JP7352353B2 - Conductive materials and connected structures - Google Patents

Description

The present invention relates to a conductive material including conductive particles having solder on the outer surface of a conductive part. The present invention also relates to a connected structure using the above-mentioned conductive material.

Anisotropic conductive materials such as anisotropic conductive pastes and anisotropic conductive films are widely known. In the above anisotropic conductive material, conductive particles are dispersed in a binder.

The above-mentioned anisotropic conductive material is used to obtain various connected structures. Examples of connections using the anisotropic conductive material include connections between flexible printed circuit boards and glass substrates (FOG (Film on Glass)), connections between semiconductor chips and flexible printed circuit boards (COF (Chip on Film)), and semiconductor Examples include connection between a chip and a glass substrate (COG (Chip on Glass)), connection between a flexible printed circuit board and a glass epoxy substrate (FOB (Film on Board)), and the like.

For example, when electrically connecting the electrodes of a flexible printed circuit board and the electrodes of a glass epoxy board using the anisotropic conductive material, the anisotropic conductive material containing conductive particles is placed on the glass epoxy board. do. Next, flexible printed circuit boards are laminated and heated and pressurized. Thereby, the anisotropic conductive material is cured, the electrodes are electrically connected via the conductive particles, and a connected structure is obtained.

As an example of the above-mentioned anisotropic conductive material, Patent Document 1 below discloses an anisotropic conductive material containing conductive particles and a resin component whose curing is not completed at the melting point of the conductive particles. Specifically, the conductive particles include tin (Sn), indium (In), bismuth (Bi), copper (Cu), zinc (Zn), lead (Pb), cadmium (Cd), and gallium (Ga). ), silver (Ag), thallium (Tl), and alloys of these metals.

Patent Document 1 discloses a resin heating step of heating an anisotropic conductive material to a temperature higher than the melting point of the conductive particles and at which curing of the resin component is not completed, and a resin component curing step of curing the resin component. It is described that the electrodes are electrically connected through. Furthermore, Patent Document 1 describes that mounting is performed using the temperature profile shown in FIG. 8 of Patent Document 1. In Patent Document 1, conductive particles are melted within a resin component that is not completely cured at the temperature at which the anisotropic conductive material is heated.

Further, Patent Document 2 below discloses a solder paste (conductive material) containing flux and alloy powder whose main component is tin. The above flux is a flux in which an activator is added and dispersed in a solvent. The above solvent is a polyhydric alcohol having 2 to 4 hydroxyl groups. The above active agent is a saccharide having 4 to 6 hydroxyl groups. The average particle diameter of the activator is 100 μm or less.

Further, Patent Document 3 below discloses a solder composition (conductive material) containing a lead-free SnZn-based alloy and a soldering flux. The soldering flux includes an epoxy resin and an organic carboxylic acid. The organic carboxylic acid is dispersed as a solid in the solder composition at room temperature (25° C.).

Japanese Patent Application Publication No. 2004-260131 Japanese Patent Application Publication No. 2007-216296 WO2003/002290A1

In conventional conductive materials such as those described in Patent Documents 1 to 3, the movement speed of conductive particles or solder particles onto the electrode (line) is slow, and it is difficult to efficiently aggregate the solder between the upper and lower electrodes to be connected. It may be difficult to do so. As a result, the reliability of conduction between the electrodes and the reliability of insulation tend to decrease.

Examples of a method for efficiently agglomerating solder on an electrode include a method of increasing the amount of flux mixed in the conductive material.

However, when the content of flux in the conductive material is increased, the flux and the thermosetting compound in the conductive material may react, resulting in a decrease in the storage stability of the conductive material. Furthermore, when the content of flux in the conductive material is increased, the heat resistance of the cured product of the conductive material may decrease.

Conventional conductive materials such as those described in Patent Documents 1 to 3 have the following objectives: increasing the storage stability of the conductive material, increasing the cohesiveness of the solder during conductive connection, and increasing the heat resistance of the cured product. , it is difficult to satisfy all these requirements.

The purpose of the present invention is to effectively increase the storage stability of conductive materials, effectively increase the cohesiveness of solder during conductive connections, and furthermore effectively increase the heat resistance of cured products. The object of the present invention is to provide a conductive material that can be used. Another object of the present invention is to provide a connected structure using the above conductive material.

According to a broad aspect of the present invention, the conductive portion includes a plurality of conductive particles having solder on the outer surface portion, a thermosetting compound, and a flux, and has any of the following first configuration and second configuration. A conductive material is provided comprising one or more of the following.

First configuration: There is no flux having a particle size that is twice or more the average particle size of the flux, or the particle size of 100% of the total number of fluxes is twice or more the average particle size of the flux. There are less than 10% of the fluxes with .

Second configuration: The composition obtained by removing the conductive particles from the conductive material is a colloid, and the flux exists as colloid particles.

In a particular aspect of the conductive material according to the present invention, there is no flux having a particle size that is 1.5 times or more the average particle size of the flux, or in 100% of the total number of fluxes, the flux is Less than 20% of the fluxes have a particle size that is 1.5 times or more the average particle size.

In a particular aspect of the conductive material according to the present invention, the average particle size of the flux is 1 μm or less.

In a particular aspect of the conductive material according to the present invention, the content of the flux is 1 part by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the thermosetting compound.

In a particular aspect of the conductive material according to the present invention, the content of the flux is 0.05% by weight or more and 20% by weight or less based on 100% by weight of the conductive material.

In a particular aspect of the conductive material according to the present invention, the conductive material is a conductive paste.

According to a broad aspect of the present invention, a first connection target member having a first electrode on its surface, a second connection target member having a second electrode on its surface, and the first connection target member, a connecting portion connecting the second connection target member, the material of the connecting portion is the above-mentioned conductive material, and the first electrode and the second electrode are connected to the connecting portion. A connection structure is provided that is electrically connected by a solder portion therein.

In a particular aspect of the connection structure according to the present invention, the first electrode and the second electrode may face each other in a stacking direction of the first electrode, the connection portion, and the second electrode. When looking at the portion, the solder portion in the connection portion is disposed on 50% or more of the 100% area of the portion where the first electrode and the second electrode face each other.

The conductive material according to the present invention includes a plurality of conductive particles having solder on the outer surface portion of the conductive part, a thermosetting compound, and a flux, and has either the first configuration or the second configuration. 1 or more. Since the conductive material according to the present invention has the above configuration, the storage stability of the conductive material can be effectively increased, and the cohesiveness of the solder during conductive connection can be effectively increased. Furthermore, the heat resistance of the cured product can be effectively improved.

FIG. 1 is a cross-sectional view schematically showing a connected structure obtained using a conductive material according to an embodiment of the present invention. FIGS. 2(a) to 2(c) are cross-sectional views for explaining each step of an example of a method for manufacturing a connected structure using a conductive material according to an embodiment of the present invention. FIG. 3 is a sectional view showing a modification of the connected structure. FIG. 4 is a cross-sectional view showing a first example of conductive particles that can be used in a conductive material. FIG. 5 is a cross-sectional view showing a second example of conductive particles that can be used in a conductive material. FIG. 6 is a cross-sectional view showing a third example of conductive particles that can be used in a conductive material.

The details of the present invention will be explained below.

(conductive material)
The electrically conductive material according to the present invention includes a plurality of electrically conductive particles having solder on the outer surface of the electrically conductive part, a thermosetting compound, and a flux. The conductive material according to the present invention includes one or more of the following first configuration and second configuration. The conductive material according to the present invention may include only the first configuration below, only the second configuration below, or the first configuration below and the second configuration below. It may have both configurations.

First configuration: There is no flux having a particle size that is twice or more the average particle size of the above flux, or the particle size of 100% of the total number of the above fluxes is twice or more the average particle size of the above flux. There are less than 10% of fluxes with

Second configuration: The composition obtained by removing the conductive particles from the conductive material is a colloid, and the flux exists as colloid particles.

The conductive material according to the present invention may have, as the first configuration, a configuration in which there is no flux having a particle size that is twice or more the average particle size of the flux (configuration 1a). The conductive material according to the present invention has a configuration in which less than 10% of the fluxes having a particle size that is twice or more the average particle size of the flux are present in 100% of the total number of the fluxes (configuration 1b). ).

The conductive material according to the present invention may include only the configuration 1a, only the configuration 1b, only the second configuration, or the 1a configuration. and the second configuration, or may include the configuration 1b and the second configuration.

Since the present invention has the above configuration, it is possible to improve the storage stability of the conductive material, effectively increase the cohesiveness of the solder during conductive connection, and further improve the heat resistance of the cured product. can be effectively increased.

In the present invention, since the above configuration is provided, when the electrodes are electrically connected, a plurality of conductive particles can be efficiently arranged on the electrodes (lines), and the Solder can be efficiently aggregated between the upper and lower electrodes. In addition, some of the plurality of conductive particles are difficult to be placed in areas (spaces) where electrodes are not formed, and the amount of conductive particles placed in areas where electrodes are not formed can be considerably reduced. . Therefore, the reliability of conduction between the electrodes can be improved. Moreover, electrical connection between horizontally adjacent electrodes that should not be connected can be prevented, and insulation reliability can be improved.

Flux is blended into conductive materials mainly to remove oxides present on the surfaces of solder and electrodes in conductive particles, and to prevent the formation of such oxides. In the present invention, the flux is relatively hard to aggregate, and the particle size of the flux is relatively small. Furthermore, in the present invention, the flux is relatively well dispersed. Therefore, in the present invention, even if the content of flux in the conductive material is relatively small, it is possible to remove the oxide present on the solder surface, the electrode surface, etc. in the conductive particle, and the oxide The formation of objects can be prevented. In the present invention, even if the content of flux in the conductive material is relatively small, it is possible to effectively improve the cohesiveness of solder during conductive connection. In the present invention, the content of flux in the conductive material can be made relatively small.

Effectively increasing the cohesiveness of solder during conductive connection when the flux is present in the present invention, compared to the present invention when the flux is not present, when the flux is the same content. I can do it.

