WO2006085481A1

WO2006085481A1 - Electrically conductive fine particles, anisotropic electrically conductive material, and electrically conductive connection method

Info

Publication number: WO2006085481A1
Application number: PCT/JP2006/301836
Authority: WO
Inventors: Takashi Kubota
Original assignee: Sekisui Chemical Co., Ltd.
Priority date: 2005-02-09
Filing date: 2006-02-03
Publication date: 2006-08-17
Also published as: JPWO2006085481A1; JP4922916B2; TW200632134A; CN101111903A; KR20070100967A

Abstract

This invention provides electrically conductive fine particles, which, even when used particularly in plasma display panels, have low connection resistance and is large in current capacity at the time of connection, further can prevent migration upon heating, and can realize high connection reliability, and anisotropic electrically conductive materials using the electrically conductive fine particles and an electrically conductive connection method. The electrically conductive fine particles (2) comprise particles (2) and films formed by electroless plating on the surface of the particles, that is, a nickel plating film (3), a tin plating film (4), and a bismuth plating film (5) provided in that order, and a silver plating film (6) provided on the outermost surface. The anisotropic electrically conductive material comprises the above electrically conductive fine particles dispersed in a resin binder. The electrically conductive connection method comprises heating the above electrically conductive fine particles on the surface of an electrode to cause metal heat diffusion to form a silver-bismuth-tin alloy film and to allow a part of the softened alloy film to flow on the surface of the electrode, thereby increasing the contact area.

Description

Specification

Conductive fine particles, anisotropic conductive material, and conductive connection method

Technical field

[0001] The present invention relates to conductive fine particles, anisotropic conductive material, and conductive connection method.

The present invention relates to a conductive fine particle having a low connection resistance, a large current capacity at the time of connection and preventing migration by heating, an anisotropic conductive material using the conductive fine particle, and a conductive connection method.

Background art

[0002] Conductive fine particles are mixed with a binder resin or the like to form main constituent materials of anisotropic conductive materials such as anisotropic conductive films, anisotropic conductive pastes, anisotropic conductive adhesives, etc. Widely used. These anisotropic conductive materials are used to electrically connect substrates to each other and electronic components such as semiconductor elements in electronic devices such as liquid crystal displays, personal computers, and mobile phones. Therefore, it is used by being sandwiched between opposing substrates and electrode terminals.

[0003] As such conductive fine particles, those obtained by applying metal plating to the outer surface of organic base particles or inorganic base particles are widely used.

[0004] In recent years, electronic devices and electronic components have been miniaturized, and wiring on a substrate or the like has become finer, and it has become an urgent task to improve the reliability of the connection portion. Furthermore, recently developed devices for application to plasma display panels, etc., are of a large current drive type, and therefore there is a demand for conductive fine particles that can handle a large current. However, if the base particles are non-conductive particles such as resin particles, the conductive layer provided by electroless plating cannot usually be made too thick, so there is a problem that the current capacity at the time of connection is small. .

[0005] On the other hand, conductive fine particles using metal particles as base particles have been reported as electrode joining members used in plasma display panels that require handling of large currents (see, for example, Patent Document 1 and Patent Document 2). ).

[0006] Patent Document 1 discloses a method in which an adhesive sheet in which conductive particles of nickel particles or gold-plated nickel particles are dispersed is bonded by pressure bonding. Patent Document 2 Discloses a member using conductive fine particles formed by coating gold on a metal powder mainly composed of nickel or copper.

[0007] However, if the base particles are conductive fine particles of nickel particles, it is not sufficient for further handling of a large current and improvement of connection reliability. Further, when copper having a lower resistance value than Nikkenore was used for the base particles, there was a problem of copper oxidation and migration. That is, when the substitution gold plating normally used on the copper metal particle surface is performed, the gold plating film forms an alloy by diffusion, and in the case of the gold-copper alloy film formed by this, a pinhole is formed in the alloy film layer. The copper oxidation prevention and migration prevention were not sufficient. Also, gold is usually used on the outermost surface to reduce the connection resistance value and stabilize the surface. However, since gold is expensive, there is a problem that, for example, power silver that can be considered to use silver as the outermost surface is easy to migrate.

