Electroconductive paste, RFID inlay, and method for producing RFID inlay

Abstract

Provided is an electroconductive paste that 1) has increased shelf life, 2) successfully demonstrates increased adhesion in the case of being mounted in a relatively short amount of time, and 3) successfully improves conduction reliability in the case of being mounted in a relatively short amount of time.　The electroconductive paste according to the present invention contains a thermosetting compound, a thermosetting agent, an electroconductive filler, and a non-electroconductive filler, the non-electroconductive filler containing a stabilizer. When the stabilizer is left to stand for 24 hours at 25°C and 50% RH, the percentage increase in weight thereof is at least 0.50 wt%.

Description

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

[0001] This invention relates to a conductive paste containing a conductive filler. Furthermore, this invention relates to an RFID inlay using the above-mentioned conductive paste and a method for manufacturing an RFID inlay. Additionally, this invention relates to the use of a conductive paste for bonding chips and the use of a conductive paste 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 and contactless RFID cards. In particular, UHF (Ultra High Frequency) band (860 MHz to 960 MHz) RFID inlays are attracting attention due to their long communication range, and are used for various items and purposes such as commuter passes, inventory management, distribution management, and history management.

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

[0004] In recent years, with the miniaturization of electronic components using RFID inlays, the chips used in RFID inlays have also become smaller. Therefore, there is a need for conductive pastes that have high adhesive properties and can be positioned with even greater precision on the wiring.

[0005] Patent Document 1 below discloses an adhesive applicable to electronic components. The adhesive is an acrylic adhesive composition comprising a radical initiator having a 10-hour half-life temperature of 80°C or lower, a vinylene-containing oligomer, and at least one diluent. The adhesive can be snap-cured at low temperatures, and its pot life at room temperature is 24 hours or more.

[0006] Patent Document 2, described below, discloses a conductive adhesive comprising a polymerizable acrylic compound, an organic peroxide, and solder particles, wherein the one-minute half-life temperature of the organic peroxide is lower than the solidus temperature of the solder particles.

[0007] Japanese Patent Publication No. 2006-144018 Japanese Patent Publication No. 2013-124330

[0008] To improve adhesion between the chip and the substrate, conductive paste is sometimes applied not only to the bonding area between the chip and the substrate, but also around the chip. The conductive paste is then cured by heating and pressurizing while a fillet is formed, and the chip is mounted to the substrate. In this case, heating may be insufficient at the fillet (especially the edges of the fillet), resulting in insufficient curing of the conductive paste. Consequently, the adhesion cannot be sufficiently improved, leading to a problem of reduced conductivity reliability between the upper and lower electrodes that should be connected in the resulting electronic component. This problem is particularly pronounced when mounting is done in a relatively short time (e.g., within 15 seconds).

[0009] Furthermore, generally speaking, increasing the curing properties of an adhesive (conductive paste) tends to shorten its pot life (working time). With conventional adhesives (conductive pastes), it is difficult to increase both the curing properties and storage stability.

[0010] The object of the present invention is to provide a conductive paste that can 1) improve storage stability, 2) improve adhesion when mounted in a relatively short time, and 3) improve conductivity reliability when mounted in a relatively short time. The present invention also aims to provide an RFID inlay using the above conductive paste and a method for manufacturing an RFID inlay. Furthermore, the present invention aims to provide the use of a conductive paste for bonding chips and the use of a conductive paste for obtaining an RFID inlay.

[0011] This specification discloses the following conductive pastes, RFID inlays, methods for manufacturing RFID inlays, the use of conductive pastes for bonding chips, and the use of conductive pastes for obtaining RFID inlays.

[0012] Item 1. A conductive paste comprising a thermosetting compound, a thermosetting agent, a conductive filler, and a non-conductive filler, wherein the non-conductive filler comprises a stabilizer, and the weight increase rate of the stabilizer when left at 25°C and 50% RH for 24 hours is 0.50% by weight or more.

[0013] Weight increase rate (weight %) = (W2 - W1) × 100 / W1 W1: Weight of the stabilizer before standing W2: Weight of the stabilizer after standing

[0014] Item 2. The conductive paste according to Item 1, wherein the pH of the mixture obtained by mixing 3.0 g of the stabilizer with 1000 mL of water at 25°C is 10.0 or higher and 14.0 or lower.

[0015] Item 3. The BET specific surface area of ​​the stabilizer is 2.5 m². ２ A conductive paste according to item 1 or 2, wherein the amount is 1 / g or more.

[0016] Item 4. The conductive paste according to any one of items 1 to 3, wherein the particle size D90 of the stabilizer, based on volume, is 10.0 μm or less.

[0017] Item 5. The conductive paste according to any one of items 1 to 4, wherein the stabilizer comprises calcium oxide.

[0018] Item 6. The conductive paste according to any one of items 1 to 5, wherein the thermosetting agent comprises a thermosetting agent that is solid at 25°C, or a microencapsulated thermosetting agent.

[0019] Item 7. The conductive paste according to any one of items 1 to 6, wherein the thermosetting agent comprises an amine curing agent.

[0020] Item 8. The conductive paste according to any one of items 1 to 7, wherein the content of the stabilizer in 100% by weight of the conductive paste is 1.5% by weight or more and 8.0% by weight or less.

[0021] Item 9. The conductive paste according to any one of items 1 to 8, wherein the conductive filler is conductive particles and the particle size of the conductive particles is 10 μm or less.

[0022] Item 10. The conductive paste is the conductive paste according to any one of items 1 to 9, used to obtain an RFID inlay.

[0023] Item 11. An RFID inlay comprising a substrate having wiring on its surface, a chip having electrodes on its surface, and an adhesive portion bonding the substrate and the chip, wherein the material of the adhesive portion is the conductive paste described in any one of items 1 to 10, and the wiring and the electrodes are electrically connected by the conductive filler in the adhesive portion.

[0024] Item 12. A method for manufacturing an RFID inlay, comprising: a first placement step of placing a conductive paste according to any one of items 1 to 10 on the surface of a substrate having wiring on its surface; a second placement step of placing a chip having electrodes on its surface on the surface of the conductive paste opposite to the substrate side; and an bonding step of heating and pressurizing the conductive paste to form an adhesive portion that bonds the substrate and the chip with the conductive paste, and electrically connecting the wiring and the electrodes with the conductive filler in the adhesive portion.

[0025] Item 13. The method for manufacturing an RFID inlay according to Item 12, wherein the substrate is elongated, and the elongated substrate is transported in a roll-to-roll manner during the first placement step, the second placement step, and the bonding step to manufacture the RFID inlay.

[0026] Item 14. A conductive paste described in any one of items 1 to 10, with a flat surface area of ​​0.50 mm². ２ The following are used for bonding chips.

[0027] Item 15. Use of any one of the conductive pastes described in items 1 to 10 to obtain an RFID inlay.

[0028] The conductive paste according to the present invention contains a thermosetting compound, a thermosetting agent, a conductive filler, and a non-conductive filler, and the non-conductive filler contains a stabilizer. In the conductive paste according to the present invention, when the stabilizer is left standing at 25 °C and 50% RH for 24 hours, the weight increase rate is 0.50% by weight or more. In the conductive paste according to the present invention, since the above configuration is provided, 1) the storage stability can be enhanced, 2) the adhesiveness can be enhanced when mounted in a relatively short time, and 3) the conduction reliability can be enhanced when mounted in a relatively short time.

[0029] FIG. 1 is a cross-sectional view schematically showing an RFID inlay using the conductive paste according to the first embodiment of the present invention.

[0030] Hereinafter, the details of the present invention will be described.

[0031] (Conductive Paste) The conductive paste according to the present invention contains a thermosetting compound, a thermosetting agent, a conductive filler, and a non-conductive filler, and the non-conductive filler contains a stabilizer. In the conductive paste according to the present invention, when the stabilizer is left standing at 25 °C and 50% RH for 24 hours, the following weight increase rate is 0.50% by weight or more.

[0032] Weight increase rate (% by weight) = (W2 - W1) × 100 / W1 W1: Weight of the stabilizer before standing W2: Weight of the stabilizer after standing

[0033] In a conventional conductive paste, the conductive paste may not be sufficiently cured. As a result, there is a problem that the adhesiveness cannot be sufficiently enhanced and the conduction reliability of the obtained electronic component is reduced. This problem is more prominent particularly when mounted in a relatively short time (for example, within 15 seconds). Further, in a conventional conductive paste, it is difficult to enhance the curability of the conductive paste and to enhance the storage stability.

[0034] The inventors of the present invention have found that the above problems can be solved by using a combination of specific materials and a stabilizer having a specific weight increase rate.

[0035] In other words, the conductive paste according to the present invention has the above configuration, which allows for a longer pot life (working time) (improved storage stability). Furthermore, the conductive paste according to the present invention has the above configuration, which allows for improved curing and sufficient curing even when mounted in a relatively short time (for example, within 15 seconds). As a result, adhesion can be improved even when mounted in a relatively short time, and the conductivity reliability between the upper and lower electrodes to be connected in the resulting electronic component can be improved. Specifically, even when mounted in a relatively short time, the initial communication characteristics and communication characteristics after high-temperature and high-humidity environment testing can be improved in the resulting electronic component.

[0036] Furthermore, the conductive paste according to the present invention can suppress the presence of uncured conductive paste in the cured product, even when mounted over a medium to long period of time. The conductive paste according to the present invention can suppress the presence of uncured conductive paste in the cured product under various mounting conditions.

[0037] The conductive paste according to the present invention is in paste form at 25°C. The conductive paste is used by dispensing it, for example, at 20°C to 50°C. The conductive paste according to the present invention is preferably used by dispensing it using a dispenser, and more preferably by dispensing it using a jet dispenser or a quantitative dispenser. The quantitative dispenser is preferably a micro-quantitative dispenser.

