WO2018181546A1

WO2018181546A1 - Conductive particle sorting method, circuit connection material, connection structure body and manufacturing method therefor, and conductive particle

Info

Publication number: WO2018181546A1
Application number: PCT/JP2018/012922
Authority: WO
Inventors: 智樹森尻; 光晴松沢; 伊澤　弘行; 田中　勝; 松田　和也
Original assignee: 日立化成株式会社
Priority date: 2017-03-29
Filing date: 2018-03-28
Publication date: 2018-10-04
Also published as: KR20190133023A; KR102596306B1; JP7341886B2; CN110494930B; JPWO2018181546A1; CN110494930A; TW201841169A; CN113823459A; JP2022173198A

Abstract

The present disclosure relates to a conductive particle sorting method. The sorting method comprises: a step for determining whether a metal that constitutes an outermost layer of a conductive particle satisfies the following first condition; and a step for determining whether the conductive particle satisfies the following second condition. A conductive particle that satisfies both the first condition and the second condition is determined to be good. First Condition: electrical conductivity at 20°C is 40×106 S/m or less. Second Condition: volume specific resistance during application of a 2 kN load is 15 mΩcm or less.

Description

Selection method of conductive particles, circuit connection material, connection structure and manufacturing method thereof, and conductive particles

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

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

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

Patent Document 1 discloses a method for producing conductive fine particles which have base material fine particles and a conductive film formed on the surface thereof, and the conductive film has protrusions protruding 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 substrate 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 surface of the electrode and the conductive particles can be sufficiently eliminated when the member to be connected between the electrodes, and the connection resistance is reduced. It is supposed to be possible.

Patent Document 3 discloses conductive particles having resin particles, an electroless metal plating layer covering the surface thereof, and a metal sputter layer excluding Au forming the outermost layer. According to this document, by coating the surface of the resin particles with electroless metal plating, the adhesion with the surface of the resin particles is improved, and by using the outermost layer as a metal sputter layer, good connection reliability can be obtained. It is said that.

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

By the way, conventionally, regarding the conductive particles used in the manufacturing process of the display or the anisotropic conductive film including the conductive particles, panel manufacturers have selected and used a variety of materials suitable for the electrode surface material. For example, since titanium oxide is formed on the outermost surface of a circuit used for organic EL displays and the like, titanium oxide is formed on the outermost surface, so that conductive particles having a harder plating layer than conventional ones are used. The Thereby, at the time of pressure bonding, the conductive particles pass through the outermost non-conductive film and come into contact with the conductor portion inside the electrode, thereby realizing low resistance. However, when the conductive particles improved by such a physical technique are applied to, for example, an electrode of an ITO film, there is a problem that the conductive particles before the improvement are less versatile, for example, the resistance may be lower. there were.

Recently, with the rapid commoditization of display related products, competition among panel manufacturers is intensifying. Some panel manufacturers are trying to unify anisotropic conductive film varieties in order to improve cost competitiveness. However, for the following reasons, it is difficult to unify the types of anisotropic conductive films.

First, the electrode circuit of the liquid crystal display and the organic EL display is not uniform. For example, in an LCD, 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 composed of a metal such as titanium, chromium, aluminum, or tantalum is mainly used. In some cases, the electrode surface is coated with an organic material such as acrylic resin or an inorganic material such as SiNx or SiOx for the purpose of protecting the electrode portion or providing high reliability. Furthermore, as electrode circuits other than the display substrate, there are FPC (Flexible Printed Circuit), IC (Integrated Circuit), etc., and various metals such as gold, copper, nickel and the like are used for these electrodes.

