Anisotropic conductive adhesive and preparation method and electronic component

Abstract

The application discloses an anisotropic conductive adhesive and a preparation method and electronic components, and relates to the technical field of packaging. The anisotropic conductive adhesive in the embodiment of the application comprises, in terms of mass fraction, 50-100 parts of epoxy resin, 0.5-30 parts of a curing agent and 10-40 parts of conductive particles with a core-shell structure, wherein the core layer of the conductive particles comprises liquid metal, and the shell layer of the conductive particles comprises a metal layer. In the application, the core-shell structure conductive particles are added to the anisotropic conductive adhesive, so that the conductive particles have good plasticity or deformability, which is beneficial to improving the reliable vertical electrical interconnection of the anisotropic conductive adhesive in the application under a low-pressure bonding scene, and is beneficial to avoiding the problem that the shell layer of the conductive particles in the conductive adhesive in the embodiment of the application is broken when the conductive adhesive is under pressure, the liquid metal in the conductive particles flows out, and the anisotropic conductive adhesive fails.

Description

Technical Field

[0001] This application relates to the field of packaging technology, and in particular to an anisotropic conductive adhesive and its preparation method, as well as electronic components. Background Technology

[0002] Anisotropic conductive paste (ACP) is a special conductive material that, after thermosetting and curing, conducts electricity along the direction of pressure while remaining insulated perpendicular to it. Furthermore, ACP demonstrates significant application potential in high-density, narrow-pitch vertical electrical interconnects due to its high efficiency and low cost. Conductive particles are uniformly dispersed within an insulating organic material. When vertical pressure is applied, some of these conductive particles are captured by the chip electrodes and substrate pads, achieving vertical conductivity and horizontal insulation. This allows for applications in ultra-narrow-pitch packaging of flexible electronic devices and liquid crystal displays, such as radio frequency identification (RFID) tag packaging.

[0003] The main components of anisotropic conductive adhesive are a polymer resin matrix and conductive particles. The polymer resin serves as the matrix, providing mechanical support after curing. The conductive particles possess excellent electrical properties, forming conductive pathways through contact between the upper and lower interfaces. Factors affecting the curing performance of anisotropic conductive adhesive include the type of curing agent, the amount of curing agent added, the curing temperature, and the curing time. By adjusting these parameters, rapid curing of the anisotropic conductive adhesive can be achieved, meeting the requirements for efficient and rapid encapsulation of RFID electronic tags.

[0004] However, the conductive particles used in traditional anisotropic conductive adhesives, such as silver (Ag), nickel (Ni), and gold (Au), often require high bonding pressure to achieve stable and reliable electrical interconnection. They are not suitable for certain scenarios such as small-sized chips and flexible substrates that require vertical electrical interconnection under low pressure.

[0005] Therefore, developing a novel anisotropic conductive adhesive to meet reliable vertical electrical interconnects in low-voltage bonding scenarios is of great significance in the electronic packaging industry. Summary of the Invention

[0006] In view of this, this application provides an anisotropic conductive adhesive and its preparation method, as well as an electronic component, aiming to improve the problem that existing anisotropic conductive adhesives do not meet the requirements for vertical electrical interconnection in low-voltage bonding scenarios.

[0007] In a first aspect, embodiments of this application provide an anisotropic conductive adhesive, comprising, by weight parts: 50 to 100 parts of epoxy resin;

[0008] Hardener 0.5 to 30 parts; and

[0009] The conductive particles with a core-shell structure consist of 10 to 40 parts, wherein the core layer of the conductive particles comprises liquid metal and the shell layer comprises a metal layer.

[0010] In some embodiments of this application, the thickness of the metal layer is 50 nm to 500 nm.

[0011] In some embodiments of this application, the thickness of the metal layer is 60 nm to 200 nm; and / or

[0012] The conductive particles have a particle size of 1 μm to 5 μm; and / or

[0013] The anisotropic conductive adhesive further includes at least one of a diluent, a thixotropic agent, and an inorganic filler; and / or

[0014] The core-shell structure contains 25 to 40 parts of conductive particles.

[0015] In some embodiments of this application, the liquid metal includes one or more of gallium, bismuth, cadmium, tin, lead, and indium; and / or

[0016] The material of the metal layer includes at least one of silver, copper, aluminum, gold, nickel, and zinc.

