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

Abstract

Provided is a conductive paste that can enhance storage stability, enhance curability, enhance adhesiveness, improve the tackiness of a cured product, and enhance conductive reliability even when implemented in a relatively short time. The conductive paste according to the present invention is a conductive paste containing a curable compound, a curing agent, and a conductive filler, and when differential scanning calorimetry is performed by heating the conductive paste from 30°C to 200°C at a heating rate of 10°C / min, the heat generation start temperature is 50°C or higher and 80°C or lower.

Description

Technical Field

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

Background Art

[0002] An RFID (Radio Frequency Identification) inlay capable of performing non-contact data transmission and reception is widely used in non-contact RFID tags, non-contact RFID cards, and the like. In particular, an RFID inlay in the UHF (Ultra High Frequency) band (860 MHz to 960 MHz) has attracted attention because of its long communication distance, and the UHF band RFID inlay is used for various articles and purposes such as commuter passes, inventory management, distribution management, and history management.

[0003] In an RFID inlay, a conductive paste containing a conductive filler and a binder resin may be used for bonding and connecting a chip having electrodes on its surface and a substrate having a wiring (antenna pattern) on its surface.

[0004] In recent years, with the miniaturization of electronic components using RFID inlays, the chips used in RFID inlays have also been miniaturized, and there is a demand for a conductive paste having high adhesiveness and capable of being arranged more precisely on the wiring.

[0005] Patent Document 1 below discloses an adhesive applicable to electronic components. The above adhesive is an acrylic adhesive composition containing 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 above adhesive can snap-cure at a low temperature, and the pot life of the above adhesive at room temperature is 24 hours or more.

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

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] In conventional adhesives (conductive pastes) as described in Patent Documents 1 and 2, the adhesiveness can be enhanced to a certain extent. However, in conventional conductive pastes, when electronic components are fabricated (mounted) in an air atmosphere using the conductive paste, due to the influence of oxygen, the polymerization reaction of the conductive paste does not proceed sufficiently, and there may be uncured portions in the cured product of the conductive paste. As a result, there is a problem that the adhesiveness cannot be sufficiently enhanced, the tackiness of the cured product cannot be improved, and the conduction reliability of the obtained electronic components cannot be sufficiently enhanced. This problem is particularly prominent when mounting is performed in a relatively short time (for example, within 15 seconds).

[0009] In general, when the curability of an adhesive (conductive paste) is enhanced, the pot life (usable time) tends to be shortened. With conventional adhesives (conductive pastes), it is difficult to enhance both the curability and the storage stability of the adhesive (conductive paste).

[0010] An object of the present invention is to provide a conductive paste that can 1) enhance storage stability and also has 2) high curability, 3) high adhesiveness, 4) good tackiness of the cured product, and 5) high conductive reliability even when implemented in a relatively short time. Another object of the present invention is to provide an RFID inlay using the above conductive paste and a method for manufacturing the RFID inlay.

Means for Solving the Problems

[0011] In this specification, the following conductive paste, RFID inlay, and method for manufacturing an RFID inlay are disclosed.

[0012] Item 1. A conductive paste containing a curable compound, a curing agent, and a conductive filler, wherein when the conductive paste is heated from 30°C to 200°C at a heating rate of 10°C / min for differential scanning calorimetry measurement, the heat generation start temperature is 50°C or higher and 80°C or lower.

[0013] Item 2. A conductive paste containing a curable compound, a curing agent, and a conductive filler, wherein the curing agent contains a secondary thiol curing agent or a primary thiol curing agent having no ester skeleton, and the conductive filler is a conductive particle including resin particles and a conductive layer disposed on the surface of the resin particles, or metal particles having a melting point exceeding 450°C.

[0014] Item 3. The conductive paste according to Item 1 or 2, wherein the curable compound contains a glycidylamine type epoxy compound.

[0015] Item 4. The conductive paste according to any one of Items 1 to 3, wherein the curing agent contains a thiol curing agent having two or more thiol groups.

[0016] Item 5. The conductive paste according to any one of Items 1 to 4, wherein the curing agent contains a thiol curing agent having a structure represented by the following formula (1).

[0017]

Chemical formula

[0018] In the formula (1), R1, R2, R3 and R4 each represent an alkylene group having 1 to 5 carbon atoms.

[0019] Item 6. The conductive paste according to any one of Items 1 to 5, wherein the curing agent contains a secondary thiol curing agent or a primary thiol curing agent having no ester skeleton, and the total content of the secondary thiol curing agent and the primary thiol curing agent having no ester skeleton in 100% by weight of the conductive paste is 5% by weight or more and 50% by weight or less.

[0020] Item 7. The conductive paste according to any one of Items 1 to 6, wherein the curing agent contains a secondary thiol curing agent.

[0021] Item 8. The conductive paste according to any one of Items 1 to 7, wherein when differential scanning calorimetry is performed by heating the conductive paste from 30°C to 200°C at a heating rate of 10°C / min, the end temperature of heat generation is 85°C or higher and 180°C or lower.

[0022] Item 9. The conductive paste according to any one of Items 1 to 8, wherein when differential scanning calorimetry is performed by heating the conductive paste from 30°C to 200°C at a heating rate of 10°C / min, the absolute value of the difference between the start temperature of heat generation and the end temperature of heat generation is 5°C or higher and 100°C or lower.

[0023] Item 10. The conductive paste according to any one of Items 1 to 9, wherein the curing agent contains a microcapsule type curing agent.

[0024] Item 11. The conductive paste according to Item 10, wherein the content of the microcapsule type curing agent in 100% by weight of the conductive paste is 5% by weight or more and 40% by weight or less.

[0025] Item 12. The conductive paste according to any one of Items 1 to 11, wherein the particle diameter of the conductive filler is 10 μm or less.

[0026] Item 13. The conductive paste according to any one of Items 1 to 12, wherein the content of the conductive filler in 100% by weight of the conductive paste is 0.1% by weight or more and 50% by weight or less.

[0027] Item 14. The conductive paste according to any one of Items 1 to 13, wherein the curing agent contains an amine curing agent that is solid at 25°C.

[0028] Item 15. The conductive paste according to any one of Items 1 to 14, further comprising a chelating agent.

[0029] Item 16. The conductive paste according to Item 15, wherein the chelating agent contains a borate ester.

[0030] Item 17. The conductive paste according to any one of Items 1 to 16, further comprising a non-conductive filler.

[0031] Item 18. The conductive paste according to Item 17, wherein the ratio of the particle diameter of the non-conductive filler to the particle diameter of the conductive filler is 0.5 or less.

[0032] Item 19. The conductive paste according to any one of Items 1 to 18, which is used to obtain an RFID inlay.

[0033] Item 20. An RFID inlay including a substrate having wiring on a surface, a chip having an electrode on a surface, and an adhesive portion bonding the substrate and the chip, wherein the material of the adhesive portion is the conductive paste according to any one of Items 1 to 19, and the wiring and the electrode are electrically connected by the conductive filler in the adhesive portion.

[0034] Item 21. A method for manufacturing an RFID inlay, comprising: a first placement step of placing the conductive paste according to any one of Items 1 to 19 on the surface of a substrate having wiring on its surface; a second placement step of placing a chip having an electrode on its surface on the surface of the conductive paste opposite to the substrate side; and an adhesion step of heating and pressurizing the conductive paste to form an adhesive portion bonding the substrate and the chip with the conductive paste, and electrically connecting the wiring and the electrode with the conductive filler in the adhesive portion.

[0035] Item 22. The method for manufacturing an RFID inlay according to Item 21, wherein the substrate is in a long shape, and in the first placement step, the second placement step, and the adhesion step, the long substrate is conveyed by a roll-to-roll method to manufacture the RFID inlay.

Advantages of the Invention

[0036] The conductive paste according to the present invention is a conductive paste containing a curable compound, a curing agent, and a conductive filler. When differential scanning calorimetry is performed by heating the conductive paste from 30°C to 200°C at a heating rate of 10°C / min, the heat generation start temperature is 50°C or higher and 80°C or lower. In the conductive paste according to the present invention, since the above configuration is provided, 1) the storage stability can be enhanced, and even when mounted in a relatively short time, 2) the curability can be enhanced, 3) the adhesiveness can be enhanced, 4) the tackiness of the cured product can be improved, and 5) the electrical communication reliability can be enhanced.

[0037] Another conductive paste according to the present invention is a conductive paste containing a curable compound, a curing agent, and a conductive filler. The curing agent includes a secondary thiol curing agent or a primary thiol curing agent having no ester skeleton. The conductive filler is a conductive particle including resin particles and a conductive layer disposed on the surface of the resin particles, or a metal particle having a melting point exceeding 450°C. In the conductive paste according to the present invention, since the above configuration is provided, 1) the storage stability can be enhanced, and even when mounted in a relatively short time, 2) the curability can be enhanced, 3) the adhesiveness can be enhanced, 4) the tackiness of the cured product can be improved, and 5) the conduction reliability can be enhanced.

Brief Description of Drawings

[0038]

Figure 1

Embodiments for Carrying Out the Invention

[0039] Hereinafter, the details of the present invention will be described.

[0040] (Conductive Paste) The conductive paste (first conductive paste) according to the present invention is a conductive paste containing a curable compound, a curing agent, and a conductive filler. In the conductive paste (first conductive paste) according to the present invention, when differential scanning calorimetry is performed by heating the conductive paste from 30°C to 200°C at a heating rate of 10°C / min, the heat generation start temperature is 50°C or higher and 80°C or lower.

[0041] In addition, the conductive paste (second conductive paste) according to the present invention is a conductive paste containing a curable compound, a curing agent, and a conductive filler. In the conductive paste (second conductive paste) according to the present invention, the curing agent includes a secondary thiol curing agent or a primary thiol curing agent having no ester skeleton. In the conductive paste (second conductive paste) according to the present invention, the conductive filler is a conductive particle including resin particles and a conductive layer disposed on the surface of the resin particles, or metal particles having a melting point exceeding 450°C.

[0042] In a conventional conductive paste, when an electronic component is manufactured (mounted) in an air atmosphere using the conductive paste, due to the influence of oxygen, the polymerization reaction of the conductive paste may not proceed sufficiently, and there may be uncured portions in the cured product of the conductive paste. As a result, there is a problem that the adhesiveness cannot be sufficiently increased and the conduction reliability of the obtained electronic component cannot be sufficiently increased. This problem is particularly prominent when only a (meth)acrylate compound is radically polymerized as the curable compound, when mounting is performed at a relatively low temperature (for example, 160°C to 200°C), or when mounting is performed in a relatively short time (for example, within 15 seconds). In addition, it is difficult to increase the curability and storage stability of a conventional adhesive (conductive paste).

