Conductive particles, conductive materials, and connecting structures

Abstract

To solve the problem of surface treatment properties deteriorating over time, this invention provides surface-treated conductive particles with low powder resistance, excellent surface treatment properties and reliability, an anisotropic conductive material containing the same, and a connecting structure. [Solution] The conductive particles comprise a core, a conductive layer formed on the core, and a metal oxide layer formed on the conductive layer, and have low powder resistance and excellent stability. The present invention provides an anisotropic conductive material and a connecting structure containing these conductive particles.

Description

Technical Field

[0001] The present invention relates to conductive particles including a metal oxide layer on the surface of the conductive particles, an anisotropic conductive material, and a connection structure.

Background Art

[0002] Conductive particles are materials used in anisotropic conductive materials (ACF (Anisotropic Conductive Film), ACP (Anisotropic Conductive Paste), ACI (Anisotropic Conductive Ink), ACS (Anisotropic Conductive Sheet), ACA (Anisotropic Conductive Adhesive)). The anisotropic conductive material, particularly ACF, is used to make an electrical connection between an electrode corresponding to a panel pixel and a driving IC in order to realize the image of a display panel.

[0003] When the ACF (anisotropic conductive film) is used for display applications, as the resolution of the display increases, the pitch of the electrodes becomes smaller. When joining the upper and lower electrodes, a part of the conductive particles flows with the AC resin due to the flow of the AC resin, and the flowed conductive particles gather between the left / right electrodes, resulting in a problem of short circuit between the left and right electrodes.

[0004] To solve such problems, a method of forming a surface treatment using an organic substance system on the surface of the conductive particles has been proposed. The surface treatment mainly uses a method of adhering an organic substance system substance to the surface of the conductive particles by a physical or chemical method. Although the characteristics are good, there is a problem that the surface treatment substance physically adhered deteriorates over time and separates from the conductive particles, resulting in a decrease in the surface treatment characteristics and an increase in the powder resistance.

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention aims to provide surface-treated conductive particles with low powder resistance, excellent surface treatment characteristics and reliability, an anisotropic conductive material containing the same, and a connecting structure, by comprising a core and a conductive layer formed on the core, and by forming conductive particles by thin-film plating of a metal oxide layer on the surface of the conductive layer, thereby solving the problem of surface treatment characteristics deteriorating over time. [Means for solving the problem]

[0006] The conductive particles of the present invention preferably include a core, a conductive layer formed on the core, and a metal oxide layer formed on the conductive layer.

[0007] The metal in the metal oxide layer preferably includes Ni, Mn, Fe, Cu, Zn, Ag, Pd, Pt, Au, and Au or a combination thereof.

[0008] The metal oxide layer is NiO; Ni2O3;MnO;Mn2O3;MnO2;Mn2O7;FeO;Fe2O3;Fe3O4;Cu2O;CuO;ZnO;Ag2O;PdO;PtO2;Au2O3;Ni(NO3)2;Ni SO4;Mn(NO3)2;MnSO4;Fe(NO3)3;FeSO4;Fe2(SO4)3;Cu(NO3)2;CuSO4;Zn(NO3)2;ZnSO4;AgNO3;Pd(NO3)2 It is preferable to include PdSO4 and Pt(SO4)2 or a combination thereof, and more preferably to include Ni(NO3)2;Mn(NO3)2;FeSO4;Cu(NO3)2;ZnSO4;Ag2O;PtO2;PdO;NiSO4;FeO;Pd(NO3)2;AgNO3;Zn(NO3)2;Fe(NO3)3;and Fe2(SO4)3 or a combination thereof.

[0009] The thickness of the metal oxide layer is preferably 0.1 nm to 100 nm, more preferably 5 nm, 10 nm, or 20 nm to 90 nm, 80 nm, or 70 nm, and most preferably 30 nm to 70 nm.

[0010] Preferably, the conductive particles have a powder resistance increase rate of 300% or less after surface treatment.

[0011] The core preferably contains resin fine particles or organic / inorganic hybrid particles.

[0012] The conductive layer preferably contains Ni and one or more elements selected from the group consisting of P, B, Cu, Au, Ag, W, Mo, Pd, Co, and Pt.

[0013] In another aspect of the present invention, it is preferable to provide an anisotropic conductive material containing the conductive particles.

[0014] In another aspect of the present invention, it is preferable to provide a connecting structure that includes the anisotropic conductive material. [Effects of the Invention]

[0015] By applying a metal oxide layer to the surface of the conductive layer of the conductive particles of the present invention, it is possible to provide conductive particles with excellent surface treatment characteristics and reliability, an anisotropic conductive material containing the same, and a connecting structure. [Modes for carrying out the invention]

[0016] Hereinafter, some embodiments of the present invention will be described in detail with reference to illustrative drawings. In assigning reference numerals to the components in each drawing, the same reference numeral may be used for the same component as much as possible, even if it is shown in different drawings.

[0017] In describing the present invention, if a specific description of a related known configuration or function is deemed likely to obscure the gist of the invention, such detailed description may be omitted. Where "includes," "has," "is made," etc., as used herein, other elements may be added unless "only" is used. When a component is expressed singularly, it includes multiple components unless otherwise explicitly stated.

[0018] Furthermore, when describing the components of the present invention, terms such as First, Second, A, B, (a), (b), etc., may be used. These terms are used to distinguish a component from other components, and do not limit the essence, order, sequence, or number of the component in question.

[0019] In descriptions of the positional relationships of constituent elements, when it is stated that two or more constituent elements are "linked," "joined," or "connected," it should be understood that this may mean that the two or more constituent elements are directly "linked," "joined," or "connected," but also that other constituent elements may be further "intervened" to "link," "join," or "connected" to the two or more constituent elements. Here, other constituent elements may be included in one or more of the two or more constituent elements that are "linked," "joined," or "connected" to each other.

[0020] Furthermore, when a component such as a layer, film, region, or plate is said to be "on top of" or "above" another component, this should be understood to include not only cases where it is "directly above" another component, but also cases where another component is located in between. On the other hand, when a component is said to be "directly above" another component, this should be understood to mean that there is no other component in between.