In the present invention, the content of flux in the conductive material does not need to be large and can be kept in a relatively small amount, so that the reaction between the thermosetting compound and the flux in the conductive material can be effectively suppressed. I can do it. As a result, the storage stability of the conductive material can be effectively improved.

In addition, the melting point (activation temperature) of flux in a conductive material is often lower than the Tg of the thermosetting compound in the conductive material, and the higher the content of flux in the conductive material, the higher the Heat resistance tends to decrease. In the present invention, the content of flux in the conductive material does not need to be large, and can be kept in a relatively small amount, so that the heat resistance of the cured product of the conductive material can be effectively improved.

Since the present invention has the above-mentioned configuration, it is possible to improve the storage stability of the conductive material, increase the cohesiveness of the solder during conductive connection, and increase the heat resistance of the cured product. All requests can be satisfied.

Furthermore, in the present invention, positional displacement between the electrodes can be prevented. At the time of conductive connection, a second member to be connected is superimposed on a first member to be connected having a conductive material disposed on the upper surface. At this time, even if the first connection target member and the second connection target member are overlapped with the electrodes of the first connection target member and the second connection target member being out of alignment, , the present invention can correct the deviation. As a result, the electrode of the first connection target member and the electrode of the second connection target member can be connected (self-alignment effect).

From the viewpoint of further improving the cohesiveness of the solder, the conductive material is preferably liquid at 25° C., and is preferably a conductive paste.

From the viewpoint of further improving the cohesiveness of the solder, the viscosity (η25) at 25° C. of the conductive material is preferably 20 Pa·s or more, more preferably 30 Pa·s or more, and preferably 500 Pa·s or less, More preferably, it is 300 Pa·s or less. The above viscosity (η25) can be adjusted as appropriate depending on the types and amounts of the ingredients.

The viscosity (η25) can be measured, for example, using an E-type viscometer (“TVE22L” manufactured by Toki Sangyo Co., Ltd.) at 25° C. and 5 rpm.

The above-mentioned conductive material can be used as a conductive paste, a conductive film, and the like. The conductive paste is preferably an anisotropic conductive paste, and the conductive film is preferably an anisotropic conductive film. From the viewpoint of further improving the cohesiveness of the solder, the conductive material is preferably a conductive paste. The above-mentioned conductive material is suitably used for electrical connection of electrodes. Preferably, the conductive material is a circuit connection material.

Each component contained in the conductive material will be explained below. In addition, in this specification, "(meth)acrylic" means one or both of "acrylic" and "methacrylic", and "(meth)acrylate" means one or both of "acrylate" and "methacrylate". means.

(conductive particles)
The conductive particles electrically connect the electrodes of the connection target members. The conductive particles have solder on the outer surface of the conductive part. The conductive particles may be solder particles formed of solder. The solder particles have solder on the outer surface of the conductive part. In the solder particles, both the center portion and the outer surface portion of the conductive portion are formed of solder. The solder particles are particles in which both the center portion and the conductive outer surface are solder. The conductive particles may include a base particle and a conductive part disposed on the surface of the base particle. In this case, the conductive particles have solder on the outer surface of the conductive part.

The conductive particles have solder on the outer surface of the conductive part. The base material particles may be solder particles formed of solder. The conductive particles may be solder particles in which both the base material particle and the outer surface portion of the conductive part are solder.

In addition, compared to the case where the above-mentioned solder particles are used, in the case of using conductive particles comprising a base particle not formed of solder and a solder part arranged on the surface of the base particle, Conductive particles become difficult to collect on the electrode. Furthermore, since the solder bondability between the conductive particles is low, the conductive particles that have moved onto the electrodes tend to easily move out of the electrodes, and the effect of suppressing misalignment between the electrodes also tends to be reduced. Therefore, it is preferable that the conductive particles are solder particles formed of solder.

Next, specific examples of conductive particles will be described with reference to the drawings.

FIG. 4 is a cross-sectional view showing a first example of conductive particles that can be used in a conductive material.

The conductive particles 21 shown in FIG. 4 are solder particles. The conductive particles 21 are entirely made of solder. The conductive particles 21 do not have a base particle in their core and are not core-shell particles. Both the center portion and the outer surface portion of the conductive part of the conductive particles 21 are formed of solder.

FIG. 5 is a cross-sectional view showing a second example of conductive particles that can be used in a conductive material.

The conductive particles 31 shown in FIG. 5 include a base particle 32 and a conductive part 33 disposed on the surface of the base particle 32. The conductive portion 33 covers the surface of the base particle 32. The conductive particles 31 are coated particles in which the surface of a base particle 32 is coated with a conductive part 33 .

The conductive part 33 includes a second conductive part 33A and a solder part 33B (first conductive part). The conductive particles 31 include a second conductive part 33A between the base particle 32 and the solder part 33B. Therefore, the conductive particles 31 include the base particles 32, the second conductive part 33A disposed on the surface of the base particle 32, and the solder part 33B disposed on the outer surface of the second conductive part 33A. Equipped with.

FIG. 6 is a cross-sectional view showing a third example of conductive particles that can be used in a conductive material.

The conductive part 33 of the conductive particle 31 in FIG. 5 has a two-layer structure. The conductive particles 41 shown in FIG. 6 have a solder portion 42 as a single-layer conductive portion. The conductive particles 41 include base particles 32 and solder portions 42 disposed on the surfaces of the base particles 32.

Other details of the conductive particles will be explained below.

(Base material particles)
Examples of the base particles include resin particles, inorganic particles other than metal particles, organic-inorganic hybrid particles, and metal particles. The base particles are preferably base particles excluding metal particles, and more preferably resin particles, inorganic particles excluding metal particles, or organic-inorganic hybrid particles. The base particle may be a core-shell particle including a core and a shell disposed on the surface of the core. The core may be an organic core, and the shell may be an inorganic shell.

The base particles are more preferably resin particles or organic-inorganic hybrid particles, and may be resin particles or organic-inorganic hybrid particles. By using these preferable base particles, the effects of the present invention can be exhibited even more effectively, and conductive particles that are more suitable for electrical connection between electrodes can be obtained.

When connecting between electrodes using the conductive particles, the conductive particles are placed between the electrodes and then compressed by pressure bonding. When the base particles are resin particles or organic-inorganic hybrid particles, the conductive particles are easily deformed during the pressure bonding, and the contact area between the conductive particles and the electrode becomes large. Therefore, the reliability of conduction between the electrodes is further increased.

Various resins are suitably used as materials for the resin particles. Examples of materials for the resin particles include polyolefin resins such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyisobutylene, and polybutadiene; acrylic resins such as polymethyl methacrylate and polymethyl acrylate; polyalkylene terephthalate, and polycarbonate. , polyamide, phenol formaldehyde resin, melamine formaldehyde resin, benzoguanamine formaldehyde resin, urea formaldehyde resin, phenol resin, melamine resin, benzoguanamine resin, urea resin, epoxy resin, unsaturated polyester resin, saturated polyester resin, polysulfone, polyphenylene oxide, polyacetal, Examples include polyimide, polyamideimide, polyetheretherketone, polyethersulfone, and polymers obtained by polymerizing one or more of various polymerizable monomers having ethylenically unsaturated groups.

It is possible to design and synthesize resin particles having arbitrary compression characteristics suitable for conductive materials, and the hardness of the resin particles can be easily controlled within a suitable range. It is preferable that it is a polymer obtained by polymerizing one or more types of polymerizable monomers having a plurality of.

When the resin particles are obtained by polymerizing a polymerizable monomer having an ethylenically unsaturated group, the polymerizable monomer having an ethylenically unsaturated group may be a non-crosslinkable monomer. Examples include crosslinkable monomers.

Examples of the non-crosslinkable monomer include styrene monomers such as styrene and α-methylstyrene; carboxyl group-containing monomers such as (meth)acrylic acid, maleic acid, and maleic anhydride; methyl ( meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, butyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, lauryl(meth)acrylate, cetyl(meth)acrylate, stearyl(meth)acrylate, cyclohexyl( Alkyl (meth)acrylate compounds such as meth)acrylate and isobornyl (meth)acrylate; oxygen atoms such as 2-hydroxyethyl (meth)acrylate, glycerol (meth)acrylate, polyoxyethylene (meth)acrylate, and glycidyl (meth)acrylate Contains (meth)acrylate compounds; nitrile-containing monomers such as (meth)acrylonitrile; acid vinyl ester compounds such as vinyl acetate, vinyl butyrate, vinyl laurate, and vinyl stearate; unsaturated compounds such as ethylene, propylene, isoprene, butadiene, etc. Hydrocarbons include halogen-containing monomers such as trifluoromethyl (meth)acrylate, pentafluoroethyl (meth)acrylate, vinyl chloride, vinyl fluoride, and chlorostyrene.

Examples of the crosslinkable monomer include tetramethylolmethanetetra(meth)acrylate, tetramethylolmethanetri(meth)acrylate, tetramethylolmethanedi(meth)acrylate, trimethylolpropanetri(meth)acrylate, dipenta Erythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, glycerol tri(meth)acrylate, glycerol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate Polyfunctional (meth)acrylate compounds such as acrylate, (poly)tetramethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate; triallyl(iso)cyanurate, triallyl trimellitate, divinylbenzene, Examples include silane-containing monomers such as diallyl phthalate, diallylacrylamide, diallyl ether, γ-(meth)acryloxypropyltrimethoxysilane, trimethoxysilylstyrene, and vinyltrimethoxysilane.

The resin particles can be obtained by polymerizing the polymerizable monomer having an ethylenically unsaturated group by a known method. Examples of this method include a method in which suspension polymerization is carried out in the presence of a radical polymerization initiator, and a method in which monomers are swollen and polymerized together with a radical polymerization initiator using non-crosslinked seed particles.