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

The present disclosure relates to a method for sorting conductive particles. The screening method includes a step of determining whether or not the metal constituting the outermost layer of the conductive particles satisfies the following first condition, and determines whether or not the conductive particles satisfy the following second condition A conductive particle satisfying both the first condition and the second condition is determined to be good.
First condition: electric conductivity at 20 ° C. of 40 × 10 ⁶ S / m or less Second condition: volume resistivity when load 2 kN is applied is 15 mΩcm or less

By adopting conductive particles that satisfy both the first condition and the second condition, for circuit electrodes with various surface compositions (such as oxide-based transparent conductive films such as ITO and metal electrodes such as Ti) The resistance of the contact interface between the conductive particles and the electrode surface can be lowered, 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 presumed to be a state in which the conductive particles are hardly flat. Therefore, it is considered that the resistance value on the surface of the conductive particles can be detected with higher sensitivity than when the load is large. In an actual connection portion, conductive particles having different flatness ratios are mixed between a pair of facing electrodes due to variations in the particle diameter of the conductive particles or fine irregularities on the electrode surface. That is, some of these conductive particles are not flattened. As described above, even if the conductive particles selected by the method according to the present disclosure have a small flatness, the contribution to the reduction in resistance of the connection portion is large, and a good connection resistance as a whole can be obtained. On the other hand, the conductive particles that do not satisfy one of the first and second conditions have a small contribution to the reduction of the resistance of the connection portion if they are slightly flat. Note that “opposing” in the present specification means that a pair of members are facing each other.

According to the present disclosure, there is provided a method for selecting conductive particles having sufficiently high versatility for circuit electrodes included in circuit members to be connected. Moreover, according to this indication, a conductive particle, a circuit connection material using the same, a connection structure, and a manufacturing method thereof are provided.

FIG. 1A is a schematic cross-sectional view showing an enlarged connection portion of a connection structure manufactured using conductive particles selected by the method according to the present disclosure, and FIG. It is a schematic cross section which expands and shows the connection part of the connection structure manufactured using the electrically-conductive particle which does not satisfy | fill either one of 2nd conditions. FIG. 2 is a graph showing an example of the measurement result of the volume resistivity. FIG. 3A to FIG. 3C are cross-sectional views schematically showing 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.

<Selection method of conductive particles>
In the method for sorting conductive particles according to the present embodiment, the step of determining whether or not the metal constituting the outermost layer of the conductive particles satisfies the following first condition, and the conductive particles satisfy the following second condition: A step of determining whether or not the condition is satisfied, and determining that the conductive particles satisfying both the first condition and the second condition are good.
First condition: electric conductivity at 20 ° C. of 40 × 10 ⁶ S / m or less Second condition: volume resistivity when load 2 kN is applied is 15 mΩcm or less

By adopting conductive particles that satisfy both the first condition and the second condition, for circuit electrodes with various surface compositions (such as oxide-based transparent conductive films such as ITO and metal electrodes such as Ti) The resistance of the contact interface between the conductive particles and the electrode surface can be lowered, and a good connection resistance can be obtained.

FIG. 1A is a schematic cross-sectional view showing an enlarged connection portion of a connection structure manufactured using 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 an enlarged 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. 1 (a), at the connection portion of the connection structure 10, due to the variation in the particle size of the conductive particles 1, between the

circuit electrodes

3a and 4a included in the pair of

circuit members

3 and 4 facing each other. Are mixed with conductive particles 1 having different flatness ratios. As schematically shown in FIG. 1A, among the three

conductive particles

1a, 1b, 1a, the two

conductive particles

1a, 1a are hardly flat. Even when the conductive particles 1 (

conductive particles

1a and 1b) are slightly flat, since the contribution to the reduction of the resistance of the connection portion is large, a good connection resistance as a whole can be obtained. On the other hand, the conductive particles 2 (2a, 2b) shown in FIG. 1 (b) have a small contribution to the reduction in resistance of the connection portion when they are slightly flat. Here, the case where conductive particles having different flatness ratios are mixed due to the variation in the particle size of the conductive particles is exemplified, but the surface of the

circuit electrodes

3a and 4a is obtained even when the particle size of the conductive particles is sufficiently uniform. The degree of flatness of the conductive particles can vary depending on the unevenness.

