Conductive composition, conductive sheet, laminate, connection structure, and method for producing connection structure

Abstract

The present invention provides a conductive composition with which separation does not occur easily even when a warped wiring circuit board and a semiconductor chip are used. The conductive composition according to an embodiment of the present invention contains conductive particles and a resin. The conductive composition has a storage modulus of 10 kPa or more at 50 °C.

Description

Conductive composition, conductive sheet, laminate, connection structure, and method for producing connection structure

[0001] The present invention relates to a conductive composition, a conductive sheet, a laminate, a connection structure, and a method for producing a connection structure.

[0002] Conventionally, anisotropic conductive compositions have been used for connecting two wiring circuit boards. When an anisotropic conductive composition is heated while being disposed between two wiring circuit boards, it exhibits conductivity in the lamination direction of the two wiring circuit boards, while ensuring insulation in the direction orthogonal to the lamination direction (in-plane direction).

[0003] As an anisotropic conductive composition, a combination of solder particles and a thermosetting resin is known (for example, Patent Document 1). When this anisotropic conductive composition is heated, the solder particles melt and aggregate between the electrode of one wiring circuit board and the electrode of the other wiring circuit board. Thereafter, the molten solder is cooled and solidified, whereby these electrodes are electrically connected. In regions where no electrodes are present, aggregation of the solder particles does not proceed, and insulation by the resin is maintained. Through such a mechanism, anisotropy in which electrical characteristics differ between the lamination direction and the in-plane direction of the two wiring circuit boards is expressed.

[0004] International Publication No. 2023 / 145487

[0005] In order to improve the performance of semiconductor packages, techniques for mounting a plurality of semiconductor chips and connecting these chips have been studied. In this technique, the size of semiconductor packages has been increasing to achieve further performance improvement. Additionally, since there are restrictions on the thickness of semiconductor packages, there is also a demand for thinner substrates and thinner semiconductor chips.

[0006] However, when the thickness of a wiring circuit board or the thickness of a semiconductor chip is reduced, both tend to warp easily. When a warped wiring circuit board and a warped semiconductor chip are used, even if the wiring circuit board and the semiconductor chip are bonded together via a conductive composition, peeling tends to occur between them.

[0007] The object of the present invention is to provide a conductive composition that is less prone to peeling, even when using a wiring circuit board and semiconductor chip that have warped.

[0008] [1] The conductive composition according to the embodiment of the present invention comprises conductive particles and a resin, and has a storage modulus of 10 kPa or more at 50°C. [2] The conductive composition described in [1] above may have a peel force of 0.30 N / 20 mm or more determined by the following test. Test: A conductive sheet (20 μm thick) made of the conductive composition is prepared on a support substrate made of polyethylene terephthalate, and then cut into strips measuring 50 mm in length and 20 mm in width to make a test piece. The test piece is attached to a stainless steel plate (SUS304 plate) via the conductive sheet, and a pressure of 0.3 MPa is applied for 2 seconds at a temperature of 80°C. The test piece is peeled off the stainless steel plate under conditions of a peel speed of 3000 mm / min and a peel angle of 180° in an atmosphere of 23°C and 50% RH. The maximum value of the force required at this time is identified as the peel force. [3] In the conductive composition described in [1] or [2] above, the conductive particles may be solder particles. [4] The conductive composition described in [3] above may have a minimum complex viscosity of 10 Pa·s or less determined by the following test. Test: The conductive composition, excluding the solder particles, is heated from 25°C to a temperature 30°C higher than the melting point T0 of the solder particles (T0 + 30°C) at a heating rate of 10°C / min. The complex viscosity of the conductive composition, excluding the solder particles, is measured from 25°C to the above temperature (T0 + 30°C), and its minimum value is determined. [5] In the conductive composition described in any of [1] to [4] above, the resin may include at least one selected from the group consisting of epoxy resin, (meth)acrylic resin, phenoxy resin, and phenolic resin. [6] In the conductive composition described in any of [1] to [5] above, the resin may include epoxy resin. [7] In the conductive composition described in [6] above, the weight-average molecular weight of the epoxy resin may be less than 10,000. [8] In the conductive composition described in [6] or [7] above, the epoxy resin may contain repeating units having glycidyl groups.[9] In the conductive composition according to any one of [6] to [8] above, the epoxy resin may have at least one selected from the group consisting of a dicyclopentadiene skeleton, a biphenyl skeleton, a naphthalene skeleton, a phenol skeleton, and a cresol skeleton.

[10] In the conductive composition according to any one of [6] to [9] above, the conductive composition may include a liquid epoxy resin and a solid epoxy resin.

