KR100593848B1 - Insulating conductive fine particles and anisotropic conductive film using same - Google Patents

Abstract

The insulating conductive fine particles of the present invention are composed of conductive fine particles coated with a metal layer on the surface of the substrate fine particle and hard insulating fine particles fixed on the surface of the conductive fine particles, and the insulating fine particles are recessed into the conductive fine particles by pressing. It is characterized in that it can be electrically connected between the electrodes. The anisotropic conductive film according to the present invention is characterized by using the above insulating conductive fine particles.

Insulating fine particles, insulating conductive particles, anisotropic conductive film, electrical connection method

Description

Insulated Conductive Particle and an Anisotropic Conductive Film Using the Same             

1 is an electrical connection cross-sectional view of an anisotropic conductive film using conventional insulating conductive fine particles.

2 is a schematic cross-sectional view and a front view of the insulating conductive fine particles of the present invention.

3 is a schematic cross-sectional view of the anisotropic conductive film using the insulating conductive fine particles of the present invention.

It is sectional drawing of the electrical connection of the anisotropic conductive film using the insulating conductive fine particle of this invention.

Brief description of the main symbols in the drawings

1: coating insulating fine particle 2: circuit board

3: insulating conductive fine particles 4: anisotropic conductive film

5: liquid crystal display substrate 11: conductive particles

12: coated insulation layer 21: bump electrode

31: substrate fine particle layer 32: metal layer

32a: nickel (Ni) layer 32b: gold (Au) layer

33: conductive fine particles 34: insulating fine particles

41: insulating adhesive 51: wiring pattern

Field of invention

The present invention relates to an insulating conductive fine particles and an anisotropic conductive film using the same. More specifically, the present invention relates to insulating conductive particles in which hard insulating fine particles are discontinuously immobilized on the surface of the conductive particles and an anisotropic conductive film using the same.

Background of the Invention

Anisotropic conductive film (ACF) is an adhesive on a film in which conductive particles such as metal-coated resin fine particles or metal particles are dispersed in insulating resin such as epoxy, urethane, and acryl, and an LCD substrate and TCP in liquid crystal display (LCD) mounting fields. It is widely used for electrical connection such as tape carrier package or printed circuit board and TCP. Such an anisotropic conductive film is conductive in the thickness direction (z-axis direction) of the film to connect the upper and lower electrodes with conductive particles, and has insulation in the plane direction (xy plane direction).

Recently, with the development of LCD technology, anisotropic conductive films are required to improve connection reliability, to minimize connection pitch, and to reduce IC bumps, and the number of leads printed on a substrate is increasing. In accordance with such technical requirements, it is necessary to reduce the particle size of the conductive particles contained in the anisotropic conductive film, and research and development to increase the compounding amount of the conductive particles in order to improve the connection reliability has been continued. However, due to the reduced particle size and the increased particle density of the particles used, agglomeration or bridges of the particles occur, which results in frequent nonuniformity of the connection and short circuits between patterns.

In order to solve the above problems, Japanese Patent Laid-Open Nos. 62-40183, 62-76215, and 62-176139 cover the surface of conductive particles with an insulating layer to insulate them in a state of being dispersed in an insulating adhesive resin component. However, the present invention discloses an anisotropic conductive film using conductive particles in which the insulating layer is destroyed and the conductive surface is exposed and energized when the electrodes are in close contact with each other by heat compression.

In Japanese Patent Laid-Open Nos. 3-46774 and 4-174980, the surface of the conductive particles is coated with a thermoplastic resin, and the insulating thermoplastic resin is dissolved at the electrode contact portion by interposing between the electrodes to pressurize and heat the conductivity of the inner layer. An anisotropic conductive film is disclosed in which parts are exposed to achieve electrical connection.

However, in the anisotropic conductive film using the coated fine particles, the insulating layer covering the conductive particles is not sufficiently destroyed or removed by heating and pressurization, but only a thin film or broken in place may cause the insulation to remain and interfere with the electrical connection. Have

On the other hand, in recent years, a low temperature fast curing type anisotropic conductive film and an adhesive process have been adopted in order to shorten the process time and reduce the cost while not burdening the electrode and the module. In this case, pressurization for a short time at a low temperature makes it more difficult to sufficiently break or remove the coated insulating layer, resulting in a problem of lowering connection reliability.