The electrical conductivity of the outermost metal layer according to the first condition can be measured using, for example, a conductivity meter (device name: SIGMATEST, manufactured by Nippon Felster Co., Ltd.). However, conductive particles are generally very small and are difficult to measure with the same apparatus. Therefore, instead of actually measuring the electrical conductivity using such an apparatus, the element constituting the outermost layer may be analyzed and the electrical 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 (electrical conductivity at 20 ° C. of the metal layer) may be set to 1 × 10 ⁶ to 40 × 10 ⁶ S / m. 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 measurement system (device name: PD51, manufactured by Mitsubishi Chemical Analytech Co., Ltd.). Specifically, 2.5 g of conductive particles are charged into a dedicated cell of the device, and the volume resistivity of the conductive particles when a load of 2 kN is applied using the device can be measured. Note that the amount of the conductive particles to be charged may be 0.5 g or more because it is sufficient that the bottom surface 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 specific resistance when a load of 2 kN is applied) may be 10 mΩcm or less. 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 compression characteristics, 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 have to cover the entire surface of the core particle, and may be an embodiment in which a part of the surface of the core particle is covered with the metal layer. The metal layer may have a single layer structure or a multilayer structure.

The particle size of the conductive particles is generally smaller than the minimum value of the distance between the electrodes of the connected circuit members. When there is variation in the height of the electrodes to be connected, the average particle diameter of the conductive particles is preferably larger than the variation in height. From this viewpoint, the average particle diameter of the conductive particles is preferably 1 to 50 μm, more preferably 1 to 20 μm, still more preferably 2 to 10 μm, and particularly preferably 2 to 6 μm. As used herein, “average particle diameter” means a value obtained by observation with a differential scanning electron microscope. That is, one particle is arbitrarily selected, and this is observed with a differential scanning electron microscope to measure the maximum diameter and the minimum diameter. The square root of the product of the maximum diameter and the minimum diameter is defined as the particle diameter of the particle. By this method, the particle diameter of 50 arbitrarily selected particles is measured, and the average value thereof is taken to obtain the average particle diameter of the particles.

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

The compression elastic modulus (20% K value) of the conductive particles when 20% compression displacement is performed at 25 ° C. (20% compression) 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 electrodes facing each other are connected. As a result, it is easy to secure a contact area between the connection reliability and the connection reliability.

The 20% K value of the conductive particles is determined by the following method using a Fischer scope H100C (manufactured by Fischer Instrument). One conductive particle spread on the 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 obtained from this curve. Specifically, when the load F (N), the displacement S (mm), the particle radius R (mm), the elastic modulus E (Pa), and the Poisson's ratio σ, the compression formula of the elastic sphere F = (2 ^{1 / ^{2/3) × (S 3/2}} ) × (E × R 1/2) / (1-σ 2) using the following equation K = E / (1-σ 2) = (3/2 1 / ² ) × F × (S ^−3/2 ) × (R ^−1/2 ). Further, assuming that the deformation rate X (%) and the sphere diameter 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 formula: X = (S / D) × 100. The maximum test load in the compression test is set to 50 mN, for example.

(Core particles)
As described above, the conductive particles in the present embodiment are core-shell type particles and include core particles. Because the conductive particles have core particles, the range of physical property design of the conductive particles themselves is greatly expanded, and the size uniformity of the conductive particles is improved compared to metal powders, etc. It becomes easy to optimize 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. From at least one resin selected from the group consisting of resins, polyvinyl butyral resins, rosin resins, terpene resins, phenol resins, guanamine resins, melamine resins, oxazoline resins, carbodiimide resins, silicone resins, etc. What is formed is mentioned. The plastic particles may be a composite of these resins and an inorganic material such as silica.

As plastic particles, from the viewpoint of ease of control of compression recovery rate and compression hardness K value, plastic particles made of a resin obtained by polymerizing one kind of 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 two or more kinds of polymerizable monomers having an ethylenically unsaturated group are copolymerized to obtain a resin, in combination with a non-crosslinkable monomer and a crosslinkable monomer, 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 No. 2004-165019 can be used.

