Electrically conductive paste, RFID inlay, and method for producing RFID inlay

Abstract

Provided is an electrically conductive paste capable of suppressing the generation of voids in a cured product of the electrically conductive paste in a case where mounting is carried out in a relatively short time in an air atmosphere.　This electrically conductive paste contains a curable compound, a curing agent and an electrically conductive filler. The curable compound includes a partial epoxy (meth)acrylate compound. The content of the partial epoxy (meth)acrylate compound is 10.0-45.0 wt% in 100 wt% of the electrically conductive paste. The electrically conductive paste does not contain a (meth)acrylate compound having a molecular weight of 150 or less or contains 15.0 wt% or less of a (meth)acrylate compound having a molecular weight of 150 or less.

Description

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

[0001] 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, and the use of the conductive paste for bonding chips and for obtaining an RFID inlay.

[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, RFID inlays in the UHF (Ultra High Frequency) band (860 MHz to 960 MHz) have attracted attention due to their long communication distances. UHF 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 may be used to bond and connect a chip having electrodes on its surface to a substrate having wiring (antenna pattern) on its surface.

[0004] In recent years, as electronic components using RFID inlays have become smaller, the chips used in RFID inlays have also become smaller, creating a demand for conductive pastes that have high adhesive properties and can be placed on wiring with greater precision.

[0005] 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.

[0006] 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.

[0007] JP 2006-144018 A JP 2013-124330 A

[0008] Conventional adhesives (conductive pastes) such as those described in Patent Documents 1 and 2 can enhance adhesiveness to a certain extent. However, when conventional conductive pastes are used to fabricate (mount) electronic components in an air atmosphere, voids can occur in the cured conductive paste. If voids exist in the cured conductive paste, they tend to remain in the bonded joint, reducing the reliability of electrical continuity between the upper and lower electrodes to be connected and the reliability of connection between the bonded joint and the electrode. This problem is particularly pronounced when mounting is performed within a relatively short time (e.g., within 15 seconds).

[0009] An object of the present invention is to provide a conductive paste that can suppress the generation of voids in the cured product when mounted in a relatively short time under an atmospheric environment, etc. Another object of the present invention is to provide an RFID inlay using the conductive paste and a method for manufacturing an RFID inlay. Another object of the present invention is to provide a use of the conductive paste for bonding a chip and a use of the conductive paste for obtaining an RFID inlay.

[0010] Disclosed herein are the following conductive pastes, RFID inlays, methods for manufacturing RFID inlays, the use of conductive pastes to bond chips, and the use of conductive pastes to obtain RFID inlays.

[0011] Item 1. A conductive paste comprising a curable compound, a curing agent, and a conductive filler, wherein the curable compound comprises a partial epoxy (meth)acrylate compound, and the content of the partial epoxy (meth)acrylate compound in 100% by weight of the conductive paste is 10.0% by weight or more and 45.0% by weight or less, and the conductive paste does not contain a (meth)acrylic compound having a molecular weight of 150 or less, or contains 15.0% by weight or less of a (meth)acrylic compound having a molecular weight of 150 or less.

[0012] Item 2. The conductive paste according to Item 1, wherein the conductive paste does not contain a first (meth)acrylate compound having one (meth)acryloyl group and no epoxy group, or contains the first (meth)acrylate compound in an amount of 30.0 wt % or less.

[0013] Item 3. The conductive paste according to Item 1 or 2, wherein the conductive paste contains a second (meth)acrylate compound having two or more (meth)acryloyl groups and one or more reactive functional groups other than (meth)acryloyl groups, and the content of the second (meth)acrylate compound in 100% by weight of the conductive paste is 20.0% by weight or more and 70.0% by weight or less.

[0014] Item 4. The conductive paste according to any one of Items 1 to 3, wherein the conductive paste contains or does not contain a non-conductive filler, and the total content of the conductive filler and the non-conductive filler in 100% by volume of the conductive paste is 15.0% by volume or less.

[0015] Item 5. The conductive paste according to any one of Items 1 to 4, which is used to obtain an RFID inlay.

[0016] Item 6. 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 together, wherein the adhesive portion is made of the conductive paste according to any one of Items 1 to 5, and the wiring and the electrodes are electrically connected by the conductive filler in the adhesive portion.

[0017] Item 7. 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 5 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 an adhesion step of forming an adhesive joint using the conductive paste to bond the substrate and the chip by heating and pressurizing the conductive paste, and electrically connecting the wiring and the electrodes via the conductive filler in the adhesive joint.

[0018] Item 8. The method for manufacturing an RFID inlay according to Item 7, wherein the substrate is long, and the RFID inlay is manufactured by transporting the long substrate by a roll-to-roll method in the first arrangement step, the second arrangement step, and the bonding step.

[0019] Item 9. The conductive paste according to any one of items 1 to 5, having a plane area of ​​0.50 mm ２ Used for gluing chips that are:

[0020] Item 10. Use of the conductive paste according to any one of Items 1 to 5 to obtain an RFID inlay.

[0021] The conductive paste according to the present invention includes a curable compound, a curing agent, and a conductive filler. In the conductive paste according to the present invention, the curable compound includes a partial epoxy (meth)acrylate compound, and the content of the partial epoxy (meth)acrylate compound in 100% by weight of the conductive paste is 10.0% by weight or more and 45.0% by weight or less. The conductive paste according to the present invention does not include a (meth)acrylic compound having a molecular weight of 150 or less, or includes 15.0% by weight or less of a (meth)acrylic compound having a molecular weight of 150 or less. Because the conductive paste according to the present invention has the above configuration, it is possible to suppress the occurrence of voids in the cured product of the conductive paste when mounted in an air atmosphere or the like in a relatively short time.

[0022] 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.

[0023] The present invention will be described in detail below.

[0024] (Conductive Paste) The conductive paste according to the present invention contains a curable compound, a curing agent, and a conductive filler.

[0025] In the conductive paste according to the present invention, the curable compound contains a partial epoxy (meth)acrylate compound, and the content of the partial epoxy (meth)acrylate compound in 100% by weight of the conductive paste is 10.0% by weight or more and 45.0% by weight or less.

[0026] The conductive paste according to the present invention does not contain a (meth)acrylic compound having a molecular weight of 150 or less, or contains 15.0 wt% or less of a (meth)acrylic compound having a molecular weight of 150 or less. That is, the conductive paste according to the present invention optionally contains a (meth)acrylic compound having a molecular weight of 150 or less, and when the conductive paste contains the (meth)acrylic compound having a molecular weight of 150 or less, the content of the (meth)acrylic compound having a molecular weight of 150 or less is 15.0 wt% or less.

[0027] When conventional conductive pastes are used to fabricate (mount) electronic components in an air atmosphere, voids can occur in the cured product of the conductive paste. If voids exist in the cured product of the conductive paste, they tend to remain in the bonded joints that are formed, resulting in problems such as reduced electrical connection reliability between the upper and lower electrodes to be connected and reduced connection reliability between the bonded joints and the electrodes. This problem is particularly pronounced when mounting is performed in a relatively short time (e.g., within 15 seconds).