[0008] Further, in recent years, where the improvement of the reliability of the connecting portion has become an urgent task, the electrodes are connected by thermocompression bonding using, for example, an anisotropic conductive film (ACF) using conductive fine particles. In general, however, the contact area of the conductive fine particles to the electrode is small, and the connection reliability may not be sufficient. For this reason, in particular, in order to apply to a plasma display panel of a large current drive type, further improvement in connection reliability has been demanded. Patent Document 1: Japanese Patent Laid-Open No. 11 16502

Patent Document 2: Japanese Patent Laid-Open No. 2001-143626

Disclosure of the invention

[0009] In view of the above situation, the present invention has a high connection reliability, especially when used in a plasma display panel, which has a low connection resistance, a large current capacity at the time of connection, and further prevents migration by heating. An object is to provide conductive fine particles, an anisotropic conductive material using the conductive fine particles, and a conductive connection method.

[0010] In order to achieve the above object, according to the invention described in claim 1, it is provided with particles and a conductive coating formed on the particle surface by an electroless plating method, and the conductive coating is an electroless mesh. Conductive fine particles characterized by having a nickel plating film, a tin plating film, and a bismuth plating film that are formed in order from the inside with a silver coating, and further having a silver plating film on the outermost surface. Provided. [0011] The invention according to claim 2 provides an anisotropic conductive material in which the conductive fine particles according to claim 1 are dispersed in a resin binder.

[0012] Further, in the invention of claim 3, the conductive fine particles of claim 1 are heated on the electrode surface to cause metal thermal diffusion to form an alloy film of silver, bismuth, and tin. In addition, the present invention provides a conductive connection method in which a part of a soft alloy film is caused to flow on the electrode surface to expand the contact area.

Hereinafter, details of the present invention will be described.

The conductive fine particles of the present invention have a structure in which a conductive film is formed on the surface of particles as substrate particles. In this conductive film, a nickel plating film, a tin plating film, and a bismuth plating film are sequentially formed by an electroless plating method, and a silver plating film is formed on the outermost surface.

That is, for example, as shown in a schematic cross-sectional view in FIG. 1, the conductive fine particles 1 of the present invention are formed on the surface of the particles 2 as base particles by a nickel plating film 3 and tin by an electroless plating method. It has a structure in which a plating film 4 and a bismuth plating film 5 are sequentially formed. In the conductive film, a silver plating film 6 is formed on the outer side of the portion where the nickel plating film 3, tin plating film, and bismuth plating film 5 are laminated. Therefore, the outermost surface is a silver plating film 6.

[0015] It should be noted that when copper metal particles are used as base particles and each metal plating film is formed on the surface, the connection resistance is low and the current capacity at the time of connection is large, which is particularly favorable when used in a plasma display panel. It becomes conductive fine particles.

[0016] When the conductive fine particles of the present invention are heated, an alloy film of silver-bismuth-tin is formed by metal thermal diffusion between the tin plating film, the bismuth plating film, and the silver plating film. When the alloy film is formed, the conductive fine particles of the present invention can prevent migration.

[0017] Generally, in a plasma display panel, a high voltage of about 250V is applied between terminals, so if moisture and metal ions are present between the electrodes, the cause of the migration is caused by the combined high voltage. turn into. When the alloy film is formed, migration that prevents elution of metal ions is prevented. [0018] The heating is preferably performed at 120 ° C or higher. When the heating is less than 120 ° C., metal thermal diffusion hardly occurs between the tin plating film, the bismuth plating film, and the silver plating film. In addition, the upper limit of heating is preferably equal to or lower than the temperature at which the base particles do not melt. When copper metal particles are used, the temperature is preferably 1000 ° C or lower.

[0019] The heating method is not particularly limited. For example, when the anisotropic conductive material is produced using the conductive fine particles of the present invention and is thermocompression-bonded to the electrode with an anisotropic conductive film, for example, 120 is used. A method of heating to ° C or higher is preferred. Usually, when electrodes are connected using an anisotropic conductive film, thermocompression bonding is performed at 120 ° C or higher.

[0020] When the conductive fine particles of the present invention are heated in the range of 120 to 400 ° C, which is usually used when connecting electrodes using an anisotropic conductive film, for example, a tin plating film, A silver-bismuth-tin alloy coating is formed by metal thermal diffusion between the bismuth coating and the silver coating. When copper metal particles are used as the base particles, the nickel plating film is provided to prevent tin from being thermally diffused into copper, which is the base particles.

[0021] In the present invention, confirmation that an alloy film of silver bismuth tin is formed is, for example, by X-ray diffraction analysis, energy dispersive X-ray spectroscopy (hereinafter also simply referred to as "EDX"), etc. It can be carried out.

Further, the method for examining the content ratio of the composition of the alloy coating can be carried out by, for example, fluorescent X-ray diffraction analysis, EDX or the like.