[0017] In some embodiments of this application, the liquid metal includes one or more of gallium, bismuth, cadmium, tin, lead, indium, bismuth-gallium alloy, gallium-indium alloy, gallium-indium-tin alloy, and indium-tin alloy; and / or

[0018] The materials of the metal layer include silver, copper, aluminum, and gold.

[0019] In some embodiments of this application, the liquid metal is a gallium-indium alloy, and the metal layer is made of silver.

[0020] In some embodiments of this application, the epoxy resin is selected from one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S type epoxy resin, linear phenolic epoxy resin, and alicyclic epoxy resin; and / or

[0021] The curing agent is one or more of dicyandiamide, aromatic diamine, imidazole, and acylhydrazine.

[0022] In some embodiments of this application, the curing agent is composed of imidazole and dicyandiamide, and the mass ratio of the imidazole to the dicyandiamide is (5-15):(5-15).

[0023] In some embodiments of this application, the reactive diluent is 1 to 50 parts by weight; and / or

[0024] The diluent includes an active diluent selected from one or more of propylene glycidyl ether, phenyl glycidyl ether, diepoxylated ethylene glycol diglycidyl ether, and resorcinol diglycidyl ether; and / or

[0025] The thixotropic agent is 0.5 to 15 parts by weight; and / or

[0026] The thixotropic agent is selected from one or more of fumed silica, precipitated silica, organobentonite, asbestos, kaolin, attapulgite, and emulsion-processed vinyl chloride compounds.

[0027] In some embodiments of this application, under a bonding pressure of 1N to 3N, the anisotropic conductive adhesive is electrically conductive in the direction of the bonding pressure and electrically insulating in the direction perpendicular to the bonding pressure.

[0028] A second aspect of this application provides a method for preparing anisotropic conductive adhesive, the method comprising the following steps:

[0029] Weigh out the core-shell structured conductive particles, epoxy resin, and curing agent according to the preset ratio;

[0030] The conductive particles of the core-shell structure, epoxy resin, and curing agent are mixed using a mixing device to obtain anisotropic conductive adhesive;

[0031] The core layer of the conductive particle comprises liquid metal, and the shell layer of the conductive particle comprises a metal layer with a thickness of 50 nm to 500 nm.

[0032] In some embodiments of this application, the step of preparing core-shell structured conductive particles includes:

[0033] A liquid metal microsphere suspension and a silver ammonia solution were obtained;

[0034] A suspension of liquid metal microspheres was added to a silver ammonia solution, and the mixture was stirred to obtain a dark brown conductive particle dispersion.

[0035] The conductive particles with a core-shell structure are obtained by filtration and drying, wherein the core layer of the conductive particles consists of liquid metal and the shell layer consists of silver.

[0036] A third aspect of this application provides an electronic component, the electronic component including a first electrical connection portion, a second electrical connection portion, and the anisotropic conductive adhesive, the anisotropic conductive adhesive being used to electrically connect the first electrical connection portion and the second electrical connection portion in the direction of bonding pressure.

[0037] Beneficial effects:

[0038] In this application, by adding core-shell structured conductive particles to the anisotropic conductive adhesive, the conductive particles are made to have better plasticity or deformability. This is beneficial to improving the reliable vertical electrical interconnection of the anisotropic conductive adhesive in low-pressure bonding scenarios, and also helps to avoid the problem that the shell of the conductive particles inside the conductive adhesive in the embodiments of this application will rupture when subjected to pressure, causing the liquid metal inside the conductive particles to flow out, thereby causing the anisotropic conductive adhesive to fail. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 Scanning electron microscope image and particle size distribution diagram of the liquid metal microsphere suspension prepared in Example 1.

[0041] Figure 2 Scanning electron microscope image and particle size distribution diagram of LM@Ag conductive microspheres prepared in Example 1.

[0042] Figure 3 Cross-sectional scanning electron microscope image and elemental distribution map of the LM@Ag conductive microspheres prepared in Example 1.

[0043] Figure 4 This is a process diagram of bonding anisotropic conductive adhesive to an RFID chip in an embodiment of the present invention.

