JPWO2018181546A1 - Method for selecting conductive particles, circuit connection material, connection structure and method for manufacturing the same, and conductive particles - Google Patents

Abstract

The present disclosure relates to a method for sorting conductive particles. This sorting method is a step of determining whether the metal constituting the outermost layer of the conductive particles satisfies the following first condition, and determining whether the conductive particles satisfy the following second condition. And conductive steps that satisfy both the first condition and the second condition are determined to be good. The first condition: the electric conductivity at 20 ° C. is 40 × 10 6 S / m or less. The second condition: the volume resistivity when a load of 2 kN is applied is 15 mΩcm or less.

Description

  The present disclosure relates to a method for selecting conductive particles, a circuit connection material, a connection structure, a method for manufacturing the same, and conductive particles.

  A driving IC is mounted on a liquid crystal and an OLED (Organic Light-Emitting Diode) display glass panel. The methods can be broadly classified into two types: COG (Chip-on-Glass) mounting and COF (Chip-on-Flex) mounting. In COG mounting, a driving IC is directly bonded to a glass panel using an anisotropic conductive adhesive containing conductive particles. On the other hand, in COF mounting, a driving IC is joined to a flexible tape having metal wiring, and they are joined to a glass panel using an anisotropic conductive adhesive containing conductive particles. The anisotropy here means that conduction is performed in the pressing direction and insulation is maintained in the non-pressing direction. The anisotropic conductive adhesive containing the conductive particles may be formed in a film shape in advance, and such a film is referred to as an anisotropic conductive film.

  Until now, ITO (Indium Tin Oxide) wiring has mainly been used for wiring on a glass panel, but is being replaced by IZO (Indium Zinc Oxide) for the purpose of improving productivity or smoothness. Further, in recent years, an electrode formed by laminating a plurality of Cu, Al, Ti, and the like on a glass panel, a composite multilayer electrode further formed with ITO or IZO on the outermost surface, and the like have been developed. It is necessary to obtain a stable connection resistance with respect to an electrode using such a highly flat material having high hardness such as Ti.

  Patent Literature 1 discloses a method for producing conductive fine particles having base particles and a conductive film formed on the surface thereof, and the conductive film having protrusions raised on the surface. According to this document, conductive fine particles having a conductive film having protrusions are considered to have excellent conductive reliability.

  Patent Document 2 discloses conductive particles having base particles and a nickel-boron conductive layer provided on the surface thereof. According to this document, since the nickel-boron conductive layer has an appropriate hardness, the oxide film on the surfaces of the electrodes and the conductive particles can be sufficiently removed when connecting members between the electrodes, and the connection resistance is reduced. It is said that you can.

  Patent Document 3 discloses conductive particles having resin particles, an electroless metal plating layer covering the surface thereof, and a metal sputtered layer excluding Au which forms an outermost layer. According to this document, by coating the surface of the resin particles with electroless metal plating, the adhesion to the surface of the resin particles is improved, and by forming the outermost layer as a metal sputtered layer, good connection reliability is obtained. It has been.

Japanese Patent No. 4563110 JP 2011-243455 A JP 2012-164454 A

  By the way, conventionally, as for the conductive particles used in the process of manufacturing the display or the anisotropic conductive film containing the same, a panel maker selects and uses a variety of materials suitable for the material of the electrode surface. For example, in a circuit having titanium on the surface, which is used in an organic EL display or the like, since titanium oxide is formed on the outermost surface and is made nonconductive, conductive particles having a plating layer harder than the conventional one are employed. You. This allows the conductive particles to penetrate the outermost non-conductive film and come into contact with the conductor inside the electrode during crimping, thereby realizing low resistance. However, when the conductive particles improved by such a physical method are applied to, for example, an electrode of an ITO film, there is a problem that the conductive particles before the improvement have a lower resistance and thus lack versatility. there were.

  Recently, with the rapid commodification of display-related products, competition between panel manufacturers has intensified. Some panel manufacturers are trying to unify the types of anisotropic conductive films in order to improve cost competitiveness. However, the fact is that it is difficult to unify the types of anisotropic conductive films for the following reasons.

  First, the electrode circuits of the liquid crystal display and the organic EL display are not uniform. For example, in a liquid crystal display, an oxide-based transparent conductive film (ITO, IZO, IGZO, IGO, ZnO, etc.) is mainly used. On the other hand, in an organic EL display, an electrode material mainly containing a metal such as titanium, chromium, aluminum, and tantalum is mainly used. In some cases, the surface of the electrode is coated with an organic material such as an acrylic resin or an inorganic material such as SiNx or SiOx for the purpose of protecting the electrode portion or achieving high reliability. Further, examples of electrode circuits other than the display substrate include FPC (Flexible Printed Circuit) and IC (Integrated Circuit), and various metals such as gold, copper, and nickel are used for these electrodes.

  The present disclosure has been made in view of the above circumstances, and has as its object to provide a method of selecting conductive particles having sufficiently high versatility with respect to circuit electrodes of circuit members to be connected. Another object of the present disclosure is to provide a conductive particle, a circuit connection material using the same, a connection structure, and a method for manufacturing the same.

The present disclosure relates to a method for sorting conductive particles. This sorting method, the step of determining whether the metal constituting the outermost layer of the conductive particles satisfies the following first condition, and determines whether the conductive particles satisfy the following second condition And conductive steps that satisfy both the first condition and the second condition are determined to be good.
The first condition: the electric conductivity at 20 ° C. is 40 × 10 ⁶ S / m or less. The second condition: the volume resistivity when a load of 2 kN is applied is 15 mΩcm or less.

  By adopting conductive particles that satisfy both the first condition and the second condition, circuit electrodes of various surface compositions (transparent conductive films of oxides such as ITO and metal electrodes such as Ti) can be used. In addition, the resistance at the contact interface between the conductive particles and the electrode surface can be reduced, and a good connection resistance can be obtained. The present inventors have found that the second condition is particularly useful for selecting conductive particles that can achieve good connection resistance and have high versatility. The load of 2 kN is assumed to be a state where the conductive particles are hardly flattened. Therefore, it is considered that the resistance value of the conductive particle surface can be detected with higher sensitivity than when the load is large. In an actual connection portion, conductive particles having different oblateness coexist between a pair of electrodes facing each other due to variation in the particle size of the conductive particles or minute unevenness on the electrode surface. That is, some of these conductive particles are almost flat. As described above, even if the conductive particles selected by the method according to the present disclosure are slightly flat, the conductive particles greatly contribute to lowering the resistance of the connection portion, and a good connection resistance can be obtained as a whole. On the other hand, the conductive particles that do not satisfy either one of the first and second conditions have little contribution to lowering the resistance of the connecting portion if they are slightly flat. Note that “opposite” in the present specification means that a pair of members face each other.