[0043] The inventors have found that the above problems can be solved by controlling the heat generation start temperature when performing differential scanning calorimetry on the conductive paste within a specific range. In addition, the inventors have found that the above problems can be solved by using a conductive paste having a specific composition.

[0044] That is, in the conductive paste according to the present invention, since the above configuration is provided, the pot life (usable time) can be extended (storage stability can be enhanced). Further, in the conductive paste according to the present invention, since the above configuration is provided, even when mounting (heating) is performed in a relatively short time (for example, within 15 seconds), the curability can be enhanced and sufficient curing can be achieved. In particular, in the second conductive paste, since the above configuration is provided, even when mounting (heating) is performed at a relatively low temperature (for example, 160°C to 200°C) and in a relatively short time (for example, within 15 seconds), the curability can be enhanced and sufficient curing can be achieved. Further, in the conductive paste according to the present invention, since the above configuration is provided, even when mounting is performed in a relatively short time, the adhesiveness can be enhanced, the tackiness of the cured product can be improved, and the conduction reliability can be enhanced.

[0045] The conductive paste is heated from 30°C to 200°C at a temperature rising rate of 10°C / minute to perform differential scanning calorimetry (DSC). In the above differential scanning calorimetry, in the conductive paste (first conductive paste) according to the present invention, the heat generation start temperature is 50°C or higher and 80°C or lower. In the above differential scanning calorimetry, in the second conductive paste, it is preferable that the heat generation start temperature is 50°C or higher and 80°C or lower. In this specification, the heat generation start temperature refers to the temperature of the portion where the heat generation amount starts to rise from the baseline. Further, in this specification, the heat generation end temperature refers to the temperature of the portion where the heat generation amount has decreased to 1% of the heat generation amount at the heat generation peak top after reaching the heat generation peak top.

[0046] The above differential scanning calorimetry (DSC) can be performed by the following method. Prepare a differential scanning calorimeter. Take 5 mg of the above conductive paste in a dedicated aluminum pan and cover it with a dedicated jig. Place this dedicated aluminum pan and an empty aluminum pan (reference) in the heating unit, heat them in an air atmosphere from 30°C to 200°C 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 defined as the exothermic peak of the conductive paste. Examples of the above differential scanning calorimeter include "TA7000" manufactured by Hitachi High-Tech Science Corporation.

[0047] In the above differential scanning calorimetry, the exotherm start temperature can be measured. From the viewpoint of enhancing the storage stability and discharge stability of the conductive paste and further improving the conduction reliability even when mounted in a relatively short time, the exotherm start temperature is preferably 50°C or higher, more preferably 55°C or higher, still more preferably 60°C or higher, and preferably 80°C or lower, more preferably 75°C or lower, still more preferably 70°C or lower.

[0048] In the above differential scanning calorimetry, the exotherm peak top temperature can be measured. From the viewpoint of further improving the conduction reliability even when mounted in a relatively short time, the exotherm peak top temperature is preferably 80°C or higher, more preferably 90°C or higher, still more preferably 100°C or higher, and preferably 145°C or lower, more preferably 140°C or lower, still more preferably 130°C or lower.

[0049] In the above differential scanning calorimetry, the exotherm end temperature can be measured. From the viewpoint of further improving the conduction reliability even when mounted in a relatively short time, the exotherm end temperature is preferably 85°C or higher, more preferably 90°C or higher, still more preferably 95°C or higher, particularly preferably 100°C or higher, and preferably 180°C or lower, more preferably 175°C or lower, still more preferably 170°C or lower.

[0050] In the above differential scanning calorimetry, methods for adjusting the heat generation start temperature, heat generation peak top temperature, and heat generation end temperature to the above preferred ranges include increasing the content of the curing agent relative to the content of the curable compound, and adjusting the type and combination of the curing agent.

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

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

[0053] The conductive paste according to the present invention is in a paste state at 25°C. The above conductive paste is discharged and used, for example, at 20°C to 50°C. The conductive paste according to the present invention is preferably discharged and used by a jet dispenser.

[0054] The viscosity (η25) of the above conductive paste at 25°C is preferably 15 Pa·s or higher, more preferably 25 Pa·s or higher, still more preferably 40 Pa·s or higher, and preferably 200 Pa·s or lower, more preferably 150 Pa·s or lower, still more preferably 100 Pa·s or lower. When the viscosity (η25) is at the above lower limit or higher, it is possible to suppress the conductive paste from flowing out from the wiring. When the viscosity (η25) is at the above upper limit or lower, the conductive paste can be arranged on a fine wiring with high precision.

[0055] The above viscosity (η25) can be measured, for example, using an E-type viscometer under the conditions of 25°C and 5 rpm for the conductive paste immediately after production. Examples of the above E-type viscometer include the "TV35 type viscometer" manufactured by Toki Sangyo Co., Ltd.

[0056] The ratio of the viscosity (ηα) at 25°C of the conductive paste after storing at 25°C and 50% RH for 24 hours to the viscosity (η25) at 25°C of the conductive paste immediately after production is defined as the ratio (viscosity after storage (ηα) / viscosity immediately after production (η25)). The above ratio (viscosity after storage (ηα) / viscosity immediately after production (η25)) is preferably 0.7 or more, more preferably 0.8 or more, still more preferably 0.9 or more, preferably 1.25 or less, more preferably less than 1.25, still more preferably 1.2 or less, and particularly preferably 1.1 or less. When the above ratio (viscosity after storage (ηα) / viscosity immediately after production (η25)) is at or above the above lower limit, the storage stability can be further enhanced, and the outflow of the conductive paste from the wiring can be suppressed. When the above ratio (viscosity after storage (ηα) / viscosity immediately after production (η25)) is at or below the above upper limit or less than the above upper limit, the conductive paste can be accurately arranged on a fine wiring with high precision.

[0057] The above viscosity (ηα) after storage can be measured, for example, using an E-type viscometer under the conditions of 25°C and 5 rpm after storing the conductive paste in a thermo-hygrostat at 25°C and 50% RH for 24 hours. Examples of the above E-type viscometer include the "TV35 type viscometer" manufactured by Toki Sangyo Co., Ltd.

[0058] The above conductive paste has good adhesiveness. The above conductive paste is suitably used as an adhesive. The above conductive paste is particularly suitably used for adhering a substrate and a chip.

[0059] From the perspective of further enhancing the communication reliability, the conductive paste is preferably an anisotropic conductive paste. The conductive paste is suitably used for the electrical connection of electrodes. The conductive paste is suitably used for obtaining a connection structure. The conductive paste is suitably used for obtaining an electronic component. The conductive paste is particularly suitably used for obtaining an RFID inlay (use of the conductive paste for obtaining an RFID inlay). The conductive paste is suitably used for the adhesion and connection between a chip having an electrode on its surface and a substrate having a wiring (antenna pattern) on its surface (use of the conductive paste for adhering and connecting a chip having an electrode on its surface and a substrate having a wiring (antenna pattern) on its surface).

[0060] Hereinafter, each component contained in the conductive paste will be described.

[0061] In this specification, “(meth)acrylate” means acrylate and methacrylate. “(meth)acrylic” means acrylic and methacrylic.

[0062] <Curable compound> Examples of the curable compound include thermosetting compounds and photocurable compounds. The curable compound is preferably a thermosetting compound. The thermosetting compound is a compound that can be cured by heating. Examples of the thermosetting compound include (meth)acrylic compounds, oxetane compounds, epoxy compounds, episulfide compounds, phenol compounds, amino compounds, unsaturated polyester compounds, polyurethane compounds, silicone compounds, and polyimide compounds. Only one kind of the curable compound may be used, or two or more kinds may be used in combination.

[0063] From the perspective of further enhancing the communication reliability even when mounted in a relatively short time, the curable compound preferably contains an epoxy compound.

[0064] Examples of the epoxy compound include glycidylamine type epoxy compounds, bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, bisphenol S type epoxy compounds, phenol novolak type epoxy compounds, biphenyl type epoxy compounds, biphenyl novolak type epoxy compounds, bisphenol 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 nucleus in the skeleton, and the like.

[0065] From the viewpoint of further enhancing the conduction reliability even when implemented in a relatively short time, it is more preferable that the curable compound contains a bisphenol A type epoxy compound, a bisphenol F type epoxy compound, or a glycidylamine type epoxy compound, and it is even more preferable that the curable compound contains a glycidylamine type epoxy compound. In particular, in the first conductive paste, from the viewpoint of further enhancing the conduction reliability even when implemented in a relatively short time, it is even more preferable that the curable compound contains a glycidylamine type epoxy compound.

[0066] In particular, in the second conductive paste, from the viewpoint of further enhancing the curability and further enhancing the storage stability even when implemented (heated) at a relatively low temperature and in a relatively short time, it is even more preferable that the curable compound contains a bisphenol A type epoxy compound or a bisphenol F type epoxy compound. In this case, the curable compound may contain at least one of the bisphenol A type epoxy compound and the bisphenol F type epoxy compound, and may contain both.

[0067] The molecular weight of the above-mentioned curable compound is preferably 350 or more, more preferably 400 or more, still more preferably 450 or more, particularly preferably 500 or more, and preferably 4500 or less, more preferably 4000 or less, still more preferably 3500 or less, particularly preferably 3000 or less. When the molecular weight of the above-mentioned curable compound is within the above range, the viscosity of the conductive paste can be adjusted to a suitable range, and the electrical communication reliability can be further enhanced.

[0068] When the structural formula of the above-mentioned curable compound can be specified, the molecular weight of the curable compound means the molecular weight calculated from the structural formula. When the structural formula of the above-mentioned curable compound cannot be specified, the molecular weight means the weight average molecular weight. The above-mentioned weight average molecular weight indicates the weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC). Since the molecular weight of the above-mentioned curable compound is relatively small, the structural formula can generally be specified. The above-mentioned weight average molecular weight can be measured under the following measuring apparatus and measuring conditions.