[0044] Figure 5 This is a SEM image of the cross-section of the anisotropic conductive adhesive bonded RFID chip in Embodiment 1 of the present invention. Detailed Implementation

[0045] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Furthermore, it should be understood that the specific embodiments described herein are only for illustration and explanation of this application and are not intended to limit this application.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0047] In this application, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in its actual use or operating state, specifically the drawing directions in the accompanying drawings; while "inner" and "outer" refer to the outline of the device. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". The terms first, second, third, etc., are used merely as illustrative purposes and do not impose numerical requirements or establish a numerical order.

[0048] In this application, "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural.

[0049] In this application, "at least one" means one or more, and "more than one" means two or more. "One or more", "at least one of the following", or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0050] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0051] Anisotropic conductive paste (ACP) is a special conductive material that, after thermosetting and curing, conducts electricity along the direction of pressure while remaining insulated perpendicular to it. Furthermore, ACP demonstrates significant application potential in high-density, narrow-pitch vertical electrical interconnects due to its high efficiency and low cost. Conductive particles are uniformly dispersed within an insulating organic material. When vertical pressure is applied, some of these conductive particles are captured by the chip electrodes and substrate pads, achieving vertical conductivity and horizontal insulation. This allows for applications in ultra-narrow-pitch packaging of flexible electronic devices and liquid crystal displays, such as radio frequency identification (RFID) tag packaging.

[0052] The main components of anisotropic conductive adhesive are a polymer resin matrix and conductive particles. The polymer resin serves as the matrix, providing mechanical support after curing. The conductive particles possess excellent electrical properties, forming conductive pathways through contact between the upper and lower interfaces. Factors affecting the curing performance of anisotropic conductive adhesive include the type of curing agent, the amount of curing agent added, the curing temperature, and the curing time. By adjusting these parameters, rapid curing of the anisotropic conductive adhesive can be achieved, meeting the requirements for efficient and rapid encapsulation of RFID electronic tags.

[0053] However, the conductive particles used in traditional anisotropic conductive adhesives, such as silver (Ag), nickel (Ni), and gold (Au), often require high bonding pressure to achieve stable and reliable electrical interconnection. They are not suitable for certain scenarios such as small-sized chips and flexible substrates that require vertical electrical interconnection under low pressure.

[0054] Therefore, in the electronic packaging industry, developing a new type of anisotropic conductive adhesive to meet the requirements of reliable vertical electrical interconnection in low-voltage bonding scenarios is of great significance.

[0055] In view of this, embodiments of this application provide an anisotropic conductive adhesive, which, by weight parts, comprises:

[0056] 50 to 100 parts of epoxy resin;

[0057] Hardener 0.5 to 30 parts; and

[0058] The conductive particles with a core-shell structure consist of 10 to 40 parts, wherein the core layer of the conductive particles comprises liquid metal and the shell layer comprises a metal layer.

[0059] For example, the mass fraction of epoxy resin in the anisotropic conductive adhesive is 50 parts, 60 parts, 70 parts, 80 parts, 90 parts, 100 parts, or any two of the above values.

[0060] For example, the mass fraction of the curing agent in the anisotropic conductive adhesive is 0.5 parts, 1 part, 5 parts, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, or any two of the above values.

[0061] For example, the mass fraction of conductive particles in the anisotropic conductive adhesive is 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, or any value between any two of the above. For example, the thickness of the metal layer is 50 nm, 60 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, or any value between any two of the above.

[0062] In this application, core-shell structured conductive particles are added to the anisotropic conductive adhesive. The mass fraction of the conductive particles is 10 to 30 parts, which enables the conductive particles to have better plasticity or deformability. This is beneficial to improving the reliable vertical electrical interconnection of the anisotropic conductive adhesive in low-pressure bonding scenarios. It also helps to avoid the problem that when the conductive adhesive in the embodiment of this application is subjected to pressure, the shell of the conductive particles inside will rupture, causing the liquid metal inside the conductive particles to flow out, thereby causing the anisotropic conductive adhesive to fail.

[0063] It should be noted that the anisotropic conductive adhesive in this application differs from traditional conductive adhesives. Anisotropic conductive adhesives exhibit high conductivity in the pressure direction (e.g., the vertical direction) while displaying insulating properties in the non-pressure direction (e.g., the horizontal direction). This characteristic enables the anisotropic conductive adhesive to effectively prevent short circuits while ensuring a good electrical connection when connecting electronic components (such as chips and circuit boards).