[11] In the conductive composition according to any one of [6] to

[10] above, the content of the solid epoxy resin in the resin may be 50% by weight or more.

[12] In the conductive composition according to any one of [1] to

[11] above, the resin may include a polymer resin having a weight-average molecular weight of 10,000 or more.

[13] In the conductive composition according to

[12] above, the content of the polymer resin in the resin may be 20% by weight or less.

[14] The conductive composition according to any one of [1] to

[13] above may further include a flux.

[15] A conductive sheet according to an embodiment of the present invention is made of a conductive composition described in any of [1] to

[14] above.

[16] A laminate according to an embodiment of the present invention comprises the conductive sheet described in

[15] above, a release liner, and

[17] A connecting structure according to an embodiment of the present invention comprises a first substrate on which a first electrode is disposed, a second substrate on which a second electrode is disposed, and a connecting member connecting the first substrate and the second substrate, wherein the connecting member is formed of a conductive composition described in any of [1] to

[14] above.

[18] A method for manufacturing a connecting structure according to an embodiment of the present invention is a method for manufacturing a connecting structure according to

[17] above, comprising: arranging the conductive composition between the first substrate and the second substrate; and heating the conductive composition to form the connecting member.

[0009] According to embodiments of the present invention, it is possible to provide a conductive composition that is less prone to peeling even when using a wiring circuit board and semiconductor chip that have warped.

[0010] This is a graph illustrating the relationship between temperature and complex viscosity for a conductive composition excluding solder particles. This is a schematic cross-sectional view of a conductive sheet according to one embodiment of the present invention. This is a schematic cross-sectional view of a connecting structure according to one embodiment of the present invention. This is a diagram illustrating the manufacturing method of the connecting structure shown in Figure 3. This is a diagram illustrating the manufacturing method of the connecting structure shown in Figure 3.

[0011] ≪1. Conductive Composition≫ The conductive composition according to the embodiment of the present invention comprises conductive particles and a resin. The conductive composition has a storage modulus E of 10 kPa or more at 50°C. This conductive composition tends to suppress peeling even when warped wiring circuit boards are bonded together. The conductive composition of this embodiment can typically function as an anisotropic conductive composition.

[0012] The above-mentioned storage modulus E can be measured by the following method. First, a measurement sample S1 made of a conductive composition is prepared. The measurement sample S1 is disc-shaped, with a base diameter of 25.0 mm and a thickness of 500 ± 50 μm. The measurement sample S1 is preferably in a dry state. In this specification, "dry state" means that the solvent content remaining in the measurement sample S1 is 1000 wt ppm or less, preferably 500 wt ppm or less. It is preferable that the measurement sample S1 is substantially solvent-free. The measurement sample S1 may also be obtained by punching out a disc shape from a laminate of multiple conductive sheets made using the conductive composition. Next, dynamic viscoelasticity measurement is performed on the measurement sample S1 under the following measurement conditions. From the results of the dynamic viscoelasticity measurement, the storage modulus of the measurement sample S1 at 50°C is determined, and the obtained value is considered to be the storage modulus E of the conductive composition. Measurement conditions: Measurement environment: atmospheric atmosphere; Strain value: 0.5%; Measurement frequency: 1 Hz; Temperature range: 25°C to 300°C; Heating rate: 10°C / min; Shape: Parallel plate, 25.0 mm diameter

[0013] The storage modulus E of the conductive composition at 50°C is 10 kPa or more, as described above, and may be 15 kPa or more, 20 kPa or more, 25 kPa or more, 30 kPa or more, 40 kPa or more, 50 kPa or more, 60 kPa or more, 70 kPa or more, and even 80 kPa or more. The upper limit of the storage modulus E is, for example, 300 kPa or less, and may be 200 kPa or less, and even 100 kPa or less.

[0014] <1-1. Conductive Particles> As described above, the conductive composition contains conductive particles. The conductive particles are not particularly limited as long as they are conductive particles. There may be only one type of conductive particle or two or more types.

[0015] Examples of conductive particles include metal particles such as solder particles, nickel particles, gold-plated nickel particles, copper particles, silver particles, nanoparticles of metal crystals, and particles in which the surface of a metal is coated with another metal; and resin particles such as styrene resin, urethane resin, melamine resin, epoxy resin, acrylic resin, phenolic resin, and styrene-butadiene resin coated with a conductive thin film of gold, nickel, silver, copper, solder, etc.

[0016] The conductive particles are preferably solder particles. There may be only one type of solder particle or two or more types. From the viewpoint of environmental protection, the material of the solder particles is preferably lead-free solder material that does not contain lead.