When the base particles are inorganic particles other than metal particles or organic-inorganic hybrid particles, examples of the inorganic material of the base particles include silica, alumina, barium titanate, zirconia, and carbon black. Preferably, the inorganic substance is not a metal. The particles formed from the above-mentioned silica are not particularly limited, but for example, after hydrolyzing a silicon compound having two or more hydrolyzable alkoxysilyl groups to form crosslinked polymer particles, baking may be performed as necessary. Examples include particles obtained by Examples of the organic-inorganic hybrid particles include organic-inorganic hybrid particles formed from a crosslinked alkoxysilyl polymer and an acrylic resin.

The organic-inorganic hybrid particles are preferably core-shell type organic-inorganic hybrid particles having a core and a shell disposed on the surface of the core. Preferably, the core is an organic core. Preferably, the shell is an inorganic shell. From the viewpoint of further effectively lowering the connection resistance between electrodes, the base particles are preferably organic-inorganic hybrid particles having an organic core and an inorganic shell arranged on the surface of the organic core. .

Examples of the material for the organic core include the materials for the resin particles described above.

Examples of the material for the inorganic shell include the inorganic substances mentioned above as the material for the base particle. The material of the inorganic shell is preferably silica. The inorganic shell is preferably formed by forming a metal alkoxide into a shell-like material by a sol-gel method on the surface of the core, and then firing the shell-like material. Preferably, the metal alkoxide is a silane alkoxide. The inorganic shell is preferably formed of silane alkoxide.

When the base particles are metal particles, examples of the metal that is the material of the metal particles include silver, copper, nickel, silicon, gold, and titanium. However, it is preferable that the base material particles are not metal particles.

The particle diameter of the base particles is preferably 0.5 μm or more, more preferably 1 μm or more, even more preferably 3 μm or more, and preferably 100 μm or less, more preferably 60 μm or less, and still more preferably 50 μm or less. When the particle size of the base particles is equal to or larger than the lower limit, the contact area between the conductive particles and the electrodes increases, so the reliability of conduction between the electrodes becomes even higher, and the connection via the conductive particles increases. The connection resistance between the electrodes can be further effectively reduced. Furthermore, when forming a conductive part on the surface of the base material particles, it becomes difficult to aggregate, and it becomes difficult to form aggregated conductive particles. When the particle size of the base particles is equal to or less than the above upper limit, the conductive particles can be sufficiently compressed, and the connection resistance between electrodes connected via the conductive particles can be lowered even more effectively. can.

It is particularly preferable that the particle diameter of the base material particles is 5 μm or more and 40 μm or less. When the particle diameter of the base particles is within the range of 5 μm or more and 40 μm or less, the distance between the electrodes can be made smaller, and even if the thickness of the conductive part is increased, small conductive particles can be obtained. I can do it.

The particle diameter of the base material particle indicates the diameter when the base material particle is true spherical, and indicates the maximum diameter when the base material particle is not true spherical.

The particle diameter of the base material particles indicates the number average particle diameter. The particle diameter of the base material particles is determined using a particle size distribution measuring device or the like. The particle diameter of the base particles is preferably determined by observing 50 base particles using an electron microscope or an optical microscope and calculating the average value. When measuring the particle diameter of the base particle in the conductive particles, it can be measured, for example, as follows.

The conductive particles are added to "Technovit 4000" manufactured by Kulzer Co., Ltd. so that the content thereof is 30% by weight, and dispersed to prepare an embedded resin for conductive particle inspection. Using an ion milling device ("IM4000" manufactured by Hitachi High Technologies), a cross section of the conductive particles is cut out so as to pass through the center of the conductive particles dispersed in the embedding resin for inspection. Then, using a field emission scanning electron microscope (FE-SEM), the image magnification was set to 25,000 times, 50 conductive particles were randomly selected, and the base material particles of each conductive particle were observed. do. The particle diameter of the base material particle in each conductive particle is measured, and the arithmetic average of the measurements is taken as the particle diameter of the base material particle.

(conductive part)
The method of forming a conductive part on the surface of the base particle and the method of forming a solder part on the surface of the base particle or the surface of the second conductive part are not particularly limited. Examples of the method for forming the conductive part and the solder part include electroless plating, electroplating, physical collision, mechanochemical reaction, physical vapor deposition or physical adsorption, Another method includes a method of coating the surface of the base material particles with metal powder or a paste containing metal powder and a binder. The method for forming the conductive part and the solder part is preferably electroless plating, electroplating, or physical collision. Examples of the physical vapor deposition method include vacuum vapor deposition, ion plating, and ion sputtering. Further, in the method using physical collision, for example, a sheeter composer (manufactured by Tokuju Kosho Co., Ltd.) or the like is used.

The melting point of the base particles is preferably higher than the melting points of the conductive part and the solder part. The melting point of the base particles is preferably higher than 160°C, more preferably higher than 300°C, even more preferably higher than 400°C, particularly preferably higher than 450°C. Note that the melting point of the base particles may be lower than 400°C. The melting point of the base particles may be 160°C or lower. The softening point of the base particles is preferably 260°C or higher. The softening point of the base particles may be less than 260°C.

The conductive particles may have a single layer solder portion. The conductive particles may have multiple layers of conductive parts (solder part, second conductive part). That is, in the above-mentioned conductive particles, two or more layers of conductive parts may be laminated. When the conductive part has two or more layers, it is preferable that the conductive particles have solder on the outer surface of the conductive part.

The solder is preferably a metal having a melting point of 450° C. or lower (low melting point metal). The solder portion is preferably a metal layer (low melting point metal layer) having a melting point of 450° C. or lower. The low melting point metal layer is a layer containing a low melting point metal. The solder in the conductive particles is preferably a metal particle (low melting point metal particle) having a melting point of 450° C. or lower. The low melting point metal particles are particles containing a low melting point metal. The above-mentioned low melting point metal refers to a metal having a melting point of 450° C. or lower. The melting point of the low melting point metal is preferably 300°C or lower, more preferably 160°C or lower. Moreover, it is preferable that the solder in the said electroconductive particle contains tin. The content of tin is preferably 30% by weight or more, more preferably 40% by weight or more, even more preferably in 100% by weight of the metal contained in the solder portion and in the 100% by weight of the metal contained in the solder in the conductive particles. is 70% by weight or more, particularly preferably 90% by weight or more. When the content of tin contained in the solder in the solder part and the conductive particles is equal to or higher than the lower limit, the reliability of conduction between the conductive particles and the electrodes becomes even higher.

The above tin content was measured using a high frequency inductively coupled plasma emission spectrometer ("ICP-AES" manufactured by Horiba Ltd.) or a fluorescent X-ray analyzer ("EDX-800HS" manufactured by Shimadzu Corporation), etc. can be measured.

By using conductive particles having the above-mentioned solder on the outer surface of the conductive part, the solder melts and joins to the electrodes, and the solder creates electrical continuity between the electrodes. For example, since the solder and the electrode tend to make surface contact rather than point contact, the connection resistance becomes low. In addition, by using conductive particles that have solder on the outer surface of the conductive part, the strength of the bond between the solder and the electrode increases, making it even more difficult for the solder to separate from the electrode, effectively improving continuity reliability. It becomes expensive.

The low melting point metal constituting the solder portion and the solder is not particularly limited. The low melting point metal is preferably tin or an alloy containing tin. Examples of the alloy include tin-silver alloy, tin-copper alloy, tin-silver-copper alloy, tin-bismuth alloy, tin-zinc alloy, tin-indium alloy, and the like. The low melting point metal is preferably tin, tin-silver alloy, tin-silver-copper alloy, tin-bismuth alloy, or tin-indium alloy, since they have excellent wettability to the electrode. More preferred are tin-bismuth alloys and tin-indium alloys.

The material constituting the solder (solder part) is preferably a filler metal whose liquidus line is 450° C. or less based on JIS Z3001: Welding terminology. Examples of the composition of the solder include metal compositions containing zinc, gold, silver, lead, copper, tin, bismuth, indium, and the like. Preferred are tin-indium (117° C. eutectic) or tin-bismuth (139° C. eutectic) which have a low melting point and are lead-free. That is, the solder preferably does not contain lead, and is preferably a solder containing tin and indium, or a solder containing tin and bismuth.

In order to further increase the bonding strength between the solder and the electrode in the solder part or conductive particles, the solder in the conductive particles is made of nickel, copper, antimony, aluminum, zinc, iron, gold, titanium, phosphorus, germanium, tellurium. , cobalt, bismuth, manganese, chromium, molybdenum, palladium, and other metals. Further, from the viewpoint of further increasing the bonding strength between the solder and the electrode in the solder part or the conductive particles, the solder in the conductive particles preferably contains nickel, copper, antimony, aluminum, or zinc. From the viewpoint of further increasing the bonding strength between the solder and the electrode in the solder part or conductive particles, the content of these metals for increasing the bonding strength is preferably 0% in 100% by weight of the solder in the conductive particles. It is at least .0001% by weight, preferably at most 1% by weight.

It is preferable that the melting point of the second conductive part is higher than the melting point of the solder part. The melting point of the second conductive part is preferably higher than 160°C, more preferably higher than 300°C, still more preferably higher than 400°C, even more preferably higher than 450°C, particularly preferably higher than 500°C, Most preferably above 600°C. Since the solder portion has a low melting point, it melts during conductive connection. Preferably, the second conductive portion does not melt during conductive connection. The conductive particles are preferably used by melting solder, preferably used by melting the solder part, and used by melting the solder part and not melting the second conductive part. It is preferable that Since the melting point of the second conductive part is higher than that of the solder part, only the solder part can be melted without melting the second conductive part during conductive connection.

The absolute value of the difference between the melting point of the solder part and the melting point of the second conductive part is more than 0°C, preferably 5°C or more, more preferably 10°C or more, even more preferably 30°C or more, particularly preferably is 50°C or higher, most preferably 100°C or higher.

Preferably, the second conductive portion includes metal. The metal constituting the second conductive part is not particularly limited. Examples of the metal include gold, silver, copper, platinum, palladium, zinc, lead, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, germanium, cadmium, and alloys thereof. Furthermore, tin-doped indium oxide (ITO) may be used as the metal. The above metals may be used alone or in combination of two or more.