[0064] The anisotropic conductive adhesive in this application embodiment can be used for encapsulating electronic components and electrodes, including flip chips, radio frequency identification, and display panels. Exemplarily, the anisotropic conductive adhesive is used to electrically connect the first electrical connection portion and the second electrical connection portion in the electronic component in the direction of bonding pressure.

[0065] It should be noted that the first electrical connection and the second electrical connection can be two electrical connection parts on the same electronic component or two electrical connection parts on different electronic components, and there is no limitation here. For example, the first electrical connection part is an external pin on a chip, and the second connection part is an electrode plate. The anisotropic conductive adhesive is applied to the first electrical connection part and / or the second connection part, and then temperature and vertical pressure are applied by a hot press head to cure the anisotropic conductive adhesive on the first electrical connection part and the second connection part, thereby realizing the electrical connection and encapsulation of the first electrical connection part and the second connection part.

[0066] In some embodiments of this application, the thickness of the metal layer is 50 nm to 500 nm. Further, the thickness of the metal layer is 60 nm to 200 nm. Further still, the thickness of the metal layer is 80 nm to 120 nm. This is beneficial for increasing the plasticity of the conductive particles and for further improving the bonding performance of the conductive adhesive in this application under low pressure. In some embodiments of this application, the particle size of the conductive particles is 1 μm to 5 μm. Exemplarily, the particle size (i.e., D50) of the conductive particles is 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or any two of the above values.

[0067] In some embodiments of this application, the liquid metal includes one or more of gallium, bismuth, cadmium, tin, lead, and indium. Further, the liquid metal includes at least one of gallium (Ga) and liquid metal alloys.

[0068] Specifically, the liquid metal alloy includes at least one of bismuth-gallium alloy, gallium-indium alloy, gallium-indium-tin alloy, and indium-tin alloy.

[0069] In some embodiments of this application, the material of the metal layer includes at least one selected from silver (Ag), copper (Cu), aluminum (Al), gold (Au), nickel (Ni), and zinc (Zn). Further, the material of the metal layer includes silver (Ag), copper (Cu), aluminum (Al), and gold (Au).

[0070] In some embodiments of this application, the liquid metal is a gallium-indium alloy, and the metal layer material includes silver (Ag), with the gallium-indium alloy encapsulated within the silver. This embodiment's structure exhibits higher shell density and greater deformability of the conductive particles, which is beneficial for further improving the stability of vertical electrical interconnects under low pressure when used in anisotropic conductive adhesives.

[0071] It should be noted that this application does not limit the type of epoxy resin. For example, the epoxy resin is selected from one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S type epoxy resin, linear phenolic epoxy resin, and alicyclic epoxy resin.

[0072] In some embodiments of this application, the curing agent is one or more of dicyandiamide, aromatic diamine, imidazole, and hydrazide.

[0073] In some embodiments of this application, the anisotropic conductive adhesive further includes a diluent. Further, by weight, the anisotropic conductive adhesive includes 1 to 50 parts of an active diluent. Exemplarily, the active diluent can be 1 part, 5 parts, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, or any value between any two of the above.

[0074] It should be noted that the diluent in this application is mainly used to adjust the viscosity of the conductive adhesive, making it easier to apply, coat, or print. The type of diluent is not limited. For example, the reactive diluent is selected from one or more of propylene glycidyl ether, phenyl glycidyl ether, diepoxy ethylene glycol diglycidyl ether, and resorcinol diglycidyl ether.

[0075] In some embodiments of this application, the anisotropic conductive adhesive further includes a thixotropic agent. Further, by weight, the anisotropic conductive adhesive includes 0.5 to 15 parts of the thixotropic agent. Exemplarily, the thixotropic agent is 0.5 parts, 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, or any value between any two of the above.

[0076] Understandably, thixotropic agents can cause anisotropic conductive adhesives to exhibit high viscosity in a static state, while their viscosity decreases when shear forces are applied (such as stirring or coating). This makes the anisotropic conductive adhesives more fluid during application, easier to coat or print, and allows them to return to a higher viscosity after standing, preventing dripping.