In order to solve the above problems, the present inventors fix the insulating fine particles that can be recessed into the conductive fine particles due to the pressure on the surface of the conductive fine particles, thereby containing the conductive conductive fine particles for increasing the conduction and insulation reliability of the conductive film and containing them It is early to develop an anisotropic conductive film.

An object of the present invention is to provide insulating conductive fine particles with high electric current reliability in the z-axis direction.

Another object of the present invention is to provide insulating conductive fine particles having high insulation reliability in the xy plane direction.

Still another object of the present invention is to provide insulating conductive fine particles in which aggregation of the conductive particles is prevented even when the particle size of the conductive particles is decreased and the density is increased.                         

Still another object of the present invention is to provide an anisotropic conductive film of a low temperature rapid curing type and insulating conductive fine particles suitable for the bonding process.

Still another object of the present invention is to provide an anisotropic conductive film containing insulating conductive fine particles.

Another object of the present invention is to provide an electrical connection structure using an anisotropic conductive film containing insulating conductive fine particles.

The above and other objects of the present invention can be achieved by the present invention described below.

Summary of the Invention

The insulating conductive fine particles of the present invention are composed of conductive fine particles coated with a metal layer on the surface of the substrate fine particle and hard insulating fine particles fixed on the surface of the conductive fine particles, and the insulating fine particles are recessed into the conductive fine particles by pressing. It is characterized in that it can be electrically connected between the electrodes.

The diameter of the insulating fine particles is 1/10 to 1 of the thickness of the metal layer. It is preferable.

It is preferable that the said insulating fine particle is discontinuously fixed by the density of 1-800 piece / micrometer <^2> on the surface of electroconductive fine particle.

The insulating fine particles are selected from the group consisting of crosslinked organic polymers, organic / inorganic composite particles, and inorganic fine particles, and are preferably insoluble in adhesives and solvent components.

The insulating fine particles are preferably immobilized on the surface of the conductive fine particles by physical / mechanical methods.

Preferably, the metal layer is formed of at least one.

The anisotropic conductive film according to the present invention is characterized by using the above insulating conductive fine particles.

Hereinafter, the detailed description of the insulating conductive fine particles of the present invention and the anisotropic conductive film using the same.

Detailed Description of the Invention

1 is an electrical connection cross-sectional view of an anisotropic conductive film using conventional insulating conductive fine particles. The coated insulating fine particles 1 cover the outermost layer of the conductive particles 11 with the insulating layer 12 and are designed to exhibit anisotropic conductivity by heating and pressing. However, as shown in FIG. 1, the insulation layer 12 is not sufficiently destroyed or removed by heating and pressurization, but only a thin film or an insulation remains.

2 shows a cross section and a surface of the insulating conductive fine particles 3 of the present invention. The insulating conductive fine particles 3 of the present invention consist of the conductive fine particles 33 and the insulating fine particles 34 discontinuously fixed to the surface thereof.

In the conductive fine particles 33 according to the present invention, the surface of the monodisperse substrate fine particles 31 made of inorganic particles or organic polymer resin is covered with the metal layer 32.

Examples of the organic polymer resin include epoxy resin, phenoxy resin, polyisocyanate resin, phenol resin, melamine resin, acrylic resin, acrylate resin, silicone resin, polyimide, polyamide, polyethylene, polypropylene, polystyrene, polydi Vinylbenzene, acrylonitrile-styrene resin, acrylonitrile-butadiene-styrene resin, polycarbonate, polysulfone, polyurethane, polyester, fluorine resin, melamine resin, benzoguanamine resin, and the like. It is preferable to use or mix 2 or more types. Moreover, the organic polymer resin can also use the hardened | cured material of resin in which the crosslinked structure was made by reacting with a crosslinking agent and a hardening | curing agent, or reactive resin.

As the inorganic particles, silica, glass and alumina may be used.

The substrate fine particles according to the present invention have an average particle diameter of 1 to 20 µm, preferably 2 to 10 µm.