[0021] In descriptions of the temporal sequence related to components, operating methods, or manufacturing methods, for example, when describing temporal or sequential relationships using phrases such as "after," "following," "next," or "before," it may include non-consecutive occurrences unless "immediately" or "directly" is used.

[0022] Furthermore, if numerical values ​​or corresponding information for a component are mentioned, unless otherwise explicitly stated, these values ​​or corresponding information may be interpreted as including a range of errors that can occur due to various factors (e.g., process factors, internal or external shocks, noise, etc.).

[0023] The terms used in this specification and the appended claims are as follows, unless otherwise specified, within the scope not departing from the spirit of the present invention.

[0024] Hereinafter, embodiments of the present invention will be described in detail. However, this is shown as an example and the present invention is not limited thereby. The present invention is defined only by the scope of the claims described later.

[0025] Hereinafter, each component will be specifically described.

[0026] 1. Conductive particles The conductive particles according to an embodiment of the present invention include a core, a conductive layer provided on the core, and a metal oxide layer provided on the conductive layer.

[0027] The core is an insulating bead, has extremely low electrical conductivity, can be manufactured from resin microparticles or organic / inorganic hybrid particles, and is made of a material that does not break when used in an anisotropic conductive material and the conductive particles are electrically connected. That is, when the conductive particles according to an embodiment of the present invention receive a force within the range for electrical connection between electrodes, the insulating beads inside the conductive particles deform very well but do not break.

[0028] The resin microparticles can use at least one monomer selected from the group consisting of urethane-based, acrylate-based, benzene-based, epoxy-based, and amine-based monomers or a copolymer obtained by polymerizing the monomers using methods such as seed polymerization, dispersion polymerization, suspension polymerization, and emulsion polymerization.

[0029] The acrylate monomers mentioned above include methyl methacrylate (MMA), ethyl methacrylate, propyl methacrylate, butyl methacrylate, benzyl methacrylate, methyl acrylate (MA), ethyl acrylate (EA), propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, 1,6-hexanediol diacrylate, tetramethylol methane tetraacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacylate, polypropylene glycol diacrylate, and polyethylene glycol dimethacrylate. One or more types selected from the group consisting of (dimethacylate) can be used.

[0030] The benzene monomers include divinylbenzene monomers and styrene monomers.

[0031] The styrene monomer can be one or more selected from the group consisting of styrene, α-methylstyrene, β-methylstyrene, p-methylstyrene, ethylstyrene, hydroxystyrene, vinylxylene, monochlorostyrene, dichlorostyrene, dibromostyrene, and vinylnaphthalene.

[0032] The amine monomers include amide monomers and imide monomers.

[0033] The aforementioned amide monomer can be one or more selected from the group consisting of acrylamide, N-isopropylacrylamide, methacrylamide, hexamethylenediamine, adipic acid, caprolactam, laurolactam, N,N-dimethylacrylamide, N,N'-methylenebisacrylamide, terephthaloyl chloride, and p-phenylenediamine.

[0034] The aforementioned imide monomer can be one or more selected from the group consisting of pyromellitimide, naphthalimide, pyridinedimide, imidazole imide, tetracarboxyimide, benzoimide, phenylimide, diethylimide, isophthalimide, and imidazophenone imide.

[0035] The aforementioned organic / inorganic hybrid particles preferably have an insulating bead (core)-shell structure. If the insulating beads are made of an organic material, the shell is made of an inorganic material, and vice versa. The reason for forming the shell is selected considering the properties of the resin used in the anisotropic material.

[0036] When insulating beads are made of organic / inorganic hybrid particles, the organic / inorganic hybrid particles preferably have a core-shell structure. If the core is organic, the shell is inorganic, and if the core is inorganic, the shell is organic.

[0037] In this case, the organic material can be a polymer using the monomers used in the aforementioned resin fine particles, while the inorganic material can be an oxide (SiO2, TiO2, Al2O3, ZrO2, etc.), a nitride (AlN, Si3N4, TiN, BaN, etc.), or a carbide (WC, TiC, SiC, etc.).

[0038] The shell can be formed by methods such as chemical coating, Sol-Gel method, spray coating, CVD (chemical vapor deposition), PVD (physical vapor deposition), and plating.

[0039] Furthermore, the conductive layer of the present invention is a layer for imparting conductivity to conductive particles, and can be composed of Ni and one or more materials selected from the group consisting of P; B; Cu; Au; Ag; W; Mo; Pd; Co and Pt.

[0040] Specifically, the alloy may include Ni and be composed of two elements such as Ni-P, Ni-B, Ni-W, Ni-Mo, and Ni-Co, or three elements such as Ni-P-Pd, Ni-B-Pd, Ni-P-Co, Ni-B-Co, Ni-PW, and Ni-BW, or even four or more elements, but is not limited to these.

[0041] The thickness of the conductive layer containing Ni is preferably 80 nm to 400 nm, more preferably 90 nm to 300 nm, and most preferably 100 nm to 250 nm.

[0042] If the thickness of the conductive layer is less than the aforementioned range, the electrical resistance of the conductive particles increases. If it exceeds the aforementioned range, even slight deformation of the conductive particles under heating / pressure bonding conditions for anisotropic conductive materials can cause delamination between the conductive layer and insulating beads, potentially reducing the reliability of the product.

[0043] The conductive layer can be composed of a multilayer comprising a first layer containing Ni and a second layer containing one or more elements selected from Au, Ag, Pt, and Pd in ​​addition to the first layer. The metal layer of the second layer enhances the electrical conductivity of the conductive particles and prevents oxidation of the conductive layer.

[0044] Furthermore, the method for forming the precious metal layer can use, but is not limited to, conventionally known techniques such as sputtering, plating, and vapor deposition.

[0045] Furthermore, the conductive layer may include protrusions.

[0046] The shape of the protrusion may be spherical, elongated, or a cluster of multiple particles, but is not limited thereto. The most preferred shape is one that narrows towards the ends.

[0047] The method for forming the protrusions is not particularly limited. The protrusions may be grown integrally with the conductive layer, or the conductive layer may be formed after attaching nano-sized particles to the core, or a first conductive layer may be formed on the core, nano-sized particles may be attached, and a second conductive layer of the same or different material as the first conductive layer may be formed to form the protrusions.