[0028] As a result of extensive research, the present inventors have found that there is a correlation between the occurrence of voids in a cured conductive paste and the volumetric shrinkage rate of the conductive paste when cured. Specifically, the present inventors have found that by reducing the volumetric shrinkage rate of the conductive paste when cured, it is possible to suppress the occurrence of voids in the cured conductive paste when mounting is performed in a relatively short time in an air atmosphere, for example.

[0029] That is, since the conductive paste according to the present invention has the above-described configuration, it is possible to reduce the volumetric shrinkage rate of the conductive paste when hardened, and to suppress the generation of voids in the cured product of the conductive paste when mounted in a relatively short time, such as in an air atmosphere. In particular, the conductive paste according to the present invention is able to suppress the generation of voids in the cured product of the conductive paste when mounted in a relatively short time, such as in an air atmosphere. As a result, it is possible to suppress the generation of voids remaining in the adhesive joint of the obtained electronic component, thereby improving the reliability of conduction between the upper and lower electrodes to be connected and the reliability of connection between the adhesive joint and the electrodes.

[0030] Furthermore, the conductive paste according to the present invention can suppress the occurrence of voids in the cured product of the conductive paste even when mounted in an atmosphere other than the air atmosphere. Furthermore, the conductive paste according to the present invention can suppress the occurrence of voids in the cured product of the conductive paste even when mounted for a medium to long time. The conductive paste according to the present invention can suppress the occurrence of voids in the cured product of the conductive paste when mounted under various conditions.

[0031] The volumetric shrinkage of the cured product obtained by heating the conductive paste at 150°C for 30 minutes is preferably 10.0% or less, more preferably 8.0% or less, even more preferably 7.5% or less, particularly preferably 7.4% or less, and most preferably 7.0% or less. When the volumetric shrinkage of the cured product is equal to or less than the upper limit, the generation of voids in the cured product of the conductive paste can be further suppressed. The lower limit of the volumetric shrinkage of the cured product is not particularly limited. The volumetric shrinkage of the cured product may be 0% or more or may be 1.0% or more. The range of the volumetric shrinkage of the cured product can be set by appropriately selecting the lower limit and the upper limit. The volumetric shrinkage of the cured product is the volumetric shrinkage of the conductive paste when cured when heated at 150°C for 30 minutes.

[0032] The volumetric shrinkage of the cured product is measured, for example, as follows. First, the specific gravity of the conductive paste (before curing) at 23°C is measured using a density meter before curing. Next, the conductive paste is filled into a disk-shaped mold having a diameter of 1 mm and a height of 1 mm, and the top and bottom surfaces of the filled product are sandwiched between glass plates that have been treated with a mold release agent. This is heated at 150°C for 30 minutes to obtain a cured product (cured product for evaluation). Eight of the cured products are stacked to prepare a measurement sample. The specific gravity of the obtained measurement sample at 23°C is measured using a density meter, and the obtained measured value is defined as the specific gravity of the cured product. The volumetric shrinkage of the cured product is calculated using the following formula. Examples of the density meter include a dry density meter (e.g., Shimadzu Corporation's "Accupyk II 1345"), etc.

[0033] Volume shrinkage rate (%) of the cured product = (G1 - G2) x 100 / G2 G1: specific gravity of the conductive paste (before curing) at 23°C G2: specific gravity of the cured product at 23°C

[0034] Methods for easily adjusting the volumetric shrinkage rate of the cured product within a preferred range include the following methods: A method using a preferred partial epoxy (meth)acrylate compound described below; A method adjusting the content of the partial epoxy (meth)acrylate compound; A method adjusting the content of a (meth)acrylic compound having a molecular weight of 150 or less; A method using a preferred first (meth)acrylate compound described below; A method adjusting the content of the first (meth)acrylate compound; A method using a preferred second (meth)acrylate compound described below; A method adjusting the content of the second (meth)acrylate compound; A method adjusting the blending amount of a conductive filler; A method adjusting the blending amount of a non-conductive filler.

[0035] The conductive paste according to the present invention is in a paste form at 23°C. The conductive paste is used by being discharged, for example, at 20°C to 50°C. The conductive paste according to the present invention is preferably used by being discharged using a dispenser, and more preferably by being discharged using a jet dispenser or a metered dose dispenser. The metered dose dispenser is preferably a micrometered dose dispenser.

[0036] The viscosity (η23) of the conductive paste at 23°C is preferably 8.0 Pa·s or more, more preferably 9.0 Pa·s or more, even more preferably 9.5 Pa·s or more, particularly preferably 10.0 Pa·s or more, and preferably 120 Pa·s or less, more preferably 100 Pa·s or less, even more preferably 40.0 Pa·s or less, particularly preferably 30.0 Pa·s or less, and most preferably 20.0 Pa·s or less. When the viscosity (η23) is above the lower limit, outflow of the conductive paste from around the chip and from the wiring can be suppressed. When the viscosity (η23) is below the upper limit, the conductive paste can be placed on fine wiring with high precision, adhesion can be further improved, and the occurrence of voids in the cured conductive paste can be further suppressed.

[0037] The viscosity (η23) can be measured, for example, using an E-type viscometer at 23° C. and 5 rpm. Examples of the E-type viscometer include the TV22 viscometer manufactured by Toki Sangyo Co., Ltd.

[0038] 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.

[0039] From the viewpoint of further improving the reliability of conduction, 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 an electrode 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 an electrode on its surface to a substrate having wiring (antenna pattern) on its surface).

[0040] The conductive paste is preferably thermosetting, and is preferably a thermosetting conductive paste, more preferably a thermosetting anisotropic conductive paste.

[0041] Each component contained in the conductive paste will be described below.

[0042] 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.

[0043] <Curable Compound> Examples of the curable compound include thermosetting compounds and photocurable compounds. 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, oxetanyl 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.

[0044] The content of the curable compound in 100% by weight of the conductive paste is preferably 30.0% by weight or more, more preferably 40.0% by weight or more, even more preferably 45.0% by weight or more, even more preferably 50.0% by weight or more, even more preferably 55.0% by weight or more, particularly preferably 57.5% by weight or more, and most preferably 60.0% by weight or more, and is preferably 95.0% by weight or less, more preferably 92.5% by weight or less, even more preferably 90.0% by weight or less, particularly preferably 87.5% by weight or less, and most preferably 85.0% by weight or less. When the content of the curable compound is above the lower limit, the conductive paste can be cured more satisfactorily when mounted in a relatively short time, such as in an atmospheric atmosphere. When the content of the curable compound is below the upper limit, the occurrence of voids can be further suppressed. The content of the curable compound is the total content of the curable compound contained in the conductive paste.

[0045] Partial epoxy (meth)acrylate compound: In the conductive paste, the curable compound includes a partial epoxy (meth)acrylate compound. The partial epoxy (meth)acrylate compound is, for example, a curable compound in which some epoxy groups in an epoxy compound have been acrylic esterified. The partial epoxy (meth)acrylate compound is available as a commercially available curable compound in which some epoxy groups in an epoxy compound have been acrylic esterified. Only one type of the partial epoxy (meth)acrylate compound may be used, or two or more types may be used.