As the metal layer 32 according to the present invention, a conductive metal such as gold, silver, nickel, copper, or the like may be used.

The conductive metal layer may be formed by a physical method such as a deposition method, an ion sputtering method, a plating method, a thermal spraying method, or a general method such as chemical bonding or precipitation.

In one specific example of the present invention, a metal layer of nickel 32a / gold 32b is sequentially electroless plated on the surface of the substrate fine particles, and the outer portion of the conductive metal layer is a gold (Au) layer.

It is preferable that it is 0.01-5 micrometers, and, as for the thickness of the said metal layer, it is more preferable to set it as 0.05-1 micrometer. This is the range which can make it deform | transform along with deformation | transformation of the substrate particle by compression, although the said metal layer has favorable electroconductivity.

The insulating fine particle 34 according to the present invention uses hard fine particles, and induces the depression into the conductive metal layer. Hard as referred to in the present invention means that the spherical shape is not deformed by external force, heat, impact and frictional force, and does not dissolve in insulating resin adhesives and other solvents at the time of physical / mechanical complexation.

As the hard insulating fine particles used in the present invention, it is preferable to use crosslinked polymer fine particles, organic / inorganic composite particles, inorganic fine particles and the like.

The crosslinked polymer microparticles are basically composed of a crosslinkable polymerizable monomer alone or a copolymer of a crosslinkable monomer and one or more general polymerizable monomers, and may be prepared by emulsion polymerization, nonemulsification polymerization, dispersion polymerization or precipitation polymerization. have.

The crosslinkable polymerizable monomer may be radically polymerized, and may be divinylbenzene, 1,4-divinyloxybutane, divinyl sulfone, diallyl phthalate, diallyl acrylamide, triallyl (iso) cyanurate, triallyl. Allyl compounds, such as trimellitate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, pentaerythritol tetra (meth) acrylate, pentaerythryl Tall tri (meth) acrylate, pentaaryl tritol di (dec) acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta Acrylic compounds, such as (meth) acrylate and glycerol tri (meth) acrylate, are included.

The organic / inorganic composite particles are prepared by adding and reacting an inorganic component such as a silane group-containing monomer, a layered silicate compound, silica, titania, alumina, and the like in a step of polymerizing a monomer capable of radical reaction to produce particles. It is desirable to.

As the inorganic fine particles, monodisperse silica fine particles may be used, and may be easily prepared by a general sol-gel method.

The insulating fine particles 34 according to the present invention are discontinuously and uniformly compounded on the surface of the outermost layer of the conductive fine particles 33.

As a method of fixing the insulating fine particles to the outermost layer of the conductive fine particles 33, spray drying, in situ polymerization method, vacuum deposition coating method, dry blend method, electrostatic coalescence method, dispersion cooling method The interfacial precipitation method is preferable, and it is more preferable to use a hybridization system of Nara Machinery Corporation.

The insulating fine particles according to the present invention may be fixed at 1 to 99% of the surface area of the conductive fine particles 33, and in order to impart electrical insulation, the insulating fine particles may be fixed to 20 to 95% of the surface area of the conductive particles.

The diameter of the insulating fine particles 34 is preferably 1/10 to 1 of the total thickness of the metal layer. In addition, in order to insulate the surface of the insulating conductive fine particles 3, it is preferable that the insulating fine particles 34 are uniformly and discontinuously complexed at a density of ¹ to 800 particles / μm ² with respect to the surface area of the conductive fine particles 33. Do.

However, the number of insulating microparticles 34 that can be immobilized per unit area varies according to the diameter thereof. For example, in the case where the diameter of the insulating fine particles is 100 nm, when the insulating fine particles are fixed at 27 particles / μm ² , 90% of the surface of the conductive fine particles is obtained. After fixing in 21 / ㎛ ² when 70% of the conductive particle surfaces, fixed in 11 / ㎛ ² and to cover the 35% of the conductive particle surfaces it can be fixed with about 30 up / ㎛ ^2.