[0022] The anisotropic conductive material of the present invention is obtained by dispersing the conductive fine particles of the present invention in a resin binder.

[0023] The anisotropic conductive material is not particularly limited as long as the conductive fine particles of the present invention are dispersed in a resin binder. For example, anisotropic conductive paste, anisotropic conductive ink, and different Examples thereof include an anisotropic conductive adhesive, an anisotropic conductive film, and an anisotropic conductive sheet.

[0024] Examples of the connection object in which the anisotropic conductive material is used include parts such as a substrate and a semiconductor. Electrode portions are respectively formed on these surfaces. As the anisotropic conductive material of the present invention, for example, when electrodes are connected using an anisotropic conductive film, thermocompression bonding is performed at 120 ° C. or higher as described above. [0025] In the conductive connection method of the present invention, the conductive fine particles of the present invention are heated on the surface of the electrode to cause metal thermal diffusion to form an alloy film of silver bismuth tin and to form a softened alloy film. A part is made to flow on the electrode surface to enlarge the contact area.

[0026] In the conductive connection method of the present invention, the conductive fine particles of the present invention cause metal thermal diffusion by heating on the electrode surface to form an alloy film of silver, bismuth, and tin. Even when used in display panels, migration can be prevented and good conductive connections can be obtained.

[0027] In addition, since the conductive coating method of the present invention forms an alloy film of silver, bismuth, and tin by heating, the alloy film can be softened, and a part of the softened alloy film is formed. Can flow to the electrode surface to increase the contact area. In this way, by increasing the contact area on the electrode, the conductive fine particles are excellent in connection reliability even when used particularly in a plasma display panel.

[0028] In the conductive connection method of the present invention, the method for heating the conductive fine particles on the electrode surface is not particularly limited. For example, the conductive fine particles are heated when thermocompression-bonded to the electrode using an anisotropic conductive film. Is preferably used.

[0029] The heating is preferably performed at 120 ° C or higher as described in the conductive fine particles of the present invention. When the heating is less than 120 ° C., metal thermal diffusion hardly occurs between the tin plating film, the bismuth plating film, and the silver plating film. The upper limit of heating is preferably 1000 ° C. or less at which the copper metal particles as the base particles do not melt.

[0030] In the conductive connection method of the present invention, metal thermal diffusion is caused in the conductive fine particles by heating to form an alloy film of silver bismuth tin. As described above, the conductive fine particles are usually used when the electrodes are connected using an anisotropic conductive film, for example, 120 to 400. When heated in the range of C, a silver-bismuth-tin alloy film is formed by metal thermal diffusion between the tin plating film, the bismuth plating film, and the silver plating film.

[0031] Hereinafter, the present invention will be described in more detail.

Examples of the substrate particles in the present invention include resin particles, inorganic particles, organic-inorganic hybrid particles, and metal particles. Examples of the resin constituting the resin particles include divinylbenzene resin, styrene resin, acrylic resin, urea resin, and imide resin. The Further, examples of the inorganic substance constituting the inorganic particles include silica and carbon black. Examples of the organic-inorganic hybrid particles include organic-inorganic hybrids composed of a crosslinked alkoxysilyl polymer and an acrylic resin. In addition, examples of the metal particles include copper metal and copper alloy. Especially, it is preferable that a base particle is a copper metal.

[0032] The copper purity of the copper metal particles in the present invention is not particularly limited, but is preferably 95% by weight or more, more preferably 99% by weight or more. If the purity of the copper is less than 95% by weight, for example, when used in a plasma display panel, it may be difficult to ensure connection reliability when a large current flows.

[0033] The shape of the particles is not particularly limited, and may be, for example, particles having a specific shape such as a spherical shape, a fibrous shape, a hollow shape, or a needle shape, or may be an irregularly shaped particle. In particular, to obtain a good electrical connection, the particles are preferred to be spherical.

[0034] The average particle size of the particles is not particularly limited, but is preferably 1-100 μm, more preferably 2-20 μΐη.

[0035] The CV value of the particles is not particularly limited, but is preferably 10% or less.

7% or less is more preferable. The CV value is a percentage obtained by dividing the standard deviation in the particle size distribution by the average particle size.

[0036] Examples of commercially available copper metal particles that can satisfy the above average particle diameter and CV value include spherical copper powder "SCP-10" manufactured by S'Science, and spherical copper powder "MA-" manufactured by Mitsui Kinzoku Co., Ltd. CD— S

Or the like.

