Conductive paste, RFID inlay and manufacturing method of RFID inlay

Abstract

Provided is a conductive paste with which it is possible to increase discharge stability, increase conduction reliability even when mounted at a relatively low temperature, and maintain high conduction reliability even when cooling and heating are repeated.　The conductive paste according to the present invention contains a curable compound, a curing agent, and a plurality of conductive fillers, wherein, when the conductive paste is heated from 25 °C to 150 °C at a rate of temperature increase of 10 °C / minute and differential scanning calorimetry is performed, the heat generation start temperature is 80 °C or higher, the heat generation peak top temperature is 85 °C to 105 °C, and the heat generation end temperature is 110 °C or lower.

Description

[Technical Field]

[0001] The present invention relates to a conductive paste containing a conductive filler, and also to an RFID inlay using the conductive paste and a method for manufacturing an RFID inlay. [Background technology]

[0002] RFID (Radio Frequency Identification) inlays, which enable contactless data transmission and reception, are widely used in contactless RFID tags, contactless RFID cards, etc. In particular, UHF (Ultra High Frequency) band (860 MHz to 960 MHz) RFID inlays have attracted attention due to their long communication distances, and UHF band RFID inlays are used for a variety of items and purposes, such as commuter passes, inventory management, distribution management, and history management.

[0003] In RFID inlays, a conductive paste containing a conductive filler and a binder resin is sometimes used to bond and connect a chip having electrodes on its surface to a substrate having wiring (antenna pattern) on its surface.

[0004] Patent Document 1 below discloses an adhesive that can be used for electronic components. The adhesive is an acrylic adhesive composition containing a radical initiator having a 10-hour half-life temperature of 80°C or less, a vinylene-containing oligomer, and at least one diluent. The adhesive can be snap-cured at low temperatures, and the usable time of the adhesive at room temperature is 24 hours or more.

[0005] Patent Document 2 listed below discloses a conductive adhesive containing a polymerizable acrylic compound, an organic peroxide, and solder particles, in which the one-minute half-life temperature of the organic peroxide is lower than the solidus temperature of the solder particles. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-144018 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-124330 Summary of the Invention [Problem to be solved by the invention]

[0007] When conventional conductive paste is discharged by a jet dispensing method, liquid accumulation may occur and the amount of droplets discharged may change.

[0008] Furthermore, in order to improve the adhesion between the chip and the substrate, a conductive paste is sometimes placed not only at the bonding area between the chip and the substrate but also around the chip, and then the conductive paste is cured by applying heat and pressure after a fillet is formed, and then the chip is mounted. In this case, the fillet (especially the end of the fillet) may not be heated sufficiently, and the conductive paste may not be cured sufficiently. As a result, there is a problem that the electrical conductivity reliability of the resulting electronic component is reduced.

[0009] On the other hand, if the chip and the substrate are bonded and connected by thermocompression at high temperatures in order to sufficiently harden the conductive paste, the substrate may be deformed, resulting in deformation of the wiring on the surface of the substrate and a decrease in the electrical conductivity reliability of the resulting electronic component.

[0010] Furthermore, in electronic components using conventional conductive pastes, the reliability of electrical continuity may decrease when cooling and heating are repeated.

[0011] The present invention aims to provide a conductive paste that can improve discharge stability, improve conductivity reliability even when mounted at relatively low temperatures, and maintain high conductivity reliability even when repeatedly cooled and heated. Another object of the present invention is to provide an RFID inlay using the conductive paste and a method for manufacturing an RFID inlay. [Means for solving the problem]

[0012] The present specification discloses the following conductive paste, RFID inlay, and method for manufacturing the RFID inlay.

[0013] Item 1. A conductive paste comprising a curable compound, a curing agent, and a plurality of conductive fillers, wherein when the conductive paste is heated from 25°C to 150°C at a temperature increase rate of 10°C / min and subjected to differential scanning calorimetry, the heat generation start temperature is 80°C or higher, the heat generation peak top temperature is 85°C or higher and 105°C or lower, and the heat generation end temperature is 110°C or lower.

[0014] Item 2. The conductive paste according to Item 1, wherein the absolute value of the difference between the heat generation start temperature and the heat generation end temperature in the differential scanning calorimetry is 13°C or less.

[0015] Item 3. The conductive paste according to Item 1 or 2, wherein the conductive paste has a cure shrinkage rate of 10% or less when cured by heating at 130°C for 10 minutes.

[0016] Item 4. The conductive paste according to any one of Items 1 to 3, wherein the curable compound includes a (meth)acrylic compound.

[0017] Item 5. The conductive paste according to any one of Items 1 to 4, wherein the curable compound contains a polymerizable monomer having one (meth)acryloyl group, and the content of the polymerizable monomer in 100% by weight of the curable compound is 50% by weight or less.

[0018] Item 6. The conductive paste according to any one of Items 1 to 5, which is used to obtain an RFID inlay.

[0019] Item 7. An RFID inlay comprising a substrate having wiring on its surface, a chip having electrodes on its surface, and an adhesive portion bonding the substrate and the chip, wherein the material of the adhesive portion is the conductive paste according to any one of Items 1 to 6, and the wiring and the electrodes are electrically connected by the conductive filler in the adhesive portion.

[0020] Item 8. A method for manufacturing an RFID inlay, comprising: a first arrangement step of arranging the conductive paste according to any one of Items 1 to 6 on a surface of a substrate having wiring on its surface; a second arrangement step of arranging a chip having electrodes on its surface on the surface of the conductive paste opposite the substrate side; and a bonding step of forming an adhesive joint that bonds the substrate and the chip with the conductive paste by heating and pressurizing the conductive paste, and electrically connecting the wiring and the electrodes with the conductive filler in the adhesive joint.

[0021] Item 9. A method for manufacturing an RFID inlay according to Item 8, wherein the substrate is long and the RFID inlay is manufactured by transporting the long substrate using a roll-to-roll method in the first placement process, the second placement process, and the bonding process. [Effects of the Invention]

[0022] The conductive paste according to the present invention is a conductive paste containing a curable compound, a curing agent, and a plurality of conductive fillers, and when the conductive paste is heated from 25°C to 150°C at a temperature increase rate of 10°C / min and subjected to differential scanning calorimetry, the heat generation start temperature is 80°C or higher, the heat generation peak top temperature is 85°C or higher and 105°C or lower, and the heat generation end temperature is 110°C or lower. Because the conductive paste according to the present invention has the above-mentioned configuration, it is possible to improve discharge stability, improve conductivity reliability even when mounted at a relatively low temperature, and maintain high conductivity reliability even when cooling and heating are repeated. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a cross-sectional view schematically showing an RFID inlay using a conductive paste according to a first embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention will be described in detail below.

[0025] (Conductive paste) The conductive paste according to the present invention is a conductive paste containing a curable compound, a curing agent, and a plurality of conductive fillers. When the conductive paste according to the present invention is heated from 25°C to 150°C at a temperature increase rate of 10°C / min and subjected to differential scanning calorimetry, the heat generation start temperature is 80°C or higher, the heat generation peak top temperature is 85°C to 105°C, and the heat generation end temperature is 110°C or lower.