[0077] It should be noted that the type of thixotropic agent is not limited in this application. For example, the thixotropic agent is selected from one or more of fumed silica, precipitated silica, organobentonite, asbestos, kaolin, attapulgite, and emulsion-processed vinyl chloride compounds.

[0078] This application also provides a method for preparing anisotropic conductive adhesive, comprising the following steps:

[0079] S1 is used to prepare conductive particles with core-shell structures.

[0080] For example, firstly, a surfactant, liquid metal, and deionized water are added to a beaker and ultrasonically treated for a certain time using an ultrasonic cleaner to obtain a liquid metal microsphere suspension. Then, a reducing agent is added to the liquid metal microsphere suspension, and the mixture is ultrasonicated for a certain time. A prepared ammonia solution is added to a silver salt solution to obtain a silver ammonia solution. Then, at a certain temperature, the liquid metal microspheres are added to the silver ammonia solution, and the mixture is stirred to react, resulting in a dark brown LM@Ag conductive microsphere dispersion. Finally, the dispersion is washed and dried to obtain LM@Ag composite conductive microsphere powder.

[0081] Optionally, the surfactant is one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium fatty alcohol polyoxyethylene ether sulfate, and polyvinylpyrrolidone.

[0082] Optionally, the liquid metal may be one or more of gallium-indium liquid metal, gallium-indium-tin liquid metal, and indium-tin liquid metal.

[0083] Optionally, the reducing agent may be one or more of glucose, potassium sodium tartrate, formaldehyde, and dimethylaminoborane.

[0084] Optionally, the silver salt may be one or more of silver nitrate, silver chloride, silver bromide, and silver iodide halide.

[0085] Furthermore, the mass ratio of liquid metal to silver salt is 1 to 5. For example, the mass ratio of liquid metal to silver salt is 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, or any two of the above values.

[0086] Furthermore, the ultrasonic cleaning machine has an ultrasonic treatment time of 10 to 50 minutes. For example, the ultrasonic cleaning machine has ultrasonic treatment times of 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, and any two of the above values.

[0087] Furthermore, the chemical reaction temperature during the preparation of the composite conductive microspheres is 40–80°C. For example, the chemical reaction temperature is 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, or any two of the above values.

[0088] Furthermore, the chemical reaction time during the preparation of the composite conductive microspheres is 5–60 min. For example, the chemical reaction time during the preparation of the composite conductive microspheres is 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, or any two of the above values.

[0089] S2 mixes epoxy resin, curing agent and conductive particles in a preset ratio to obtain anisotropic conductive adhesive.

[0090] For example, epoxy resin, curing agent and conductive particles are added into a mixing device according to a preset ratio and mixed evenly to obtain anisotropic conductive adhesive.

[0091] This application also provides a polymer, which is formed by hot-pressing and curing the anisotropic conductive adhesive described above or the anisotropic conductive adhesive obtained by the above preparation method.

[0092] Further, the hot-press curing temperature is 120–190°C. For example, the hot-press curing temperature is 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, or any value between any two of the above.

[0093] Furthermore, the hot-press curing time is 4 to 15 seconds. For example, the hot-press curing time is 4 seconds, 5 seconds, 6 seconds, 7 seconds, 8 seconds, 9 seconds, 10 seconds, 11 seconds, 12 seconds, 13 seconds, 14 seconds, 15 seconds, or any two of the above values.

[0094] The anisotropic conductive adhesive of this application will be further described below with reference to specific embodiments and experimental tests.

[0095] Example 1

[0096] (1) Preparation of core-shell structured conductive particles

[0097] First, 0.5 g of polyvinylpyrrolidone, 0.5 g of gallium indium liquid metal, and 40 mL of deionized water were added to a beaker and ultrasonically treated for 20 minutes to obtain a liquid metal microsphere suspension. Then, 0.5 g of glucose was added to the liquid metal microsphere suspension and ultrasonicated for 10 minutes. Ammonia solution was added to 5 mL of silver nitrate solution (20 mg / mL) to obtain a silver ammonia solution. Then, at 55 °C, the liquid metal microspheres were added to the silver ammonia solution and stirred for 20 minutes under heating to obtain a dark brown LM@Ag conductive microsphere dispersion. Finally, the mixture was centrifuged, washed three times, and dried to obtain LM@Ag conductive microsphere powder.