[0046] The partial epoxy (meth)acrylate compound includes a partial epoxy (meth)acrylate compound having one (meth)acryloyl group and one or more epoxy groups. The conductive paste includes a partial epoxy (meth)acrylate compound having one (meth)acryloyl group and one or more epoxy groups.

[0047] Examples of the partial epoxy (meth)acrylate compound include a compound obtained by reacting some of the epoxy groups of a compound having two or more epoxy groups (epoxy compound) with (meth)acrylic acid, and a compound obtained by reacting a compound having two or more isocyanate groups with a (meth)acrylic acid derivative having a hydroxyl group, and then reacting the compound with glycidol.

[0048] From the viewpoint of more effectively exerting the effects of the present invention, the partial epoxy (meth)acrylate compound is preferably a compound obtained by reacting some of the epoxy groups of a compound having two or more epoxy groups with (meth)acrylic acid.

[0049] The partial epoxy (meth)acrylate compound may have one epoxy group, two epoxy groups, two or more epoxy groups, three or more epoxy groups, ten or less epoxy groups, or five or less epoxy groups.

[0050] The partial epoxy (meth)acrylate compound may or may not have a reactive functional group other than a (meth)acryloyl group and an epoxy group. Examples of the reactive functional group other than a (meth)acryloyl group and an epoxy group in the partial epoxy (meth)acrylate compound include an oxetanyl group, an amino group, a hydroxy group, a carboxy group, an amide group, an isocyanate group, and an episulfide group. The reactive functional group other than a (meth)acryloyl group and an epoxy group in the partial epoxy (meth)acrylate compound may be of only one type, or may be of two or more types. The partial epoxy (meth)acrylate compound may have one, two or more, three or more, ten or fewer, or five or fewer reactive functional groups other than a (meth)acryloyl group and an epoxy group.

[0051] The reactive functional groups other than the (meth)acryloyl group and the epoxy group in the partial epoxy (meth)acrylate compound are preferably oxetanyl, amino, hydroxy, or carboxy groups, more preferably hydroxy or carboxy groups, and even more preferably hydroxy groups. That is, the partial epoxy (meth)acrylate compound more preferably contains a curable compound having one (meth)acryloyl group, one or more epoxy groups, and one or more hydroxy or carboxy groups. It is even more preferable that the partial epoxy (meth)acrylate compound contains a curable compound having one (meth)acryloyl group, one or more epoxy groups, and one or more hydroxy groups. In these cases, the conductive paste can be cured more satisfactorily when mounted in an atmospheric atmosphere or the like for a relatively short time.

[0052] Commercially available partial epoxy (meth)acrylate compounds include "EBECRYL3605" manufactured by Daicel Allnex Co., Ltd., "PNEA-50" manufactured by KSM Co., Ltd., "PNEM-50" manufactured by KSM Co., Ltd., "BAEA-50" manufactured by KSM Co., Ltd., and "BAEM-50" manufactured by KSM Co., Ltd.

[0053] The molecular weight of the partial epoxy (meth)acrylate compound is preferably 142 or more, more preferably 150 or more, even more preferably more than 150, particularly preferably 160 or more, and is preferably 2000 or less, more preferably 1500 or less, and even more preferably 1000 or less. When the molecular weight of the partial epoxy (meth)acrylate compound is equal to or more than the above lower limit (or exceeds the above lower limit) and equal to or less than the above upper limit, the generation of voids in the cured product of the conductive paste can be more effectively suppressed when mounting is performed in a relatively short time in an air atmosphere, etc.

[0054] The molecular weight means a molecular weight that can be calculated from the structural formula when the partial epoxy (meth)acrylate compound is not a polymer and when the structural formula of the partial epoxy (meth)acrylate compound can be identified, or a weight average molecular weight when the partial epoxy (meth)acrylate compound is a polymer.

[0055] The content of the partial epoxy (meth)acrylate compound in 100% by weight of the conductive paste is 10.0% by weight or more and 45.0% by weight or less. The content of the partial epoxy (meth)acrylate compound in 100% by weight of the conductive paste is preferably 11.0% by weight or more, more preferably 13.0% by weight or more, even more preferably 15.0% by weight or more, and preferably 44.0% by weight or less, more preferably 42.0% by weight or less, and even more preferably 40.0% by weight or less. When the content of the partial epoxy (meth)acrylate compound is above the lower limit, the conductive paste can be cured more satisfactorily when mounted in a relatively short time, such as in the air. When the content of the partial epoxy (meth)acrylate compound is below the upper limit, the generation of voids in the cured product of the conductive paste can be more effectively suppressed when mounted in a relatively short time, such as in the air.

[0056] The content of the partial epoxy (meth)acrylate compound in 100 wt% of the curable compound is preferably 10.0 wt% or more, more preferably 12.5 wt% or more, even more preferably 15.0 wt% or more, even more preferably 20.0 wt% or more, particularly preferably 30.0 wt% or more, and most preferably 40.0 wt% or more, and is preferably 90.0 wt% or less, more preferably 85.0 wt% or less, even more preferably 80.0 wt% or less, particularly preferably 70.0 wt% or less, and most preferably 60.0 wt% or less. When the content of the partial epoxy (meth)acrylate compound is above the lower limit, the conductive paste can be cured more satisfactorily when mounted in a relatively short time, such as in an atmospheric atmosphere. When the content of the partial epoxy (meth)acrylate compound is below the upper limit, the generation of voids can be further suppressed.

[0057] First (meth)acrylate compound: The conductive paste may or may not contain a first (meth)acrylate compound having one (meth)acryloyl group and no epoxy group. The conductive paste optionally contains the first (meth)acrylate compound. The curable compound may or may not contain the first (meth)acrylate compound. The curable compound optionally contains the first (meth)acrylate compound. Only one type of the first (meth)acrylate compound may be used, or two or more types may be used in combination.

[0058] The first (meth)acrylate compound is a curable compound having one (meth)acryloyl group and no epoxy group.

[0059] Examples of the first (meth)acrylate compound include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, allyl (meth)acrylate, benzyl (meth)acrylate, cyclohexyl (meth)acrylate, phenyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, methoxyethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, allyl (meth)acrylate, benzyl (meth)acrylate, cyclohexyl (meth)acrylate, phenyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, 2-hydroxypropyl ... Examples of the acrylates include diethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, methoxypropylene glycol (meth)acrylate, methoxydipropylene glycol (meth)acrylate, isobornyl (meth)acrylate, dicyclopentadienyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, glycerol mono(meth)acrylate, 2-ethylhexyl (meth)acrylate, dihydroxycyclopentadienyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, naphthyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, and N-(meth)acryloyloxyethyl hexahydrophthalimide.