[0026] The conductive paste according to the present invention has the above-mentioned configuration, and therefore can improve discharge stability. In particular, it can improve discharge stability using a jet dispenser. Furthermore, the conductive paste according to the present invention has the above-mentioned configuration, and therefore can be sufficiently cured at a relatively low temperature (for example, 160°C to 180°C). Furthermore, the conductive paste according to the present invention can improve conduction reliability even when mounted at a relatively low temperature. Furthermore, the conductive paste according to the present invention has the above-mentioned configuration, and therefore can maintain high conduction reliability (improve thermal cycling characteristics) even when the connection structure (electronic component) is repeatedly cooled and heated. In other words, the conductive paste according to the present invention can improve conduction reliability even when mounted at a relatively low temperature and when cooling and heating are repeatedly performed.

[0027] The conductive paste is heated from 25°C to 150°C at a temperature increase rate of 10°C / min, and differential scanning calorimetry (DSC) is performed. In the differential scanning calorimetry, the conductive paste according to the present invention has an exothermic onset temperature of 80°C or higher, an exothermic peak top temperature of 85°C to 105°C, and an exothermic end temperature of 110°C or lower. In this specification, the exothermic onset temperature refers to the temperature at which the amount of heat generated starts to increase from the baseline. In this specification, the exothermic end temperature refers to the temperature at which, after reaching the exothermic peak top, the amount of heat generated decreases to 1% of the amount of heat generated at the exothermic peak top.

[0028] The differential scanning calorimetry (DSC) can be performed as follows. A differential scanning calorimeter is prepared. 5 mg of the conductive paste is placed in a dedicated aluminum pan (aluminum container) and the lid is closed using a dedicated jig. The dedicated aluminum pan containing the conductive paste and an empty aluminum pan (reference) are placed in a heating unit, and heating is performed in a nitrogen atmosphere from 25°C to 150°C at a temperature increase rate of 10°C / min, and the reverse heat flow and non-reverse heat flow are observed. The exothermic peak observed in the non-reverse heat flow is taken as the exothermic peak of the conductive paste. An example of the differential scanning calorimeter is the "TA7000" manufactured by Hitachi High-Tech Science Corporation.

[0029] From the viewpoint of further improving the storage stability and discharge stability of the conductive paste and further improving the conductivity reliability even when mounted at a relatively low temperature, the heat generation initiation temperature in the differential scanning calorimetry measurement is preferably 82°C or higher, more preferably 85°C or higher. There is no particular upper limit to the heat generation initiation temperature. The heat generation initiation temperature may be 105°C or lower, 103°C or lower, 100°C or lower, or 90°C or lower.

[0030] From the viewpoint of further improving the conductivity reliability even when mounted at a relatively low temperature, the exothermic peak top temperature in the differential scanning calorimetry measurement is preferably 88°C or higher, more preferably 90°C or higher, and is preferably 103°C or lower, more preferably 100°C or lower.

[0031] From the viewpoint of further improving the electrical conductivity reliability even when mounted at a relatively low temperature, the heat generation end temperature in the differential scanning calorimetry is preferably 108°C or less, more preferably 105°C or less. There is no particular limitation on the lower limit of the heat generation end temperature. The heat generation end temperature may be 90°C or more, or may be 95°C or more.

[0032] In the differential scanning calorimetry, the absolute value of the difference between the heat generation start temperature and the heat generation end temperature is preferably 1° C. or more, more preferably 3° C. or more, even more preferably 5° C. or more, and is preferably 25° C. or less, more preferably 20° C. or less, even more preferably 15° C. or less, and particularly preferably 13° C. or less. When the absolute value of the difference between the heat generation start temperature and the heat generation end temperature is equal to or more than the above lower limit and equal to or less than the above upper limit, the storage stability of the conductive paste can be improved, and the conductivity reliability can be further improved even when the paste is mounted at a relatively low temperature.

[0033] In the differential scanning calorimetry, examples of a method for adjusting the exotherm onset temperature, exotherm peak top temperature, and exotherm end temperature to fall within the preferred ranges include the following: A method using a preferred curable compound described below. A method using a preferred curing agent described below. A method adjusting the content of the curable compound. A method adjusting the content of the curing agent.

[0034] In the differential scanning calorimetry, it is preferable that only one exothermic peak is observed. In the differential scanning calorimetry, it is preferable that two or more exothermic peaks are not observed.

[0035] The conductive paste according to the present invention is in a paste form at 25° C. The conductive paste is used by being discharged at, for example, 20° C. to 50° C. The conductive paste according to the present invention is preferably used by being discharged using a jet dispenser.

[0036] The conductive paste has good adhesive properties, is suitable for use as an adhesive, and is particularly suitable for use in bonding a substrate and a chip.

[0037] From the viewpoint of further improving the conduction reliability, the conductive paste is preferably an anisotropic conductive paste. The conductive paste is preferably used for electrically connecting electrodes. The conductive paste is preferably used for obtaining a connection structure. The conductive paste is preferably used for obtaining electronic components. The conductive paste is particularly preferably used for obtaining an RFID inlay (use of the conductive paste for obtaining an RFID inlay). The conductive paste is preferably used for bonding and connecting a chip having electrodes on its surface to a substrate having wiring (antenna pattern) on its surface (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).

[0038] The conductive paste is preferably applied to a substrate having a surface tension of 30 mN / m or more and 50 mN / m or less (use of the conductive paste on a substrate having a surface tension of 30 mN / m or more and 50 mN / m or less). 2 It is preferable to use it for bonding chips with a planar area of ​​0.50 mm or less. 2 (Use of the above conductive paste to bond the chip, which is below).

[0039] The conductive paste is preferably thermosetting, and is preferably a thermosetting conductive paste, more preferably a thermosetting anisotropic conductive paste.

[0040] From the viewpoint of further improving the electrical conductivity reliability, the curing shrinkage rate when the conductive paste is heated at 130°C for 10 minutes to be cured is preferably 13% or less, more preferably 10% or less, even more preferably 9% or less, and particularly preferably 7% or less. There is no particular limitation on the lower limit of the curing shrinkage rate. The curing shrinkage rate may be 0%, 0% or more, or 3% or more.

[0041] The cure shrinkage is measured, for example, as follows. The conductive paste is applied to a glass substrate, and the specific gravity of the conductive paste (before curing) is measured using an AccuPyc II 1340 manufactured by Micrometrics. The conductive paste is then heated at 130°C for 10 minutes to form a cured product of the conductive paste. The specific gravity of the resulting cured product of the conductive paste is measured using an AccuPyc II 1340 manufactured by Micrometrics. The cure shrinkage is calculated using the following formula.

[0042] Curing shrinkage rate = (specific gravity of cured conductive paste - specific gravity of conductive paste) x 100 / specific gravity of conductive paste

[0043] Each component contained in the conductive paste will be described below.

[0044] In this specification, "(meth)acrylate" refers to acrylate and methacrylate, "(meth)acrylic" refers to acrylic and methacrylic, and "(meth)acryloyl" refers to acryloyl and methacryloyl.

[0045] <Curable compound> Examples of the curable compound include a thermosetting compound and a photocurable compound. The curable 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. Only one type of the curable compound may be used, or two or more types may be used in combination.

[0046] From the viewpoint of more effectively exerting the effects of the present invention, the curable compound preferably contains an epoxy compound or a (meth)acrylic compound, more preferably a (meth)acrylic compound. From the viewpoint of improving adhesiveness, the curable compound more preferably contains a compound having a (meth)acryloyl group ((meth)acrylate).

