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

Abstract

This invention provides a conductive paste that maintains high conductivity reliability even when moisture penetrates into the connecting structure. The conductive paste of this invention comprises a curing compound, a curing agent, and a plurality of conductive fillers. The curing compound comprises a polymeric monomer having an alicyclic backbone. In a test where the cured conductive paste is immersed in water at 121°C, 100% RH, and 2 atm for 2 hours, the water absorption rate of the cured paste is less than 2.0%.

Description

Technical Field

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

[0002] RFID (Radio Frequency Identification) inlays, which enable contactless data transmission and reception, are widely used in contactless RFID tags and cards. In particular, RFID inlays operating in the UHF (Ultra High Frequency) band (860 MHz to 960 MHz) have attracted attention due to their longer communication range. These inlays are used for a variety of items and purposes, including commuter tickets, inventory management, circulation management, and history management.

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

[0004] Patent Document 1 below discloses an adhesive for electronic components. The adhesive is an acrylic adhesive composition comprising a free radical initiator with a 10-hour half-life temperature of 80°C or less, an oligomer containing a vinylidene group, and at least one diluent. The adhesive cures rapidly at low temperatures and has a shelf life of at least 24 hours at room temperature.

[0005] Patent Document 2 below discloses a conductive adhesive comprising a polymerizable acrylic compound, an organic peroxide, and solder particles, wherein the one-minute half-life temperature of the organic peroxide is lower than the solidus temperature of the solder particles. [Prior Art Literature] [Patent Document]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-144018 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-124330 Summary of the Invention

[0007] [Problems to be solved by the invention]

[0008] With the widespread use of RFID inlays, moisture from rain or drinking water can adhere to electronic components such as contactless RFID tags and cards. Furthermore, condensation can form on electronic components when stored at low temperatures. Therefore, there is a desire to develop a conductive paste that can maintain conductivity even when moisture penetrates electronic components (connection structures).

[0009] The present invention aims to provide a conductive paste that can maintain high conductivity reliability even when moisture penetrates the connection structure. Furthermore, the present invention aims to provide an RFID inlay using the conductive paste and a method for manufacturing the RFID inlay. [Technical means to solve the problem]

[0010] This specification discloses the following conductive paste, RFID inlay, and method for manufacturing the RFID inlay.

[0011] Item 1. A conductive paste comprising a curable compound, a curing agent, and a plurality of conductive fillers, wherein the curable compound comprises a polymerizable monomer having an alicyclic skeleton, and wherein the cured conductive paste exhibits a water absorption of 2.0% or less when immersed in water at 121°C, 100% RH, and 2 atm for 2 hours.

[0012] Water absorption of the cured product (%) = (weight of the cured product after the test - weight of the cured product before the test) × 100 / weight of the cured product before the test

[0013] Item 2. The conductive paste according to Item 1, wherein the storage modulus of the cured product before the test is 0.8 GPa or greater, and the storage modulus of the cured product after the test is 0.5 GPa or greater.

[0014] Item 3. The conductive paste according to Item 1 or 2, wherein a ratio of the storage modulus of the cured product after the test to the storage modulus of the cured product before the test is 0.5 or greater.

[0015] Item 4. The conductive paste according to any one of Items 1 to 3, wherein the polymerizable monomer having an alicyclic skeleton has a (meth)acryloyl group.

[0016] Item 5. The conductive paste according to any one of items 1 to 4, wherein the polymerizable monomer having an alicyclic skeleton is tricyclodecane dimethanol di(meth)acrylate or isobutyl(meth)acrylate.

[0017] Item 6. The conductive paste according to any one of Items 1 to 5, wherein the content of the polymerizable monomer having an alicyclic skeleton in 100 wt % of the curable compound is 10 wt % to 50 wt %.

[0018] Item 7. The conductive paste according to any one of Items 1 to 6, wherein the conductive filler comprises nickel.

[0019] Item 8. The conductive paste as described in any one of Items 1 to 7, which is used to obtain an RFID inlay.

[0020] Item 9. An RFID inlay comprising a substrate having wiring on its surface, a chip having electrodes on its surface, and a bonding portion for bonding the substrate and the chip, wherein the material of the bonding portion is a conductive paste as described in any one of items 1 to 8, and the wiring and the electrodes are electrically connected via the conductive filler in the bonding portion.

[0021] Item 10. A method for manufacturing an RFID inlay, comprising: a first configuration step of configuring a conductive paste as described in any one of items 1 to 8 on a surface of a substrate having wiring on its surface; a second configuration step of configuring a chip having electrodes on its surface on the surface of the conductive paste opposite to the substrate; and a subsequent step of heating and pressurizing the conductive paste to form a bonding portion that bonds the substrate and the chip with the conductive paste, and electrically connecting the wiring and the electrodes using the conductive filler in the bonding portion.

[0022] Item 11. A method for manufacturing an RFID inlay as described in Item 10, wherein the substrate is in the form of an elongated strip, and in the first configuration step, the second configuration step, and the subsequent step, the RFID inlay is manufactured by conveying the elongated substrate in a roll-to-roll manner. [Effects of the Invention]

[0023] The conductive paste of the present invention comprises a curable compound, a curing agent, and a plurality of conductive fillers. In the conductive paste of the present invention, the curable compound comprises a polymerizable monomer having an alicyclic skeleton. When the cured conductive paste of the present invention was immersed in water for two hours at 121°C, 100% RH, and 2 atm, the water absorption rate of the cured conductive paste was less than 2.0%. Due to the aforementioned composition, the conductive paste of the present invention can maintain high conductivity reliability even when moisture penetrates the connection structure. Simple diagram description

[0024] FIG1 is a cross-sectional view schematically showing an RFID inlay using the conductive paste according to the first embodiment of the present invention. Implementation Method

[0025] Hereinafter, the details of the present invention will be described.

[0026] (Conductive paste) The conductive paste of the present invention comprises a curable compound, a curing agent, and a plurality of conductive fillers. In the conductive paste of the present invention, the curable compound comprises a polymerizable monomer having an alicyclic skeleton. In a test in which the cured conductive paste of the present invention was immersed in water for 2 hours at 121°C, 100% RH, and 2 atm, the water absorption of the cured product was less than 2.0%.

[0027] Water absorption rate of the cured product (%) = (weight of the cured product after the test - weight of the cured product before the test) × 100 / weight of the cured product before the test

[0028] The conductive paste of the present invention has the above-mentioned structure, so it can maintain high conduction reliability even when moisture penetrates into the connection structure (electronic components).

[0029] When the cured conductive paste is immersed in water for 2 hours at 121°C, 100% RH, and 2 atm, the water absorption of the cured material is preferably 1.8% or less, more preferably 1.7% or less, even more preferably 1.5% or less, particularly preferably 1.0% or less, and most preferably 0.5% or less. If the water absorption of the cured material is below the upper limit, high conductivity reliability can be maintained even when moisture penetrates the connection structure (electronic components). There is no specific lower limit for the water absorption of the cured material. The water absorption of the cured material may be 0%, 0% or greater, or 0.1% or greater.

[0030] The water absorption rate of the cured product can be measured, for example, as follows: The conductive paste is heated at 130°C for 10 minutes to obtain a cured product (pre-test cured product). The cured product is then immersed in water at 121°C, 100% RH, and 2 atm for 2 hours to obtain a post-test cured product. The weight of the cured product before and after the test is measured to calculate the water absorption rate of the cured product.

[0031] Water absorption rate of the cured product (%) = (weight of the cured product after the test - weight of the cured product before the test) × 100 / weight of the cured product before the test

[0032] Methods for adjusting the water absorption of the cured product include the following methods: A method for using the following preferred polymerizable monomers as the polymerizable monomer having an alicyclic skeleton; and a method for adjusting the content of the polymerizable monomer having an alicyclic skeleton (particularly, a polymerizable monomer having an alicyclic skeleton and no polar group).

[0033] The storage modulus of the cured product before the test is preferably 0.8 GPa or greater, more preferably 1.0 GPa or greater, and even more preferably 1.2 GPa or greater, and is preferably 3.5 GPa or less, more preferably 3.2 GPa or less, and even more preferably 3.0 GPa or less. If the storage modulus of the cured product before the test is above the lower limit and below the upper limit, adhesion and conduction reliability can be further improved.