[0038] The viscosity (η25) of the conductive paste at 25°C is preferably 15 Pa·s or more, more preferably 25 Pa·s or more, even more preferably 40 Pa·s or more, preferably 200 Pa·s or less, more preferably 150 Pa·s or less, and even more preferably 100 Pa·s or less. If the viscosity (η25) is above the lower limit, it is possible to suppress the conductive paste from flowing out of the wiring. If the viscosity (η25) is below the upper limit, the conductive paste can be placed on fine wiring with high precision.

[0039] The viscosity (η25) mentioned above can be measured, for example, using an E-type viscometer on a conductive paste immediately after preparation, under conditions of 25°C and 5 rpm. Examples of such E-type viscometers include the "TV35 Viscometer" manufactured by Toki Sangyo Co., Ltd.

[0040] The ratio (ηA / η25) is defined as the ratio of the viscosity (ηA) of the conductive paste at 25°C after storage at 25°C and 50% RH for 24 hours to the viscosity (η25) of the conductive paste immediately after preparation at 25°C. The ratio (ηA / η25) is preferably 0.7 or higher, more preferably 0.8 or higher, even more preferably 0.9 or higher, preferably 2.0 or lower, more preferably 1.5 or lower, even more preferably 1.25 or lower, particularly preferably 1.2 or lower, and most preferably 1.1 or lower. If the ratio (ηA / η25) is above the lower limit, storage stability can be further enhanced, and leakage of the conductive paste from the wiring can be suppressed. If the ratio (ηA / η25) is below the upper limit, the conductive paste can be placed on fine wiring with high precision.

[0041] The viscosity (ηA) after storage can be measured, for example, by storing the conductive paste in a constant temperature and humidity chamber at 25°C and 50% RH for 24 hours, and then measuring it using an E-type viscometer at 25°C and 5 rpm. An example of an E-type viscometer is the "TV35 Viscometer" manufactured by Toki Sangyo Co., Ltd.

[0042] The above conductive paste has good adhesive properties. The above conductive paste is suitable for use as an adhesive. The above conductive paste is particularly suitable for bonding a substrate to a chip.

[0043] From the viewpoint of further improving conductivity reliability, the conductive paste is preferably an anisotropic conductive paste. The conductive paste is suitably used for electrical connection of electrodes. The conductive paste is suitably used to obtain connection structures. The conductive paste is suitably used to obtain electronic components. The conductive paste is particularly suitably used to obtain RFID inlays (use of the conductive paste to obtain RFID inlays). The conductive paste is suitably used for bonding and connecting a chip having electrodes on its surface to a substrate having wiring (antenna patterns) on its surface (use of the conductive paste to bond and connect a chip having electrodes on its surface to a substrate having wiring (antenna patterns) on its surface).

[0044] If the storage stability of conductive paste is low, the dispensing properties of the conductive paste will change before and after storage. RFID inlays require mass production and are manufactured, for example, by transporting long substrates using a roll-to-roll method. Therefore, in the manufacturing of RFID inlays, even slight irregularities in dispensing can easily lead to poor adhesion and poor conductivity, and thus excellent storage stability of the conductive paste is required. Furthermore, in the manufacturing of RFID inlays, it is required that the paste can be mounted in a relatively short time under atmospheric conditions. The conductive paste according to the present invention can 1) improve storage stability, 2) improve adhesion when mounted in a relatively short time, and 3) improve conductivity reliability when mounted in a relatively short time, so the conductive paste according to the present invention is particularly suitable for RFID inlays.

[0045] The conductive paste described above contains a thermosetting compound and is therefore thermosetting. The conductive paste described above is a thermosetting conductive paste. It is more preferable that the conductive paste described above is a thermosetting anisotropic conductive paste.

[0046] In the above conductive paste, when differential scanning calorimetry (DSC) is performed by heating the conductive paste from 30°C to 200°C at a heating rate of 10°C / min, it is preferable that the exothermic start temperature is 50°C or higher, the exothermic peak top temperature is 80°C to 125°C, and the exothermic end temperature is 180°C or lower. In this specification, the exothermic start temperature refers to the temperature at which the amount of heat generated begins to rise from the baseline. In this specification, the exothermic end temperature refers to the temperature at which the amount of heat generated decreases to 1% of the amount of heat generated at the peak top after reaching the peak top.

[0047] The differential scanning calorimetry (DSC) described above can be performed using the following method: Prepare a differential scanning calorimetry device. Place 5 mg of the conductive paste into a dedicated aluminum pan and cover it using a dedicated jig. Place this dedicated aluminum pan and an empty aluminum pan (reference) inside a heating unit and heat from 30°C to 200°C in an atmospheric environment at a heating rate of 10°C / min, and observe the reverse heat flow and non-reverse heat flow. The exothermic peak observed in the non-reverse heat flow is taken as the exothermic peak of the conductive paste. An example of the differential scanning calorimetry device described above is the "TA7000" manufactured by Hitachi High-Tech Science Corporation.

[0048] From the viewpoint of improving the storage stability and dispensing stability of the conductive paste, and further enhancing conductivity reliability when mounted in a relatively short time, the exothermic start temperature in the differential scanning calorimetry described above is preferably 50°C or higher, more preferably 60°C or higher. The upper limit of the exothermic start temperature is not particularly limited. The exothermic start temperature may be 110°C or lower, 105°C or lower, 100°C or lower, 90°C or lower, or 80°C or lower.

[0049] From the viewpoint of further improving conductivity reliability when implemented in a relatively short time, in the differential scanning calorimetry described above, the heat generation peak top temperature is preferably 80°C or higher, more preferably 85°C or higher, even more preferably 90°C or higher, preferably 125°C or lower, and more preferably 120°C or lower.

[0050] From the viewpoint of further improving conductivity reliability when implemented in a relatively short time, in the differential scanning calorimetry described above, the exothermic termination temperature is preferably 180°C or lower, more preferably 175°C or lower. The lower limit of the exothermic termination temperature is not particularly limited. The exothermic termination temperature may be 90°C or higher, or 95°C or higher.

[0051] In the differential scanning calorimetry described above, the absolute value of the difference between the heat generation start temperature and the heat generation end temperature is preferably 5°C or more, more preferably 10°C or more, even more preferably 15°C or more, particularly preferably 20°C or more, preferably 100°C or less, more preferably 95°C or less, even more preferably 90°C or less, particularly preferably 85°C or less, and most preferably 80°C or less. When the absolute value of the difference between the heat generation start temperature and the heat generation end temperature is above the lower limit and below the upper limit, the storage stability of the conductive paste can be further enhanced, and the conductivity reliability can be further enhanced when mounted in a relatively short time.

[0052] In the differential scanning calorimetry described above, it is preferable that there is one exothermic peak. In the differential scanning calorimetry described above, it is preferable that only one exothermic peak is observed. In the differential scanning calorimetry described above, it is preferable that two or more exothermic peaks are not observed.

[0053] The following explains each component contained in the conductive paste.

[0054] In this specification, "(meth)acrylate" refers to acrylate and methacrylate. "(meth)acrylic" refers to acrylic and methacrylic.

[0055] <Thermosetting Compounds> The thermosetting compounds described above are compounds that can be cured by heating. Examples of thermosetting compounds include epoxy compounds, (meth)acrylic compounds, oxetane compounds, episulfide compounds, phenol compounds, amino compounds, unsaturated polyester compounds, polyurethane compounds, silicone compounds, and polyimide compounds. Only one of the thermosetting compounds may be used, or two or more may be used in combination.

[0056] From the viewpoint of further improving conductivity reliability when implemented in a relatively short time, it is preferable that the thermosetting compound includes an epoxy compound.

[0057] Examples of the epoxy compounds mentioned above include glycidylamine-type epoxy compounds, bisphenol A-type epoxy compounds, bisphenol F-type epoxy compounds, bisphenol S-type epoxy compounds, phenol novolac-type epoxy compounds, biphenyl-type epoxy compounds, biphenyl novolac-type epoxy compounds, biphenol-type epoxy compounds, naphthalene-type epoxy compounds, fluorene-type epoxy compounds, phenol aralkyl-type epoxy compounds, naphthol aralkyl-type epoxy compounds, dicyclopentadiene-type epoxy compounds, anthracene-type epoxy compounds, epoxy compounds having an adamantane skeleton, epoxy compounds having a tricyclodecane skeleton, naphthylene ether-type epoxy compounds, and epoxy compounds having a triazine core as their skeleton.

[0058] The epoxy compound described above may also be a glycidyl ether compound. The glycidyl ether compound described above is a compound having at least one glycidyl ether group.

[0059] From the viewpoint of further improving conductivity reliability when implemented in a relatively short time, the thermosetting compound is more preferably an epoxy compound having an aromatic skeleton, and even more preferably a bisphenol A type epoxy compound or a bisphenol F type epoxy compound. The epoxy compound may be used alone, or two or more may be used in combination.

[0060] The molecular weight of the thermosetting compound is preferably 350 or more, more preferably 400 or more, even more preferably 450 or more, particularly preferably 500 or more, preferably 4500 or less, more preferably 4000 or less, even more preferably 3500 or less, and particularly preferably 3000 or less. When the molecular weight of the thermosetting compound is within the above range, the viscosity of the conductive paste can be adjusted to a suitable range, and the conductivity reliability can be further improved.

[0061] The molecular weight of the above-mentioned thermosetting compound refers to the molecular weight that can be calculated from the structural formula of the thermosetting compound, if the structural formula of the thermosetting compound can be identified. If the structural formula of the thermosetting compound cannot be identified, the molecular weight refers to the weight-average molecular weight. The weight-average molecular weight is the weight-average molecular weight in polystyrene terms, measured by gel permeation chromatography (GPC). Since the molecular weight of the above-mentioned thermosetting compound is relatively small, its structural formula can generally be identified. The weight-average molecular weight can be measured using the following measuring device and measurement conditions.