The second conductive part is preferably a nickel layer, a palladium layer, a copper layer, or a gold layer, more preferably a nickel layer, a gold layer, or a copper layer, and even more preferably a copper layer. The conductive particles preferably have a nickel layer, a palladium layer, a copper layer or a gold layer, more preferably a nickel layer, a gold layer or a copper layer, and even more preferably a copper layer. By using conductive particles having these preferable conductive parts for connection between electrodes, the connection resistance between electrodes can be further reduced. Moreover, solder parts can be formed much more easily on the surfaces of these preferable conductive parts.

The thickness of the solder part is preferably 0.005 μm or more, more preferably 0.01 μm or more, and preferably 10 μm or less, more preferably 1 μm or less, and still more preferably 0.3 μm or less. When the thickness of the solder part is at least the above lower limit and below the above upper limit, sufficient conductivity can be obtained, and the conductive particles can be sufficiently deformed during connection between electrodes without becoming too hard. do.

The particle diameter of the conductive particles is preferably 0.5 μm or more, more preferably 1 μm or more, even more preferably 3 μm or more, preferably 100 μm or less, more preferably 60 μm or less, even more preferably 50 μm or less, and particularly preferably It is 40 μm or less. When the particle diameter of the conductive particles is not less than the lower limit and not more than the upper limit, it is possible to more efficiently arrange the solder in the conductive particles on the electrodes, and increase the amount of solder in the conductive particles between the electrodes. It is easy to arrange and has even higher conduction reliability.

The particle diameter of the conductive particles is preferably an average particle diameter, more preferably a number average particle diameter. The average particle diameter of the conductive particles can be determined, for example, by observing 50 arbitrary conductive particles with an electron microscope or an optical microscope and calculating the average value, or by performing laser diffraction particle size distribution measurement.

The CV value of the particle diameter of the conductive particles is preferably 5% or more, more preferably 10% or more, and preferably 40% or less, more preferably 30% or less. When the CV value of the particle size is not less than the lower limit and not more than the upper limit, the solder can be disposed on the electrode even more efficiently. However, the CV value of the particle diameter of the conductive particles may be less than 5%.

The CV value (coefficient of variation) of the particle diameter of the conductive particles can be measured as follows.

CV value (%) = (ρ/Dn) x 100
ρ: Standard deviation of particle diameter of conductive particles Dn: Average value of particle diameter of conductive particles

The shape of the conductive particles is not particularly limited. The shape of the conductive particles may be spherical or may have a shape other than spherical, such as a flat shape.

The content of the conductive particles in 100% by weight of the conductive material is preferably 1% by weight or more, more preferably 2% by weight or more, still more preferably 10% by weight or more, particularly preferably 20% by weight or more, and most preferably is 30% by weight or more, preferably 95% by weight or less, more preferably 90% by weight or less, even more preferably 85% by weight or less. The content of the conductive particles in 100% by weight of the conductive material may be less than 80% by weight. When the content of the conductive particles is not less than the lower limit and not more than the upper limit, the solder in the conductive particles can be placed on the electrodes even more efficiently, and the solder in the conductive particles can be disposed more efficiently between the electrodes. It is easy to arrange and has even higher conduction reliability. From the viewpoint of further improving conduction reliability, it is preferable that the content of the conductive particles be as large as possible.

(thermosetting compound)
The conductive material according to the present invention includes a thermosetting compound. The thermosetting compound is a compound that can be cured by heating. Examples of the thermosetting compound include oxetane compounds, epoxy compounds, episulfide compounds, (meth)acrylic compounds, phenol compounds, amino compounds, unsaturated polyester compounds, polyurethane compounds, silicone compounds, and polyimide compounds. From the viewpoint of further improving the curability and viscosity of the conductive material and further increasing the continuity reliability, epoxy compounds or episulfide compounds are preferred, and epoxy compounds are more preferred. Preferably, the conductive material includes an epoxy compound. The above thermosetting compounds may be used alone or in combination of two or more.

As the epoxy compound, aromatic epoxy compounds such as resorcinol-type epoxy compounds, naphthalene-type epoxy compounds, biphenyl-type epoxy compounds, benzophenone-type epoxy compounds, and phenol novolak-type epoxy compounds are preferable. The melting temperature of the epoxy compound is preferably equal to or lower than the melting point of the solder. The melting temperature of the epoxy compound is preferably 100°C or lower, more preferably 80°C or lower, even more preferably 40°C or lower. By using the above preferable epoxy compound, the viscosity is high at the stage where the connection target members are bonded together, and when acceleration is applied due to impact such as transportation, the first connection target member and the second connection target member are bonded together. Misalignment with the member can be suppressed. Furthermore, the heat during curing can greatly reduce the viscosity, and the aggregation of the solder in the conductive particles can proceed efficiently.

The content of the thermosetting compound in 100% by weight of the conductive material is preferably 5% by weight or more, more preferably 8% by weight or more, even more preferably 10% by weight or more, and preferably 60% by weight or less, The content is more preferably 55% by weight or less, further preferably 50% by weight or less, particularly preferably 40% by weight or less. When the content of the thermosetting compound is at least the above lower limit and below the above upper limit, the solder in the conductive particles can be more efficiently arranged on the electrodes, the positional shift between the electrodes can be further suppressed, and the The conduction reliability can be further improved.

(Thermosetting agent)
Preferably, the conductive material includes a thermosetting agent. The conductive material preferably contains a thermosetting agent together with the thermosetting compound. The thermosetting agent thermosets the thermosetting compound. Examples of the thermosetting agent include imidazole curing agents, phenol curing agents, thiol curing agents, amine curing agents, acid anhydride curing agents, thermal cation curing agents, and thermal radical generators. The above thermosetting agents may be used alone or in combination of two or more.

From the viewpoint of enabling the conductive material to be cured more rapidly at low temperatures, the thermosetting agent is preferably an imidazole curing agent, a thiol curing agent, or an amine curing agent. Further, from the viewpoint of improving the storage stability when the thermosetting compound and the thermosetting agent are mixed, the thermosetting agent is preferably a latent curing agent. Preferably, the latent curing agent is a latent imidazole curing agent, a latent thiol curing agent or a latent amine curing agent. Note that the thermosetting agent may be coated with a polymeric substance such as polyurethane resin or polyester resin.

The above imidazole curing agent is not particularly limited. Examples of the imidazole curing agent include 2-methylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6 -[2'-Methylimidazolyl-(1')]-ethyl-s-triazine and 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct etc.

The above-mentioned thiol curing agent is not particularly limited. Examples of the thiol curing agent include trimethylolpropane tris-3-mercaptopropionate, pentaerythritol tetrakis-3-mercaptopropionate, and dipentaerythritol hexa-3-mercaptopropionate.

The above amine curing agent is not particularly limited. Examples of the amine curing agent include boron trifluoride-amine complex, hexamethylene diamine, octamethylene diamine, decamethylene diamine, 3,9-bis(3-aminopropyl)-2,4,8,10-tetraspiro[5 .5] undecane, bis(4-aminocyclohexyl)methane, metaphenylenediamine, and diaminodiphenylsulfone.

The above-mentioned thermal cation curing agent is not particularly limited. Examples of the thermal cationic curing agent include iodonium-based cationic curing agents, oxonium-based cationic curing agents, and sulfonium-based cationic curing agents. Examples of the iodonium-based cationic curing agent include bis(4-tert-butylphenyl)iodonium hexafluorophosphate. Examples of the oxonium-based cationic curing agent include trimethyloxonium tetrafluoroborate. Examples of the sulfonium-based cationic curing agent include tri-p-tolylsulfonium hexafluorophosphate.

The thermal radical generator described above is not particularly limited. Examples of the thermal radical generator include azo compounds and organic peroxides. Examples of the azo compound include azobisisobutyronitrile (AIBN) and the like. Examples of the organic peroxide include di-tert-butyl peroxide and methyl ethyl ketone peroxide.

The reaction initiation temperature of the thermosetting agent is preferably 50°C or higher, more preferably 60°C or higher, even more preferably 70°C or higher, preferably 250°C or lower, more preferably 200°C or lower, and even more preferably 190°C. The temperature below is particularly preferably 180°C or below. When the reaction start temperature of the thermosetting agent is equal to or higher than the lower limit and lower than the upper limit, the solder can be disposed on the electrode more efficiently.

The content of the thermosetting agent is not particularly limited. With respect to 100 parts by weight of the thermosetting compound, the content of the thermosetting agent is preferably 0.01 parts by weight or more, more preferably 1 part by weight or more, and preferably 200 parts by weight or less, more preferably The amount is 100 parts by weight or less, more preferably 75 parts by weight or less. When the content of the thermosetting agent is equal to or higher than the lower limit, it is easy to sufficiently cure the thermosetting compound. When the content of the thermosetting agent is below the above upper limit, it becomes difficult for excess thermosetting agent that did not take part in curing to remain after curing, and the heat resistance of the cured product becomes even higher.

(flux)
The conductive material according to the present invention includes flux. The conductive material according to the present invention may preferably have a configuration (configuration 1a) in which there is no flux having a particle size that is twice or more the average particle size of the flux. Preferably, the conductive material according to the present invention has a structure in which less than 10% of the fluxes having a particle diameter that is twice or more the average particle diameter of the fluxes are present in 100% of the total number of the fluxes. 1b). The conductive material according to the present invention preferably has a configuration (second configuration) in which the composition obtained by removing the conductive particles from the conductive material is a colloid, and the flux is present as colloidal particles.

In the case where the conductive material has the configuration 1a above, it is preferable that there is no flux having a particle size that is 1.8 times or more the average particle size of the flux, and 1.5 times the average particle size of the flux. It is more preferable that there is no flux having a particle size larger than that. When the average particle diameter of the above-mentioned flux satisfies the above-mentioned preferable conditions, the storage stability can be further improved, the cohesiveness of the solder can be further improved, and the heat resistance of the cured product can be further improved. be able to.