[0034] The storage modulus of the cured product after the above test is preferably 0.3 GPa or greater, more preferably 0.4 GPa or greater, even more preferably 0.5 GPa or greater, even more preferably 0.8 GPa or greater, and particularly preferably 1.0 GPa or greater, and is preferably 3.0 GPa or less, more preferably 2.8 GPa or less, and even more preferably 2.5 GPa or less. If the storage modulus of the cured product after the above test is above the lower limit and below the upper limit, conductive reliability can be improved and high adhesion can be maintained even when moisture penetrates the connection structure.

[0035] The ratio of the storage modulus of the cured product after the test to the storage modulus of the cured product before the test (storage modulus of the cured product after the test / storage modulus of the cured product before the test) is preferably 0.3 or greater, more preferably 0.5 or greater, further preferably 0.6 or greater, and particularly preferably 0.7 or greater. If the ratio (storage modulus of the cured product after the test / storage modulus of the cured product before the test) is above the lower limit, high conductivity reliability can be maintained even when moisture penetrates the connection structure (electronic component). The upper limit of the ratio (storage modulus of the cured product after the test / storage modulus of the cured product before the test) is not particularly limited. The ratio (storage modulus of the cured product after the test / storage modulus of the cured product before the test) may be 1.0 or less, 0.9 or less, or 0.85 or less.

[0036] The storage modulus of the cured material before and after the test can be measured, for example, as follows. The cured material before and after the test is cut into pieces measuring 10 mm in length, 1 mm to 10 mm in width, and 15 mm to 50 mm in height to prepare test samples. For each test sample, a dynamic viscoelasticity tester (e.g., the "RSA3" manufactured by TA Instruments) is used to measure the storage modulus of the cured material before and after the test under the conditions of a frequency of 10 Hz, a strain of 0.1%, a temperature range of 20°C to 180°C, and a heating rate of 10°C / minute.

[0037] The conductive paste of the present invention is in a paste form at 25° C. The conductive paste is sprayed and used at, for example, 20° C. to 50° C. The conductive paste of the present invention is preferably sprayed and used using a jet dispenser.

[0038] The conductive paste has good adhesion and is suitable for use as an adhesive. The conductive paste is particularly suitable for bonding substrates and chips.

[0039] From the perspective of further improving conductivity reliability, the conductive paste is preferably an anisotropic conductive paste. The conductive paste is suitable for electrically connecting electrodes. It is suitable for forming a connected structure. It is suitable for forming electronic components. The conductive paste is particularly suitable for forming RFID inlays (use of the conductive paste for forming RFID inlays). The conductive paste is suitable for bonding and connecting a wafer having electrodes on its surface to a substrate having wiring (antenna pattern) on its surface (use of the conductive paste for bonding and connecting a wafer having electrodes on its surface to a substrate having wiring (antenna pattern) on its surface).

[0040] The conductive paste is preferably applied to a substrate having a surface tension of 30 mN / m to 50 mN / m (application of the conductive paste on a substrate having a surface tension of 30 mN / m to 50 mN / m). The conductive paste is preferably used to bond wafers having a surface area of ​​0.50 mm² or less (application of the conductive paste to bond wafers having a surface area of ​​0.50 mm² or less).

[0041] The conductive paste is preferably thermosetting. The conductive paste is preferably a thermosetting conductive paste, and more preferably a thermosetting anisotropic conductive paste.

[0042] The following describes the components of the conductive paste.

[0043] In this specification, "(meth)acrylate" refers to both acrylate and methacrylate. "(meth)acrylic acid" refers to both acrylic acid and methacrylic acid. "(Meth)acryloyl" refers to both acryl and methacryloyl.

[0044] <Curing Compound> The curable compound includes a polymerizable monomer having an alicyclic skeleton. Due to the aforementioned composition, the conductive paste can have a low water absorption rate. Consequently, even when moisture penetrates into the connection structure (electronic components), high conductivity reliability can be maintained.

[0045] The polymerizable monomer having an alicyclic backbone is preferably a (meth)acrylic compound. The polymerizable monomer having an alicyclic backbone is preferably a (meth)acryloyl group. The polymerizable monomer having an alicyclic backbone is preferably a (meth)acryloyl group. The polymerizable functional group in the polymerizable monomer having an alicyclic backbone is preferably a (meth)acryloyl group.

[0046] The polymerizable monomer having an alicyclic skeleton preferably does not have a polar group. The polymerizable monomer having an alicyclic skeleton preferably includes a polymerizable monomer having an alicyclic skeleton and no polar group. Examples of the polar group include hydroxyl groups, amino groups, and carboxyl groups. In this case, the water absorption rate of the cured product can be reduced, resulting in high conductivity reliability even when moisture penetrates the connection structure (electronic components).

[0047] The polymerizable monomer having an alicyclic skeleton may be a monofunctional (meth)acrylate or a polyfunctional (meth)acrylate. The polymerizable monomer having an alicyclic skeleton may have one (meth)acryloyl group, two (meth)acryloyl groups, two or more (meth)acryloyl groups, or ten or fewer (meth)acryloyl groups. To further improve adhesion, conduction reliability, and discharge properties, the polymerizable monomer having an alicyclic skeleton is preferably a monofunctional (meth)acrylate, preferably one having a single (meth)acryloyl group.

[0048] Examples of the polymerizable monomer having an alicyclic skeleton include cyclohexyl (meth)acrylate, dimethyloltricyclodecane di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, isothioyl (meth)acrylate, 4-tert-butylcyclohexanol, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, pentamethylpiperidinyl (meth)acrylate, tetramethylpiperidinyl (meth)acrylate, acrylopyrin, and 3,3,5-trimethylcyclohexyl (meth)acrylate. These polymerizable monomers having an alicyclic skeleton may be used alone or in combination of two or more.

[0049] To maintain high conductivity reliability even when moisture penetrates the connection structure (electronic components), the polymerizable monomer having an alicyclic skeleton is preferably tricyclodecane dimethanol di(meth)acrylate or isoindole (meth)acrylate. To maintain high conductivity reliability even when moisture penetrates the connection structure (electronic components), the alicyclic skeleton is preferably tricyclodecane dimethylol di(meth)acrylate or isoindole (meth)acrylate.

[0050] The molecular weight of the polymerizable monomer having an alicyclic skeleton is preferably 50 or greater, more preferably 100 or greater, even more preferably 150 or greater, and particularly preferably 200 or greater, and is preferably 1000 or less, more preferably less than 1000, even more preferably 900 or less, particularly preferably 800 or less, and most preferably 700 or less. If the molecular weight of the polymerizable monomer having an alicyclic skeleton is within the above range, the viscosity of the conductive paste can be adjusted to an appropriate range, further improving adhesion and conduction reliability.

[0051] When the molecular weight of the polymerizable monomer having an alicyclic skeleton is a molecular weight that can be calculated from the structural formula, if the structural formula of the polymerizable monomer having an alicyclic skeleton can be specified. Furthermore, when the structural formula of the polymerizable monomer having an alicyclic skeleton can be specified, the molecular weight refers to the weight-average molecular weight. The weight-average molecular weight is the polystyrene-equivalent weight-average molecular weight measured by gel permeation chromatography (GPC). Since the molecular weight of the polymerizable monomer having an alicyclic skeleton is relatively small, the structural formula can usually be specified. The weight-average molecular weight can be measured using the following measurement apparatus and conditions.

[0052] Measurement equipment: "Waters GPC System (Waters 2690 + Waters 2414 (RI))" manufactured by Nihon Waters Column: Shodex GPC LF-G × 1, Shodex GPC LF-804 × 2 Mobile phase: THF 1.0 mL / min Sample concentration: 5 mg / mL Detector: Refractive Index Detector (RID) Standard material: Polystyrene (manufactured by TOSOH, weight average molecular weight: 620~590000)

[0053] The curable compound may also include a curable compound other than the aforementioned polymerizable monomer having an alicyclic skeleton. The curable compound other than the aforementioned polymerizable monomer having an alicyclic skeleton may be a thermosetting compound or a photocurable compound. The curable compound other than the aforementioned polymerizable monomer having an alicyclic skeleton 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, phenolic compounds, amino compounds, unsaturated polyester compounds, polyurethane compounds, silicone compounds, and polyimide compounds. The curable compound other than the aforementioned polymerizable monomer having an alicyclic skeleton may be used alone or in combination of two or more.

[0054] To further improve adhesion and conduction reliability, and to achieve good ejection properties, the curable compound other than the aforementioned polymerizable monomer having an alicyclic skeleton preferably comprises an epoxy compound or a (meth)acrylic compound, and more preferably comprises a (meth)acrylic compound. To further improve adhesion, the curable compound other than the aforementioned polymerizable monomer having an alicyclic skeleton more preferably comprises a compound having a (meth)acryloyl group ((meth)acrylate).