[0037] When the substrate particles are copper metal particles, it is preferable to purify the surface of the copper metal particles until the active surface of the metal copper comes out when performing electroless plating on the surface of the particles. The method for purifying the surface of the copper metal particles is not particularly limited, and examples thereof include a wet method using persulfate and the like, a dry method using plasma, etc. Among them, the treatment method is simple. Therefore, the wet method is preferably used.

[0038] The thickness of the nickel plating film in the present invention is not particularly limited, but is preferably from 5 to 5% of the average particle diameter of the particles.

[0039] The film thickness of the tin plating film is not particularly limited, but the average particle diameter of the particles :! ~ 5% is preferred.

[0040] The thickness of the bismuth plating film is not particularly limited, but is preferably 1 to 3.5% of the average particle diameter of the particles.

[0041] Further, the film thickness of the silver plating film is not particularly limited, but it is preferably 0.01 to 0.05 ^ο / _ο of the average particle diameter of the particles.

[0042] In the present invention, the method for forming the coating film by the electroless plating method is not particularly limited. For example, a reduction plating such as a reduction nickel plating, a reduction tin plating, a reduction bismuth plating, a reduction silver plating, A method formed by substitution tin plating or the like is preferably used.

[0043] The method formed by the above reduction plating may be a method using an autocatalytic reduction method, a method using a base catalyst type reduction method, or a method using a self catalyst type reduction method and a method using a base catalyst type. You may use together the method by a reduction method.

[0044] The above-described method based on the base catalyst type reduction plating causes a reduction agent that causes an oxidation reaction on the surface of the base metal and does not cause an oxidation reaction on the surface of the deposited metal. In this method, a metal film is formed by reducing and precipitating a metal salt.

[0045] When the nickel plating film is formed, the nickel salt is not particularly limited, and examples thereof include nickel sulfate, nickel chloride, nickel nitrate and the like.

[0046] Further, when the tin plating film is formed, the tin salt is not particularly limited, and examples thereof include tin chloride and tin nitrate.

[0047] When the bismuth plating film is formed, the bismuth salt is not particularly limited, and examples thereof include bismuth nitrate.

[0048] When the silver plating film is formed, the silver salt is not particularly limited, and examples thereof include silver nitrate, silver chloride, and silver cyanide.

[0049] Next, a specific method of autocatalytic reduced nickel plating will be described.

The above-described method using a self-catalyst type reduced nickel plating is a method in which palladium metal is first deposited as a catalyst, and then a nickel plating film is deposited by the autocatalyst.

[0050] Examples of self-catalyzed reduced nickel plating baths include nickel salt-based plating baths, complexing agents such as carboxylic acids such as citrate and tartaric acid, and aminocarbo- yls such as glycine. Acids, Phosphorus-based reducing agents such as sodium hypophosphite as reducing agents, Boron-based reducing agents such as dimethylaminoborane, Boric acid etc. as pH buffering agents, monostrength rubonic acids such as acetic acid and propionic acid, And a plating bath to which a pH adjusting agent is added.

[0051] The concentration of the nickel salt in the plating bath is preferably 0.01 to 0.1 ImolZl.

[0052] The concentration of citrate as a complexing agent in the above bath is preferably from 0.08 to 0.8 molZl.

[0053] The concentration of hypophosphorous acid as the reducing agent in the plating bath is preferably 0.03 to 0.7 molZl.

[0054] The concentration of the pH buffer that suppresses pH fluctuation in the above-mentioned bath is preferably from 0.01 to 0.3 mol / l.

[0055] Further, examples of the pH adjuster for adjusting the pH in the above-mentioned bath include ammonia, sodium hydroxide and the like when adjusting to the strength side, and among others, ammonia. In the case of adjusting to the more preferable acidic side, sulfuric acid, hydrochloric acid and the like can be mentioned. Of these, sulfuric acid is preferable.

[0056] The pH of the plating bath is preferably 8 to 10 in order to increase the reaction driving force.

[0057] Further, the bath temperature of the above-mentioned bath is preferably higher in order to increase the reaction driving force, but if it is too high, bath decomposition may occur, so 50-70 ° C is preferable.

[0058] In addition, since the above-mentioned Metsu bath tends to cause aggregation due to the reaction if the particles are not uniformly dispersed in the aqueous solution, at least an ultrasonic wave and a stirrer are used so that the particles are uniformly dispersed and aggregation is not caused. It is preferable to use any dispersing means.

[0059] Next, specific methods for substituted tin plating and autocatalytic reduced tin plating will be described.

[0060] The above-described method using substituted tin plating is a method in which nickel as a base is dissolved, the tin salt receives the dissolved nickel salt electrons, and a tin plating film is deposited.