[0060] The molecular weight of the first (meth)acrylate compound is preferably 150 or more, more preferably more than 150, even more preferably 175 or more, particularly preferably 200 or more, and is preferably 1000 or less, more preferably 500 or less, and even more preferably 300 or less. When the molecular weight of the first (meth)acrylate compound is equal to or more than the above lower limit (or exceeds the above lower limit) and equal to or less than the above upper limit, the generation of voids in the cured product of the conductive paste can be more effectively suppressed when mounting is performed in a relatively short time in an air atmosphere, etc.

[0061] When the first (meth)acrylate compound is not a polymer and when the structural formula of the first (meth)acrylate compound can be identified, the molecular weight refers to a molecular weight that can be calculated from the structural formula, and when the first (meth)acrylate compound is a polymer, the molecular weight refers to a weight average molecular weight.

[0062] The conductive paste preferably does not contain a first (meth)acrylate compound having one (meth)acryloyl group and no epoxy group, or contains 40.0 wt% or less of the first (meth)acrylate compound. It is particularly preferred that the conductive paste does not contain a first (meth)acrylate compound having one (meth)acryloyl group and no epoxy group, or contains 30.0 wt% or less of the first (meth)acrylate compound. When the conductive paste contains the first (meth)acrylate compound, the content of the first (meth)acrylate compound in 100 wt% of the conductive paste is preferably 40.0 wt% or less, more preferably 35.0 wt% or less, even more preferably 30.0 wt% or less, even more preferably 25.0 wt% or less, particularly preferably 20.0 wt% or less, and most preferably 10.0 wt% or less. When the content of the first (meth)acrylate compound is equal to or less than the upper limit, the occurrence of voids in the cured product of the conductive paste can be more effectively suppressed when the conductive paste is mounted in an air atmosphere or the like for a relatively short time. The lower limit of the content of the first (meth)acrylate compound is not particularly limited. The content of the first (meth)acrylate compound in 100% by weight of the conductive paste may be 0% by weight or more, more than 0% by weight, 1.0% by weight or more, 3.0% by weight or more, 5.0% by weight or more, or 10.0% by weight or more. The range of the content of the first (meth)acrylate compound can be set by appropriately selecting the lower limit and the upper limit.

[0063] When the conductive paste contains the first (meth)acrylate compound, the content of the first (meth)acrylate compound in 100 wt% of the curable compound is preferably 60.0 wt% or less, more preferably 50.0 wt% or less, even more preferably 40.0 wt% or less, even more preferably 30.0 wt% or less, even more preferably 25.0 wt% or less, particularly preferably 20.0 wt% or less, and most preferably 10.0 wt% or less. When the content of the first (meth)acrylate compound is below the upper limit, the occurrence of voids in the cured product of the conductive paste can be more effectively suppressed when mounted in a relatively short time under an atmospheric atmosphere, etc. The lower limit of the content of the first (meth)acrylate compound is not particularly limited. The content of the first (meth)acrylate compound in 100% by weight of the curable compound may be 0% by weight or more, more than 0% by weight, 1.0% by weight or more, 3.0% by weight or more, 5.0% by weight or more, or 10.0% by weight or more. The range of the content of the first (meth)acrylate compound can be set by appropriately selecting the lower limit and the upper limit.

[0064] (Meth)acrylic compound having a molecular weight of 150 or less: The conductive paste may or may not contain a (meth)acrylic compound having a molecular weight of 150 or less. The conductive paste optionally contains a (meth)acrylic compound having a molecular weight of 150 or less. The curable compound may or may not contain the (meth)acrylic compound having a molecular weight of 150 or less. The curable compound optionally contains the (meth)acrylic compound having a molecular weight of 150 or less. Only one type of (meth)acrylic compound having a molecular weight of 150 or less may be used, or two or more types may be used in combination.

[0065] The (meth)acrylic compound having a molecular weight of 150 or less is a curable compound having a (meth)acryloyl group and a molecular weight of 150 or less.

[0066] The (meth)acrylic compound having a molecular weight of 150 or less may be a curable compound (first (meth)acrylate compound) having one (meth)acryloyl group and no epoxy group. That is, the first (meth)acrylate compound may contain a (meth)acrylate compound having one (meth)acryloyl group, no epoxy group, and a molecular weight of 150 or less.

[0067] Examples of the (meth)acrylic compound having a molecular weight of 150 or less include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl acrylate, hydroxyethyl acrylate, and hydroxypropyl acrylate.

[0068] There are no particular limitations on the molecular weight of the (meth)acrylic compound having a molecular weight of 150 or less. The molecular weight of the (meth)acrylic compound having a molecular weight of 150 or less may be less than 150, 140 or less, 130 or less, or 120 or less. The molecular weight of the (meth)acrylic compound having a molecular weight of 150 or less may be 100 or more, or 120 or more. The range of the molecular weight of the (meth)acrylic compound having a molecular weight of 150 or less can be set by appropriately selecting the lower limit and the upper limit.

[0069] The above molecular weight means a molecular weight that can be calculated from the structural formula of the (meth)acrylic compound having a molecular weight of 150 or less.

[0070] The conductive paste does not contain the (meth)acrylic compound having a molecular weight of 150 or less, or contains the (meth)acrylic compound having a molecular weight of 150 or less in an amount of 15.0 wt% or less. The content of the (meth)acrylic compound having a molecular weight of 150 or less in 100 wt% of the conductive paste is preferably 12.0 wt% or less, more preferably 10.0 wt% or less, even more preferably 5.0 wt% or less, particularly preferably 3.0 wt% or less, and most preferably 0 wt% (not contained). When the content of the (meth)acrylic compound having a molecular weight of 150 or less is equal to or less than the upper limit, the effects of the present invention can be more effectively exhibited. In particular, when the content of the (meth)acrylic compound having a molecular weight of 150 or less is equal to or less than the upper limit, the occurrence of voids can be further suppressed. The content of the (meth)acrylic compound having a molecular weight of 150 or less in 100 wt% of the conductive paste may be 0 wt% or more, more than 0 wt%, 0.1 wt% or more, 0.5 wt% or more, 1.0 wt% or more, or 3.0 wt% or more. The range of the content of the (meth)acrylic compound having a molecular weight of 150 or less can be set by appropriately selecting the lower limit and the upper limit.

[0071] When the conductive paste contains the (meth)acrylic compound having a molecular weight of 150 or less, the content of the (meth)acrylic compound having a molecular weight of 150 or less, relative to 100% by weight of the curable compound, is preferably 30.0% by weight or less, more preferably 25.0% by weight or less, even more preferably 20.0% by weight or less, and particularly preferably 10.0% by weight or less. When the content of the (meth)acrylic compound having a molecular weight of 150 or less is equal to or less than the above upper limit, the effects of the present invention can be more effectively exhibited. In particular, when the content of the (meth)acrylic compound having a molecular weight of 150 or less is equal to or less than the above upper limit, the occurrence of voids can be further suppressed. When the content of the (meth)acrylic compound having a molecular weight of 150 or less is equal to or less than 0% by weight, the content of the (meth)acrylic compound having a molecular weight of 150 or less, relative to 100% by weight of the curable compound, may be 0% by weight or more, more than 0% by weight, 0.1% by weight or more, 0.5% by weight or more, or 1.0% by weight or more. The range of the content of the (meth)acrylic compound having a molecular weight of 150 or less can be set by appropriately selecting the above lower limit and upper limit.