[0055] To maintain high conductivity reliability even when moisture penetrates the connection structure (electronic components), curable compounds other than the aforementioned polymerizable monomers having an alicyclic skeleton preferably have two or more (meth)acryl groups. Curable compounds other than the aforementioned polymerizable monomers having an alicyclic skeleton are preferably multifunctional (meth)acrylates. These multifunctional (meth)acrylates may be difunctional, trifunctional, or tetrafunctional or higher. Curable compounds other than the aforementioned polymerizable monomers having an alicyclic skeleton may have two (meth)acryl groups, two or more, three or more, four or more, or ten or fewer.

[0056] Examples of the polyfunctional (meth)acrylate include 1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol (meth)acrylate, 1,9-nonanediol di(meth)acrylate, polyethylene glycol (200) di(meth)acrylate, tetraethylene glycol di(meth)acrylate, triethylene glycol (meth)acrylate, tripropylene glycol di(meth)acrylate, polyethylene glycol (400) di(meth)acrylate, dipropylene glycol di(meth)acrylate, alkoxylated hexanediol di(meth)acrylate, and dodecane. glycol di(meth)acrylate, polyethylene glycol (600) di(meth)acrylate, polypropylene glycol (700) (meth)acrylate, propoxylated (2) neopentyl glycol di(meth)acrylate, alkoxylated neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tris-(2-hydroxyethyl)isocyanurate tri(meth)acrylate, pentaerythritol tri(meth)acrylate, ethoxylated (3) trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, di-trimethylolpropane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate, etc.

[0057] From the viewpoint of further improving adhesion and conduction reliability and achieving good ejection properties, the curable compound other than the above-mentioned polymerizable monomer having an alicyclic skeleton preferably includes urethane (meth)acrylate.

[0058] The molecular weight of the urethane (meth)acrylate is preferably 1,000 or greater, more preferably 1,500 or greater, even more preferably 2,000 or greater, even more preferably 3,000 or greater, and particularly preferably 5,000 or greater, and is preferably 30,000 or less, more preferably 25,000 or less, even more preferably 20,000 or less, and particularly preferably 18,000 or less. When the molecular weight of the urethane (meth)acrylate is above the lower limit and below the upper limit, adhesion and conduction reliability can be further improved.

[0059] Regarding the molecular weight of the urethane (meth)acrylate, if the structural formula of the urethane (meth)acrylate can be specified, it refers to the molecular weight that can be calculated from the structural formula. If the structural formula of the urethane (meth)acrylate cannot be specified, the molecular weight refers to the weight-average molecular weight. The weight-average molecular weight is the polystyrene-converted weight-average molecular weight measured by gel permeation chromatography (GPC). The molecular weight of the urethane (meth)acrylate is preferably the polystyrene-converted weight-average molecular weight measured by gel permeation chromatography (GPC). The weight-average molecular weight can be measured using the following measurement apparatus and conditions.

[0060] Measurement equipment: "Waters GPC System (Waters 2690 + Waters 2414 (RI))" manufactured by Nihon Waters Column: Shodex GPC LF-G × 1, Shodex GPC LF-804 × 2 Mobile phase: THF 1.0 mL / min Sample concentration: 5 mg / mL Detector: Refractive Index Detector (RID) Standard material: Polystyrene (manufactured by TOSOH, weight average molecular weight: 620~590000)

[0061] The content of the curable compound in 100% by weight of the conductive paste is preferably 30% by weight or more, more preferably 50% by weight or more, and preferably 90% by weight or less, more preferably 85% by weight or less, and even more preferably 80% by weight or less. When the content of the curable compound is above the lower limit and below the upper limit, adhesion and conduction reliability can be further improved.

[0062] The content of the polymerizable monomer having an alicyclic skeleton in 100% by weight of the conductive paste is preferably 5% by weight or more, more preferably 15% by weight or more, and preferably 50% by weight or less, more preferably 45% by weight or less, further preferably 40% by weight or less, and particularly preferably 35% by weight or less. If the content of the polymerizable monomer having an alicyclic skeleton is above the lower limit and below the upper limit, high conductivity reliability can be maintained even when moisture penetrates the connection structure (electronic component). When two or more polymerizable monomers having an alicyclic skeleton are used in combination, the content of the polymerizable monomers having an alicyclic skeleton represents the total content of the polymerizable monomers having an alicyclic skeleton.

[0063] The content of the polymerizable monomer having an alicyclic skeleton in 100% by weight of the curable compound is preferably 5% by weight or more, more preferably 10% by weight or more, and even more preferably 20% by weight or more, and is preferably 50% by weight or less, more preferably 40% by weight or less, and even more preferably 30% by weight or less. If the content of the polymerizable monomer having an alicyclic skeleton is above the lower limit and below the upper limit, high conductivity reliability can be maintained even when moisture penetrates the connection structure (electronic component). When two or more polymerizable monomers having an alicyclic skeleton are used in combination, the content of the polymerizable monomers having an alicyclic skeleton represents the total content of the polymerizable monomers having an alicyclic skeleton.

[0064] The urethane (meth)acrylate content in 100% by weight of the curable compound is preferably 15% by weight or greater, more preferably 20% by weight or greater, and preferably 50% by weight or less, more preferably 45% by weight or less. When the urethane (meth)acrylate content is above the lower limit and below the upper limit, adhesion and conduction reliability can be improved.

[0065] The combined content of the polymerizable monomer having an alicyclic skeleton and the urethane (meth)acrylate in 100% by weight of the curable compound is preferably 20% by weight or greater, more preferably 40% by weight or greater, and preferably 95% by weight or less, more preferably 90% by weight or less. If the combined content of the polymerizable monomer having an alicyclic skeleton and the urethane (meth)acrylate is above the lower limit and below the upper limit, high conductivity reliability can be maintained even when moisture penetrates the connection structure (electronic component).

[0066] The content of the polymerizable monomer having an alicyclic skeleton, based on a total of 100% by weight of the polymerizable monomer having an alicyclic skeleton and the urethane (meth)acrylate, is preferably 15% by weight or greater, more preferably 20% by weight or greater, and preferably 80% by weight or less, more preferably 70% by weight or less. If the content of the polymerizable monomer having an alicyclic skeleton is above the lower limit and below the upper limit, high conductivity reliability can be maintained even when moisture penetrates the connection structure (electronic component).

[0067] The content of the polymerizable monomer having an alicyclic skeleton and no polar group in 100% by weight of the polymerizable monomer having an alicyclic skeleton is preferably 50% by weight or less, more preferably 45% by weight or less, and even more preferably 40% by weight or less. If the content of the polymerizable monomer having an alicyclic skeleton and no polar group is below the upper limit, the water absorption of the cured product can be low, thereby maintaining high conductivity reliability even when moisture penetrates into the connected structure (electronic component). There is no particular lower limit for the content of the polymerizable monomer having an alicyclic skeleton and no polar group in 100% by weight of the polymerizable monomer having an alicyclic skeleton. The content of the polymerizable monomer having an alicyclic skeleton and no polar group in 100% by weight of the polymerizable monomer having an alicyclic skeleton can be 5% by weight or more, or 10% by weight or more.

[0068] <Conductive filler> The conductive paste contains a plurality of conductive fillers. The conductive fillers are not particularly limited. They may be conductive particles or carbon fibers. In this specification, "containing a plurality of conductive fillers" means the paste contains two or more conductive fillers. The conductive fillers may be used alone or in combination.

[0069] The shape of the conductive filler is not particularly limited. The conductive filler may be spherical, or may be a shape other than a spherical shape, or may be flat.

[0070] The conductive filler is preferably conductive particles. The conductive particles may be solder particles or metal particles. The metal particles may also be metal powder. The conductive particles may include substrate particles and a conductive portion disposed on the surface of the substrate particles. To further improve conduction reliability, the conductive particles preferably include substrate particles and a conductive portion disposed on the surface of the substrate particles.

[0071] The particle size of the conductive particles is preferably 0.1 μm or larger, more preferably 1 μm or larger, and even more preferably 3 μm or larger, and is preferably 100 μm or smaller, more preferably 30 μm or smaller, and even more preferably 10 μm or smaller. When the particle size of the conductive particles is greater than the lower limit and less than the upper limit, the conduction reliability can be further improved.