3 shows a cross-sectional structure of the anisotropic conductive film 4 using the insulating conductive fine particles 3 of the present invention. The anisotropic conductive film 4 is obtained by dispersing the insulating conductive fine particles 3 in the insulating adhesive 41. It is preferable that the anisotropic conductive film which concerns on this invention contains the said insulating conductive fine particle 3 in the density of 5,000-8,000 piece / mm <2>. Moreover, 1-30 weight% is preferable and, as for the compounding quantity of the insulating conductive particle with respect to an insulating adhesive agent, 3-20 weight% is more preferable.

Fig. 4 shows the electrical connection structure of the anisotropic conductive film 4 and its mechanism using the insulating conductive fine particles 3 of the present invention. Referring to FIG. 4A, an anisotropic conductive adhesive film according to the present invention is provided between a circuit board 2 on which bump electrodes 21 are formed and a liquid crystal display board 5 on which wiring patterns 51 are formed. (4) is located.

As shown in (b) and (c) of FIG. 4, when the anisotropic conductive film according to the present invention is bonded between the electrodes, the insulating fine particles 34 on the surface of the insulating conductive fine particles 3 are pressed to form a metal layer. The electrodes are energized by breaking and sinking therein to expose the outermost metal layer. In addition, the insulating fine particles 34 on the surface of the insulating conductive fine particles 3 may destroy the metal layer by the heating and pressing, and may be recessed therein. The heating and pressurization can be easily carried out by those skilled in the art.

When the anisotropic conductive film 4 of the present invention is connected to electricity to pressurize or heat / press, the insulating fine particles 34 are pressed and spread widely, or are not broken and removed from the surface of the conductive fine particles 33 so that the electrical connection is made. In order to prevent being inhibited, in the present invention, hard insulating fine particles are used to induce depression into the conductive metal layer.

The invention can be better understood by the following examples, which are intended for the purpose of illustration of the invention and are not intended to limit the scope of protection defined by the appended claims.

Example

Example 1

Preparation of Insulating Fine Particles

Ultrapure water (700 parts by weight) containing methyl methacrylate (MMA, 80 parts by weight) monomer and divinylbenzene (DVB, 20 parts by weight) containing potassium persulfate (KPS, 1 part) by water-soluble initiator It dispersed in, and superposed | polymerized at 75 degreeC by the non-emulsification polymerization method for 24 hours, and obtained 100 micrometer diameter particle | grains. The prepared poly (MMA-DVB) particles were dried in a vacuum oven for 24 hours after removing unreacted materials and other impurities using a centrifuge to obtain a powder form.

Preparation of Insulating Conductive Fine Particles

The insulating fine particles prepared above were immobilized on the surface of the conductive fine particles by using a hybridization system (Hybridizer 0 type) in a conductive fine particle having a diameter of 4 µm on the surface of the monodisperse acrylic resin fine particles. . The nickel / gold plated layer thickness was about 150 nm, and the immobilization density was measured to be about 21 pieces / μm ² as measured using a scanning electron micrograph.

Preparation of Anisotropic Conductive Film

NBR rubber (65 parts by weight), bisphenol A type epoxy resin (7000 equivalents, 25 parts by weight) and curing agent 2-methylimidazole (4 parts by weight) are dissolved in a mixed solvent of toluene and methyl ethyl ketone, The prepared three-layered insulating conductive fine particles were dispersed together with the silane coupling agent, and then coated on a release PET film and dried to prepare a 25 μm thick film. The number of the insulating conductive fine particles per unit area of the film thus produced was about 10,000 pieces / mm 2.

Examples 2-4

Examples 2 to 4 were prepared in the same manner as in Example 1 except that the density of the insulating fine particles was changed as described in Table 1.

Comparative Examples 1 and 2

Comparative Examples 1 and 2 were prepared in the same manner as in Example 1, except that the LDPE resin was completely coated on the surface of the conductive fine particles with the thickness of the insulating layer shown in Table 1.

Example Comparative Example One 2 3 4 One 2 Content of Insulating Conductive Fine Particles (pcs / mm2) 10.000 10,000 10,000 10,000 10,000 10,000 Insulation layer thickness (㎛) 0.1 0.1 0.1 0.1 0.1 0.2 Density of Insulating Fine Particles (piece / μm ² ) 21 11 27 21 - - Bump area of the IC used for conduction evaluation (㎛ ² ) 3,000 3,000 3,000 3,000 3,000 3,000

The conduction reliability and insulation reliability of the IC chip were evaluated for the anisotropic conductive adhesive film prepared as follows.