[0069] Measuring apparatus: "Waters GPC System (Waters 2690 + Waters 2414 (RI))" manufactured by Waters Corporation, Japan Column: 1 piece of Shodex GPC LF-G, 2 pieces of Shodex GPC LF-804 Mobile phase: THF 1.0 mL / min Sample concentration: 5 mg / mL Detector: Differential refractive index detector (RID) Standard substance: Polystyrene (manufactured by TOSOH Corporation, weight average molecular weight: 620 - 590000)

[0070] In 100% by weight of the above conductive paste, the content of the above curable compound is preferably 15% by weight or more, more preferably 20% by weight or more, preferably 90% by weight or less, more preferably 80% by weight or less, and even more preferably 70% by weight or less. When the content of the above curable compound is equal to or higher than the above lower limit and equal to or lower than the above upper limit, even when mounted in a relatively short time, the curability can be further enhanced, the adhesiveness can be further enhanced, the tackiness of the cured product can be further improved, and the conduction reliability can be further enhanced. When the above curable compound contains two or more curable compounds, the content of the above curable compound indicates the total content of the two or more curable compounds.

[0071] In 100% by weight of the above conductive paste, the content of the above epoxy compound is preferably 15% by weight or more, more preferably 20% by weight or more, preferably 90% by weight or less, more preferably 80% by weight or less, and even more preferably 70% by weight or less. When the content of the above epoxy compound is equal to or higher than the above lower limit and equal to or lower than the above upper limit, even when mounted in a relatively short time, the curability can be further enhanced, the adhesiveness can be further enhanced, the tackiness of the cured product can be further improved, and the conduction reliability can be further enhanced.

[0072] In 100% by weight of the above conductive paste, the content of the above glycidylamine type epoxy compound is preferably 15% by weight or more, more preferably 20% by weight or more, preferably 90% by weight or less, more preferably 80% by weight or less, and even more preferably 70% by weight or less. When the content of the above glycidylamine type epoxy compound is equal to or higher than the above lower limit and equal to or lower than the above upper limit, even when mounted in a relatively short time, the curability can be further enhanced, the adhesiveness can be further enhanced, the tackiness of the cured product can be further improved, and the conduction reliability can be further enhanced.

[0073] In 100% by weight of the above conductive paste, the total content of the above bisphenol A type epoxy compound and the above bisphenol F type epoxy compound is preferably 15% by weight or more, more preferably 20% by weight or more, preferably 90% by weight or less, more preferably 80% by weight or less, and even more preferably 70% by weight or less. When the total content of the above bisphenol A type epoxy compound and the above bisphenol F type epoxy compound is within the above lower limit and the above upper limit, even when mounting (heating) is performed at a relatively low temperature and for a relatively short time, the curability can be further enhanced. Also, even when mounting is performed for a relatively short time, the adhesiveness can be further enhanced, the tackiness of the cured product can be made even better, and the conduction reliability can be further enhanced. When the above curable compound contains only one of the above bisphenol A type epoxy compound and the above bisphenol F type epoxy compound, the total content of the above bisphenol A type epoxy compound and the above bisphenol F type epoxy compound means the content of one compound. When the above curable compound contains both the above bisphenol A type epoxy compound and the above bisphenol F type epoxy compound, the total content of the above bisphenol A type epoxy compound and the above bisphenol F type epoxy compound means the total content of both compounds.

[0074] <Curing agent> The above curing agent is not particularly limited. As the above curing agent, a curing agent capable of curing the above curable compound can be appropriately used. The above curing agent may contain a curing accelerator.

[0075] Examples of the above curing agent include phenol compounds (phenol curing agents), active ester compounds, carbodiimide compounds (carbodiimide curing agents), amine compounds (amine curing agents), thiol compounds (thiol curing agents), phosphine compounds, dicyandiamide, and acid anhydrides. The above curing agent preferably has a functional group capable of reacting with the epoxy group of the above epoxy compound. Only one kind of the above curing agent may be used, or two or more kinds may be used in combination.

[0076] From the perspective of further enhancing the curability even when implemented in a relatively short time, the above curing agent preferably contains a thiol compound (thiol curing agent) or an amine compound (amine curing agent), more preferably contains a thiol compound (thiol curing agent), and even more preferably contains both a thiol compound (thiol curing agent) and an amine compound (amine curing agent).

[0077] The above thiol compound (thiol curing agent) may be a primary thiol compound (primary thiol curing agent) or a secondary thiol compound (secondary thiol curing agent).

[0078] In the second conductive paste, the above curing agent contains a secondary thiol curing agent or a primary thiol curing agent having no ester skeleton. In this case, the above curing agent may contain only at least one of a secondary thiol curing agent and a primary thiol curing agent having no ester skeleton, or may contain both.

[0079] "Secondary thiol" means a compound having a structure with one side chain on the carbon atom to which the SH group is bonded. "Primary thiol" means a compound having no side chain on the carbon atom to which the SH group is bonded.

[0080] In the first conductive paste, it is preferable that the above curing agent contains a secondary thiol curing agent or a primary thiol curing agent having no ester skeleton.

[0081] In the first conductive paste and the second conductive paste, the above curing agent may contain a primary thiol curing agent having no ester skeleton or a secondary thiol curing agent. The above secondary thiol curing agent may or may not have an ester skeleton. That is, in the second conductive paste, the above curing agent may contain a primary thiol curing agent having no ester skeleton, a secondary thiol curing agent having an ester skeleton, or a secondary thiol curing agent having no ester skeleton.

[0082] Examples of the above primary thiol compound (primary thiol curing agent) include stearyl 3-mercaptopropionate, 2-ethyl-2-{[(3-sulfanylpropanoyl)oxy]methyl}propane-1,3-diyl bis(3-sulfanylpropanoate), methoxybutyl β-mercaptopropionate, and 2-{2,4,6-trioxo-3,5-bis[2-(3-sulfanylpropanoyloxy)ethyl]-1,3,5-triazinane-1-yl}ethyl 3-sulfanylpropionate, etc.

[0083] Examples of the above primary thiol compound without an ester skeleton (primary thiol curing agent without an ester skeleton) include tetrahydro-1,3,4,6-tetrakis(3-mercaptopropyl)-imidazo[4,5-d]imidazole-2,5(1H,3H)-dione, tetrahydro-1,3,4,6-tetrakis(3-mercaptoethyl)-imidazo[4,5-d]imidazole-2,5(1H,3H)-dione, 3-(3-mercapto-propoxy)-2,2-bis-(3-mercapto-propoxymethyl)-propan-1-ol, and 3-{3-(3-mercapto-propoxy)-2,2-bis-[(3-mercaptopropoxy)methyl]propoxy}-propan-1-ol, etc.

[0084] Examples of the above secondary thiol compound (secondary thiol curing agent) include pentaerythritol tetrakis(3-mercaptobutyrate), 1,4-bis(3-mercaptobutyryloxy)butane, 1,3,5-tris(2-(3-sulfanylbutanoyloxy)ethyl)-1,3,5-triazinane-2,4,6-trione, and trimethylolpropane tris(3-mercaptobutyrate), etc.

[0085] From the perspective of further enhancing the curability even when implemented in a relatively short time, the above thiol compound (thiol curing agent) is preferably a secondary thiol compound (secondary thiol curing agent). From the perspective of further enhancing the curability even when implemented in a relatively short time, the above curing agent preferably contains a secondary thiol compound (secondary thiol curing agent).

[0086] From the viewpoint of further enhancing the curability even when implemented (heated) at a relatively low temperature and for a relatively short time, it is preferable that the conductive paste contains a thiol curing agent having no ester skeleton. From the viewpoint of further enhancing the curability even when implemented (heated) at a relatively low temperature and for a relatively short time, it is preferable that the conductive paste contains a primary thiol curing agent having no ester skeleton or a secondary thiol curing agent having no ester skeleton.

[0087] From the viewpoint of further enhancing the curability even when implemented (heated) at a relatively low temperature and for a relatively short time, it is preferable that the conductive paste contains a thiol curing agent having two or more thiol groups. From the viewpoint of further enhancing the curability even when implemented (heated) at a relatively low temperature and for a relatively short time, the number of thiol groups in the thiol curing agent is preferably two or more, more preferably three or more, and even more preferably four or more. The number of thiol groups in the thiol curing agent may be ten or less, or six or less. The range of the thiol groups in the thiol curing agent can be appropriately selected and set with the above lower limit value and the above upper limit value.

[0088] From the viewpoint of further enhancing the curability even when implemented (heated) at a relatively low temperature and for a relatively short time, it is particularly preferable that the conductive paste contains a thiol curing agent having two or more thiol groups and having no ester skeleton.

[0089] From the viewpoint of further enhancing the curability even when implemented (heated) at a relatively low temperature and for a relatively short time, it is particularly preferable that the conductive paste contains a thiol curing agent having a structure represented by the following formula (1).

[0090]

Chemical formula

[0091] In the above formula (1), R1, R2, R3, and R4 each represent an alkylene group having 1 to 5 carbon atoms.

[0092] In the above formula (1), the number of carbon atoms of the alkylene groups of R1, R2, R3, and R4 may be 2 or more.

[0093] The thiol curing agent having the structure represented by the above formula (1) is a thiol curing agent having two or more thiol groups and no ester skeleton.

[0094] In the above formula (1), R1, R2, R3, and R4 may be the same or different.

[0095] From the viewpoint of further enhancing the curability even when implemented (heated) at a relatively low temperature and for a relatively short time, in the above formula (1), R1, R2, R3, and R4 are each preferably an alkylene group having 2 or 3 carbon atoms. From the viewpoint of further enhancing the curability even when implemented (heated) at a relatively low temperature and for a relatively short time, in the above formula (1), the number of carbon atoms of the alkylene groups of R1, R2, R3, and R4 is preferably 2 or 3.

[0096] The above curing agent preferably contains tetrahydro-1,3,4,6-tetrakis(3-mercaptopropyl)-imidazo[4,5-d]imidazole-2,5(1H,3H)-dione, or tetrahydro-1,3,4,6-tetrakis(3-mercaptoethyl)-imidazo[4,5-d]imidazole-2,5(1H,3H)-dione. In this case, the curability can be further enhanced even when implemented (heated) at a relatively low temperature and for a relatively short time. The above curing agent more preferably contains tetrahydro-1,3,4,6-tetrakis(3-mercaptopropyl)-imidazo[4,5-d]imidazole-2,5(1H,3H)-dione. In this case, the curability can be further enhanced even when implemented (heated) at a relatively low temperature and for a relatively short time.

[0097] Examples of the amine compound (amine curing agent) include dihydrazide compounds, diethylamine, triethylamine, diethylenetetramine, triethylenetetramine, and 4,4-dimethylaminopyridine. The amine compound (amine curing agent) may be an amine adduct-based curing agent.

[0098] The amine compound (amine curing agent) is preferably solid at 25°C. The curing agent preferably contains an amine compound (amine curing agent) that is solid at 25°C.

