Conductive paste, RFID inlay, and manufacturing method of RFID inlay

Abstract

This invention provides a conductive paste that can be precisely applied to wiring. Even when materials are transported vertically during manufacturing, it prevents wafer misalignment and conductive filler agglomeration, thereby improving the conductivity reliability of the resulting electronic components. The conductive paste of this invention comprises a curing compound, a curing agent, and a plurality of conductive fillers. The specific gravity of the conductive fillers is 1.5 to 4.0. The content of the conductive fillers in 100% by weight of the conductive paste is 1.0% to 15% by weight. The ratio of the viscosity of the conductive paste at 25°C and 0.5 rpm to its viscosity at 25°C and 5 rpm is 1.5 to 4.5. The viscosity of the conductive paste at 25°C and 5 rpm is 5 Pa·s to 50 Pa·s.

Description

Conductive paste, RFID inlay, and method for manufacturing RFID inlay The present invention relates to a conductive paste containing a conductive filler, an RFID inlay using the conductive paste, and a method for manufacturing the RFID inlay. RFID (Radio Frequency Identification) inlays, which enable contactless data transmission and reception, are widely used in contactless RFID tags and cards. In particular, RFID inlays operating in the UHF (Ultra High Frequency) band (860 MHz to 960 MHz) have attracted attention due to their longer communication range. These inlays are used for a variety of items and purposes, including commuter tickets, inventory management, circulation management, and history management. Regarding RFID inlays, a conductive paste containing a conductive filler and a binder resin is sometimes used to bond and connect a wafer having electrodes on its surface and a substrate having wiring (antenna pattern) on its surface. Patent Document 1 below discloses an adhesive for electronic components. The adhesive is an acrylic adhesive composition comprising a free radical initiator with a 10-hour half-life temperature of 80°C or less, an oligomer containing a vinylidene group, and at least one diluent. The adhesive cures rapidly at low temperatures and has a shelf life of at least 24 hours at room temperature. Patent Document 2 below discloses a conductive adhesive comprising a polymerizable acrylic compound, an organic peroxide, and solder particles, wherein the one-minute half-life temperature of the organic peroxide is lower than the solidus temperature of the solder particles. [Prior Art Document] [Patent Document] [Patent Document 1] Japanese Patent Application Publication No. 2006-144018 [Patent Document 2] Japanese Patent Application Publication No. 2013-124330 [Problems to be solved by the invention] In the manufacturing of electronic components such as RFID inlays, a roll-to-roll process is sometimes used to facilitate mass production. In this process, a laminated body with conductive paste and wafers placed on the surface of a substrate is transported not only horizontally but also vertically. For example, a laminated body being transported horizontally may change its transport direction to vertical when it reaches a roll. When the laminate is transported vertically before the conductive paste has fully cured, the conductive material (conductive filler) in the paste may not be dispersed but may become concentrated, depending on the specific gravity of the conductive material. This may result in reduced electrical conductivity reliability in the resulting electronic component. Furthermore, when the laminate is transported vertically, the position of the wafer placed on the substrate surface may shift, which may also reduce the electrical conductivity reliability of the resulting electronic component. Furthermore, in recent years, as electronic components using RFID inlays have become smaller, the chips used in RFID inlays have also been miniaturized, and the industry is seeking a conductive paste that can be precisely configured on wiring. The present invention aims to provide a conductive paste that can be precisely applied to wiring and that prevents chip positional shifting and conductive filler segregation during vertical transport during manufacturing, thereby improving the conductivity reliability of the resulting electronic components. Furthermore, the present invention aims to provide an RFID inlay using the conductive paste and a method for manufacturing the RFID inlay. [Technical Means for Solving the Problem] This specification discloses the following conductive paste, RFID inlay, and method for manufacturing the RFID inlay. Item 1. A conductive paste comprising a curable compound, a curing agent, and a plurality of conductive fillers, wherein the specific gravity of the conductive fillers is from 1.5 to 4.0, the content of the conductive fillers in 100% by weight of the conductive paste is from 1.0% to 15% by weight, the ratio of the viscosity of the conductive paste at 25°C and 0.5 rpm to the viscosity at 25°C and 5 rpm is from 1.5 to 4.5, and the viscosity of the conductive paste at 25°C and 5 rpm is from 5 Pa·s to 50 Pa·s. Item 2. The conductive paste according to Item 1, wherein the curable compound comprises a (meth)acrylic compound. Item 3. The conductive paste according to Item 1 or 2, wherein the conductive filler is conductive particles, and the particle size of the conductive particles is 10 μm or less. Item 4. The conductive paste according to Item 3, wherein the conductive particles include substrate particles and a conductive portion disposed on a surface of the substrate particles. Item 5. The conductive paste according to any one of Items 1 to 4, which is applied to a substrate having a surface tension of 30 mN / m to 50 mN / m. Item 6. The conductive paste according to any one of Items 1 to 5, which is used to obtain an RFID inlay. Item 7. An RFID inlay comprising a substrate having wiring on its surface, a chip having electrodes on its surface, and a bonding portion for bonding the substrate and the chip, wherein the material of the bonding portion is a conductive paste as described in any one of items 1 to 6, and the wiring and the electrodes are electrically connected via the conductive filler in the bonding portion. Item 8. A method for manufacturing an RFID inlay, comprising: a first configuration step of configuring a conductive paste as described in any one of items 1 to 6 on a surface of a substrate having wiring on its surface; a second configuration step of configuring a chip having electrodes on its surface on the surface of the conductive paste opposite to the substrate; and a subsequent step of heating and pressurizing the conductive paste to form a bonding portion that bonds the substrate and the chip with the conductive paste, and electrically connecting the wiring and the electrode using the conductive filler in the bonding portion. Item 9. The method for manufacturing an RFID inlay according to Item 8, wherein the substrate is in a long strip shape, and the RFID inlay is manufactured by conveying the long strip substrate in a roll-to-roll manner in the first arrangement step, the second arrangement step, and the subsequent step. [Effects of the Invention] The conductive paste of the present invention comprises a curable compound, a hardener, and a plurality of conductive fillers. In the conductive paste of the present invention, the specific gravity of the conductive filler is 1.5 to 4.0. The content of the conductive filler in 100% by weight of the conductive paste is 1.0 to 15% by weight. The ratio of the viscosity of the conductive paste at 25°C and 0.5 rpm to the viscosity at 25°C and 5 rpm is 1.5 to 4.5, and the viscosity of the conductive paste at 25°C and 5 rpm is 5 to 50 Pa·s. Due to the above-described structure, the conductive paste of the present invention can be precisely applied to wiring. This prevents chip positional shifting and conductive filler segregation during vertical transport of the object during the manufacturing process, thereby improving the conductivity reliability of the resulting electronic component. Hereinafter, the present invention will be described in detail. (Conductive Paste) The conductive paste of the present invention comprises a curable compound, a curing agent, and a plurality of conductive fillers. In the conductive paste of the present invention, the specific gravity of the conductive filler is greater than 1.5 and less than 4.0. In the conductive paste of the present invention, the content of the conductive filler in 100% by weight of the conductive paste is greater than 1.0% by weight and less than 15% by weight. In the conductive paste of the present invention, the ratio of the viscosity of the conductive paste at 25°C and 0.5 rpm to the viscosity at 25°C and 5 rpm is greater than 1.5 and less than 4.5, and the viscosity of the conductive paste at 25°C and 5 rpm is greater than 5 Pa·s and less than 50 Pa·s. With respect to the conductive paste of the present invention, since it has the above-mentioned structure, the conductive paste can be arranged on the wiring with high precision. In addition, with respect to the conductive paste of the present invention, since it has the above-mentioned structure, when the conveyed object is conveyed in the vertical direction during the manufacturing process, it is also possible to prevent the position shift of the chip and prevent the conductive filler from being concentrated, so that the conductive filler is well dispersed. As a result, the conduction reliability can be improved. For example, when the conveyed object conveyed in the horizontal direction reaches the reel part, the conveying direction at the reel part sometimes changes to the vertical direction. In this case, the direction of the conveyed object changes, and therefore, the position shift of the chip and the concentration of the conductive filler are likely to occur. However, by means of the structure of the present invention, the position shift of the chip and the concentration of the conductive filler can be prevented. The conductive paste of the present invention is in a paste form at 25° C. The conductive paste is sprayed and used at, for example, 20° C. to 50° C. The conductive paste of the present invention is preferably sprayed and used using a jet dispenser. The conductive paste has a viscosity (ηA) of 5 Pa·s to 50 Pa·s at 25°C and 5 rpm. The viscosity (ηA) is preferably 7 Pa·s or higher, more preferably 8 Pa·s or higher, and even more preferably 10 Pa·s or higher, and is preferably 45 Pa·s or lower, more preferably 43 Pa·s or lower, and even more preferably 40 Pa·s or lower. When the viscosity (ηA) is above the lower limit, wafer positional shifting can be more effectively prevented when the object is transported vertically during the manufacturing process. When the viscosity (ηA) is below the upper limit, the conductive paste can be placed on fine wiring with greater precision. The ratio (ηB / ηA) of the viscosity (ηB) of the conductive paste at 25°C and 0.5 rpm to the viscosity (ηA) at 25°C and 5 rpm is defined as the thixotropic index. The ratio (thixotropic index) of the viscosity (ηB) of the conductive paste at 25°C and 0.5 rpm to the viscosity (ηA) at 25°C and 5 rpm is 1.5 or more and 4.5 or less. The thixotropic index is preferably 2.0 or more, more preferably 2.2 or more, and further preferably 2.5 or more, and preferably 4.2 or less, more preferably 