High-adhesion and high-reliability acrylic conductive pressure-sensitive adhesive and preparation method thereof

Abstract

This invention discloses a high-adhesion, high-reliability acrylic voltage-sensitive adhesive and its preparation method. The adhesive comprises an acrylic copolymer resin, surface-modified conductive powder, surface-modified conductive reinforcing fibers, a tackifying resin, a crosslinking agent, and a coupling agent. By introducing characteristic monomers containing phosphate ester groups, the chemical affinity of the adhesive to the metal substrate is enhanced. Simultaneously, a three-dimensional conductive network is constructed using silver-coated copper powder and carbon nanotubes / graphene, and surface grafting modification enables covalent bonds between the filler and the matrix. This solves the problems of filler sedimentation and the difficulty in simultaneously achieving conductivity and adhesion in traditional voltage-sensitive adhesives. The voltage-sensitive adhesive prepared by this invention exhibits excellent adhesive strength, conductive stability, and long-term reliability, making it suitable for electronic packaging and electromagnetic shielding applications.

Description

Technical Field

[0001] This invention belongs to the field of adhesive technology, specifically relating to a high-adhesion, high-reliability acrylic conductive voltage-sensitive adhesive and its preparation method. Background Technology

[0002] Traditional voltage-sensitive adhesives typically incorporate large amounts of metal powder (such as silver or nickel) or graphite into an acrylic matrix through physical mixing. This method has the following drawbacks:

[0003] Settling issue: The conductive filler has a high density and is prone to settling during storage and coating, resulting in uneven conductivity.

[0004] Performance contradiction: In order to achieve high conductivity, the filler ratio must be increased significantly, which will seriously damage the cohesive force of the colloid, resulting in a decrease in peel strength and even powdering.

[0005] Weak interfacial bonding: Traditional adhesives mainly rely on physical adsorption, which results in insufficient chemical affinity for metal substrates and poor long-term reliability. Summary of the Invention

[0006] The purpose of this invention is to provide an acrylic voltage-sensitive adhesive with high adhesion and high reliability, and a method for preparing the same, in order to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a high-adhesion, high-reliability acrylic voltage-sensitive adhesive and its preparation method, comprising the following raw materials in parts by weight:

[0008] Acrylic copolymer resin: 100 parts;

[0009] Surface-modified conductive powder: 30–80 parts;

[0010] Surface-modified conductive reinforcing fibers: 0.5–5 parts (selected from carbon nanotubes or graphene);

[0011] Tackifying resin: 10–30 parts;

[0012] Crosslinking agent: 0.5–3 parts;

[0013] Coupling agent: 1–5 parts.

[0014] Preferably, the monomer composition of the acrylic copolymer resin includes:

[0015] Soft monomers: butyl acrylate (BA) or isooctyl acrylate (EHA).

[0016] Functional monomers: monomers containing carboxyl or hydroxyl groups (such as AA acrylate or HEMA hydroxyethyl methacrylate).

[0017] Characteristic monomers: acrylic monomers containing phosphate ester groups, accounting for 2%–8% of the total weight of monomers.

[0018] Preferably, the surface-modified conductive powder is silver-coated copper powder; the surface-modified conductive reinforcing fiber is multi-walled carbon nanotube or graphene; the two are combined to form a three-dimensional conductive network.

[0019] Preferably, both the surface-modified conductive powder and the surface-modified conductive reinforcing fiber are treated with a silane coupling agent (such as KH-570) to graft unsaturated double bonds onto their surfaces, enabling them to participate in the curing reaction of the acrylic matrix to form covalent bonds.

[0020] A method for preparing a high-adhesion, high-reliability acrylic voltage-sensitive adhesive includes the following steps:

[0021] S1. Prepolymer Synthesis: Soft monomers, functional monomers, and characteristic monomers are dissolved in ethyl acetate, and initiator BPO is added. The mixture is refluxed at 80°C for 6–8 hours to obtain an acrylic resin with a molecular weight of 600,000–800,000.

[0022] S2. Conductive powder pretreatment: Immerse the conductive powder in a 1% silane coupling agent ethanol solution, sonicate for 30 minutes, filter and dry.

[0023] S3, Adhesive Formulation: The resin obtained in S1 is mixed with the conductive powder, conductive reinforcing fiber, and crosslinking agent treated in S2, and dispersed at high speed;

[0024] S4. Filtration and Coating: After filtration, the material is coated onto the release layer and cured to obtain the finished product.

[0025] The technical effects and advantages of this invention are as follows:

[0026] 1. This invention significantly improves adhesive strength through molecular structure design; by introducing 2%–8% acrylate phosphate monomer into the acrylic resin backbone, the strong chemical bonding force between the phosphate groups and the metal substrate is utilized, solving the problem of poor adhesion of traditional conductive voltage-sensitive adhesives to metals and achieving high peel strength.