[0099] The melting point of the amine compound (amine curing agent) that is solid at 25°C is preferably 50°C or higher, more preferably 55°C or higher, still more preferably 60°C or higher, and preferably 180°C or lower, more preferably 175°C or lower, still more preferably 170°C or lower. When the melting point is within the above lower limit and upper limit, the curability can be further enhanced and the tackiness of the cured product can be further improved even when mounted in a relatively short time.

[0100] The melting point of the amine compound (amine curing agent) that is solid at 25°C can be calculated from the endothermic peak, for example, by performing differential scanning calorimetry (DSC).

[0101] The curing agent preferably contains a secondary thiol compound (secondary thiol curing agent) and an amine compound (amine curing agent) that is solid at 25°C.

[0102] From the viewpoint of further enhancing the storage stability, the curing agent preferably contains a microcapsule-type curing agent.

[0103] Commercially available products may be used as the microcapsule-type curing agent. Examples of commercially available products of the microcapsule-type curing agent include Novacure HX3088, Novacure HX3941, Novacure HXA4922HP, Novacure HX3742, Novacure HX3722, and Novacure HXA9042HP (all manufactured by Asahi Kasei E-Materials Co., Ltd.).

[0104] From the viewpoint of further enhancing the storage stability, it is particularly preferable that the curing agent includes a secondary thiol curing agent or a primary thiol curing agent having no ester skeleton, and the microcapsule type curing agent.

[0105] In 100% by weight of the conductive paste, the content of the curing agent is preferably 5% by weight or more, more preferably 10% by weight or more, still more preferably 15% by weight or more, and preferably 50% by weight or less, more preferably 45% by weight or less, still more preferably 40% by weight or less. When the content of the curing agent is within the above lower limit and the above upper limit, even when mounted in a relatively short time, the curability can be further enhanced, the adhesiveness can be further enhanced, the tackiness of the cured product can be further improved, and the conduction reliability can be further enhanced. When the curing agent contains two or more kinds of curing agents, the content of the curing agent indicates the total content of the two or more kinds of curing agents. (The same shall apply hereinafter)

[0106] Based on 100 parts by weight of the content of the curable compound, the content of the curing agent is preferably 40 parts by weight or more, more preferably 50 parts by weight or more, preferably 90 parts by weight or less, more preferably 80 parts by weight or less. When the content of the curing agent is within the above lower limit and the above upper limit, even when mounted in a relatively short time, the curability can be further enhanced, the adhesiveness can be further enhanced, the tackiness of the cured product can be further improved, and the conduction reliability can be further enhanced.

[0107] In 100% by weight of the conductive paste, the content of the secondary thiol curing agent is preferably 5% by weight or more, more preferably 10% by weight or more, still more preferably 15% by weight or more, and preferably 50% by weight or less, more preferably 45% by weight or less, still more preferably 40% by weight or less. When the content of the secondary thiol curing agent is within the above lower limit and the above upper limit, even when mounted in a relatively short time, the curability can be further enhanced, the adhesiveness can be further enhanced, the tackiness of the cured product can be further improved, and the conduction reliability can be further enhanced.

[0108] In 100% by weight of the above conductive paste, the total content of the above secondary thiol curing agent and the amine curing agent that is solid at 25°C is preferably 7% by weight or more, more preferably 10% by weight or more, still more preferably 15% by weight or more, and preferably 50% by weight or less, more preferably 45% by weight or less, still more preferably 40% by weight or less. When the total content of the above secondary thiol curing agent and the amine curing agent that is solid at 25°C is equal to or higher than the above lower limit and equal to or lower than the above upper limit, even when mounted in a relatively short time, the curability can be further enhanced, the adhesiveness can be further enhanced, the tackiness of the cured product can be further improved, and the conduction reliability can be further enhanced.

[0109] With respect to 100 parts by weight of the content of the above curable compound, the total content of the above secondary thiol curing agent and the amine curing agent that is solid at 25°C is preferably 40 parts by weight or more, more preferably 50 parts by weight or more, preferably 90 parts by weight or less, more preferably 80 parts by weight or less. When the total content of the above secondary thiol curing agent and the amine curing agent that is solid at 25°C is equal to or higher than the above lower limit and equal to or lower than the above upper limit, even when mounted in a relatively short time, the curability can be further enhanced, the adhesiveness can be further enhanced, the tackiness of the cured product can be further improved, and the conduction reliability can be further enhanced.

[0110] In 100% by weight of the above conductive paste, the total content of the above secondary thiol curing agent and the primary thiol curing agent having no ester skeleton is preferably 5% by weight or more, more preferably 10% by weight or more, still more preferably 15% by weight or more, and preferably 50% by weight or less, more preferably 45% by weight or less, still more preferably 40% by weight or less. When the total content of the above secondary thiol curing agent and the primary thiol curing agent having no ester skeleton is within the above lower limit and the above upper limit, the curability can be further enhanced even when mounting (heating) is performed at a relatively low temperature and for a relatively short time. Further, when the total content of the above secondary thiol curing agent and the primary thiol curing agent having no ester skeleton is within the above lower limit and the above upper limit, the adhesiveness can be further enhanced, the tackiness of the cured product can be made better, and the conduction reliability can be further enhanced. When the above curing agent contains only one of the above secondary thiol curing agent and the primary thiol curing agent having no ester skeleton, the total content of the above secondary thiol curing agent and the primary thiol curing agent having no ester skeleton indicates the content of one curing agent. When the above curing agent contains both the above secondary thiol curing agent and the primary thiol curing agent having no ester skeleton, the total content of the above secondary thiol curing agent and the primary thiol curing agent having no ester skeleton indicates the total content of both curing agents.

[0111] In 100% by weight of the above conductive paste, the content of the above microcapsule type curing agent is preferably 5% by weight or more, more preferably 10% by weight or more, still more preferably 15% by weight or more, and preferably 50% by weight or less, more preferably 45% by weight or less, still more preferably 40% by weight or less. When the content of the above microcapsule type curing agent is within the above lower limit and the above upper limit, the storage stability can be further enhanced.

[0112] <Conductive filler> The above conductive filler is not particularly limited. The above conductive filler may be conductive particles or carbon fiber.

[0113] From the viewpoint of further enhancing the conduction reliability, in the first conductive paste, it is preferable that the conductive filler is conductive particles including resin particles and a conductive layer disposed on the surface of the resin particles, or metal particles having a melting point exceeding 450°C. In the second conductive paste, the conductive filler is conductive particles including resin particles and a conductive layer disposed on the surface of the resin particles, or metal particles having a melting point exceeding 450°C. In the second conductive paste, the conductive filler may be conductive particles including resin particles and a conductive layer disposed on the surface of the resin particles, or may be metal particles having a melting point exceeding 450°C. In the conductive particles including resin particles and a conductive layer disposed on the surface of the resin particles, the resin particles are base material particles. From the viewpoint of further enhancing the conduction reliability, in the first conductive paste, it is preferable that the conductive filler is metal particles having a melting point exceeding 450°C. From the viewpoint of further enhancing the conduction reliability, in the second conductive paste, it is preferable that the conductive filler is metal particles having a melting point exceeding 450°C.

[0114] The conductive filler in the second conductive paste is different from solder particles. In the second conductive paste, since the above configuration is provided, the discharge stability of the conductive paste can be enhanced. When only metal particles having a melting point of 450°C or lower (for example, solder particles) are used as the conductive filler, it is difficult to sufficiently enhance the discharge stability of the conductive paste as compared with the case where metal particles having a melting point exceeding 450°C are used.

[0115] In the above conductive paste (particularly the first conductive paste), the shape of the conductive filler is not particularly limited. The shape of the conductive filler may be spherical, may be a shape other than spherical, or may be flat or the like.

[0116] In the above conductive paste (especially the first conductive paste), the conductive filler is preferably conductive particles. The conductive particles may be solder particles or metal particles. The metal particles may be metal powder. The conductive particles may include a base material particle and a conductive portion disposed on the surface of the base material particle. From the viewpoint of further enhancing the conduction reliability, it is preferable that the conductive particles include a base material particle and a conductive portion disposed on the surface of the base material particle.

[0117] In the above conductive paste (especially the first conductive paste), when the conductive filler is conductive particles, the particle diameter of the conductive particles is preferably 0.1 μm or more, more preferably 1 μm or more, still more preferably 2 μm or more, and preferably 100 μm or less, more preferably 30 μm or less, still more preferably 10 μm or less. When the particle diameter of the conductive particles is equal to or greater than the lower limit and equal to or less than the upper limit, the conduction reliability can be further enhanced even when mounted in a relatively short time.

[0118] In the above conductive paste, the particle diameter of the conductive filler is preferably 0.1 μm or more, more preferably 1 μm or more, still more preferably 2 μm or more, and preferably 100 μm or less, more preferably 30 μm or less, still more preferably 10 μm or less. When the particle diameter of the conductive particles is equal to or greater than the lower limit and equal to or less than the upper limit, the conduction reliability can be further enhanced even when mounted in a relatively short time.

[0119] The particle diameter of the conductive particles and the conductive filler is preferably the average particle diameter, and more preferably the number average particle diameter. The average particle diameter of the conductive particles and the conductive filler can be obtained, for example, by observing 50 arbitrary conductive particles and conductive fillers with an electron microscope or an optical microscope and calculating the average value of the particle diameters of each conductive particle and conductive filler, or by performing laser diffraction particle size distribution measurement.

[0120] In the case of measuring the particle diameter of the above conductive particles by observing 50 arbitrary conductive particles with an electron microscope or an optical microscope, for example, it can be measured as follows. Add and disperse in "Technovit 4000" manufactured by Kulzer so that the content of the conductive particles becomes 30% by weight to produce an embedded resin body for conductive particle inspection. Cut out a cross-section of the conductive particles using an ion milling device ("IM4000" manufactured by Hitachi High-Technologies Corporation) so as to pass through the vicinity of the center of the conductive particles dispersed in the embedded resin body for conductive particle inspection. Then, using a field emission scanning electron microscope (FE-SEM), set the image magnification to 25,000 times, randomly select 50 conductive particles, and observe each conductive particle. Measure the equivalent circle diameter of each conductive particle and calculate their arithmetic mean as the particle diameter of the conductive particles. The same applies to the case of the conductive filler.

[0121] The coefficient of variation (CV value) of the particle diameter of the above conductive particles is preferably 10% or less, more preferably 5% or less. When the coefficient of variation of the particle diameter of the above conductive particles is below the above upper limit, the conduction reliability can be further enhanced. The lower limit of the coefficient of variation (CV value) of the particle diameter of the above conductive particles is not particularly limited. The coefficient of variation (CV value) of the particle diameter of the above conductive particles may be 0% or more, or may be 1% or more.