[0072] Second (meth)acrylate compound: The conductive paste may or may not contain a second (meth)acrylate compound having two or more (meth)acryloyl groups and one or more reactive functional groups other than (meth)acryloyl groups. The conductive paste optionally contains the second (meth)acrylate compound. The curable compound may or may not contain the second (meth)acrylate compound. The curable compound optionally contains the second (meth)acrylate compound. Only one type of the second (meth)acrylate compound may be used, or two or more types may be used in combination.

[0073] The second (meth)acrylate compound is a curable compound having two or more (meth)acryloyl groups and one or more reactive functional groups other than the (meth)acryloyl group.

[0074] From the viewpoint of more effectively exhibiting the effects of the present invention, the conductive paste preferably contains a second (meth)acrylate compound having two or more (meth)acryloyl groups and one or more reactive functional groups other than (meth)acryloyl groups. From the viewpoint of more effectively exhibiting the effects of the present invention, the curable compound preferably contains the second (meth)acrylate compound.

[0075] The second (meth)acrylate compound may have one reactive functional group other than a (meth)acryloyl group, or may have two, two or more, three or more, ten or less, or five or less.

[0076] Examples of the reactive functional group other than the (meth)acryloyl group in the second (meth)acrylate compound include an epoxy group, an oxetanyl group, an amino group, a hydroxy group, a carboxy group, an amide group, an isocyanate group, and an episulfide group, etc. The reactive functional group other than the (meth)acryloyl group in the second (meth)acrylate compound may be of only one type or of two or more types.

[0077] From the viewpoint of more effectively achieving the effects of the present invention, the reactive functional group other than the (meth)acryloyl group in the second (meth)acrylate compound preferably has polarity, and is preferably a polar group. From the viewpoint of more effectively achieving the effects of the present invention, the reactive functional group other than the (meth)acryloyl group in the second (meth)acrylate compound is preferably a functional group capable of reacting with an epoxy group. From the viewpoint of more effectively achieving the effects of the present invention, the second (meth)acrylate compound preferably contains a curable compound having two or more (meth)acryloyl groups and one or more functional groups capable of reacting with an epoxy group. The epoxy group may be a part of a glycidyl group.

[0078] The reactive functional group other than the (meth)acryloyl group in the second (meth)acrylate compound is preferably a hydroxy group, an amino group, or a carboxy group, more preferably a hydroxy group or an amino group, and even more preferably an amino group. That is, the second (meth)acrylate compound preferably contains a (meth)acrylate compound having two or more (meth)acryloyl groups and one or more hydroxy groups, amino groups, or carboxy groups. More preferably, the second (meth)acrylate compound contains a (meth)acrylate compound having two or more (meth)acryloyl groups and one or more hydroxy groups or amino groups. In these cases, the conductive paste can be cured more effectively when mounted in an air atmosphere or the like for a relatively short time.

[0079] Commercially available products of the second (meth)acrylate compound include "EBECRYL3701" manufactured by Daicel-Allnex Ltd., "EBECRYL3703" manufactured by Daicel-Allnex Ltd., "EBECRYL8209" manufactured by Daicel-Allnex Ltd., "EBECRYL4587" manufactured by Daicel-Allnex Ltd., "EBECRYL4265" manufactured by Daicel-Allnex Ltd., and "EBECRYL4858" manufactured by Daicel-Allnex Ltd.

[0080] The molecular weight of the second (meth)acrylate compound is preferably 200 or more, more preferably 300 or more, and even more preferably 400 or more, and is preferably 10,000 or less, more preferably 5,000 or less, and even more preferably 2,000 or less. When the molecular weight of the second (meth)acrylate compound is equal to or more than the above lower limit and equal to or less than the above upper limit, the generation of voids in the cured product of the conductive paste can be more effectively suppressed when mounting is performed in a relatively short time in an air atmosphere or the like.

[0081] When the second (meth)acrylate compound is not a polymer and when the structural formula of the second (meth)acrylate compound can be identified, the molecular weight refers to a molecular weight that can be calculated from the structural formula, and when the second (meth)acrylate compound is a polymer, the molecular weight refers to a weight average molecular weight.

[0082] When the conductive paste contains the second (meth)acrylate compound, the content of the second (meth)acrylate compound in 100% by weight of the conductive paste is preferably 1.0 wt% or more, more preferably 5.0 wt% or more, even more preferably 10.0 wt% or more, even more preferably 20.0 wt% or more, particularly preferably 25.0 wt% or more, and most preferably 30.0 wt% or more. When the conductive paste contains the second (meth)acrylate compound, the content of the second (meth)acrylate compound in 100% by weight of the conductive paste is preferably 75.0 wt% or less, more preferably 70.0 wt% or less, and even more preferably 65.0 wt% or less. When the content of the second (meth)acrylate compound is equal to or greater than the lower limit, the conductive paste can be cured more satisfactorily when mounted in an air atmosphere or the like for a relatively short time. When the content of the second (meth)acrylate compound is equal to or less than the upper limit, the occurrence of voids in the cured product of the conductive paste can be more effectively suppressed when mounting is performed in a relatively short time in an air atmosphere, etc. The range of the content of the second (meth)acrylate compound can be set by appropriately selecting the lower limit and the upper limit.

[0083] When the conductive paste contains the second (meth)acrylate compound, the content of the second (meth)acrylate compound in 100 wt% of the curable compound is preferably 1.5 wt% or more, more preferably 7.5 wt% or more, even more preferably 15.0 wt% or more, even more preferably 30.0 wt% or more, particularly preferably 35.0 wt% or more, and most preferably 40.0 wt% or more. When the conductive paste contains the second (meth)acrylate compound, the content of the second (meth)acrylate compound in 100 wt% of the curable compound is preferably 90.0 wt% or less, more preferably 85.0 wt% or less, and even more preferably 80.0 wt% or less. When the content of the second (meth)acrylate compound is above the lower limit, the conductive paste can be cured more satisfactorily when mounted in an atmospheric atmosphere or the like for a relatively short time. When the content of the second (meth)acrylate compound is equal to or less than the upper limit, the occurrence of voids in the cured product of the conductive paste can be more effectively suppressed when mounting is performed in a relatively short time in an air atmosphere, etc. The range of the content of the second (meth)acrylate compound can be set by appropriately selecting the lower limit and the upper limit.

[0084] <Curing Agent> The curing agent is not particularly limited, and any curing agent capable of curing the curable compound can be used as the curing agent.

[0085] From the viewpoint of curing the curable compound, 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.

[0086] 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.

[0087] Examples of the azo radical polymerization initiator include azobisisobutyronitrile, azobiscyclohexanecarbonitrile, and azobisdimethylvaleronitrile.

[0088] 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-butylperoxy-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.

[0089] 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.

[0090] From the viewpoint of enhancing the reactivity and storage stability of the conductive paste, the polymerization initiator preferably contains a peroxide-based radical polymerization initiator.