4.0 or less, and further preferably 3.8 or less. If the thixotropic index is above the lower limit, it is possible to more effectively prevent the position of the chip from shifting when the object to be conveyed is conveyed in the vertical direction during the manufacturing process. If the thixotropic index is below the upper limit, the conductive paste can be arranged on fine wiring with higher precision. The viscosity (ηA) of the conductive paste at 25°C and 5 rpm and the viscosity (ηB) of the conductive paste at 25°C and 0.5 rpm can be measured using an E-type viscometer, for example, the TV22 viscometer manufactured by Toki Sangyo Co., Ltd. The viscosity (ηC) of the composition of the conductive paste excluding the conductive filler at 25°C and 5 rpm is preferably 5 Pa·s or higher and 50 Pa·s or lower. The viscosity (ηC) is preferably 7 Pa·s or higher, more preferably 8 Pa·s or higher, and even more preferably 10 Pa·s or higher, and is preferably 45 Pa·s or lower, more preferably 43 Pa·s or lower, and even more preferably 40 Pa·s or lower. When the viscosity (ηC) is above the lower limit, positional shifting of the wafer can be more effectively prevented when the object is transported vertically during the manufacturing process. When the viscosity (ηC) is below the upper limit, the conductive paste can be placed on fine wiring with greater precision. The viscosity (ηC) of the composition excluding the conductive filler in the conductive paste at 25°C and 5 rpm can be measured, for example, by the following method. The viscosity of the composition after removing the conductive filler from the conductive paste is measured using an E-type viscometer. The viscosity of the composition containing the conductive paste materials excluding the conductive filler is measured using an E-type viscometer. Examples of the E-type viscometer include the "TV22 Viscometer" manufactured by Toki Sangyo Co., Ltd. The conductive paste is 25°C and the shear speed is 0.1 sec -1The viscosity (ηD) is preferably 5 Pa·s or higher and preferably 50 Pa·s or lower. When the viscosity (ηD) is above the lower limit, wafer positional shifting can be more effectively prevented when the object is transported vertically during the manufacturing process. When the viscosity (ηD) is below the upper limit, the conductive paste can be placed on fine wiring with greater precision. The conductive paste is 25°C and the shear speed is 0.01 sec -1 The viscosity (ηE) is preferably 15 Pa·s or higher and preferably 200 Pa·s or lower. When the viscosity (ηE) is above the lower limit, wafer positional shifting can be more effectively prevented when the object is transported vertically during the manufacturing process. When the viscosity (ηE) is below the upper limit, the conductive paste can be placed on fine wiring with greater precision. The conductive paste is 25°C and the shear rate is 0.001 sec -1 The viscosity (ηF) is preferably 20 Pa·s or higher and preferably 10,000 Pa·s or lower. When the viscosity (ηF) is above the lower limit, wafer positional shifting can be more effectively prevented when the object is transported vertically during the manufacturing process. When the viscosity (ηF) is below the upper limit, the conductive paste can be placed on fine wiring with greater precision. The viscosity (ηD), the viscosity (ηE), and the viscosity (ηF) can be measured using a rheometer (for example, manufactured by Thermo Scientific, model: HAAKE) or the like. The conductive paste has good adhesion and is suitable for use as an adhesive. The conductive paste is particularly suitable for bonding substrates and chips. From the perspective of further improving the reliability of conduction, the conductive paste is preferably an anisotropic conductive paste. The conductive paste is suitable for electrical connection of electrodes. The conductive paste is suitable for obtaining a connection structure. The conductive paste is suitable for obtaining electronic components. The conductive paste is particularly suitable for obtaining an RFID inlay (the use of the conductive paste for obtaining an RFID inlay). The conductive paste is suitable for bonding and connecting a chip having electrodes on its surface to a substrate having wiring (antenna pattern) on its surface (the use of the conductive paste for bonding and connecting a chip having electrodes on its surface to a substrate having wiring (antenna pattern) on its surface). The conductive paste is preferably applied to a substrate having a surface tension of 30 mN / m to 50 mN / m. (Application of the conductive paste on a substrate having a surface tension of 30 mN / m to 50 mN / m). The conductive paste is preferably applied to a substrate having a surface tension of 0.50 mm. 2 The following wafers are bonded (for bonding a flat surface area of ​​0.50 mm 2 The following is the use of the above conductive paste for chip bonding). The conductive paste is preferably thermosetting, more preferably thermosetting anisotropic conductive paste. Hereinafter, each component contained in the conductive paste will be described. In this specification, "(meth)acrylate" refers to both acrylate and methacrylate. "(meth)acrylic acid" refers to both acrylic acid and methacrylic acid. "(meth)acryloyl" refers to both acryl and methacryloyl. <Curing compound> Examples of the curing compound include thermosetting compounds and photocuring compounds. The curing compound is preferably a thermosetting compound. The thermosetting compound is a compound that can be cured by heating. Examples of the thermosetting compound include (meth)acrylic compounds, oxetane compounds, epoxy compounds, episulfide compounds, phenol compounds, amino compounds, unsaturated polyester compounds, polyurethane compounds, silicone compounds, and polyimide compounds. The curing compound may be used alone or in combination of two or more. To enhance the curing reactivity of the conductive paste and improve the conductivity reliability of the resulting connection structure, the curable compound preferably comprises an epoxy compound or a (meth)acrylic compound, more preferably a (meth)acrylic compound. To enhance adhesion, the curable compound more preferably comprises a compound having a (meth)acryloyl group ((meth)acrylate). The (meth)acrylic compound may be a monofunctional (meth)acrylate or a multifunctional (meth)acrylate. The multifunctional (meth)acrylate may be a difunctional (meth)acrylate, a trifunctional (meth)acrylate, or a tetrafunctional or higher functional (meth)acrylate. The (meth)acrylic compound may have 100 or fewer (meth)acryloyl groups, 50 or fewer, or 10 or fewer. A single (meth)acrylic compound may be used alone, or two or more may be used in combination. Examples of the monofunctional (meth)acrylate include 2-(2-ethoxyethoxy)ethyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, lauryl (meth)acrylate, isobutyl (meth)acrylate, isodecyl (meth)acrylate, isooctyl (meth)acrylate, octyl / decyl (meth)acrylate, tridecyl (meth)acrylate, nonyl (meth)acrylate, caprolactone (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, and (2-methyl-2-ethyl-1,3-dioxolane) (meth)acrylate. -4-yl)methyl (meth)acrylate, (3-ethyloxetane-3-yl)methyl (meth)acrylate, methoxyethyl (meth)acrylate, methoxypolyethylene glycol (350) mono(meth)acrylate, methoxytriethylene glycol (meth)acrylate, alkoxylated tetrahydrofurfuryl (meth)acrylate, alkoxylated lauryl (meth)acrylate, dimethylacrylamide, diethylacrylamide, hydroxyethylacrylamide, dimethylaminopropylacrylamide, isopropylacrylamide, N-acryloyloxyethylhexahydrophthalimide, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Examples of the polyfunctional (meth)acrylate include 1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol (meth)acrylate, 1,9-nonanediol di(meth)acrylate, polyethylene glycol (200) di(meth)acrylate, tetraethylene glycol di(meth)acrylate, triethylene glycol (meth)acrylate, tripropylene glycol di(meth)acrylate, polyethylene glycol (400) di(meth)acrylate, dipropylene glycol di(meth)acrylate, alkoxylated hexanediol di(meth)acrylate, and dodecane diol. glycol di(meth)acrylate, polyethylene glycol (600) di(meth)acrylate, polypropylene glycol (700) (meth)acrylate, propoxylated (2) neopentyl glycol di(meth)acrylate, alkoxylated neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tris-(2-hydroxyethyl)isocyanurate tri(meth)acrylate, pentaerythritol tri(meth)acrylate, ethoxylated (3) trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, di-trimethylolpropane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate, etc. To adjust the viscosity of the conductive paste to an appropriate range, improve discharge properties, and allow for more precise placement of the conductive paste on the wiring, the (meth)acrylic compound preferably contains a polymerizable monomer having one (meth)acryloyl group (hereinafter sometimes referred to as "(A) polymerizable monomer"). To improve discharge properties and allow for more precise placement of the conductive paste on the wiring, the curable compound preferably contains a polymerizable monomer having one (meth)acryloyl group ((A) polymerizable monomer). The (A) polymerizable monomer is a monofunctional (meth)acrylate. The (A) polymerizable monomer is a polymerizable component that can be homopolymerized or copolymerized. From the perspective of improving the conductive reliability of the resulting connection structure, the polymerizable monomer (A) preferably has an aromatic skeleton or an alicyclic skeleton. The polymerizable monomer (A) may have an aromatic skeleton, an alicyclic skeleton, or both. The polymerizable monomer (A) may also include a polymerizable monomer having an aromatic skeleton and a polymerizable monomer having an alicyclic skeleton. Examples of the (A) polymerizable monomer having an aromatic skeleton include 2-phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, nonylphenoxy polyethylene glycol (meth)acrylate, ethoxylated (4) nonylphenol (meth)acrylate, and alkoxylated phenol (meth)acrylate. Examples of the polymerizable monomer (A) having an alicyclic skeleton include cyclohexyl (meth)acrylate, dimethyloltricyclodecane di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, isothiocyanate (meth)acrylate, 4-tert-butylcyclohexanol, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, pentamethylpiperidinyl (meth)acrylate, tetramethylpiperidinyl (meth)acrylate, acrylonitrile, and 3,3,5-trimethylcyclohexyl (meth)acrylate. From the viewpoint of improving the conduction reliability of the obtained connection structure, the polymerizable monomer (A) is preferably isothioyl (meth)acrylate. The molecular weight of the polymerizable monomer (A) is preferably 50 or greater, more preferably 100 or greater, even more preferably 150 or greater, and particularly preferably 200 or greater, and is preferably 1000 or less, more preferably less than 1000, even more preferably 900 or less, particularly preferably 800 or less, and most preferably 700 or less. If the molecular weight of the polymerizable monomer (A) is within this range, the viscosity of the conductive paste can be adjusted to an appropriate range, and the conductive reliability of the resulting connection structure can be further improved. Regarding the molecular weight of the above-mentioned (A) polymerizable monomer, when the structural formula of the above-mentioned (A) polymerizable monomer can be specified, it