[0048] The size of the protrusion is preferably 50 nm to 500 nm, more preferably 100 nm to 350 nm.

[0049] Insulating microparticles are particles formed in a first region on the conductive layer to prevent short circuits with adjacent electrodes when conductive particles are used as an anisotropic conductive material, and can also be provided on protrusions if they are present.

[0050] The insulating fine particles can be made of insulating resin particles or inorganic particles. The resin particles contain at least one or more resins selected from the group consisting of styrene or styrene-based resins containing one or more C1 alkyl groups, acrylates or methacrylates containing one or more C1 alkyl groups, and acrylate-based resins containing diacrylate or dimethacrylate at both ends of a glycol with one or more C1. The inorganic particles contain one or more materials selected from the group consisting of trimethoxysilane-based resins containing acrylic groups, phenyl groups, and vinyl groups.

[0051] The particle size may be 90 nm or larger to exhibit an insulating effect, but to ensure connection resistance and insulation resistance, it is preferably 100 nm to 300 nm, and more preferably 100 nm to 250 nm.

[0052] Furthermore, in order to improve the insulating and conductive effects, insulating fine particles of different particle sizes may be mixed and used, or organic and inorganic particles may be mixed and used.

[0053] As a method for attaching insulating microparticles to the surface of conductive particles, a method (wet method) is used in which the solvent, conductive particles, and insulating microparticles are mixed together and attached. The insulating microparticles are polymers having a first substituent on their surface that has a bonding force with the metal of the conductive layer of the conductive particles, and the insulating microparticles are attached to the conductive layer or protrusions by the first substituent.

[0054] The first substituent is any heteroatom or substituent that has a bonding force to the metal, such as a covalent bond or a polar bond, or has a high affinity for the metal and can therefore be attached to and fixed to the metal surface. Specifically, it is selected from the group consisting of heterogroups, ether groups, carbonate groups, and hydroxyl groups, and the heterogroup may preferably be at least one selected from the group consisting of sulfur, phosphorus, nitrogen, and oxygen.

[0055] In this case, it is preferable that the insulating fine particles adhere to 5% to 40% of the total surface area of ​​the outer surface of the conductive layer (including any protrusions). If the percentage is less than 5%, the proportion of insulating particles is low, making it difficult to obtain an insulating effect. If it exceeds 40%, the problem arises that the connection resistance increases due to the large number of insulating fine particles. Therefore, even when insulating fine particles are attached, a portion of the surface of the conductive layer of the conductive particles remains open.

[0056] 2. Metal oxide layer The metal oxide layer according to the embodiment of the present invention is a layer formed on a conductive layer to prevent bonding between insulating fine particles, and is formed in a second region on the conductive layer other than the first region formed on the conductive layer.

[0057] In other words, it is preferable that the metal oxide layer be made of a material that is reactive with the metal in the conductive layer but not with the insulating fine particles.

[0058] The material constituting the metal oxide layer is preferably a metal oxide.

[0059] The metal oxide layer of the present invention, composed of a metal oxide, bonds firmly to the conductive layer composed of metal, exhibiting excellent surface treatment properties and reducing powder resistance, thereby improving the reliability of conductive particles.

[0060] The metal in the metal oxide preferably includes Ni, Mn, Fe, Cu, Zn, Ag, Pd, Pt, and Au or a combination thereof, and more preferably Ni, Cu, Mn, Pd, and Pt or a combination thereof.

[0061] The metal oxide is NiO;NI2O3;MnO;Mn2O3;MnO2;Mn2O7;FeO;Fe2O3;Fe3O4;Cu2O;CuO;ZnO;Ag2O;PdO;PtO2;Au2O3;N i(NO3)2;NiSO4;Mn(NO3)2;MnSO4;Fe(NO3)3;FeSO4;Fe2(SO4)3;Cu(NO3)2;CuSO4;Zn(NO3)2;ZnSO4;AgNO3;P It is preferable to include d(NO3)2;PdSO4 and Pt(SO4)2 or a combination thereof, and more preferably to include Ni(NO3)2;Mn(NO3)2;FeSO4;Cu(NO3)2;ZnSO4;Ag2O;PtO2;PdO;NiSO4;FeO;Pd(NO3)2;AgNO3;Zn(NO3)2;Fe(NO3)3; and Fe2(SO4)3 or a combination thereof.

[0062] The thickness of the metal oxide layer is preferably 0.1 nm to 100 nm, more preferably 5 nm, 10 nm, or 20 nm to 90 nm, 80 nm, or 70 nm, and most preferably 30 nm to 70 nm.

[0063] The reason why it is preferable for the thickness of the metal oxide layer to be within an appropriate range is that if it is too thin, its protective function will be insufficient, reducing durability and stability, and if it is too thick, the electrical resistance will increase significantly, reducing conductivity. Within the appropriate thickness range, the metal oxide layer can effectively protect the particles without significantly hindering the flow of current, maintaining a good balance between electrical performance and physical stability. In particular, within the most preferable thickness range, the oxide layer performs a sufficient protective function while minimizing unnecessary increases in resistance, optimizing the reliability and lifespan of the conductive particles. Therefore, limiting the thickness of the metal oxide layer within an appropriate range is important for ensuring product performance and durability.

[0064] The conductive particles of the present invention preferably have a powder resistance increase rate of 300% or less after surface treatment of the metal oxide layer, more preferably 280% or less, 260% or less, 240% or less, or 220% or less, and most preferably 200% or less.

[0065] When the rate of increase in powder resistance after the formation of the metal oxide layer is within the range described above, the electrical properties of the conductive particles are maintained, current flows smoothly, and the metal oxide layer enhances the durability and stability of the particles. On the other hand, if the rate of increase is too high, it can hinder current flow, degrade electrical performance, and the thickening of the oxide layer may lead to physical damage to the particles and a shortened lifespan. Therefore, controlling the rate of increase in resistance within an appropriate range is important for improving electrical performance and material reliability.

[0066] The conductive particles of the present invention preferably have a resistance increase rate of 300% or less after 85 / 85 reliability evaluation relative to the initial resistance, more preferably 280% or less, 260% or less, 240% or less, or 220% or less, and most preferably 200% or less.