[0017] The solder particles preferably contain tin (Sn). Solder particles containing tin tend to accelerate the hardening of the resin through metal catalytic action. In the solder particles, tin may exist in elemental form or form an alloy with other metals. Examples of tin alloys include tin-bismuth alloy (Sn-Bi), tin-silver-copper alloy (Sn-Ag-Cu), tin-silver alloy (Sn-Ag), and tin-bismuth-indium alloy (Sn-Bi-In).

[0018] When solder particles contain a tin-silver-copper alloy, the tin content in the tin-silver-copper alloy may be, for example, 90% by weight or more, and may be 95% by weight or more. The silver content in the tin-silver-copper alloy may be, for example, 10% by weight or less, and may be 5% by weight or less. The copper content in the tin-silver-copper alloy may be, for example, 1% by weight or less, and may be 0.5% by weight or less.

[0019] When the solder particles contain a tin-bismuth alloy, the tin content in the tin-bismuth alloy may be, for example, 80% by weight or less, or 50% by weight or less. The bismuth content in the tin-bismuth alloy may be, for example, 20% by weight or more, or 50% by weight or more.

[0020] The melting point T0 of solder particles is, for example, 70°C or higher, and may be 100°C or higher, 120°C or higher, 150°C or higher, 180°C or higher, or even 200°C or higher. The melting point T0 of solder particles is, for example, 280°C or lower, and may be 260°C or lower, or even 240°C or lower. The melting point can be measured by differential scanning calorimetry (DSC).

[0021] The shape of the conductive particles is not particularly limited as long as they are particulate, and examples include spherical, ellipsoidal, flaky, and fibrous shapes. Spherical conductive particles are preferred. The average particle diameter (average primary particle diameter) of the conductive particles is, for example, 20 μm or less, and may be 10 μm or less, 8 μm or less, 5 μm or less, or even 3 μm or less. Conductive particles with a small average particle diameter are suitable for the fabrication of miniaturized, low-profile connecting structures. The average particle diameter of the conductive particles may be, for example, 0.1 μm or more, or 0.5 μm or more. In this specification, the average particle diameter can be specified as the median diameter (D50) in the particle size distribution measured by a laser diffraction particle size distribution analyzer or the like.

[0022] The content of conductive particles in the conductive composition is, for example, 20% by weight or more, and may be 30% by weight or more, 40% by weight or more, 50% by weight or more, or even 60% by weight or more. The above content may be, for example, 80% by weight or less, and may be 70% by weight or less.

[0023] Furthermore, conductive particles (especially solder particles) may have an oxide film formed on their surface, but it is preferable that no oxide film is formed. The oxide film on conductive particles can be removed, for example, by performing an acid treatment on the conductive particles before preparing the conductive composition. Details of the method for removing the oxide film will be explained in section 1-6. Method for producing conductive compositions.

[0024] <1-2. Resin> As described above, the conductive composition includes a resin. As the resin, any resin known in the field of anisotropic conductive compositions can be used, such as thermosetting resins and thermoplastic resins. It is preferable that the resin includes a thermosetting resin.

[0025] The resin preferably contains at least one selected from the group consisting of epoxy resin, (meth)acrylic resin, phenoxy resin, and phenolic resin, and is particularly preferably epoxy resin. In this specification, "(meth)acrylic" means "acrylic and / or methacrylic".

[0026] (1-2-a. Epoxy Resins) The epoxy resin may be of one type or two or more types. The epoxy resin described in section (1-2-a. Epoxy Resins) typically has a weight-average molecular weight of less than 10,000 and is not classified as a polymer resin, as will be discussed later.

[0027] Epoxy resins are typically thermosetting. In other words, epoxy resins typically have at least one epoxy group (particularly a glycidyl group) in one molecule. The epoxy equivalent of an epoxy resin is, for example, 100 g / eq. or more, and may be 150 g / eq. or more, 180 g / eq. or more, 200 g / eq. or more, 225 g / eq. or more, 230 g / eq. or more, 250 g / eq. or more, and even 280 g / eq. or more. The above epoxy equivalent is, for example, 3000 g / eq. or less, and may be 2000 g / eq. or less, 1000 g / eq. or less, 800 g / eq. or less, 500 g / eq. or less, 400 g / eq. or less, and even 300 g / eq. or less. Note that epoxy equivalent refers to the molecular weight of the epoxy resin per equivalent of epoxy groups contained in the epoxy resin. If the conductive composition contains two or more types of epoxy resins, the average value of the epoxy equivalents may satisfy the above numerical range.