[0061] The substituted tin plating bath includes, for example, a plating bath obtained by adding a carboxylic acid such as tartaric acid and a sulfur compound such as thiourea as a complexing agent to a plating bath based on a tin salt. Can be mentioned.

[0062] The concentration of the tin salt in the plating bath is preferably 0.01 to 0.1 mol / l. [0063] The concentration of tartaric acid is preferably from 0.08 to 0.8 mol / l as the complexing agent in the above-mentioned Metz bath. The concentration of thiourea is preferably from 0.08 to 0.8 mol / l.

[0064] Further, the pH adjustment, bath temperature adjustment, and dispersion means of the plating bath are preferably performed in the same manner as in the case of the above-described reduced nickel plating bath.

[0065] The above-described method using a self-catalyzed reduced tin plating is a method of forming a tin plating coating by a disproportionation reaction as a self-catalytic reducing tin plating after a substituted tin plating coating is formed. .

[0066] Examples of the reduced tin plating bath as a disproportionation reaction include a plating bath based on a tin salt, carboxylic acids such as citrate and tartaric acid as complexing agents, sodium hydroxide and hydroxide as reducing agents. Examples thereof include potassium baths and a plating bath to which sodium hydrogen phosphate, ammonium hydrogen phosphate and the like are added as a buffering agent.

[0067] The concentration of the tin salt in the plating bath is preferably 0.01 to 0.1 mol / l.

[0068] The concentration of citrate as a complexing agent in the above bath is preferably 0.08-0.8 mol / l.

[0069] The concentration of sodium hydroxide as the reducing agent in the plating bath is preferably 0.3 to 2.4 mol / l.

[0070] The concentration of sodium hydrogen phosphate, which is a buffer that stabilizes tin precipitation, in the above bath is 0

.:! To 0.3 mol / l is preferred.

[0071] The pH adjustment, bath temperature adjustment, and dispersion means of the above-mentioned plating bath are preferably performed in the same manner as in the above-described reduced nickel plating bath.

[0072] Next, a specific method of autocatalytic reduced bismuth plating will be described.

The self-catalytic reduced bismuth plating method described above is a method in which palladium metal is first attached to the underlying tin plating film as a catalyst, and then the bismuth plating film is deposited by the autocatalysis.

[0073] Examples of the self-catalyzed reduced bismuth plating bath include, for example, a plating bath based on a bismuth salt, a carboxylic acid such as sodium citrate as a complexing agent, and titanium chloride as a reducing agent.

(Ii), salty titanium (IV), etc., darioxynolic acid as a crystal modifier, phosphate salt as a buffer, and a bath with a pH adjuster added. [0074] The concentration of the bismuth salt in the plating bath is preferably 0.01 to 0.03 mol / l.

[0075] The concentration of sodium citrate as a complexing agent in the above-mentioned bath is preferably 0.04 to 0.1 mol / l.

[0076] The concentration of titanium salt as a reducing agent in the above bath is preferably 0.12-0.8 mol / l.

[0077] The concentration of darioxylic acid as a crystal adjusting agent in the above-mentioned bath is preferably 0.001 to 0.005 molZl.

[0078] The concentration of hydrogen phosphate as a buffering agent in the above bath is preferably 0.04-0.12 molZl.

[0079] The pH adjusting agent for adjusting pH in the above-mentioned bath is, for example, ammonia when adjusting to the alkalinity side, sulfuric acid when adjusting to the acidic side, Examples include hydrochloric acid, and sulfuric acid is preferable.

[0080] The pH of the plating bath is preferably 8 to 10 in order to increase the reaction driving force.

[0081] Further, the bath temperature of the above-mentioned bath is preferably 10-30 ° C.

[0082] Further, it is preferable to carry out the dispersing means of the plating bath in the same manner as in the case of the above-described reduced nickel plating bath.

[0083] Next, a specific method of autocatalytic reduced silver plating will be described.

As a self-catalyzed reduced silver plating bath, for example, a plating bath based on a silver salt, a carboxylic acid such as succinimide as a complexing agent, an imidazole compound as a reducing agent, and crystals are generated. Examples of the crystal adjusting agent for adjusting the concentration include dalixinolic acid and a plating bath supplemented with a pH adjusting agent.

[0084] The concentration of the silver salt in the plating bath is preferably 0.01 to 0.03 mol / l.

[0085] The concentration of succinimide as the complexing agent in the above bath is preferably 0.04-0. ImolZl.

[0086] The concentration of the imidazole compound as the reducing agent in the plating bath is preferably 0.04-0.lmol / 1.