[0067] The reason why it is preferable for the resistance increase rate after the 85 / 85 reliability evaluation relative to the initial resistance to be within a specific range is that the electrical properties of the conductive particles are stably maintained, current flow is smooth, and the metal oxide layer adequately performs the durability and protective functions of the particles. The lower the range of the increase rate, the more the deterioration of electrical performance is minimized, and the reliability and lifespan of the material are further improved. On the other hand, if the resistance increase rate is too high, electrical conduction becomes difficult, the electrical performance deteriorates significantly, and the oxide layer becomes thicker, leading to physical damage, delamination, and cracking of the particles, shortening the material lifespan and potentially increasing the defect rate in the manufacturing process. Therefore, controlling the resistance increase rate to below an appropriate level is extremely important to ensure the electrical efficiency and durability of the product.

[0068] The aforementioned 85 / 85 reliability evaluation is preferably performed over a period of 72 hours under environmental conditions of 85°C and 85%RH humidity.

[0069] 3. Method for manufacturing conductive particles and metal oxide layer A method for producing conductive particles according to an embodiment of the present invention includes a core supply step S1, a conductive layer formation step S2, a selective insulating fine particle attachment step S3, a surface treatment step S4, and a drying step S5.

[0070] In this case, the core supply step S1 includes the core particle synthesis step S1a and the plating catalyst activation step S1b.

[0071] First, in the core particle synthesis step S1a, monomers such as urethane-based, styrene-based, acrylate-based, benzene-based, epoxy-based, amine-based, and imide-based monomers, or modified monomers thereof, or mixed monomers of the above monomers are polymerized by methods such as seed polymerization, dispersion polymerization, suspension polymerization, and emulsion polymerization to produce a copolymer and form a core.

[0072] When the core is a hybrid particle, when the core has a core-shell structure, when the core is organic, the shell is inorganic, and when the core is inorganic, the shell is organic. The organic material used here is the monomer, modified monomer, or mixed monomer, and the inorganic material used here can be oxides such as SiO2, TiO2, Al2O3, and ZrO2, nitrides such as AlN, Si3N4, TiN, and BaN, carbides such as WC, TiC, and SiC, etc.

[0073] Methods for forming the shell include chemical coating, sol-gel coating, spray coating, CVD (chemical vapor deposition), PVD (physical vapor deposition), and plating.

[0074] Furthermore, forms in which inorganic particles are dispersed within an organic matrix are also possible, as are forms in which organic particles are dispersed within an inorganic matrix, and even forms in which organic and inorganic materials are dispersed in a 50:50 ratio.

[0075] As an example, ethoxylate triacrylate monomers and ethoxylate diacrylate monomers are used as the organic substances, and a solution mixed with a solvent and polymerization initiator is dispersed. In this dispersion process, homogenization using ultrasound may be included.

[0076] Furthermore, a solution containing a dispersion stabilizer and a surfactant is added to the dispersion liquid, and a polymerization process is carried out under elevated temperature conditions to form a core.

[0077] Next, in the plating catalyst activation step S1b, the core particles produced in step S1a are activated with an electroless plating catalyst. At this time, the plating catalyst used in the plating catalyst activation step S1b may be replaced with one in which small metal or inorganic particles are attached to insulating fine particles, as long as it can provide the same effect.

[0078] Specifically, in the plating catalyst activation step S1b, after treating the core particles with a surfactant, pre-treating them using various known methods to sensitize the electroless plating catalyst, and then immersing the sensitized core particles in a solution containing a precursor of the electroless metal plating catalyst to perform the activation treatment.

[0079] The core particles activated in this way are placed in a solution containing a strong acid and stirred at room temperature to accelerate the process, thereby obtaining catalytically treated core particles for electroless plating.

[0080] Next, the conductive layer formation step S2 with protrusions includes the core dispersion step S2a and the conductive layer formation step S2b.

[0081] In the core dispersion step S2a, the core is immersed in an alloy plating solution that forms a conductive layer and dispersed. The alloy plating solution is prepared by sequentially dissolving alloy element precursors, complexing agents, lactic acid, stabilizers, and surfactants.

[0082] The catalyst-treated core particles obtained in step S1b are added to the manufactured plating solution and dispersed using an ultrasonic homogenizer.

[0083] Adjusting the pH of the dispersion solution to pH 5.5-6.5 using ammonia water or the like is preferable because it improves the adhesion and dispersibility between the insulating fine particles and the conductive layer in the initial Ni reduction reaction in the conductive layer formation step S2b described later. If the pH is less than 5.5, for example pH 4 or lower, adhesion and dispersibility are good, but the reactivity is too low, and some particles may not be plated. If the pH is higher than 6.5, abnormal deposition of Ni may cause the surface of the conductive layer to become rough, resulting in poor adhesion and dispersibility.

[0084] Next, a process S2b is performed to form a conductive layer on the core that has been immersed in the dispersed plating solution. The number of conductive layers, the material, the method of formation, or the method of forming the protrusions are not limited. The thickness of the conductive layer is formed to be 80 nm to 400 nm, and the protrusions may be formed integrally or separately. For example, the protrusions may be grown integrally with the conductive layer, or nano-sized particles may be attached to the core and then the conductive layer may be formed, or a first conductive layer may be formed on the core, nano-sized particles may be attached, and then a second conductive layer of the same or different material as the first conductive layer may be formed to form the protrusions.

[0085] One example of forming the protrusions integrally with the conductive layer is to add one or more precursors selected from P and B to the nickel-based alloy plating solution in the core dispersion step S2a, and then in the conductive layer formation step S2b having the protrusions, to divide and add alloy elements containing precursors of one or more elements selected from Cu, Au, Ag, W, Mo, Pd, Co, and Pt to the dispersed plating solution, thereby forming a conductive layer having protrusions with a concentration gradient.

[0086] In this case, the alloying elements to be added in portions can be added in 2 to 5 portions at intervals of 10 to 30 minutes, or in 2 to 4 portions at intervals of 15 to 25 minutes. In this case, the amount added can be added in portions with increased content, or added continuously if necessary, but it is preferable to increase the amount added in accordance with the addition rate at regular intervals so that the concentration can be increased as you move towards the protrusion.