[0028] Epoxy resins preferably contain repeating units having epoxy groups (particularly glycidyl groups) in their molecules. Repeating units having epoxy groups are represented, for example, by the following formula (1).

[0029] In formula (1) above, A is a divalent linking group. Preferably, A includes a ring structure. Examples of ring structures include aliphatic rings such as dicyclopentadiene rings; aromatic rings such as benzene rings, biphenyl rings, and naphthalene rings. The ring structure may or may not have further substituents. The ring structure may be directly bonded to the benzene ring adjacent to A in formula (1), or it may be bonded via a linking group such as an alkylene group.

[0030] As shown in formula (1), the benzene ring adjacent to A has a glycidyl group. This benzene ring may further have other substituents besides the glycidyl group. Examples of other substituents include alkyl groups such as methyl groups.

[0031] Epoxy resins preferably have at least one selected from the group consisting of a dicyclopentadiene skeleton, a biphenyl skeleton, a naphthalene skeleton, a phenol skeleton, and a cresol skeleton in their molecules, more preferably at least one selected from the group consisting of a dicyclopentadiene skeleton, a biphenyl skeleton, and a naphthalene skeleton, and particularly preferably have a dicyclopentadiene skeleton. Epoxy resins having skeletons such as a dicyclopentadiene skeleton, a biphenyl skeleton, or a naphthalene skeleton are suitable for increasing the storage modulus E of a conductive composition at 50°C. Furthermore, these epoxy resins also tend to reduce the water absorption of the conductive composition.

[0032] The dicyclopentadiene skeleton can be represented, for example, by the following formula (2).

[0033] In formula (2) above, * indicates a bonding site with other structures. Formula (2) specifically represents a dicyclopentadiene ring functioning as a divalent linking group. This dicyclopentadiene ring may or may not have substituents. Examples of epoxy resins having a dicyclopentadiene skeleton include those in which A in the repeating unit of formula (1) above is represented by formula (2).

[0034] Furthermore, examples of epoxy resins having a biphenyl skeleton include those in which A is a biphenyl ring in the repeating unit of formula (1) above. Examples of epoxy resins having a naphthalene skeleton include those in which A is a naphthalene ring in the repeating unit of formula (1) above.

[0035] The epoxy resin included in the conductive composition of this embodiment is not limited to those described above. For example, the conductive composition may include other epoxy resins other than the epoxy resin having the repeating unit of formula (1) described above.

[0036] Specific examples of epoxy resins (thermosetting epoxy resins) include bisphenol-type epoxy resins (e.g., bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, and bisphenol S-type epoxy resin), novolac-type epoxy resins (e.g., phenol novolac-type epoxy resin, cresol novolac-type epoxy resin, and biphenyl-type epoxy resin), naphthalene-type epoxy resin, fluorene-type epoxy resin (e.g., bisarylfluorene-type epoxy resin), triphenylmethane-type epoxy resin (e.g., trishydroxyphenylmethane-type epoxy resin), and dicyclopentadiene-type epoxy resin.

[0037] The conductive composition preferably contains at least one epoxy resin selected from the group consisting of dicyclopentadiene-type epoxy resins, biphenyl-type epoxy resins, and naphthalene-type epoxy resins, and is particularly preferably a dicyclopentadiene-type epoxy resin. However, the conductive composition may also contain other epoxy resins (for example, bisphenol A-type epoxy resins, cresol novolac-type epoxy resins, phenol novolac-type epoxy resins, etc.).

[0038] Commercially available dicyclopentadiene-type epoxy resins include "EPICLON HP-7200HHH" from DIC Corporation and "XD-1000" from Nippon Kayaku Co., Ltd. Commercially available biphenyl-type epoxy resins include "NC-3000" and "NC-3500" from Nippon Kayaku Co., Ltd. Commercially available naphthalene-type epoxy resins include "NC-7000H" from Nippon Kayaku Co., Ltd. Commercially available bisphenol-type epoxy resins include "jER828" from Mitsubishi Chemical Corporation and "NPES907" from Nanya Plastics Co., Ltd. Commercially available cresol novolac-type epoxy resins include "EOCN-1020-70" from Nippon Kayaku Co., Ltd. Commercially available phenol novolac-type epoxy resins include "EPPN-502H" from Nippon Kayaku Co., Ltd.

[0039] The weight average molecular weight of the epoxy resin is, for example, less than 10,000, and may be 9,000 or less, 8,000 or less, 7,000 or less, 6,000 or less, 5,000 or less, or even 4,000 or less. The above-mentioned weight average molecular weight is, for example, 100 or more, and may be 300 or more, 500 or more, 800 or more, or even 1,000 or more. The weight average molecular weight can be measured by GPC (gel permeation chromatography).