[0091] From the viewpoint of enhancing the reactivity and storage stability of the conductive paste, 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 5.0% by weight or less, more preferably 4.0% by weight or less, even more preferably 3.0% by weight or less.

[0092] The content of the curing agent (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, and is preferably 6.0 parts by weight or less, more preferably 5.0 parts by weight or less, and even more preferably 4.0 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.

[0093] The content of the curing agent (polymerization initiator) is preferably 0.5 parts by weight or more, more preferably 0.7 parts by weight or more, and even more preferably 1.0 part by weight or more, and is preferably 10.0 parts by weight or less, more preferably 8.0 parts by weight or less, and even more preferably 5.0 parts by weight or less, relative to 100 parts by weight of the content of the partial epoxy (meth)acrylate compound. 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.

[0094] <Conductive Filler> The conductive filler is not particularly limited, and may be conductive particles or carbon fibers.

[0095] The shape of the conductive filler is not particularly limited, and may be spherical, may be a shape other than spherical, or may be flat or the like.

[0096] 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.

[0097] The particle diameter (diameter) of the conductive filler is preferably 0.1 μm or more, more preferably 1 μm or more, even more preferably 2 μm or more, and 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 filler 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 when mounting is performed in a relatively short time in an atmospheric atmosphere, etc. When the conductive filler is a conductive particle, the particle diameter of the conductive filler is the particle diameter of the conductive particle.

[0098] The particle diameter of the conductive filler is preferably an average particle diameter, more preferably a number average particle diameter. The average particle diameter of the conductive filler can be determined, for example, by observing 50 arbitrary conductive fillers with an electron microscope or an optical microscope, calculating the average particle diameter of each conductive filler, or by performing laser diffraction particle size distribution measurement.

[0099] The content of the conductive filler in 100% by weight of the conductive paste is preferably 0.1% by weight or more, more preferably 1.0% by weight or more, and even more preferably 5.0% by weight or more, and is preferably 80.0% by weight or less, more preferably 60.0% by weight or less, and even more preferably 40.0% 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, adhesion and conduction reliability can be further improved when mounting is performed in a relatively short time in an air atmosphere, etc.

[0100] 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. Only one of the metals may be used, or two or more may be used in combination.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] (Base 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.

[0105] 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.

[0106] Various resins are suitable for use 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 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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 (poly)propylene glycol di(meth)acrylate. Examples of suitable monomers 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.

[0111] 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.

[0112] When the base particles are inorganic particles other than metal particles or organic-inorganic hybrid particles, examples of the inorganic material of the base particles include silica, alumina, barium titanate, zirconia, and carbon black. Preferably, the inorganic material is not metal. Examples of the silica particles 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.

[0113] 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.

[0114] Examples of the material for the organic core include the materials for the resin particles described above.

[0115] 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.

[0116] 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.

[0117] 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 above the lower limit, the 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 below 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.

[0118] The particle diameter of the substrate particles is preferably an average particle diameter, and more preferably a number-average particle diameter. The number-average particle diameter of the substrate particles can be measured, for example, as follows. The conductive particles are added to Kulzer's "Technovit 4000" so that the content is 30 wt %, and dispersed to prepare an embedding resin for substrate particle inspection. A cross section of the conductive particles dispersed in the embedding resin for substrate particle inspection is cut out using an ion milling device (Hitachi High-Technologies Corporation's "IM4000") so as to pass through the vicinity of the center of the substrate particle. Then, using a field emission scanning electron microscope (FE-SEM) set at an image magnification of 25,000x, 50 conductive particles are randomly selected, and the substrate particle of each conductive particle is observed. The particle diameter of the substrate particle in each conductive particle is measured, and the arithmetic average is taken to determine the average particle diameter of the substrate particles.

[0119] (Conductive Portion) 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.

[0120] 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.

[0121] 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 100% by weight or less, 99% by weight or less, 90% by weight or less, or 70% by weight or less. The range of the nickel content in 100% by weight of the nickel-containing conductive portion can be set by appropriately selecting the lower limit and the upper limit.

[0122] 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.

[0123] 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.).

[0124] The thickness of the conductive portion is preferably 0.005 μm or more, more preferably 0.01 μm or more, and is 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 above lower limit and equal to or less than the above 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.

[0125] 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.

[0126] 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).

[0127] Core material: The conductive particles preferably have multiple 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 outer 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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 of a plurality of microparticles, and amorphous masses.

[0133] The particle size (diameter) of the core material is preferably 0.001 μm or more, more preferably 0.05 μm or more, and is 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.

[0134] 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, calculating the average particle size of each core substance, or by performing laser diffraction particle size distribution measurement.

[0135] <Non-conductive filler> The conductive paste may or may not contain a non-conductive filler. The conductive paste optionally contains a non-conductive filler.

[0136] Examples of the non-conductive filler include silica, alumina, titanium oxide, calcium oxide, zinc oxide, boron nitride, etc. The non-conductive filler may be used alone or in combination of two or more.

[0137] From the viewpoint of improving the coatability of the conductive paste, the conductive paste preferably contains a non-conductive filler. From the viewpoint of improving the coatability of the conductive paste, the non-conductive filler preferably contains silica or titanium oxide, and more preferably contains silica.

[0138] The content of the non-conductive filler in 100% by weight of the conductive paste is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, and preferably 10.0% by weight or less, more preferably 5.0% by weight or less. When the content of the non-conductive filler is equal to or greater than the lower limit, the coating properties of the conductive paste can be improved, and the electrical conductivity reliability can be increased. When the content of the non-conductive filler is equal to or less than the upper limit, the adhesiveness can be further improved.

[0139] The total content of the conductive filler and the non-conductive filler in 100% by volume of the conductive paste is preferably 5.0% by volume or more, more preferably 10.0% by volume or more, and is preferably 40.0% by volume or less, more preferably 30.0% by volume or less, even more preferably 25.0% by volume or less, particularly preferably 20.0% by volume or less, and most preferably 15.0% by volume or less. When the total content of the conductive filler and the non-conductive filler is equal to or more than the above lower limit and equal to or less than the above upper limit, the coatability of the conductive paste can be improved, and the conduction reliability can be increased.

[0140] The total content of the conductive filler and the non-conductive filler in 100% by weight of the conductive paste is preferably 5.0% by weight or more, more preferably 10.0% by weight or more, and is preferably 40.0% by weight or less, more preferably 30.0% by weight or less, and even more preferably 25.0% by weight or less. When the total content of the conductive filler and the non-conductive filler is equal to or more than the lower limit and equal to or less than the upper limit, the coatability of the conductive paste can be improved, and the conduction reliability can be increased.

[0141] <Other Components> The conductive paste may contain components other than the curable compound, the curing agent, the conductive filler, and the non-conductive filler. The conductive paste may contain, as other components, a solvent, 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, an adhesion imparting agent, etc.