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

(Metal layer)
In the present embodiment, the outermost layer of the conductive particles is composed 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. In addition, the outermost layer here 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 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 (a mode in which an Au layer is provided on the Ni layer, the same applies hereinafter), Ni / Pd, Ni / W, Cu, and NiB. Preferably it is formed from. The metal layer is formed by a general method such as plating, vapor deposition, or sputtering, and may be a thin film. In addition, when forming a metal layer by plating with respect to a plastic particle, it is preferable that a metal layer contains Ni, Pd, or W from a viewpoint of the plating property with respect to a plastic. Furthermore, it is preferable to eliminate the resin between the electrode and the particles at the time of pressure bonding, and a lower resistance can be obtained, so that the metal layer preferably contains Ni. In addition to being excellent in resin exclusion at the time of press bonding, Ni is superior in plating and corrosion resistance compared to Au, Cu and Ag, which have high electrical conductivity, and also in terms of supply stability and price. There are advantages.

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

Conductive particles are formed by attaching an insulating material layer (eg, organic film) or insulating fine particles (eg, organic fine particles or inorganic fine particles) to the outside of the metal layer from the viewpoint of improving insulation between adjacent electrodes. You may have an adhesion layer. The thickness of the adhesion layer is preferably about 50 to 1000 nm. In addition, it is preferable to form the adhesion layer with respect to the 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 protrusions on the surface. By having protrusions on the metal layer, it is possible to eliminate the resin at the time of crimping, to increase the number of contact points with the electrode, and to further contact the inside of the electrode 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 together and electrically connecting circuit electrodes (for example, connection terminals) included in each circuit member. The circuit connecting 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. .

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

The compounding amount of the adhesive component is a circuit connecting material from the viewpoint of maintaining the gap between the electrodes at the time of circuit connection and after connection, and ensuring the strength and elasticity necessary for providing excellent connection reliability. When the total mass is 100 parts by mass, it is 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 an epoxy resin latent curing agent (hereinafter referred to as “first composition”), a radical polymerizable substance and a free radical by heating. A composition containing a curing agent that generates water (hereinafter, “second composition”), or a mixed composition of the first composition and the second composition is preferable.

The epoxy resin contained in the first composition is bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol A novolac type epoxy resin, bisphenol. Examples thereof include F novolac type epoxy resins, alicyclic epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, hydantoin type epoxy resins, isocyanurate type epoxy resins, and aliphatic chain epoxy resins. These epoxy resins may be halogenated or hydrogenated. Two or more of these epoxy resins may be used in combination.

The latent curing agent contained in the first composition is not particularly limited as long as it can cure the epoxy resin. Examples of such latent curing agents include anionic polymerizable catalyst-type curing agents and cationic polymerizable agents. Catalyst-type curing agents, polyaddition-type curing agents, and the like. These can be used alone or as a mixture of two or more. Of these, anionic or cationic polymerizable catalyst-type curing agents are preferred because they are excellent in rapid curability and do not require chemical equivalent considerations.

Examples of the anionic or cationic polymerizable catalyst-type curing agent include imidazole curing agent, hydrazide curing agent, boron trifluoride-amine complex, sulfonium salt, amine imide, diaminomaleonitrile, melamine and its derivatives, polyamine salt, dicyandiamide These modifications 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 anionically polymerizable catalyst-type curing agent, the epoxy resin is cured by heating at a medium temperature of about 160 ° C. to 200 ° C. for several tens of seconds to several hours. For this reason, pot life (pot life) can be made relatively long. As the cationic polymerizable catalyst-type curing agent, for example, photosensitive onium salts (such as aromatic diazonium salts and aromatic sulfonium salts) that cure the epoxy resin by energy ray irradiation are preferable. In addition to irradiation with energy rays, there are aliphatic sulfonium salts and the like that are activated by heating to cure the epoxy resin. This type of curing agent is preferable because it has a feature of fast curing.