[0047] The (meth)acrylic compound may be a monofunctional (meth)acrylate or a polyfunctional (meth)acrylate. The polyfunctional (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 less (meth)acryloyl groups, 50 or less, or 10 or less. The (meth)acrylic compound may be used alone or in combination of two or more.

[0048] 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, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, (3-ethyloxene 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.

[0049] Examples of the polyfunctional (meth)acrylate include 1,3-butylene glycol 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, dodecanediol di(meth)acrylate, and the like. 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, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate.

[0050] From the viewpoint of adjusting the viscosity of the conductive paste within a preferred range and improving the ejection stability, the (meth)acrylic compound preferably contains a polymerizable monomer having one (meth)acryloyl group (hereinafter, sometimes referred to as "(A) polymerizable monomer"). From the viewpoint of improving the ejection stability, 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.

[0051] From the viewpoint of further improving the electrical conductivity reliability, the (A) polymerizable monomer preferably has an aromatic skeleton or an alicyclic skeleton. The (A) polymerizable monomer may have an aromatic skeleton, an alicyclic skeleton, or both an aromatic skeleton and an alicyclic skeleton. The (A) polymerizable monomer may include a polymerizable monomer having an aromatic skeleton and a polymerizable monomer having an alicyclic skeleton.

[0052] 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.

[0053] Examples of the polymerizable monomer (A) having an alicyclic skeleton include cyclohexyl (meth)acrylate, dimethylol-tricyclodecane di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, isobornyl (meth)acrylate, 4-tert-butylcyclohexanol, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, pentamethylpiperidyl (meth)acrylate, tetramethylpiperidyl (meth)acrylate, acrylomorpholine, N-acryloyloxyethyl hexahydrophthalimide, and 3,3,5-trimethylcyclohexyl (meth)acrylate.

[0054] From the viewpoint of further improving the conduction reliability even when mounted at a relatively low temperature, the polymerizable monomer (A) is preferably isobornyl (meth)acrylate.

[0055] The molecular weight of the (A) polymerizable monomer is preferably 50 or more, more preferably 100 or more, even more preferably 150 or more, and particularly preferably 200 or more, 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. When the molecular weight of the (A) polymerizable monomer is within the above range, the viscosity of the conductive paste can be adjusted to a suitable range, and the conductivity reliability can be further improved.

[0056] The molecular weight of the (A) polymerizable monomer refers to a molecular weight that can be calculated from the structural formula when the structural formula of the (A) polymerizable monomer can be identified. Furthermore, when the structural formula of the (A) polymerizable monomer cannot be identified, the molecular weight refers to a weight-average molecular weight. The weight-average molecular weight refers to a weight-average molecular weight measured by gel permeation chromatography (GPC) in terms of polystyrene. Since the (A) polymerizable monomer has a relatively small molecular weight, its structural formula can generally be identified. The weight-average molecular weight can be measured using the following measuring device and under the following measuring conditions.

[0057] Measurement equipment: Waters GPC System (Waters 2690 + Waters 2414 (RI)) manufactured by Japan Waters Columns: Shodex GPC LF-G x 1, Shodex GPC LF-804 x 2 Mobile phase: THF 1.0mL / min Sample concentration: 5mg / mL Detector: Refractive index detector (RID) Standard material: Polystyrene (TOSOH Corporation, weight average molecular weight: 620-590,000)

[0058] The (meth)acrylic compound may contain a (meth)acrylic compound other than the (A) polymerizable monomer. The (meth)acrylic compound other than the (A) polymerizable monomer may be used alone or in combination of two or more.

[0059] From the viewpoint of further improving the electrical conductivity reliability, the (meth)acrylic compound other than the (A) polymerizable monomer preferably has two or more (meth)acryloyl groups. The (meth)acrylic compound other than the (A) polymerizable monomer is preferably a polyfunctional (meth)acrylate. The (meth)acrylic compound other than the (A) polymerizable monomer may have two (meth)acryloyl groups, two or more, three or more, four or more, or ten or less.

[0060] From the viewpoint of further improving the conduction reliability, the (meth)acrylic compound other than the (A) polymerizable monomer preferably contains a urethane (meth)acrylate.

[0061] The molecular weight of the urethane (meth)acrylate is preferably 1000 or more, more preferably 1500 or more, even more preferably 2000 or more, even more preferably 3000 or more, and particularly preferably 5000 or more, and is preferably 30000 or less, more preferably 25000 or less, even more preferably 20000 or less, and particularly preferably 18000 or less. When the molecular weight of the urethane (meth)acrylate is equal to or more than the above lower limit and equal to or less than the above upper limit, the adhesiveness can be further improved and the conduction reliability can be further improved.

[0062] When the structural formula of the urethane (meth)acrylate can be identified, the molecular weight of the urethane (meth)acrylate refers to a molecular weight that can be calculated from the structural formula. When the structural formula of the urethane (meth)acrylate cannot be identified, the molecular weight refers to a weight average molecular weight. The weight average molecular weight refers to a weight average molecular weight measured by gel permeation chromatography (GPC) in terms of polystyrene. The molecular weight of the urethane (meth)acrylate is preferably a weight average molecular weight measured by gel permeation chromatography (GPC) in terms of polystyrene. The weight average molecular weight can be measured using the following measuring device and under the following measuring conditions.

[0063] Measurement equipment: Waters GPC System (Waters 2690 + Waters 2414 (RI)) manufactured by Japan Waters Columns: Shodex GPC LF-G x 1, Shodex GPC LF-804 x 2 Mobile phase: THF 1.0mL / min Sample concentration: 5mg / mL Detector: Refractive index detector (RID) Standard material: Polystyrene (TOSOH Corporation, weight average molecular weight: 620-590,000)

[0064] 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 equal to or more than the lower limit and equal to or less than the upper limit, adhesiveness can be further improved and conduction reliability can be further improved.

[0065] In 100% by weight of the conductive paste, the content of the (A) polymerizable monomer 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, even more preferably 40% by weight or less, and particularly preferably 35% by weight or less. When the content of the (A) polymerizable monomer is equal to or greater than the above lower limit and equal to or less than the above upper limit, the conductivity reliability can be further improved. Note that when the (A) polymerizable monomer contains a polymerizable monomer having an aromatic skeleton and a polymerizable monomer having an alicyclic skeleton, the content of the (A) polymerizable monomer refers to the total content of the polymerizable monomer having an aromatic skeleton and the polymerizable monomer having an alicyclic skeleton.

[0066] The content of the (A) polymerizable monomer in 100% by weight of the curable compound is preferably 10% by weight or more, more preferably 15% by weight or more, and even more preferably 20% by weight or more, and is preferably 65% ​​by weight or less, more preferably 60% by weight or less, and even more preferably 50% by weight or less. When the content of the (A) polymerizable monomer is equal to or greater than the above-mentioned lower limit and equal to or less than the above-mentioned upper limit, the viscosity of the conductive paste can be adjusted within a suitable range, thereby improving adhesion and further improving conductivity reliability. Note that 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 refers to the total content of the polymerizable monomer having an aromatic skeleton and the polymerizable monomer having an alicyclic skeleton.

[0067] 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 80% by weight or less, more preferably 70% by weight or less. When the content of the urethane (meth)acrylate is equal to or more than the lower limit and equal to or less than the upper limit, the adhesiveness can be improved and the conduction reliability can be further improved.