  According to the present disclosure, there is provided a method of selecting conductive particles having sufficiently high versatility with respect to a circuit electrode of a circuit member to be connected. Further, according to the present disclosure, a conductive particle, a circuit connection material using the same, a connection structure, and a method for manufacturing the same are provided.

FIG. 1A is an enlarged schematic cross-sectional view showing a connection portion of a connection structure manufactured using the conductive particles selected by the method according to the present disclosure, and FIG. FIG. 9 is a schematic cross-sectional view showing, on an enlarged scale, a connection portion of a connection structure manufactured using conductive particles that do not satisfy one of the second conditions. FIG. 2 is a graph showing an example of the measurement result of the volume resistivity. 3A to 3C are cross-sectional views schematically illustrating an example of a method for manufacturing a connection structure.

  Hereinafter, embodiments of the present disclosure will be described in detail. However, the present invention is not limited to the following embodiments.

<Method for sorting conductive particles>
The method for selecting conductive particles according to the present embodiment is a step of determining whether the metal constituting the outermost layer of the conductive particles satisfies the following first condition, and the conductive particles satisfy the following second condition. Determining whether or not the conductive particles satisfy the first condition and the second condition.
The first condition: the electric conductivity at 20 ° C. is 40 × 10 ⁶ S / m or less. The second condition: the volume resistivity when a load of 2 kN is applied is 15 mΩcm or less.

  By adopting conductive particles that satisfy both the first condition and the second condition, circuit electrodes of various surface compositions (transparent conductive films of oxides such as ITO and metal electrodes such as Ti) can be used. In addition, the resistance at the contact interface between the conductive particles and the electrode surface can be reduced, and a good connection resistance can be obtained.

  FIG. 1A is a schematic cross-sectional view showing, on an enlarged scale, a connection portion of a connection structure manufactured using the conductive particles selected by the method according to the present embodiment. The conductive particles 1 (conductive particles 1a and 1b) shown in the figure satisfy both the first and second conditions. FIG. 1B is a schematic cross-sectional view showing, on an enlarged scale, a connection portion of a connection structure manufactured using conductive particles 2 (2a, 2b) that do not satisfy one of the first and second conditions. is there. In these figures, the thickness of the arrow indicates the ease of current flow.

  As shown in FIG. 1A, in the connection portion of the connection structure 10, due to variation in the particle size of the conductive particles 1, between the circuit electrodes 3 a and 4 a of the pair of circuit members 3 and 4 facing each other. Has conductive particles 1 having different oblate ratios. As schematically shown in FIG. 1A, of the three conductive particles 1a, 1b, 1a, the two conductive particles 1a, 1a are hardly flat. Even if the conductive particles 1 (conductive particles 1a and 1b) have a small flatness, the connection portion greatly contributes to lowering the resistance, so that a good connection resistance can be obtained as a whole. On the other hand, the conductive particles 2 (2a, 2b) shown in FIG. 1B have little contribution to lowering the resistance of the connection portion when they are slightly flat. Although the case where the conductive particles having different flatnesses are mixed due to the variation in the particle size of the conductive particles has been exemplified here, even if the particle size of the conductive particles is sufficiently uniform, the surface of the circuit electrodes 3a and 4a may be formed. The degree of flattening of the conductive particles may change depending on the unevenness of the conductive particles.

The electrical conductivity of the metal in the outermost layer according to the first condition can be measured using, for example, a conductivity measuring device (SIGMAEST, manufactured by Nippon Felster Co., Ltd.). However, conductive particles are generally very small and difficult to measure with the same device. Therefore, instead of actually measuring the electric conductivity using such an apparatus, the element constituting the outermost layer may be analyzed, and the electric conductivity may be specified from the type of the element. From the viewpoint of lowering the connection resistance at the connection portion of the connection structure, the first condition (the electrical conductivity of the metal layer at 20 ° C.) may be 1 × 10 ⁶ to 40 × 10 ⁶ S / m, and may be 5 ×. It may be 10 ⁶ to 40 × 10 ⁶ S / m.

  The volume resistivity according to the second condition can be measured using, for example, a powder resistance measuring system (device name: PD51, manufactured by Mitsubishi Chemical Analytech Co., Ltd.). Specifically, 2.5 g of conductive particles is put into a dedicated cell of the above-described device, and the volume resistivity of the conductive particles when a load of 2 kN is applied using the above-described device can be measured. The amount of the conductive particles to be charged may be 0.5 g or more, as long as the bottom of the dedicated cell can be filled. Further, the measurement load can be arbitrarily changed.

  FIG. 2 is a graph showing an example of the measurement result of the volume resistivity. The results in FIG. 2 are measured every 2 kN from a load of 2 kN to 20 kN. In the present embodiment, a volume resistivity of 2 kN is used as an index. From the viewpoint of lowering the connection resistance at the connection portion of the connection structure and obtaining a more versatile circuit connection material, the second condition (volume resistivity when a load of 2 kN is applied) may be set to 10 mΩcm or less, and 7. It may be 5 mΩcm or less or 5 mΩcm or less.

<Conductive particles>
The conductive particles are not particularly limited as long as they have compressive properties, and examples thereof include core-shell particles having a core particle made of a resin material and a metal layer covering the core particle. The metal layer does not need to cover the entire surface of the core particle, and may have a form in which a part of the surface of the core particle is coated with the metal layer. Further, the metal layer may have a single-layer structure or a multilayer structure.