[0072] The particle size of the conductive particles is preferably an average particle size, more preferably a number average particle size. The average particle size of the conductive particles can be determined, for example, by observing 50 random conductive particles using an electron microscope or an optical microscope and calculating the average particle size of each conductive particle, or by performing laser diffraction particle size distribution measurement.

[0073] When measuring the particle size of the conductive particles by observing 50 random conductive particles using an electron microscope or an optical microscope, the measurement can be performed, for example, as follows. Conductive particles are added to "Technovit 4000" manufactured by Kulzer to a concentration of 30% by weight and dispersed to prepare an embedding resin for conductive particle inspection. A cross-section of the conductive particles is cut using an ion milling device ("IM4000" manufactured by Hitachi High-Technologies) so as to pass near the center of the conductive particles dispersed in the embedding resin for conductive particle inspection. Subsequently, 50 randomly selected conductive particles are observed using a field emission scanning electron microscope (FE-SEM) at a magnification of 25,000x. The equivalent circular diameter of each conductive particle is measured, and the arithmetic average of these values ​​is used as the particle size of the conductive particles.

[0074] The coefficient of variation (CV) of the particle size of the conductive particles is preferably 10% or less, more preferably 5% or less. If the coefficient of variation of the particle size of the conductive particles is below the upper limit, the conduction reliability can be further improved. There is no particular lower limit for the coefficient of variation (CV) of the particle size of the conductive particles. The coefficient of variation (CV) of the particle size of the conductive particles can be 0% or greater, or 1% or greater.

[0075] The above-mentioned coefficient of variation (CV value) can be measured as follows.

[0076] CV value (%) = (ρ / Dn) × 100 ρ: Standard deviation of conductive particle size Dn: Average particle size of conductive particles

[0077] The content of the conductive filler in 100% by weight of the conductive paste is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, and preferably 80% by weight or less, more preferably 60% by weight or less, further preferably 40% by weight or less, particularly preferably 20% by weight or less, and most preferably 10% by weight or less. When the content of the conductive filler is above the lower limit and below the upper limit, conduction reliability can be further improved.

[0078] The conductive filler content is preferably 2 parts by weight or greater, more preferably 3 parts by weight or greater, even more preferably 5 parts by weight or greater, and particularly preferably 7 parts by weight or greater, per 100 parts by weight of the curable compound in the conductive paste. The conductive filler content is preferably 35 parts by weight or less, more preferably 30 parts by weight or less, even more preferably 25 parts by weight or less, and particularly preferably 20 parts by weight or less, per 100 parts by weight of the curable compound in the conductive paste. When the conductive filler content in the conductive paste is above the lower limit and below the upper limit, conduction reliability can be further improved.

[0079] The conductive filler preferably comprises a metal. Examples of the metal include gold, silver, copper, platinum, palladium, zinc, lead, aluminum, cobalt, indium, ruthenium, nickel, chromium, titanium, antimony, bismuth, germanium, and cadmium, as well as alloys thereof. Alternatively, tin-doped indium oxide (ITO) may be used as the metal. The metals may be used singly or in combination.

[0080] To further reduce the connection resistance between electrodes, the conductive filler preferably comprises a tin-containing alloy, nickel, palladium, ruthenium, silver, copper, or gold, more preferably nickel or palladium. To improve the corrosion resistance of the conductive filler and maintain high conduction reliability, the conductive filler preferably comprises nickel or gold, more preferably nickel. To further improve the corrosion resistance of the conductive filler and maintain high conduction reliability, the conductive filler preferably comprises nickel on its outer surface.

[0081] When the conductive particles are metal particles, examples of the metal material of the metal particles include silver, copper, nickel, silicon, gold, titanium, and alloys such as solder. To further improve conduction reliability, the metal particles are preferably made of nickel or a nickel alloy, and more preferably, nickel or a nickel alloy. To further improve conduction reliability, the outer surface of the metal particles is preferably made of nickel or a nickel alloy.

[0082] Hereinafter, the conductive particles including the substrate particles and the conductive portion arranged on the surface of the substrate particles will be described in detail.

[0083] (Base particles) Examples of the substrate particles include resin particles, inorganic particles other than metal particles, organic-inorganic hybrid particles, and metal particles. The substrate particles are preferably substrate particles other than metal particles, more preferably resin particles, inorganic particles other than metal particles, or organic-inorganic hybrid particles. The substrate particles may also be core-shell particles comprising a core and a shell disposed on the surface of the core. The core may be an organic core, and the shell may be an inorganic shell.

[0084] The substrate particles are preferably resin particles or organic-inorganic hybrid particles. Alternatively, they may be resin particles or organic-inorganic hybrid particles. By using these preferred substrate particles, the effects of the present invention can be more effectively exerted.

[0085] Various resins can be suitably used as the material for the resin particles. Examples of the material for the resin particles include polyolefin resins such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyisobutylene, and polybutadiene; acrylic resins such as polymethyl methacrylate and polymethyl acrylate; polyalkylene terephthalate, polycarbonate, polyamide, phenol formaldehyde resin, melamine formaldehyde resin, benzoguanamine formaldehyde resin, urea formaldehyde resin, phenolic resin, melamine resin, benzoguanamine resin, urea resin, epoxy resin, unsaturated polyester resin, saturated polyester resin, polysulfone, polyphenylene ether, polyacetal, polyimide, polyamide imide, polyetheretherketone, polyethersulfone, divinylbenzene polymers, and polymers obtained by polymerizing one or more polymerizable monomers having ethylenically unsaturated groups. The divinylbenzene polymer may also be a divinylbenzene copolymer. Examples of the divinylbenzene-based copolymer include divinylbenzene-styrene copolymers and divinylbenzene-(meth)acrylate copolymers.

[0086] Since it is possible to design and synthesize resin particles having arbitrary compression characteristics suitable for the conductive paste and the hardness of the resin particles can be easily controlled within an appropriate range, the material of the above-mentioned resin particles is preferably a polymer formed by polymerizing one or more polymerizable monomers having multiple ethylenically unsaturated groups.

[0087] When the resin particles are obtained by polymerizing a polymerizable monomer having an ethylenically unsaturated group, examples of the polymerizable monomer having an ethylenically unsaturated group include non-crosslinkable monomers and crosslinkable monomers.

[0088] Examples of the non-crosslinking monomer include: styrene-based monomers such as styrene and α-methylstyrene; carboxyl group-containing monomers such as (meth)acrylic acid, maleic acid, and maleic anhydride; and alkyl (meth)acrylate compounds such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, and isothioyl (meth)acrylate. ; (meth)acrylate compounds containing oxygen atoms such as 2-hydroxyethyl (meth)acrylate, glycerol (meth)acrylate, polyoxyethylene (meth)acrylate, and glycidyl (meth)acrylate; nitrile-containing monomers such as (meth)acrylonitrile; vinyl acetate, vinyl butyrate, vinyl laurate, and vinyl stearate; unsaturated hydrocarbons such as ethylene, propylene, isoprene, and butadiene; halogen-containing monomers such as trifluoromethyl (meth)acrylate, pentafluoroethyl (meth)acrylate, vinyl chloride, vinyl fluoride, and chlorostyrene.

[0089] Examples of the crosslinking monomer include tetramethylolmethane tetra(meth)acrylate, tetramethylolmethane tri(meth)acrylate, tetramethylolmethane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, glycerol tri(meth)acrylate, glycerol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, and the like. Multifunctional (meth)acrylate compounds such as (meth)acrylate, (poly)tetramethylene glycol di(meth)acrylate, and 1,4-butanediol di(meth)acrylate; silane-containing monomers such as triallyl (iso)cyanurate, triallyl trimellitate, divinylbenzene, diallyl phthalate, diallylacrylamide, diallyl ether, γ-(meth)acryloyloxypropyltrimethoxysilane, trimethoxysilylstyrene, and vinyltrimethoxysilane.

[0090] The resin particles can be obtained by polymerizing the polymerizable monomer having an ethylenically unsaturated group using a known method. Examples of such methods include suspension polymerization in the presence of a free radical polymerization initiator, and polymerization using non-crosslinked seed particles and swelling the monomer with a free radical polymerization initiator.

[0091] When the substrate particles are inorganic particles other than metal particles or organic-inorganic hybrid particles, examples of the inorganic material used as the substrate particles include silica, alumina, barium titanate, zirconium oxide, and carbon black. Preferably, the inorganic material is not a metal. The silica particles are not particularly limited. For example, particles obtained by hydrolyzing a silicon compound having two or more hydrolyzable alkoxysilyl groups to form crosslinked polymer particles, followed by optional calcination, can be used. Examples of the organic-inorganic hybrid particles include those formed from a crosslinked alkoxysilyl polymer and an acrylic resin.