[0040] The curing temperature of the epoxy resin is, for example, 150°C to 280°C, and may be 160°C to 260°C, or even 170°C to 250°C. When the conductive particles are solder particles, the curing temperature of the epoxy resin is preferably not lower than the melting point T0 of the solder particles.

[0041] It should be noted that in the conductive composition, the epoxy resin may be either liquid or solid. The conductive composition of the present embodiment preferably contains both a liquid epoxy resin and a solid epoxy resin. However, the conductive composition may contain only one of the liquid epoxy resin and the solid epoxy resin (for example, only the solid epoxy resin). In the present specification, "liquid" means a substance in a liquid state that is flowable at 25°C under atmospheric pressure (101.325 kPa), and "solid" means a substance in a solid state that does not flow at 25°C under atmospheric pressure.

[0042] The softening point of the solid epoxy resin is, for example, 40°C or higher, and may be 60°C or higher, or even 80°C or higher. The above-mentioned softening point is, for example, 200°C or lower, and may be 180°C or lower, 150°C or lower, or even 140°C or lower. When the conductive particles are solder particles, the softening point is preferably lower than the melting point T0 of the solder particles. The softening point can be measured by a thermomechanical analyzer.

[0043] The content of the epoxy resin in the conductive composition is, for example, 10% by weight or more, and may be 20% by weight or more, 25% by weight or more, or even 30% by weight or more. The above-mentioned content is, for example, 60% by weight or less, and may be 50% by weight or less, or even 40% by weight or less.

[0044] The content ratio R1 of solid epoxy resin among the resins contained in the conductive composition is, for example, 40% by weight or more, and may be 50% by weight or more, 60% by weight or more, 65% by weight or more, or even 70% by weight or more. The content ratio R1 is, for example, 95% by weight or less, and may be 90% by weight or less, 85% by weight or less, or even 80% by weight or less. By appropriately adjusting the content ratio R1, the storage elastic modulus E described above tends to be adjusted to a high value.

[0045] (1-2-b. Polymer Resin) The conductive composition preferably contains a polymer resin having a weight average molecular weight of 10,000 or more. The polymer resin is suitable for adjusting the complex viscosity of the conductive composition to an appropriate value. The polymer resin may be used alone, or two or more kinds thereof may be used.

[0046] Examples of the polymer resin include epoxy resins and (meth)acrylic resins having a weight average molecular weight of 10,000 or more. Epoxy resins having a weight average molecular weight of 10,000 or more are sometimes referred to as phenoxy resins.

[0047] The epoxy resin as the polymer resin may be thermosetting or thermoplastic. A thermosetting epoxy resin typically has at least one epoxy group (particularly a glycidyl group) per molecule. In this case, the epoxy equivalent of the epoxy resin is, for example, 3000 g / eq. or more, 5000 g / eq. or more, or even 8000 g / eq. or more. The epoxy equivalent described above is, for example, 50000 g / eq. or less, and may be 10000 g / eq. or less.

[0048] Specific examples of the epoxy resin include those exemplified in the section of (1-2-a. Epoxy Resin). The epoxy resin as the polymer resin is preferably a bisphenol-type epoxy resin (particularly a bisphenol A-type epoxy resin or a bisphenol F-type epoxy resin). Commercially available products of the bisphenol-type epoxy resin as the polymer resin include the products under the trade names "jER1256" and "jER4250" manufactured by Mitsubishi Chemical Corporation.

[0049] The (meth)acrylic resin used as the polymer resin is preferably thermoplastic. Examples of commercially available (meth)acrylic resins include "Teisan Resin SG-70L" manufactured by Nagase ChemteX Corporation and "ARUFON UH-2170" manufactured by Toagosei Co., Ltd.

[0050] The weight-average molecular weight of the polymer resin is 10,000 or more, as described above, but may be 20,000 or more, 30,000 or more, or even 40,000 or more. The above weight-average molecular weight may be, for example, 2 million or less, but may be 1 million or less, 500,000 or less, 300,000 or less, or even 100,000 or less.

[0051] The polymer resin may be thermosetting or thermoplastic. If the polymer resin is thermosetting, the curing temperature of the polymer resin may be, for example, 120°C to 280°C, 160°C to 260°C, or even 170°C to 250°C. If the conductive particles are solder particles, the curing temperature of the polymer resin is preferably above the melting point T0 of the solder particles.