  Generally, the particle size of the conductive particles is smaller than the minimum value of the distance between the electrodes of the circuit member to be connected. When the height of the connected electrodes varies, it is preferable that the average particle size of the conductive particles is larger than the variation in height. From such a viewpoint, the average particle size of the conductive particles is preferably 1 to 50 μm, more preferably 1 to 20 μm, further preferably 2 to 10 μm, and particularly preferably 2 to 6 μm. The “average particle size” as used herein means a value determined by observing with a differential scanning electron microscope. That is, one particle is arbitrarily selected, observed with a differential scanning electron microscope, and its maximum diameter and minimum diameter are measured. The square root of the product of the maximum diameter and the minimum diameter is defined as the particle diameter. With this method, the average particle size is determined by measuring the particle size of 50 arbitrarily selected particles and taking the average value.

  The volume resistivity of the conductive particles to be sorted when a load of 2 kN is applied is 15 mΩcm or less as described above. From the viewpoint of lowering the connection resistance at the connection portion of the connection structure and obtaining a more versatile circuit connection material, the volume resistivity is preferably 0.1 to 10 mΩcm, more preferably 0.1 to 7 mΩcm. It is 0.5 mΩcm, more preferably 0.1 to 5 mΩcm or less.

  The compression elastic modulus (20% K value) of the conductive particles when subjected to 20% compression displacement (at 20% compression) at 25 ° C. is preferably 0.5 to 15 GPa, more preferably 1.0 to 10 GPa. . The compression hardness K value is an index of the softness of the conductive particles. When the 20% K value is in the above range, the conductive particles are appropriately flattened between the electrodes when the opposing electrodes are connected to each other, and the electrodes and the particles are hardly compressed. Therefore, it is easy to secure a contact area, and thus there is a tendency that connection reliability can be further improved.

The 20% K value of the conductive particles can be determined by the following method using a Fisher scope H100C (manufactured by Fisher Instrument). One conductive particle sprayed on a slide glass is compressed at a speed of 0.33 mN / sec. Thus, a stress-strain curve is obtained, and a 20% K value is determined from the curve. Specifically, when the load F (N), the displacement S (mm), the radius R (mm) of the particles, the elastic modulus E (Pa), and the Poisson's ratio σ, the compression formula of the elastic sphere F = (2 ^{1 / By using} 2/3) × (S ^3/2 ) × (E × R ^1/2 ) / (1−σ ² ), the following equation K = E / (1−σ ² ) = (3/2 ^{1 / 2) × F × (S -3/2} ) can be determined from the × ^{(R -1/2).} Further, assuming that the deformation rate is X (%) and the diameter of the sphere is D (μm), the K value at an arbitrary deformation rate can be obtained by the following equation: K = 3000F / (D ² × X ^3/2 ) × 10 ⁶ The deformation rate X is calculated by the following equation: X = (S / D) × 100. The maximum test load in the compression test is set to, for example, 50 mN.

(Core particles)
As described above, the conductive particles in the present embodiment are core-shell type particles and include core particles. Since the conductive particles have the core particles, the range of the physical property design of the conductive particles themselves is greatly expanded, and the size uniformity of the conductive particles is also improved as compared with the metal powder or the like. It becomes easier to optimize the conductive particles.

  Specific examples of the core particles include various plastic particles. Plastic particles include, for example, acrylic resins such as polymethyl methacrylate and polymethyl acrylate, polyolefin resins such as polyethylene, polypropylene, polyisobutylene and polybutadiene, polystyrene resins, polyester resins, polyurethane resins, polyamide resins, and epoxy resins. Resin, polyvinyl butyral-based resin, rosin-based resin, terpene-based resin, phenol-based resin, guanamine-based resin, melamine-based resin, oxazoline-based resin, carbodiimide-based resin, at least one resin selected from the group consisting of silicone-based resin and the like What is formed is mentioned. The plastic particles may be a composite of these resins and an inorganic substance such as silica.

  As the plastic particles, from the viewpoint of easy control of the compression recovery rate and compression hardness K value, plastic particles made of a resin obtained by polymerizing one type of a polymerizable monomer having an ethylenically unsaturated group, Alternatively, plastic particles made of a resin obtained by copolymerizing two or more polymerizable monomers having an ethylenically unsaturated group can be used. When obtaining a resin by copolymerizing two or more polymerizable monomers having an ethylenically unsaturated group, using a non-crosslinkable monomer and a crosslinkable monomer in combination, their copolymerization ratio, By appropriately adjusting the type, the compression recovery rate and the compression hardness K value of the plastic particles can be easily controlled. As the non-crosslinkable monomer and the crosslinkable monomer, for example, monomers described in JP-A-2004-165019 can be used.

  The average particle size of the plastic particles is preferably 1 to 50 μm. In addition, from the viewpoint of high-density mounting, the average particle size of the plastic particles is more preferably 1 to 20 μm. Further, from the viewpoint of maintaining the connection state more stably when unevenness of the electrode surface is uneven, the average particle size of the plastic particles is more preferably 2 to 10 μm.

(Metal layer)
In the present embodiment, the outermost layer of the conductive particles is formed of a metal layer made of a metal having an electric conductivity at 20 ° C. of 40 × 10 ⁶ S / m or less. By adopting such a configuration, good connection reliability can be obtained. Here, the outermost layer means a range within 50 nm from the surface of the metal layer. The electric conductivity at 20 ° C. of the metal constituting the outermost layer is 40 × 10 ⁶ S / m or less, preferably 1 × 10 ⁶ to 40 × 10 ⁶ S / m, more preferably 5 × 10 ⁶ to 5 × 10 ⁶ S / m. It is 20 × 10 ⁶ S / m.

The metal layer may be made of a single metal or may be made of an alloy. Examples of the metal having an electric conductivity of 40 × 10 ⁶ S / m or less include Al, Ti, Cr, Fe, Co, Ni, Zn, Zr, Mo, Pd, In, Sn, W, and Pt. The metal layer is, for example, at least one metal selected from the group consisting of Ni, Ni / Au (an embodiment in which an Au layer is provided on a Ni layer; the same applies hereinafter), Ni / Pd, Ni / W, Cu, and NiB. Is preferably formed. The metal layer is formed by a general method such as plating, vapor deposition, and sputtering, and may be a thin film. When the metal layer is formed by plating the plastic particles, the metal layer preferably contains Ni, Pd or W from the viewpoint of the plating property for the plastic. Further, it is preferable that the metal layer contains Ni, since the removal of the resin between the electrode and the particles at the time of pressure bonding becomes more effective and lower resistance is obtained. Ni is said to have excellent plating properties and corrosion resistance as compared with Au, Cu, and Ag, which have high electrical conductivity, and also excellent supply stability and price, in addition to being excellent in resin rejection during pressure bonding. There are advantages.