[0087] The concentration of darioxylic acid as a crystal adjusting agent in the above-mentioned bath is preferably 0.001 to 0.005 molZl. [0088] In addition, examples of the pH adjuster for adjusting the pH in the above-mentioned bath include ammonia when adjusting to the alkaline side, and sulfuric acid when adjusting to the acidic side. Examples include hydrochloric acid, and sulfuric acid is preferable.

[0089] The pH of the plating bath is preferably 8 to 10 in order to increase the reaction driving force.

[0090] Further, the bath temperature of the above-mentioned bath is preferably 10-30 ° C.

[0091] Further, the dispersion means of the plating bath is preferably performed in the same manner as in the case of the reduced nickel plating bath.

[0092] The method for producing the anisotropic conductive material of the present invention is not particularly limited. For example, the conductive fine particles of the present invention are added to an insulating resin binder and mixed uniformly. For example, anisotropic conductive paste, anisotropic conductive ink, anisotropic conductive adhesive, etc., or by adding the conductive fine particles of the present invention in an insulating resin binder, After preparing a conductive composition by mixing uniformly, this conductive composition is uniformly dissolved (dispersed) in an organic solvent as necessary, or heated and melted to release paper or a release film. For example, an anisotropic conductive film, an anisotropic conductive sheet, etc. are applied to the release treatment surface of the release material such as a film to a predetermined film thickness, and dried or cooled as necessary. Corresponding to the type of anisotropic conductive material to be manufactured. Te may be taken as appropriate of the work made by the method. Alternatively, the insulating resin binder and the conductive fine particles of the present invention may be used separately without being mixed to form an anisotropic conductive material.

[0093] The resin of the insulating resin binder is not particularly limited, and examples thereof include a butyl resin such as a butyl acetate resin, a vinyl chloride resin, an acrylic resin, and a styrene resin; Resins, ethylene acetate butyl copolymer, polyamide resins, and other thermoplastic resins; epoxy resins, urethane resins, polyimide resins, unsaturated polyester resins, and curable resins composed of these curing agents; styrene Butadiene / styrene block copolymer, styrene / isoprene / styrene block copolymer, thermoplastic block copolymers such as hydrogenated products thereof; styrene-butadiene copolymer rubber, chloroprene rubber, acrylonitrile / styrene block Examples include elastomers such as copolymer rubber (rubbers). These resins may be used alone or in combination of two or more. In addition, the curable resin is a room temperature curing type, a thermosetting type, a photocurable type, It may be a moisture-curing type or a miscured cured form.

[0094] In addition to the insulating resin binder and the conductive fine particles of the present invention, the anisotropic conductive material of the present invention includes, for example, an increased amount within a range that does not hinder the achievement of the object of the present invention. Additives, softeners (plasticizers), tackifiers, antioxidants (anti-aging agents), heat stabilizers, light stabilizers, UV absorbers, colorants, flame retardants, organic solvents, etc. One or more of these may be used in combination.

[0095] Since the conductive fine particles of the present invention have the above-mentioned configuration, even when used particularly in a plasma display panel, the connection resistance is low, the current capacity at the time of connection is large, and further heating prevents migration. It has become possible to obtain a connection with high reliability.

In addition, the anisotropic conductive material and conductive connection method using the conductive fine particles of the present invention have a low connection resistance and a large current capacity at the time of connection even when used in a plasma display panel. In addition, the connection was prevented by migration and the connection reliability was high.

Brief Description of Drawings

FIG. 1 is a front sectional view schematically showing one structural example of the conductive fine particles of the present invention.

[0098] 1 ... conductive fine particles

2 ... Particle

3 ... Nickel coating

4 ... Tin plating film

5 ... Bismuth moon

6 ... Silver plating film

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to the following examples.

[0100] (Example 1)

Soak copper metal particles (purity 99% by weight) with a particle size of 5 μm in hydrogen peroxide-monosulfuric acid mixture. Purification was carried out by a wet method to obtain copper metal particles with exposed surface of the copper metal and purified surface.

[0101] Palladium was attached to the obtained copper metal particles by a two-component activation method to obtain copper metal particles to which palladium was attached.

[0102] Next, a solution containing 25 g of nickel sulfate and 1000 ml of ion-exchanged water was prepared, and 10 g of the obtained copper metal particles to which palladium adhered was mixed to prepare an aqueous suspension.

[0103] To the obtained aqueous suspension, 30 g of citrate, 80 g of sodium hypophosphite and 10 g of acetic acid were added to prepare a solution.