refers to the molecular weight that can be calculated based on the structural formula. In addition, when the structural formula of the above-mentioned (A) polymerizable monomer cannot be specified, the above-mentioned molecular weight refers to the weight average molecular weight. The above-mentioned weight average molecular weight represents the weight average molecular weight converted by gel permeation chromatography (GPC). Since the molecular weight of the above-mentioned (A) polymerizable monomer is relatively small, the structural formula can usually be specified. The above-mentioned weight average molecular weight can be measured using the following measuring device and measuring conditions. Measurement apparatus: Nihon Waters "Waters GPC System (Waters 2690 + Waters 2414 (RI))" Columns: Shodex GPC LF-G × 1, Shodex GPC LF-804 × 2 Mobile phase: THF 1.0 mL / min Sample concentration: 5 mg / mL Detector: Differential refractive index detector (RID) Standard substance: Polystyrene (manufactured by TOSOH, weight-average molecular weight: 620-590,000) The viscosity of the polymerizable monomer (A) at 25°C is preferably 1 mPa·s or higher, more preferably 2 mPa·s or higher, and preferably 50 mPa·s or lower, more preferably 45 mPa·s or lower. When the viscosity of the polymerizable monomer (A) at 25°C is above the lower limit and below the upper limit, the conductive paste can be more accurately deposited on fine wiring and exhibits improved wettability to the substrate. The viscosity of the polymerizable monomer (A) at 25° C. can be measured, for example, using an E-type viscometer at 25° C. and 5 rpm. Examples of the E-type viscometer include the TV22 Viscometer manufactured by Toki Sangyo Co., Ltd. The (meth)acrylic compound may contain a (meth)acrylic compound other than the polymerizable monomer (A). The (meth)acrylic compound other than the polymerizable monomer (A) may be used alone or in combination of two or more. From the perspective of improving the conductive reliability of the resulting connection structure, the (meth)acrylic compound other than the polymerizable monomer (A) preferably has two or more (meth)acrylic groups. The (meth)acrylic compound other than the polymerizable monomer (A) is preferably a multifunctional (meth)acrylate. The (meth)acrylic compound other than the polymerizable monomer (A) may have two (meth)acrylic groups, two or more (meth)acrylic groups, three or more (meth)acrylic groups, four or more (meth)acrylic groups, or ten or fewer (meth)acrylic groups. From the viewpoint of improving the conduction reliability of the obtained connection structure, the (meth)acrylic compound other than the above-mentioned (A) polymerizable monomer preferably contains urethane (meth)acrylate. The molecular weight of the urethane (meth)acrylate is preferably 1000 or greater, more preferably 1500 or greater, even more preferably 2000 or greater, even more preferably 3000 or greater, and particularly preferably 5000 or greater, and is preferably 30,000 or less, more preferably 25,000 or less, even more preferably 20,000 or less, and particularly preferably 18,000 or less. When the molecular weight of the urethane (meth)acrylate is above the lower limit and below the upper limit, adhesion and conduction reliability can be further improved. Regarding the molecular weight of the above-mentioned urethane (meth)acrylate, when the structural formula of the above-mentioned urethane (meth)acrylate can be specified, it refers to the molecular weight that can be calculated based on the structural formula. Furthermore, when the structural formula of the above-mentioned urethane (meth)acrylate cannot be specified, the above-mentioned molecular weight refers to the weight-average molecular weight. The above-mentioned weight-average molecular weight represents the weight-average molecular weight measured by gel permeation chromatography (GPC) and converted to polystyrene. The molecular weight of the above-mentioned urethane (meth)acrylate is preferably the weight-average molecular weight measured by gel permeation chromatography (GPC) and converted to polystyrene. The above-mentioned weight-average molecular weight can be measured using the following measuring apparatus and measuring conditions. Measurement apparatus: Nihon Waters "Waters GPC System (Waters 2690 + Waters 2414 (RI))" Columns: Shodex GPC LF-G × 1, Shodex GPC LF-804 × 2 Mobile phase: THF 1.0 mL / min Sample concentration: 5 mg / mL Detector: Differential refractive index detector (RID) Standard substance: Polystyrene (manufactured by TOSOH, weight-average molecular weight: 620-590,000) The viscosity of the urethane (meth)acrylate at 25° C. can be measured, for example, using an E-type viscometer at 25° C. and 5 rpm. Examples of the E-type viscometer include the TV22 Viscometer manufactured by Toki Sangyo Co., Ltd. The content of the curable compound in 100% by weight of the conductive paste is preferably 15% by weight or more, more preferably 20% by weight or more, and preferably 60% by weight or less, more preferably 55% by weight or less, and even more preferably 50% by weight or less. When the content of the curable compound is above the lower limit and below the upper limit, adhesion and conduction reliability can be further improved. In 100 wt % of the conductive paste, the content of the polymerizable monomer (A) is preferably 10 wt % or more, more preferably 15 wt % or more, and preferably 50 wt % or less, more preferably 45 wt % or less, further preferably 40 wt % or less, and particularly preferably 35 wt % or less. If the content of the polymerizable monomer (A) is above the lower limit and below the upper limit, the conductivity reliability of the obtained connection structure can be further improved. Furthermore, when the polymerizable monomer (A) includes a polymerizable monomer having an aromatic skeleton and a polymerizable monomer having an alicyclic skeleton, the content of the polymerizable monomer (A) represents the total content of the polymerizable monomer having an aromatic skeleton and the polymerizable monomer having an alicyclic skeleton. The content of the polymerizable monomer (A) in 100% by weight of the curable compound is preferably 10% by weight or more, more preferably 15% by weight or more, and preferably 50% by weight or less, more preferably 45% by weight or less. If the content of the polymerizable monomer (A) is above the lower limit and below the upper limit, the conduction reliability can be further improved. Furthermore, when the polymerizable monomer includes a polymerizable monomer having an aromatic skeleton and a polymerizable monomer having an alicyclic skeleton, the content of the polymerizable monomer represents the total content of the polymerizable monomer having an aromatic skeleton and the polymerizable monomer having an alicyclic skeleton. The content of the urethane (meth)acrylate in 100% by weight of the curable compound is preferably 15% by weight or more, more preferably 20% by weight or more, and preferably 50% by weight or less, more preferably 45% by weight or less. When the content of the urethane (meth)acrylate is above the lower limit and below the upper limit, adhesion can be improved and conduction reliability can be further enhanced. The combined content of the polymerizable monomer (A) and the urethane (meth)acrylate in 100% by weight of the curable compound is preferably 20% by weight or greater, more preferably 40% by weight or greater, and preferably 90% by weight or less, more preferably 80% by weight or less. If the combined content of the polymerizable monomer (A) and the urethane (meth)acrylate is above the lower limit and below the upper limit, the viscosity of the conductive paste can be adjusted to an appropriate range, improving adhesion and further enhancing conduction reliability. In the total of 100 weight % of the above-mentioned (A) polymerizable monomer and the above-mentioned urethane (meth) acrylate, the content of the above-mentioned (A) polymerizable monomer is preferably 15 weight % or more, more preferably 20 weight % or more, and preferably 55 weight % or less, more preferably 50 weight % or less. If the content of the above-mentioned (A) polymerizable monomer is above the above-mentioned lower limit and below the above-mentioned upper limit, the viscosity of the conductive paste can be adjusted to an appropriate range, the adhesion can be improved and the conduction reliability can be further improved. Furthermore, in the case where the above-mentioned (A) polymerizable monomer includes a polymerizable monomer having an aromatic skeleton and a polymerizable monomer having an alicyclic skeleton, the content of the above-mentioned (A) polymerizable monomer represents the total content of the polymerizable monomer having an aromatic skeleton and the polymerizable monomer having an alicyclic skeleton. <Conductive Filler> The conductive paste contains a plurality of conductive fillers. The conductive fillers are not particularly limited. They may be conductive particles or carbon fibers. In this specification, "containing a plurality of conductive fillers" means that the conductive paste contains two or more conductive fillers. These conductive fillers may be used alone or in combination. The specific gravity of the conductive filler is 1.5 to 4.0. The specific gravity of the conductive filler is preferably 1.8 or higher, more preferably 2.0 or higher, and preferably 3.8 or lower, more preferably 3.5 or lower. If the specific gravity of the conductive filler is above the lower limit and below the upper limit, segregation of the conductive filler in the conductive paste can be prevented even when the object is conveyed vertically during the manufacturing process, further improving the conductivity reliability of the resulting connection structure. The specific gravity of the conductive filler can be measured using, for example, "AccuPyc II 1340" manufactured by Micrometrics. The shape of the conductive filler is not particularly limited and may be spherical, or may be other than spherical, or may be flat. The conductive filler is preferably conductive particles. The conductive particles may be solder particles or metal particles. The metal particles may also be metal powder. The conductive particles may include substrate particles and a conductive portion disposed on the surface of the substrate particles. To further improve conduction reliability, the conductive particles preferably include substrate particles and a conductive portion disposed on the surface of the substrate particles. The particle size of the conductive particles is preferably 0.1 μm or larger, more preferably 1 μm or larger, and even more preferably 2 μm or larger, and is preferably 100 μm or smaller, more preferably 30 μm or smaller, and even more preferably 10 μm or smaller. When the particle size of the conductive particles is greater than the lower limit and less than the upper limit, the conduction reliability can be further improved. The particle size of the conductive particles is preferably an average particle size, more preferably a number average particle size. The average particle size of the conductive particles can be determined, for example, by observing 50 random conductive particles using an electron microscope or an optical microscope and calculating the average particle size of each conductive particle, or by performing