[0062] Measurement device: Waters GPC System (Waters 2690 + Waters 2414 (RI)) manufactured by Waters Japan Ltd. Column: Shodex GPC LF-G x 1, Shodex GPC LF-804 x 2 Mobile phase: THF 1.0 mL / min Sample concentration: 5 mg / mL Detector: Differential refractive index detector (RID) Standard material: Polystyrene (manufactured by TOSOH Corporation, weight-average molecular weight: 620-590000)

[0063] In 100% by weight of the above conductive paste, the content of the thermosetting compound is preferably 15% by weight or more, more preferably 20% by weight or more, even more preferably 30% by weight or more, still more preferably 40% by weight or more, particularly preferably 45% by weight or more, most preferably 50% by weight or more, preferably 90% by weight or less, more preferably 80% by weight or less, still more preferably 75% by weight or less, and particularly preferably 70% by weight or less. When the content of the thermosetting compound is above the lower limit and below the upper limit, the curing properties can be further enhanced, the adhesive properties can be further enhanced, and the conductivity reliability can be further enhanced when the product is mounted in a relatively short time. If the thermosetting compound contains two or more thermosetting compounds, the content of the thermosetting compound refers to the total content of each thermosetting compound.

[0064] In 100% by weight of the conductive paste, the content of the epoxy compound is preferably 15% by weight or more, more preferably 20% by weight or more, even more preferably 30% by weight or more, still more preferably 40% by weight or more, particularly preferably 45% by weight or more, most preferably 50% by weight or more, preferably 90% by weight or less, more preferably 80% by weight or less, still more preferably 75% by weight or less, and particularly preferably 70% by weight or less. When the content of the epoxy compound is above the lower limit and below the upper limit, the curing properties can be further improved, the adhesive properties can be further improved, and the conductivity reliability can be further improved when the product is mounted in a relatively short time.

[0065] <Thermosetting Agent> From the viewpoint of further improving curability when implemented in a relatively short time, it is preferable that the conductive paste contains a thermosetting agent that is solid at 25°C or a microencapsulated thermosetting agent. The conductive paste may contain a thermosetting agent that is solid at 25°C, or it may contain a microencapsulated thermosetting agent. From the viewpoint of further improving curability when implemented in a relatively short time, it is preferable that the thermosetting agent contains a thermosetting agent that is solid at 25°C, and more preferably a thermosetting agent that is solid at 25°C. From the viewpoint of further improving storage stability, further improving curability when implemented in a relatively short time, further improving adhesion, and further improving conductivity reliability, it is preferable that the thermosetting agent contains a microencapsulated thermosetting agent, and more preferably a microencapsulated thermosetting agent. Only one type of thermosetting agent may be used, or two or more types may be used in combination.

[0066] In the above-described microencapsulated thermosetting agent, the thermosetting agent component is contained within a microcapsule. In the above-described microencapsulated thermosetting agent, the contents of the microcapsule are the thermosetting agent component. The above-described microencapsulated thermosetting agent is capable of releasing the thermosetting agent component. In the above-described microencapsulated thermosetting agent, the material of the microcapsule is not particularly limited. Examples of materials for the microcapsule include ethylcellulose, polyvinyl alcohol, gelatin, and alginic acid.

[0067] From the viewpoint of further improving curability when implemented in a relatively short time, the melting point of the thermosetting agent, which is solid at 25°C, is preferably 50°C or higher, more preferably 60°C or higher, even more preferably 70°C or higher, preferably 150°C or lower, more preferably 140°C or lower, and even more preferably 130°C or lower.

[0068] The melting point of the thermosetting agent, which is solid at 25°C, can be calculated, for example, by performing differential scanning calorimetry (DSC) and observing the endothermic peak.

[0069] The above-mentioned thermosetting agent may be an anionic curing agent or a cationic curing agent. It is preferable that the above-mentioned thermosetting agent contains an anionic curing agent. Examples of the above-mentioned anionic curing agent include amine curing agents (amine compounds), imidazole curing agents, phenol curing agents (phenol compounds), and acid anhydride curing agents (acid anhydrides).

[0070] In the conductive paste described above, it is particularly preferable that the thermosetting compound includes an epoxy compound and the thermosetting agent includes an anionic curing agent. In this case, when the product is mounted in a relatively short time, the curing properties can be further enhanced, the adhesive properties can be further enhanced, and the conductivity reliability can be further improved.

[0071] The above-mentioned thermosetting agent (anionic curing agent) preferably contains an amine curing agent (amine compound), an imidazole curing agent, a phenol curing agent (phenol compound), or an acid anhydride curing agent (acid anhydride), and more preferably contains an amine curing agent. In these cases, when the product is mounted in a relatively short time, the curing properties can be further enhanced, the adhesive properties can be further enhanced, and the conductivity reliability can be further enhanced.

[0072] Examples of the above-mentioned amine curing agents include dicyandiamide, imidazole compounds, diaminodiphenylmethane, and diaminodiphenylsulfone. From the viewpoint of further improving conductivity reliability when implemented in a relatively short time, it is preferable that the above-mentioned amine curing agent contains dicyandiamide or an imidazole compound. The above-mentioned amine curing agent may be a thermosetting agent that is solid at 25°C, or it may be a microencapsulated thermosetting agent. The above-mentioned amine curing agent may be encapsulated in microcapsules.

[0073] The above imidazole curing agents include 2-undecylimidazole, 2-heptadecylimidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1,2-dimethylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole trimellitate, and 1-cyanoethyl-2-phenylimidazole tri Examples include melite, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanurate adduct, 2-phenylimidazole isocyanurate adduct, 2-methylimidazole isocyanurate adduct, 2-phenyl-4,5-dihydroxymethylimidazole, and 2-phenyl-4-methyl-5-dihydroxymethylimidazole.

[0074] Examples of the above-mentioned phenol curing agents include phenol novolac, o-cresol novolac, p-cresol novolac, t-butylphenol novolac, dicyclopentadiene cresol, poly-p-vinylphenol, bisphenol A type novolac, xylylene-modified novolac, decalin-modified novolac, poly(di-o-hydroxyphenyl)methane, poly(di-m-hydroxyphenyl)methane, and poly(di-p-hydroxyphenyl)methane. From the viewpoint of improving adhesion when mounted at relatively high temperatures, phenol resins having a melamine skeleton, phenol resins having a triazine skeleton, or phenol resins having an allyl group are preferred. From the viewpoint of further improving adhesion when mounted in a relatively short time, bisphenol A type novolac is preferred.

[0075] Examples of commercially available phenol curing agents include MEH-8005, MEH-8010, MEH-8015, and MEH-8000H (all manufactured by Meiwa Chemical Co., Ltd.), YLH903 (manufactured by Mitsubishi Chemical Corporation), LA-7052, LA-7054, LA-7751, LA-1356, and LA-3018-50P (all manufactured by DIC Corporation), and PS6313 and PS6492 (both manufactured by Gun-ei Chemical Co., Ltd.).

[0076] In 100% by weight of the conductive paste, the content of the thermosetting agent is preferably 1% by weight or more, more preferably 3% by weight or more, even more preferably 5% by weight or more, preferably 20% by weight or less, more preferably 18% by weight or less, and even more preferably 15% by weight or less. When the content of the thermosetting agent is above the lower limit and below the upper limit, storage stability can be further enhanced, and curability can be further enhanced when the product is mounted in a relatively short time.

[0077] With respect to 100 parts by weight of the thermosetting compound, the content of the thermosetting agent is preferably 3 parts by weight or more, more preferably 5 parts by weight or more, even more preferably 10 parts by weight or more, preferably 40 parts by weight or less, more preferably 30 parts by weight or less, and even more preferably 20 parts by weight or less. When the content of the thermosetting agent is above the lower limit and below the upper limit, storage stability can be further improved, and curability can be further improved when the product is mounted in a relatively short time.

[0078] <Conductive Filler> The conductive filler described above is not particularly limited. The conductive filler may be conductive particles or carbon fibers.

[0079] The shape of the conductive filler is not particularly limited. The conductive filler may be spherical, or it may have a shape other than spherical, or it may be flattened, etc.

[0080] The conductive filler is preferably a conductive particle. The conductive particles may be solder particles or metal particles. The metal particles may be metal powder. The conductive particles may comprise a base particle and a conductive portion disposed on the surface of the base particle. From the viewpoint of further improving conductivity reliability, it is preferable that the conductive particles comprise a base particle and a conductive portion disposed on the surface of the base particle.

[0081] The particle size (diameter) of the conductive filler (or, if the conductive filler is a conductive particle, the particle size of the conductive particle) is preferably 0.1 μm or more, more preferably 1 μm or more, even more preferably 2 μm or more, preferably 100 μm or less, more preferably 30 μm or less, even more preferably 20 μm or less, particularly preferably 15 μm or less, and most preferably 10 μm or less. When the particle size of the conductive filler is above the lower limit and below the upper limit, the conductivity reliability can be further improved when the assembly is completed in a relatively short time.

[0082] The particle diameter of the conductive filler described above is preferably the average particle diameter, and more preferably the 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 optical microscope and calculating the average value of the particle diameter of each conductive filler, or by performing a laser diffraction particle size distribution measurement.

[0083] When measuring the particle size of the conductive filler by observing 50 arbitrary conductive fillers with an electron microscope or optical microscope, for example, the measurement can be performed as follows: A conductive filler is added to Kulzer's "Technovit 4000" so that the conductive filler content is 30% by weight, and dispersed to create an embedded resin body for conductive filler inspection. An ion milling device (Hitachi High-Technologies Corporation's "IM4000") is used to cut a cross-section of the conductive filler, passing through the vicinity of the center of the conductive filler dispersed in the embedded resin body for conductive filler inspection. Then, using a field emission scanning electron microscope (FE-SEM), the image magnification is set to 25,000 times, and 50 conductive fillers are randomly selected and each conductive filler is observed. The equivalent circular diameter of each conductive filler is measured, and these are arithmetically averaged to obtain the particle size of the conductive filler.

[0084] The particle size of the conductive filler described above may be the particle size D50 of the conductive filler in the volume-based particle size distribution of the conductive filler. The particle size D50 of the conductive filler is the average diameter measured on a volume basis and is the median diameter (D50) value that corresponds to 50%. The particle size D50 of the conductive filler can be measured by laser diffraction / scattering methods, etc. That is, the particle size D50 of the conductive filler is the diameter value that corresponds to 50% when the particles are accumulated from the smallest particle size in the volume-based particle size distribution. A laser diffraction particle size distribution analyzer is preferably used as the measuring device. A commercially available laser diffraction particle size distribution analyzer is the "HELOS-KR" manufactured by Nippon Laser Co., Ltd. When using the "HELOS-KR" manufactured by Nippon Laser Co., Ltd., measurements can be performed with a dispersion pressure of 3.0 bar.