[0104] To the obtained solution, ammonia was used, the pH was adjusted to 10, and the bath temperature was adjusted to 60 ° C.

By reacting for about 20 minutes, particles having a nickel plating film were obtained.

[0105] Next, a solution containing 5 g of salty tin and 1000 ml of ion-exchanged water was prepared, and 15 g of the particles having the Nikkenore-Metsuki coating formed were mixed to prepare an aqueous suspension.

[0106] 30 g of thiourea and 80 g of tartaric acid were added to the obtained aqueous suspension to prepare a solution.

[0107] The obtained plating solution was brought to a bath temperature of 60 ° C and reacted for about 15 to 20 minutes to obtain particles on which a substituted tin plating film was formed.

[0108] Further, 20 g of tin chloride, 40 g of citrate, and 30 g of sodium hydroxide were added to this plating bath and reacted at a bath temperature of 60 ° C for about 15 to 20 minutes to form a tin plating film. Obtained particles.

[0109] Palladium was adhered to the obtained particles having the tin plating film by a two-component activation method to obtain particles having the tin plating film having palladium attached thereto.

[0110] Next, an aqueous suspension was prepared by preparing a solution containing 18 g of bismuth nitrate and 1000 ml of ion-exchanged water, and mixing the obtained 20 g of particles having a tin-plated film with attached palladium. did.

[0111] To the obtained aqueous suspension, 30 g of sodium citrate, 40 g of titanium (III) chloride, 40 g of titanium (IV) chloride, and 40 g of ammonium hydrogen phosphate were added to prepare a solution.

[0112] After adding 5 g of darioxynolic acid to the obtained solution, adjust the pH to 10 using ammonia, set the bath temperature to 20 ° C, and react for about 15 to 20 minutes to form a bismuth plating film. Particles were obtained.

[0113] Next, a solution containing 5 g of silver nitrate and 1000 ml of ion-exchanged water was prepared, and 24 g of the particles on which the obtained bismuth plating film was formed were mixed to prepare an aqueous suspension.

[0114] To the obtained aqueous suspension, 30 g of succinimide, 80 g of imidazole, and 5 g of darioxynolic acid were added to prepare a solution.

[0115] By using ammonia in the obtained plating solution, adjusting the pH to 9, and setting the bath temperature to 20 ° C and reacting for about 15-20 minutes, particles having a silver plating film formed were obtained. The obtained particles having the silver plating film were used as conductive fine particles.

[0116] (Example 2)

Conductive fine particles were obtained in the same manner as in Example 1 except that dibulebenzene resin fine particles having an average particle diameter of 4 μm were used in place of the copper metal particles.

[0117] (Comparative Example 1)

In the same manner as in Example 1, copper metal particles having a purified surface were obtained.

Nickel plating film, tin plating film, and bismuth plating film were not formed on the obtained copper metal particles whose surface was purified.

[0118] Next, a solution containing 10 g of silver nitrate and 1000 ml of ion-exchanged water was prepared, and 10 g of copper metal particles whose surface was purified was mixed to prepare an aqueous suspension.

[0119] To the obtained aqueous suspension, 30 g of succinimide, 80 g of imidazole, and 5 g of darioxynolic acid were added to prepare a solution.

[0120] The obtained plating solution was adjusted to pH 9 using ammonia, the bath temperature was set to 60 ° C, and the mixture was reacted for about 15 to 20 minutes to obtain particles having a silver plating film formed. The obtained particles having the silver plating film were used as conductive fine particles.

[0121] (Measurement of resistance of conductive fine particles)

For each of the obtained conductive fine particles, a micro compression tester (“DUH_200”, manufactured by Shimadzu Corporation) is used so that the resistance value can be measured. The resistance value of the conductive fine particles was measured by applying a voltage and measuring the resistance value per particle.

[0122] After conducting a PCT test (held at 80 ° C, 95% RH in a high temperature and high humidity environment for 1000 hours) Similarly, the resistance value of the conductive fine particles was measured.

Table 1 shows the evaluation results.

[0123] (Evaluation of leakage current)

As the resin binder resin, 100 parts by weight of epoxy resin (manufactured by Japan Epoxy Resin, “Epicote 828”), 2 parts by weight of trisdimethylaminoethylphenol, and 100 parts by weight of toluene were obtained. Add fine particles, mix thoroughly using a planetary stirrer, and then apply on the release film so that the thickness after drying is 7 xm, evaporate the tolene and contain conductive fine particles An adhesive film was obtained. The content of conductive fine particles was 50,000 Zcm ^{2 in the} film.