Reliability

The bump heights of the evaluation IC chips used were all about 40 mu m and the IC size was 6 mm x 6 mm.

The board | substrate formed the wiring pattern by Cu and Au plating of 8 micrometers thick on the board | substrate of 0.8-mm-thick BT resin, and the pitch between wiring patterns is 150 micrometers.

Heat press for 15 seconds under conditions of a temperature of 200 ° C. and a pressure of 400 kg / cm 2 -bump with the anisotropic conductive film interposed between the IC chip and the substrate (the sum of the bump height and the wiring pattern height is about 58 μm). And crimped | bonded and connected. After the connection sample was aged at 85 ° C., 85% RH for 1,000 hours, the current-carrying reliability was evaluated based on the resistance increase according to the following criteria. The results are shown in Table 2.

◎: resistance rise 0.1 Ω or less

△: resistance increase 0.1 Ω or more and 0.3 or less

×: resistance rise exceeding 0.3 Ω

Insulation reliability

The IC chip has a bump size of 70 μm × 100 μm, a space of 10 μm, a bump height of 20 μm, an IC size of 6 mm × 6 mm, the substrate has a pitch of 80 μm, a line of 70 μm, and the presence or absence of a short circuit occurs under a microscope. A transparent substrate having a wiring pattern formed of indium tin oxide (ITO) on glass was used.

The IC chip and the substrate were connected in the same manner as in the above conduction evaluation. After the connection sample was aged at 85 ° C., 85% RH for 1000 hours, adjacent two pins 25V and 1 minute were applied, and the insulation resistance was evaluated according to the following criteria, and the results are shown in Table 2.

10 ¹⁰ Ω or more: ◎

10 ¹⁰ Ω or less: ×

division Example Comparative Example One 2 3 4 One 2 Reliability ◎ ◎ △ ◎ ◎ △ Insulation reliability ◎ ◎ ◎ ◎ × ◎

As can be seen in the above Examples 1 to 4 and Comparative Examples 1 to 2, the anisotropic conductive adhesive film using the insulating conductive fine particles to which the insulating fine particles according to the present invention are immobilized can obtain higher conduction and insulation reliability. there was.

The present invention provides a high temperature fast curing type anisotropic conductive film and a bonding process when the insulating fine particles are discontinuously and uniformly immobilized on the surface of the conductive fine particles, so that the conduction reliability in the z-axis direction and the insulation reliability in the xy plane direction are high. The effect of the invention to provide an anisotropic conductive adhesive film and electrical connection structure suitable for the.

Simple modifications and variations of the present invention can be readily used by those skilled in the art, and all such variations or modifications can be considered to be included within the scope of the present invention.

Claims (8)

Conductive fine particles 33 having a metal layer 32 coated on the substrate fine particles 31; And It is made of hard insulating fine particles 34 fixed to the surface of the conductive fine particles 33, The insulating fine particles (34) can be electrically connected between the electrodes by being recessed into the inside of the conductive fine particles (33) by the pressurized. Insulating conductive fine particles according to claim 1, wherein the insulating fine particles (34) are recessed into the conductive fine particles (33) by heating and pressing. Insulating conductive fine particles according to claim 1, wherein the diameter of the insulating fine particles (34) is 1/10 to 1 of the thickness of the metal layer (32). The insulating conductive fine particles according to claim 1, wherein the insulating fine particles (34) are discontinuously fixed to the surface of the conductive fine particles at a density of ¹ to 800 particles / µm ² . The insulating conductive particles according to claim 1, wherein the insulating fine particles (34) are selected from the group consisting of crosslinked organic polymers, organic / inorganic composite particles, and inorganic fine particles, and are insoluble in adhesives and solvent components. Insulating conductive fine particles according to claim 1, wherein the insulating fine particles (34) are immobilized on the surface of the conductive fine particles (33) by physical / mechanical methods. Insulating conductive fine particles according to claim 1, wherein the metal layer (32) is formed of at least one. The anisotropic conductive film using the insulating conductive microparticles of any one of Claims 1-7.

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