[0085] The coefficient of variation (CV value) of the particle size of the conductive filler is preferably 0% or more, preferably 10% or less, and more preferably 5% or less. If the coefficient of variation (CV value) of the particle size of the conductive filler is below the above upper limit, the conductivity reliability can be further improved. The lower limit of the coefficient of variation (CV value) of the particle size of the conductive filler is not particularly limited. The coefficient of variation (CV value) of the particle size of the conductive filler may be 0% or more, or 1% or more.

[0086] The coefficient of variation (CV value) mentioned above can be measured as follows.

[0087] CV value (%) = (ρ / Dn) × 100 ρ: Standard deviation of conductive filler particle size Dn: Mean value of conductive filler particle size

[0088] In 100% by weight of the above conductive paste, the content of the above conductive filler is preferably 0.1% by weight or more, more preferably 1% by weight or more, even more preferably 5% by weight or more, preferably 80% by weight or less, more preferably 60% by weight or less, even more preferably 50% by weight or less, particularly preferably 45% by weight or less, and most preferably 40% by weight or less. When the content of the above conductive filler is above the lower limit and below the upper limit, the conductivity reliability can be further improved when the product is mounted in a relatively short time.

[0089] With respect to 100 parts by weight of the thermosetting compound, the content of the conductive filler is preferably 2 parts by weight or more, more preferably 3 parts by weight or more, even more preferably 5 parts by weight or more, particularly preferably 7 parts by weight or more, preferably 35 parts by weight or less, more preferably 30 parts by weight or less, even more preferably 25 parts by weight or less, and particularly preferably 20 parts by weight or less. When the content of the conductive filler is above the lower limit and below the upper limit, the conductivity reliability can be further improved when the product is mounted in a relatively short time.

[0090] The conductive filler described above preferably contains a metal. Examples of such metals include gold, silver, copper, platinum, palladium, zinc, lead, aluminum, cobalt, indium, ruthenium, nickel, chromium, titanium, antimony, bismuth, germanium, and cadmium, as well as alloys thereof. In addition, tin-doped indium oxide (ITO) may be used as the metal. Only one of the metals may be used, or two or more may be used in combination.

[0091] From the viewpoint of further lowering 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 conductivity 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 conductivity reliability, it is particularly preferable that the conductive filler contains nickel on its outer surface.

[0092] When the conductive filler is a metal filler (when the conductive particles are metal particles), examples of metals that make up the metal filler include silver, copper, nickel, silicon, gold, titanium, and alloys such as solder. From the viewpoint of further effectively improving conductivity reliability, it is preferable that the material of the metal filler contains nickel or a nickel alloy, and it is more preferable that the material of the metal filler contains nickel or a nickel alloy. From the viewpoint of further effectively improving conductivity reliability, it is preferable that the outer surface portion of the metal filler contains nickel or a nickel alloy.

[0093] The details of conductive particles comprising a base particle and a conductive portion disposed on the surface of the base particle will be described below.

[0094] (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 also be core-shell particles comprising a core and a shell disposed on the surface of the core. The core may be an organic core, and the shell may be an inorganic shell.

[0095] The above-mentioned base material particles are more preferably resin particles or organic-inorganic hybrid particles, and may be resin particles or organic-inorganic hybrid particles. The effects of the present invention are exhibited even more effectively by using these preferred base material particles.

[0096] Various resins are suitably used as the material for the above-mentioned resin particles. Examples of materials for the above-mentioned 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, polyetheretherketone, polyethersulfone, divinylbenzene polymer, and polymers obtained by polymerizing one or more polymerizable monomers having ethylenically unsaturated groups. The above-mentioned divinylbenzene polymer may also be a divinylbenzene-based copolymer. Examples of the above-mentioned divinylbenzene copolymers include divinylbenzene-styrene copolymers and divinylbenzene-(meth)acrylic acid ester copolymers.

[0097] Since it is possible to design and synthesize resin particles having any desired compression characteristics suitable for conductive pastes, and the hardness of the resin particles can be easily controlled within a suitable range, it is preferable that the material of the above resin particles is a polymer obtained by polymerizing polymerizable monomers having multiple ethylenically unsaturated groups. In this case, only one type of polymer obtained by polymerizing polymerizable monomers having multiple ethylenically unsaturated groups may be used, or two or more types may be used in combination.

[0098] When the above resin particles are obtained by polymerizing a polymerizable monomer having an ethylenically unsaturated group, the polymerizable monomer having an ethylenically unsaturated group can be a non-crosslinked monomer or a crosslinked monomer.

[0099] The above non-crosslinked monomers include styrene 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 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; vinyl acid 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.

[0100] The above crosslinkable monomers 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) Examples 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, diallylacrylamide, diallyl ether, γ-(meth)acryloxypropyltrimethoxysilane, trimethoxysilylstyrene, and vinyltrimethoxysilane.

[0101] The above-mentioned polymerizable monomer having an ethylenically unsaturated group can be polymerized by known methods to obtain the resin particles. Examples of such methods include suspension polymerization in the presence of a radical polymerization initiator, and polymerization by swelling the monomer together with a radical polymerization initiator using non-crosslinked seed particles.

[0102] When the above-mentioned base material particles are inorganic particles excluding metal particles or organic-inorganic hybrid particles, examples of inorganic materials for the base material particles include silica, alumina, barium titanate, zirconia, and carbon black. Preferably, the inorganic material is not a metal. Examples of particles formed from silica include particles obtained by hydrolyzing a silicon compound having two or more hydrolyzable alkoxysilyl groups to form crosslinked polymer particles, and then firing them as needed. Examples of organic-inorganic hybrid particles include organic-inorganic hybrid particles formed from a crosslinked alkoxysilyl polymer and an acrylic resin.

[0103] The above organic-inorganic hybrid particles are preferably core-shell type organic-inorganic hybrid particles having a core and a shell disposed on the surface of the core. The core is preferably an organic core. The shell is preferably an inorganic shell. From the viewpoint of more effectively lowering the connection resistance between electrodes, the base particles are preferably organic-inorganic hybrid particles having an organic core and an inorganic shell disposed on the surface of the organic core.

[0104] Examples of materials for the organic core mentioned above include the resin particle material described above.

[0105] Examples of materials for the inorganic shell include the inorganic substances listed above as materials for the base particles. 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 using 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.

[0106] When the above-mentioned base material particles are metal particles, examples of metals that make up the metal particles include silver, copper, nickel, silicon, gold, titanium, and alloys such as solder.

[0107] The particle size of the above-mentioned base material particles 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, preferably 50 μm or less, more preferably 30 μm or less, even more preferably 20 μm or less, and particularly preferably 10 μm or less. When the particle size of the above-mentioned base material particles is above the lower limit, the conductivity reliability is further increased. Furthermore, aggregation becomes less likely when forming conductive parts on the surface of the base material particles, and aggregated conductive particles are less likely to form. When the particle size of the above-mentioned base material particles is below the upper limit, the conductive particles are easily compressed, and the connection resistance between electrodes connected via the conductive particles can be further effectively reduced.

[0108] The particle size of the above-mentioned substrate particles is preferably the average particle size, and more preferably the number-average particle size. The number-average particle size of the above-mentioned substrate particles can be measured, for example, as follows: Conductive particles are added to Kulzer's "Technovit 4000" so that the content of conductive particles is 30% by weight, and dispersed to create an embedded resin body for substrate particle inspection. An ion milling device (Hitachi High-Technologies Corporation's "IM4000") is used to cut out a cross-section of the conductive particles dispersed in the above-mentioned embedded resin body for substrate particle inspection, passing through the vicinity of the center of the substrate particles. Then, using a field emission scanning electron microscope (FE-SEM), the image magnification is set to 25,000 times, 50 conductive particles are randomly selected, and the substrate particles of each conductive particle are observed. The particle size of the substrate particles in each conductive particle is measured, and these are arithmetically averaged to obtain the average particle size of the substrate particles.

[0109] (Conductive part) The conductive part preferably contains a metal. The metal constituting the conductive part is not particularly limited. Examples of the metal include gold, silver, copper, platinum, palladium, zinc, lead, aluminum, cobalt, indium, ruthenium, nickel, chromium, titanium, antimony, bismuth, germanium, and cadmium, as well as alloys thereof. In addition, tin-doped indium oxide (ITO) may be used as the metal. Only one type of metal may be used, or two or more types may be used in combination. From the viewpoint of further lowering the connection resistance between electrodes, alloys containing tin, nickel, palladium, ruthenium, silver, copper, or gold are preferred, and nickel or palladium are more preferred.

[0110] From the viewpoint of more effectively improving conductivity reliability, it is preferable that the conductive part contains nickel, and it is more preferable that the outer surface portion of the conductive part contains nickel.

[0111] The nickel content in 100% by weight of the nickel-containing conductive part 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 part 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 nickel content in 100% by weight of the nickel-containing conductive part can be set by appropriately selecting the above lower limit and upper limit.

[0112] The conductive portion may be formed by a single layer. The conductive portion may be formed by multiple layers. That is, the conductive portion may have a laminated structure of two or more layers. When the conductive portion is formed by 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 electrodes becomes even lower.

[0113] The method for forming the conductive portion on the surface of the above-mentioned substrate particles is not particularly limited. Examples of methods for forming the conductive portion include electroless plating, electroplating, physical impact, mechanochemical reaction, physical vapor deposition or physical adsorption, and coating the surface of the substrate particles with metal powder or a paste containing metal powder and a binder. The method for forming the conductive portion is preferably electroless plating, electroplating, or physical impact. Examples of physical vapor deposition methods include vacuum deposition, ion plating, and ion sputtering. In the physical impact method, for example, a theta composer (manufactured by Tokuju Kogyosho) can be used.