[0122] The coefficient of variation (CV value) can be measured as follows.

[0123] CV value (%) = (ρ / Dn) × 100 ρ: Standard deviation of the particle diameter of the conductive particles Dn: Average value of the particle diameter of the conductive particles

[0124] 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, still more preferably 5% by weight or more, and preferably 80% by weight or less, more preferably 60% by weight or less, still more preferably 50% by weight or less. When the content of the above conductive filler is not less than the above lower limit and not more than the above upper limit, the conduction reliability can be further enhanced even when mounted in a relatively short time.

[0125] With respect to 100 parts by weight of the content of the above curable compound, the content of the above conductive filler is preferably 2 parts by weight or more, more preferably 3 parts by weight or more, still more preferably 5 parts by weight or more, particularly preferably 7 parts by weight or more. With respect to 100 parts by weight of the content of the above curable compound, the content of the above conductive filler is preferably 35 parts by weight or less, more preferably 30 parts by weight or less, still more preferably 25 parts by weight or less, particularly preferably 20 parts by weight or less. When the content of the above conductive filler is not less than the above lower limit and not more than the above upper limit, the conduction reliability can be further enhanced even when mounted in a relatively short time.

[0126] The above conductive filler preferably contains a metal. Examples of the above metal include gold, silver, copper, platinum, palladium, zinc, lead, aluminum, cobalt, indium, ruthenium, nickel, chromium, titanium, antimony, bismuth, germanium, cadmium, and alloys thereof. Further, tin-doped indium oxide (ITO) may be used as the above metal. Only one kind of the above metal may be used, or two or more kinds may be used in combination.

[0127] From the viewpoint of further reducing the connection resistance between electrodes, the conductive filler preferably contains an alloy containing tin, nickel, palladium, ruthenium, silver, copper, or gold, and more preferably contains nickel or palladium. From the viewpoint of enhancing the corrosion resistance of the conductive filler and maintaining high conduction reliability, the conductive filler preferably contains nickel or gold, and more preferably contains nickel. From the viewpoint of enhancing the corrosion resistance of the conductive filler and maintaining high conduction reliability, it is particularly preferable that the outer surface of the conductive filler contains nickel.

[0128] When the conductive particles are metal particles, examples of the metal that is the material of the metal particles include silver, copper, nickel, silicon, gold, titanium, and alloys such as solder. From the viewpoint of more effectively enhancing conduction reliability, the material of the metal particles preferably contains nickel or a nickel alloy, and more preferably the material of the metal particles is nickel or a nickel alloy. From the viewpoint of more effectively enhancing conduction reliability, the outer surface portion of the metal particles preferably contains nickel or a nickel alloy.

[0129] Hereinafter, details of the conductive particles including base material particles and a conductive portion disposed on the surface of the base material particles will be described.

[0130] (Base material particles) Examples of the base material particles include resin particles, inorganic particles excluding metal particles, organic-inorganic hybrid particles, and metal particles. The base material particles are preferably base material particles excluding metal particles, and more preferably resin particles, inorganic particles excluding metal particles, or organic-inorganic hybrid particles. The base material particles may be core-shell particles including a core and a shell disposed on the surface of the core. The core may be an organic core, and the shell may be an inorganic shell.

[0131] The above base material particles are more preferably resin particles or organic-inorganic hybrid particles, and may be either resin particles or organic-inorganic hybrid particles. By using these preferred base material particles, the effects of the present invention can be more effectively exerted.

[0132] As the material of the above resin particles, various resins are preferably used. Examples of the material of the above 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, polyamideimide, polyetheretherketone, polyethersulfone, divinylbenzene polymer, and polymers obtained by polymerizing one or more of various polymerizable monomers having an ethylenically unsaturated group. The above divinylbenzene polymer may be a divinylbenzene copolymer. Examples of the above divinylbenzene copolymer include divinylbenzene-styrene copolymer and divinylbenzene-(meth)acrylate copolymer.

[0133] Since resin particles having any compression characteristics suitable for the conductive paste can be designed and synthesized, and the hardness of the resin particles can be easily controlled within a suitable range, the material of the above resin particles is preferably a polymer obtained by polymerizing one or two or more polymerizable monomers having a plurality of ethylenically unsaturated groups.

[0134] When the above resin particles are obtained by polymerizing a polymerizable monomer having an ethylenically unsaturated group, examples of the polymerizable monomer having an ethylenically unsaturated group include non-crosslinkable monomers and crosslinkable monomers.

[0135] Examples of the non-crosslinkable monomer include styrene-based monomers such as styrene and α-methylstyrene; carboxyl group-containing monomers such as (meth)acrylic acid, maleic acid, and maleic anhydride; alkyl (meth)acrylate compounds such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate; oxygen atom-containing (meth)acrylate compounds such as 2-hydroxyethyl (meth)acrylate, glycerol (meth)acrylate, polyoxyethylene (meth)acrylate, and glycidyl (meth)acrylate; nitrile-containing monomers such as (meth)acrylonitrile; vinyl ester compounds such as vinyl acetate, vinyl butyrate, vinyl laurate, and vinyl stearate; unsaturated hydrocarbons such as ethylene, propylene, isoprene, and butadiene; and halogen-containing monomers such as trifluoromethyl (meth)acrylate, pentafluoroethyl (meth)acrylate, vinyl chloride, vinyl fluoride, and chlorostyrene.

[0136] Examples of the crosslinkable monomer include polyfunctional (meth)acrylate compounds such as tetramethylolmethane tetra(meth)acrylate, tetramethylolmethane tri(meth)acrylate, tetramethylolmethane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, glycerol tri(meth)acrylate, glycerol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, (poly)tetramethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate; silane-containing monomers such as triallyl (iso)cyanurate, triallyl trimellitate, divinylbenzene, diallyl phthalate, diallyl acrylamide, diallyl ether, γ-(meth)acryloxypropyltrimethoxysilane, trimethoxysilylstyrene, vinyltrimethoxysilane, etc.

[0137] The resin particles can be obtained by polymerizing the polymerizable monomer having an ethylenically unsaturated group by a known method. Examples of this method include a method of suspension polymerization in the presence of a radical polymerization initiator, and a method of swelling and polymerizing a monomer together with a radical polymerization initiator using non-crosslinked seed particles.

[0138] When the base material particles are inorganic particles excluding metal particles or organic-inorganic hybrid particles, examples of the inorganic substance that is the material of the base material particles include silica, alumina, barium titanate, zirconia, and carbon black. It is preferable that the inorganic substance is not a metal. The particles formed by the silica are not particularly limited, and examples include particles obtained by hydrolyzing a silicon compound having two or more hydrolyzable alkoxysilyl groups to form crosslinked polymer particles and then performing firing as necessary. Examples of the organic-inorganic hybrid particles include organic-inorganic hybrid particles formed by a crosslinked alkoxysilyl polymer and an acrylic resin.

[0139] 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. It is preferable that the above core is an organic core. It is preferable that the above shell is an inorganic shell. From the viewpoint of more effectively reducing the connection resistance between electrodes, it is preferable that the above base material particles are organic-inorganic hybrid particles having an organic core and an inorganic shell disposed on the surface of the above organic core.

[0140] Examples of the material of the above organic core include the materials of the resin particles described above.

[0141] Examples of the material of the above inorganic shell include the inorganic substances listed as the material of the above base material particles. The material of the above inorganic shell is preferably silica. The above inorganic shell is preferably formed by sol-gel method of metal alkoxide into a shell-like substance on the surface of the above core and then firing the shell-like substance. The above metal alkoxide is preferably silane alkoxide. The above inorganic shell is preferably formed by silane alkoxide.

[0142] When the above base material particles are metal particles, examples of the metal that is the material of the metal particles include silver, copper, nickel, silicon, gold, titanium, and alloys such as solder.

[0143] The melting point of the above metal particles is preferably above 450 °C, more preferably 500 °C or higher, even more preferably 600 °C or higher, still more preferably 700 °C or higher, even still more preferably 800 °C or higher, and particularly preferably 900 °C or higher. When the melting point of the above metal particles is above the above lower limit, the discharge stability of the above conductive paste can be further enhanced. The melting point of the above metal particles may be 3000 °C or lower, or may be 2500 °C or lower. The range of the melting point of the above metal particles can be set by appropriately selecting the above lower limit value and the above upper limit value.

[0144] The particle diameter of the above-mentioned base material particles is preferably 0.01 μm or more, more preferably 0.05 μm or more, still more preferably 0.5 μm or more, further preferably 1 μm or more, and particularly preferably 3 μm or more, and is preferably 50 μm or less, more preferably 30 μm or less, still more preferably 20 μm or less, and particularly preferably 10 μm or less. When the particle diameter of the above-mentioned base material particles is equal to or greater than the above lower limit, the communication reliability becomes even higher. Further, when forming a conductive portion on the surface of the base material particles, it becomes difficult to aggregate, and it becomes difficult to form aggregated conductive particles. When the particle diameter of the above-mentioned base material particles is equal to or less than the above upper limit, the conductive particles are easily compressed sufficiently, and the connection resistance between the electrodes connected through the conductive particles can be made even lower more effectively.

[0145] The particle diameter of the above-mentioned base material particles is preferably the average particle diameter, and more preferably the number average particle diameter. The number average particle diameter of the above-mentioned base material particles can be measured, for example, as follows. Add and disperse in "Technovit 4000" manufactured by Kulzer so that the content of the conductive particles becomes 30% by weight to produce an embedding resin body for base material particle inspection. Using an ion milling apparatus ("IM4000" manufactured by Hitachi High-Technologies Corporation), cut out the cross-section of the conductive particles so as to pass near the center of the base material particles in the conductive particles dispersed in the above-mentioned embedding resin body for base material particle inspection. Then, using a field emission scanning electron microscope (FE-SEM), set the image magnification to 25,000 times, randomly select 50 conductive particles, and observe the base material particles of each conductive particle. Measure the particle diameter of the base material particles in each conductive particle, and calculate their arithmetic mean to obtain the average particle diameter of the base material particles.

[0146] (Conductive portion) The above conductive part preferably contains a metal. The metal constituting the above conductive part is not particularly limited. Examples of the above metal include gold, silver, copper, platinum, palladium, zinc, lead, aluminum, cobalt, indium, ruthenium, nickel, chromium, titanium, antimony, bismuth, germanium, cadmium, and alloys thereof. Further, tin-doped indium oxide (ITO) may be used as the above metal. Only one kind of the above metal may be used, or two or more kinds may be used in combination. From the viewpoint of further reducing the connection resistance between electrodes, an alloy containing tin, nickel, palladium, ruthenium, silver, copper, or gold is preferable, and nickel or palladium is more preferable.