In the case where the conductive material has the configuration 1b, out of 100% of the total number of fluxes, 8% or less of the flux has a particle diameter that is twice or more the average particle diameter of the flux. is preferred. It is more preferable that out of 100% of the total number of the fluxes, 6% or less of the fluxes have a particle diameter that is twice or more the average particle diameter of the flux. When the ratio of the number of fluxes having a particle size that is twice or more the average particle size of the above flux is below the above upper limit, storage stability can be further improved, and the cohesiveness of the solder can be further improved. Furthermore, the heat resistance of the cured product can be further improved.

Either there is no flux with a particle size that is 1.5 times or more the average particle size of the above flux, or there is a particle size that is 1.5 times or more the average particle size of the above flux in 100% of the total number of the above fluxes. Preferably, the number of fluxes having the following properties is less than 20%. It is preferable that out of 100% of the total number of the fluxes, less than 20% of the fluxes have a particle diameter that is 1.5 times or more the average particle diameter of the flux. It is more preferable that out of 100% of the total number of the fluxes, 10% or less of the fluxes have a particle diameter that is 1.5 times or more the average particle diameter of the flux. It is more preferable that out of 100% of the total number of the fluxes, 5% or less of the fluxes have a particle diameter that is 1.5 times or more the average particle diameter of the flux. When the ratio of the number of fluxes having a particle size that is 1.5 times or more the average particle size of the flux is less than the above upper limit or less than the above upper limit, the storage stability can be further improved, and the cohesiveness of the solder can be improved. Furthermore, the heat resistance of the cured product can be further improved.

From the viewpoint of further effectively increasing the storage stability, the viewpoint of further effectively increasing the cohesiveness of the solder, and the viewpoint of further effectively increasing the heat resistance of the cured product, the average particle diameter of the above flux is as follows: Preferably it is 1 μm or less, more preferably less than 1 μm, and still more preferably 0.8 μm or less. The lower limit of the average particle diameter of the flux is not particularly limited. The average particle diameter of the flux may be 0.1 μm or more.

The particle diameter of the above-mentioned flux indicates the diameter when the flux is perfectly spherical, and indicates the maximum diameter when the flux is not perfectly spherical.

The average particle diameter of the above-mentioned flux indicates the number average particle diameter. The particle diameter of the flux is preferably determined by observing 50 arbitrary fluxes with an electron microscope and calculating the average value.

From the viewpoint of further effectively increasing the storage stability, further effectively increasing the cohesiveness of the solder, and further effectively increasing the heat resistance of the cured product, the CV value of the particle size of the above-mentioned flux is (Coefficient of variation) is preferably 40% or less, more preferably 20% or less. The lower limit of the CV value of the particle diameter of the flux is not particularly limited. The CV value of the particle diameter of the flux may be 0.01% or more.

The CV value (coefficient of variation) of the particle diameter of the above flux can be measured as follows.

CV value (%) = (ρ/Dn) x 100
ρ: Standard deviation of flux particle diameter Dn: Average value of flux particle diameter

The shape of the flux is not particularly limited. The shape of the above-mentioned flux may be spherical or may be a shape other than spherical, such as a flat shape.

When the conductive material has the second configuration, the composition obtained by removing the conductive particles from the conductive material is a colloid. From the viewpoint of further effectively increasing the storage stability, further effectively increasing the cohesiveness of the solder, and further effectively increasing the heat resistance of the cured product, the above composition has the following properties: Preferably, the whole is a colloid. The above composition only needs to contain a portion that is a colloid, and the entire composition does not need to be a colloid.

In the case where the conductive material has the second configuration, the flux exists as colloidal particles. From the viewpoint of further effectively increasing the storage stability, further effectively increasing the cohesiveness of the solder, and further effectively increasing the heat resistance of the cured product, the above-mentioned flux should be colloidal particles. is preferable, and it is more preferable that the flux is a colloidal particle having the above-mentioned average particle size in the composition. From the viewpoint of further effectively increasing the storage stability, further effectively increasing the cohesiveness of the solder, and further effectively increasing the heat resistance of the cured product, the above-mentioned flux is added in the above-mentioned composition. Preferably, the flux is dispersed, and more preferably, the flux is uniformly dispersed in the composition. In the conductive material, 20% or more of the total number of fluxes is preferably colloidal particles. In the conductive material, part of the flux may be colloidal particles, and not all of the flux may be colloidal particles.

A method for confirming that the above composition is a colloid includes a method of observing the Tyndall phenomenon using the above composition or a mixture of the above composition and a solvent in which the above flux is not dissolved.

Examples of the above flux include zinc chloride, a mixture of zinc chloride and an inorganic halide, a mixture of zinc chloride and an inorganic acid, molten salt, phosphoric acid, a derivative of phosphoric acid, an organic halide, hydrazine, an organic acid, and pine resin. etc. Only one kind of the above-mentioned flux may be used, or two or more kinds thereof may be used in combination.

Examples of the molten salt include ammonium chloride. Examples of the organic acids include lactic acid, citric acid, stearic acid, glutamic acid, malic acid, and glutaric acid. Examples of the pine resin include activated pine resin and non-activated pine resin. The flux is preferably an organic acid having two or more carboxyl groups or pine resin. The above-mentioned flux may be an organic acid having two or more carboxyl groups, or may be pine resin. By using an organic acid having two or more carboxyl groups or pine resin, the reliability of conduction between the electrodes is further increased.

The above-mentioned pine resin is a rosin whose main component is abietic acid. The flux is preferably rosin, more preferably abietic acid. By using this preferable flux, the reliability of conduction between the electrodes is further increased.

The melting point (activation temperature) of the flux is preferably 50°C or higher, more preferably 70°C or higher, even more preferably 80°C or higher, preferably 200°C or lower, more preferably 190°C or lower, even more preferably 160°C or lower. The temperature is preferably 150°C or lower, even more preferably 140°C or lower. When the melting point (activation temperature) of the flux is above the above lower limit and below the above upper limit, the flux effect is even more effectively exhibited, and the solder in the conductive particles is more efficiently arranged on the electrode. The melting point (activation temperature) of the flux is preferably 60°C or more and 190°C or less. It is particularly preferable that the melting point (activation temperature) of the above-mentioned flux is 80°C or more and 140°C or less.

Examples of the above-mentioned fluxes having an active temperature (melting point) of 60°C or higher and 190°C or lower include succinic acid (melting point 186°C), glutaric acid (melting point 96°C), adipic acid (melting point 152°C), and pimelic acid (melting point 104°C). C), dicarboxylic acids such as suberic acid (melting point 142°C), benzoic acid (melting point 122°C), and malic acid (melting point 130°C).

Moreover, it is preferable that the boiling point of the above-mentioned flux is 200° C. or lower.

The above-mentioned flux is preferably a flux that releases cations when heated. The use of a flux that releases cations upon heating allows the solder in the conductive particles to be placed on the electrode more efficiently.

Examples of the flux that releases cations upon heating include the thermal cation curing agent described above.

More preferably, the flux is a salt of an acid compound and a basic compound. The acid compound preferably has the effect of cleaning the surface of the metal, and the base compound preferably has the effect of neutralizing the acid compound. The flux is preferably a neutralized reaction product of the acid compound and the base compound. The above fluxes may be used alone or in combination of two or more.

From the viewpoint of more efficiently arranging the solder in the conductive particles on the electrode, the melting point of the flux is preferably lower than the melting point of the solder in the conductive particles, more preferably 5° C. or more lower. , more preferably 10°C or more lower. However, the melting point of the flux may be higher than the melting point of the solder in the conductive particles. Usually, the operating temperature of the conductive material is higher than the melting point of the solder in the conductive particles, and if the melting point of the flux is lower than the operating temperature of the conductive material, the melting point of the flux is the melting point of the solder in the conductive particles. Even if the flux is higher than that, the above-mentioned flux can sufficiently exhibit its performance as a flux. For example, in a conductive material whose operating temperature is 150°C or higher and which contains solder (Sn42Bi58: melting point 139°C) in conductive particles and flux (melting point 146°C) which is a salt of malic acid and benzylamine. The flux, which is a salt of malic acid and benzylamine, exhibits sufficient flux action.

From the viewpoint of disposing the solder in the conductive particles on the electrode more efficiently, the melting point of the flux is preferably lower than the reaction initiation temperature of the thermosetting agent, more preferably 5° C. or more lower. More preferably, the temperature is lower by 10°C or more.

The acid compound is preferably an organic compound having a carboxyl group. The above acid compounds include aliphatic carboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, citric acid, malic acid, and cycloaliphatic carboxylic acids. Examples include cyclohexylcarboxylic acid, 1,4-cyclohexyldicarboxylic acid, aromatic carboxylic acids such as isophthalic acid, terephthalic acid, trimellitic acid, and ethylenediaminetetraacetic acid. Preferably, the acid compound is glutaric acid, azelaic acid, or malic acid.

The basic compound is preferably an organic compound having an amino group. The above basic compounds include diethanolamine, triethanolamine, methyldiethanolamine, ethyldiethanolamine, cyclohexylamine, dicyclohexylamine, benzylamine, benzhydrylamine, 2-methylbenzylamine, 3-methylbenzylamine, 4-tert-butylbenzylamine. , N-methylbenzylamine, N-ethylbenzylamine, N-phenylbenzylamine, N-tert-butylbenzylamine, N-isopropylbenzylamine, N,N-dimethylbenzylamine, imidazole compounds, and triazole compounds. . The basic compound is preferably benzylamine, 2-methylbenzylamine, or 3-methylbenzylamine.

The flux may be dispersed in the conductive material or may be attached to the surface of the conductive particles. From the viewpoint of increasing the flux effect even more effectively, the flux is preferably attached to the surface of the conductive particles.

A flux that satisfies the above-mentioned configuration 1a, configuration 1b, and second configuration can be obtained, for example, by melting a solid flux and then re-precipitating it. It is preferable that the redeposition proceeds gently. The method for obtaining the above-mentioned flux is preferably a method in which the solid flux is heated above its melting point to completely melt the flux. The method for obtaining the above-mentioned flux is preferably a method in which molten flux is gradually reprecipitated. By the above method, a uniform flux having the above average particle diameter can be easily obtained.