[0114] The thickness of the conductive portion is preferably 0.005 μm or more, more preferably 0.01 μm or more, preferably 10 μm or less, more preferably 1 μm or less, and even more preferably 0.3 μm or less. When the thickness of the conductive portion is above the lower limit and below the upper limit, sufficient conductivity can be obtained, and the conductive particles can be sufficiently deformed during connection without becoming too hard.

[0115] When the conductive portion is formed by multiple layers, the thickness of the outermost conductive layer is preferably 0.001 μm or more, more preferably 0.01 μm or more, preferably 0.5 μm or less, and more preferably 0.1 μm or less. When the thickness of the outermost conductive layer is above the lower limit and below the upper limit, the conductive layer of the outermost layer becomes uniform, corrosion resistance is sufficiently high, and the connection resistance between electrodes can be sufficiently low.

[0116] The thickness of the conductive portion can be measured, for example, by observing the cross-section of the conductive particles using a transmission electron microscope (TEM).

[0117] 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 with protrusions on the outer surface of the conductive portion are used, the oxide film can be effectively removed by the protrusions when the conductive particles are placed between the electrodes and pressed together. As a result, the electrodes and the conductive portion make contact more reliably, and the connection resistance between the electrodes becomes even lower. Furthermore, when connecting electrodes, the protrusions of the conductive particles can effectively remove fillers between the conductive particles and the electrodes. As a result, the conductivity reliability between electrodes becomes even higher.

[0118] Methods for forming the above-mentioned protrusions include a method in which a core material is attached to the surface of a base particle and then a conductive part is formed by electroless plating, and a method in which a conductive part is formed on the surface of a base particle by electroless plating, then a core material is attached, and then a conductive part is formed by electroless plating. Alternatively, to form the protrusions, a method may be used in which a conductive part is formed on the base particle by electroless plating without using the above-mentioned core material, then a plating is deposited on the surface of the conductive part in the form of protrusions, and then a conductive part is formed by electroless plating.

[0119] Methods for attaching a core material to the surface of base particles include, for example, adding the core material to a dispersion of base particles and accumulating and attaching the core material to the surface of the base particles by van der Waals forces, and adding the core material to a container containing base particles and attaching the core material to the surface of the base particles by mechanical action such as rotating the container. From the viewpoint of controlling the amount of core material to be attached, the method of attaching the core material to the surface of base particles is preferably one in which the core material is accumulated and attached to the surface of base particles in a dispersion.

[0120] The materials constituting the core material mentioned above include conductive materials and non-conductive materials. Examples of conductive materials include metals, metal oxides, conductive nonmetals such as graphite, and conductive polymers. Examples of conductive polymers include polyacetylene. Examples of non-conductive materials include silica, alumina, titanium oxide, tungsten carbide, and zirconia. From the viewpoint of further improving the conductivity reliability between electrodes, it is preferable that the core material is a metal.

[0121] The above metals are not particularly limited. Examples of the above metals 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 conductivity reliability between electrodes, the above metals are preferably nickel, copper, silver, or gold. The above metals may be the same as or different from the metals constituting the conductive part.

[0122] The shape of the core material described above is not particularly limited. The core material is preferably in the form of a lump. Examples of the core material include particulate lumps, aggregates formed by the aggregation of multiple fine particles, and irregularly shaped lumps.

[0123] The particle size (diameter) of the core material is preferably 0.001 μm or larger, more preferably 0.05 μm or larger, preferably 0.9 μm or smaller, and more preferably 0.2 μm or smaller. When the particle size of the core material is above the lower limit and below the upper limit, the connection resistance between electrodes can be effectively reduced.

[0124] The particle size (diameter) of the core material described above is preferably the average particle size (average diameter), and more preferably the number-average particle size (number-average diameter). The particle size of the core material can be determined, for example, by observing 50 arbitrary core material samples with an electron microscope or optical microscope and calculating the average value of the particle size of each core material, or by performing laser diffraction particle size distribution measurement.

[0125] <Non-conductive filler> In the conductive paste described above, the non-conductive filler contains a stabilizer. The non-conductive filler may be used alone, or two or more may be used in combination.

[0126] Examples of the above-mentioned stabilizers include calcium oxide, zeolite (aluminosilicate), calcium sulfate, silica, titanium dioxide, calcium hydroxide, zinc oxide, and boron nitride. Only one of these stabilizers may be used, or two or more may be used in combination.

[0127] The above stabilizer preferably contains calcium oxide, zeolite (aluminosilicate), calcium sulfate, silica, or titanium oxide, more preferably calcium oxide, zeolite (aluminosilicate), or calcium sulfate, and even more preferably calcium oxide or zeolite (aluminosilicate). The above stabilizer is particularly preferably calcium oxide. In these cases, the conductivity reliability can be further improved when the components are mounted in a relatively short time. Specifically, when the components are mounted in a relatively short time, the initial communication characteristics and the communication characteristics after high-temperature and high-humidity environment testing of the resulting electronic components can be further improved.

[0128] The above stabilizer is preferably solid at 25°C. Specifically, it is preferable that the stabilizer (stabilizer alone) is solid at 25°C when it is not mixed with the above thermosetting compound, the above thermosetting agent, and the above conductive filler.

[0129] In the above conductive paste, it is preferable that the stabilizer is solid in the conductive paste at 25°C.

[0130] From the viewpoint of further improving conductivity reliability when implemented in a relatively short time, the stabilizer is preferably water-absorbing or hygroscopic, and more preferably hygroscopic. From the viewpoint of further improving conductivity reliability when implemented in a relatively short time, the stabilizer is even more preferably hygroscopic at 25°C and 50% RH.

[0131] The above stabilizer increases in weight when left at 25°C and 50% RH for 24 hours. When the above stabilizer is left at 25°C and 50% RH for 24 hours, the weight of the stabilizer after leaving it is greater than the weight of the stabilizer before leaving it.

[0132] When the above stabilizer is left at 25°C and 50% RH for 24 hours, the weight increase rate is 0.50% by weight or more. Because the above conductive paste has the above configuration, conductivity reliability can be improved when it is mounted in a relatively short time. Specifically, when it is mounted in a relatively short time, the initial communication characteristics and communication characteristics after high temperature and high humidity environment testing can be improved in the resulting electronic component.

[0133] Weight increase rate (weight %) = (W2 - W1) × 100 / W1 W1: Weight of the stabilizer before standing W2: Weight of the stabilizer after standing

[0134] The weight increase rate of the stabilizer is preferably 0.70% by weight or more, more preferably 1.0% by weight or more, even more preferably 1.3% by weight or more, particularly preferably 1.5% by weight or more, most preferably 1.6% by weight or more, preferably 10.0% by weight or less, more preferably 8.0% by weight or less, even more preferably 5.0% by weight or less, particularly preferably 4.0% by weight or less, and most preferably 3.0% by weight or less. If the weight increase rate of the stabilizer is above the lower limit, the conductivity reliability can be further improved when the assembly is completed in a relatively short time. If the weight increase rate of the stabilizer is below the upper limit, it is possible to prevent moisture from entering the connection part in the resulting connection structure (electronic component). From the viewpoint of further improving conductivity reliability when the assembly is completed in a relatively short time, it is particularly preferable that the stabilizer is solid at 25°C and has a weight increase rate of 0.50% by weight or more.

[0135] The weight increase rate of the above stabilizer can be measured by the following method. After placing the stabilizer in a desiccator at 25°C and 0% RH until its weight stops decreasing, remove the stabilizer from the desiccator at 25°C and 0% RH and measure the weight of the stabilizer before standing (W1). After removing the stabilizer from the desiccator at 25°C and 0% RH and leaving it at 25°C and 50% RH for 24 hours, measure the weight of the stabilizer after standing (W2). Weights (W1) and (W2) can be measured using an electronic balance. Weight (W1) is measured after removing the stabilizer from the desiccator at 25°C and 0% RH and leaving it at 25°C and 50% RH for 15 minutes. The weight change during these 15 minutes is small. It is preferable that the weight (W1) is about 1.0 g. The weight (W2) is measured after removing the stabilizer from a desiccator at 25°C and 0% RH and leaving it at 25°C and 50% RH for 24 hours.

[0136] Furthermore, if the stabilizer is calcium oxide particles, the calcium oxide particles can be obtained by performing a calcination process, and then, if necessary, crushing or classifying them to adjust the particle size. Also, if the stabilizer is calcium oxide particles (main component is calcium oxide), reducing the calcium hydroxide content in the calcium oxide particles (for example, making the weight ratio (calcium oxide content / calcium hydroxide content) 2.0 or higher) tends to result in a moderately large weight increase. The calcium hydroxide content in the calcium oxide particles can be adjusted by the calcination conditions during the production of the calcium oxide particles, particularly the calcination temperature, the amount supplied into the calcination furnace (residence time in the calcination furnace), and the size of the calcination furnace, as described in Japanese Patent Application Publication No. 2025-92871. In addition, the BET specific surface area of ​​the calcium oxide particles can be set to an appropriate range (for example, the BET specific surface area should be 10 m²). ２ / g to 30m ２By setting the weight to 1 / g, the weight increase rate can be made moderately large. The BET specific surface area of ​​calcium oxide can be adjusted by the firing conditions during the production of calcium oxide particles, particularly the firing temperature and the amount supplied into the firing furnace (residence time in the firing furnace), as described in Japanese Patent Publication No. 2025-92871. The BET specific surface area of ​​calcium oxide can also be adjusted by the grinding conditions and classification conditions. Furthermore, by setting the particle size of the calcium oxide particles to a moderate range (for example, setting the particle size D50 to 0.3 μm or more and 15 μm or less, the particle size D90 to 0.5 μm or more and 100 μm or less, and the particle size D97 to 1 μm or more and 260 μm or less), the weight increase rate can be made moderately large. It is widely known that the particle size of calcium oxide particles can be adjusted by the grinding conditions and classification conditions.

[0137] The shape of the stabilizer may be spherical, or other than spherical, or it may be flattened, etc. The stabilizer is preferably in particulate form.