[0098] The obtained metal microsphere suspension and LM@Ag conductive microsphere powder were tested using scanning electron microscopy and a particle size analyzer. The test results of the metal microsphere suspension are as follows: Figure 1 As shown, the test results of LM@Ag conductive microsphere powder are as follows: Figure 2As shown, the average particle size of the prepared LM@Ag conductive microsphere powder is about 3 μm, and the particle distribution is relatively uniform. Figure 3 Cross-sectional scanning electron microscope images and elemental distribution maps of LM@Ag conductive microspheres, from Figure 3 It can be seen that the average thickness of the metal shell is about 90 nm, and an intermediate phase is formed between the liquid metal and the metal shell.

[0099] (2) Preparation of anisotropic conductive adhesive and test samples

[0100] Weigh out the following components by weight: 100 parts of bisphenol A epoxy resin; 10 parts of diepoxy ethylene glycol diglycidyl ether; 20 parts of dicyandiamide; 5 parts of fumed silica; and 30 parts of LM@Ag composite conductive microspheres. Figure 1 The images show scanning electron microscope (SEM) images and particle size distribution diagrams of liquid metal ions, with an average particle size of approximately 3.2 μm.

[0101] Prepare the raw materials according to the above-mentioned components and mass proportions, and mix them evenly to obtain anisotropic conductive adhesive. Fill the prepared anisotropic conductive adhesive into a dispensing syringe. Apply the prepared anisotropic conductive adhesive based on LM@Ag composite conductive microspheres to bond an RFID chip (R6 chip, size 465μm×400μm), and achieve thermosetting curing using a hot press head. The hot pressing temperature is 190℃, the hot pressing time is 8s, and the hot pressing curing pressure is 1N. A schematic diagram of the thermosetting curing process is shown below. Figure 4 As shown, the SEM image of the cross-section of the anisotropic conductive adhesive-bonded RFID chip is as follows. Figure 5 As shown.

[0102] Example 2

[0103] Compared to Example 1, in Example 2 the curing agent is 5 parts of imidazole adduct (PN23J) and 15 parts of dicyandiamide, while other components remain unchanged.

[0104] Example 3

[0105] Compared to Example 1, in Example 3 the curing agent is 10 parts of imidazole adduct (PN23J) and 10 parts of dicyandiamide, while other components remain unchanged.

[0106] Example 4

[0107] Compared to Example 1, in Example 4 the curing agent was 15 parts of imidazole adduct (PN23J) and 5 parts of dicyandiamide, while other components remained unchanged.

[0108] Example 5

[0109] Compared to Example 1, in Example 5 the curing agent was 20 parts of imidazole adduct (PN23J), 0 parts of dicyandiamide, and other components remained unchanged.

[0110] Example 6

[0111] Compared to Example 3, the LM@Ag composite conductive microspheres in Example 6 have a mass fraction of 20 parts, while other components remain unchanged.

[0112] Example 7

[0113] Compared to Example 3, the LM@Ag composite conductive microspheres in Example 7 have a mass fraction of 10 parts, while other components remain unchanged.

[0114] Example 8

[0115] Compared to Example 3, the LM@Ag composite conductive microspheres in Example 8 have a mass fraction of 40 parts, while other components remain unchanged.

[0116] Example 9

[0117] Compared to Example 3, the difference lies in the amount of silver nitrate solution used in Example 9 during the preparation of the core-shell structured conductive particles. The resulting LM@Ag composite conductive microspheres had a shell thickness of approximately 60 nm, while other components remained unchanged.

[0118] Example 10

[0119] Compared to Example 3, in Example 10, the amount of silver nitrate solution used in the preparation of core-shell conductive particles was 8 ml. The prepared LM@Ag composite conductive microspheres had a shell thickness of approximately 200 nm, while other components remained unchanged.

[0120] Example 11

[0121] Compared to Example 3, the active epoxy diluent in Example 11 was 15 parts, while other components remained unchanged.