[0068] The total content of the (A) polymerizable monomer and the urethane (meth)acrylate in 100% by weight of the curable compound is preferably 20% by weight or more, more preferably 40% by weight or more, and preferably 90% by weight or less, more preferably 80% by weight or less. When the total content of the (A) polymerizable monomer and the urethane (meth)acrylate is equal to or more than the lower limit and equal to or less than the upper limit, the viscosity of the conductive paste can be adjusted within a suitable range, and the adhesiveness and the conduction reliability can be further improved.

[0069] The content of the (A) polymerizable monomer is preferably 15% by weight or more, more preferably 20% by weight or more, and preferably 55% by weight or less, more preferably 50% by weight or less, based on a total of 100% by weight of the (A) polymerizable monomer and the urethane (meth)acrylate. When the content of the (A) polymerizable monomer is equal to or greater than the above-mentioned lower limit and equal to or less than the above-mentioned upper limit, the viscosity of the conductive paste can be adjusted within a suitable range, thereby improving adhesion and further improving conductivity reliability. When the (A) polymerizable monomer includes a polymerizable monomer having an aromatic skeleton and a polymerizable monomer having an alicyclic skeleton, the content of the (A) polymerizable monomer refers to the total content of the polymerizable monomer having an aromatic skeleton and the polymerizable monomer having an alicyclic skeleton.

[0070] <Conductive filler> The conductive paste contains a plurality of conductive fillers. The conductive fillers are not particularly limited. The conductive fillers 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. Only one type of the conductive fillers may be used, or two or more types may be used in combination.

[0071] The shape of the conductive filler is not particularly limited, and may be spherical, or may be a shape other than spherical, such as flat.

[0072] The conductive filler is preferably a conductive particle. The conductive particle may be a solder particle or a metal particle. The metal particle may be a metal powder. The conductive particle may include a base particle and a conductive portion disposed on the surface of the base particle. From the viewpoint of further improving the conduction reliability, the conductive particle preferably includes a base particle and a conductive portion disposed on the surface of the base particle.

[0073] The particle diameter of the conductive particles is preferably 0.1 μm or more, more preferably 1 μm or more, and even more preferably 2 μm or more, and is preferably 100 μm or less, more preferably 30 μm or less, and even more preferably 10 μm or less. When the particle diameter of the conductive particles is equal to or greater than the above lower limit and equal to or less than the above upper limit, the electrical conductivity reliability can be further improved.

[0074] The particle size of the conductive particles is preferably an average particle size, more preferably a number average particle size, which can be determined, for example, by observing 50 random conductive particles with 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.

[0075] The particle diameter of the conductive particles can be measured by observing 50 random conductive particles under an electron microscope or optical microscope, for example, as follows. The conductive particles are added to Kulzer's Technovit 4000 so that the content is 30% by weight, and dispersed to prepare a resin embedding body for conductive particle inspection. An ion milling machine (Hitachi High-Technologies Corporation's IM4000) is used to cut out a cross section of the conductive particles so that it passes through the center of the conductive particles dispersed in the resin embedding body for conductive particle inspection. Then, a field emission scanning electron microscope (FE-SEM) is used, with the image magnification set to 25,000x, to randomly select 50 conductive particles and observe each conductive particle. The equivalent circle diameter of each conductive particle is measured, and the arithmetic average is used to determine the particle diameter of the conductive particles.

[0076] The coefficient of variation (CV value) of the particle diameter of the conductive particles is preferably 10% or less, more preferably 5% or less. When the coefficient of variation of the particle diameter of the conductive particles is equal to or less than the upper limit, the electrical conductivity reliability can be further improved. There is no particular limitation on the lower limit of the coefficient of variation (CV value) of the particle diameter of the conductive particles. The coefficient of variation (CV value) of the particle diameter of the conductive particles may be 0% or more, or may be 1% or more.

[0077] The coefficient of variation (CV value) can be measured as follows.

[0078] CV value (%) = (ρ / Dn) × 100 ρ: Standard deviation of the particle size of the conductive particles Dn: average particle diameter of conductive particles

[0079] The content of the conductive filler in 100% by weight of the conductive paste is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, and is preferably 80% by weight or less, more preferably 60% by weight or less, even more preferably 40% by weight or less, particularly preferably 20% by weight or less, and most preferably 10% by weight or less. When the content of the conductive filler is equal to or more than the lower limit and equal to or less than the upper limit, the conduction reliability can be further improved.

[0080] The content of the conductive filler relative to 100 parts by weight of the curable compound in the conductive paste is preferably 2 parts by weight or more, more preferably 3 parts by weight or more, even more preferably 5 parts by weight or more, and particularly preferably 7 parts by weight or more. The content of the conductive filler relative to 100 parts by weight of the curable compound in the conductive paste 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. When the content of the conductive filler in the conductive paste is equal to or greater than the lower limit and equal to or less than the upper limit, the conduction reliability can be further improved.

[0081] The conductive filler preferably contains 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. Tin-doped indium oxide (ITO) may also be used as the metal. The metal may be used alone or in combination of two or more.

[0082] From the viewpoint of further reducing the connection resistance between electrodes, the conductive filler preferably contains a tin-containing alloy, nickel, palladium, ruthenium, silver, copper, or gold, and more preferably contains nickel or palladium. From the viewpoint of improving the corrosion resistance of the conductive filler and maintaining high conduction reliability, the conductive filler preferably contains nickel or gold, and more preferably contains nickel. From the viewpoint of improving the corrosion resistance of the conductive filler and maintaining high conduction reliability, it is particularly preferable that the conductive filler contains nickel on the outer surface.

[0083] When the conductive particles are metal particles, examples of the metal particles include silver, copper, nickel, silicon, gold, titanium, and alloys such as solder. From the viewpoint of more effectively improving the electrical conductivity reliability, the material of the metal particles preferably contains nickel or a nickel alloy, and more preferably the material of the metal particles is nickel or a nickel alloy. From the viewpoint of more effectively improving the electrical conductivity reliability, the outer surface portion of the metal particles preferably contains nickel or a nickel alloy.

[0084] Hereinafter, the conductive particle including a base particle and a conductive portion disposed on the surface of the base particle will be described in detail.

[0085] (base material particles) Examples of the base particles include resin particles, inorganic particles excluding 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 particles may be core-shell particles having 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.

[0086] The base particles are more preferably resin particles or organic-inorganic hybrid particles, and may be either resin particles or organic-inorganic hybrid particles. By using these preferred base particles, the effects of the present invention are more effectively exhibited.

[0087] Various resins are suitable for use as the material 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, 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, polyimide, polyamide-imide, polyether ether ketone, polyether sulfone, divinylbenzene polymer, and polymers obtained by polymerizing one or more of various polymerizable monomers having an ethylenically unsaturated group. The divinylbenzene polymer may be a divinylbenzene copolymer. Examples of the divinylbenzene copolymer include a divinylbenzene-styrene copolymer and a divinylbenzene-(meth)acrylic acid ester copolymer.

[0088] Since it is possible to design and synthesize resin particles having any compression characteristics suitable for a conductive paste, and the hardness of the resin particles can be easily controlled within a suitable range, it is preferable that the material of the resin particles is a polymer obtained by polymerizing one or more polymerizable monomers having multiple ethylenically unsaturated groups.

[0089] 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 or a crosslinkable monomer.