When these latent hardeners are coated with polymer materials such as polyurethane and polyester, metal thin films such as nickel and copper, and inorganic materials such as calcium silicate, the pot life is extended. This is preferable because it is possible. The blending amount of the latent curing agent contained in the first composition is preferably 20 to 80 parts by mass with respect to 100 parts by mass in total of the epoxy resin and the film forming material to be blended if necessary, and preferably 30 to 70 parts by mass. Part by mass is more preferable.

The radical polymerizable substance contained in the second composition is a substance having a functional group that is polymerized by radicals. Examples of such radically polymerizable substances include acrylate (including corresponding methacrylates; the same shall apply hereinafter) compounds, acryloxy (including corresponding methacryloxy; the same shall apply hereinafter) compounds, maleimide compounds, citraconic imide resins, nadiimide resins, and the like. It is done. The radically polymerizable substance may be used in a monomer or oligomer state, and the monomer and oligomer may be used in combination. Specific examples of the acrylate compound include methyl acrylate, ethyl acrylate, isopropyl acrylate, isobutyl acrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, trimethylolpropane triacrylate, tetramethylolmethane 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 admixture of two or more. Moreover, you may use suitably polymerization inhibitors, such as hydroquinone and methyl ether hydroquinone, as needed. Furthermore, 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 International Publication No. 2009/063827 can be preferably used. These are used individually by 1 type or in combination of 2 or more types.

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

[Wherein n represents an integer of 1 to 3. ]

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

The blending amount of the radically polymerizable substance having a phosphate ester structure represented by the above formula (I) is 0.01 to 50 with respect to 100 parts by mass in total of the radically polymerizable substance and the film forming material to be blended if necessary. The amount is preferably part by mass, and more preferably 0.5 to 5 parts by mass.

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

The curing agent that generates a free radical by heating, which is contained in the second composition, is a curing agent that decomposes by heating to generate a free radical. 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 viewpoint of high reactivity and improvement in pot life, organic peroxides having a half-life of 10 hours at a temperature of 40 ° C. or more and a half-life of 1 minute at a temperature of 180 ° C. or less are preferred. An organic peroxide having a temperature of 60 ° C. or higher and a half-life of 1 minute is 170 ° C. or lower is more preferable.

When the connection time is 25 seconds or less, the amount of the curing agent is 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 blended as necessary. The amount is preferably 4 to 8 parts by mass. Thereby, sufficient reaction rate can be obtained. When the connection time is not limited, the compounding amount of the curing agent is 0.05 to 20 parts by mass with respect to 100 parts by mass in total of the radical polymerizable substance and the film forming material to be blended as necessary. The amount is preferably 0.1 to 10 parts by mass.

Specific examples of curing agents that generate free radicals upon heating contained in the second composition are diacyl peroxide, peroxydicarbonate, peroxyester peroxyketal, dialkyl peroxide, hydroperoxide, silyl peroxide. Etc. Further, from the viewpoint of suppressing the corrosion of the circuit electrode, a curing agent having a concentration of chlorine ions and organic acid of 5000 ppm or less is preferable, and a curing agent with less organic acid generated after thermal decomposition is more preferable. Specific examples of such curing agents include peroxyesters, dialkyl peroxides, hydroperoxides, silyl peroxides, and the like, and curing agents selected from peroxyesters that provide high reactivity are more preferable. In addition, the said hardening | curing agent can be mixed and used suitably.