Another method for obtaining a flux with a relatively small average particle size includes, for example, a method of pulverizing a solid flux. However, in the method of pulverizing solid flux, there is a limit to reducing the average particle size of the flux, and it is difficult to obtain a flux having the above-mentioned average particle size. Furthermore, after the flux is pulverized, the flux tends to coagulate with each other, resulting in a non-uniform flux. Non-uniform flux (pulverized flux) is difficult to uniformly disperse in a conductive material, and when using a non-uniform flux, it is necessary to include flux in the conductive material to increase the cohesiveness of the solder. The amount tends to be relatively large. As a result, the storage stability of the conductive material decreases, and the heat resistance of the cured product of the conductive material decreases, making it difficult to obtain the effects of the present invention. For this reason, the flux is preferably obtained by a method other than pulverizing a solid flux, and is preferably obtained by melting a solid flux whose reprecipitation rate is relatively slow and then re-precipitating it.

From the viewpoint of further effectively increasing the storage stability, further effectively increasing the cohesiveness of the solder, and further effectively increasing the heat resistance of the cured product, 100 parts by weight of the above thermosetting compound was added. On the other hand, the content of the flux is preferably 1 part by weight or more, more preferably 2 parts by weight or more, and preferably 20 parts by weight or less, more preferably 15 parts by weight or less.

From the viewpoint of further effectively increasing the storage stability, the viewpoint of further effectively increasing the cohesiveness of the solder, and the viewpoint of further effectively increasing the heat resistance of the cured product, in 100% by weight of the above conductive material, The content of the flux is preferably 0.05% by weight or more, more preferably 2% by weight or more, and preferably 20% by weight or less, more preferably 15% by weight or less. Moreover, when the content of the flux is more than the above lower limit and less than the above upper limit, it becomes even more difficult to form an oxide film on the surface of the solder and electrode in the conductive particles, and furthermore, the content of the flux is more than the above lower limit and less than the above upper limit. The oxide film formed on the surface can be removed more effectively.

(filler)
A filler may be added to the conductive material. The filler may be an organic filler or an inorganic filler. By adding the filler, the conductive particles can be uniformly aggregated over all the electrodes on the substrate.

It is preferable that the conductive material does not contain the filler or contains 5% by weight or less of the filler. When a crystalline thermosetting compound is used, the smaller the filler content, the easier the solder will move onto the electrode.

The content of the filler in 100% by weight of the conductive material is preferably 0% by weight (not contained) or more, preferably 5% by weight or less, more preferably 2% by weight or less, even more preferably 1% by weight or less. It is. When the content of the filler is not less than the lower limit and not more than the upper limit, the conductive particles are more efficiently arranged on the electrode.

(other ingredients)
The above-mentioned conductive materials may include fillers, extenders, softeners, plasticizers, polymerization catalysts, curing catalysts, colorants, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, and lubricants, as necessary. , various additives such as antistatic agents and flame retardants.

(connected structure)
The connection structure according to the present invention includes a first connection target member having a first electrode on its surface, a second connection target member having a second electrode on its surface, and the first connection target member, and a connecting portion connecting the second connection target member. In the connected structure according to the present invention, the material of the connecting portion is the conductive material described above. In the connected structure according to the present invention, the connection portion is a cured product of the conductive material described above. In the connection structure according to the present invention, the connection portion is formed of the conductive material described above. In the connected structure according to the present invention, the first electrode and the second electrode are electrically connected by a solder part in the connecting part.

In the connected structure according to the present invention, since a specific conductive material is used, the solder in the conductive particles easily collects between the first electrode and the second electrode, and the solder is efficiently spread onto the electrode (line). It can be placed as follows. In addition, a portion of the solder is less likely to be placed in the area (space) where no electrode is formed, and the amount of solder placed in the area where no electrode is formed can be considerably reduced. Therefore, the reliability of conduction between the first electrode and the second electrode can be improved. Moreover, electrical connection between horizontally adjacent electrodes that should not be connected can be prevented, and insulation reliability can be improved.

In addition, in order to efficiently arrange the solder in the conductive particles on the electrode and to significantly reduce the amount of solder placed in areas where no electrode is formed, the conductive material is not a conductive film, Preferably, a conductive paste is used.

The thickness of the solder portion between the electrodes is preferably 10 μm or more, more preferably 20 μm or more, and preferably 100 μm or less, more preferably 80 μm or less. The solder wetted area on the surface of the electrode (the area in contact with the solder out of 100% of the exposed area of the electrode) is preferably 50% or more, more preferably 60% or more, still more preferably 70% or more, and preferably is less than 100%.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view schematically showing a connected structure obtained using a conductive material according to an embodiment of the present invention.

The connection structure 1 shown in FIG. 1 includes a first connection target member 2, a second connection target member 3, and a connection connecting the first connection target member 2 and the second connection target member 3. 4. The connecting portion 4 is made of the above-mentioned conductive material. In this embodiment, the conductive material includes conductive particles, a thermosetting compound, and a flux. In this embodiment, the conductive particles include solder particles. The thermosetting compound, the thermosetting agent, and the flux are referred to as a thermosetting component.

The connecting portion 4 includes a solder portion 4A in which a plurality of solder particles are gathered and bonded to each other, and a cured material portion 4B in which a thermosetting component is thermoset.

The first connection target member 2 has a plurality of first electrodes 2a on its surface (upper surface). The second connection target member 3 has a plurality of second electrodes 3a on the front surface (lower surface). The first electrode 2a and the second electrode 3a are electrically connected by a solder portion 4A. Therefore, the first connection target member 2 and the second connection target member 3 are electrically connected by the solder portion 4A. Note that, in the connection portion 4, no solder exists in a region different from the solder portion 4A gathered between the first electrode 2a and the second electrode 3a (cured material portion 4B portion). In a region different from the solder portion 4A (cured material portion 4B portion), there is no solder separate from the solder portion 4A. Note that solder may be present in a region different from the solder portion 4A gathered between the first electrode 2a and the second electrode 3a (cured material portion 4B portion) as long as the amount is small.

As shown in FIG. 1, in the connection structure 1, a plurality of solder particles gather between a first electrode 2a and a second electrode 3a, and after the plurality of solder particles are melted, a melted solder particle is formed. The solder portion 4A is formed by wetting and spreading the surface of the electrode and solidifying the solder portion 4A. Therefore, the connection area between the solder portion 4A and the first electrode 2a and between the solder portion 4A and the second electrode 3a becomes large. In other words, by using solder particles, the solder portion 4A, the first electrode 2a, and the solder can be bonded more easily than when using conductive particles in which the outer surface of the conductive portion is made of metal such as nickel, gold, or copper. The contact area between the portion 4A and the second electrode 3a becomes larger. Therefore, the conduction reliability and connection reliability in the connected structure 1 are increased. Note that the flux contained in the conductive material is generally gradually deactivated by heating.

In addition, in the connection structure 1 shown in FIG. 1, all of the solder parts 4A are located in the opposing region between the first and second electrodes 2a and 3a. The modified connected structure 1X shown in FIG. 3 differs from the connected structure 1 shown in FIG. 1 only in the connecting portion 4X. The connecting portion 4X has a solder portion 4XA and a cured material portion 4XB. Like the connection structure 1X, most of the solder portion 4XA is located in the area where the first and second electrodes 2a and 3a are facing each other, and a part of the solder portion 4XA is located in the area where the first and second electrodes 2a and 3a face each other. It may protrude laterally from the opposing regions of the electrodes 2a and 3a. The solder portion 4XA that protrudes laterally from the opposing region of the first and second electrodes 2a and 3a is a part of the solder portion 4XA, and is not solder separate from the solder portion 4XA. In addition, in this embodiment, the amount of solder separated from the solder part can be reduced, but the solder separated from the solder part may exist in the cured material part.

By reducing the amount of solder particles used, it becomes easier to obtain the connected structure 1. If the amount of solder particles used is increased, it becomes easier to obtain the connected structure 1X.

The opposing portions of the first electrode and the second electrode are seen in the stacking direction of the first electrode, the connecting portion, and the second electrode. In this case, from the viewpoint of further increasing conduction reliability, the area of the opposing portion of the first electrode and the second electrode should be at least 50% (more preferably at least 60%, and even more preferably at least 60%). It is preferable that the solder portions in the connection portions are arranged in 70% or more, particularly preferably 80% or more, and most preferably 90% or more.

Next, an example of a method for manufacturing the connected structure 1 using a conductive material according to an embodiment of the present invention will be described.

First, a first connection target member 2 having a first electrode 2a on its surface (upper surface) is prepared. Next, as shown in FIG. 2(a), a conductive material 11 containing a thermosetting component 11B and a plurality of solder particles 11A is placed on the surface of the first connection target member 2 (first process). The conductive material 11 includes a thermosetting compound, a thermosetting agent, and a flux as the thermosetting component 11B.

A conductive material 11 is placed on the surface of the first connection target member 2 on which the first electrode 2a is provided. After the conductive material 11 is placed, the solder particles 11A are placed both on the first electrode 2a (line) and on the area (space) where the first electrode 2a is not formed.

Methods for disposing the conductive material 11 include, but are not particularly limited to, application using a dispenser, screen printing, and ejection using an inkjet device.

Further, a second connection target member 3 having a second electrode 3a on its surface (lower surface) is prepared. Next, as shown in FIG. 2(b), in the conductive material 11 on the surface of the first connection target member 2, on the surface of the conductive material 11 opposite to the first connection target member 2 side, Arranging the second connection target member 3 (second step). The second connection target member 3 is placed on the surface of the conductive material 11 from the second electrode 3a side. At this time, the first electrode 2a and the second electrode 3a are made to face each other.