[0090] Examples of the non-crosslinkable 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; 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 isobornyl (meth)acrylate; and 2-hydroxyethyl Examples of the monomer include oxygen atom-containing (meth)acrylate compounds such as (meth)acrylate, glycerol (meth)acrylate, polyoxyethylene (meth)acrylate, and glycidyl (meth)acrylate; nitrile-containing monomers such as (meth)acrylonitrile; acid vinyl ester compounds such as vinyl acetate, vinyl butyrate, vinyl laurate, and vinyl stearate; unsaturated hydrocarbons such as ethylene, propylene, isoprene, and butadiene; and halogen-containing monomers such as trifluoromethyl (meth)acrylate, pentafluoroethyl (meth)acrylate, vinyl chloride, vinyl fluoride, and chlorostyrene.

[0091] 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)propane ... Examples of suitable (meth)acrylates include polyfunctional (meth)acrylate compounds such as pyrene glycol di(meth)acrylate, (poly)tetramethylene glycol di(meth)acrylate, and 1,4-butanediol di(meth)acrylate; and silane-containing monomers such as triallyl (iso)cyanurate, triallyl trimellitate, divinylbenzene, diallyl phthalate, diallyl acrylamide, diallyl ether, γ-(meth)acryloxypropyltrimethoxysilane, trimethoxysilylstyrene, and vinyltrimethoxysilane.

[0092] The resin particles can be obtained by polymerizing the polymerizable monomer having an ethylenically unsaturated group by a known method, such as a suspension polymerization method in the presence of a radical polymerization initiator, or a method in which non-crosslinked seed particles are used to swell and polymerize the monomer together with the radical polymerization initiator.

[0093] 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. It is preferable that the inorganic material is not metal. The particles formed from silica are not particularly limited, but examples include particles obtained by hydrolyzing a silicon compound having two or more hydrolyzable alkoxysilyl groups to form crosslinked polymer particles, followed by calcination as necessary. Examples of the organic-inorganic hybrid particles include organic-inorganic hybrid particles formed from a crosslinked alkoxysilyl polymer and an acrylic resin.

[0094] 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 viewpoint of more effectively reducing the connection resistance between electrodes, the base particle is preferably an organic-inorganic hybrid particle having an organic core and an inorganic shell disposed on the surface of the organic core.

[0095] Examples of the material for the organic core include the materials for the resin particles described above.

[0096] Examples of materials for the inorganic shell include the inorganic substances listed as materials for the base particle described above. The material for the inorganic shell is preferably silica. The inorganic shell is preferably formed by forming a shell-like substance from a metal alkoxide on the surface of the core by a sol-gel method and then firing the shell-like substance. The metal alkoxide is preferably a silane alkoxide. The inorganic shell is preferably formed from a silane alkoxide.

[0097] 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, titanium, and alloys such as solder.

[0098] The particle diameter of the base particle is preferably 0.01 μm or more, more preferably 0.05 μm or more, even more preferably 0.5 μm or more, even more preferably 1 μm or more, particularly preferably 3 μm or more, and preferably 50 μm or less, more preferably 30 μm or less, even more preferably 20 μm or less, particularly preferably 10 μm or less. When the particle diameter of the base particle is equal to or greater than the lower limit, the electrical conductivity reliability is further improved. Furthermore, when forming a conductive portion on the surface of the base particle, aggregation is less likely to occur, and aggregated conductive particles are less likely to be formed. When the particle diameter of the base particle is equal to or less than the upper limit, the conductive particles are easily compressed sufficiently, and the connection resistance between electrodes connected via the conductive particles can be further effectively reduced.

[0099] The particle diameter of the base particles is preferably an average particle diameter, and more preferably a number-average particle diameter. The number-average particle diameter of the base particles can be measured, for example, as follows: The conductive particles are added to Kulzer's Technovit 4000 so that the content is 30% by weight, and dispersed to prepare a resin embedding body for base particle inspection. An ion milling machine (Hitachi High-Technologies Corporation's IM4000) is used to cut out a cross section of the conductive particles dispersed in the resin embedding body for base particle inspection, passing through the vicinity of the center of the base particle. Then, using a field emission scanning electron microscope (FE-SEM) with an image magnification set to 25,000x, 50 conductive particles are randomly selected, and the base particle of each conductive particle is observed. The particle diameter of the base particle in each conductive particle is measured, and the arithmetic average is calculated to determine the average particle diameter of the base particles.

[0100] (Conductive part) The conductive portion preferably contains 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. Tin-doped indium oxide (ITO) may 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 reducing the connection resistance between electrodes, tin-containing alloys, nickel, palladium, ruthenium, silver, copper, or gold are preferred, and nickel or palladium is more preferred.

[0101] From the viewpoint of more effectively improving the conduction reliability, it is preferable that the conductive portion contains nickel, and it is more preferable that the outer surface portion of the conductive portion contains nickel.

[0102] The nickel content in 100% by weight of the nickel-containing conductive portion is preferably 10% by weight or more, more preferably 50% by weight or more, even more preferably 60% by weight or more, even more preferably 70% by weight or more, and particularly preferably 90% by weight or more. The nickel content in 100% by weight of the nickel-containing conductive portion may be 99% by weight or less, 90% by weight or less, or 70% by weight or less.

[0103] The conductive portion may be formed of one layer. The conductive portion may be formed of multiple layers. That is, the conductive portion may have a laminated structure of two or more layers. When the conductive portion is formed of multiple layers, the metal constituting the outermost layer is preferably an alloy containing gold, silver, nickel, palladium, ruthenium, copper, or tin, and 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.

[0104] The method for forming the conductive portion on the surface of the base particle is not particularly limited. Examples of methods for forming the conductive portion include electroless plating, electroplating, physical collision, mechanochemical reaction, physical vapor deposition or physical adsorption, and coating the surface of the base particle with a metal powder or a paste containing a metal powder and a binder. The method for forming the conductive portion is preferably electroless plating, electroplating, or physical collision. Examples of physical vapor deposition methods include vacuum deposition, ion plating, and ion sputtering. Furthermore, the physical collision method uses, for example, a sheeter composer (manufactured by Tokuju Manufacturing Co., Ltd.).

[0105] The thickness of the conductive portion 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 even more preferably 0.3 μm or less. When the thickness of the conductive portion is equal to or greater than the lower limit and equal to or less than the upper limit, sufficient conductivity is obtained, and the conductive particles do not become too hard, allowing the conductive particles to be sufficiently deformed during connection.

[0106] When the conductive portion is formed of multiple layers, the thickness of the conductive portion of the outermost layer is preferably 0.001 μm or more, more preferably 0.01 μm or more, and preferably 0.5 μm or less, more preferably 0.1 μm or less. When the thickness of the conductive portion of the outermost layer is equal to or greater than the above lower limit and equal to or less than the above upper limit, the conductive portion of the outermost layer becomes uniform, the corrosion resistance is sufficiently high, and the connection resistance between electrodes can be sufficiently low.

[0107] The thickness of the conductive portion can be measured by observing the cross section of the conductive particle using, for example, a transmission electron microscope (TEM).

[0108] Core material: The conductive particles preferably have a plurality of protrusions on the outer surface of the conductive portion. An oxide film is often formed on the surface of the electrodes connected by the conductive particles. When conductive particles having protrusions on the surface of the conductive portion are used, the oxide film can be effectively removed by placing the conductive particles between the electrodes and pressing them together. This ensures more reliable contact between the electrodes and the conductive portion, further reducing the connection resistance between the electrodes. Furthermore, when connecting the electrodes, the protrusions of the conductive particles can effectively remove the filler between the conductive particles and the electrodes. This further increases the reliability of conduction between the electrodes.