Peroxyesters include cumylperoxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, 1-cyclohexyl-1-methylethylperoxyneodecanoate, and t-hexyl. Peroxyneodecanodate, t-butyl peroxypivalate, 1,1,3,3-tetramethylbutylperoxy 2-ethylhexanate, 2,5-dimethyl-2,5-di (2-ethyl) Hexanoylperoxy) hexane, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanate , T-butylperoxyisobutyrate, 1,1-bis (t-butylperoxy) cyclohexane, -Hexylperoxyisopropyl monocarbonate, t-butylperoxy-3,5,5-trimethylhexanonate, t-butylperoxylaurate, 2,5-dimethyl-2,5-di (m-toluoyl par Oxy) hexane, t-butyl peroxyisopropyl monocarbonate, t-butyl peroxy-2-ethylhexyl monocarbonate, t-hexyl peroxybenzoate, t-butyl peroxyacetate and the like. As the curing agent that generates free radicals by heating other than the peroxyester, for example, the compounds described in International Publication No. 2009/063827 can be suitably used. These are used individually by 1 type or in combination of 2 or more types.

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

In the circuit connection material of this embodiment, a film forming material may be added as necessary. Film-forming material means that when a liquid material is solidified and the composition composition is made into a film shape, it is easy to handle the film in a normal state (normal temperature and normal pressure), and does not easily tear, break or stick. Mechanical properties and the like are imparted to the film. Examples of the film forming material include phenoxy resin, polyvinyl formal resin, polystyrene resin, polyvinyl butyral resin, polyester resin, polyamide resin, xylene resin, polyurethane resin and the like. Among these, a phenoxy resin is preferable because of excellent adhesiveness, compatibility, heat resistance, and mechanical strength.

The phenoxy resin is a resin obtained by reacting a bifunctional phenol and epihalohydrin until they are polymerized, or by polyaddition of a bifunctional epoxy resin and a bifunctional phenol. The phenoxy resin is prepared by reacting, for example, 1 mol of a bifunctional phenol and 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 a phenoxy resin, from the viewpoint of the mechanical properties and thermal properties of the resin, the mixing equivalent ratio of the bifunctional epoxy resin and the bifunctional phenols is particularly preferably epoxy group / phenol hydroxyl group = 1 / 0.9˜ 1/1, organic amides, ethers, ketones, lactones, alcohols, etc. having a boiling point of 120 ° C. or higher in the presence of catalysts such as alkali metal compounds, organophosphorus compounds, cyclic amine compounds, etc. What was obtained by carrying out polyaddition reaction by heating to 50 to 200 ° C. under the condition that the reaction solid content is 50% by mass or less in a solvent is preferable. You may use a phenoxy resin individually or in mixture of 2 or more types.

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

The blending amount of the film forming material is preferably 10 to 90 parts by mass, and 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 this embodiment may further contain a polymer or copolymer containing at least one of acrylic acid, acrylic acid ester, methacrylic acid ester, and acrylonitrile as a monomer component. Here, since it is excellent in stress relaxation, it is preferable that the circuit connection material includes a glycidyl acrylate-containing copolymer and / or a copolymer acrylic rubber containing glycidyl methacrylate. 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 fine rubber particles, fillers, softeners, accelerators, anti-aging agents, colorants, flame retardants, thixotropic agents, coupling agents, phenol resins, melamine resins, isocyanates. Etc. can also be contained.

The rubber fine particles have an average particle size 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.) of the conductive particles and the adhesive composition at room temperature. It is preferable that it is less than 1/2 of the rate. 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 in combination of two or more. These three-dimensionally crosslinked rubber fine particles are excellent in solvent resistance and are easily dispersed in the adhesive composition.