  The thickness of the metal layer is preferably from 10 to 1000 nm, more preferably from 20 to 500 nm, and still more preferably from 50 to 250 nm, from the viewpoint of achieving a balance between conductivity and cost.

  The conductive particles are formed by attaching a layer of an insulating material (for example, an organic film) or insulating fine particles (for example, organic fine particles or inorganic fine particles) to the outside of the metal layer from the viewpoint of improving the insulating property between adjacent electrodes. May be provided. The thickness of the adhesion layer is preferably about 50 to 1000 nm. Note that the adhesion layer is preferably formed on conductive particles that have been confirmed to satisfy the first and second conditions. The thicknesses of the metal layer and the adhesion layer can be measured by, for example, a scanning electron microscope (SEM), a transmission electron microscope (TEM), an optical microscope, or the like. Further, the metal layer may have projections formed on the surface. Since the metal layer has protrusions, the resin can be effectively removed at the time of pressure bonding, the number of contact points with the electrode increases, and the inside of the electrode can be brought into contact with the conductive particles. Resistance can be achieved.

<Circuit connection material>
The circuit connection material according to the present embodiment is used for bonding circuit members and electrically connecting circuit electrodes (for example, connection terminals) included in each circuit member. The circuit connection material includes an adhesive component that is cured by light or heat, and conductive particles dispersed in the adhesive component, and the conductive particles satisfy both the first and second conditions. .

  Circuit connection materials are prepared by dispersing conductive particles in an adhesive component. As the circuit connection material, a paste-like adhesive composition may be used as it is, or an anisotropic conductive film obtained by molding this into a film may be used. The amount of the conductive particles is 0.1 to 30 parts by volume when the total volume of the circuit connection material is 100 parts by volume from the viewpoint of achieving a good balance between the conductivity between the counter electrodes and the insulation between the adjacent electrodes. Part, more preferably 0.5 to 15 parts by volume, even more preferably 1 to 7.5 parts by volume.

  The amount of the adhesive component is determined from the viewpoint that the gap between the electrodes is maintained at the time of circuit connection and after the connection, and the strength and elastic modulus required for providing excellent connection reliability are easily secured. Is 100 parts by mass, preferably 10 to 90 parts by mass, more preferably 20 to 80 parts by mass, and still more preferably 30 to 70 parts by mass.

  The adhesive component is not particularly limited. For example, a composition containing an epoxy resin and a latent curing agent for the epoxy resin (hereinafter, referred to as a “first composition”), a radical polymerizable substance, and free radicals by heating (Hereinafter, referred to as a “second composition”), or a mixed composition of the first composition and the second composition.

  Examples of the epoxy resin contained in the first composition include bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, phenol novolak epoxy resin, cresol novolak epoxy resin, bisphenol A novolak epoxy resin, and bisphenol. F novolak type epoxy resin, alicyclic epoxy resin, glycidyl ester type epoxy resin, glycidylamine type epoxy resin, hydantoin type epoxy resin, isocyanurate type epoxy resin, aliphatic chain epoxy resin and the like. These epoxy resins may be halogenated or hydrogenated. These epoxy resins may be used in combination of two or more.

  The latent curing agent contained in the first composition may be any one capable of curing an epoxy resin. Examples of such a latent curing agent include an anionic polymerizable catalytic curing agent and a cationic polymerizable curing agent. And a polyaddition type curing agent. These can be used alone or as a mixture of two or more. Of these, an anionic or cationically polymerizable catalytic curing agent is preferred from the viewpoint that it has excellent rapid curability and does not require consideration of chemical equivalents.

  Examples of the anionic or cationic polymerizable catalytic curing agent include imidazole curing agents, hydrazide curing agents, boron trifluoride-amine complexes, sulfonium salts, amine imides, diamino maleonitriles, melamines and derivatives thereof, polyamine salts, and dicyandiamide. And the like, and these modified products can also be used. Examples of the polyaddition type curing agent include polyamines, polymercaptans, polyphenols, and acid anhydrides.

  When a tertiary amine, imidazole or the like is blended as an anion-polymerizable catalytic curing agent, the epoxy resin is cured by heating at a medium temperature of about 160 to 200 ° C. for several tens of seconds to several hours. For this reason, the pot life can be made relatively long. As the cationically polymerizable catalytic curing agent, for example, a photosensitive onium salt (such as an aromatic diazonium salt or an aromatic sulfonium salt) that cures an epoxy resin by irradiation with energy rays is preferable. In addition to the energy ray irradiation, aliphatic sulfonium salts and the like are activated by heating to cure the epoxy resin. This type of curing agent is preferable because it has a characteristic of fast curing.

  The potable life is extended when these latent curing agents are microencapsulated by coating them with polymer substances such as polyurethane or polyester, metal thin films such as nickel or copper, or inorganic substances such as calcium silicate. It is preferable because it is possible. The amount of the latent curing agent contained in the first composition is preferably from 20 to 80 parts by mass, and more preferably from 30 to 70 parts by mass, based on 100 parts by mass of the total amount of the epoxy resin and the film-forming material to be blended if necessary. Parts by mass are more preferred.

  The radical polymerizable substance contained in the second composition is a substance having a functional group that is polymerized by a radical. Examples of such a radical polymerizable substance include an acrylate (including the corresponding methacrylate; the same applies hereinafter) compound, an acryloxy (including the corresponding methacryloxy; the same applies hereinafter) compound, a maleimide compound, a citraconic imide resin, a nadiimide resin, and the like. Can be The radically polymerizable substance may be used in a state of a monomer or an oligomer, and it is also possible to use a monomer and an oligomer together. Specific examples of the acrylate compound include methyl acrylate, ethyl acrylate, isopropyl acrylate, isobutyl acrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, trimethylolpropane triacrylate, tetramethylol methane tetraacrylate, 2-hydroxy-1,3- Diacryloxypropane, 2,2-bis [4- (acryloxymethoxy) phenyl] propane, 2,2-bis [4- (acryloxypolyethoxy) phenyl] propane, dicyclopentenyl acrylate, tricyclodecanyl acrylate , Tris (acryloyloxyethyl) isocyanurate, urethane acrylate and the like. These can be used alone or in combination of two or more. If necessary, a polymerization inhibitor such as hydroquinone and methyl ether hydroquinone may be appropriately used. Further, from the viewpoint of improving heat resistance, the acrylate compound preferably has at least one substituent selected from the group consisting of a dicyclopentenyl group, a tricyclodecanyl group, and a triazine ring. As the radical polymerizable substance other than the acrylate compound, for example, a compound described in WO 2009/063827 can be suitably used. These are used alone or in combination of two or more.