[0109] Methods for forming the protrusions include a method of adhering a core material to the surface of a base particle and then forming a conductive portion by electroless plating, and a method of forming a conductive portion on the surface of a base particle by electroless plating, then adhering a core material, and then further forming a conductive portion by electroless plating, etc. Alternatively, to form the protrusions, a method may be used in which, without using the core material, a conductive portion is formed on the base particle by electroless plating, and then a protruding plating is deposited on the surface of the conductive portion, and then a conductive portion is formed by electroless plating, etc.

[0110] Examples of methods for adhering a core substance to the surface of a base particle include a method of adding a core substance to a dispersion of base particles and accumulating and adhering the core substance to the surface of the base particle by van der Waals forces, and a method of adding a core substance to a container containing base particles and adhering the core substance to the surface of the base particle by mechanical action such as rotating the container.From the viewpoint of controlling the amount of core substance to be adhered, the method for adhering a core substance to the surface of a base particle is preferably a method of adhering the core substance to the surface of the base particle by accumulating and adhering the core substance to the surface of the base particle in a dispersion.

[0111] The materials constituting the core material include conductive materials and non-conductive materials. Examples of the conductive materials include conductive non-metals such as metals, metal oxides, and graphite, and conductive polymers. Examples of the conductive polymers include polyacetylene. Examples of the non-conductive materials include silica, alumina, titanium oxide, tungsten carbide, and zirconia. From the viewpoint of further improving the reliability of conduction between electrodes, it is preferable that the core material be a metal.

[0112] 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 composed of two or more metals, such as tin-lead alloys, tin-copper alloys, tin-silver alloys, tin-lead-silver alloys, and tungsten carbide. From the viewpoint of further improving the reliability of conduction between 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.

[0113] The shape of the core material is not particularly limited. The core material is preferably in the form of a mass. Examples of the core material include particulate masses, aggregates formed by aggregating multiple microparticles, and amorphous masses.

[0114] 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. When the particle size of the core material is equal to or more than the lower limit and equal to or less than the upper limit, the connection resistance between electrodes can be effectively reduced.

[0115] The particle size of the core substance is preferably an average particle size, more preferably a number average particle size, which can be determined, for example, by observing 50 random core substances with an electron microscope or an optical microscope and calculating the average particle size of each core substance, or by performing laser diffraction particle size distribution measurement.

[0116] <Curing agent> From the viewpoint of curing the curable compound containing the polymerizable monomer (A), the curing agent is preferably a polymerization initiator. Examples of the polymerization initiator include a photopolymerization initiator and a thermal polymerization initiator. The polymerization initiator may be used alone or in combination of two or more.

[0117] From the viewpoint of curing the curable compound by heating, the polymerization initiator preferably includes a thermal polymerization initiator. The thermal polymerization initiator preferably includes a thermal radical polymerization initiator, and is preferably a thermal radical polymerization initiator. Examples of the thermal radical polymerization initiator include a peroxide radical polymerization initiator, an azo radical polymerization initiator, and a redox radical polymerization initiator.

[0118] Examples of the azo radical polymerization initiator include azobisisobutyronitrile, azobiscyclohexanecarbonitrile, and azobisdimethylvaleronitrile.

[0119] Examples of the peroxide radical polymerization initiator include diacyl radical polymerization initiators, peroxyester radical polymerization initiators, dialkyl radical polymerization initiators, percarbonate radical polymerization initiators, and ketone peroxide radical polymerization initiators. Examples of the diacyl radical polymerization initiator include lauroyl peroxide and benzoyl peroxide. Examples of the peroxyester radical polymerization initiator include t-butyl peroxybenzoate, t-butyl peroxyacetate, t-butyl peroxypivalate, and t-butyl peroxy-2-ethylhexanoate. Examples of the dialkyl radical polymerization initiator include dicumyl peroxide and di-t-butyl peroxide. Examples of the percarbonate radical polymerization initiator include diisopropyl peroxydicarbonate. Examples of the ketone peroxide radical polymerization initiator include methyl ethyl ketone peroxide.

[0120] The redox radical polymerization initiator contains, for example, a peroxide and a reducing agent or a metal-containing compound. Specific examples of the redox radical polymerization initiator include a mixture of benzoyl peroxide and an organic amine, a mixture of the peroxyester radical polymerization initiator and a reducing agent such as a mercaptan, and a mixture of methyl ethyl ketone peroxide and an organic cobalt salt.

[0121] From the viewpoint of enhancing reactivity and storage stability, the polymerization initiator preferably contains a peroxide-based radical polymerization initiator.

[0122] From the viewpoint of improving reactivity and storage stability, the content of the curing agent (polymerization initiator) in 100% by weight of the conductive paste is preferably 0.1% by weight or more, more preferably 0.3% by weight or more, even more preferably 0.5% by weight or more, and is preferably 5% by weight or less, more preferably 4% by weight or less, even more preferably 3% by weight or less.

[0123] The content of the curing agent (polymerization initiator) relative to 100 parts by weight of the curable compound in the conductive paste is preferably 0.3 parts by weight or more, more preferably 0.5 parts by weight or more, even more preferably 0.7 parts by weight or more, and 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 curing agent (polymerization initiator) is equal to or more than the above lower limit and equal to or less than the above upper limit, reactivity and storage stability can be improved.

[0124] <Other ingredients> The conductive paste may contain components other than the curable compound, the curing agent, and the plurality of conductive fillers, such as a solvent, an inorganic filler, an organic filler, a colorant, a polymerization inhibitor, a chain transfer agent, an antioxidant, an ultraviolet absorber, an antifoaming agent, a leveling agent, a surfactant, a slip agent, an antiblocking agent, a wax, a masking agent, a deodorizer, a fragrance, a preservative, an antibacterial agent, an antistatic agent, and an adhesion promoter.

[0125] (RFID inlay and manufacturing method of RFID inlay) The RFID inlay of the present invention comprises a substrate having wiring on its surface, a chip having electrodes on its surface, and an adhesive portion bonding the substrate and the chip. In the RFID inlay of the present invention, the material of the adhesive portion is the conductive paste described above. In the RFID inlay of the present invention, the wiring and the electrodes are electrically connected by the conductive filler in the adhesive portion.

[0126] FIG. 1 is a cross-sectional view schematically showing an RFID inlay using a conductive paste according to a first embodiment of the present invention.

[0127] 1 includes a substrate 82 having wiring on its surface, a chip 83 having electrodes on its surface, and an adhesive portion 84 that bonds the substrate 82 and the chip 83. The material of the adhesive portion 84 is a conductive paste containing a conductive filler 1. The adhesive portion 84 is formed from the conductive paste containing the conductive filler 1. The adhesive portion 84 is preferably formed by hardening the conductive paste containing the conductive filler 1.

[0128] Substrate 82 has wiring 82a on its surface (upper surface). Chip 83 has electrodes 83a on its surface (lower surface). Wiring 82a and electrodes 83a are electrically connected by conductive filler 1 in adhesive portion 84.

[0129] The method for manufacturing an RFID inlay according to the present invention comprises the following steps (1) to (3): (1) a first placement step of placing the above-mentioned conductive paste on a surface of a substrate having wiring on its surface; (2) a second placement step of placing a chip having electrodes on its surface on the surface of the conductive paste opposite the substrate; and (3) a bonding step of forming an adhesive joint that bonds the substrate and the chip with the conductive paste by heating and pressurizing the conductive paste, and electrically connecting the wiring and the electrodes with the conductive filler in the adhesive joint.