[0142] (Use of Conductive Paste) The use of the conductive paste according to the present invention is carried out by applying the above-mentioned conductive paste to a substrate having a planar area of ​​0.50 mm ２ The present invention relates to a use for bonding a chip having the following characteristics: In the use according to the present invention, a specific conductive paste and a chip having a specific planar area are used, which can suppress the occurrence of voids in the cured product, improve adhesion (between the substrate and the chip), and increase the reliability of electrical conduction.

[0143] From the viewpoint of further increasing the adhesiveness (between the substrate and the chip) and further increasing the reliability of conduction, the plane area of ​​the chip is preferably 0.04 mm ２ More preferably, 0.09 mm ２ More preferably, 0.16 mm ２ or more, preferably 0.50 mm ２ Less than or equal to 0.40 mm, more preferably ２ Less than 0.30 mm, more preferably ２ The above-mentioned plane area is the area in a plane (area in a planar view).

[0144] The use according to the present invention is also directed to the use of the above-mentioned conductive paste for obtaining an RFID inlay. In the use according to the present invention, a specific conductive paste is used, which can suppress the occurrence of voids in the cured product, improve adhesion (between the substrate and the chip), and increase the reliability of electrical conduction.

[0145] (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.

[0146] 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.

[0147] 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 conductive filler 1. The adhesive portion 84 is formed from the conductive paste containing conductive filler 1. The adhesive portion 84 is preferably formed by hardening the conductive paste containing conductive filler 1.

[0148] The substrate 82 has wiring 82a on its surface (upper surface). The chip 83 has electrodes 83a on its surface (lower surface). The wiring 82a and the electrodes 83a are electrically connected by conductive filler 1 in the adhesive portion 84.

[0149] 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 the 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 side; 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.

[0150] The RFID inlay and the manufacturing method thereof according to the present invention use a specific conductive paste, which can suppress the occurrence of voids in the adhesive portion of the RFID inlay.Furthermore, the RFID inlay and the manufacturing method thereof according to the present invention use a specific conductive paste, which can improve the adhesiveness between the substrate and the chip and can also improve the reliability of electrical conduction.

[0151] 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 disposing step, the second disposing step, and the bonding step. In this case, a plurality of RFID inlays can be manufactured continuously, thereby further improving the manufacturing efficiency of the RFID inlay.

[0152] When the roll-to-roll method is used, the transport speed of the substrate is not particularly limited.

[0153] Examples of methods for disposing the conductive paste include application using a dispenser, screen printing, and ejection using an inkjet device.

[0154] 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, thermal damage to the substrate can be reduced, and good electrical connection between the chip and the substrate can be achieved.

[0155] The applied pressure 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 applied pressure in the bonding step is equal to or greater than the above lower limit and equal to or less than the above upper limit, the adhesion between the substrate and the chip can be improved, and the electrical connection reliability can be improved.

[0156] The heating and pressurizing time in the bonding step is not particularly limited, and may be 2 seconds or more, 15 seconds or less, 10 seconds or less, 9 seconds or less, 7 seconds or less, or 5 seconds or less.

[0157] 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 to 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.

[0158] 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 substrate may be a resin board, a glass board, or a paper board.

[0159] 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.

[0160] 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.

[0161] 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 960 MHz), the wiring is preferably aluminum wiring.

[0162] From the viewpoint of suppressing 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.

[0163] 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.

[0164] The chip may be a semiconductor chip (IC chip) or the like.

[0165] The chip has an electrode on its surface. Examples of the electrode include a metal electrode such as a gold electrode, a nickel electrode, a tin electrode, an aluminum electrode, a silver electrode, a SUS electrode, a copper electrode, a molybdenum electrode, and a tungsten electrode. 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.

[0166] 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.

[0167] The shape of the tip is not particularly limited, and may be rectangular, triangular, or circular.

[0168] The planar area of ​​the chip is preferably 0.04 mm ２ More preferably, 0.09 mm ２ More preferably, 0.16 mm ２ or more, preferably 0.50 mm ２ Less than or equal to 0.40 mm, more 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 according to the present invention can be suitably used for bonding relatively small chips.

[0169] 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.

[0170] The following materials were prepared:

[0171] Curable compounds: (partial epoxy (meth)acrylate compounds) "EBECRYL3605" manufactured by Daicel Allnex Co., Ltd. (epoxy resin half acrylate, molecular weight 450, 1 (meth)acryloyl group, 1 epoxy group) "PNEA-50" manufactured by KSM Co., Ltd. (phenol novolac type epoxy half acrylate, molecular weight 460, (meth)acryloyl group / epoxy group=1)

[0172] (First (meth)acrylate compound) "M-140" manufactured by Toagosei Co., Ltd. (N-acryloyloxyethylhexahydrophthalimide, molecular weight 251, one (meth)acryloyl group) "EBECRYL IBOMA" manufactured by Daicel Allnex Corporation (isobornyl methacrylate, molecular weight 222, one (meth)acryloyl group) "MMA" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. (methyl methacrylate, molecular weight 100, one (meth)acryloyl group)

[0173] (Second (meth)acrylate compound) "EBECRYL3701" manufactured by Daicel-Allnex Corporation (modified epoxy acrylate, molecular weight 850, 2 (meth)acryloyl groups, 0 epoxy groups, 2 hydroxy groups) "EBECRYL3703" manufactured by Daicel-Allnex Corporation (amine-modified bisphenol A epoxy acrylate, molecular weight 850, 2 (meth)acryloyl groups, 0 epoxy groups, amino group present) "EBECRYL8209" manufactured by Daicel-Allnex Corporation (urethane (meth)acrylate compound, molecular weight 600, 4 (meth)acryloyl groups, hydroxy group present)

[0174] Curing agent: NOF Corporation "Perocta O" (peroxyester radical polymerization initiator) NOF Corporation "Perbutyl PV" (peroxyester radical polymerization initiator)

[0175] Conductive filler: "CN050" manufactured by Nikko Rica Corporation (nickel particles, average particle diameter: 5 μm); "NIB3B-205-S" manufactured by Sekisui Chemical Co., Ltd. (conductive particles comprising base particles (resin particles) and a conductive portion (nickel layer) disposed on the surface thereof, average particle diameter: 5 μm)

[0176] Non-conductive filler: "RX200" (silica silylate) manufactured by Nippon Aerosil Co., Ltd. "PM-20L" (dried silica) manufactured by Tokuyama Corporation

[0177] Additives: Shin-Etsu Silicones "KBM-5103" (3-acryloxypropyl methoxysilane) Shin-Etsu Silicones "KBM-403" (3-glycidoxypropyl trimethoxysilane)

[0178] Chip: IC chip (copper electrode, NXP "UCODE9", surface area: 0.22 mm ２ )

[0179] Substrate: PET film (long, resin film with aluminum wiring and an operating frequency in the UHF band (860 MHz to 960 MHz))

[0180] (Example 1) (1) Preparation of Conductive Paste The materials shown in Table 1 below were mixed in the amounts (wt %) shown in Table 1 below, and the mixture was stirred using a planetary mixer (Thinky Corporation's "Awatori Rentaro") to obtain a conductive paste (anisotropic conductive paste).