[0122] Example 12

[0123] Compared to Example 3, in Example 12, the amount of silver nitrate solution used in the preparation of core-shell conductive particles was 25 ml. The prepared LM@Ag composite conductive microspheres had a shell thickness of approximately 300 nm, while other components remained unchanged.

[0124] Compared to Example 3, in Example 13, copper nitrate was used instead of silver nitrate in the preparation of the core-shell structured conductive particles. The prepared conductive particles were LM@Cu composite conductive microspheres, with 30 parts by mass of conductive particles in the anisotropic adhesive, while other components remained unchanged.

[0125] Comparative Example 1

[0126] Compared to Example 3, in Comparative Example 1 (E), the conductive particles were liquid metal microspheres, with a weight of 30 parts, and other components remained unchanged.

[0127] Comparative Example 2

[0128] Compared to Example 3, in Comparative Example 1 (E), the conductive particles were irregular Ni powder, with a weight of 30 parts, and other components remained unchanged.

[0129] Comparative Example 3

[0130] Compared to Example 3, Comparative Example 1 (E) used irregular Ni powder as the conductive particles, with a weight of 120 parts, while other components remained unchanged.

[0131] Performance testing:

[0132] Adhesion strength: Peel strength was tested using a weld strength tester. Five samples were tested for each type of sample, and the average value of the results was calculated.

[0133] Rheological properties: Viscosity was tested using a high-speed rotary rheometer with a test interval of 0.2 mm.

[0134] Curing reaction: Tested using a DSC differential scanning calorimeter. The heating rate was 10℃ / min, and the temperature scan range was -50 to 250℃.

[0135] Cross-sectional observation of RFID tags: The cross-section of an RFID tag encapsulated with anisotropic conductive adhesive was observed using a scanning electron microscope.

[0136] RFID tag signal testing: Tested using a tag comprehensive performance tester.

[0137] Reliability testing: The samples were subjected to aging tests using a high-temperature and high-humidity accelerated aging test chamber and a thermal shock cycle test chamber. The high-temperature and high-speed accelerated aging test chamber was set at 85°C and RH 85%, while the thermal shock cycle conditions were -45°C to 85°C, with each cycle lasting 15 minutes. The samples were placed in both test chambers for 7 days, and the changes in label signals before and after aging were measured.

[0138] Table 1

[0139]

[0140]

[0141] Depend on Figure 5 It can be seen that the LM@Ag composite conductive microspheres sandwiched between the chip electrode and the Al antenna serve to conduct the circuit. In the non-bonding area, the LM@Ag composite conductive microspheres are dispersed in the resin matrix, and ACP (anisotropic conductive adhesive) serves to fix and provide mechanical support.

[0142] Furthermore, the working signal of the RFID tags encapsulated with the above-mentioned anisotropic conductive adhesive was tested using a tag comprehensive performance tester. As shown in Examples 1 to 13 and Table 1, the anisotropic conductive adhesive based on core-shell structure conductive particle composite conductive microspheres prepared in this application can enable the RFID tags to function normally under a bonding pressure of 1N. The anisotropic conductive adhesive obtained in the embodiments of this application is used to bond RFID chips, and the minimum startup power of the RFID chip is less than 10dBm. The anisotropic conductive adhesive in the embodiments of this application can effectively bond the chip to the RFID antenna.

[0143] As can be seen from Examples 1 to 5, when the curing agent in this application includes both imidazole adduct and dicyandiamide, the adhesive strength is higher, and it is beneficial to further reduce the minimum startup power of the RFID chip. Furthermore, when the ratio of imidazole adduct to dicyandiamide is close to 1:1, it is beneficial to further improve the adhesive performance of the anisotropic conductive adhesive and further reduce the minimum startup power of the RFID chip, achieving unexpected results.

[0144] As can be seen from Examples 3, 6 to 8, when the conductive particles in the anisotropic conductive adhesive are about 30 parts by mass, it is beneficial to further reduce the minimum start-up power of the RFID chip, and the anisotropic conductive adhesive still has high bonding strength, achieving unexpected results.

[0145] As can be seen from Examples 3, 9 and 10, when the shell thickness of the conductive particles is around 90nm, it is beneficial to improve the bonding strength of the anisotropic conductive adhesive and further reduce the minimum startup power of the RFID chip, achieving unexpected results.