[0130] The RFID inlay and the manufacturing method of the RFID inlay according to the present invention use a specific conductive paste, which can improve the adhesion between the substrate and the chip and also improve the reliability of the electrical connection.

[0131] In the method for manufacturing an RFID inlay, it is preferable that the substrate is long, and that the RFID inlay is manufactured by conveying the long substrate by a roll-to-roll method in the first arrangement step, the second arrangement step, and the bonding step. In this case, multiple RFID inlays can be manufactured continuously, further improving the manufacturing efficiency of RFID inlays.

[0132] When the roll-to-roll method is used, the transport speed of the substrate is not particularly limited.

[0133] Examples of methods for disposing the conductive paste include application using a dispenser, screen printing, and ejection using an inkjet device.

[0134] The heating temperature in the bonding 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. When the heating temperature in the bonding step is equal to or higher than the lower limit and equal to or lower than the upper limit, good electrical connection can be achieved between the chip and the wiring (antenna pattern).

[0135] The pressure applied in the bonding step is preferably 0.5 N or more, more preferably 1 N or more, and is preferably 3.5 N or less, more preferably 3 N or less, and even more preferably 2.5 N or less. When the pressure applied in the bonding step is equal to or greater than the lower limit and equal to or less than the upper limit, the adhesion between the substrate and the chip can be improved, and the electrical connection reliability can be improved.

[0136] The heating and pressurizing time in the bonding step is not particularly limited, and may be 2 seconds or more, 15 seconds or less, or 10 seconds or less.

[0137] The RFID inlay may be cut to a predetermined size as needed, or may be used after being cut. Preferably, a plurality of the chips are adhered to a long substrate by a plurality of the adhesive parts. A plurality of stacks of the chips and the adhesive parts may be arranged on the long substrate. In the first arranging step, it is preferable to arrange the conductive paste at a plurality of locations on the surface of the long substrate. In the second arranging step, it is preferable to use a plurality of chips and arrange the chips on the surface opposite the substrate side of each of the conductive pastes arranged at a plurality of locations. After the chips are adhered to the long substrate by the adhesive parts, the long substrate may be cut.

[0138] The substrate is not particularly limited. The substrate is preferably a circuit board. Examples of the circuit board include a resin film, a flexible printed circuit board, a rigid-flexible board, a glass board, and a paper board. The base material may be a resin board, a glass board, or a paper board.

[0139] The substrate has wiring (antenna pattern) on its surface. The substrate has wiring (antenna pattern) formed on its surface. The substrate preferably has a substrate and wiring (antenna pattern) disposed on the surface of the substrate.

[0140] Examples of the material for the substrate include resin, glass, and paper. Examples of the resin include PET (polyethylene terephthalate), PP (polypropylene), and PVC (polyvinyl chloride). The paper may be impregnated with an epoxy resin or a phenolic resin. From the viewpoint of further enhancing adhesiveness and manufacturing RFID inlays using a roll-to-roll method, the material for the substrate is preferably resin or paper, and more preferably PET (polyethylene terephthalate) or paper. The substrate may be resin, glass, or paper.

[0141] 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. From the viewpoint of improving the operating sensitivity in the UHF band (860 MHz to 920 MHz), the wiring is preferably aluminum wiring.

[0142] From the viewpoint of preventing deformation of the substrate due to heat when mounting a chip (e.g., an IC chip) and increasing flexibility, the thickness of the substrate is preferably 20 μm or more, more preferably 30 μm or more, and is preferably 200 μm or less, more preferably 100 μm or less.

[0143] The shapes of the substrate and the base material are not particularly limited. From the viewpoint of manufacturing RFID inlays by a roll-to-roll method, the substrate and the base material are preferably long. The lengths of the substrate and the base material are not particularly limited. The lengths of the substrate and the base material may be 1 m or more, 10 m or more, 5000 m or less, or 1000 m or less.

[0144] The surface tension of the substrate (base material) is preferably 30 mN / m or more, more preferably 32 mN / m or more, even more preferably 34 mN / m or more, and preferably 50 mN / m or less, more preferably 48 mN / m or less, even more preferably 45 mN / m or less. When the surface tension of the substrate (base material) is above the above lower limit and below the above upper limit, adhesion can be further improved. The conductive paste according to the present invention can be suitably used for application to a substrate (base material) having a surface tension above the above lower limit and below the above upper limit.

[0145] The surface tension of the substrate (base material) can be measured in accordance with JIS K6768 using the following method: A cotton swab is dipped in a JIS-specified liquid and applied to the substrate (base material). The surface tension is determined from the shape of the coating film 2 seconds after application.

[0146] The chip may be a semiconductor chip (IC chip) or the like.

[0147] The chip has an electrode on its surface. Examples of the electrode include metal electrodes such as gold electrodes, nickel electrodes, tin electrodes, aluminum electrodes, silver electrodes, SUS electrodes, copper electrodes, molybdenum electrodes, and tungsten electrodes. From the viewpoint of further improving the electrical conductivity reliability, the electrode is preferably a copper electrode or a gold electrode, and more preferably a copper electrode.

[0148] The number of electrodes per chip is not particularly limited, and may be 1 or more, 4 or more, 20 or less, or 10 or less.

[0149] The shape of the tip is not particularly limited, and may be rectangular, triangular, or circular.

[0150] The planar area of ​​the chip is preferably 0.04 mm 2 More than 0.09mm, preferably 0.09mm 2 More preferably, 0.16 mm 2or more, preferably 0.50 mm 2 Less than or equal to 0.40 mm, preferably 2 Less than 0.30 mm, more preferably 2 When the planar area of ​​the chip is equal to or greater than the lower limit, the conductive paste can be placed on fine wiring with high precision. When the planar area of ​​the chip is equal to or less than the upper limit, the RFID inlay can maintain its electrical conductivity reliability even when left in a high-temperature, high-humidity environment for a long period of time. The conductive paste of the present invention can be suitably used for bonding relatively small chips.

[0151] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0152] The following materials were prepared:

[0153] Curable compound: Isobornyl acrylate ((A) polymerizable monomer, molecular weight: 208) Polyester urethane acrylate (Negami Chemical Industrial Co., Ltd. "UN-353", molecular weight (weight average molecular weight): 5000) Tricyclodecane dimethanol diacrylate (Daicel Allnex "IRR214", molecular weight: 304) Trimethylolpropane triacrylate ("A-TMPT" manufactured by Shin-Nakamura Chemical Co., Ltd., molecular weight: 296) Epoxy resin half acrylate (Daicel Allnex "EBECRYL3605", molecular weight: 450) N-Acryloyloxyethylhexahydrophthalimide ("M-140" manufactured by Toagosei Co., Ltd., molecular weight: 251)

[0154] Hardener: NOF Corporation's "Perbutyl PV" (peroxyester radical polymerization initiator) NOF Corporation's "Niper BW" (diacyl peroxide radical polymerization initiator) Arkema Yoshitomi's "Luperox 10M70" (alkyl peroxyester radical polymerization initiator) NOF Corporation's "Perhexa V" (peroxyketal radical polymerization initiator) NOF Corporation's "Perbutyl D" (dialkyl peroxide radical polymerization initiator)

[0155] Conductive filler: "NIELB-005-S" manufactured by Sekisui Chemical Co., Ltd. (Conductive particles consisting of a base particle and a conductive portion on the surface of the base particle, nickel content in 100% by weight of the conductive portion: 52% by weight, average particle diameter: 5 μm)

[0156] Inorganic fillers: Silica (Nippon Shokubai "KE-S100")

[0157] Tips: IC chip (copper electrode, NXP "UCODE7", surface area: 0.22 mm 2 )

[0158] substrate: PET film (long, resin film with aluminum wiring, operating frequency in the UHF band (860MHz to 920MHz), surface tension: 43mN / m)

[0159] 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 mixer (Thinky Corporation's "Awatori Rentaro") to obtain a conductive paste (anisotropic conductive paste).