  Further, it is preferable to use a radical polymerizable substance having a phosphate ester structure represented by the following formula (I) in combination with the above radical polymerizable substance. In this case, since the adhesive strength to the surface of an inorganic substance such as a metal is improved, it is suitable for bonding circuit electrodes.

［式中、ｎは１〜３の整数を示す。］

[In the formula, n represents an integer of 1 to 3. ]

  A radically polymerizable substance having a phosphate ester structure is obtained by reacting phosphoric anhydride with 2-hydroxyethyl (meth) acrylate. Specific examples of the radical polymerizable substance having a phosphate ester structure include mono (2-methacryloyloxyethyl) acid phosphate and di (2-methacryloyloxyethyl) acid phosphate. These can be used alone or in combination of two or more.

  The compounding amount of the radical polymerizable substance having a phosphate ester structure represented by the above formula (I) is 0.01 to 50 parts by mass based on 100 parts by mass of the radical polymerizable substance and the film forming material to be compounded as required. It is preferable that the amount is from 0.5 to 5 parts by mass.

  The radical polymerizable substance can be used in combination with allyl acrylate. In this case, the compounding amount of the allyl acrylate is preferably 0.1 to 10 parts by mass with respect to a total of 100 parts by mass of the radical polymerizable substance and the film forming material compounded as necessary, and -5 parts by mass is more preferred.

  The curing agent contained in the second composition that generates free radicals by heating is a curing agent that decomposes by heating to generate free radicals. Examples of such a curing agent include peroxides and azo compounds. Such a curing agent is appropriately selected depending on the intended connection temperature, connection time, pot life and the like. From the viewpoints of high reactivity and improvement in pot life, an organic peroxide having a half-life of 10 hours at a temperature of 40 ° C. or more and a half-life of 1 minute of 180 ° C. or less is preferable. An organic peroxide having a temperature of 60 ° C. or more and a half-life of 1 minute of 170 ° C. or less is more preferable.

  When the connection time is set to 25 seconds or less, the curing agent may be used in an amount of 2 to 10 parts by mass with respect to a total of 100 parts by mass of the radical polymerizable substance and the film forming material to be added as required. It is more preferably 4 to 8 parts by mass. Thereby, a sufficient reaction rate can be obtained. In addition, the compounding amount of the curing agent when the connection time is not limited is 0.05 to 20 parts by mass with respect to a total of 100 parts by mass of the radical polymerizable substance and the film forming material compounded as necessary. More preferably, it is 0.1 to 10 parts by mass.

  Specific examples of the curing agent contained in the second composition that generates free radicals by heating include diacyl peroxide, peroxydicarbonate, peroxyester peroxyketal, dialkyl peroxide, hydroperoxide, and silyl peroxide. And the like. Further, from the viewpoint of suppressing corrosion of the circuit electrode, a curing agent having a concentration of chlorine ion and an organic acid of 5000 ppm or less is preferable, and a curing agent having a small amount of organic acid generated after thermal decomposition is more preferable. Specific examples of such a curing agent include a peroxyester, a dialkyl peroxide, a hydroperoxide, a silyl peroxide, and the like, and a curing agent selected from peroxyesters having high reactivity is more preferable. In addition, the said hardening | curing agent can be mixed and used suitably.

  Examples of peroxy esters include cumyl peroxy neodecanoate, 1,1,3,3-tetramethylbutyl peroxy neodecanoate, 1-cyclohexyl-1-methylethyl peroxy neodecanoate, t-hexyl Peroxyneodecanodate, t-butylperoxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanonate, 2,5-dimethyl-2,5-di (2-ethyl Hexanoylperoxy) hexane, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanonate, t-hexylperoxy-2-ethylhexanonate, t-butylperoxy-2-ethylhexanonate , T-butylperoxyisobutyrate, 1,1-bis (t-butylperoxy) cyclohexane, t Hexylperoxyisopropyl monocarbonate, t-butylperoxy-3,5,5-trimethylhexanonate, t-butylperoxylaurate, 2,5-dimethyl-2,5-di (m-toluoylperoxy ) Hexane, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, t-butylperoxyacetate and the like. As the curing agent other than the peroxyester, which generates free radicals by heating, for example, a compound described in WO2009 / 063827 can be suitably used. These are used alone or in combination of two or more.

  These curing agents can be used alone or in admixture of two or more, and may be used in combination with a decomposition accelerator, a decomposition inhibitor and the like. Further, these curing agents may be coated with a polyurethane-based or polyester-based polymer substance or the like to be microencapsulated. A microencapsulated curing agent is preferred because the pot life is extended.

  A film forming material may be added to the circuit connection material of the present embodiment, if necessary. The film-forming material, when the liquid material is solidified and the constituent composition is in the form of a film, facilitates handling of the film in a normal state (normal temperature and normal pressure), and does not easily tear, break, or stick. It imparts mechanical properties and the like to the film. Examples of the film forming material include a phenoxy resin, a polyvinyl formal resin, a polystyrene resin, a polyvinyl butyral resin, a polyester resin, a polyamide resin, a xylene resin, and a polyurethane resin. Among these, a phenoxy resin is preferable because of its excellent adhesiveness, compatibility, heat resistance, and mechanical strength.