The filler can improve the connection reliability of the electrical characteristics between the circuit electrodes. As the filler, for example, those having an average particle size of ½ or less of the average particle size of the conductive particles can be suitably used. Moreover, when using together the particle | grains which do not have electroconductivity, if it is below the average particle diameter of the particle | grains which do not have electroconductivity, it can be used. The blending amount of the filler is preferably 5 to 60 parts by mass with respect to 100 parts by mass of the adhesive composition. When the blending amount is 60 parts by mass or less, there is a tendency that the effect of improving the connection reliability can be obtained more sufficiently, and when it is 5 parts by mass or more, there is a tendency that the effect of adding the filler can 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 the connection of the opposing circuit electrodes, and then hardens to maintain the connection. The fluidity of the circuit connection material is an important factor. As an index indicating this, for example, the following can be cited. 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 heating and pressurization are performed under conditions of 170 ° C., 2 MPa, 10 seconds The value of fluidity (B) / (A) expressed using the area (A) of the main surface of the circuit connecting material before heating and pressing and the area (B) of the main surface after heating and pressing is 1. It is preferably from 3 to 3.0, more preferably from 1.5 to 2.5. If it is 1.3 or more, the fluidity is suitable, and it tends to be easy to obtain a good connection, and if it is 3.0 or less, bubbles tend not to be 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, and 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 this embodiment is 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. It is suitably used for (Chip on Polymer) connection, COF (Chip on Flex) connection, and the like.

COG connection is, for example, a method of connecting an IC to an organic EL panel or an LCD panel, and a circuit electrode formed on the IC and a circuit electrode formed on a glass substrate constituting the organic EL panel or 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, typified 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 LCD panel, as typified by 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, typified by TCP, COF, and FPC, for example. FOP connection refers to 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 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 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 this embodiment includes 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 connecting portion made of a cured product of the above-described circuit connecting material. In the present embodiment, circuit electrode materials include 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 100 to 5000 nm, and more preferably 100 to 2500 nm, from the viewpoint of balancing connection resistance and price. 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 the first circuit electrode and the 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 arranged to face each other, and heated and pressurized to thereby form the first circuit electrode and the second circuit electrode. Are electrically connected to each other. Thus, the circuit connection material of this embodiment is useful as a material for bonding electrical circuits.

More specifically, examples of the circuit member include chip parts 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. By arranging at least a part of the circuit electrodes to face each other, interposing a circuit connecting material between the circuit electrodes arranged to face each other, and heating and pressing at least one set of circuit members, the circuit electrodes arranged to face each other can be electrically connected to each other. Connecting. At this time, the circuit electrodes arranged opposite to each other are electrically connected through conductive particles contained in the circuit connection material, while insulation between adjacent circuit electrodes is maintained. Thus, the circuit connection material of this embodiment exhibits anisotropic conductivity.

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

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 provided. prepare. And the circuit connection material 5 shape | molded by the film form is mounted on the circuit electrode 21a.

Next, as shown in FIG. 3B, the substrate 31 on which the circuit electrode 31a is provided is aligned on the circuit connection material 5 while positioning the circuit electrode 21a and the circuit electrode 31a so as to face each other. The circuit connection 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 connection material 5 can be easily interposed between the circuit electrode 21a and the circuit electrode 31a, and the connection work between the circuit member 20 and the circuit member 30 can be facilitated.

Next, the circuit connection material 5 is pressed in the direction of the arrow A in FIG. 3B through the organic EL panel 21 and the substrate 31 while being heated 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 a method for the curing treatment, one or both of heating and light irradiation can be employed depending on the adhesive composition to be 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. The electrical conductivity of nickel is 14.5 × 10 ⁶ S / m. Of the conductive particles A to K, the conductive particles A to E and the conductive particles H and J satisfy both the first and second conditions.

<Example 1>
(2) Production of anisotropic conductive film (Preparation of phenoxy resin solution)
50 g of 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) to obtain a phenoxy resin having a solid content of 40% by mass. It was set as the solution.

(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), 2-hydroxy A reaction solution 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-based catalyst. To the reaction liquid heated to 70 ° C., 666 parts by mass of isophorone diisocyanate (IPDI) was uniformly dropped over 3 hours to be reacted. After completion of the dropwise addition, the reaction was continued for 15 hours, and the time when NCO% (NCO content) became 0.2% by mass or less was regarded as the completion of the reaction, and urethane acrylate was obtained. NCO% was confirmed by a potentiometric automatic 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 8500 (standard polystyrene conversion value). Table 2 shows the GPC measurement conditions.