[0138] In the volume-based particle size distribution of the above stabilizer, the particle size D50 of the stabilizer is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 1.0 μm or more, preferably 15.0 μm or less, more preferably 10.0 μm or less, even more preferably 7.5 μm or less, and particularly preferably 5.0 μm or less. When the particle size D50 of the above stabilizer is above the lower limit and below the upper limit, the dispersibility of the stabilizer is further improved, and the conductivity reliability can be further enhanced when it is mounted in a relatively short time.

[0139] In the volume-based particle size distribution of the above stabilizer, the particle size D90 of the stabilizer is preferably 0.5 μm or more, more preferably 1.0 μm or more, even more preferably 1.5 μm or more, particularly preferably 2.0 μm or more, preferably 35.0 μm or less, more preferably 30.0 μm or less, even more preferably 25.0 μm or less, even more preferably 20.0 μm or less, even more preferably 10.0 μm or less, particularly preferably 7.5 μm or less, and most preferably 5.0 μm or less. When the particle size D90 of the above stabilizer is above the lower limit and below the upper limit, the dispersibility of the stabilizer is further increased, and the conductivity reliability can be further improved when it is mounted in a relatively short time. Note that the particle size D90 of the above stabilizer is the same as or larger than the particle size D50 of the above stabilizer.

[0140] The ratio of the particle size D90 of the stabilizer to the particle size D50 of the conductive filler (or the particle size D50 of the conductive particles if the conductive filler is a conductive particle) is denoted as the ratio (particle size D90 of stabilizer / particle size D50 of conductive filler). The ratio (particle size D90 of stabilizer / particle size D50 of conductive filler) is preferably 0.1 or more, more preferably 0.2 or more, even more preferably 0.3 or more, particularly preferably 0.4 or more, preferably 10.0 or less, more preferably 6.0 or less, even more preferably 5.0 or less, even more preferably 4.0 or less, even more preferably 3.0 or less, particularly preferably 2.5 or less, and most preferably 2.0 or less. When the ratio (particle size D90 of stabilizer / particle size D50 of conductive filler) is above the lower limit and below the upper limit, the dispersibility of the stabilizer is further increased, and the conductivity reliability can be further improved when mounted in a relatively short time. If the above ratio (diameter D90 of stabilizer / particle size D50 of conductive filler) is above the above lower limit, that is, if the particle size D90 of the stabilizer is not excessively smaller than the particle size D50 of the conductive filler, then an excessive increase in the viscosity of the conductive paste can be suppressed, and the storage stability of the conductive paste can be further improved. If the above ratio (diameter D90 of stabilizer / particle size D50 of conductive filler) is below the above upper limit, then if the particle size D90 of the stabilizer is not excessively larger than the particle size D50 of the conductive filler, then the inhibition of conductivity by the stabilizer can be further prevented.

[0141] The particle sizes D50 and D90 of the stabilizer described above are average diameters measured on a volume basis, and represent the median diameter (D50) at 50% and the median diameter (D90) at 90%. The particle sizes D50 and D90 of the stabilizer described above can be measured by laser diffraction / scattering methods, etc. That is, the particle sizes D50 and D90 of the stabilizer described above are the diameter values ​​corresponding to 50% and 90% when the particle size distribution on a volume basis is accumulated from the smallest particle size. A laser diffraction particle size distribution analyzer is preferably used as the measuring device. A commercially available laser diffraction particle size distribution analyzer is the "HELOS-KR" manufactured by Nippon Laser Co., Ltd. When using the "HELOS-KR" manufactured by Nippon Laser Co., Ltd., measurements can be performed with a dispersion pressure of 3.0 bar.

[0142] The particle sizes D50 and D90 of the stabilizer can be controlled, for example, by selecting the stabilizer particles using a sieve. The particle sizes D50 and D90 of the stabilizer can be controlled by the following methods: Dispersing the stabilizer in a solvent and classifying it using a wet classifier; Classifying the dry powder form of the stabilizer using a dry classifier.

[0143] The coefficient of variation (CV value) of the particle size of the stabilizer is preferably 0% or more, preferably 10% or less, and more preferably 5% or less. When the coefficient of variation (CV value) of the particle size of the stabilizer is below the above upper limit, storage stability can be further improved, and conductivity reliability can be further improved when implemented in a relatively short time. The lower limit of the coefficient of variation (CV value) of the particle size of the stabilizer is not particularly limited. The coefficient of variation (CV value) of the particle size of the stabilizer may be 0% or more, or 1% or more.

[0144] The coefficient of variation (CV value) mentioned above can be measured as follows.

[0145] CV value (%) = (ρ / Dn) × 100 ρ: Standard deviation of stabilizer particle size Dn: Mean value of stabilizer particle size

[0146] The BET specific surface area of ​​the above stabilizer is preferably 1.0 m².２ / g or more, more preferably 1.5 m ２ / g or more, even more preferably 2.0 m ２ / g or more, still more preferably 2.5 m ２ / g or more, particularly preferably 3.0 m ２ / g or more, preferably 30.0 m ２ / g or less, more preferably 25.0 m ２ / g or less, still more preferably 20.0 m ２ / g or less. When the BET specific surface area of the stabilizer is not less than the above lower limit and not more than the above upper limit, the communication reliability (particularly, the communication characteristics after the high-temperature and high-humidity environment test) can be further enhanced when implemented in a relatively short time.

[0147] The BET specific surface area of the stabilizer can be measured from the nitrogen adsorption isotherm in accordance with the BET method. Examples of the measuring apparatus for the BET specific surface area of the stabilizer include "NOVA4200e" manufactured by Quantachrome Instruments.

[0148] The pH of the mixed solution (mixed solution containing the stabilizer) obtained by mixing 3.0 g of the stabilizer and 100 mL of water at 25°C is preferably 3.0 or more, more preferably 4.0 or more, even more preferably 7.0 or more, still more preferably 8.0 or more, particularly preferably 10.0 or more, most preferably 11.0 or more, and preferably 14.0 or less, more preferably 13.5 or less, still more preferably 13.0 or less. When the pH of the mixed solution containing the stabilizer is not less than the above lower limit and not more than the above upper limit, the communication reliability (particularly, the communication characteristics after the high-temperature and high-humidity environment test) can be further enhanced when implemented in a relatively short time.

[0149] The pH of the mixed solution containing the stabilizer can be measured, for example, by the following method. Put 3.0 g of the stabilizer into 100 mL of water at 25°C and dissolve it. Then, stir well and measure the pH at 25°C of the resulting solution using a pH meter. The temperature of the mixed solution during measurement is 25°C, and the measurement environment is 25°C and 50% RH. As the pH meter, commercially available products (for example, "F-52" manufactured by Horiba, Ltd.) can be used.

[0150] In 100% by weight of the conductive paste, the content of the non-conductive filler is preferably 0.5% by weight or more, more preferably 1.0% by weight or more, even more preferably 1.5% by weight or more, preferably 10.0% by weight or less, more preferably 8.0% by weight or less, even more preferably 6.0% by weight or less, and particularly preferably 5.0% by weight or less. If the content of the non-conductive filler is above the lower limit, the discharge stability of the conductive paste can be improved, and the conductivity reliability (especially the communication characteristics after high temperature and high humidity environment testing) can be further enhanced when the device is mounted in a relatively short time. If the content of the non-conductive filler is below the upper limit, the adhesion can be further enhanced when the device is mounted in a relatively short time.

[0151] In 100% by weight of the conductive paste, the content of the stabilizer is preferably 0.5% by weight or more, more preferably 1.0% by weight or more, even more preferably 1.5% by weight or more, preferably 10.0% by weight or less, more preferably 8.0% by weight or less, even more preferably 6.0% by weight or less, and particularly preferably 5.0% by weight or less. When the content of the stabilizer is above the lower limit, the discharge stability of the conductive paste can be improved, and the conductivity reliability (especially the communication characteristics after high temperature and high humidity environment testing) can be further enhanced when the device is mounted in a relatively short time. When the content of the stabilizer is below the upper limit, the adhesion can be further enhanced when the device is mounted in a relatively short time.

[0152] The ratio of the conductive filler content to the stabilizer content (conductive filler content / stabilizer content) is preferably 1.0 or higher, more preferably 2.0 or higher, even more preferably 3.0 or higher, preferably 30.0 or lower, more preferably 25.0 or lower, and even more preferably 20.0 or lower. When the above ratio (conductive filler content / stabilizer content) is above the lower limit and below the upper limit, the conductivity reliability (especially the communication characteristics after high temperature and high humidity environment testing) can be further improved when the device is mounted in a relatively short time.

[0153] The ratio of the content of the thermosetting agent to the content of the stabilizer (thermosetting agent content / stabilizer content) is preferably 1.0 or more, more preferably 2.0 or more, even more preferably 3.0 or more, particularly preferably 5.0 or more, preferably 30.0 or less, more preferably 20.0 or less, even more preferably 15.0 or less, particularly preferably 10.0 or less, and most preferably 8.0 or less. When the above ratio (thermosetting agent content / stabilizer content) is above the lower limit and below the upper limit, the conductivity reliability can be further improved when the device is mounted in a relatively short time.

[0154] <Other Components> The conductive paste described above may contain components other than the thermosetting compound, the thermosetting agent, the conductive filler, and the non-conductive filler. The conductive paste may also contain other components such as solvents, inorganic fillers, organic fillers, colorants, polymerization inhibitors, chain transfer agents, ultraviolet absorbers, antioxidants, defoamers, leveling agents, surfactants, slip agents, antiblocking agents, waxes, masking agents, deodorizers, fragrances, preservatives, antibacterial agents, antistatic agents, and adhesion enhancers.

[0155] (Use of conductive paste) The use according to the present invention is of the conductive paste described above with a planar area of ​​0.50 mm² ２ The following is an application for bonding chips. In the application according to the present invention, a specific conductive paste and a chip of a specific surface area are used, so that 1) storage stability can be improved, 2) adhesion can be improved when mounted in a relatively short time, and 3) conductivity reliability can be improved when mounted in a relatively short time.