  The phenoxy resin is a resin obtained by reacting a bifunctional phenol with epihalohydrin until it is polymerized, or by polyaddition of a bifunctional epoxy resin and a bifunctional phenol. The phenoxy resin is prepared, for example, by reacting 1 mol of a bifunctional phenol with 0.985 to 1.015 mol of epihalohydrin in a non-reactive solvent at a temperature of 40 to 120 ° C. in the presence of a catalyst such as an alkali metal hydroxide. Can be obtained. In addition, as the phenoxy resin, from the viewpoint of the mechanical and thermal properties of the resin, the blending equivalent ratio of the bifunctional epoxy resin and the bifunctional phenol is particularly set to epoxy group / phenol hydroxyl group = 1 / 0.9 to 1 / 1.1, and in the presence of a catalyst such as an alkali metal compound, an organic phosphorus compound, or a cyclic amine compound, an amide, ether, ketone, lactone, alcohol, or other organic compound having a boiling point of 120 ° C. or higher. It is preferably obtained by heating at 50 to 200 ° C. in a solvent at a reaction solid content of 50% by mass or less to cause a polyaddition reaction. The phenoxy resins may be used alone or in combination of two or more.

  Examples of the bifunctional epoxy resin include bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol AD epoxy resin, bisphenol S epoxy resin, biphenyl diglycidyl ether, and methyl-substituted biphenyl diglycidyl ether. Bifunctional phenols have two phenolic hydroxyl groups. Examples of the bifunctional phenols include hydroquinones, bisphenols such as bisphenol A, bisphenol F, bisphenol AD, bisphenol S, bisphenol fluorene, methyl-substituted bisphenol fluorene, dihydroxybiphenyl, and methyl-substituted dihydroxybiphenyl. The phenoxy resin may be modified (for example, epoxy modified) with a radical polymerizable functional group or another reactive compound.

  The compounding amount of the film forming material is preferably 10 to 90 parts by mass, more preferably 20 to 60 parts by mass, when the total mass of the circuit connecting material is 100 parts by mass.

The circuit connection material of the present embodiment may further include a polymer or a copolymer containing at least one of acrylic acid, acrylic acid ester, methacrylic acid ester and acrylonitrile as a monomer component. Here, from the viewpoint of excellent stress relaxation, the circuit connection material preferably contains a glycidyl acrylate containing a glycidyl ether group and / or a copolymer acrylic rubber containing glycidyl methacrylate in combination. The weight average molecular weight of these acrylic rubbers is preferably 200,000 or more from the viewpoint of increasing the cohesive strength of the adhesive composition.
The circuit connection material of the present embodiment further includes a rubber fine particle, a filler, a softener, an accelerator, an antioxidant, a coloring agent, a flame retardant, a thixotropic agent, a coupling agent, a phenol resin, a melamine resin, and an isocyanate. And the like.

  The average particle size of the rubber fine particles is not more than twice the average particle size of the conductive particles to be blended, and the storage elastic modulus at room temperature (25 ° C.) is the storage elasticity of the conductive particles and the adhesive composition at room temperature. It is preferable that the ratio is not more than 1/2 of the ratio. In particular, when the material of the rubber fine particles is silicone, acrylic emulsion, SBR, NBR or polybutadiene rubber, it is preferable to use them alone or as a mixture of two or more. These three-dimensionally crosslinked rubber fine particles have excellent solvent resistance and are easily dispersed in the adhesive composition.

  The filler can improve connection reliability and the like of electrical characteristics between circuit electrodes. As the filler, for example, those having an average particle size of 1/2 or less of the average particle size of the conductive particles can be suitably used. In addition, when particles having no conductivity are used in combination, the particles having an average particle diameter equal to or less than the average particle size of the particles having no conductivity can be used. The compounding amount of the filler is preferably 5 to 60 parts by mass based on 100 parts by mass of the adhesive composition. When the amount is 60 parts by mass or less, the effect of improving connection reliability tends to be more sufficiently obtained, and when the amount is 5 parts by mass or more, the effect of adding a filler tends to be sufficiently obtained. .

  As the coupling agent, a compound containing an amino group, a vinyl group, an acryloyl group, an epoxy group or an isocyanate group is preferable because the adhesiveness is improved.

  The circuit connection material melts and flows at the time of connection to obtain a connection between opposing circuit electrodes and then hardens to maintain the connection. The fluidity of the circuit connection material is an important factor. The following are examples of indices indicating this. That is, when a circuit connection material of 5 mm × 5 mm with a thickness of 35 μm is sandwiched between two glass plates of 15 mm × 15 mm with a thickness of 0.7 mm and heated and pressed at 170 ° C., 2 MPa, and 10 seconds. The value of the fluidity (B) / (A) expressed by using the area (A) of the main surface of the circuit connection material before heating and pressing and the area (B) of the main surface after heating and pressing is 1 0.3 to 3.0, and more preferably 1.5 to 2.5. When the ratio is 1.3 or more, the fluidity is suitable, and good connection tends to be easily obtained. When the ratio is 3.0 or less, bubbles are hardly generated and the reliability tends to be excellent.

  The elastic modulus at 40 ° C. after curing of the circuit connecting material is preferably 100 to 3000 MPa, more preferably 500 to 2000 MPa. The elastic modulus of the circuit connection material after curing can be measured using, for example, a dynamic viscoelasticity measuring device (DVE, DMA, etc.).

  The circuit connection material of the present embodiment includes COG connection (Chip on Glass), FOB (Flex on Board) connection, FOG (Flex on Glass) connection, FOF (Flex on Flex) connection, FOP (Flex on Polymer) connection, COP. (Chip on Polymer) connection, COF (Chip on Flex) connection and the like.

The COG connection is, for example, a method of connecting an IC to an organic EL panel or an LCD panel. A circuit electrode formed on the IC is connected to a circuit electrode formed on a glass substrate constituting the organic EL panel or the LCD panel. Refers to a connection.
The FOB connection refers to a connection between a circuit electrode formed on a flexible substrate and a circuit electrode formed on a printed wiring board, for example, represented by TCP (Tape Carrier Package), COF, and FPC. The FOG connection refers to a connection between a circuit electrode formed on a flexible substrate and a circuit electrode formed on a glass substrate constituting an organic EL panel or an LCD panel, such as TCP, COF, and FPC. The FOF connection refers to a connection between a circuit electrode formed on a flexible substrate and a circuit electrode formed on the flexible substrate, for example, represented by TCP, COF, and FPC. The FOP connection refers to a connection between a circuit electrode formed on a flexible substrate and a circuit electrode formed on a polymer substrate constituting an organic EL panel or an LCD panel. COP connection refers to connection between a circuit electrode formed on an IC and a circuit electrode formed on a plastic substrate. COF connection refers to a connection between a circuit electrode formed on an IC and a circuit electrode formed on a flexible substrate.

