, and 0.3m / min. After peeling off the carrier film, a copper foil 1.5cm wide and 15cm long was applied, and the mixture was then pressed at 180℃, 2MPa, and for 3min. They were hot-pressed and then heated in an electric furnace at 160℃ for 60 minutes to obtain evaluation samples. Using a tensile testing machine (Jinan Langguang Electromechanical Technology Co., Ltd., C610H), the adhesion between the conductive adhesive and SUS304 steel strip or copper foil was tested at a tensile speed of 50 mm / min and a 90° peel test. The magnitude of the adhesion force was used to evaluate the adhesion performance. The adhesion was evaluated according to the following evaluation criteria: ◎: Excellent (adhesion force ≥ 15 N / cm); ○: Good (adhesion force ≥ 12 N / cm); △: Satisfactory (adhesion force ≥ 10 N / cm); ×: Unsatisfactory (adhesion force < 10 N / cm).

[0091] Conductivity: The conductive adhesive film was cut into sample strips 1cm wide and 10cm long. The exposed conductive adhesive side was adhered to the nickel layer of a 1.5cm wide and 15cm long SUS304 steel strip (commercially available SUS304 steel strip with a thickness of 0.1~0.4mm and a nickel layer of 1~3μm on the surface). The conductive adhesive film and SUS304 steel strip were pressed together using a roller press at 140℃, 0.6MPa, and 0.3m / min. The carrier film was then peeled off and adhered to the strip. They were hot-pressed at 180℃, 2MPa, and 3min, and then heated in a 160℃ electric furnace for 60min to obtain the evaluation sample. The aforementioned thermoplastic printed circuit board was formed on both sides of a 75μm thick polyimide film. A copper foil circuit with a thickness of 32 μm was formed, and an insulating cover film with a thickness of 37.5 μm and adhesive, having circular through-holes with a diameter of 1.0 mm, was stacked on the copper foil circuit. Additionally, an insulating cover film with a thickness of 37.5 μm and adhesive, without through-holes, was stacked on another copper foil circuit, thus forming the final cross-sectional stacked structure shown in Figure 2 after the conductive adhesive film processing and application. The resistance between the SUS304 steel strip and the copper foil circuit of the evaluation sample was measured using a multimeter, and the measured values ​​were used as indicators to evaluate conductivity according to the following evaluation criteria: ◎: Excellent (resistance ≤ 20 mΩ); ○: Good (100 mΩ ≥ resistance > 20 mΩ); △: Satisfactory (500 mΩ ≥ resistance > 100 mΩ); ×: Unsatisfactory (resistance > 500 mΩ).

[0092] Low-temperature storage stability of conductive adhesive film: The conductive adhesive film was cut into wide strips with a width of 10cm and a length of 15cm. Five strips were taken from each example and comparative example and placed in an aging chamber at 10℃ and 60%RH. Samples were taken at 0d, 90d, 120d, 150d, 180d, 210d, and 240d respectively to test the heat resistance, adhesive overflow, adhesion, and conductivity according to the above method. The performance of the conductive adhesive film was evaluated according to the evaluation method. The conductive adhesive film was considered qualified only if the heat resistance, adhesive overflow, adhesion, and conductivity all met the requirements for use. The number of days that the performance was finally qualified was the test time before the number of days that failed the test. The storage stability of the conductive adhesive film was evaluated according to the following evaluation criteria.

[0093] ◎: Excellent (performance qualified for the last 180 days ≥ 180 days); ○: Good (180 days ≥ performance qualified for the last 150 days > 150 days); △: Satisfactory for use (150 days ≥ performance qualified for the last 120 days > 120 days); ×: Unsatisfactory for use (< 120 days).

[0094] The specific test results are shown in Table 1: Table 1

[0095] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A conductive adhesive, characterized in that, The raw material components include the following parts by weight: 100 parts of carboxyl-containing flexible resin, 1-100 parts of naphthyl-containing carboxyl-modified polyester, and 5-50 parts of epoxy resin; wherein the acid value of the carboxyl-containing flexible resin is 1-50 mg KOH / g; and the epoxy equivalent of the epoxy resin is 150-300 g / eq.

2. The conductive adhesive as described in claim 1, characterized in that, The conductive adhesive further includes the following raw material components in parts by weight: 100-350 parts conductive particles, 0.01-4 parts non-microencapsulated curing agent, 0.5-15 parts microencapsulated curing agent, and 0.01-10 parts additives.

3. The conductive adhesive as described in claim 2, characterized in that, The conductive adhesive comprises the following raw material components in parts by weight: 100 parts of carboxyl-containing flexible resin, 10-90 parts of naphthyl-containing carboxyl-modified polyester, 5-40 parts of epoxy resin, 110-250 parts of conductive particles, 0.01-4 parts of non-microencapsulated curing agent, 0.5-12 parts of microencapsulated curing agent, and 0.01-10 parts of additives.

4. The conductive adhesive as described in claim 3, characterized in that, The conductive adhesive comprises the following raw material components in parts by weight: 100 parts of carboxyl-containing flexible resin, 10-90 parts of naphthyl-containing carboxyl-modified polyester, 8-30 parts of epoxy resin, 120-200 parts of conductive particles, 0.05-3 parts of non-microencapsulated curing agent, 0.5-10 parts of microencapsulated curing agent, and 0.01-10 parts of additives.

5. The conductive adhesive according to any one of claims 2 to 4, characterized in that, The conductive particles include at least one of silver powder, copper powder, nickel powder, silver-coated copper powder, or silver-coated nickel powder.

6. The conductive adhesive according to any one of claims 2 to 4, characterized in that, The non-microencapsulated curing agent includes at least one of thiol compounds, aromatic amines, fatty amines, imidazoles, imidazole adducts, or polyamides.

7. The conductive adhesive as described in claim 6, characterized in that, The carboxyl-modified polyester containing naphthyl groups comprises the following preparation steps: S1, mixing non-naphthalenedicarboxylic acid, non-naphthalene glycol, naphthalene-containing monomer and a first catalyst uniformly, and reacting at 180~260℃ and -0.02~-0.1MPa to obtain a hydroxyl prepolymer; S2, mixing the hydroxyl prepolymer, solvent, chain extender and second catalyst, and then reacting at 70~80℃ to obtain the carboxyl-modified polyester containing naphthyl groups.

8. The conductive adhesive according to any one of claims 2 to 4, characterized in that, The mass ratio of the non-microencapsulated curing agent to the microencapsulated curing agent is (1:300) to (400:100).

9. The conductive adhesive according to any one of claims 2 to 4, characterized in that, (Mass of non-microencapsulated curing agent + mass of microencapsulated curing agent) / mass of epoxy resin = 1%~40%.

10. The application of the conductive adhesive according to any one of claims 1 to 9 in a conductive film.

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