[0147] From the viewpoint of more effectively enhancing the conduction reliability, it is preferable that the above conductive part contains nickel, and it is more preferable that the outer surface part of the above conductive part contains nickel.

[0148] The content of nickel in 100% by weight of the conductive part containing nickel is preferably 10% by weight or more, more preferably 50% by weight or more, even more preferably 60% by weight or more, still more preferably 70% by weight or more, and particularly preferably 90% by weight or more. The content of nickel in 100% by weight of the conductive part containing nickel may be 99% by weight or less, 90% by weight or less, or 70% by weight or less.

[0149] The above conductive part may be formed by one layer. The above conductive part may be formed by a plurality of layers. That is, the above conductive part may have a laminated structure of two or more layers. When the above conductive part is formed by a plurality of 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 these preferable metals, the connection resistance between electrodes becomes even lower.

[0150] The method for forming the conductive portion on the surface of the base material particles is not particularly limited. Examples of the method for forming the conductive portion include, for example, a method by electroless plating, a method by electroplating, a method by physical collision, a method by mechanochemical reaction, a method by physical vapor deposition or physical adsorption, and a method of coating the surface of the base material particles with a paste containing metal powder or a metal powder and a binder. The method for forming the conductive portion is preferably a method by electroless plating, electroplating or physical collision. Examples of the method by physical vapor deposition include methods such as vacuum evaporation, ion plating and ion sputtering. In the method by physical collision, for example, a Seater Composer (manufactured by Tokuju Kousakusho Co., Ltd.) is used.

[0151] 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 still more preferably 0.3 μm or less. When the thickness of the conductive portion is equal to or more than the lower limit and equal to or less than the upper limit, sufficient conductivity can be obtained, and the conductive particles do not become too hard, so that the conductive particles can be sufficiently deformed during connection.

[0152] When the conductive portion is formed of a plurality of layers, the thickness of the outermost layer of the conductive portion 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 layer of the conductive portion is equal to or more than the lower limit and equal to or less than the upper limit, the outermost layer of the conductive portion becomes uniform, the corrosion resistance becomes sufficiently high, and the connection resistance between the electrodes can be sufficiently lowered.

[0153] 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).

[0154] Core material: Preferably, the conductive particles have a plurality of protrusions on the outer surface of the conductive portion. An oxide film is often formed on the surface of the electrode connected by the conductive particles. When using conductive particles having protrusions on the outer surface of the conductive portion, by arranging the conductive particles between the electrodes and crimping them, the oxide film can be effectively removed by the protrusions. Therefore, the electrode and the conductive portion are more reliably in contact with each other, and the connection resistance between the electrodes becomes even lower. Further, when connecting the electrodes, the filler between the conductive particles and the electrodes can be effectively removed by the protrusions of the conductive particles. Therefore, the conduction reliability between the electrodes becomes even higher.

[0155] Examples of the method for forming the protrusions include a method of forming a conductive portion by electroless plating after attaching a core material to the surface of base material particles, and a method of forming a conductive portion by electroless plating on the surface of base material particles, then attaching a core material, and further forming a conductive portion by electroless plating. Also, in order to form protrusions, a method such as forming a conductive portion by electroless plating on base material particles without using the core material, then depositing plating in a protrusion shape on the surface of the conductive portion, and further forming a conductive portion by electroless plating may be used.

[0156] Examples of the method for attaching a core material to the surface of base material particles include, for example, adding a core material to a dispersion of base material particles and accumulating and attaching the core material to the surface of the base material particles by van der Waals forces, and adding a core material to a container containing base material particles and attaching the core material to the surface of the base material particles by a mechanical action such as rotation of the container. From the viewpoint of controlling the amount of the core material to be attached, the method of attaching the core material to the surface of the base material particles is preferably a method of accumulating and attaching the core material to the surface of the base material particles in the dispersion.

[0157] Examples of the material constituting the core material include conductive materials and non-conductive materials. Examples of the conductive material include metals, metal oxides, conductive non-metals such as graphite, and conductive polymers. Examples of the conductive polymer include polyacetylene. Examples of the non-conductive material include silica, alumina, titanium oxide, tungsten carbide, and zirconia. From the viewpoint of further enhancing the conduction reliability between electrodes, it is preferable that the core material is a metal.

[0158] The metal is not particularly limited. Examples of the metal include metals such as gold, silver, copper, platinum, zinc, iron, lead, tin, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, germanium, and cadmium, and alloys composed of two or more metals such as tin-lead alloy, tin-copper alloy, tin-silver alloy, tin-lead-silver alloy, and tungsten carbide. From the viewpoint of further enhancing the conduction reliability between electrodes, the metal is preferably nickel, copper, silver, or gold. The metal may be the same as or different from the metal constituting the conductive portion.

[0159] The shape of the core material is not particularly limited. The shape of the core material is preferably a lump. Examples of the core material include particulate lumps, agglomerates formed by aggregation of a plurality of fine particles, and amorphous lumps.

[0160] The particle diameter of the core material is preferably 0.001 μm or more, more preferably 0.05 μm or more, preferably 0.9 μm or less, and more preferably 0.2 μm or less. When the particle diameter of the core material is within the above lower limit and the above upper limit, the connection resistance between electrodes can be effectively reduced.

[0161] The particle diameter of the core material is preferably an average particle diameter, and more preferably a number average particle diameter. The particle diameter of the core material can be determined, for example, by observing 50 arbitrary core materials with an electron microscope or an optical microscope and calculating the average value of the particle diameters of each core material, or by performing laser diffraction particle size distribution measurement.

[0162] <Non-conductive filler> Preferably, the conductive paste further contains a non-conductive filler. The non-conductive filler is a filler having no conductivity.

[0163] Examples of the non-conductive filler include silica, titania, alumina, sorbitol, and zinc oxide. Only one type of the non-conductive filler may be used, or two or more types may be used in combination.

[0164] From the viewpoint of further enhancing the storage stability, the non-conductive filler preferably contains titania, silica, or alumina, more preferably contains silica or titania, and even more preferably contains titania.

[0165] From the viewpoint of further enhancing the storage stability, the non-conductive filler is preferably solid at 25°C. From the viewpoint of further enhancing the storage stability, the non-conductive filler is preferably present in a dispersed state in the conductive paste.

[0166] When the non-conductive filler is solid at 25°C, the particle diameter of the non-conductive filler is preferably 0.001 μm or more, more preferably 0.01 μm or more, even more preferably 0.1 μm or more, preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 1 μm or less. When the particle diameter of the non-conductive filler is equal to or greater than the lower limit and equal to or less than the upper limit, the storage stability can be further enhanced.

[0167] The particle diameter of the non-conductive filler is preferably an average particle diameter, and more preferably a number average particle diameter. The average particle diameter of the non-conductive filler can be obtained, for example, by observing 50 arbitrary non-conductive fillers with an electron microscope or an optical microscope and calculating the average value of the particle diameters of each non-conductive filler, or by performing laser diffraction particle size distribution measurement.

[0168] The ratio of the particle diameter of the above non-conductive filler to the particle diameter of the above conductive filler (non-conductive filler particle diameter / conductive filler particle diameter) is preferably 0.0002 or more, more preferably 0.002 or more, still more preferably 0.02 or more, and preferably 0.5 or less, more preferably 0.1 or less, still more preferably 0.05 or less. When the above ratio (non-conductive filler particle diameter / conductive filler particle diameter) is equal to or greater than the above lower limit and equal to or less than the above upper limit, the storage stability can be further enhanced.

[0169] In 100% by weight of the above conductive paste, the content of the above non-conductive filler is preferably 0.1% by weight or more, more preferably 0.3% by weight or more, and preferably 10% by weight or less, more preferably 5% by weight or less. When the content of the above non-conductive filler is equal to or greater than the above lower limit and equal to or less than the above upper limit, the storage stability can be further enhanced.

[0170] In 100% by weight of the above conductive paste, the total content of the above conductive filler and the above non-conductive filler is preferably 10% by weight or more, more preferably 15% by weight or more, and preferably 40% by weight or less, more preferably 30% by weight or less. When the total content of the above conductive filler and the above non-conductive filler is equal to or greater than the above lower limit and equal to or less than the above upper limit, the storage stability can be further enhanced.

[0171] <Chelating agent> The above conductive paste preferably further contains a chelating agent. The above chelating agent is preferably used in combination with the above amine curing agent. By using the above chelating agent in combination with the above amine curing agent, the surface of the above amine curing agent can be protected, and the storage stability of the conductive paste can be further enhanced.

[0172] Examples of the above chelating agent include borate esters, barbituric acid, and isophthalic acid. Only one kind of the above chelating agent may be used, or two or more kinds may be used in combination.

[0173] From the viewpoint of further enhancing the storage stability, it is preferable that the chelating agent contains a borate ester, and more preferably contains tributyl borate.

[0174] In 100% by weight of the above conductive paste, the content of the chelating agent is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, particularly preferably 0.2% by weight or more, and preferably 10% by weight or less, more preferably 5% by weight or less. When the content of the chelating agent is not less than the above lower limit and not more than the above upper limit, the storage stability can be further enhanced.

[0175] Based on 100 parts by weight of the content of the amine curing agent, the content of the chelating agent is preferably 0.5 part by weight or more, more preferably 1 part by weight or more, and preferably 100 parts by weight or less, more preferably 50 parts by weight or less. When the content of the chelating agent is not less than the above lower limit and not more than the above upper limit, the storage stability can be further enhanced.

[0176] <Other components> The above conductive paste may contain components other than the above curable compound, curing agent, conductive filler, non-conductive filler, and chelating agent. As other components, the conductive paste may contain a solvent, inorganic filler, organic filler, colorant, polymerization inhibitor, chain transfer agent, antioxidant, ultraviolet absorber, defoaming agent, leveling agent, surfactant, slip agent, anti-blocking agent, wax, masking agent, deodorant, fragrance, preservative, antibacterial agent, antistatic agent, and adhesion promoter, etc.

[0177] (RFID Inlay and Method for Manufacturing RFID Inlay) The RFID inlay according to the present invention includes a substrate having wiring on its surface, a chip having electrodes on its surface, and an adhesive portion bonding the substrate and the chip. In the RFID inlay according to the present invention, the material of the adhesive portion is the above-described conductive paste (the first conductive paste or the second conductive paste). 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.