[0052] In the conductive composition, the polymer resin may be liquid, but it is preferably solid. When the conductive particles are solder particles, the glass transition temperature of the solid polymer resin is preferably lower than the melting point T0 of the solder particles. The glass transition temperature is, for example, 50°C to 150°C, and may also be 80°C to 120°C.

[0053] The content of polymer resin in the conductive composition is, for example, 0.1% by weight or more, and may be 0.5% by weight or more, 1.0% by weight or more, 2.0% by weight or more, and even 3.0% by weight or more. The above content is, for example, 20% by weight or less, and may be 15% by weight or less, 10% by weight or less, and even 5.0% by weight or less.

[0054] The content ratio R2 of the polymer resin in the resin contained in the conductive composition is, for example, 30% by weight or less, and may be 25% by weight or less, 20% by weight or less, 15% by weight or less, or even 10% by weight or less. The content ratio R2 is, for example, 0.1% by weight or more, and may be 0.5% by weight or more, 1.0% by weight or more, 5.0% by weight or more, or even 8.0% by weight or more. By appropriately adjusting the content ratio R2, it tends to be possible to adjust the above storage modulus E to a high value.

[0055] (1-2-c. Other Resins) The conductive composition may contain other resins besides those described above. Examples of other resins include urea resin, melamine resin, diallyl phthalate resin, silicone resin, polyester resin (e.g., polyethylene terephthalate), polyimide resin, polyurethane resin, polyolefin (e.g., polyethylene, polypropylene, ethylene-propylene copolymer), polyvinyl acetate, ethylene-vinyl acetate copolymer, polyvinyl chloride, polystyrene, polyacrylonitrile, polyamide, polycarbonate, polyacetal, polyphenylene oxide, polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone, polyallylsulfone, polyaminobismaleimide, polyamideimide, polyetherimide, bismaleimide triazine resin, polymethylpentene, fluorinated resin, liquid crystal polymer, olefin-vinyl alcohol copolymer, ionomer, polyarylate, acrylonitrile-ethylene-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene copolymer, butadiene-styrene copolymer, and the like.

[0056] The content of other resins in the conductive composition may be, for example, 10% by weight or less, 5% by weight or less, 1% by weight or less, or even 0.1% by weight or less. The conductive composition may be substantially free of other resins.

[0057] <1-3. Flux> The conductive composition preferably further contains flux. Flux tends to remove oxide films that may be present on the surface of conductive particles. Flux also tends to remove oxide films that may be present on the surface of electrodes that the conductive composition contacts when the conductive composition is used to connect two wiring circuit boards. There may be only one type of flux or two or more types.

[0058] The flux is preferably an organic acid, and more preferably a carboxylic acid compound. Examples of carboxylic acid compounds include monocarboxylic acid compounds, dicarboxylic acid compounds, and tricarboxylic acid compounds, with dicarboxylic acid compounds being preferred.

[0059] Examples of monocarboxylic acid compounds include aliphatic monocarboxylic acids and aromatic monocarboxylic acids. Examples of aromatic monocarboxylic acids include 2-phenoxybenzoic acid.

[0060] Examples of dicarboxylic acid compounds include aliphatic dicarboxylic acids and aromatic dicarboxylic acids. Aliphatic dicarboxylic acids include linear saturated dicarboxylic acids, branched saturated dicarboxylic acids, linear unsaturated dicarboxylic acids, and branched unsaturated dicarboxylic acids.

[0061] Examples of linear saturated dicarboxylic acids include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. Examples of branched saturated dicarboxylic acids include 3,3-dimethylglutaric acid and 3-methyladipic acid. Examples of linear unsaturated dicarboxylic acids include fumaric acid.

[0062] Examples of tricarboxylic acid compounds include 1,3,5-pentanetricarboxylic acid and tricarbaryl acid.

[0063] From the viewpoint of improving connection reliability, the flux is preferably an aliphatic dicarboxylic acid (especially a linear saturated dicarboxylic acid or a branched saturated dicarboxylic acid), more preferably glutaric acid, adipic acid, pimelic acid, 3-methyladipic acid, or 3,3-dimethylglutaric acid, and particularly preferably 3,3-dimethylglutaric acid.

[0064] The flux may also be a salt of an organic acid (especially a dicarboxylic acid compound).

[0065] The flux content in the conductive composition is, for example, 1% to 10% by weight, and may also be 3% to 7% by weight.

[0066] The flux content in the conductive composition is, for example, 1 part by weight or more, and may be 5 parts by weight or more, per 100 parts by weight of conductive particles. The above content is, for example, 20 parts by weight or less, and may be 10 parts by weight or less, per 100 parts by weight of conductive particles.