[0027] 2. This invention solves the problems of sedimentation and powder shedding through filler surface modification technology; it uses a silane coupling agent to perform in-situ surface grafting of silver-coated copper and carbon nanotubes, giving the conductive filler surface unsaturated double bonds that participate in the matrix curing reaction. This "chemical bonding" method firmly locks the conductive particles in the adhesive network, eliminating sedimentation and stratification during storage and powder shedding during application. Ω

[0028] 3. This invention achieves a balance between low cost and high performance through a composite technology. By combining silver-coated copper with carbon nanotubes / graphene, a highly efficient three-dimensional conductive pathway is constructed, ensuring a volume resistivity of 10⁻⁶. -3 ~10 -4 While achieving Ω.cm level, it also reduces the amount of expensive silver powder used, resulting in significant economic benefits. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the present invention.

[0030] In the diagram, 1-reworkable flame-retardant thermally conductive adhesive layer, 2-release layer. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1: Preparation of Basic Formula

[0033] 1. Raw material preparation:

[0034] Soft monomers: 70 parts by weight of isooctyl acrylate (EHA) and 20 parts by weight of butyl acrylate (BA).

[0035] Functional monomers: 5 parts by weight of acrylic acid (AA) and 5 parts by weight of phosphate acrylate monomer (5%).

[0036] Solvent and initiator: Ethyl acetate (appropriate amount), initiator BPO (benzoyl peroxide) 1 part by weight.

[0037] Filler: 50 parts by weight of silver-coated copper powder and 2 parts by weight of multi-walled carbon nanotubes.

[0038] Additives: 20 parts by weight of tackifying resin, 2 parts by weight of isocyanate crosslinking agent, and an appropriate amount of silane coupling agent KH-570.

[0039] 2. Preparation steps:

[0040] S1. Synthesis of acrylic resin: In a four-necked flask equipped with a stirrer and a condenser, EHA, BA, AA, phosphate acrylate monomers, and ethyl acetate solvent were added. Nitrogen gas was introduced for protection, and the temperature was raised to 80°C. A mixture containing dissolved BPO was added dropwise, and the reaction was refluxed for 6 hours. Subsequently, an initiator was added, and the reaction was continued at this temperature for another 2 hours to obtain an acrylic copolymer resin solution with a molecular weight of approximately 650,000.

[0041] S2. Surface modification of filler: Silver-coated copper powder and multi-walled carbon nanotubes are mixed, immersed in 1% KH-570 ethanol solution, ultrasonically treated for 30 minutes, and then dried in an oven at 80℃ to obtain a modified conductive filler with double bonds grafted on the surface.

[0042] The surface grafting modification process involves the following steps: First, the silane coupling agent KH-570 (γ-methacryloyloxypropyltrimethoxysilane) is pre-hydrolyzed in an aqueous ethanol solution. During hydrolysis, the methoxy group (-OCH3) at the end of KH-570 is converted into highly active silanol groups (-Si-OH). Subsequently, silver-coated copper powder and multi-walled carbon nanotubes are added. Under ultrasonic conditions, these silanol groups undergo a dehydration condensation reaction with the hydroxyl groups (-OH) on the surface of the conductive filler to form stable Si-O-metal / carbon covalent bonds.

[0043] Mechanism of action (explanation of chemical bonding):

[0044] 1. Inorganic end bonding: One end of the silane coupling agent is firmly anchored to the surface of the conductive filler, forming a monomolecular modified layer.

[0045] 2. Organic end crosslinking: KH-57O contains active unsaturated double bonds (C=C) at the other end. In the subsequent formulation and curing process (steps S3 and S4), these double bonds will participate in the free radical polymerization or crosslinking reaction of acrylic resin.

[0046] 3. Structural Significance: This design transforms the conductive filler from a mere physical impurity "floating" in the adhesive matrix into a chemically bonded network within the acrylic molecule. This effectively prevents the conductive powder from settling due to gravity during storage and enhances the cohesive strength within the colloid, avoiding filler detachment (powder shedding) caused by stress during use. Consequently, it significantly improves the product's conductive stability and mechanical reliability.

[0047] S3. Mixing and Curing: Mix the resin solution obtained in S1 with the modified filler, tackifying resin, and crosslinking agent from S2. Disperse at high speed (800-1000 rpm) for 30 minutes to ensure uniform dispersion of the filler. Then filter to remove impurities.

[0048] S4. Coating: Apply the above adhesive solution evenly onto the release paper (PET release film) and place it in an oven. Pre-bake at 100℃ for 5 minutes, and then cure at 120℃ for 10 minutes to obtain a pressure-sensitive adhesive product with a thickness of approximately 50μm.

[0049] Example 2: Adjusting the content of functional monomers

[0050] This embodiment is basically the same as Example 1, except for the content of acrylate phosphate monomer.

[0051] Adjusted parameters: The proportion of acrylate phosphate monomer is adjusted to 2%.

[0052] Results: The prepared adhesive still has good conductivity and improved initial adhesion to metal substrates, making it suitable for applications with high requirements for aging resistance.

[0053] Example 3: Adjusting the filler compound ratio

[0054] This embodiment is basically the same as Embodiment 1, except for the selection of packing material.