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

(Production of anisotropic conductive film)
5 parts by mass of conductive particles A were dispersed with respect to 100 parts by mass of the adhesive composition-containing liquid to prepare a circuit connection material-containing liquid. This circuit connecting material-containing liquid was applied onto a 50 μm-thick polyethylene terephthalate (PET) film having a surface treated on one side, and then dried with hot air at 70 ° C. for 3 minutes. Thereby, 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 (film thickness 50 nm) and aluminum (film thickness 250 nm) in this order. did. The transfer conditions were 70 ° C. and 1 MPa for 2 seconds. After peeling off the PET film, a flexible circuit board (FPC) having 600 tin-plated copper circuits with a pitch of 50 μm and a thickness of 8 μm was temporarily fixed on the anisotropic conductive film. Temporary fixing was performed at 24 ° C. and 0.5 MPa for 1 second. Next, this is installed in the main pressure bonding apparatus, and a 200 μm-thick silicone rubber sheet is used as a cushioning material. From the FPC side, heat and pressure are applied with a heat tool at 170 ° C. and 3 MPa for 6 seconds to connect over a width of 1.5 mm. did. Thereby, a connection structure was obtained.

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

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

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

<Examples 2 to 5 and Comparative Examples 1 and 2>
Three types of connection structures were prepared in the same manner as in Example 1 except that the conductive particles B to K were used instead of the conductive particles A, and their connection resistances were measured. Table 3 shows the results.

DESCRIPTION OF

SYMBOLS

1, 1a, 1b ... Conductive particle, 3, 4, 20, 30 ... Circuit member, 3a, 4a, 21a, 31a ... Circuit electrode, 5 ... Circuit connection material, 5a ... Hardened | cured material of circuit connection material, 10, 50 ... Connection structure

Claims

A method for sorting conductive particles,
Determining whether the metal constituting the outermost layer of the conductive particles satisfies the following first condition;
Determining whether the conductive particles satisfy the following second condition;
Including
A method for selecting conductive particles, wherein the conductive particles satisfying both the first condition and the second condition are determined to be good.
First condition: electric conductivity at 20 ° C. of 40 × 10 6 S / m or less Second condition: volume resistivity when load 2 kN is applied is 15 mΩcm or less
A circuit connecting material used for bonding circuit members together and electrically connecting circuit electrodes of each circuit member,
An adhesive component that is cured by light or heat;
Conductive particles dispersed in the adhesive component;
Including
The circuit connection material, wherein the conductive particles are conductive particles determined to be good by the conductive particle sorting method according to claim 1.
The circuit connection material according to claim 2, which is formed in a film shape.
The circuit connection material according to claim 2 or 3, wherein the connection is a COG connection, an FOB connection, an FOG connection, an FOF connection, an 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 disposed opposite to each other;
The circuit members are bonded to each other so that the circuit electrodes of the circuit members are electrically connected to each other by being interposed between the pair of circuit members by heating and pressing. Forming a connecting portion to be
A method for manufacturing a connection structure including:
A pair of circuit members disposed opposite to each other;
A circuit connection material according to any one of claims 2 to 4, wherein the circuit electrodes are interposed between the pair of circuit members and are electrically connected to each other. A connecting portion for bonding the circuit members together;
A connection structure comprising:
A metal layer having an electrical 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 contains Ni.
It further comprises core particles made of a resin material,
The conductive particle according to claim 7 or 8, wherein the metal layer is formed on a surface of the core particle.
The conductive particle according to any one of claims 7 to 9, wherein the metal layer has a protrusion.
The conductive particles according to any one of claims 7 to 10, further comprising an organic film, organic fine particles, or inorganic fine particles disposed on the surface of the metal layer.
The conductive particles according to any one of claims 7 to 11, having an average particle diameter of 1 to 50 µm.
The conductive particles according to any one of claims 7 to 12, wherein the elastic modulus at 20% compression is 0.1 to 15 GPa.