laser diffraction particle size distribution measurement. For the above-mentioned conductive particles, when the particle size of the above-mentioned conductive particles is measured by observing 50 arbitrary conductive particles using an electron microscope or an optical microscope, the measurement can be performed, for example, in the following manner. The conductive particles are added to "Technovit 4000" manufactured by Kulzer Company in such a manner that the content thereof becomes 30% by weight, and are dispersed to prepare an embedding resin body for conductive particle inspection. An ion milling device ("IM4000" manufactured by Hitachi High-Technologies Company) is used to cut out a cross-section of the conductive particles near the center of the conductive particles dispersed in the embedding resin body for conductive particle inspection. Then, a field emission scanning electron microscope (FE-SEM) is used to set the image magnification to 25,000 times, randomly select 50 conductive particles, and observe each conductive particle. The circular equivalent diameter of each conductive particle is measured, and the arithmetic average thereof is taken as the particle size of the conductive particle. The coefficient of variation (CV value) of the particle size of the conductive particles is preferably 10% or less, more preferably 5% or less. If the coefficient of variation of the particle size of the conductive particles is below the upper limit, the conduction reliability can be further improved. The lower limit of the coefficient of variation (CV value) of the particle size of the conductive particles is not particularly limited. The coefficient of variation (CV value) of the particle size of the conductive particles can be 0% or more, or 1% or more. The above-mentioned coefficient of variation (CV value) can be measured as follows. CV value (%) = (ρ / Dn) × 100 ρ: Standard deviation of conductive particle size Dn: Average value of conductive particle size The conductive filler content is between 1.0% and 15% by weight per 100% by weight of the conductive paste. The conductive filler content is preferably between 2.0% and 5.0% by weight, and preferably between 13% and 10% by weight, respectively. When the conductive filler content is between the lower limit and the upper limit, conduction reliability can be further improved. The content of the conductive filler is preferably 2.0 parts by weight or greater, more preferably 3.0 parts by weight or greater, even more preferably 5.0 parts by weight or greater, and particularly preferably 7.0 parts by weight or greater, per 100 parts by weight of the curable compound in the conductive paste. The content of the conductive filler is preferably 35 parts by weight or less, more preferably 30 parts by weight or less, even more preferably 25 parts by weight or less, and particularly preferably 20 parts by weight or less, per 100 parts by weight of the curable compound in the conductive paste. When the content of the conductive filler in the conductive paste is above the lower limit and below the upper limit, conduction reliability can be further improved. The conductive filler preferably comprises a metal. Examples of the metal include gold, silver, copper, platinum, palladium, zinc, lead, aluminum, cobalt, indium, ruthenium, nickel, chromium, titanium, antimony, bismuth, germanium, and cadmium, as well as alloys thereof. Alternatively, tin-doped indium oxide (ITO) may be used as the metal. The metals may be used singly or in combination. To further reduce the connection resistance between electrodes, the conductive filler preferably comprises a tin-containing alloy, nickel, palladium, ruthenium, silver, copper, or gold, more preferably nickel or palladium. To improve the corrosion resistance of the conductive filler and maintain high conduction reliability, the conductive filler preferably comprises nickel or gold, more preferably nickel. To further improve the corrosion resistance of the conductive filler and maintain high conduction reliability, the conductive filler preferably contains nickel on its outer surface. When the conductive particles are metal particles, examples of the metal material of the metal particles include silver, copper, nickel, silicon, gold, titanium, and alloys such as solder. To further improve conduction reliability, the metal particles are preferably made of nickel or a nickel alloy, and more preferably, nickel or a nickel alloy. To further improve conduction reliability, the outer surface of the metal particles is preferably made of nickel or a nickel alloy. Hereinafter, the electroconductive particle provided with the substrate particle and the electroconductive part arrange|positioned on the surface of the said substrate particle is demonstrated in detail. (Substrate Particles) Examples of the substrate particles include resin particles, inorganic particles other than metal particles, organic-inorganic hybrid particles, and metal particles. The substrate particles are preferably substrate particles other than metal particles, more preferably resin particles, inorganic particles other than metal particles, or organic-inorganic hybrid particles. The substrate particles may also be core-shell particles comprising 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 substrate particles are preferably resin particles or organic-inorganic hybrid particles. Alternatively, the substrate particles may be resin particles or organic-inorganic hybrid particles. By using these preferred substrate particles, the effects of the present invention can be more effectively exerted. Various resins can be suitably used as the material for the resin particles. Examples of the material 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, 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 ether, polyacetal, polyimide, polyamide imide, polyetheretherketone, polyethersulfone, divinylbenzene polymers, and polymers obtained by polymerizing one or more polymerizable monomers having ethylenically unsaturated groups. The divinylbenzene polymer may also be a divinylbenzene-based copolymer. Examples of the divinylbenzene-based copolymer include divinylbenzene-styrene copolymers and divinylbenzene-(meth)acrylate copolymers. Since it is possible to design and synthesize resin particles having arbitrary compression characteristics suitable for conductive paste, and the hardness of the resin particles can be easily controlled within an appropriate range, the material of the above-mentioned resin particles is preferably a polymer formed by polymerizing one or more polymerizable monomers having multiple ethylenically unsaturated groups. When the resin particles are obtained by polymerizing a polymerizable monomer having an ethylenically unsaturated group, examples of the polymerizable monomer having an ethylenically unsaturated group include non-crosslinkable monomers and crosslinkable monomers. Examples of the non-crosslinking monomer include: styrene-based monomers such as styrene and α-methylstyrene; carboxyl group-containing monomers such as (meth)acrylic acid, maleic acid, and maleic anhydride; and alkyl (meth)acrylate compounds such as 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 (meth)acrylate, and isothioyl (meth)acrylate. ; (meth)acrylate compounds containing oxygen atoms such as 2-hydroxyethyl (meth)acrylate, glycerol (meth)acrylate, polyoxyethylene (meth)acrylate, and glycidyl (meth)acrylate; nitrile-containing monomers such as (meth)acrylonitrile; vinyl acetate, vinyl butyrate, vinyl laurate, and vinyl stearate; unsaturated hydrocarbons such as ethylene, propylene, isoprene, and butadiene; halogen-containing monomers such as trifluoromethyl (meth)acrylate, pentafluoroethyl (meth)acrylate, vinyl chloride, vinyl fluoride, and chlorostyrene, etc. Examples of the crosslinkable monomer include tetramethylolmethane tetra(meth)acrylate, tetramethylolmethane tri(meth)acrylate, tetramethylolmethane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol 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, and the like. Multifunctional (meth)acrylate compounds such as (meth)acrylate, (poly)tetramethylene glycol di(meth)acrylate, and 1,4-butanediol di(meth)acrylate; silane-containing monomers such as triallyl (iso)cyanurate, triallyl trimellitate, divinylbenzene, diallyl phthalate, diallylacrylamide, diallyl ether, γ-(meth)acryloyloxypropyltrimethoxysilane, trimethoxysilylstyrene, and vinyltrimethoxysilane. The resin particles can be obtained by polymerizing the polymerizable monomer having an ethylenically unsaturated group using a known method. Examples of such methods include suspension polymerization in the presence of a free radical polymerization initiator, and polymerization using non-crosslinked seed particles and swelling the monomer with a free radical polymerization initiator. When the substrate particles are inorganic particles other than metal particles or organic-inorganic hybrid particles, examples of the inorganic material used as the substrate particles include silica, alumina, barium titanate, zirconium oxide, and carbon black. Preferably, the inorganic material is not a metal. The silica particles are not particularly limited. For example, particles obtained by hydrolyzing a silicon compound having two or more hydrolyzable alkoxysilyl groups to form crosslinked polymer particles, followed by optional calcination, can be used. Examples of the organic-inorganic hybrid particles include those formed from a crosslinked alkoxysilyl polymer and an acrylic resin. The organic-inorganic hybrid particles are preferably core-shell organic-inorganic hybrid particles having a core and a shell disposed on the surface of the core. The core is preferably an organic core. The shell is preferably an inorganic shell. From the perspective of more effectively reducing the connection resistance between electrodes, the substrate particles are preferably organic-inorganic hybrid particles having an organic core and an inorganic shell disposed on the surface of the organic core. As the material of the organic core, the material of the resin particles mentioned above may be mentioned. The inorganic shell may be made of any of the inorganic materials listed above as the material for the substrate particles. Silicon dioxide is preferably used as the material for the inorganic shell. The inorganic shell is preferably formed by forming a shell of a metal alkoxide on the surface of the core using a sol-gel method and then calcining the shell. The metal alkoxide is preferably a silane alkoxide. The inorganic shell is preferably formed of a silane alkoxide. When the substrate particles are metal particles, examples of the metal material of the metal particles include silver, copper, nickel, silicon, gold, titanium, and alloys such as solder. The particle size of the substrate particles is preferably 0.01 μm or more, more preferably 0.05 μm or more, further preferably 0.5 μm or more, further preferably 1 μm or more, particularly preferably 3 μm or more, and preferably 50 μm or less, more preferably 30 μm or less, further preferably 20 μm or less, particularly preferably 10 μm or less. If the particle size of the substrate particles is above the lower limit, the conduction reliability becomes higher. Furthermore, when the conductive portion is formed on the surface of the substrate particles, it is not easy to