Next, the conductive material 11 is heated to a temperature higher than the melting point of the solder particles 11A (third step). Preferably, the conductive material 11 is heated to a temperature higher than the curing temperature of the thermosetting component 11B (thermosetting compound). During this heating, the solder particles 11A existing in the region where no electrode is formed gather between the first electrode 2a and the second electrode 3a (self-agglomeration effect). When a conductive paste is used instead of a conductive film, the solder particles 11A gather more effectively between the first electrode 2a and the second electrode 3a. Further, the solder particles 11A are melted and bonded to each other. Further, the thermosetting component 11B is thermoset. As a result, as shown in FIG. 2(c), the connection portion 4 connecting the first connection target member 2 and the second connection target member 3 is formed of the conductive material 11. A connecting portion 4 is formed by the conductive material 11, a solder portion 4A is formed by joining a plurality of solder particles 11A, and a cured material portion 4B is formed by thermosetting the thermosetting component 11B. If the solder particles 11A move sufficiently, the solder particles 11A that are not located between the first electrode 2a and the second electrode 3a start moving, and then the first electrode 2a and the second electrode 11A start moving. It is not necessary to keep the temperature constant until the movement of the solder particles 11A between the solder particles 3a and the solder particles 11A is completed.

In this embodiment, it is preferable not to apply pressure in the second step and the third step. In this case, the weight of the second connection target member 3 is applied to the conductive material 11 . Therefore, when forming the connection portion 4, the solder particles 11A gather more effectively between the first electrode 2a and the second electrode 3a. Note that if pressure is applied in at least one of the second step and the third step, the solder particles 11A tend to gather between the first electrode 2a and the second electrode 3a. are more likely to be inhibited.

A state in which, when a second connection target member is superimposed on a first connection target member coated with a conductive material, the electrodes of the first connection target member and the electrodes of the second connection target member are misaligned. In some cases, the first connection target member and the second connection target member are overlapped. In this embodiment, since pressurization is not performed, the deviation can be corrected and the electrodes of the first connection target member and the electrodes of the second connection target member can be connected (self-alignment effect). This is because the molten solder that has self-agglomerated between the electrodes of the first connection target member and the electrode of the second connection target member is removed between the electrodes of the first connection target member and the second connection target member. This is because the energy is more stable when the contact area between the solder between the electrodes and other components of the conductive material is minimized. This is because a force acts to create an aligned connection structure that has the minimum area. At this time, it is desirable that the conductive material is not cured and that the viscosity of the components of the conductive material other than the conductive particles is sufficiently low at that temperature and time.

The viscosity of the conductive material at the melting point of the solder is preferably 50 Pa.s or less, more preferably 10 Pa.s or less, even more preferably 1 Pa.s or less, preferably 0.1 Pa.s or more, more preferably 0.1 Pa.s or less. It is 2 Pa·s or more. If the viscosity is below the upper limit, the solder in the conductive particles can be efficiently aggregated. If the above-mentioned viscosity is more than the above-mentioned lower limit, it is possible to suppress voids in the connection portion and to suppress the conductive material from protruding outside the connection portion.

The viscosity of the conductive material at the melting point of the solder is measured as follows.

The viscosity of the conductive material at the melting point of the solder is determined using STRESSTECH (manufactured by REOLOGICA), etc., with strain control of 1 rad, frequency of 1 Hz, temperature increase rate of 20°C/min, and measurement temperature range of 25 to 200°C (however, the temperature range of the solder is 25 to 200°C). If the melting point exceeds 200°C, measurement can be performed under the following conditions: the upper temperature limit is the melting point of the solder. From the measurement results, the viscosity at the melting point (°C) of the solder is evaluated.

In this way, the connected structure 1 shown in FIG. 1 is obtained. In addition, the said 2nd process and the said 3rd process may be performed continuously. Further, after performing the second step, the obtained laminate of the first connection target member 2, the conductive material 11, and the second connection target member 3 is moved to a heating section, and the third You may perform the process. In order to perform the heating, the laminate may be placed on a heating member, or the laminate may be placed in a heated space.

The heating temperature in the third step is preferably 140°C or higher, more preferably 160°C or higher, preferably 450°C or lower, more preferably 250°C or lower, even more preferably 200°C or lower.

The heating method in the third step includes heating the entire connected structure to a temperature above the melting point of the solder in the conductive particles and above the curing temperature of the thermosetting component using a reflow oven or an oven; , a method of locally heating only the connecting portion of the connected structure.

Examples of devices used in the local heating method include a hot plate, a heat gun that applies hot air, a soldering iron, and an infrared heater.

In addition, when heating locally with a hot plate, use a highly thermally conductive metal directly below the connection, and use a low thermally conductive material such as fluororesin for other areas where it is not desirable to heat. , preferably forming the top surface of the hot plate.

The first and second connection target members are not particularly limited. Specifically, the first and second connection target members include semiconductor chips, semiconductor packages, LED chips, LED packages, electronic components such as capacitors and diodes, resin films, printed circuit boards, flexible printed circuit boards, and flexible Examples include electronic components such as flat cables, rigid-flexible boards, circuit boards such as glass epoxy boards, and glass boards. It is preferable that the first and second connection target members are electronic components.

It is preferable that at least one of the first connection target member and the second connection target member is a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible circuit board. It is preferable that at least one of the first connection target member and the second connection target member is a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible circuit board. Resin films, flexible printed circuit boards, flexible flat cables, and rigid-flexible circuit boards have the properties of being highly flexible and relatively lightweight. When a conductive film is used to connect such connection target members, solder tends to be difficult to collect on the electrodes. On the other hand, by using a conductive paste, even when using a resin film, flexible printed circuit board, flexible flat cable, or rigid-flexible circuit board, the solder can be efficiently collected on the electrodes, thereby improving the continuity reliability between the electrodes. can be sufficiently increased. When using resin films, flexible printed circuit boards, flexible flat cables, or rigid-flex circuit boards, the reliability of conduction between electrodes can be improved by not applying pressure, compared to when using other connection objects such as semiconductor chips. The improvement effect can be obtained even more effectively.

Examples of the electrodes provided on the connection target member include metal electrodes such as gold electrodes, nickel electrodes, tin electrodes, aluminum electrodes, copper electrodes, molybdenum electrodes, silver electrodes, SUS electrodes, and tungsten electrodes. When the member to be connected is a flexible printed circuit board, the electrode is preferably a gold electrode, a nickel electrode, a tin electrode, a silver electrode, or a copper electrode. When the member to be connected is a glass substrate, the electrode is preferably an aluminum electrode, a copper electrode, a molybdenum electrode, a silver electrode, or a tungsten electrode. In addition, when the said electrode is an aluminum electrode, it may be an electrode formed only with aluminum, and the electrode may be an electrode in which an aluminum layer is laminated|stacked on the surface of a metal oxide layer. Examples of the material for the metal oxide layer include indium oxide doped with a trivalent metal element and zinc oxide doped with a trivalent metal element. Examples of the trivalent metal elements include Sn, Al, and Ga.

Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples. The invention is not limited only to the following examples.

Thermosetting compound:
"jER152" manufactured by Mitsubishi Chemical Corporation, epoxy resin

Thermosetting agent (thermal curing accelerator (catalyst)):
"BF3-MEA" manufactured by Stella Chemifa, boron trifluoride-monoethylamine complex

Conductive particles:
“Sn42Bi58 (DS-10)” manufactured by Mitsui Kinzoku Mining Co., Ltd.

flux:
(1) Flux 1
How to make Flux 1:
24 g of water as a reaction solvent and 13.212 g of glutaric acid (manufactured by Wako Pure Chemical Industries, Ltd.) were placed in a glass bottle and dissolved until uniform at room temperature. Then, 10.715 g of benzylamine (manufactured by Wako Pure Chemical Industries, Ltd.) was added and stirred for about 5 minutes to obtain a mixed solution. The resulting mixture was placed in a refrigerator at 5 to 10°C and left overnight. The precipitated crystals were collected by filtration, washed with water, and dried in vacuum. Flux 1 was obtained by heating the dried crystals at 140° C. for 15 minutes to completely melt them and gradually re-precipitating them at 25° C. over 30 minutes.

(2) Flux 2
How to make Flux 2:
24 g of water as a reaction solvent and 13.212 g of glutaric acid (manufactured by Wako Pure Chemical Industries, Ltd.) were placed in a glass bottle and dissolved until uniform at room temperature. Then, 10.715 g of benzylamine (manufactured by Wako Pure Chemical Industries, Ltd.) was added and stirred for about 5 minutes to obtain a mixed solution. The resulting mixture was placed in a refrigerator at 5 to 10°C and left overnight. The precipitated crystals were collected by filtration, washed with water, and dried in vacuum. Flux 2 was obtained by heating the dried crystals at 160° C. for 5 minutes to completely melt them and gradually re-precipitating them at 25° C. over 30 minutes.

(3) Flux 3
How to make Flux 3:
24 g of water as a reaction solvent and 13.212 g of glutaric acid (manufactured by Wako Pure Chemical Industries, Ltd.) were placed in a glass bottle and dissolved until uniform at room temperature. Then, 10.715 g of benzylamine (manufactured by Wako Pure Chemical Industries, Ltd.) was added and stirred for about 5 minutes to obtain a mixed solution. The resulting mixture was placed in a refrigerator at 5 to 10°C and left overnight. The precipitated crystals were collected by filtration, washed with water, and dried in vacuum. Flux 3 was obtained by crushing the dried crystals in a mortar.

(4) Flux 4
How to make Flux 4:
24 g of water as a reaction solvent and 13.212 g of glutaric acid (manufactured by Wako Pure Chemical Industries, Ltd.) were placed in a glass bottle and dissolved until uniform at room temperature. Then, 10.715 g of benzylamine (manufactured by Wako Pure Chemical Industries, Ltd.) was added and stirred for about 5 minutes to obtain a mixed solution. The resulting mixture was placed in a refrigerator at 5 to 10°C and left overnight. The precipitated crystals were collected by filtration, washed with water, and dried in vacuum. Flux 4 was obtained by pulverizing the dried crystals using a jet mill pulverizer manufactured by Nisshin Engineering Co., Ltd.

(Examples 1-2 and Comparative Examples 1-3)
(1) Preparation of conductive material (anisotropic conductive paste) The components shown in Table 1 below were blended in the amounts shown in Table 1 below to obtain a conductive material (anisotropic conductive paste).