[0178] FIG. 1 is a cross-sectional view schematically showing an RFID inlay using a conductive paste according to a first embodiment of the present invention.

[0179] The RFID inlay 81 shown in FIG. 1 includes a substrate 82 having wiring on its surface, a chip 83 having electrodes on its surface, and an adhesive portion 84 bonding 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 of a conductive paste containing the conductive filler 1. Preferably, the adhesive portion 84 is formed by curing a conductive paste containing the conductive filler 1.

[0180] The substrate 82 has wiring 82a on its surface (upper surface). The chip 83 has electrodes 83a on its surface (lower surface). The wiring 82a and the electrodes 83a are electrically connected by the conductive filler 1 in the adhesive portion 84.

[0181] The method for manufacturing an RFID inlay according to the present invention includes the following steps (1) to (3). (1) A first placement step of placing the above-described conductive paste (the first conductive paste or the second conductive paste) on the surface of a substrate having wiring on its surface. (2) A second placement step of placing a chip having electrodes on its surface on the surface opposite to the substrate side of the conductive paste. (3) An adhesion step of forming an adhesive portion bonding the substrate and the chip with the conductive paste by heating and pressurizing the conductive paste, and electrically connecting the wiring and the electrodes by the conductive filler in the adhesive portion.

[0182] In the RFID inlay and the method for manufacturing an RFID inlay according to the present invention, since a specific conductive paste is used, the adhesiveness between the substrate and the chip can be enhanced, and the electrical communication reliability can be enhanced.

[0183] In the method for manufacturing the RFID inlay, the substrate is in a long shape, and in the first placement step, the second placement step, and the bonding step, it is preferable to manufacture the RFID inlay by conveying the long substrate by a roll-to-roll method. In this case, a plurality of RFID inlays can be continuously manufactured, and the manufacturing efficiency of the RFID inlay can be further enhanced.

[0184] When the roll-to-roll method is used, the conveyance speed of the substrate is not particularly limited.

[0185] Examples of the method for disposing the conductive paste include coating by a dispenser, screen printing, and ejection by an inkjet device.

[0186] The heating temperature in the bonding step is preferably 100°C or higher, more preferably 150°C or higher, preferably 400°C or lower, more preferably 300°C or lower, and still more preferably 250°C or lower. When the heating temperature in the bonding step is equal to or higher than the lower limit and equal to or lower than the upper limit, the electrical connection between the chip and the substrate can be made good.

[0187] The pressing pressure in the bonding step is preferably 0.5 N or higher, more preferably 1 N or higher, preferably 3.5 N or lower, more preferably 3 N or lower, and still more preferably 2.5 N or lower. When the pressing pressure in the bonding step is equal to or higher than the lower limit and equal to or lower than the upper limit, the adhesiveness between the substrate and the chip can be enhanced, and the electrical communication reliability can be enhanced.

[0188] The heating and pressurization time in the above bonding step is not particularly limited. The heating and pressurization time in the above bonding step may be 2 seconds or more, may be 15 seconds or less, may be 10 seconds or less, may be 9 seconds or less, or may be 7 seconds or less.

[0189] The above RFID inlay may be cut to a predetermined size as needed and may be used after being cut. It is preferable to bond a plurality of the above chips to a plurality of the above bonding portions on a long substrate. A plurality of laminates of the above chip and the above bonding portion may be arranged on the long substrate. In the above first arranging step, it is preferable to arrange the conductive paste at a plurality of locations on the surface of the long substrate. In the above second arranging step, it is preferable to arrange the chips on the surfaces of the conductive paste arranged at a plurality of locations, opposite to the substrate side of each of them, using a plurality of chips. After bonding the above chips to the above bonding portions on the long substrate, the long substrate may be cut.

[0190] The above substrate is not particularly limited. The above substrate is preferably a circuit board. Examples of the above circuit board include a resin film, a flexible printed circuit board, a rigid-flexible circuit board, a glass substrate, and a paper substrate. The above substrate may be a resin substrate, a glass substrate, or a paper substrate.

[0191] The above substrate has wiring (antenna pattern) on its surface. Wiring (antenna pattern) is formed on the surface of the above base material. It is preferable that the above substrate has a base material and wiring (antenna pattern) arranged on the surface of the above base material.

[0192] Examples of the material of the base material include resin, glass, and paper. Examples of the resin include PET (polyethylene terephthalate), PP (polypropylene), and PVC (polyvinyl chloride). The paper may be impregnated with an epoxy resin or a phenolic resin. From the viewpoint of further enhancing the adhesiveness and from the viewpoint of manufacturing the RFID inlay by a roll-to-roll method, the material of the base material is preferably resin or paper, and more preferably PET (polyethylene terephthalate) or paper. The base material may be resin, glass, or paper.

[0193] Examples of the wiring (antenna pattern) include gold wiring, nickel wiring, tin wiring, aluminum wiring, silver wiring, SUS wiring, copper wiring, molybdenum wiring, and tungsten wiring. From the viewpoint of improving the operating sensitivity in the UHF band (860 MHz to 960 MHz), the wiring is preferably aluminum wiring.

[0194] From the viewpoint of suppressing deformation of the substrate due to heat during mounting of the chip (for example, an IC chip) and enhancing 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.

[0195] The shapes of the substrate and the base material are not particularly limited. From the viewpoint of manufacturing the RFID inlay by a roll-to-roll method, the substrate and the base material are preferably in a long shape. The lengths of the substrate and the base material are not particularly limited. The lengths of the substrate and the base material may be 1 m or more, 10 m or more, 5000 m or less, or 1000 m or less.

[0196] Examples of the chip include semiconductor chips (IC chips) and the like.

[0197] The above chip has electrodes on its surface. Examples of the above 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 enhancing the conduction reliability, the above electrode is preferably a copper electrode or a gold electrode, and more preferably a copper electrode.

[0198] The number of the above electrodes per chip is not particularly limited. The number of the above electrodes per chip may be one or more, may be four or more, may be twenty or less, or may be ten or less.

[0199] The shape of the above chip is not particularly limited. The shape of the above chip may be rectangular, triangular, or circular.

[0200] The planar area of the above chip is preferably 0.04 mm 2 or more, more preferably 0.09 mm 2 or more, still more preferably 0.16 mm 2 or more, and preferably 0.50 mm 2 or less, more preferably 0.40 mm 2 or less, still more preferably 0.30 mm 2 or less. When the planar area of the above chip is equal to or greater than the above lower limit, the conductive paste can be arranged on the fine wiring with high precision. When the planar area of the above chip is equal to or less than the above upper limit, the conduction reliability can be maintained even when the RFID inlay is left in a high-temperature and high-humidity environment for a long time. The conductive paste according to the present invention can be suitably used for adhering relatively small chips.

[0201] Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The present invention is not limited only to the following Examples.

[0202] The following materials were prepared.

[0203] Curable compound: "EP-3950S" manufactured by ADEKA Corporation (Glycidylamine type epoxy compound) "EP-3980S" manufactured by ADEKA Corporation (Glycidylamine type epoxy compound) "EXA830CRP" manufactured by DIC Corporation (Bisphenol F type epoxy compound) "EXA850CRP" manufactured by DIC Corporation (Bisphenol A type epoxy compound)

[0204] Hardener: "Karenz MT PE-1" manufactured by Resonac Corporation (Secondary thiol hardener having an ester skeleton) "TMMP" manufactured by SC Organic Chemicals Co., Ltd. (Primary thiol hardener having an ester skeleton) "Amicure PN23" manufactured by Ajinomoto Fine-Techno Co., Inc. (Amine adduct hardener, solid at 25°C) "Diethylenetriamine" manufactured by TCI (Amine hardener, liquid at 25°C) "TS-G" manufactured by Shikoku Kasei Kogyo Co., Ltd. (Primary thiol hardener having no ester skeleton) "C3TS-G" manufactured by Shikoku Kasei Kogyo Co., Ltd. (Primary thiol hardener having no ester skeleton) "PEMP" manufactured by Sakai Chemical Industry Co., Ltd. (Primary thiol hardener having an ester skeleton) "Novacure HX4922HP" manufactured by Asahi Kasei E-Materials Corporation (Microcapsule type hardener)

[0205] Conductive filler: "CN050" manufactured by Nikko Rica Co., Ltd. (Nickel particles, average particle diameter: 5 μm) "NIB-205-S" manufactured by Sekisui Chemical Co., Ltd. (Conductive particles comprising resin particles and a conductive layer disposed on the surface of the resin particles, average particle diameter: 5 μm)

[0206] Non-conductive filler: "RX-200" manufactured by Nippon Aerosil Co., Ltd. (Silica, solid at 25°C, average particle diameter: 0.012 μm) "Gelol D" manufactured by Shin Nippon Rika Co., Ltd. (Sorbitol (thixotropic agent), solid at 25°C, average particle diameter: 0.10 μm)

[0207] Chelating agent: "Tributyl borate" manufactured by TCI

[0208] Thixotropic agent (non-conductive filler): "Gelol D" manufactured by Shin Nippon Rika Co., Ltd. (sorbitol, solid at 25°C, average particle size: 0.10 μm)

[0209] Chip: IC chip (copper electrode, "UCODE9" manufactured by NXP, planar area: 0.22 mm 2 )

[0210] Substrate: PET film (long strip, resin film with aluminum wiring whose operating frequency is in the UHF band (860 MHz to 960 MHz))

[0211] (Example 1) (1) Preparation of conductive paste The materials shown in Table 1 below were blended in the blending amounts (parts by weight) shown in Table 1 below, and stirred using a planetary stirrer ("Avatori Rentaro" manufactured by Shinki Co., Ltd.) to obtain a conductive paste (anisotropic conductive paste).

[0212] (2) Preparation of RFID inlay The obtained conductive paste was applied onto a PET film by the jet dispensing method to form a conductive paste layer (adhesive layer) (first placement step). Next, an IC chip was laminated onto the surface of the conductive paste layer (adhesive layer) opposite to the substrate side such that the wiring on the PET film surface and the electrodes on the chip surface faced each other (second placement step). Thereafter, thermal compression bonding was performed under the conditions of an upper heat tool at 180 °C, a lower heat tool at 180 °C, a pressure of 2 N, and a compression bonding time of 3 seconds to cure the conductive paste layer (adhesive layer) and form an adhesive portion. Also, the wiring on the surface of the PET film and the electrodes on the surface of the chip were electrically connected by the conductive filler (conductive particles) in the adhesive portion to obtain a connection structure (adhesive step). Note that the first placement step, the second placement step, and the adhesive step were performed using "DDA40000" (roll-to-roll method) manufactured by Muhlbauer. The obtained connection structure was cut into a size of 5 cm × 1.5 cm using "DCL30000" manufactured by Muhlbauer to obtain 50 RFID inlays.