agglomerate, and it is not easy to form agglomerated conductive particles. If the particle size of the substrate particles is below the upper limit, it is easy to fully compress the conductive particles, which can more effectively reduce the connection resistance between the electrodes connected via the conductive particles. The particle size of the substrate particles is preferably an average particle size, more preferably a number average particle size. The number average particle size of the substrate particles can be measured, for example, in the following manner. The conductive particles are added to "Technovit 4000" manufactured by Kulzer Company in such a manner that the content thereof becomes 30% by weight, and are dispersed to prepare an embedded resin body for substrate particle inspection. An ion milling device ("IM4000" manufactured by Hitachi High-Technologies Company) is used to cut out a cross-section of the conductive particles in a manner near the center of the substrate particles in the conductive particles dispersed in the embedded resin body for substrate particle inspection. Then, a field emission scanning electron microscope (FE-SEM) is used to set the image magnification to 25,000 times, randomly select 50 conductive particles, and observe the substrate particles of each conductive particle. The particle size of the substrate particles in each conductive particle is measured, and the arithmetic average is taken as the average particle size of the substrate particles. (Conductive portion) The conductive portion preferably comprises a metal. The metal constituting the conductive portion is not particularly limited. Examples of the metal include gold, silver, copper, platinum, palladium, zinc, lead, aluminum, cobalt, indium, ruthenium, nickel, chromium, titanium, antimony, bismuth, germanium, and cadmium, as well as alloys thereof. In addition, tin-doped indium oxide (ITO) can also be used as the metal. Only one of the metals may be used, or two or more may be used in combination. From the viewpoint of further lowering the connection resistance between the electrodes, preferably, it is an alloy comprising tin, nickel, palladium, ruthenium, silver, copper, or gold, more preferably nickel or palladium. From the viewpoint of more effectively improving conduction reliability, it is preferred that the conductive portion include nickel, and it is more preferred that the outer surface portion of the conductive portion include nickel. The nickel content in 100% by weight of the conductive portion comprising nickel is preferably 10% by weight or greater, more preferably 50% by weight or greater, even more preferably 60% by weight or greater, even more preferably 70% by weight or greater, and particularly preferably 90% by weight or greater. The nickel content in 100% by weight of the conductive portion comprising nickel may also be 99% by weight or less, 90% by weight or less, or 70% by weight or less. The conductive portion may be formed from a single layer. It may also be formed from multiple layers. That is, the conductive portion may have a laminated structure of two or more layers. When the conductive portion is formed from multiple layers, the metal constituting the outermost layer is preferably an alloy containing gold, silver, nickel, palladium, ruthenium, copper, or tin, more preferably nickel. When the metal constituting the outermost layer is one of these preferred metals, the connection resistance between the electrodes is further reduced. The method for forming the conductive portion on the surface of the above-mentioned substrate particles is not particularly limited. As the method for forming the above-mentioned conductive portion, for example, there can be cited: a method based on electroless plating, a method based on electroplating, a method based on physical collision, a method based on mechanochemical reaction, a method based on physical evaporation or physical adsorption, and a method of applying a paste comprising metal powder or metal powder and an adhesive to the surface of the substrate particles. The method for forming the above-mentioned conductive portion is preferably a method based on electroless plating, electroplating or physical collision. As the above-mentioned method based on physical evaporation, methods such as vacuum evaporation, ion plating and ion sputtering can be cited. In addition, in the above-mentioned method based on physical collision, for example, Theta Composer (manufactured by Deju Works Co., Ltd.) is used. The thickness of the conductive portion is preferably 0.005 μm or greater, more preferably 0.01 μm or greater, and preferably 10 μm or less, more preferably 1 μm or less, and even more preferably 0.3 μm or less. When the thickness of the conductive portion is above the lower limit and below the upper limit, sufficient conductivity can be achieved, and the conductive particles can be sufficiently deformed during connection without excessive hardening of the conductive particles. When the conductive portion is formed from multiple layers, the thickness of the outermost conductive portion is preferably 0.001 μm or greater, more preferably 0.01 μm or greater, and preferably 0.5 μm or less, more preferably 0.1 μm or less. If the thickness of the outermost conductive portion is above the lower limit and below the upper limit, the outermost conductive portion becomes uniform, corrosion resistance is sufficiently improved, and connection resistance between electrodes can be sufficiently reduced. The thickness of the conductive portion can be measured by observing a cross section of the conductive particle using a transmission electron microscope (TEM), for example. Core material: The conductive particles preferably have a plurality of protrusions on the outer surface of the conductive portion. In most cases, an oxide film is formed on the surface of the electrode connected by the conductive particles. When using conductive particles having protrusions on the surface of the conductive portion, the oxide film can be effectively removed by arranging the conductive particles between the electrodes and pressing them. Therefore, the electrode and the conductive portion are in contact more reliably, and the connection resistance between the electrodes becomes lower. Furthermore, when connecting between the electrodes, the filler between the conductive particles and the electrode can be effectively removed by the protrusions of the conductive particles. Therefore, the conduction reliability between the electrodes becomes higher. Examples of methods for forming the protrusions include: a method in which a core material is attached to the surface of a substrate particle and then a conductive portion is formed by electroless plating; a method in which a conductive portion is formed on the surface of a substrate particle by electroless plating, a core material is attached, and then a conductive portion is formed by electroless plating. Alternatively, a method in which, without using the core material, a conductive portion is formed on the substrate particle by electroless plating, a plating layer is deposited in the form of a protrusion on the surface of the conductive portion, and then a conductive portion is formed by electroless plating. Examples of methods for attaching the core material to the surface of substrate particles include: adding the core material to a dispersion of the substrate particles, causing the core material to aggregate and adhere to the substrate particle surfaces via van der Waals forces; and adding the core material to a container containing the substrate particles, causing the core material to adhere to the substrate particle surfaces via mechanical action such as the rotation of the container. From the perspective of controlling the amount of attached core material, a method for attaching the core material to the substrate particle surfaces is preferably a method for aggregating and adhering the core material to the substrate particle surfaces in the dispersion. As materials constituting the core material, conductive materials and non-conductive materials may be mentioned. Examples of the conductive material include metals, metal oxides, conductive non-metals such as graphite, and conductive polymers. Examples of the conductive polymer include polyacetylene. Examples of the non-conductive material include silicon dioxide, aluminum oxide, titanium oxide, tungsten carbide, and zirconium oxide. From the perspective of further improving the reliability of conduction between electrodes, the core material is preferably a metal. The metal is not particularly limited. Examples of the metal include gold, silver, copper, platinum, zinc, iron, lead, tin, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, germanium, and cadmium, as well as alloys containing two or more metals such as tin-lead alloys, tin-copper alloys, tin-silver alloys, tin-lead-silver alloys, and tungsten carbide. From the perspective of further improving the conduction reliability between the electrodes, the metal is preferably nickel, copper, silver, or gold. The metal may be the same as or different from the metal constituting the conductive portion. The shape of the core material is not particularly limited. The core material is preferably in a block shape. Examples of the core material include a particle-shaped block, an aggregated block formed by agglomeration of a plurality of fine particles, and an amorphous block. The particle size (average particle size) of the core material is preferably 0.001 μm or more, more preferably 0.05 μm or more, and preferably 0.9 μm or less, more preferably 0.2 μm or less. If the particle size of the core material is above the lower limit and below the upper limit, the connection resistance between the electrodes can be effectively reduced. The particle size of the core material is preferably an average particle size, more preferably a number average particle size. The particle size of the core material can be determined, for example, by observing 50 random core materials using an electron microscope or an optical microscope and calculating the average particle size of each core material, or by performing laser diffraction particle size distribution measurement. <Curing Agent> From the perspective of curing the curable compound containing the polymerizable monomer (A), the curing agent is preferably a polymerization initiator. Examples of the polymerization initiator include photopolymerization initiators and thermal polymerization initiators. One or more polymerization initiators may be used. From the perspective of curing the curable compound by heating, the polymerization initiator preferably comprises a thermal polymerization initiator. The thermal polymerization initiator preferably comprises a thermal free radical polymerization initiator, and is preferably a thermal free radical polymerization initiator. Examples of the thermal free radical polymerization initiator include peroxide-based free radical polymerization initiators, azo-based free radical polymerization initiators, and redox-based free radical polymerization initiators. Examples of the azo radical polymerization initiator include azobisisobutyronitrile, azobiscyclohexanecarbonitrile, and azobisdimethylvaleronitrile. Examples of the peroxide-based free radical polymerization initiator include diacyl-based free radical