<Connection structure>
The circuit connection structure of the present embodiment has a first circuit member having a first circuit electrode, a second circuit member having a second circuit electrode, a first circuit member and a second circuit member. And a connection portion made of a cured product of the above-described circuit connection material, interposed between them. In the present embodiment, as the material of the circuit electrode, Ti, Al, Mo, Co, Cu, Cr, Sn, Zn, Ga, In, Ni, Au, Ag, V, Sb, Bi, Re, Ta, Nb, W or the like can be used. The thickness of the circuit electrode is preferably from 100 to 5000 nm, more preferably from 100 to 2500 nm, from the viewpoint of balancing connection resistance and cost. Further, the lower limit can be set to 500 nm.

  The circuit connection structure of the present embodiment includes a first circuit member having a first circuit electrode and a second circuit member having a second circuit electrode, and a first circuit electrode and a second circuit electrode. Are arranged so as to face each other, a circuit connecting material is interposed between the first circuit electrode and the second circuit electrode which are opposed to each other, and heated and pressurized, so that the first circuit electrode and the second circuit electrode Can be manufactured by electrically connecting Thus, the circuit connecting material of the present embodiment is useful as a material for bonding electric circuits to each other.

  More specifically, examples of the circuit member include chip components such as a semiconductor chip, a resistor chip, and a capacitor chip, and a substrate such as a printed board. These circuit members are usually provided with a large number (in some cases, a single electrode) of the above-mentioned circuit electrodes. At least a part of these circuit electrodes are opposed to each other, a circuit connecting material is interposed between the opposed circuit electrodes, and at least one set of circuit members is heated and pressed to electrically connect the opposed circuit electrodes to each other. Connecting. At this time, the circuit electrodes facing each other are electrically connected via the conductive particles included in the circuit connection material, while the insulation between the adjacent circuit electrodes is maintained. Thus, the circuit connection material of the present embodiment exhibits anisotropic conductivity.

  An embodiment of a method for manufacturing a circuit connection structure will be described with reference to FIGS. 3 (a) to 3 (c). FIG. 3A is a process sectional view before connecting circuit members, FIG. 3B is a process sectional view when connecting circuit members, and FIG. It is a process sectional view after connection.

  First, as shown in FIG. 3A, a circuit member 20 having a circuit electrode 21a and a circuit board 21b provided on an organic EL panel 21 and a circuit member 30 having a circuit electrode 31a provided on a substrate 31 are formed. prepare. Then, the circuit connection material 5 formed into a film is placed on the circuit electrode 21a.

  Next, as shown in FIG. 3B, the substrate 31 provided with the circuit electrode 31a is positioned on the circuit connecting material 5 while the circuit electrode 21a and the circuit electrode 31a are positioned so as to face each other. And the circuit connecting material 5 is interposed between the circuit electrode 21a and the circuit electrode 31a. The circuit electrodes 21a and 31a have a structure (not shown) in which a plurality of electrodes are arranged in the depth direction. Since the circuit connection material 5 is in the form of a film, it is easy to handle. For this reason, the circuit connecting material 5 can be easily interposed between the circuit electrode 21a and the circuit electrode 31a, and the work of connecting the circuit member 20 and the circuit member 30 can be facilitated.

  Next, the circuit connecting material 5 is pressurized in the direction of arrow A in FIG. 3B through the organic EL panel 21 and the substrate 31 while heating to perform a curing process. As a result, a circuit connection structure 50 in which the circuit members 20 and 30 are connected to each other via the cured product 5a of the circuit connection material as shown in FIG. 3C is obtained. As the curing method, one or both of heating and light irradiation can be employed depending on the adhesive composition used.

  Hereinafter, the present disclosure will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

(1) Preparation of conductive particles Eleven types of conductive particles A to K shown in Table 1 below were prepared. Each of these conductive particles is a core-shell particle composed of a core made of plastic particles and a metal layer (nickel layer) covering the core particle as a shell. The electrical conductivity of nickel is 14.5 × 10 ⁶ S / m. Among the conductive particles A to K, the conductive particles A to E and the conductive particles H and J satisfied both the first and second conditions.

<Example 1>
(2) Preparation of anisotropic conductive film (preparation of phenoxy resin solution)
50 g of a phenoxy resin (product name: PKHC, manufactured by Union Carbide Co., Ltd., weight average molecular weight 5000) is dissolved in a mixed solvent of toluene / ethyl acetate = 50/50 (mass ratio), and a phenoxy resin having a solid content of 40% by mass. The solution was used.

(Synthesis of urethane acrylate)
In a 2 L (liter) four-necked flask equipped with a thermometer, a stirrer, an inert gas inlet, and a reflux condenser, 4000 parts by mass of polycarbonate diol (manufactured by Aldrich, number average molecular weight Mn = 2000) and 2-hydroxy A reaction liquid was prepared by charging 238 parts by mass of ethyl acrylate, 0.49 parts by mass of hydroquinone monomethyl ether, and 4.9 parts by mass of a tin catalyst. To the reaction solution heated to 70 ° C., 666 parts by mass of isophorone diisocyanate (IPDI) was uniformly dropped over 3 hours to cause a reaction. After the completion of the dropwise addition, the reaction was continued for 15 hours. When the NCO% (NCO content) became 0.2% by mass or less, the reaction was regarded as completed, and a urethane acrylate was obtained. The NCO% was confirmed by an automatic potentiometric titrator (trade name: AT-510, manufactured by Kyoto Electronics Industry Co., Ltd.). As a result of analysis by GPC, the weight average molecular weight of urethane acrylate was 8,500 (standard polystyrene equivalent). Table 2 shows the GPC measurement conditions.

(Preparation of adhesive composition-containing liquid)
A phenoxy resin solution weighed so as to contain 50 g of a solid content from the phenoxy resin solution, 30 g of the urethane acrylate, 15 g of isocyanurate type acrylate (product name: M-215, manufactured by Toagosei Co., Ltd.), and phosphoric acid An adhesive composition-containing liquid was prepared by mixing 1 g of the ester type acrylate and 4 g of benzoyl peroxide (product name: Niper BMT-K40, manufactured by NOF CORPORATION) as a free radical generator.