[0087] Before and after the aforementioned phased addition, it is preferable to maintain the pH of the plating solution within a controlled range depending on the type of alloying element added to form a conductive layer with protrusions. For example, when adding a P precursor, it is preferable to maintain the pH within the range of 5.5 to 6.0, and when adding a B precursor, it is preferable to maintain the pH within the range of 8.5 to 9.0. In this case, if the pH of the plating solution is too low, the reactivity will decrease and problems will occur in protrusion formation, and conversely, if the pH is too high, excessive abnormal deposition will occur, disrupting the balance of the plating solution and resulting in defective plating.

[0088] Furthermore, applying temperature-raising conditions is even more preferable because it prevents excessive abnormal precipitation in the protrusion formation mechanism and allows for the formation of desired protrusions.

[0089] Step S3, which involves attaching insulating microparticles, is a step in which insulating microparticles are selectively attached to the conductive layer. There are dry and wet methods for attaching insulating microparticles to the surface of conductive particles, but in this embodiment, the wet method is preferably used. This is because the dry method involves attaching particles by colliding them with each other at high temperatures, making it difficult to achieve uniform particle attachment.

[0090] The wet method is a method of mixing a solvent with conductive particles and insulating fine particles and depositing them together, wherein a substituent that is reactive with the metal in the conductive layer of the conductive particles is attached to the surface of the insulating fine particles, thereby depositing the insulating fine particles onto the conductive layer or protrusions. That is, the surface of the insulating fine particles is provided with substituents to improve reactivity with the metal on the surface of the conductive layer or protrusions of the conductive particles. As such substituents, one selected from the group consisting of heterogroups, thiol groups, carbonate groups, and hydroxyl groups can be used. The heterogroup can preferably be at least one selected from the group consisting of sulfur, phosphorus, nitrogen, and oxygen.

[0091] Furthermore, substituents can be provided not only on the surface of the insulating fine particles, but also on the surface of the conductive particles. In this case, it is preferable that the substituents on the insulating fine particles and the substituents on the conductive particles have a strong bonding force with each other.

[0092] In the wet process, insulating microparticles are not formed on the entire surface of the conductive particles, but rather on 5% to 40% of the total surface area of ​​the outer surface of the conductive layer (including any protrusions). This is because the insulating microparticles have a surface that is highly compatible with the conductive particles, resulting in a low tendency for them to adhere to each other. Consequently, some of the conductive particles' surfaces remain open, exposing the conductive layer.

[0093] On the other hand, in order to improve the insulating and conductive effects, insulating fine particles of different particle sizes may be mixed and used, or organic / inorganic particles may be mixed and used.

[0094] In order to ensure that insulating microparticles adhere better to the surface of conductive particles, the adhesion force of the insulating microparticles and the area over which the insulating microparticles adhere to the conductive particles can be adjusted by having substituents not only on the surface of the insulating microparticles but also on the surface of the conductive particles.

[0095] Surface treatment step S4 is a step of introducing a metal oxide layer to the surface of the conductive particles.

[0096] The surface treatment step is preferably carried out by adding a metal oxide or a hydrate of a metal oxide, a conductive particle surface modifier (such as stearic acid), distilled water (DI water), and ethanol and stirring, and then adding conductive particles to the solution and heating it at a high temperature.

[0097] The metal oxide layer of the present invention, composed of a metal oxide, firmly bonds with the conductive layer composed of metal, exhibiting excellent surface treatment properties and reducing powder resistance, thereby improving the reliability and stability of conductive particles.

[0098] The metal in the metal oxide preferably includes Ni, Mn, Fe, Cu, Zn, Ag, Pd, Pt, and Au or a combination thereof, and more preferably Ni, Cu, Mn, Pd, and Pt or a combination thereof.

[0099] The metal oxide is NiO;NI2O3;MnO;Mn2O3;MnO2;Mn2O7;FeO;Fe2O3;Fe3O4;Cu2O;CuO;ZnO;Ag2O;PdO;PtO2;Au2O3;N i(NO3)2;NiSO4;Mn(NO3)2;MnSO4;Fe(NO3)3;FeSO4;Fe2(SO4)3;Cu(NO3)2;CuSO4;Zn(NO3)2;ZnSO4;AgNO3;P Preferably, it contains d(NO3)2;PdSO4 and Pt(SO4)2 or a combination thereof, and more preferably, Ni(NO3)2;Mn(NO3)2;Fe2SO4;Cu(NO3)2;ZnSO4;Ag2O;PtO2;PdO;NiSO4;FeO;Pd(NO3)2;AgNO3;Zn(NO3)2;Fe(NO3)3; and Fe2(SO4)3 or a combination thereof.

[0100] The thickness of the metal oxide layer is preferably 0.1 nm to 100 nm, more preferably 5 nm, 10 nm, or 20 nm to 90 nm, 80 nm, or 70 nm, and most preferably 30 nm to 70 nm.

[0101] Drying step S5 is a process of drying the conductive particles manufactured by the wet process. The drying process is carried out in the range of 100 to 200°C, although the drying temperature varies depending on the type of solvent.

[0102] The drying process is a step to dry the solvent when insulating fine particles are wet-bonded onto conductive particles. Since the conductive particles are in a solution state with the solvent, the drying process is necessary to ensure that the correct amount is added during the production of anisotropic conductive materials to obtain the desired conductive particle density and connection resistance.

[0103] In the drying step of the present invention, as described above, a metal oxide layer is formed, and due to substituents on selectively attached insulating fine particles, a phenomenon occurs during the drying process in which insulating fine particles attached to the surface of conductive particles and the surface (conductive layer) of conductive particles without insulating fine particles attached adhere to each other. As time passes after drying, a phenomenon occurs in which adjacent conductive particles and insulating fine particles naturally adhere to each other, and the problem of aggregation of multiple particles occurring during the final ACF production does not occur.

[0104] Furthermore, by forming a metal oxide layer on the outer surface of the conductive layer, in which conductive particles have hydrophobic properties and substituents capable of bonding with metal, the phenomenon of insulating fine particles adhering to the conductive layer of other conductive particles is prevented, while the metal oxide layer is not formed on the outer surface of the insulating fine particles. This prevents an increase in insulating conductive particles that are aggregated due to the reaction of surface treatment materials with each other, which would occur if a metal oxide layer were formed over the entire outer surface of the conductive particles.