polymerization initiators, peroxyester-based free radical polymerization initiators, dialkyl-based free radical polymerization initiators, percarbonate-based free radical polymerization initiators, and ketone peroxide-based free radical polymerization initiators. Examples of the diacyl-based free radical polymerization initiator include lauryl peroxide and benzoyl peroxide. Examples of the peroxyester-based free radical polymerization initiator include t-butyl perbenzoate, t-butyl peroxyacetate, t-butyl peroxypivalate, and t-butyl peroxy-2-ethylhexanoate. Examples of the dialkyl-based free radical polymerization initiator include dicumyl peroxide and di-t-butyl peroxide. Examples of the percarbonate-based free radical polymerization initiator include diisopropyl peroxydicarbonate. Examples of the ketone peroxide-based free radical polymerization initiator include methyl ethyl ketone peroxide. The redox-based free radical polymerization initiator comprises, for example, a peroxide and a reducing agent or a metal-containing compound. Specific examples of the redox-based free radical polymerization initiator include mixtures of benzoyl peroxide and organic amines, mixtures of the peroxyester-based free radical polymerization initiator and a reducing agent such as a thiol, and mixtures of methyl ethyl ketone peroxide and an organic cobalt salt. From the viewpoint of improving reactivity and storage stability, the polymerization initiator preferably includes a peroxide-based radical polymerization initiator. From the perspective of improving reactivity and storage stability, the content of the hardener (polymerization initiator) in 100 wt % of the conductive paste is preferably 0.1 wt % or more, more preferably 0.3 wt % or more, and further preferably 0.5 wt % or more, and preferably 5 wt % or less, more preferably 4 wt % or less, and further preferably 3 wt % or less. The content of the hardener (polymerization initiator) is preferably 0.3 parts by weight or more, more preferably 0.5 parts by weight or more, and even more preferably 0.7 parts by weight or more, relative to 100 parts by weight of the curable compound in the conductive paste, and is preferably 6 parts by weight or less, more preferably 5 parts by weight or less, and even more preferably 4 parts by weight or less. When the content of the hardener (polymerization initiator) is above the lower limit and below the upper limit, reactivity and storage stability can be improved. <Other Ingredients> The conductive paste may contain ingredients other than the curable compound, the curing agent, and the plurality of conductive fillers. Other ingredients include solvents, inorganic fillers, organic fillers, colorants, polymerization inhibitors, chain transfer agents, antioxidants, UV absorbers, defoamers, leveling agents, surfactants, lubricants, anti-blocking agents, waxes, masking agents, deodorants, fragrances, preservatives, antimicrobial agents, antistatic agents, and adhesion-imparting agents. (RFID Inlay and RFID Inlay Manufacturing Method) The RFID inlay of the present invention comprises a substrate having wiring on its surface, a chip having electrodes on its surface, and a bonding portion that bonds the substrate and chip together. In the RFID inlay of the present invention, the bonding portion is made of the conductive paste. In the RFID inlay of the present invention, the wiring and electrodes are electrically connected via the conductive filler in the bonding portion. FIG1 is a cross-sectional view schematically showing an RFID inlay using the conductive paste according to the first embodiment of the present invention. RFID inlay 81 shown in Figure 1 comprises a substrate 82 having wiring on its surface, a chip 83 having electrodes on its surface, and a bonding portion 84 that bonds substrate 82 and chip 83. Bonding portion 84 is made of a conductive paste containing conductive filler 1. Bonding portion 84 is preferably formed by curing the conductive paste containing conductive filler 1. The substrate 82 has wiring 82 a on its surface (upper surface). The chip 83 has electrodes 83 a on its surface (lower surface). The wiring 82 a and the electrodes 83 a are electrically connected via the conductive filler 1 in the adhesive portion 84 . The manufacturing method of the RFID inlay of the present invention includes the following steps (1) to (3). (1) A first configuration step, which is to configure the conductive paste on the surface of a substrate having wiring on the surface. (2) A second configuration step, which is to configure a chip having electrodes on the surface of the conductive paste on the surface opposite to the substrate. (3) A subsequent step, which is to heat and pressurize the conductive paste to form a bonding portion that bonds the substrate and the chip, and to electrically connect the wiring and the electrodes using the conductive filler in the bonding portion. The RFID inlay and the method for manufacturing the RFID inlay of the present invention use a specific conductive paste, so the adhesion between the substrate and the chip can be improved. In addition, the RFID inlay and the method for manufacturing the RFID inlay of the present invention use a specific conductive paste, so the conductive paste can be arranged on the wiring with high precision. Furthermore, the RFID inlay and the method for manufacturing the RFID inlay of the present invention use a specific conductive paste, so when the conveyed object is conveyed in the vertical direction during the manufacturing step, the position shift of the chip and the segregation of the conductive filler can be prevented. As a result, the conduction reliability can be improved. Furthermore, in the method for manufacturing the RFID inlay, the conductive paste can be arranged on the surface of the substrate, and the chip and the conductive paste can also be arranged on the surface of the substrate. In the above-described RFID inlay manufacturing method, the substrate is preferably in a long strip shape. In the first placement step, the second placement step, and the subsequent step, the RFID inlay is manufactured by conveying the long strip substrate in a roll-to-roll manner. In this case, multiple RFID inlays can be manufactured continuously, further improving RFID inlay manufacturing efficiency. In the manufacturing method of the above-mentioned RFID inlay, the above-mentioned substrate can be transported in the horizontal direction, the vertical direction, or the horizontal and vertical directions by a roll-to-roll method in the above-mentioned first configuration step, the above-mentioned second configuration step, and the above-mentioned subsequent step. In the manufacturing method of the above-mentioned RFID inlay, the above-mentioned substrate can be transported in an oblique direction by a roll-to-roll method in the above-mentioned first configuration step, the above-mentioned second configuration step, and the above-mentioned subsequent step. In the manufacturing method of the above-mentioned RFID inlay, since the above-mentioned conductive paste is used, when the conveyed object is conveyed in the vertical direction by a roll-to-roll method, the positional displacement of the chip and the segregation of the conductive filler can also be prevented. Furthermore, the above-mentioned substrate can be conveyed in a state where the above-mentioned conductive paste is disposed on the surface of the substrate, or can be conveyed in a state where the above-mentioned chip and the above-mentioned conductive paste are disposed. When a roll-to-roll method is used, the transport speed of the substrate is not particularly limited. Examples of a method for disposing the conductive paste include coating with a dispenser, screen printing, and discharge with an inkjet device. The heating temperature in the subsequent step is preferably 100° C. or higher, more preferably 150° C. or higher, and preferably 400° C. or lower, more preferably 300° C. or lower, and even more preferably 250° C. or lower. If the heating temperature in the subsequent step is above the lower limit and below the upper limit, good electrical connection between the chip and the wiring (antenna pattern) can be achieved. The pressing pressure in the bonding step is preferably 0.5 N or more, more preferably 1 N or more, and preferably 3.5 N or less, more preferably 3 N or less, and further preferably 2.5 N or less. If the pressing pressure in the bonding step is greater than the lower limit and less than the upper limit, the adhesion between the substrate and the wafer can be improved, and the conduction reliability can be improved. The heating and pressing time in the subsequent step is not particularly limited and may be 2 seconds or longer, 15 seconds or shorter, or 10 seconds or shorter. The above-mentioned RFID inlay can also be cut into a specific size as needed, and can also be used after cutting. It is preferred to use a plurality of the above-mentioned bonding parts to bond a plurality of the above-mentioned chips on a long strip substrate. It is also possible to arrange a stack of a plurality of the above-mentioned chips and the above-mentioned bonding parts on a long strip substrate. It is preferred that in the above-mentioned first configuration step, the above-mentioned conductive paste is configured at a plurality of locations on the surface of the long strip substrate. It is preferred that in the above-mentioned second configuration step, a plurality of chips are used to configure the above-mentioned chips on the surface opposite to the above-mentioned substrate side of each of the conductive pastes configured at a plurality of locations. It is also possible to bond the above-mentioned chips to a long strip substrate using the above-mentioned bonding parts and then cut the long strip substrate. The substrate is not particularly limited. It is preferably a circuit substrate. Examples of the circuit substrate include resin films, flexible printed circuit boards, rigid flexible substrates, glass substrates, and paper substrates. The substrate may be a resin substrate, a glass substrate, or a paper substrate. The substrate has wiring (antenna pattern) on its surface. The wiring (antenna pattern) is formed on the surface of the substrate. The substrate preferably has a base material and wiring (antenna pattern) arranged on the surface of the base material. Examples of the substrate material include resin, glass, and paper. Examples of the resin include PET (polyethylene terephthalate), PP (polypropylene), and PVC (polyvinyl chloride). The paper may also be impregnated with an epoxy resin or a phenolic resin. To further improve adhesion and enable roll-to-roll manufacturing of RFID inlays, the substrate material is preferably resin or paper, more preferably PET (polyethylene terephthalate) or paper. The substrate may be resin, glass, or paper. Examples of the wiring (antenna pattern) include gold wiring, nickel wiring, tin wiring, aluminum wiring, silver wiring, SUS wiring, copper wiring, molybdenum wiring, and tungsten wiring. Aluminum wiring is preferred for improved sensitivity in the UHF band (860 MHz to 920 MHz). From the viewpoint of suppressing deformation of the substrate due to heat when mounting a chip (eg, IC chip) and improving flexibility, the thickness of the substrate is preferably 20 μm or more, more preferably 30 μm or more, and preferably 