[0055] Adjust parameters: Replace "multi-walled carbon nanotubes" with an equal amount of "graphene", increase silver-coated copper powder to 60 parts by weight, and reduce graphene to 1 part by weight.

[0056] Effect: By utilizing the two-dimensional sheet structure of graphene, the volume resistivity of the colloid is further reduced, making it more suitable for high-frequency electromagnetic shielding.

[0057] Comparative Example 1: Preparation of Basic Formulation

[0058] 1. Raw material preparation:

[0059] Soft monomers: 70 parts by weight of isooctyl acrylate (EHA) and 20 parts by weight of butyl acrylate (BA).

[0060] Functional monomer: Acrylic acid (AA) 10 parts by weight.

[0061] Solvent and initiator: Ethyl acetate (appropriate amount), initiator BPO (benzoyl peroxide) 1 part by weight.

[0062] Filler: 50 parts by weight of nickel powder.

[0063] Additives: 20 parts by weight of tackifying resin, 2 parts by weight of isocyanate crosslinking agent.

[0064] 2. Preparation steps:

[0065] S1. Synthesis of acrylic resin: In a four-necked flask equipped with a stirrer and a condenser, EHA, BA, AA, and ethyl acetate solvents were added. Nitrogen gas was introduced for protection, and the temperature was raised to 80°C. A mixture containing dissolved BPO was added dropwise, and the reaction was refluxed for 6 hours. Subsequently, an initiator was added, and the reaction was continued at this temperature for another 2 hours to obtain an acrylic copolymer resin solution with a molecular weight of approximately 650,000.

[0066] S2. Pre-dispersion of filler: Soak nickel powder in an appropriate amount of ethyl acetate solution and sonicate for 30 minutes to reduce powder agglomeration.

[0067] S3. Mixing and Curing: Mix the resin solution obtained in S1 with the modified filler, tackifying resin, and crosslinking agent from S2. Disperse at high speed (800-1000 rpm) for 30 minutes to ensure uniform dispersion of the filler. Then filter to remove impurities.

[0068] S4. Coating: Apply the above adhesive solution evenly onto the release paper (PET release film) and place it in an oven. Pre-bake at 100℃ for 5 minutes, and then cure at 120℃ for 10 minutes to obtain a pressure-sensitive adhesive product with a thickness of approximately 50μm.

[0069] Experimental data and effect verification

[0070]

[0071] The applicant further declares that while the above embodiments illustrate the implementation method and apparatus structure of the present invention, the present invention is not limited to the above-described embodiments, meaning that the present invention must rely on the above methods and structures to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the selected implementation methods, additions to steps, and selections of specific methods all fall within the protection and disclosure scope of the present invention.

[0072] This invention is not limited to the above-described embodiments. All methods that employ similar structures and approaches to achieve the objectives of this invention are within the scope of protection of this invention.

Claims

1. A high-adhesion, high-reliability acrylic voltage-sensitive adhesive and its preparation method, characterized in that, Including the following parts by weight of raw materials: Acrylic copolymer resin: 100 parts; Surface-modified conductive powder: 30–80 parts; Surface-modified conductive reinforcing fiber: 0.5–5 parts; Tackifying resin: 10–30 parts; Crosslinking agent: 0.5–3 parts; Coupling agent: 1–5 parts.

2. The acrylic conductive voltage-sensitive adhesive according to claim 1, characterized in that, The monomer composition of the acrylic copolymer resin includes: Soft monomers: butyl acrylate (BA) or isooctyl acrylate (EHA). Functional monomers: monomers containing carboxyl or hydroxyl groups; Characteristic monomers: acrylic monomers containing phosphate ester groups, accounting for 2%–8% of the total weight of monomers.

3. The acrylic conductive voltage-sensitive adhesive according to claim 1, characterized in that, The surface-modified conductive powder is silver-coated copper powder; the surface-modified conductive reinforcing fiber is multi-walled carbon nanotube or graphene; the two are combined to form a three-dimensional conductive network.

4. The acrylic conductive voltage-sensitive adhesive according to claim 1, characterized in that, Both the surface-modified conductive powder and the surface-modified conductive reinforcing fiber are treated with silane coupling agent to graft unsaturated double bonds onto their surfaces, enabling them to participate in the curing reaction of the acrylic matrix to form covalent bonds.

5. A method for preparing a high-adhesion, high-reliability acrylic voltage-sensitive adhesive as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Prepolymer Synthesis: Soft monomers, functional monomers, and characteristic monomers are dissolved in ethyl acetate, and initiator BPO is added. The mixture is refluxed at 80°C for 6–8 hours to obtain an acrylic resin with a molecular weight of 600,000–800,000. S2. Conductive powder pretreatment: Immerse the conductive powder in a 1% silane coupling agent ethanol solution, sonicate for 30 minutes, filter and dry. S3, Adhesive Formulation: The resin obtained in S1 is mixed with the conductive powder, conductive reinforcing fiber, and crosslinking agent treated in S2, and dispersed at high speed; S4. Filtration and Coating: After filtration, the material is coated onto the release layer and cured to obtain the finished product.

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