[0105] 4. Anisotropic conductive materials An anisotropic conductive material can be manufactured by dispersing the conductive particles of the present invention in a resin binder. Examples of anisotropic conductive materials include anisotropic conductive paste, anisotropic conductive film, and anisotropic conductive sheet. After uniformly dispersing the conductive particles in the resin binder, it may be used as an anisotropic conductive paste, or it may be used as an anisotropic film by thinly coating the surface of release paper.

[0106] In this case, the resin binder is not particularly limited. Examples include vinyl resins such as styrene-based, acrylic-based, and vinyl acetate-based resins; thermoplastic resins such as polyolefin-based and polyamide-based resins; and curable resins such as urethane-based and epoxy-based resins. The resin may be used alone or in combination of two or more types. In particular, it is preferable that the resin binder contains monomers from the same series as the core mentioned above, as this allows it to exhibit similar behavior under changing temperature conditions.

[0107] The binder resin may be used with a radical initiator such as BPO (Benzoyl Peroxide), a photoinitiator such as TPO (Trimethylbenzoyl Phenylphosphinate), or an epoxy-based latent curing agent such as HX3941HP, either alone or in combination, for polymerization or curing purposes.

[0108] Furthermore, other substances can be added to the resin binder, provided they do not interfere with achieving the objectives of the present invention. Examples include colorants, softeners, heat stabilizers, light stabilizers, antioxidants, and inorganic particles.

[0109] 5. Connection Structure In the present invention, when the aforementioned conductive particles are used, the application, structure, and material of the connecting structure are not particularly limited. That is, the connecting structure connects circuit boards using the conductive particles or anisotropic conductive material of the present invention. For example, it can be used as a method to electrically connect a display driver IC and an FPC. The connecting structure of the present invention can prevent short circuits between the left and right electrodes during joining and prevent malfunctions of the circuit.

[0110] The following describes specific examples of synthesis and embodiments of the present invention, but the examples of synthesis and embodiments of the present invention are not limited thereto.

[0111] <Examples> I. Manufacturing of conductive particles 1) Synthesis of insulating core particles To prepare the first solution, 1100g of monomer TMMT (Tetramethylol Methane Tetraacrylate), 400g of divinylbenzene, 15g of 1,6-hexanediol diacrylate, and 30g of styrene were placed in a 3L glass beaker, and after adding 5g of the initiator BPO, the mixture was treated in a 40kHz ultrasonic bath for 10 minutes. To prepare the second solution, 3,000g of deionized water, 500g of the dispersion stabilizer PVP (Polyvinylpyrrolidone)-30K, and 200g of the surfactant Solusol (Dioctyl sulfosuccinate sodium salt) were dissolved in a 5L PP beaker.

[0112] The first and second solutions were placed in a 50 L reactor, 40,000 g of deionized water was added, and the mixture was treated with an ultrasonic homogenizer (20 kHz, 600 W) for 90 minutes. The solution was then heated to 35°C while rotating at 120 rpm, maintained at that temperature for 3 hours, and then heated again to 85°C. After the solution reached 85°C, it was maintained at that temperature for 16 hours to perform the polymerization process. The polymerized microparticles were subjected to filtration, washing, classification, and drying to obtain core resin microparticles. The average diameter of the manufactured core resin microparticles was measured using a Particle Size Analyzer (BECKMAN MULTISIZER TM3) and the mode value was used. The number of core microparticles measured at this time was 75,000, and the average diameter was 3.51 μm.

[0113] 2) Formation of conductive layer around insulating core particles (1) Catalyst treatment process 30 g of the manufactured insulating core particles were placed in a solution of 800 g of deionized water, 0.5 g of the surfactant Triton X100, and 10 g of sulfuric acid, and treated in an ultrasonic bath for 1 hour to perform a washing and degreasing process to remove excess unreacted monomers and oily components present in the insulating core particles. At the end of the washing and degreasing process, three rinses were performed using deionized water at 45°C.

[0114] The insulating core particles, after the degreasing and washing steps described above, were placed in a solution prepared by dissolving 150 g of stannous chloride and 300 g of 35-37% hydrochloric acid in 600 g of deionized water. The particles were then immersed and stirred at 30°C for 30 minutes to sensitize them, followed by three washes with water.

[0115] Sensitized insulating cores were placed in a solution of 1 g palladium chloride, 200 g 35-37% hydrochloric acid, and 600 g deionized water, and activated at 40°C for 1 hour. Ultrasound was applied during the activation process using an ultrasonic bath. After the activation process, the cores were rinsed with water three times.

[0116] The activated insulating core was placed in a solution of 100 g of 35-37 wt% hydrochloric acid aqueous solution and 600 g of deionized water, and the mixture was stirred at room temperature for 10 minutes to accelerate the treatment. After the accelerated treatment, the core was washed with water three times to obtain a catalytically treated insulating core for electroless plating.

[0117] (2) Plating process Solution (a) was prepared by sequentially dissolving 70g of nickel sulfate as the Ni salt, 5g of sodium acetate and 2g of lactic acid as complexing agents, 0.001g of Pb acetate and 0.001g of sodium thiosulfate as stabilizers, and 1g of PEG-600 as a surfactant in a 5L reactor. The catalyst-treated insulating core was added to the prepared solution (a) and dispersed using an ultrasonic homogenizer for 10 minutes. After dispersion, the pH of the solution was adjusted to 8.0 using ammonia water. Solution (c) was prepared by dissolving 300g of deionized water, 33g of DMAB as a reducing agent, and 0.002g of sodium thiosulfate as a stabilizer in a 1L beaker. Solution (d) was prepared by dissolving 500g of deionized water, 155g of nickel sulfate, and 10g of sodium hydroxide in a 1L beaker.

[0118] While maintaining the temperature of solution (b) in the 5L reactor at 20°C, solution (c) was added at a rate of 5 g per minute using a metering pump, and the reactor temperature was heated and maintained at a rate of 0.33°C until it reached 35°C. The pH of solution (b) in the 5L reactor was adjusted to 8.0 by adding more aqueous ammonia until the solution temperature reached 35°C, and no further aqueous ammonia was added after 75°C.