[0213] (Examples 2 to 12 and Comparative Examples 1 to 6) Conductive pastes and RFID inlays were obtained in the same manner as in Example 1, except that the compounding components and compounding amounts of the conductive paste were changed as shown in Tables 1, 3, 5, 7, and 9.

[0214] (Evaluation) (1) Differential Scanning Calorimetry A differential scanning calorimeter ("TA7000" manufactured by Hitachi High-Tech Science Corporation) was prepared, 5 mg of the obtained conductive paste was placed in a dedicated aluminum pan, and the lid was closed using a dedicated jig. This dedicated aluminum pan and an empty aluminum pan (reference) were placed in the heating unit, and heating was performed in an air atmosphere from 30 °C to 200 °C at a heating rate of 10 °C / min, and reverse heat flow and non-reverse heat flow were observed. The heat generation start temperature, heat generation peak top temperature, and heat generation end temperature were determined using the heat generation peak observed in the non-reverse heat flow as the heat generation peak of the conductive paste.

[0215] (2) Storage Stability (Pot Life) Regarding the as-prepared conductive paste, the viscosity at 25°C (η25) was measured by the method described above. Also, by the method described above, the viscosity at 25°C (ηα) after storing the conductive paste at 25°C and 50% RH for 24 hours was measured. The ratio of the viscosity after storage (ηα) to the viscosity as-prepared (η25) (viscosity after storage (ηα) / viscosity as-prepared (η25)) was determined, and the storage stability (pot life) was judged according to the following criteria.

[0216] [Criteria for Judging Storage Stability (Pot Life)] ○○: The ratio of the viscosity after storage to the viscosity as-prepared is less than 1.1 ○: The ratio of the viscosity after storage to the viscosity as-prepared is 1.1 or more and less than 1.25 ×: The ratio of the viscosity after storage to the viscosity as-prepared is 1.25 or more

[0217] (3) Curing Property of Conductive Paste (3-1) Curing Property of Conductive Paste (Low-Temperature Quick Curing Property) The conductive paste was applied on a glass plate with a thickness of 30 μm. The glass plate was placed on the surface of a hot plate from the surface opposite to the side where the paste was applied, and the temperature at which the conductive paste gelled (cured) within 3 seconds was measured. The curing property (low-temperature quick curing property) of the conductive paste was judged according to the following criteria. In addition, after heating for 3 seconds, thread pulling was confirmed using a handled needle, and when the thread did not break, it was judged that the conductive paste had cured.

[0218] [Criteria for Judging Curing Property (Low-Temperature Quick Curing Property) of Conductive Paste] A: The temperature at which the conductive paste cures is less than 160°C B: The curing temperature of the conductive paste is 160°C or more and less than 200°C C: The temperature at which the conductive paste cures is 200°C or more, or it does not cure

[0219] (3-2) Curing Property of Conductive Paste (Gel Time) A conductive paste was applied on a glass plate with a thickness of 30 μm. Onto the surface of a hot plate (set temperature: 180°C), the glass plate was placed with the surface opposite to the side where the conductive paste was applied, and the elapsed time until the conductive paste gelled was measured. The curability (gel time) of the conductive paste was judged according to the following criteria. In addition, every 5 seconds, thread pulling was checked using a patterned needle, and when the thread could no longer be broken, it was judged that the conductive paste had gelled.

[0220] [Judgment Criteria for Curability (Gel Time) of Conductive Paste] ○○○○: The elapsed time until the conductive paste gels is less than 5 seconds ○○○: The elapsed time until the conductive paste gels is 5 seconds or more and less than 10 seconds ○○: The elapsed time until the conductive paste gels is 10 seconds or more and less than 15 seconds ○: The elapsed time until the conductive paste gels is 15 seconds or more and less than 30 seconds ×: The elapsed time until the conductive paste gels is 30 seconds or more

[0221] (4) Adhesion (Die Shear Strength) Regarding the obtained RFID inlay, using a die shear tester ("DAGE4000PLUS" manufactured by Nordson Corporation), under the conditions of a tool height of 30 μm and a speed of 100 μm / second, the chip was peeled from the substrate, and the die shear strength at 25°C was evaluated. The adhesion was judged according to the following criteria.

[0222] [Judgment Criteria for Adhesion] ○○: The die shear strength is 7.0 N or more ○: The die shear strength is 4.0 N or more and less than 7.0 N ×: The die shear strength is less than 4.0 N

[0223] (5) Tackiness of the Cured Product The prepared conductive paste was filled into a mold made of PTFE, and the conductive paste filled in the mold was heated in an oven at 180 °C for 300 seconds to obtain a strip-shaped cured product of 5 mm × 40 mm × 2 mm. The obtained cured product was left at room temperature for 12 hours or more, and the cured product was cooled. At 25 °C, when the tip of a handled needle touched one end of the cured product, it was observed whether the cured product lifted up. The tackiness of the cured product was determined according to the following criteria.

[0224] [Criteria for judging the tackiness of the cured product] ○○: The cured product does not lift up ○: While the other end where the handled needle is not touching remains grounded, one end side of the cured product lifts up ×: The entire cured product lifts up

[0225] (6) Conductive communication reliability After leaving 50 obtained RFID inlays at 85 °C and 85% RH (under high temperature and high humidity environment) for 168 hours, they were placed in a dark box that blocks external radio waves, and the peak sensitivity at 25 °C in the UHF band (860 MHz to 960 MHz) was measured using a frequency reader ("Tagformance Pro" manufactured by Voyantic). The conductive communication reliability was determined according to the following criteria.

[0226] [Criteria for judging conductive communication reliability] ○○: The peak sensitivity of all RFID inlays is less than -18 dBm ○: Does not fall under either ○○ or × ×: The peak sensitivity of at least one RFID inlay is -16.4 dBm or more

[0227] The composition of the conductive paste and the results are shown in Tables 1 to 10 below.

[0228]

Table 1

[0229]

Table 2

[0230]

Table 3

[0231]

Table 4

[0232]

Table 5

[0233]

Table 6

[0234]

Table 7

[0235]

Table 8

[0236]

Table 9

[0237]

Table 10

Explanation of Symbols

[0238] 1…Conductive filler 81…RFID inlay 82…Substrate having wiring on the surface 82a…Wiring 83…Chip having electrodes on the surface 83a…Electrode 84…Adhesive part

Claims

1. A conductive paste including a curable compound, a curing agent, and a conductive filler, the curable compound comprises a bisphenol A type epoxy compound, a bisphenol F type epoxy compound, or a glycidylamine type epoxy compound; A conductive paste, the heat generation starting temperature of which is 50° C. or more and 80° C. or less when the conductive paste is heated from 30° C. to 200° C. at a temperature increase rate of 10° C. / min and subjected to differential scanning calorimetry.

2. A conductive paste including a curable compound, a curing agent, and a conductive filler, the curable compound comprises a bisphenol A type epoxy compound, a bisphenol F type epoxy compound, or a glycidylamine type epoxy compound; The curing agent includes a secondary thiol curing agent or a primary thiol curing agent having no ester skeleton, The conductive paste, wherein the conductive filler is a conductive particle having a resin particle and a conductive layer disposed on a surface of the resin particle, or a metal particle having a melting point exceeding 450°C.

3. The conductive paste according to claim 1 , wherein the curable compound comprises a glycidyl amine type epoxy compound.

4. The conductive paste according to claim 1 , wherein the curing agent comprises a thiol curing agent having two or more thiol groups.

5. The conductive paste according to claim 1 , wherein the curing agent comprises a thiol curing agent having a structure represented by the following formula (1): 【Chemistry 1】 In the formula (1), R1, R2, R3 and R4 each represent an alkylene group having 1 to 5 carbon atoms.

6. The curing agent includes a secondary thiol curing agent or a primary thiol curing agent having no ester skeleton, 3. The conductive paste according to claim 1, wherein the total content of the secondary thiol curing agent and the primary thiol curing agent not having an ester skeleton is 5% by weight or more and 50% by weight or less in 100% by weight of the conductive paste.

7. The conductive paste according to claim 1 or 2, wherein the curing agent comprises a secondary thiol curing agent.

8. 3. The conductive paste according to claim 1, wherein when the conductive paste is heated from 30° C. to 200° C. at a temperature increase rate of 10° C. / min and subjected to differential scanning calorimetry, the heat generation end temperature is 85° C. or higher and 180° C. or lower.

9. 3. The conductive paste according to claim 1, wherein when the conductive paste is heated from 30° C. to 200° C. at a temperature increase rate of 10° C. / min and subjected to differential scanning calorimetry, the absolute value of the difference between the heat generation start temperature and the heat generation end temperature is 5° C. or more and 100° C. or less.

10. The conductive paste according to claim 1 , wherein the curing agent comprises a microencapsulated curing agent.

11. The conductive paste according to claim 10 , wherein the content of the microcapsule-type hardener is 5% by weight or more and 40% by weight or less in 100% by weight of the conductive paste.

12. The conductive paste according to claim 1 or 2, wherein the conductive filler has a particle size of 10 μm or less.

13. 3. The conductive paste according to claim 1, wherein the conductive filler has a content of 0.1% by weight or more and 50% by weight or less in 100% by weight of the conductive paste.

14. The conductive paste according to claim 1 or 2, wherein the curing agent comprises an amine curing agent that is solid at 25°C.

15. The conductive paste according to claim 1 or 2, further comprising a chelating agent.

16. The conductive paste of claim 15 , wherein the chelating agent comprises a borate ester.

17. The conductive paste according to claim 1 or 2, further comprising a non-conductive filler.

18. 18. The conductive paste according to claim 17, wherein a ratio of a particle size of the non-conductive filler to a particle size of the conductive filler is 0.5 or less.

19. The conductive paste according to claim 1 or 2, used for obtaining an RFID inlay.

20. The semiconductor device includes a substrate having wiring on a surface thereof, a chip having electrodes on a surface thereof, and an adhesive portion that adheres the substrate and the chip to each other; The material of the adhesive portion is the conductive paste according to claim 1 or 2, An RFID inlay, wherein the wiring and the electrodes are electrically connected by the conductive filler in the adhesive portion.

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

22. The substrate is elongated, The method for manufacturing an RFID inlay according to claim 21 , wherein the long substrate is transported by a roll-to-roll method in the first arrangement step, the second arrangement step, and the bonding step to manufacture the RFID inlay.

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