[0156] Furthermore, the use of the present invention is for obtaining an RFID inlay using the conductive paste described above. In the use of the present invention, since a specific conductive paste is used, 1) storage stability can be improved, 2) adhesion can be improved when mounted in a relatively short time, and 3) conductivity reliability can be improved when mounted in a relatively short time.

[0157] (RFID inlay and method for manufacturing an RFID inlay) The RFID inlay according to the present invention comprises a substrate having wiring on its surface, a chip having electrodes on its surface, and an adhesive portion that adheres the substrate and the chip together. In the RFID inlay according to the present invention, the material of the adhesive portion is the conductive paste described above. In the RFID inlay according to the present invention, the wiring and the electrodes are electrically connected by the conductive filler in the adhesive portion.

[0158] Figure 1 is a schematic cross-sectional view showing an RFID inlay using a conductive paste according to the first embodiment of the present invention.

[0159] The RFID inlay 81 shown in Figure 1 comprises a substrate 82 having wiring on its surface, a chip 83 having electrodes on its surface, and an adhesive portion 84 that bonds the substrate 82 and the chip 83. The material of the adhesive portion 84 is a conductive paste containing a conductive filler 1. The adhesive portion 84 is formed from a conductive paste containing a conductive filler 1. Preferably, the adhesive portion 84 is formed by curing a conductive paste containing a conductive filler 1.

[0160] The substrate 82 has wiring 82a on its surface (top surface). The chip 83 has electrodes 83a on its surface (bottom surface). The wiring 82a and electrodes 83a are electrically connected by a conductive filler 1 in the adhesive portion 84.

[0161] 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 conductive paste described above 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 to the substrate side. (3) An bonding step of heating and pressurizing the conductive paste to form an adhesive portion that bonds the substrate and the chip, and electrically connecting the wiring and the electrodes with the conductive filler in the adhesive portion.

[0162] In the RFID inlay and RFID inlay manufacturing method according to the present invention, a specific conductive paste is used, which improves adhesion between the substrate and the chip and enhances conductivity reliability, even when the installation is completed in a relatively short time.

[0163] In the above-described method for manufacturing RFID inlays, it is preferable that the substrate is elongated, and that the elongated substrate is transported by a roll-to-roll method in the first placement step, the second placement step, and the bonding step to manufacture the RFID inlays. In this case, multiple RFID inlays can be manufactured continuously, further increasing the manufacturing efficiency of the RFID inlays.

[0164] When a roll-to-roll system is used, the transport speed of the substrate is not particularly limited.

[0165] Methods for distributing the conductive paste include, for example, application by a dispenser, screen printing, and ejection by an inkjet device.

[0166] The heating temperature in the bonding process described above is preferably 100°C or higher, more preferably 150°C or higher, preferably 350°C or lower, more preferably 300°C or lower, and even more preferably 250°C or lower. When the heating temperature in the bonding process described above is above the lower limit and below the upper limit, thermal damage to the substrate can be reduced, and good electrical connection between the chip and the substrate can be achieved.

[0167] The pressure applied during the bonding process is preferably 0.5 N or more, more preferably 1 N or more, preferably 3.5 N or less, more preferably 3 N or less, and even more preferably 2.5 N or less. When the pressure applied during the bonding process is above the lower limit and below the upper limit, the adhesion between the substrate and the chip can be improved, and the conductivity reliability can be enhanced.

[0168] The heating and pressing times in the bonding process described above are not particularly limited. The heating and pressing times in the bonding process described above 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.

[0169] The RFID inlay may be cut to a predetermined size as needed, or may be used after being cut. It is preferable to bond a plurality of the chips to a long substrate using a plurality of the adhesive portions. Multiple laminates of the chips and adhesive portions may be arranged on the long substrate. In the first arrangement step, it is preferable to place the conductive paste at a plurality of locations on the surface of the long substrate. In the second arrangement step, it is preferable to use a plurality of chips to place the chips on the surface opposite to the substrate side of each of the conductive pastes placed at the plurality of locations. After the chips are bonded to the long substrate using the adhesive portions, the long substrate may be cut.

[0170] The above-mentioned substrate is not particularly limited. Preferably, the substrate is a circuit board. Examples of the circuit board include resin films, flexible printed circuit boards, rigid-flexible circuit boards, glass substrates, and paper substrates. The substrate may be a resin substrate, a glass substrate, or a paper substrate.

[0171] The above substrate has wiring (antenna pattern) on its surface. Wiring (antenna pattern) is formed on the surface of the above substrate. Preferably, the above substrate has a base material and wiring (antenna pattern) arranged on the surface of the base material.

[0172] Examples of materials for the above-mentioned substrate include resin, glass, and paper. Examples of resins include PET (polyethylene terephthalate), PP (polypropylene), and PVC (polyvinyl chloride). The paper may be impregnated with epoxy resin or phenolic resin. From the viewpoint of further improving adhesion and from the viewpoint of manufacturing RFID inlays using a roll-to-roll method, the material of the above-mentioned substrate is preferably resin or paper, and more preferably PET (polyethylene terephthalate) or paper. The above-mentioned substrate may be resin, glass, or paper.

[0173] Examples of the above-mentioned wiring (antenna pattern) include gold wiring, nickel wiring, tin wiring, aluminum wiring, silver wiring, stainless steel 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), aluminum wiring is preferred.

[0174] From the viewpoint of suppressing deformation of the substrate due to heat during chip (e.g., IC chip) mounting and improving flexibility, the thickness of the substrate is preferably 20 μm or more, more preferably 30 μm or more, preferably 200 μm or less, and more preferably 100 μm or less.

[0175] The shapes of the substrate and base material are not particularly limited. From the viewpoint of manufacturing RFID inlays using a roll-to-roll method, the substrate and base material are preferably elongated. The lengths of the substrate and base material are not particularly limited. The lengths of the substrate and base material may be 1 m or more, 10 m or more, 5000 m or less, or 1000 m or less.

[0176] Examples of the above-mentioned chips include semiconductor chips (IC chips), etc.

[0177] The above-mentioned chip has electrodes on its surface. Examples of such electrodes include metal electrodes such as gold electrodes, nickel electrodes, tin electrodes, aluminum electrodes, silver electrodes, SUS electrodes, copper electrodes, molybdenum electrodes, and tungsten electrodes. From the viewpoint of further improving conductivity reliability, the electrodes are preferably copper electrodes or gold electrodes, and more preferably gold electrodes.

[0178] The number of electrodes per chip is not particularly limited. The number of electrodes per chip may be one or more, four or more, 20 or less, or 10 or less.

[0179] The shape of the chip described above is not particularly limited. The shape of the chip may be rectangular, triangular, or circular.

[0180] From the viewpoint of further improving adhesion (between the substrate and the chip) and further improving conductivity reliability, the surface area of ​​the chip is preferably 0.04 mm². ２ More preferably, 0.09 mm ２ More preferably 0.16 mm ２ The above is preferable, and preferably 0.50 mm ２ More preferably, 0.40 mm ２ Further preferably 0.30 mm ２ The following applies: The above-mentioned area is the area on a plane (area in a planar view). If the area of ​​the chip is greater than or equal to the lower limit, the conductive paste can be placed on fine wiring with high precision. If the area of ​​the chip is less than or equal to the upper limit, the conductivity reliability can be maintained even when the RFID inlay is left in a high-temperature, high-humidity environment for a long time. The conductive paste according to the present invention can be suitably used for bonding relatively small chips.

[0181] The present invention will be specifically described below with reference to examples and comparative examples. The present invention is not limited to the following examples.

[0182] The following materials were prepared.

[0183] Thermosetting compounds: DIC Corporation's "EXA830CRP" (bisphenol F type epoxy compound) and DIC Corporation's "EXA850CRP" (bisphenol A type epoxy compound).

[0184] Thermosetting agents: Asahi Kasei's "NovaCure HX9042HP" (resin containing amine curing agent (microencapsulated thermosetting agent), liquid at 25°C) and Ajinomoto Fine Techno's "Amicure PN23" (amine curing agent (non-microencapsulated thermosetting agent), solid at 25°C).

[0185] Conductive filler: Nikko Rica Co., Ltd. "CN050" (nickel particles, average particle size (D50): 5 μm)

[0186] Prepared stabilizer (non-conductive filler): Prepared product (1) (calcium oxide particles, weight increase rate: 1.80% by weight, pH of the mixture containing the stabilizer: 12.8, BET specific surface area: 18.00 m²) ２ / g, particle size D90: 2.7μm) Preparation (2) (Calcium oxide particles, weight increase rate: 1.90 wt%, pH of mixed solution containing stabilizer: 12.8, BET specific surface area: 16.68 m²) ２ / g, particle size D90: 25.5 μm) Preparation (3) (Calcium oxide particles prepared by grinding Preparation (2) in a dry grinder, weight increase rate: 1.90% by weight, pH of the mixture containing stabilizer: 12.8, BET specific surface area: 20.07 m²) ２ / g, particle size D90: 2.2 μm)

[0187] By changing the calcination conditions, grinding conditions, and / or classification conditions of the calcium oxide particles, different preparations (1) to (3) can be prepared.