[0067] <1-4. Curing Agent> The conductive composition may further contain a curing agent. The curing agent can react with a resin component, such as epoxy resin, to accelerate its curing. There may be only one type of curing agent, or two or more types.

[0068] Examples of curing agents include acid anhydride-based curing agents, amine-based curing agents, phenol-based curing agents, cationic initiators, imidazole catalysts, and DICY (dicyandiamide).

[0069] The amount of curing agent in the conductive composition is, for example, less than 20 parts by weight per 100 parts by weight of the resin component, and may be less than 10 parts by weight, less than 5 parts by weight, less than 3 parts by weight, or even less than 1 part by weight. The conductive composition does not need to contain a curing agent.

[0070] <1-5. Other Additives> The conductive composition may further contain other additives in addition to the components described above. Other additives include solvents and curing aids. Examples of solvents include organic solvents such as methyl ethyl ketone.

[0071] The content of other additives in the conductive composition may be, for example, 10% by weight or less, 5% by weight or less, 1% by weight or less, or even 0.1% by weight or less. The conductive composition may be substantially free of other additives. If the conductive composition contains a solvent, the solid content concentration of the conductive composition may be, for example, 50% by weight to 80% by weight, or 60% by weight to 75% by weight.

[0072] <1-6. Method for Producing Conductive Compositions> Conductive compositions according to embodiments of the present invention can be prepared, for example, by stirring and mixing the conductive particles, resin, and, if necessary, a solvent as described above. After preparing the conductive composition, the solvent may be removed from the conductive composition by heat treatment or the like.

[0073] Before preparing the conductive composition, any oxide film formed on the surface of the conductive particles may be removed beforehand. The oxide film can be removed, for example, by acid treatment, in which the conductive particles are brought into contact with an acid treatment agent. The acid treatment agent may be one type or two or more types.

[0074] The acid treatment agent is preferably a carboxylic acid treatment agent having a carboxyl group. Examples of carboxylic acid treatment agents include monocarboxylic acid treatment agents, dicarboxylic acid treatment agents, and trifunctional or more carboxylic acid treatment agents, with dicarboxylic acid treatment agents being preferred. The dicarboxylic acid treatment agent is preferably an aliphatic dicarboxylic acid treatment agent, and is particularly preferably malic acid.

[0075] <1-7. Physical Properties of Conductive Compositions> It is preferable that the conductive composition has a peel force of 0.30 N / 20 mm or more, as determined by the following test. Test: A conductive sheet (20 μm thick) made of the conductive composition is prepared on a polyethylene terephthalate support substrate, and then cut into strips measuring 50 mm in length and 20 mm in width to make test pieces. The test pieces are attached to a stainless steel plate (SUS304 plate) via the conductive sheet, and a pressure of 0.3 MPa is applied for 2 seconds at a temperature of 80°C. The test pieces are peeled off the stainless steel plate under conditions of 23°C, 50% RH atmosphere, peel speed of 3000 mm / min, and peel angle of 180°. The maximum force required at this time is identified as the peel force.

[0076] The peeling force described above can be determined in detail by the following method. First, the conductive composition is applied to a polyethylene terephthalate (PET) support substrate using an applicator to form a coating film. A biaxially oriented PET film (for example, "Lumirror S10" manufactured by Toray Industries, Inc., with a thickness of 50 μm) can be used as the support substrate. Next, the coating film is dried to obtain a laminate of a dry conductive sheet (thickness of 20 μm) and the support substrate. The drying of the coating film may be carried out, for example, at 60°C for 5 minutes.

[0077] Next, the laminate is cut into strips measuring 50 mm in length and 20 mm in width to form test specimens. It is preferable that the length of the test specimen aligns with the TD direction of the conductive sheet. Then, the test specimen is bonded to a stainless steel plate (SUS304 plate) via the conductive sheet, and a pressure of 0.3 MPa is applied for 2 seconds at a temperature of 80°C. This operation can be performed using a commercially available vacuum bonding device.

[0078] Next, the test specimen is allowed to cool to room temperature (23°C), and then, using a tensile testing machine, it is peeled from the stainless steel plate under the conditions of 23°C, 50% RH atmosphere, peeling speed of 3000 mm / min, and peeling angle of 180°. The maximum force required to peel the test specimen from the stainless steel plate (peel strength) is identified as the peeling force.