[0181] (2) Fabrication of RFID Inlay The obtained conductive paste was applied to a PET film by jet dispensing to a diameter of 800 μm to form a conductive paste layer (adhesive layer) (first placement step). Next, an IC chip (450 μm × 450 μm) was laminated on the surface opposite the PET film side of the conductive paste layer (adhesive layer) so that the wiring on the PET film surface and the electrodes on the IC chip surface faced each other (second placement step). Then, thermocompression bonding was performed under conditions of an upper heat tool of 180°C, a lower heat tool of 175°C, a pressure of 0.05 MPa, and a compression bonding time of 3 seconds to harden the conductive paste layer (adhesive layer) and form an adhesive bond. Furthermore, the wiring on the surface of the PET film and the electrodes on the surface of the IC chip were electrically connected by the conductive filler (conductive particles) in the adhesive bond to obtain a connection structure (adhesion step). The first arrangement step, the second arrangement step, and the bonding step were performed using a "DDA40000" (roll-to-roll method) manufactured by Muhlbauer GmbH. The resulting connection structure was cut into a size of 5 cm x 1.5 cm to obtain 50 RFID inlays.

[0182] Examples 2 to 11 and Comparative Examples 1 to 4 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 to 4.

[0183] (Evaluation) (1) Volumetric Shrinkage of Cured Product The specific gravity of the conductive paste (before curing) was measured at 23°C using a density meter (Shimadzu Corporation's "Accupyk II 1345"). Next, a measurement sample was prepared by the method described above. The specific gravity of the obtained measurement sample was measured at 23°C using a density meter (Shimadzu Corporation's "Accupyk II 1345"), and the obtained measurement value was taken as the specific gravity of the cured product. The volumetric shrinkage of the cured product was calculated using the following formula.

[0184] Volume shrinkage rate (%) of the cured product = (G1 - G2) x 100 / G2 G1: specific gravity of the conductive paste (before curing) at 23°C G2: specific gravity of the cured product at 23°C

[0185] (2) Void Generation Suppression Effect For 50 of the obtained RFID inlays, the hardened conductive paste in the fillet portion was observed using a microscope. The void generation suppression effect was evaluated according to the following criteria.

[0186] [Criteria for evaluating suppression of void generation] ○○: No voids of 50 μm or more in diameter were observed in any of the 50 RFID inlays. ○: One void of 50 μm or more but less than 100 μm in diameter was observed in any of the 50 RFID inlays, and no voids of 100 μm or more in diameter were observed in any of the 50 RFID inlays. ×: Two or more voids of 50 μm or more but less than 100 μm in diameter were observed in any of the 50 RFID inlays, or one or more voids of 100 μm or more in diameter were observed in any of the 50 RFID inlays.

[0187] (3) Adhesion For 50 of the obtained RFID inlays, the IC chip was peeled from the substrate using a die shear tester ("DAGE4000PLUS" manufactured by Nordson Corporation) at a tool height of 30 μm and a speed of 100 μm / sec, and the die shear strength was measured at 25° C. and the average value was calculated. The adhesion (die shear strength) was evaluated according to the following criteria.

[0188] [Adhesion evaluation criteria] ○○○: Average die shear strength is 7.0 N or more. ○○: Average die shear strength is 5.0 N or more and less than 7.0 N. ○: Average die shear strength is 3.0 N or more and less than 5.0 N. ×: Average die shear strength is less than 3.0 N.

[0189] (4) Conduction reliability After leaving 50 of the obtained RFID inlays at 85°C and 85% RH (high temperature and high humidity environment) for 168 hours, they were placed in a dark box that blocks external radio waves, and the sensitivity was measured at 25°C in the UHF band (860 MHz to 960 MHz) using a frequency reader ("Tagformance Pro" manufactured by Voyantic). The conduction reliability (frequency characteristics) was judged according to the following criteria.

[0190] [Criteria for judging continuity reliability] ○○: Peak sensitivity values ​​of all RFID inlays are less than -18 dBm. ○: Does not fall under either ○○ or ×. ×: Peak sensitivity value of at least one RFID inlay is -16.4 dBm or more.

[0191] The compositions of the conductive pastes and the results are shown in Tables 1 to 4 below.

[0192]

[0193]

[0194]

[0195]

[0196] REFERENCE SIGNS LIST 1... conductive filler 81... RFID inlay 82... substrate having wiring on its surface 82a... wiring 83... chip having electrode on its surface 83a... electrode 84... adhesive portion

Claims

1. A conductive paste comprising a curable compound, a curing agent, and a conductive filler. The curable compound comprises a partially epoxy (meth)acrylate compound, In 100% by weight of the conductive paste, the content of the partial epoxy (meth)acrylate compound is 10.0% by weight or more and 45.0% by weight or less. The conductive paste either does not contain a (meth)acrylic compound with a molecular weight of 150 or less, or contains a (meth)acrylic compound with a molecular weight of 150 or less in an amount of 15.0% by weight or less. A conductive paste wherein the conductive paste does not contain a first (meth)acrylate compound having one (meth)acryloyl group and no epoxy group, or contains the first (meth)acrylate compound in an amount of 25.0% by weight or less.

2. The conductive paste according to claim 1, wherein the conductive paste does not contain a first (meth)acrylate compound having one (meth)acryloyl group and no epoxy group, or contains the first (meth)acrylate compound in an amount of 10.0% by weight or less.

3. The conductive paste comprises a second (meth)acrylate compound having two or more (meth)acryloyl groups and one or more reactive functional groups other than (meth)acryloyl groups, The conductive paste according to claim 1 or 2, wherein the content of the second (meth)acrylate compound in 100% by weight of the conductive paste is 20.0% by weight or more and 70.0% by weight or less.

4. The conductive paste either contains or does not contain a non-conductive filler. The conductive paste according to claim 1 or 2, wherein the total content of the conductive filler and the non-conductive filler in 100% by volume of the conductive paste is 15.0% by volume or less.

5. A conductive paste according to claim 1 or 2, used to obtain an RFID inlay.

6. 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 described in claim 1 or 2. An RFID inlay in which the wiring and the electrodes are electrically connected by the conductive filler in the adhesive portion.

7. A first placement step of placing the conductive paste according to claim 1 or 2 on the surface of a substrate having wiring on its surface, A second arrangement step involves placing a chip having electrodes on its surface on the surface of the conductive paste opposite to the substrate side, A method for manufacturing an RFID inlay, comprising: a bonding step of forming an adhesive portion that bonds the substrate and the chip by heating and pressurizing the conductive paste, and electrically connecting the wiring and the electrode with the conductive filler in the adhesive portion.

8. The substrate is elongated, The method for manufacturing an RFID inlay according to claim 7, wherein in the first placement step, the second placement step, and the bonding step, the long substrate is transported by a roll-to-roll method to manufacture the RFID inlay.

9. The conductive paste according to claim 1 or 2 has a planar area of ​​0.50 mm². ２ The following are used for bonding chips.

10. Use of the conductive paste according to claim 1 or 2 for obtaining an RFID inlay.

Images