[0092] The organic-inorganic hybrid particles are preferably core-shell organic-inorganic hybrid particles having a core and a shell disposed on the surface of the core. The core is preferably an organic core. The shell is preferably an inorganic shell. To more effectively reduce the connection resistance between electrodes, the substrate particles are preferably organic-inorganic hybrid particles having an organic core and an inorganic shell disposed on the surface of the organic core.

[0093] As the material of the organic core, the material of the resin particles mentioned above can be mentioned.

[0094] The inorganic shell material may be any of the inorganic substances listed above as materials for the substrate particles. The inorganic shell material is preferably silicon dioxide. The inorganic shell is preferably formed by forming a shell of a metal alkoxide on the surface of the core using a sol-gel method and then calcining the shell. The metal alkoxide is preferably a silane alkoxide. The inorganic shell is preferably formed from a silane alkoxide.

[0095] When the substrate particles are metal particles, examples of the metal material of the metal particles include silver, copper, nickel, silicon, gold, titanium, and alloys such as solder.

[0096] The particle size of the substrate particles is preferably 0.01 μm or larger, more preferably 0.05 μm or larger, further preferably 0.5 μm or larger, further preferably 1 μm or larger, and particularly preferably 3 μm or larger, and preferably 50 μm or smaller, more preferably 30 μm or smaller, further preferably 20 μm or smaller, and particularly preferably 10 μm or smaller. When the particle size of the substrate particles is above the lower limit, the conductive reliability is further improved. Furthermore, when the conductive portion is formed on the surface of the substrate particles, aggregation is less likely to occur, and agglomerated conductive particles are less likely to form. When the particle size of the substrate particles is below the upper limit, the conductive particles are easily compressed, which can more effectively reduce the connection resistance between electrodes connected via the conductive particles.

[0097] The particle size of the substrate particles is preferably an average particle size, more preferably a number-average particle size. The number-average particle size of the substrate particles can be measured, for example, as follows. Conductive particles are added to "Technovit 4000" manufactured by Kulzer to a concentration of 30% by weight and dispersed to prepare an embedding resin for substrate particle inspection. Using an ion milling device ("IM4000" manufactured by Hitachi High-Technologies), a cross-section of the conductive particles is cut out, passing through the vicinity of the center of the substrate particles dispersed in the embedding resin for substrate particle inspection. Subsequently, using a field emission scanning electron microscope (FE-SEM) with an image magnification of 25,000x, 50 randomly selected conductive particles are observed for the substrate particles of each conductive particle. The particle size of the substrate particles in each conductive particle is measured, and the arithmetic average of these values ​​is calculated as the average particle size of the substrate particles.

[0098] (Conductive part) The conductive portion preferably comprises a metal. The metal constituting the conductive portion is not particularly limited. Examples of the metal include gold, silver, copper, platinum, palladium, zinc, lead, aluminum, cobalt, indium, ruthenium, nickel, chromium, titanium, antimony, bismuth, germanium, and cadmium, as well as alloys thereof. In addition, tin-doped indium oxide (ITO) may be used as the metal. Only one of the metals may be used, or two or more may be used in combination. From the perspective of lowering the connection resistance between the electrodes, an alloy containing tin, nickel, palladium, ruthenium, silver, copper, or gold is preferred, and nickel or palladium is more preferred.

[0099] From the perspective of more effectively improving conduction reliability, it is preferred that the conductive portion include nickel, and it is more preferred that the outer surface portion of the conductive portion include nickel.

[0100] The nickel content in 100% by weight of the conductive portion comprising nickel is preferably 10% by weight or greater, more preferably 50% by weight or greater, even more preferably 60% by weight or greater, even more preferably 70% by weight or greater, and particularly preferably 90% by weight or greater. The nickel content in 100% by weight of the conductive portion comprising nickel may also be 99% by weight or less, 90% by weight or less, or 70% by weight or less.

[0101] The conductive portion may be formed from a single layer. Alternatively, it may be formed from multiple layers. That is, the conductive portion may have a laminated structure comprising two or more layers. When the conductive portion is formed from multiple layers, the metal constituting the outermost layer is preferably an alloy containing gold, silver, nickel, palladium, ruthenium, copper, or tin, more preferably nickel. When the metal constituting the outermost layer is one of these preferred metals, the connection resistance between the electrodes is further reduced.

[0102] The method for forming the conductive portion on the surface of the substrate particles is not particularly limited. As the method for forming the conductive portion, for example, there can be mentioned: a method based on electroless plating, a method based on electroplating, a method based on physical collision, a method based on mechanochemical reaction, a method based on physical vapor deposition or physical adsorption, and a method of applying a paste containing metal powder or metal powder and an adhesive to the surface of the substrate particles. The method for forming the conductive portion is preferably a method based on electroless plating, electroplating or physical collision. As the above-mentioned method based on physical vapor deposition, there can be mentioned methods such as vacuum evaporation, ion plating and ion sputtering. In addition, among the above-mentioned methods based on physical collision, for example, Theta Composer (manufactured by Tokuju Kosho Co., Ltd.) is used.

[0103] The thickness of the conductive portion is preferably 0.005 μm or greater, more preferably 0.01 μm or greater, and preferably 10 μm or less, more preferably 1 μm or less, and even more preferably 0.3 μm or less. When the thickness of the conductive portion is above the lower limit and below the upper limit, sufficient conductivity can be achieved, and the conductive particles can be sufficiently deformed during connection without excessive hardening of the conductive particles.

[0104] When the conductive portion is formed from multiple layers, the thickness of the outermost conductive portion is preferably 0.001 μm or greater, more preferably 0.01 μm or greater, and preferably 0.5 μm or less, more preferably 0.1 μm or less. If the thickness of the outermost conductive portion is above the lower limit and below the upper limit, the outermost conductive portion becomes uniform, corrosion resistance is sufficiently improved, and connection resistance between electrodes can be sufficiently reduced.

[0105] The thickness of the conductive portion can be measured by observing a cross section of the conductive particle using a transmission electron microscope (TEM), for example.

[0106] Core material: The conductive particles preferably have a plurality of protrusions on the outer surface of the conductive portion. In many cases, an oxide film forms on the surface of the electrodes connected by the conductive particles. When using conductive particles with protrusions on the surface of the conductive portion, the protrusions can be used to effectively remove the oxide film by placing the conductive particles between the electrodes and performing pressure bonding. This ensures more reliable contact between the electrode and the conductive portion, lowering the connection resistance between the electrodes. Furthermore, the protrusions of the conductive particles can effectively remove filler between the conductive particles and the electrode during connection between the electrodes. This improves the reliability of the conduction between the electrodes.

[0107] Examples of methods for forming the protrusions include: a method in which a core material is attached to the surface of a substrate particle and then a conductive portion is formed by electroless plating; a method in which a conductive portion is formed on the surface of a substrate particle by electroless plating, a core material is attached, and then a conductive portion is formed by electroless plating. Alternatively, a method in which, without using a core material, a conductive portion is formed on the surface of a substrate particle by electroless plating, a plating layer is deposited in the form of a protrusion on the surface of the conductive portion, and then a conductive portion is formed by electroless plating.

[0108] Examples of methods for attaching the core material to the surface of substrate particles include adding the core material to a dispersion of the substrate particles, causing the core material to aggregate and adhere to the substrate particles' surfaces via van der Waals forces, and adding the core material to a container containing the substrate particles, causing the core material to adhere to the substrate particles' surfaces via mechanical forces such as the rotation of the container. From the perspective of controlling the amount of attached core material, a method for attaching the core material to the substrate particles' surfaces is preferably one in which the core material aggregates and adheres to the substrate particles' surfaces in a dispersion.

[0109] Materials constituting the core material include conductive 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 silicon dioxide, aluminum oxide, titanium oxide, tungsten carbide, and zirconium oxide. To further enhance the reliability of electrical conduction between electrodes, the core material is preferably a metal.

[0110] The metal is not particularly limited. Examples of the metal include gold, silver, copper, platinum, zinc, iron, lead, tin, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, germanium, and cadmium, as well as alloys containing two or more metals such as tin-lead alloys, tin-copper alloys, tin-silver alloys, tin-lead-silver alloys, and tungsten carbide. To further improve the reliability of electrical conduction between electrodes, the metal is preferably nickel, copper, silver, or gold. The metal may be the same as or different from the metal constituting the conductive portion.