(Production of anisotropic conductive film)
5 parts by mass of the conductive particles A were dispersed in 100 parts by mass of the liquid containing the adhesive composition to prepare a liquid containing a circuit connection material. This circuit connection material-containing liquid was applied on a 50 μm-thick polyethylene terephthalate (PET) film having one surface treated using a coating apparatus, and then dried with hot air at 70 ° C. for 3 minutes. Thus, an anisotropic conductive film having a thickness of 20 μm was obtained on the PET film. When the total mass of the anisotropic conductive film was 100 parts by volume, the contents of the adhesive component and the conductive particles were 97 parts by volume and 3 parts by volume, respectively.

(3) Preparation of connection structure (electrode outermost surface: titanium)
An anisotropic conductive film with a PET film was cut into a predetermined size (width 1.5 mm × length 3 cm). The surface on which the anisotropic conductive film is formed (adhesion surface) is transferred from the outermost surface onto a glass substrate (thickness 0.7 mm) coated with titanium (thickness 50 nm) and aluminum (thickness 250 nm) in this order. did. The transfer conditions were 70 ° C., 1 MPa and 2 seconds. After peeling off the PET film, a flexible circuit board (FPC) having 600 tin-plated copper circuits having a pitch of 50 μm and a thickness of 8 μm was temporarily fixed on the anisotropic conductive film. The condition of the temporary fixing was 24 ° C. and 0.5 MPa for 1 second. Next, this was set in the main press bonding apparatus, and a silicone rubber sheet having a thickness of 200 μm was used as a cushioning material. From the FPC side, heating and pressing were performed at 170 ° C. and 3 MPa for 6 seconds using a heat tool, and connected over a width of 1.5 mm. did. Thus, a connection structure was obtained.

(4) Preparation of connection structure (electrode outermost surface: ITO)
A connection structure was obtained in the same manner as described above, except that a glass substrate coated with ITO (100 nm in thickness) was used instead of the glass substrate coated with titanium and aluminum in order from the outermost surface. Was.

(5) Preparation of connection structure (electrode outermost surface: IZO)
Instead of the above glass substrate coated in the order of titanium and aluminum from the outermost surface, a glass substrate coated in the order of IZO (film thickness 100 nm), Cr (film thickness 50 nm) and aluminum (film thickness 200 nm) from the outermost surface is used. A connection structure was obtained in the same manner as described above except for the above.

(6) Measurement of connection resistance The connection resistance of the two types of connection structures obtained was measured as follows. The resistance between adjacent circuits of the FPC including the connection portion of the connection structure was measured with a multimeter (device name: TR6845, manufactured by Advantest Corporation). In addition, the average value was obtained by measuring the resistance of 40 points between adjacent circuits, and this was defined as the connection resistance. Table 3 shows the results.

<Examples 2 to 5 and Comparative Examples 1 and 2>
Except that the conductive particles A to B were used instead of the conductive particles A, three types of connection structures were produced in the same manner as in Example 1, and the connection resistances thereof were measured. Table 3 shows the results.

  According to the present disclosure, there is provided a method of selecting conductive particles having sufficiently high versatility with respect to a circuit electrode of a circuit member to be connected. Further, according to the present disclosure, a conductive particle, a circuit connection material using the same, a connection structure, and a method for manufacturing the same are provided.

1, 1a, 1b ... conductive particles, 3, 4, 20, 30 ... circuit members, 3a, 4a, 21a, 31a ... circuit electrodes, 5 ... circuit connection materials, 5a ... cured products of circuit connection materials, 10, 50 ... Connection structure

Claims (13)

A method for sorting conductive particles,
A step of determining whether the metal constituting the outermost layer of the conductive particles satisfies the following first condition,
A step of determining whether the conductive particles satisfy the following second condition,
Including
A method for selecting conductive particles, wherein a conductive particle that satisfies both the first condition and the second condition is determined to be good.
The first condition: the electric conductivity at 20 ° C. is 40 × 10 ⁶ S / m or less. The second condition: the volume resistivity when a load of 2 kN is applied is 15 mΩcm or less. A circuit connection material used for bonding circuit members together and electrically connecting circuit electrodes included in each circuit member,
An adhesive component that is cured by light or heat,
Conductive particles dispersed in the adhesive component,
Including
A circuit connecting material, wherein the conductive particles are conductive particles determined to be good by the method for selecting conductive particles according to claim 1.   3. The circuit connecting material according to claim 2, wherein the circuit connecting material is formed in a film shape.   The circuit connection material according to claim 2, wherein the connection is a COG connection, a FOB connection, a FOG connection, a FOF connection, a FOP connection, a COP connection, or a COF connection. A step of interposing the circuit connection material according to any one of claims 2 to 4 between a pair of circuit members arranged to face each other,
It is made of a cured product of the circuit connection material by heating and pressing, and the circuit members are bonded between the pair of circuit members so that the circuit electrodes of the circuit members are electrically connected to each other. Forming a connecting portion to be connected;
A method for manufacturing a connection structure including: A pair of circuit members arranged facing each other,
A circuit connecting material according to any one of claims 2 to 4, wherein the circuit electrode is provided between the pair of circuit members, and the circuit electrodes of the respective circuit members are electrically connected to each other. A connection portion for bonding the circuit members to each other,
A connection structure comprising: A metal layer having an electric conductivity at 20 ° C. of 40 × 10 ⁶ S / m or less;
Conductive particles having a volume resistivity of 15 mΩcm or less when a load of 2 kN is applied.   The conductive particle according to claim 7, wherein the metal layer includes Ni. Further comprising core particles made of a resin material,
The conductive particle according to claim 7, wherein the metal layer is formed on a surface of the core particle.   The conductive particles according to claim 7, wherein the metal layer has a protrusion.   The conductive particles according to claim 7, further comprising an organic film, organic fine particles, or inorganic fine particles disposed on a surface of the metal layer.   The conductive particles according to any one of claims 7 to 11, wherein the conductive particles have an average particle size of 1 to 50 m.   The conductive particles according to any one of claims 7 to 12, wherein an elastic modulus at 20% compression is 0.1 to 15 GPa.

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