[0124] Thereafter, an adhesive film containing conductive fine particles was bonded to an adhesive film obtained without containing conductive fine particles at room temperature to obtain an anisotropic conductive film having a two-layer structure with a thickness of 17 μm. .

[0125] The obtained anisotropic conductive film was cut into a size of 5 X 5 mm. In addition, two glass substrates with a 200 μm wide, lmm long, 0.2 / im high, L / S20 β m anodized electrode with resistance measurement leads on one side are prepared. did. After attaching the anisotropic conductive film to the center of one glass substrate, align the other glass substrate so that it overlaps the electrode pattern of the glass substrate attached with the anisotropic conductive film. Combined.

[0126] Two glass substrates were subjected to thermocompression bonding under conditions of a pressure of 10 N and a temperature of 180 ° C, and then each of the anisotropic conductive films obtained for the presence or absence of a leak current between the electrodes was measured.

[0127] Further, after conducting a PCT test (held at 80 ° C, 95% RH in a high-temperature and high-humidity environment for 1000 hours), the presence or absence of leakage current between electrodes was measured in the same manner.

Table 1 shows the evaluation results.

[0128] Each conductive fine particle after thermocompression bonding was taken out, and the formation of an alloy film was examined with an energy dispersive X-ray spectrometer (manufactured by JEOL Datum). As a result, a silver-bismuth-tin alloy alloy film was formed on the conductive fine particles of Example 1, and an alloy film was not formed on the conductive fine particles of Comparative Example 1.

[0129] [Table 1] The resistance value of Example 1 Example 2 Comparative Example 1 normal conductive fine particles 1.5 X Ω 1.5 X 10- ⁶ Q

Existence of leakage between electrodes No No No

After PCT test Resistance of conductive fine particles 3.4 Χ 10 " ⁶ Ω 19.5 10" ⁶ Ω (after 80 ° C, 95SRH, 1000Hr) Existence of leakage current between electrodes No Yes

Silver-bismuth-tin silver-bismuth-tin after anisotropic conductive film thermocompression bonding

None Formation of conductive fine particle alloy coating Alloy coating Alloy coating

[0130] From Table 1, Example 1 and Example 2 showed less resistance increase after the PCT test than Comparative Example 1, and no leakage current between the electrodes. This is thought to be because silver migration occurred in Comparative Example 1 whereas migration was prevented in Example 1.

[0131] Further, energization was performed and evaluated by the following method to cope with a high voltage used in a plasma display panel.

[0132] Two glass substrates of 20 mm X 40 mm, connecting part IT ○ line width 300 μm were prepared. Epoxy resin as thermosetting resin (Japan Epoxy Resin X, “Epicoat 1009”) — _5

Each conductive fine particle obtained in 0.5 weight. / ₀ , after applying a composition in which 1.5% by weight of silica spacer is dispersed on one glass substrate, the other glass substrate is aligned and bonded so that the electrode patterns overlap, By thermocompression bonding, a test piece in the form of IT ○ Z conductive fine particle paste / soot was prepared. By applying a current of 10 mA and a voltage of 100 V to this test piece, it was judged whether or not high voltage could be handled by checking whether or not the conductive fine particles were destroyed.

As a result, in both Example 1 and Comparative Example 1, since the copper metal particles are used as the base particles, the conduction due to the destruction of the base particles, which occurs in the conductive fine particles using the resin particles as the base particles, and the like. No defects occurred. On the other hand, the conductive fine particles obtained in Example 2 were destroyed by the base material particles.

Industrial applicability

[0134] According to the present invention, even when used particularly in a plasma display panel, the connection resistance is low, the current capacity during connection is large, and migration is prevented by heating, the connection reliability is high, and the conductivity is high. Fine particles, and anisotropic conductive material using the conductive fine particles, And a conductive connection method.

Claims

The scope of the claims

[1] A particle and a conductive film formed on the particle surface by an electroless plating method,

The conductive coating has a nickel plating coating, a tin plating coating, and a bismuth plating coating formed in order from the inside by an electroless plating, and the conductive coating has a silver plating coating on the outermost surface. Conductive fine particles characterized by the above.

[2] An anisotropic conductive material, wherein the conductive fine particles according to claim 1 are dispersed in a resin binder.

[3] The conductive fine particles according to claim 1 are heated on the electrode surface to cause metal thermal diffusion to form a silver-bismuth-tin alloy coating, and a part of the softened alloy coating is applied to the electrode surface. The conductive connection method is characterized in that the contact area is expanded by flowing the liquid into the surface.