[0111] The shape of the core material is not particularly limited. The core material is preferably in a block shape. Examples of the core material include a particle-shaped block, an aggregated block formed by agglomerating a plurality of fine particles, and an amorphous block.

[0112] The particle size (average particle size) of the core material is preferably 0.001 μm or greater, more preferably 0.05 μm or greater, and preferably 0.9 μm or less, more preferably 0.2 μm or less. If the particle size of the core material is above the lower limit and below the upper limit, the connection resistance between the electrodes can be effectively reduced.

[0113] The particle size of the core material is preferably an average particle size, more preferably a number average particle size. The particle size of the core material can be determined, for example, by observing 50 random core materials using an electron microscope or an optical microscope and calculating the average particle size of each core material, or by performing laser diffraction particle size distribution measurement.

[0114] <Hardener> From the perspective of curing the curable compound containing the polymerizable monomer having an alicyclic skeleton, the curing agent is preferably a polymerization initiator. Examples of the polymerization initiator include photopolymerization initiators and thermal polymerization initiators. These polymerization initiators may be used alone or in combination of two or more.

[0115] From the perspective of curing the curable compound by heating, the polymerization initiator preferably comprises a thermal polymerization initiator. The thermal polymerization initiator preferably comprises a thermal radical polymerization initiator, and is preferably a thermal radical polymerization initiator. Examples of the thermal radical polymerization initiator include peroxide-based radical polymerization initiators, azo-based radical polymerization initiators, and redox-based radical polymerization initiators.

[0116] Examples of the azo-based radical polymerization initiator include azobisisobutyronitrile, azobiscyclohexanecarbonitrile, and azobisdimethylvaleronitrile.

[0117] Examples of the peroxide-based free radical polymerization initiator include diacyl-based free radical polymerization initiators, peroxyester-based free radical polymerization initiators, dialkyl-based free radical polymerization initiators, percarbonate-based free radical polymerization initiators, and ketone peroxide-based free radical polymerization initiators. Examples of the diacyl-based free radical polymerization initiator include lauryl peroxide and benzoyl peroxide. Examples of the peroxyester-based free radical polymerization initiator include t-butyl perbenzoate, t-butyl peroxyacetate, t-butyl peroxypivalate, and t-butyl peroxy-2-ethylhexanoate. Examples of the dialkyl-based free radical polymerization initiator include diisopropyl peroxydicarbonate. Examples of the ketone peroxide-based free radical polymerization initiator include methyl ethyl ketone peroxide.

[0118] The redox-based free radical polymerization initiator comprises, for example, a peroxide and a reducing agent or a metal-containing compound. Specific examples of the redox-based free radical polymerization initiator include mixtures of benzoyl peroxide and organic amines, mixtures of the peroxyester-based free radical polymerization initiator and a reducing agent such as a thiol, and mixtures of methyl ethyl ketone peroxide and an organic cobalt salt.

[0119] From the viewpoint of improving reactivity and storage stability, the polymerization initiator preferably includes a peroxide-based free radical polymerization initiator.

[0120] From the perspective of improving reactivity and storage stability, the content of the hardener (polymerization initiator) in 100 wt % of the conductive paste is preferably 0.1 wt % or more, more preferably 0.3 wt % or more, and further preferably 0.5 wt % or more, and preferably 5 wt % or less, more preferably 4 wt % or less, and further preferably 3 wt % or less.

[0121] The content of the hardener (polymerization initiator) is preferably 0.3 parts by weight or more, more preferably 0.5 parts by weight or more, and even more preferably 0.7 parts by weight or more, relative to 100 parts by weight of the curable compound in the conductive paste, and is preferably 6 parts by weight or less, more preferably 5 parts by weight or less, and even more preferably 4 parts by weight or less. When the content of the hardener (polymerization initiator) is above the lower limit and below the upper limit, reactivity and storage stability can be improved.

[0122] <Other ingredients> The conductive paste may also contain ingredients other than the curable compound, the curing agent, and the plurality of conductive fillers. Other ingredients include solvents, inorganic fillers, organic fillers, colorants, polymerization inhibitors, chain transfer agents, antioxidants, UV absorbers, defoamers, leveling agents, surfactants, lubricants, anti-blocking agents, waxes, masking agents, deodorants, fragrances, preservatives, antimicrobial agents, antistatic agents, and adhesion-imparting agents.

[0123] (RFID inlay and method for manufacturing the same) The RFID inlay of the present invention comprises a substrate having wiring on its surface, a chip having electrodes on its surface, and a bonding portion for bonding the substrate and the chip. In the RFID inlay of the present invention, the bonding portion is made of the conductive paste. In the RFID inlay of the present invention, the wiring and the electrodes are electrically connected via the conductive filler in the bonding portion.

[0124] FIG1 is a cross-sectional view schematically showing an RFID inlay using the conductive paste according to the first embodiment of the present invention.

[0125] RFID inlay 81 shown in Figure 1 comprises a substrate 82 having wiring on its surface, a chip 83 having electrodes on its surface, and a bonding portion 84 that bonds substrate 82 and chip 83. Bonding portion 84 is made of a conductive paste containing conductive filler 1. Bonding portion 84 is preferably formed by curing the conductive paste containing conductive filler 1.

[0126] The substrate 82 has wiring 82 a on its surface (upper surface). The chip 83 has electrodes 83 a on its surface (lower surface). The wiring 82 a and the electrodes 83 a are electrically connected via the conductive filler 1 in the adhesive portion 84 .

[0127] The manufacturing method of the RFID inlay of the present invention includes the following steps (1) to (3). (1) A first arrangement step, which is to arrange the conductive paste on the surface of a substrate having wiring on the surface. (2) A second arrangement step, which is to arrange a chip having electrodes on the surface of the conductive paste on the surface opposite to the substrate. (3) A subsequent step, which is to heat and pressurize the conductive paste to form a bonding portion that bonds the substrate and the chip, and to electrically connect the wiring and the electrodes using the conductive filler in the bonding portion.

[0128] The RFID inlay and the manufacturing method of the RFID inlay of the present invention can improve the adhesion between the substrate and the chip and improve the conduction reliability because they use a specific conductive paste.

[0129] In the above-mentioned RFID inlay manufacturing method, the substrate is preferably in a long strip shape. In the first arrangement step, the second arrangement step, and the subsequent step, the RFID inlay is manufactured by conveying the long strip substrate in a roll-to-roll manner. In this case, multiple RFID inlays can be manufactured continuously, further improving the efficiency of RFID inlay manufacturing.

[0130] When a roll-to-roll method is used, the transport speed of the substrate is not particularly limited.

[0131] Examples of methods for disposing the conductive paste include coating with a dispenser, screen printing, and ejection with an inkjet device.

[0132] The heating temperature in the subsequent step is preferably 100°C or higher, more preferably 150°C or higher, and preferably 400°C or lower, more preferably 300°C or lower, and even more preferably 250°C or lower. If the heating temperature in the subsequent step is above the lower limit and below the upper limit, good electrical connection between the chip and the wiring (antenna pattern) can be achieved.

[0133] The pressing pressure in the bonding step is preferably 0.5 N or greater, more preferably 1 N or greater, and preferably 3.5 N or less, more preferably 3 N or less, and further preferably 2.5 N or less. If the pressing pressure in the bonding step is greater than the lower limit and less than the upper limit, the adhesion between the substrate and the wafer can be improved, and the conduction reliability can be improved.

[0134] The heating and pressing time in the above-mentioned subsequent step is not particularly limited. The heating and pressing time in the above-mentioned subsequent step can be more than 2 seconds, can be less than 15 seconds, or can be less than 10 seconds.

[0135] The RFID inlay can be cut to a specific size as needed, or it can be used after cutting. Preferably, a plurality of the chips are bonded to a long strip of substrate using a plurality of the bonding portions. Alternatively, a stack of the chips and the bonding portions can be arranged on the long strip of substrate. Preferably, in the first arrangement step, the conductive paste is applied to a plurality of locations on the surface of the long strip of substrate. Preferably, in the second arrangement step, a plurality of chips are used and arranged on the surface opposite the substrate side of each of the conductive pastes applied to the plurality of locations. Alternatively, the chips can be bonded to the long strip of substrate using the bonding portions and then cut.