[0146] As can be seen from Examples 3, 13, Comparative Example 1, and 2, when the mass fraction of conductive particles in the anisotropic conductive adhesive is the same, the conductive particles with a core-shell structure added in the embodiments of this application can significantly reduce the minimum startup power of the RFID chip. Furthermore, as can be seen from Examples 3 and 13, compared to a copper shell for the conductive particles, a silver shell for the conductive particles can further reduce the minimum startup power of the RFID chip, achieving unexpected results.

[0147] The technical solutions provided by the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. An anisotropic conductive adhesive, comprising, by weight parts: 50 to 100 parts of epoxy resin; Hardener: 0.5 to 30 parts; as well as The conductive particles with a core-shell structure consist of 15 to 40 parts, wherein the core layer of the conductive particles comprises liquid metal and the shell layer of the conductive particles comprises a metal layer. The thickness of the metal layer is 80nm to 250nm; the material of the metal layer includes at least one of silver, copper, aluminum, and gold. The curing agent is composed of imidazole and dicyandiamide, and the mass ratio of the imidazole to the dicyandiamide is (5~15):(5~15).

2. The anisotropic conductive adhesive as described in claim 1, characterized in that, The conductive particles have a particle size of 1 μm to 5 μm; and / or The anisotropic conductive adhesive further includes at least one of a diluent, a thixotropic agent, and an inorganic filler; and / or The core-shell structure contains 25 to 40 parts of conductive particles.

3. The anisotropic conductive adhesive as described in claim 2, characterized in that, The liquid metal includes one or more of gallium, bismuth-gallium alloy, gallium-indium alloy, gallium-indium-tin alloy, and indium-tin alloy; and / or The thickness of the metal layer is 80 nm to 200 nm; and / or The diluent is 1 to 50 parts by weight; and / or The diluent includes an active diluent selected from one or more of propylene glycidyl ether, phenyl glycidyl ether, diepoxylated ethylene glycol diglycidyl ether, and resorcinol diglycidyl ether; and / or The thixotropic agent is 0.5 to 15 parts by weight; and / or The thixotropic agent is selected from one or more of the following: fumed silica, precipitated silica, organobentonite, asbestos, kaolin, attapulgite, and emulsion-processed vinyl chloride compounds.

4. The anisotropic conductive adhesive as described in any one of claims 1 to 3, characterized in that, The liquid metal is a gallium-indium alloy, and the metal layer is made of silver; and / or The thickness of the metal layer is 80nm~100nm.

5. The anisotropic conductive adhesive as described in any one of claims 1 to 3, characterized in that, The epoxy resin is selected from one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S type epoxy resin, linear phenolic epoxy resin, and alicyclic epoxy resin.

6. The anisotropic conductive adhesive as described in any one of claims 1 to 3, characterized in that, Under a bonding pressure of 1N to 3N, the anisotropic conductive adhesive is electrically conductive in the direction of the bonding pressure and electrically insulating in the direction perpendicular to the bonding pressure.

7. A method for preparing an anisotropic conductive adhesive as described in any one of claims 1 to 6, the method comprising the following steps: Preparation of core-shell structured conductive particles; An anisotropic conductive adhesive is obtained by mixing epoxy resin, curing agent and the core-shell structure conductive particles according to a preset ratio. The core layer of the conductive particle comprises liquid metal, and the shell layer of the conductive particle comprises a metal layer with a thickness of 80 nm to 250 nm.

8. The preparation method according to claim 7, characterized in that, The steps for preparing core-shell structured conductive particles include: A liquid metal microsphere suspension and a silver ammonia solution were obtained; A suspension of liquid metal microspheres was added to a silver ammonia solution, and the mixture was stirred to obtain a dark brown conductive particle dispersion. The conductive particles with a core-shell structure are obtained by filtration and drying, wherein the core layer of the conductive particles consists of liquid metal and the shell layer consists of silver.

9. An electronic component, characterized in that, The electronic component includes a first electrical connection portion, a second electrical connection portion, and an anisotropic conductive adhesive as described in any one of claims 1 to 6, wherein the anisotropic conductive adhesive is used to electrically connect the first electrical connection portion and the second electrical connection portion in the direction of the bonding pressure.

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