[0119] Five minutes after solution (c) was added, solution (d) was added to the 5L reactor at a rate of 20 g per minute using a metering pump. After the addition of solution (c) was completed, the reactor was held for 30 minutes to obtain Ni-plated conductive particles.

[0120] II. Surface treatment of conductive particles (Example 1) Ni(NO3)2 surface treatment Add 20g of Ni(NO3)2·6H2O, 20g of stearic acid, and 50g of DI water to the solution and stir for 30 minutes while adding 50mL of ethanol. Then, add 20g of the conductive particles produced in step I to the solution, seal it in an autoclave, heat at 120°C for 30 minutes, and after cooling to room temperature, wash the surface-treated conductive particles with DI water and then dry in a convention oven for 12 hours.

[0121] (Example 2) Ni(NO3)2 surface treatment The surface treatment is performed in the same manner as in Example 1, except that the autoclave is sealed and heated for 45 minutes.

[0122] (Example 3) Ni(NO3)2 surface treatment The surface treatment is performed in the same manner as in Example 1, except that the area is sealed in an autoclave and heated for 1 hour.

[0123] (Example 4) Ni(NO3)2 surface treatment The surface treatment is performed in the same manner as in Example 1, except that the area is sealed in an autoclave and heated for 3 hours.

[0124] (Example 5) Ni(NO3)2 surface treatment The surface treatment is performed in the same manner as in Example 1, except that the area is sealed in an autoclave and heated for 6 hours.

[0125] (Example 6) Mn(NO3)2 surface treatment Add 20g of Mn(NO3)2·4H2O, 20g of stearic acid, and 50g of DI water to the solution and stir for 30 minutes while adding 50mL of ethanol. Then, add 20g of the conductive particles produced in step I to the solution, seal it in an autoclave, heat at 120°C for 1 hour, and after cooling to room temperature, wash the surface-treated conductive particles with DI water and then dry in a convention oven for 12 hours.

[0126] (Example 7) FeSO4 surface treatment Add 20g of stearic acid and 50g of DI water to 20g of FeSO4·7H2O, and stir for 30 minutes while adding 50mL of ethanol. Then, add 20g of the conductive particles produced in step I to the solution, seal it in an autoclave, heat at 120°C for 1 hour, and after cooling to room temperature, wash the surface-treated conductive particles with DI water and then dry in a convention oven for 12 hours.

[0127] (Example 8) Cu(NO3)2 surface treatment Add 20g of Cu(NO3)2·3H2O, 20g of stearic acid, and 50g of DI water to the mixture and stir for 30 minutes while adding 50mL of ethanol. Then, add 20g of the conductive particles produced in step I to the solution, seal it in an autoclave, heat it at 120°C for 1 hour, and after it cools to room temperature, wash the surface-treated conductive particles with DI water and then dry them in a convention oven for 12 hours.

[0128] (Example 9) ZnSO4 surface treatment Add 20g of ZnSO47H2O, 20g of stearic acid, and 50g of DI water, and stir for 30 minutes while adding 50mL of ethanol. Then, add 20g of the conductive particles produced in step I to the solution, seal it in an autoclave, heat at 120°C for 1 hour, and after cooling to room temperature, wash the surface-treated conductive particles with DI water and then dry in a convention oven for 12 hours.

[0129] (Example 10) Ag2O surface treatment Add 20g of stearic acid and 50g of DI water to 20g of Ag2O, and stir for 30 minutes while adding 50mL of ethanol. Then, add 20g of the conductive particles produced in step I to the solution, seal it in an autoclave, heat at 120°C for 1 hour, and after cooling to room temperature, wash the surface-treated conductive particles with DI water and then dry in a convention oven for 12 hours.

[0130] (Example 11) PtO2 surface treatment Add 20g of stearic acid and 50g of DI water to 220g of PtO2, and stir for 30 minutes while adding 50mL of ethanol. Then, add 20g of the conductive particles produced in step I to the solution, seal it in an autoclave, heat at 120°C for 30 minutes, and after cooling to room temperature, wash the surface-treated conductive particles with DI water and then dry in a convention oven for 12 hours.

[0131] (Example 12) PdO surface treatment Add 20g of stearic acid and 50g of DI water to 20g of PdO, and stir for 30 minutes while adding 50mL of ethanol. Then, add 20g of the conductive particles produced in step I to the solution, seal it in an autoclave, heat at 120°C for 30 minutes, and after cooling to room temperature, wash the surface-treated conductive particles with DI water and then dry in a convention oven for 12 hours.

[0132] (Example 13) NiSO4 surface treatment Add 20g of stearic acid and 50g of DI water to 420g of NiSO4, and stir for 30 minutes while adding 50mL of ethanol. Then, add 20g of the conductive particles produced in step I to the solution, seal it in an autoclave, heat at 120°C for 1 hour, and after cooling to room temperature, wash the surface-treated conductive particles with DI water and then dry in a convention oven for 12 hours.

[0133] (Example 14) FeO surface treatment Add 20g of stearic acid and 50g of DI water to 20g of FeO, and stir for 30 minutes while adding 50mL of ethanol. Then, add 20g of the conductive particles produced in step I to the solution, seal it in an autoclave, heat at 120°C for 1 hour, and after cooling to room temperature, wash the surface-treated conductive particles with DI water and then dry in a convention oven for 12 hours.

[0134] (Example 15) Pd(NO3)2 surface treatment Add 20g of stearic acid and 50g of DI water to 220g of Pd(NO3) and stir for 30 minutes while adding 50mL of ethanol. Then, add 20g of the conductive particles produced in step I to the solution, seal it in an autoclave, heat at 120°C for 30 minutes, and after cooling to room temperature, wash the surface-treated conductive particles with DI water and then dry in a convention oven for 12 hours.

[0135] (Example 16) AgNO3 surface treatment Add 20g of stearic acid and 50g of DI water to 320g of AgNO, and stir for 30 minutes while adding 50mL of ethanol. Then, add 20g of the conductive particles produced in step I to the solution, seal it in an autoclave, heat at 120°C for 6 hours, and after cooling to room temperature, wash the surface-treated conductive particles with DI water and then dry in a convention oven for 12 hours.