[0136] The substrate is not particularly limited. It is preferably a circuit substrate. Examples of the circuit substrate include resin films, flexible printed circuit boards, rigid flexible substrates, glass substrates, and paper substrates. The substrate may be a resin substrate, a glass substrate, or a paper substrate.

[0137] The substrate has wiring (antenna pattern) on its surface. The wiring (antenna pattern) is formed on the surface of the substrate. The substrate preferably has a base material and wiring (antenna pattern) arranged on the surface of the base material.

[0138] Examples of the substrate material include resin, glass, and paper. Examples of the resin include PET (polyethylene terephthalate), PP (polypropylene), and PVC (polyvinyl chloride). The paper may also be impregnated with epoxy resin or phenolic resin. To further improve adhesion and enable roll-to-roll production of RFID inlays, the substrate material is preferably resin or paper, more preferably PET (polyethylene terephthalate) or paper. The substrate can be resin, glass, or paper.

[0139] Examples of the wiring (antenna pattern) include gold wiring, nickel wiring, tin wiring, aluminum wiring, silver wiring, SUS wiring, copper wiring, molybdenum wiring, and tungsten wiring. Aluminum wiring is preferred for improved sensitivity in the UHF band (860 MHz to 920 MHz).

[0140] From the perspective of suppressing deformation of the substrate due to heat when mounting a chip (e.g., an IC chip) and improving flexibility, the thickness of the substrate is preferably 20 μm or more, more preferably 30 μm or more, and preferably 200 μm or less, more preferably 100 μm or less.

[0141] The shapes of the substrate and base material are not particularly limited. To facilitate roll-to-roll manufacturing of RFID inlays, the substrate and base material are preferably in the form of long strips. The length of the substrate and base material is not particularly limited. The length of the substrate and base material can be greater than 1 m, greater than 10 m, less than 5000 m, or less than 1000 m.

[0142] The surface tension of the substrate (base material) is preferably 30 mN / m or higher, more preferably 32 mN / m or higher, and even more preferably 34 mN / m or higher, and is preferably 50 mN / m or lower, more preferably 48 mN / m or lower, and even more preferably 45 mN / m or lower. If the surface tension of the substrate (base material) is above the lower limit and below the upper limit, adhesion can be further improved. The conductive paste of the present invention is suitable for application to substrates (base materials) having a surface tension above the lower limit and below the upper limit.

[0143] The surface tension of the substrate can be measured according to JIS K6768 using the following method. Dip a cotton swab into the JIS standard liquid and apply it to the substrate. Calculate the surface tension based on the shape of the coating two seconds after application.

[0144] Examples of the wafer include semiconductor wafers (IC wafers) and the like.

[0145] The wafer has electrodes on its surface. Examples of these electrodes include metal electrodes such as gold, nickel, tin, aluminum, silver, SUS, copper, molybdenum, and tungsten. To further enhance conduction reliability, these electrodes are preferably copper or gold, more preferably copper.

[0146] The number of electrodes per chip is not particularly limited. The number of electrodes per chip may be 1 or more, 4 or more, 20 or less, or 10 or less.

[0147] The shape of the wafer is not particularly limited and can be rectangular, triangular, or circular.

[0148] The wafer preferably has a planar surface area of ​​0.04 mm² or greater, more preferably 0.09 mm² or greater, and even more preferably 0.16 mm² or greater, and preferably 0.50 mm² or less, more preferably 0.40 mm² or less, and even more preferably 0.30 mm² or less. If the wafer has a planar surface area above this lower limit, the conductive paste can be precisely applied to fine wiring. If the wafer has a planar surface area below this upper limit, conductive reliability can be maintained even when the RFID inlay is exposed to high temperature and high humidity for extended periods of time. The conductive paste of the present invention is suitable for bonding relatively small wafers.

[0149] The present invention is described in detail below with reference to Examples and Comparative Examples. However, the present invention is not limited to the following Examples.

[0150] Prepare the following materials.

[0151] (hardening compound): Polymerizable monomers with an alicyclic skeleton: Isobutyl acrylate ("IBXA" manufactured by Kyoei Chemical Co., Ltd., molecular weight: 208) Tricyclodecane dimethanol diacrylate ("IRR-214" manufactured by DAICEL-ALLNEX, molecular weight: 304) 1,4-Cyclohexanedimethanol monoacrylate ("CHDMMA" manufactured by Mitsubishi Chemical, molecular weight: 198) Polymerizable monomers without an alicyclic skeleton: Polyester urethane acrylate ("UN-353" manufactured by Negami Industries, molecular weight (weight average molecular weight): 5000) Polyether urethane acrylate ("UN-6306" manufactured by Negami Industries, molecular weight (weight average molecular weight): 6600) Trimethylolpropane triacrylate ("A-TMPT" manufactured by Shin-Nakamura Chemical Industry Co., Ltd., molecular weight: 296) Hydroxyethyl methacrylate (manufactured by FUJIFILM Wako Pure Chemical Co., Ltd., molecular weight: 130) 2-Phenoxyethyl acrylate ("EBCRYL 114" manufactured by DAICEL-ALLNEX, molecular weight: 192)

[0152] Conductive filler: Sekisui Chemical Co., Ltd. "NIELB-005-S" (conductive particles having a substrate particle and a conductive portion on the surface of the substrate particle; nickel content in 100% by weight of the conductive portion: 52% by weight; average particle size: 5 μm) NIKKO RICA "4SP-10" (metal particles (nickel), average particle size: 6.5 μm) Mitsui Mining & Smelting Co., Ltd. "1300Y" (metal particles (copper), average particle size: 3.5 μm)

[0153] Hardener: PERBUTYL PV manufactured by NOF Corporation (peroxyester-based free radical polymerization initiator (tert-butyl peroxybutyrate))

[0154] Inorganic fillers: Silicon dioxide ("SSP-04M" manufactured by Tokuyama)

[0155] chip: IC chip (copper electrodes, NXP UCODE7, surface area: 0.22 mm²)

[0156] Substrate: PET film (long strip, resin film with aluminum wiring operating in the UHF band (860 MHz to 920 MHz), surface tension: 43 mN / m)

[0157] (Example 1) (1) Production of conductive paste The materials shown in Table 1 below were mixed in the amounts shown in Table 1 below and stirred using a planetary stirring device ("Defoaming Stirring Taro" manufactured by Thinky Co., Ltd.) to obtain a conductive paste (anisotropic conductive paste).

[0158] (2) Production of RFID inlays The resulting conductive paste is applied to a PET film by jet dispensing to form a conductive paste layer (adhesive layer) (first placement step). An IC chip is then laminated onto the surface of the conductive paste layer (adhesive layer) opposite the substrate, with the wiring on the PET film facing the electrodes on the chip (second placement step). The conductive paste layer (adhesive layer) is then cured by thermocompression bonding using an upper heating tool at 180°C, a lower heating tool at 175°C, a pressure of 2 N, and a pressing time of 7 seconds, forming a bond. Furthermore, the wiring on the PET film surface and the electrodes on the chip surface are electrically connected via the conductive filler (conductive particles) in the adhesive layer, resulting in a connected structure (bonding step). The first placement step, the second placement step, and the bonding step are performed using a "DDA40000" manufactured by Mühlbauer (roll-to-roll process). The obtained connected structure was cut into pieces of 5 cm × 1.5 cm using a "DCL30000" manufactured by Muhlbauer, to obtain 50 RFID inlays.

[0159] (Examples 2 to 10 and Comparative Examples 1 to 3) The conductive paste and RFID inlay were obtained in the same manner as in Example 1 except that the ingredients and amounts of the conductive paste were changed as shown in Tables 1, 3, and 5.

[0160] (evaluate) (1) Water absorption rate of hardened material The resulting conductive paste was heated at 130°C for 10 minutes to obtain a cured product (pre-test cured product). This cured product was then immersed in water at 121°C, 100% RH, and 2 atm for 2 hours to obtain a post-test cured product. The weight of the cured product before and after the test was measured, and the water absorption rate of the cured product was calculated as follows. Water absorption rate of the cured product (%) = (weight of the cured product after the test - weight of the cured product before the test) × 100 / weight of the cured product before the test

[0161] (2) Storage module The hardened material before and after the test obtained in (1) was cut into pieces with a length of 10 mm, a width of 1 mm to 10 mm, and a height of 15 mm to 50 mm to prepare measurement samples. For each measurement sample, a dynamic viscoelasticity measuring apparatus ("RSA3" manufactured by TA Instruments) was used to measure the storage modulus of the hardened material before and after the test under the conditions of a frequency of 10 Hz, a strain of 0.1%, a temperature of 20°C to 180°C, and a heating rate of 10°C / min. In addition, the ratio (storage modulus of the hardened material after the test / storage modulus of the hardened material before the test) was calculated.