200 μm or less, more preferably 100 μm or less. The shapes of the substrate and base material are not particularly limited. To facilitate roll-to-roll manufacturing of RFID inlays, the substrate and base material are preferably in the form of long strips. The length of the substrate and base material is not particularly limited. The length of the substrate and base material can be greater than 1 m, greater than 10 m, less than 5000 m, or less than 1000 m. The surface tension of the substrate (base material) is preferably 30 mN / m or higher, more preferably 32 mN / m or higher, and even more preferably 34 mN / m or higher, and is preferably 50 mN / m or lower, more preferably 48 mN / m or lower, and even more preferably 45 mN / m or lower. If the surface tension of the substrate (base material) is above the lower limit and below the upper limit, adhesion can be further improved. The conductive paste of the present invention is suitable for application to substrates (base materials) having a surface tension above the lower limit and below the upper limit. The surface tension of the substrate can be measured according to JIS K6768 using the following method. A cotton swab is dipped into the JIS standard liquid and applied to the substrate. The surface tension is determined based on the shape of the coating film two seconds after application. Examples of the wafer include semiconductor wafers (IC wafers) and the like. The wafer has electrodes on its surface. Examples of these electrodes include metal electrodes such as gold, nickel, tin, aluminum, silver, SUS, copper, molybdenum, and tungsten. To further enhance conduction reliability, these electrodes are preferably copper or gold, more preferably copper. The number of electrodes per wafer is not particularly limited and may be 1 or more, 4 or more, 20 or less, or 10 or less. The shape of the wafer is not particularly limited and may be rectangular, triangular, or circular. The plane area of ​​the above chip is preferably 0.04 mm 2 Above, preferably 0.09 mm 2 More than 0.16 mm 2 Above, and preferably 0.50 mm 2 Below, preferably 0.40 mm 2 Below, more preferably 0.30 mm 2 If the wafer's planar area is greater than or equal to the lower limit, the conductive paste can be precisely applied to fine wiring. If the wafer's planar area is less than or equal to the upper limit, conductive reliability can be maintained even when the RFID inlay is exposed to high temperature and high humidity for extended periods of time. The conductive paste of the present invention is suitable for bonding relatively small wafers. The present invention will be described in detail below with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. Prepare the following materials. Curing compound: Isobutyl acrylate ((A) polymerizable monomer, molecular weight: 208) Polyester urethane acrylate ("UN-353" manufactured by Negami Industries, molecular weight (weight average molecular weight): 5000) Tricyclodecane dimethanol diacrylate ("IRR214" manufactured by DAICEL-ALLNEX, molecular weight: 304) Bisphenol A epoxy resin ("EXA850CRP" manufactured by DIC Corporation, molecular weight (weight average molecular weight): 340) Conductive filler: Conductive particles A (conductive particles having substrate particles and conductive portions on the surfaces of the substrate particles (substrate particles: resin particles; conductive portion: nickel), average particle size: 5 μm, specific gravity: 2.0) Conductive particles B (conductive particles having substrate particles and conductive portions on the surfaces of the substrate particles (substrate particles: resin particles; conductive portion: nickel), average particle size: 5 μm, specific gravity: 1.5) Conductive particles C (conductive particles having substrate particles and conductive portions on the surfaces of the substrate particles (substrate particles: resin particles; conductive portion: nickel), average particle size: 5 μm, specific gravity: 4.0) Conductive particles D (conductive particles having substrate particles and conductive portions on the surfaces of the substrate particles (substrate particles: resin particles; conductive portion: 75% by weight of silver and 25% by weight of nickel), average particle size: 5 μm, specific gravity: 2.3) Conductive particles E (conductive particles having substrate particles and conductive portions on the surfaces of the substrate particles (substrate particles: resin particles; conductive portion: nickel), average particle size: 5 Conductive Particles F (Conductive Particles Having a Base Particle and a Conductive Portion on the Surface of the Base Particle (Base Particles: Resin Particles; Conductive Portion: Nickel), Average Particle Size: 5 μm, Specific Gravity: 6.0) Conductive Particles G (Metal Particles (Copper), Average Particle Size: 5 μm, Specific Gravity: 8.9) Conductive Particles H (Metal Particles (Nickel), Average Particle Size: 5 μm, Specific Gravity: 8.9) Hardener: PEROYL L (diacyl-based free radical polymerization initiator (lauryl peroxide)) manufactured by NOF Corporation; Novacure HXA3922HP (latent hardener for epoxy resin) manufactured by Asahi Kasei Corporation Inorganic filler: Silicon dioxide (PM-20L manufactured by Tokuyama) Chip: IC chip (gold electrodes, NXP "UCODE8", flat surface area: 0.22 mm 2 ) Substrate: PET film (long strip, resin film with aluminum wiring operating in the UHF band (860 MHz to 920 MHz), surface tension: 43 mN / m) (Example 1) (1) Preparation of Conductive Paste The materials shown in Table 1 below were mixed in the amounts shown in Table 1 below and stirred using a planetary stirring device ("Defoaming Stirring Taro" manufactured by Thinky) to obtain a conductive paste (anisotropic conductive paste). (2) Production of RFID inlays: The conductive paste obtained is applied to the PET film by the jet dispensing method to form a conductive paste layer (adhesive layer) (first configuration step). Then, on the surface of the conductive paste layer (adhesive layer) opposite to the substrate side, the IC chip is laminated in such a way that the wiring on the surface of the PET film and the electrodes on the surface of the chip face each other (second configuration step). Thereafter, heat pressing is performed under the conditions of an upper heating tool of 180°C, a lower heating tool of 175°C, a pressure of 2 N, and a pressing time of 7 seconds to harden the conductive paste layer (adhesive layer) and form a bonding portion. In addition, the wiring on the surface of the PET film and the electrodes on the surface of the chip are electrically connected by the conductive filler in the bonding portion to obtain a connected structure (bonding step). Furthermore, the above-mentioned first configuration step, the above-mentioned second configuration step, and the above-mentioned bonding step are performed using the "DDA40000" manufactured by Muhlbauer (roll-to-roll method, with a portion in the conveying path having a portion for conveying the conveyed object in the vertical direction). The obtained connection structure was cut into pieces of 5 cm×1.5 cm using a “DCL30000” manufactured by Muhlbauer to obtain an RFID inlay. (Examples 2 to 10 and Comparative Examples 1 to 9) Conductive pastes and RFID inlays were obtained in the same manner as in Example 1 except that the ingredients and amounts of the conductive pastes were changed as shown in Tables 1, 3, 5, and 7. (Evaluation) (1) Viscosity The viscosity (ηA) of the conductive paste at 25°C and 5 rpm and the viscosity (ηB) of the conductive paste at 25°C and 0.5 rpm were measured using an E-type viscometer ("TV22 Viscometer" manufactured by Toki Sangyo Co., Ltd.). The thixotropic index (ratio (ηB / ηA)) was determined based on the obtained results. In addition, the ingredients of the conductive paste other than the conductive filler in each embodiment and comparative example were mixed in the amounts shown in Tables 1, 3, 5, and 7, and stirred using a planetary stirring device ("Defoaming Stirring Taro" manufactured by Thinky Co., Ltd.) to obtain a composition containing the conductive paste material other than the conductive filler. The viscosity (ηC) of the composition other than the conductive filler in the conductive paste was measured using an E-type viscometer ("TV22 Viscometer" manufactured by Toki Sangyo Co., Ltd.) (2) Dispensing performance using a jet dispenser (dispensing performance of conductive paste) The bonding areas of the 50 RFID inlays obtained were observed using a microscope to see if the conductive paste was applied to the wiring in an appropriate amount (with high precision). The dispensing performance using a jet dispenser was evaluated based on the following criteria. [Judgment criteria based on the ejection performance of the jet dispenser] ○: The conductive paste is accurately placed on the wiring in all RFID inlays ×: The conductive paste is not accurately placed on the wiring in at least one RFID inlay (3) Chip Position Misalignment Prevention: The bonding portions of the 50 RFID inlays obtained were observed using a microscope to determine whether the chip was properly positioned in the center of the wiring (the center of the conductive paste) during vertical transport during the manufacturing process. The chip position misalignment prevention was evaluated based on the following criteria. [Criteria for determining chip position shift prevention] ○: The chip is properly positioned in the center of the wiring in all RFID inlays ×: The chip is not properly positioned in the center of the wiring in at least one RFID inlay (4) Prevention of Segregation of Conductive Fillers For each of the 50 RFID inlays obtained, the wafers were peeled from the wiring and the number of conductive fillers on the electrodes on the wafer surface was counted using a microscope. Prevention of segregation of conductive fillers was determined based on the following criteria. [Criteria for determining the ability to prevent the segregation of conductive fillers] ○: The number of conductive fillers on all electrodes is 3 or more ×: The number of conductive fillers on at least one electrode is 2 or less (5) Conductivity Reliability: 50 RFID inlays were placed at 60°C and 90% RH (high temperature and high humidity environment) for 250 hours. They were then placed in a dark box that blocked external radio waves. Peak sensitivity at 25°C in the UHF band (860 MHz to 920 MHz) was measured using a frequency reader ("Tagformance Pro" manufactured by Voyantic). Conductivity reliability (frequency characteristics) was determined according to the following criteria. [Conduction reliability judgment criteria] ○: The peak sensitivity of all RFID inlays does not reach -18 dBm ×: The peak sensitivity of at least one RFID inlay is above -18 dBm The composition of the conductive paste and the results are shown in Tables 1 to 8 below. [Table 1] [Table 2] [Table 3] [Table 4] [Table 5] [Table 6] [Table 7] [Table 8] 1: Conductive filler 81: RFID inlay 82: Substrate with wiring on the surface 82a: Wiring 83: Wafer with electrodes on the surface 83a: Electrode 84: Adhesive FIG1 is a cross-sectional view schematically showing an RFID inlay using the conductive paste according to the first embodiment of the present invention. 1: Conductive filler 81:RFID Inlay 82: Substrate with wiring on the surface 82a: Wiring 83: Chip with electrodes on the surface 83a: Electrode 84: Continuation