[0136] (Example 17) Zn(NO3)2 surface treatment Add 20g of stearic acid and 50g of DI water to 220g of Zn(NO3) and stir for 30 minutes while adding 50mL of ethanol. Then, add 20g of the conductive particles produced in step I to the solution, seal it in an autoclave, heat at 120°C for 6 hours, and after cooling to room temperature, wash the surface-treated conductive particles with DI water and then dry in a convention oven for 12 hours.

[0137] (Example 18) Fe(NO3)3 surface treatment Add 20g of stearic acid and 50g of DI water to 320g of Fe(NO3) and stir for 30 minutes while adding 50mL of ethanol. Then, add 20g of the conductive particles produced in step I to the solution, seal it in an autoclave, heat at 120°C for 6 hours, and after cooling to room temperature, wash the surface-treated conductive particles with DI water and then dry in a convention oven for 12 hours.

[0138] (Example 19) Fe2(SO4)3 surface treatment Add 20g of stearic acid and 50g of DI water to 320g of Fe2(SO4) and stir for 30 minutes while adding 50mL of ethanol. Then, add 20g of the conductive particles produced in step I to the solution, seal it in an autoclave, heat at 120°C for 6 hours, and after cooling to room temperature, wash the surface-treated conductive particles with DI water and then dry in a convention oven for 12 hours.

[0139] (Comparative Example 1) No surface treatment was performed on the metal oxide layer. Conductive particles produced in the above process I were used, without surface treatment with a separate metal oxide layer.

[0140] (Comparative Example 2) Ni(NO3)2 surface treatment Add 20g of stearic acid and 50g of DI water to 20g of Ni(NO3)2·6H2O, and stir for 30 minutes while adding 50mL of ethanol. Then, add 20g of the conductive particles produced in step I to the solution, seal it in an autoclave, heat at 120°C for 24 hours, and after cooling to room temperature, wash the surface-treated conductive particles with DI water and then dry in a convention oven for 12 hours.

[0141] II. Measurement of Powder Resistance For the conductive particles of Examples 1-19 and Comparative Examples 1 and 2, the powder resistance was measured from 200 kgf to 2000 kgf using a powder resistance instrument, and the value at 1400 kgf is shown. Furthermore, the rate of increase in powder resistance after the formation of the metal oxide layer is shown in Table 1, comparing the results of measuring the conductive particle powder resistance of Comparative Example 2 and Examples 1-19 using the same method, with the conductive particle powder resistance of Comparative Example 1 as the reference.

[0142] III. 85 / 85 Reliability Evaluation The conductive particles of Examples 1 to 19 and Comparative Examples 1 and 2 were left for 72 hours under conditions of 85°C and 85%RH (85 / 85) humidity, and then their powder resistance values ​​were measured. [Table 1]

[0143] In Table 1, comparing the results of Comparative Example 1 and the Example, it can be confirmed that in the Example, the resistance increase of the conductive particles containing the metal oxide layer after the 85 / 85 reliability evaluation was small. This is judged to be a result of the metal oxide layer effectively protecting the surface of the conductive layer, thereby improving the electrical stability of the conductive layer.

[0144] Furthermore, comparing the results of Comparative Example 2 with those of the Example, it can be confirmed that when the thickness of the metal oxide layer is within 100 nm, as in the Example, the powder resistance is low and the rate of increase in powder resistance after the formation of the metal oxide layer is also low. This is judged to be a result that occurs when a metal oxide layer within the appropriate range is formed, the path through which the current passes becomes shorter, and interference due to the resistance characteristics of the oxide layer is relatively small.

[0145] On the other hand, if the metal oxide layer is excessively thick, the path through which the current must pass becomes longer, and the resistance characteristics of the metal oxide layer obstruct the flow of current, resulting in high powder resistance.

[0146] The present invention is not limited to the embodiments described above, and can be manufactured in a variety of different forms.

[0147] The above description is merely illustrative, and any person with ordinary skill in the art to which the present invention belongs can make various modifications without departing from the essential features of the present invention.

[0148] Therefore, the examples disclosed herein are for illustrative purposes only, not to limit the invention, and these examples do not limit the spirit or scope of the invention. The scope of protection of the invention must be interpreted in accordance with the claims, and all art of equivalent scope must be interpreted as being included within the scope of the invention.

Claims

1. The core and A conductive layer formed on the core, A conductive particle comprising a metal oxide layer formed on the aforementioned conductive layer.

2. The conductive particles according to claim 1, wherein the metal of the metal oxide layer includes Ni; Mn; Fe; Cu; Zn; Ag; Pd; Pt; or Au or a combination thereof.

3. The metal oxide layer is NiO; Ni ２ O ３ ; MnO; Mn ２ O ３ ; MnO ２ ; Mn ２ O ７ ; FeO; Fe ２ O ３ ; Fe ３ O ４ ; Cu ２ O; CuO; ZnO; Ag ２ O; PdO; PtO ２ ; Au ２ O ３ ; Ni(NO ３ ) ２ ; NiSO ４ ; Mn(NO ３ ) ２ ; MnSO ４ ; Fe(NO ３ ) ３ ; FeSO ４ ; Fe ２ (SO ４ ) ３ ; Cu(NO ３ ) ２ ; CuSO ４ ; Zn(NO ３ ) ２ ; ZnSO ４ ; AgNO ３ ; Pd(NO ３ ) ２ ; PdSO ４ or Pt(SO ４ ) ２ or a combination thereof, the conductive particles according to claim 1.

4. The conductive particle according to claim 1, wherein the thickness of the metal oxide layer is 0.1 nm to 100 nm.

5. The conductive particle according to claim 1, wherein the rate of increase in powder resistance after the formation of the metal oxide layer is 300% or less.

6. The conductive particles according to claim 1, wherein the core comprises resin fine particles or organic / inorganic hybrid particles.

7. The conductive particle according to claim 1, wherein the conductive layer contains Ni and at least one selected from the group consisting of P; B; Cu; Au; Ag; W; Mo; Pd; Co and Pt.

8. An anisotropic conductive material comprising conductive particles as described in claim 1.

9. A connecting structure comprising the anisotropic conductive material according to claim 8.

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