[0162] (3) Conductivity reliability Fifty RFID inlays were placed in a dark box shielded from external radio waves. Using a frequency reader (Voyantic's "Tagformance Pro"), the peak sensitivity at 25°C in the UHF band (860 MHz to 920 MHz) was measured as the initial peak sensitivity. Furthermore, the RFID inlays were immersed in water for 30 minutes and then dried. The peak sensitivity of the immersed RFID inlays was similarly measured at 25°C in the UHF band, and the absolute value of the difference from the initial peak sensitivity was calculated. The initial and post-immersion conductivity reliability was evaluated according to the following criteria.

[0163] [Initial conduction reliability criteria] ○○: The initial peak sensitivity of all RFID inlays does not reach -18 dBm ○: Does not belong to any of ○○ and × ×: The initial peak sensitivity of at least one RFID inlay is -17 dBm or higher

[0164] [Judgment criteria for conduction reliability after immersion] ○○: The absolute value of the difference in peak sensitivity of all RFID inlays does not reach 2 dBm ○: Does not belong to any of ○○ and × ×: The absolute value of the initial peak sensitivity difference of at least one RFID inlay is 3 dBm or more

[0165] The composition of the conductive paste and the results are shown in Tables 1 to 6 below.

[0166] [Table 1] Example 1 Example 2 Example 3 Example 4 Example 5 Conductive paste Hardening compound Isobutyl acrylate parts by weight 35 25 10 35 20 Tricyclodecane dimethanol diacrylate parts by weight 1,4-Cyclohexanedimethanol monoacrylate parts by weight 15 Polyester urethane acrylate parts by weight 40 40 40 40 Polyether urethane acrylate parts by weight 40 Trimethylolpropane triacrylate parts by weight 5 5 5 5 5 Hydroxyethyl methacrylate parts by weight 10 25 2-Phenoxyethyl acrylate parts by weight Conductive fillers NIELB-005-S parts by weight 7 7 7 7 7 4SP-10 parts by weight 1300Y parts by weight hardener PERBUTYL PV parts by weight 1 1 1 1 1 Silicon dioxide SSP-04M parts by weight 20 20 20 20 20 Content of polymerizable monomer having an alicyclic skeleton in 100% by weight of the curable compound weight% 43.8 31.3 12.5 43.8 43.8

[0167] [Table 2] Example 1 Example 2 Example 3 Example 4 Example 5 evaluate Water absorption of hardened material % 0.15 0.41 1.65 0.48 0.52 Storage module Storage modulus of the cured product before testing Gpa 2.23 1.67 1.08 0.88 1.00 Storage modulus of the cured product after the test Gpa 1.81 1.07 0.47 0.68 0.33 Ratio (storage modulus of the cured product after the test / storage modulus of the cured product before the test) - 0.81 0.64 0.44 0.77 0.33 Conductivity reliability initial - ○ ○ ○ ○ ○ After immersion - ○○ ○○ ○ ○○ ○

[0168] [Table 3] Example 6 Example 7 Example 8 Example 9 Example 10 Conductive paste Hardening compound Isobutyl acrylate parts by weight 35 45 25 25 Tricyclodecane dimethanol diacrylate parts by weight 35 1,4-Cyclohexanedimethanol monoacrylate parts by weight Polyester urethane acrylate parts by weight 40 30 40 40 40 Polyether urethane acrylate parts by weight Trimethylolpropane triacrylate parts by weight 5 5 5 5 5 Hydroxyethyl methacrylate parts by weight 10 10 2-Phenoxyethyl acrylate parts by weight Conductive fillers NIELB-005-S parts by weight 7 7 7 4SP-10 parts by weight 27 1300Y parts by weight 27 hardener PERBUTYL PV parts by weight 1 1 1 1 1 Silicon dioxide SSP-04M parts by weight 40 20 20 20 20 Content of polymerizable monomer having an alicyclic skeleton in 100% by weight of the curable compound weight% 43.8 56.3 43.8 31.3 31.3

[0169] [Table 4] Example 6 Example 7 Example 8 Example 9 Example 10 evaluate Water absorption of hardened material % 0.13 0.15 0.13 0.35 0.33 Storage module Storage modulus of the cured product before testing Gpa 2.61 2.29 2.45 1.84 1.76 Storage modulus of the cured product after the test Gpa 2.22 1.92 1.99 1.28 1.20 Ratio (storage modulus of the cured product after the test / storage modulus of the cured product before the test) - 0.85 0.84 0.81 0.70 0.68 Conductivity reliability initial - ○ ○ ○ ○ ○ After immersion - ○○ ○ ○○ ○○ ○

[0170] [Table 5] Comparative Example 1 Comparative Example 2 Comparative Example 3 Conductive paste Hardening compound Isobutyl acrylate parts by weight Tricyclodecane dimethanol diacrylate parts by weight 1,4-Cyclohexanedimethanol monoacrylate parts by weight 35 Polyester urethane acrylate parts by weight 40 40 40 Polyether urethane acrylate parts by weight Trimethylolpropane triacrylate parts by weight 5 5 5 Hydroxyethyl methacrylate parts by weight 35 2-Phenoxyethyl acrylate parts by weight 35 Conductive fillers NIELB-005-S parts by weight 7 7 7 4SP-10 parts by weight 1300Y parts by weight hardener PERBUTYL PV parts by weight 1 1 1 Silicon dioxide SSP-04M parts by weight 20 20 20 Content of polymerizable monomer having an alicyclic skeleton in 100% by weight of the curable compound weight% 0.0 0.0 43.8

[0171] [Table 6] Comparative Example 1 Comparative Example 2 Comparative Example 3 evaluate Water absorption of hardened material % 2.78 0.20 2.16 Storage module Storage modulus of the cured product before testing Gpa 0.81 0.096 0.32 Storage modulus of the cured product after the test Gpa 0.22 0.071 0.07 Ratio (storage modulus of the cured product after the test / storage modulus of the cured product before the test) - 0.27 0.74 0.22 Conductivity reliability initial - ○ ○ ○ After immersion - × × ×

[0172] 1: Conductive filler 81:RFID Inlay 82: Substrate with wiring on the surface 82a: Wiring 83: Chip with electrodes on the surface 83a: Electrode 84: Continuation

Claims

1. A conductive paste comprising a curing compound, a curing agent, and a plurality of conductive fillers, wherein the curing compound comprises a polymeric monomer having an alicyclic backbone, and when the cured conductive paste is immersed in water for 2 hours at 121°C, 100% RH, and 2 atm, the water absorption rate of the cured paste is 0.1% to 1.7%: Water absorption rate (%) of the cured paste = (weight of the cured paste after the test - weight of the cured paste before the test) × 100 / weight of the cured paste before the test.

2. The conductive paste of claim 1, wherein the storage modulus of the cured material before the above test is 0.8 GPa or more and 3.0 GPa or less, and the storage modulus of the cured material after the above test is 0.3 GPa or more and 2.5 GPa or less.

3. The conductive paste of claim 1 or 2, wherein the ratio of the storage modulus of the cured material after the above test to the storage modulus of the cured material before the above test is 0.33 or more and 0.9 or less.

4. The conductive paste of claim 1 or 2, wherein the polymeric monomer having an alicyclic backbone has a (meth)acrylic group.

5. The conductive paste as claimed in claim 1 or 2, wherein the polymerizable monomer having an alicyclic backbone is tricyclodecanediethanol di(meth)acrylate or isomethacrylate.

6. The conductive paste of claim 1 or 2, wherein the content of the polymerizable monomer having an alicyclic backbone in 100% by weight of the curing compound is more than 10% by weight and less than 50% by weight.

7. The conductive paste as claimed in claim 1 or 2, wherein the conductive filler comprises nickel.

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

9. An RFID inlay comprising a substrate having wiring on its surface, a chip having electrodes on its surface, and a bonding portion for bonding the substrate and the chip, wherein the bonding portion is made of conductive paste as claimed in any one of claims 1 to 8, and the wiring and the electrodes are electrically connected by the conductive filler in the bonding portion.

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

11. The method for manufacturing an RFID inlay as claimed in claim 10, wherein the substrate is elongated, and the RFID inlay is manufactured by conveying the elongated substrate in a roll-to-roll manner in the first configuration step, the second configuration step, and the connecting step.

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