Claims

1. A conductive paste comprising a curing compound, a curing agent, and a plurality of conductive fillers, wherein the specific gravity of the conductive fillers is 1.5 to 4.0, the content of the conductive fillers in 100% by weight of the conductive paste is 1.0% to 15% by weight, the ratio of the viscosity of the conductive paste at 25°C and 0.5 rpm to its viscosity at 25°C and 5 rpm is 1.5 to 4.5, and the viscosity of the conductive paste at 25°C and 5 rpm is 8 Pa·s to 50 Pa·s.

2. The conductive paste of claim 1, wherein the curing compound comprises a (meth)acrylic compound.

3. The conductive paste as requested in item 1 or 2, wherein the conductive filler is conductive particles and the particle size of the conductive particles is more than 1 μm and less than 10 μm.

4. The conductive paste of claim 3, wherein the conductive particles comprise substrate particles and conductive portions disposed on the surface of the substrate particles.

5. The conductive paste, as requested in item 1 or 2, is applied to a substrate with a surface tension of 30 mN / m or more and 50 mN / m or less.

6. The conductive paste as requested in item 1 or 2, used to obtain an RFID inlay.

7. An RFID inlay comprising a substrate having wiring on its surface, a chip having electrodes on its surface, and a bonding portion for bonding the substrate and the chip, wherein the bonding portion is made of conductive paste as claimed in any one of claims 1 to 6, and the wiring and the electrodes are electrically connected by the conductive filler in the bonding portion.

8. A method for manufacturing an RFID inlay, comprising: The first configuration step involves configuring a conductive paste, as described in any one of claims 1 to 6, on the surface of a substrate having wiring on its surface. The second configuration step involves placing a wafer with electrodes on the surface of the conductive paste opposite to the substrate side; and the next step involves heating and pressurizing the conductive paste to form an attachment portion that connects the substrate and the wafer, and using the conductive filler in the attachment portion to electrically connect the wiring to the electrodes.

9. The method for manufacturing an RFID inlay as claimed in claim 8, wherein the substrate is elongated, and the RFID inlay is manufactured by conveying the elongated substrate in a roll-to-roll manner in the first configuration step, the second configuration step, and the connecting step.

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