[0188] Commercially available stabilizer (non-conductive filler): Calfine Co., Ltd. "F-Lime 1300K" (calcium oxide particles, weight increase rate: 1.70% by weight, pH of the mixture containing the stabilizer: 12.8, BET specific surface area: 3.37 m²) ２ ( / g, particle size D90: 10.7 μm) HWASUNG CHEMICAL "ANFOGEN #600HH" (calcium oxide particles, weight increase rate: 1.70 wt%, pH of mixed solution including stabilizer: 12.8, BET specific surface area: 2.95 m²) ２ ( / g, particle size D90: 3.4 μm) "PULVE440" manufactured by Irimajiri Lime Industry Co., Ltd. (calcium oxide particles, weight increase rate: 1.50 wt%, pH of mixed solution including stabilizer: 12.8, BET specific surface area: 1.71 m²) ２ ( / g, particle size D90: 23.8 μm) Omi Chemical Industry Co., Ltd. "CML#31" (calcium oxide particles, weight increase rate: 1.50 wt%, pH of mixed solution including stabilizer: 12.8, BET specific surface area: 1.17 m²) ２ / g, particle size D90: 30.8 μm) Tosoh Corporation "Zeolam A-5 FP 100#" (zeolite (aluminosilicate) particles, weight increase rate: 1.00 wt%, pH of mixed solution including stabilizer: 10.0, BET specific surface area: 2.34 m²) ２( / g, particle size D90: 6.3 μm) Sunes Gypsum Co., Ltd. "Hemihydrate Gypsum" (calcium sulfate particles, weight increase rate: 0.70% by weight, pH of mixed solution including stabilizer: 4.0, BET specific surface area: 3.05 m²) ２ ( / g, particle size D90: 8.3 μm) Admatex Co., Ltd. "SO-C4" (silica particles, weight increase rate: 0.02 wt%, pH of mixed solution including stabilizer: 7.0, BET specific surface area: 4.50 m²) ２ ( / g, particle size D90: 8.0 μm) Resonaq Ceramics "Super Titania F-10" (titanium oxide particles, weight increase rate: 0.17 wt%, pH of mixed solution including stabilizer: 7.8, BET specific surface area: 13.20 m²) ２ / g, particle size D90: 0.8 μm)

[0189] The weight increase rate of the stabilizer (the weight increase rate when the stabilizer is left at 25°C and 50% RH for 24 hours, as shown below) and the pH of the mixture containing the stabilizer (the pH of the mixture obtained by mixing 3.0 g of stabilizer with 1000 mL of water at 25°C) were measured using the method described above.

[0190] Weight increase rate (weight %) = (W2 - W1) × 100 / W1 W1: Weight of the stabilizer before standing W2: Weight of the stabilizer after standing

[0191] Chip: IC chip (copper electrode, NXP "UCODE9", surface area: 0.22 mm²) ２ )

[0192] Substrate: PET film (long-length resin film with aluminum wiring operating in the UHF band (860 MHz to 960 MHz))

[0193] (Example 1) (1) Preparation of conductive paste The materials shown in Table 1 below were mixed in the amounts (parts by weight) shown in Table 1 below, and stirred using a planetary stirring device (Thinky Co., Ltd. "Awatori Rentaro") to obtain a conductive paste (anisotropic conductive paste).

[0194] (2) Fabrication of RFID Inlay The obtained conductive paste was applied to the PET film using a jet dispensing method to form a conductive paste layer (adhesive layer) with a diameter of 800 μm (first placement step). Next, an IC chip (450 μm × 450 μm) was laminated on the surface of the conductive paste layer (adhesive layer) so that the wiring on the surface of the PET film and the electrodes on the surface of the IC chip faced each other (second placement step). Then, the conductive paste layer (adhesive layer) was cured by heat pressing under the conditions of an upper heat tool at 180°C, a lower heat tool at 175°C, a pressure of 0.05 MPa, and a pressing time of 3 seconds, thereby forming an adhesive part. Furthermore, the wiring on the surface of the PET film and the electrodes on the surface of the IC chip were electrically connected by a conductive filler in the adhesive part to obtain a connection structure (bonding step). The first placement step, the second placement step, and the bonding step described above were performed using a Muhlbauer "DDA40000" (roll-to-roll type). The resulting connection structure was cut to a size of 5 cm x 1.5 cm to obtain 50 RFID inlays.

[0195] (Examples 2-13 and Comparative Examples 1-4) Conductive pastes and RFID inlays were obtained in the same manner as in Example 1, except that the components and amounts of the conductive paste were changed as shown in Tables 1, 3, 5, and 7.

[0196] (Evaluation) (1) Adhesion (Die Shear Strength) The obtained RFID inlays were peeled off the chips from the substrate using a die shear tester (Nordson DAGE4000PLUS) with a tool height of 30 μm and a speed of 100 μm / sec, and the die shear strength at 25°C was evaluated. Adhesion was determined according to the following criteria.

[0197] [Adhesion Criteria] ○○: Die shear strength of 7.0 N or higher ○: Die shear strength of 4.0 N or higher but less than 7.0 N ×: Die shear strength less than 4.0 N

[0198] (2) Fifty RFID inlays, for which initial communication characteristics were obtained, were placed in a dark box that blocked external radio waves one hour after fabrication, and the peak sensitivity values ​​at 25°C in the UHF band (860 MHz to 960 MHz) were measured using a frequency reader (Voyantic "Tagformance Pro"). The initial communication characteristics were judged according to the following criteria.

[0199] [Initial communication characteristics determination criteria] ○○: The peak minimum sensitivity value of all RFID inlays is less than -18 dBm. ○: Neither ○○ nor × applies. ×: The peak minimum sensitivity value of at least one RFID inlay is -16.4 dBm or higher.

[0200] (3) Communication characteristics after high temperature and high humidity environment testing (2) After measuring the initial communication characteristics, 50 RFID inlays were left at 85°C and 85% RH (high temperature and high humidity environment) for 500 hours. Then, they were placed in a dark box that blocked external radio waves, and the peak sensitivity value at 25°C in the UHF band (860 MHz to 960 MHz) was measured using a frequency reader (Voyantic "Tagformance Pro"). The absolute difference between the peak sensitivity value after being left in the high temperature and high humidity environment and the initial peak sensitivity value was calculated. The communication characteristics after the high temperature and high humidity environment testing were judged according to the following criteria.

[0201] [Criteria for determining communication characteristics after high temperature and high humidity environment testing] ○○○: The absolute difference in peak sensitivity values ​​of all RFID inlays is less than 1.5 dBm ○○: One to two RFID inlays have an absolute difference in peak sensitivity values ​​of 1.5 dBm or more ○: Three to four RFID inlays have an absolute difference in peak sensitivity values ​​of 1.5 dBm or more ×: Five or more RFID inlays have an absolute difference in peak sensitivity values ​​of 1.5 dBm or more

[0202] (4) Storage Stability (Pot Life) The viscosity (η25) of the conductive paste at 25°C was measured using the method described above for the conductive paste immediately after preparation. The viscosity (ηA) of the conductive paste at 25°C and 5 rpm after being stored for 24 hours at 25°C and 50% RH was measured using the same method as for the viscosity (η25), and the ratio (ηA / η25) was calculated. The storage stability of the conductive paste was determined according to the following criteria.

[0203] [Storage Stability Criteria] ○○: Ratio (ηA / η25) is 0.9 or higher and 1.1 or lower ○: Ratio (ηA / η25) is 0.75 or higher and less than 0.9, or greater than 1.1 and 1.25 or lower ×: Ratio (ηA / η25) is less than 0.75 or greater than 1.25

[0204] The composition and details of the conductive paste, as well as the evaluation results, are shown in Tables 1 to 8 below.

[0205]

[0206]

[0207]

[0208]

[0209]

[0210]

[0211]

[0212]

[0213] 1...Conductive filler 81...RFID inlay 82...Substrate with wiring on its surface 82a...Wiring 83...Chip with electrodes on its surface 83a...Electrode 84...Adhesive part

Claims

1. A conductive paste comprising a thermosetting compound, a thermosetting agent, a conductive filler, and a non-conductive filler, wherein the non-conductive filler contains a stabilizer, and the weight increase rate of the stabilizer after being left at 25°C and 50% RH for 24 hours is 0.50% by weight or more. Weight increase rate (by weight) = (W2 - W1) × 100 / W1 W1: Weight of the stabilizer before standing W2: Weight of the stabilizer after standing 2. The conductive paste according to claim 1, wherein the pH of the mixture obtained by mixing 3.0 g of the stabilizer with 1000 mL of water at 25°C is 10.0 or higher and 14.0 or lower.

3. The BET specific surface area of ​​the stabilizer is 2.5 m². ２ The conductive paste according to claim 1 or 2, wherein the amount is 1 / g or more.

4. The conductive paste according to any one of claims 1 to 3, wherein the particle size D90 of the stabilizer, based on volume, is 10.0 μm or less.

5. The conductive paste according to any one of claims 1 to 4, wherein the stabilizer comprises calcium oxide.

6. The conductive paste according to any one of claims 1 to 5, wherein the thermosetting agent comprises a thermosetting agent that is solid at 25°C, or a microencapsulated thermosetting agent.

7. The conductive paste according to any one of claims 1 to 6, wherein the thermosetting agent comprises an amine curing agent.

8. The conductive paste according to any one of claims 1 to 7, wherein the content of the stabilizer in 100% by weight of the conductive paste is 1.5% by weight or more and 8.0% by weight or less.

9. The conductive paste according to any one of claims 1 to 8, wherein the conductive filler is conductive particles, and the particle size of the conductive particles is 10 μm or less.

10. The conductive paste according to any one of claims 1 to 9, which is used to obtain an RFID inlay.

11. An RFID inlay comprising a substrate having wiring on its surface, a chip having electrodes on its surface, and an adhesive portion bonding the substrate and the chip, wherein the material of the adhesive portion is the conductive paste described in any one of claims 1 to 10, and the wiring and the electrodes are electrically connected by the conductive filler in the adhesive portion.

12. A method for manufacturing an RFID inlay, comprising: a first placement step of placing a conductive paste according to any one of claims 1 to 10 on the surface of a substrate having wiring on its surface; a second placement step of placing a chip having electrodes on its surface on the surface of the conductive paste opposite to the substrate side; and an bonding step of heating and pressurizing the conductive paste to form an adhesive portion that bonds the substrate and the chip, and electrically connecting the wiring and the electrodes with the conductive filler in the adhesive portion.

13. The method for manufacturing an RFID inlay according to claim 12, wherein the substrate is elongated, and the elongated substrate is transported by a roll-to-roll method in the first placement step, the second placement step, and the bonding step to manufacture the RFID inlay.

14. A conductive paste according to any one of claims 1 to 10, with a planar area of ​​0.50 mm². ２ The following are used for bonding chips.

15. Use of the conductive paste according to any one of claims 1 to 10 for obtaining an RFID inlay.

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