(2) Fabrication of first connected structure (L/S=50 μm/50 μm) Using the conductive material (anisotropic conductive paste) immediately after fabrication, fabricate the first bonded structure as follows. did.

A glass epoxy substrate (FR-4 substrate) (first connection target member) having a copper electrode pattern (copper electrode thickness 12 μm) with an L/S of 50 μm/50 μm and an electrode length of 3 mm on the upper surface was prepared. In addition, a flexible printed circuit board (second connection target member) having a copper electrode pattern with an L/S of 50 μm/50 μm and an electrode length of 3 mm (copper electrode thickness of 12 μm) on the lower surface was prepared.

The overlapping area of the glass epoxy substrate and the flexible printed circuit board was 1.5 cm x 3 mm, and the number of connected electrodes was 75 pairs.

Applying a conductive material (anisotropic conductive paste) immediately after preparation to the upper surface of the glass epoxy substrate using a metal mask by screen printing so that the thickness is 100 μm on the electrodes of the glass epoxy substrate, A layer of conductive material (anisotropic conductive paste) was formed. Next, the flexible printed circuit board was laminated on the upper surface of the conductive material (anisotropic conductive paste) layer so that the electrodes faced each other. At this time, no pressure was applied. The weight of the flexible printed circuit board is added to the conductive material (anisotropic conductive paste) layer. From this state, the temperature of the conductive material (anisotropic conductive paste) layer was heated to 139° C. (melting point of solder) 5 seconds after the start of temperature rise. Furthermore, 15 seconds after the start of temperature rise, the conductive material (anisotropic conductive paste) layer is heated to a temperature of 160°C to harden the conductive material (anisotropic conductive paste) layer, and the connected structure is formed. Obtained. No pressure was applied during heating.

(3) Production of second connection structure (L/S = 75 μm/75 μm) Glass epoxy substrate having a copper electrode pattern (copper electrode thickness 12 μm) with L/S of 75 μm/75 μm and electrode length of 3 mm on the top surface (FR-4 board) (first connection target member) was prepared. Further, a flexible printed circuit board (second connection target member) having a copper electrode pattern (copper electrode thickness 12 μm) with an L/S of 75 μm/75 μm and an electrode length of 3 mm on the lower surface was prepared.

A second connected structure was obtained in the same manner as the first connected structure except that the glass epoxy substrate and flexible printed circuit board having different L/S were used.

(4) Production of third connection structure (L/S=100 μm/100 μm) Glass epoxy substrate having a copper electrode pattern (copper electrode thickness 12 μm) with L/S of 100 μm/100 μm and electrode length of 3 mm on the top surface (FR-4 board) (first connection target member) was prepared. Further, a flexible printed circuit board (second connection target member) having a copper electrode pattern (copper electrode thickness 12 μm) with an L/S of 100 μm/100 μm and an electrode length of 3 mm on the lower surface was prepared.

A third connected structure was obtained in the same manner as the first connected structure except that the glass epoxy substrate and flexible printed circuit board having different L/S were used.

(evaluation)
(1) Existence state of flux The average particle diameter of the obtained flux was calculated from the average value of the particle diameters of 50 arbitrary fluxes measured using a laser microscope ("OLS4100" manufactured by Olympus Corporation).

From the average particle diameter of the obtained flux, the ratio of the number of fluxes having a particle diameter that is twice or more the average particle diameter of the flux in 100% of the total number of fluxes, and the average particle diameter of flux in 100% of the total number of fluxes. The ratio of the number of fluxes having a particle diameter of 1.5 times or more was calculated.

(2) Colloid The conductive particles were removed from the conductive material (anisotropic conductive paste) by filtering the obtained conductive material (anisotropic conductive paste). The composition from which conductive particles had been removed was placed in a 10 mL screw tube, and a laser pointer was irradiated from the side of the screw tube to check whether the Tyndall phenomenon due to flux was observed. Colloids were judged according to the following criteria. In addition, it was confirmed that the thermosetting compound and the thermosetting agent were dissolved.

[Colloid criteria]
○: Tyndall phenomenon due to flux is observed ×: Tyndall phenomenon due to flux is not observed

(3) Storage stability The viscosity (η1) at 25° C. of the conductive material (anisotropic conductive paste) immediately after production was measured. Further, the conductive material (anisotropic conductive paste) immediately after preparation was left at room temperature for 24 hours, and the viscosity (η2) at 25° C. of the conductive material (anisotropic conductive paste) after being left was measured. The above viscosity was measured using an E-type viscometer (“TVE22L” manufactured by Toki Sangyo Co., Ltd.) at 25° C. and 5 rpm. The viscosity increase rate (η2/η1) was calculated from the measured value of viscosity. Storage stability was determined based on the following criteria.

[Criteria for storage stability]
○: Viscosity increase rate (η2/η1) is 1.5 or less △: Viscosity increase rate (η2/η1) is more than 1.5 and 2.0 or less ×: Viscosity increase rate (η2/η1) is 2.0 or less exceed

(4) Heat resistance of cured product A cured product was obtained by heating the obtained conductive material (anisotropic conductive paste) at 150° C. for 2 hours. The glass transition temperature (Tg) of the obtained cured product was measured using a dynamic viscoelasticity measuring device ("Rheogel-E" manufactured by UBM) at a heating rate of 10° C./min. The heat resistance of the cured product was evaluated based on the following criteria.

[Criteria for determining heat resistance of cured product]
○: Tg of cured product is 100°C or higher △: Tg of cured product is 90°C or higher and lower than 100°C ×: Tg of cured product is lower than 90°C

(5) Accuracy of solder placement on electrodes (solder cohesiveness)
In the obtained first, second, and third connected structures, the portions where the first electrode and the second electrode face each other in the stacking direction of the first electrode, the connecting portion, and the second electrode are When viewed, the ratio X of the area where the solder part in the connection part is arranged to 100% of the area of the opposing part of the first electrode and the second electrode was evaluated. The placement accuracy of the solder on the electrode (solder cohesiveness) was judged based on the following criteria.

[Criteria for determining solder placement accuracy (solder cohesion) on electrodes]
○○: Proportion X is 70% or more ○: Proportion X is 60% or more and less than 70% △: Proportion X is 50% or more and less than 60% ×: Proportion X is less than 50%

(6) Conduction reliability between upper and lower electrodes In the obtained first, second, and third connected structures (n = 15 pieces), the connection resistance per connection point between the upper and lower electrodes was 4, respectively. It was measured by the terminal method. The average value of connection resistance was calculated. Note that from the relationship of voltage=current×resistance, the connection resistance can be determined by measuring the voltage when a constant current is passed. Continuity reliability was determined based on the following criteria.

[Criteria for determining continuity reliability]
○○: Average value of connection resistance is 50mΩ or less ○: Average value of connection resistance is more than 50mΩ and less than 70mΩ △: Average value of connection resistance is more than 70mΩ and less than 100mΩ ×: Average value of connection resistance is more than 100mΩ, or A poor connection has occurred.

(7) Insulation reliability between horizontally adjacent electrodes The obtained first, second, and third connected structures (n = 15 pieces) were left in an atmosphere of 85°C and 85% humidity for 100 hours. Thereafter, 5V was applied between the horizontally adjacent electrodes, and the resistance values were measured at 25 locations. Insulation reliability was judged based on the following criteria.

[Judgment criteria for insulation reliability]
○○: The average value of connection resistance is 10 ⁷ Ω or more. ○: The average value of connection resistance is 10 ⁶ Ω or more and less than 10 ⁷ Ω. △: The average value of connection resistance is 10 ⁵ Ω or more and less than 10 ^{6 Ω. ×: The average value of connection resistance is 10 5 Ω or more and less than 10 6} Ω. Average value is less than 10 ⁵ Ω

The results are shown in Table 1 below.

A similar tendency was observed even when a resin film, a flexible flat cable, and a rigid-flexible board were used instead of the flexible printed circuit board.

1, 1X... Connection structure 2... First connection target member 2a... First electrode 3... Second connection target member 3a... Second electrode 4, 4X... Connection part 4A, 4XA... Solder part 4B, 4XB ...Cured product part 11...Conductive material 11A...Solder particles (conductive particles)
11B...Thermosetting component 21...Electroconductive particles (solder particles)
31... Conductive particles 32... Base material particles 33... Conductive part (conductive part having solder)
33A...Second conductive part 33B...Solder part 41...Conductive particles 42...Solder part

Claims (6)

A plurality of conductive particles having solder on the outer surface of the conductive part, a thermosetting compound, and a flux,
The average particle diameter of the flux is 1 μm or less,
The content of the flux is 1 part by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the thermosetting compound,
A conductive material comprising the following first configuration.
First configuration: There is no flux having a particle size that is twice or more the average particle size of the flux, or the particle size of 100% of the total number of fluxes is twice or more the average particle size of the flux. There are less than 10% of fluxes with Either there is no flux having a particle size that is 1.5 times or more the average particle size of the flux, or there is a particle size that is 1.5 times or more the average particle size of the flux in 100% of the total number of fluxes. The electrically conductive material according to claim 1, wherein the flux having a conductive material is present in a number of less than 20%. The conductive material according to claim 1 or 2 , wherein the content of the flux is 0.05% by weight or more and 15% by weight or less in 100% by weight of the conductive material. The conductive material according to any one of claims 1 to 3 , which is a conductive paste and excludes a conductive paste in which the flux is contained in a flux-encapsulating capsule . a first connection target member having a first electrode on its surface;
a second connection target member having a second electrode on its surface;
comprising a connection part connecting the first connection target member and the second connection target member,
The material of the connecting portion is the conductive material according to any one of claims 1 to 4 ,
A connection structure in which the first electrode and the second electrode are electrically connected by a solder part in the connection part. When looking at the opposing portions of the first electrode and the second electrode in the stacking direction of the first electrode, the connecting portion, and the second electrode, the first electrode and the second electrode are 6. The connection structure according to claim 5 , wherein the solder part in the connection part is disposed on 50% or more of 100% of the area of the part facing the second electrode.

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