[0160] (2) RFID inlay fabrication The obtained conductive paste was applied to a PET film by jet dispensing to form a conductive paste layer (adhesive layer) (first placement step). Next, an IC chip was laminated on the surface opposite the substrate side of the conductive paste layer (adhesive layer) so that the wiring on the PET film surface and the electrodes on the chip surface faced each other (second placement step). Thereafter, thermocompression bonding was performed under conditions of an upper heat tool temperature of 175°C, a lower heat tool temperature of 170°C, a pressure of 2N, and a compression time of 5 seconds to harden the conductive paste layer (adhesive layer) and form an adhesive joint. In addition, the wiring on the surface of the PET film and the electrodes on the surface of the chip were electrically connected by conductive filler (conductive particles) in the adhesive joint to obtain a connection structure (adhesion step). The first placement step, the second placement step, and the adhesion step were performed using a "DDA40000" (roll-to-roll method) manufactured by Muhlbauer. The resulting connection structure was cut into pieces measuring 5 cm x 1.5 cm using a "DCL30000" manufactured by Muhlbauer, to obtain 50 RFID inlays.

[0161] (Examples 2 to 9 and Comparative Examples 1 to 3) Conductive pastes and RFID inlays were obtained in the same manner as in Example 1, except that the ingredients and amounts of the conductive paste were changed as shown in Tables 1, 3, and 5.

[0162] (evaluation) (1) Differential scanning calorimetry A differential scanning calorimeter (Hitachi High-Tech Science Corporation, "TA7000") was prepared, and 5 mg of the above conductive paste was placed in a dedicated aluminum pan and covered with a dedicated jig. This dedicated aluminum pan and an empty aluminum pan (reference) were placed in a heating unit and heated in a nitrogen atmosphere from 25°C to 150°C at a temperature increase rate of 10°C / min, and reverse heat flow and non-reverse heat flow were observed. The exothermic peak observed in the non-reverse heat flow was considered to be the exothermic peak of the conductive paste, and the exothermic start temperature, exothermic peak top temperature, and exothermic end temperature were determined.

[0163] (2) Curing shrinkage rate The obtained conductive paste was heated at 130° C. for 10 minutes to be cured, and the specific gravity of the cured conductive paste was measured, and the cure shrinkage was calculated by the method described above.

[0164] (3) Dispensing stability with a jet dispenser The obtained conductive paste was subjected to a discharge test using an inkjet dispenser (Vermes MDS-3200). The discharge stability of the conductive paste using the jet dispenser was evaluated according to the following criteria. "Stable discharge" means that no liquid pooling occurs when the conductive paste is discharged, and there is no change in the amount of droplets discharged.

[0165] [Jet dispenser discharge stability criteria] ○: Stable discharge is possible for 10 minutes. ×: Stable discharge is not possible for 10 minutes.

[0166] (4) Conduction reliability Fifty of the resulting RFID inlays were placed in a dark box that blocks external radio waves, and a frequency reader (Voyantic's "Tagformance Pro") was used to measure the peak sensitivity at 25°C in the UHF band (860 MHz to 920 MHz), which was used as the initial peak sensitivity. The 50 resulting RFID inlays were then heated to 85°C for 15 minutes and cooled to -40°C at a rate of 10°C / min, a cycle consisting of 100 cycles. The peak sensitivity at 25°C in the UHF band of the RFID inlays after the thermal cycling test was similarly measured, and the absolute value of the difference from the initial peak sensitivity was calculated. The initial and post-thermal cycling reliability was evaluated according to the following criteria.

[0167] [Initial conduction reliability criteria] XX: The initial peak sensitivity of all RFID inlays is less than -18dBm ○: Does not fall under either ○○ or × ×: The initial peak sensitivity of at least one RFID inlay is -17 dBm or higher

[0168] [Criteria for determining electrical continuity reliability after thermal cycle testing] XX: The absolute value of the difference in peak sensitivity of all RFID inlays is less than 2 dBm ○: Does not fall under either ○○ or × ×: The absolute value of the difference in the initial peak sensitivity of at least one RFID inlay is 3 dBm or more.

[0169] The compositions of the conductive pastes and the results are shown in Tables 1 to 6 below.

[0170] [Table 1]

[0171] [Table 2]

[0172] [Table 3]

[0173] [Table 4]

[0174] [Table 5]

[0175] [Table 6] [Explanation of symbols]

[0176] 1...Conductive filler 81...RFID inlay 82...Substrate having wiring on its surface 82a...Wiring 83...Chip with electrode on its surface 83a…electrode 84…Continued

Claims

1. A conductive paste including a curable compound, a curing agent, and a plurality of conductive fillers, A conductive paste, wherein when the conductive paste is heated from 25°C to 150°C at a temperature increase rate of 10°C / min and subjected to differential scanning calorimetry, the heat generation start temperature is 82°C or higher and 100°C or lower, the heat generation peak top temperature is 85°C or higher and 103°C or lower, and the heat generation end temperature is 90°C or higher and 108°C or lower.

2. 2. The conductive paste according to claim 1, wherein the absolute value of the difference between the heat generation start temperature and the heat generation end temperature in the differential scanning calorimetry is 5°C or more and 13°C or less.

3. 3. The conductive paste according to claim 1, wherein the conductive paste has a cure shrinkage of 3% or more and 10.8% or less when cured by heating at 130°C for 10 minutes.

4. The conductive paste according to claim 1 or 2, wherein the curable compound comprises a (meth)acrylic compound.

5. the curable compound contains a polymerizable monomer having one (meth)acryloyl group, 3. The conductive paste according to claim 1, wherein the content of the polymerizable monomer is 50% by weight or less in 100% by weight of the curable compound.

6. The conductive paste according to claim 1 or 2, used to obtain an RFID inlay.

7. The device comprises a substrate having wiring on its surface, a chip having electrodes on its surface, and an adhesive portion that bonds the substrate and the chip together, The material of the adhesive portion is the conductive paste according to claim 1 or 2, An RFID inlay, wherein the wiring and the electrode are electrically connected by the conductive filler in the adhesive portion.

8. a first disposing step of disposing the conductive paste according to claim 1 or 2 on a surface of a substrate having wiring on the surface; a second placement step of placing a chip having an electrode on a surface of the conductive paste opposite to the substrate; A method for manufacturing an RFID inlay, comprising: a bonding process in which an adhesive joint that bonds the substrate and the chip is formed using the conductive paste by heating and pressurizing the conductive paste, and the wiring and the electrode are electrically connected by the conductive filler in the adhesive joint.

9. The substrate is long, The method for manufacturing an RFID inlay according to claim 8 , wherein the RFID inlay is manufactured by transporting the long substrate using a roll-to-roll method in the first placement step, the second placement step, and the bonding step.

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