[0079] As described above, the peeling force is preferably 0.30 N / 20 mm or more, but may be 0.35 N / 20 mm or more, 0.40 N / 20 mm or more, 0.50 N / 20 mm or more, 0.60 N / 20 mm or more, and even 0.70 N / 20 mm or more. The upper limit of the peeling force is not particularly limited and may be, for example, 3.0 N / 20 mm or less, 2.0 N / 20 mm or less, and even 1.0 N / 20 mm or less.

[0080] Furthermore, if the conductive particles are solder particles, it is preferable that the conductive composition has a minimum complex viscosity V1 of 10 Pa·s or less, as determined by the following test. Test: The conductive composition, excluding the solder particles, is heated from 25°C to a temperature 30°C higher than the melting point T0 of the solder particles (T0 + 30°C) at a heating rate of 10°C / min. The complex viscosity of the conductive composition, excluding the solder particles, is measured from 25°C to the temperature (T0 + 30°C), and its minimum value is identified.

[0081] The minimum value V1 of the complex viscosity can be measured in detail by the following method. First, a measurement sample S2 is prepared, which is made of a conductive composition from which solder particles have been removed. Note that the conductive composition from which solder particles have been removed is simply a resin composition and does not strictly exhibit conductivity, but for convenience, it is referred to as a "conductive composition" in this specification. The measurement sample S2 is disc-shaped, with a base diameter of 25.0 mm and a thickness of 500 ± 50 μm. It is preferable that the measurement sample S2 is in a dry state. The measurement sample S2 may also be a disc-shaped cutout of a laminate of multiple conductive sheets made using the conductive composition from which solder particles have been removed. Next, dynamic viscoelasticity measurement is performed on the measurement sample S2 under the following measurement conditions. Measurement conditions Measurement environment: atmospheric atmosphere Strain value: 0.5% Measurement frequency: 1 Hz Temperature range: 25°C to 300°C Heating rate: 10°C / min Shape: parallel plate 25.0 mmφ

[0082] From the results of the dynamic viscoelasticity measurements described above, a temperature-complex viscosity profile (e.g., Figure 1) is created. Based on this profile, the minimum value V1 of the complex viscosity can be identified in the range from 25°C to a temperature 30°C higher than the melting point T0 of the solder particles (T0 + 30°C).

[0083] Figure 1 is a graph illustrating the relationship between temperature and complex viscosity for a conductive composition excluding solder particles (i.e., the measurement sample S2 described above). This graph schematically shows the relationship between temperature and complex viscosity and does not limit the physical properties of the conductive composition. As can be seen from the graph in Figure 1, when the measurement sample S2 is heated and its temperature rises, it is preferable that the complex viscosity gradually decreases. At temperature T1, the complex viscosity reaches its minimum value V1. Furthermore, when the measurement sample S2 is heated to a temperature higher than T1, it is preferable that its complex viscosity increases.

[0084] The minimum value V1 of the complex viscosity is preferably 10 Pa·s or less, as described above, but may also be 5.0 Pa·s or less, 3.0 Pa·s or less, 2.0 Pa·s or less, 1.0 Pa·s or less, or even 0.5 Pa·s or less. The smaller the minimum value V1, the easier it is for solder particles (or molten solder) to move through the conductive composition. Therefore, when a conductive composition is used to connect two wiring circuit boards, for example, solder is more likely to aggregate between the electrodes of one wiring circuit board and the electrodes of the other wiring circuit board, thereby obtaining a connection structure with high electrical reliability. The lower limit of the minimum value V1 is, for example, 0.01 Pa·s or more, and may also be 0.03 Pa·s or more.

[0085] Furthermore, the temperature T1 at which the complex viscosity reaches its minimum value V1 is preferably lower than the melting point T0 of the solder particles. Also, the difference between temperature T1 and the melting point T0 |T1-T0| is, for example, 0°C to 50°C, and may be 5°C to 30°C.

[0086] ≪2. Conductive Sheet≫ The conductive sheet according to the embodiment of the present invention is composed of the conductive composition described above. More specifically, the conductive sheet has the same composition as the conductive composition, except that it does not contain a solvent (or has a low solvent content). However, the conductive sheet may contain a small amount of solvent derived from the conductive composition. When the conductive composition contains a thermosetting resin, the thermosetting resin is typically present in an uncured state in the conductive sheet. The conductive sheet of this embodiment can typically function as an anisotropic conductive sheet.

[0087] <2-1. Structure of the Conductive Sheet> An example of a conductive sheet according to an embodiment of the present invention is shown in Figure 2. Figure 2 shows the conductive sheet 1 placed on the release liner 15. Another aspect of the present invention is to provide a laminate 150 comprising the conductive sheet 1 and the release liner 15. When the conductive sheet 1 is used, the release liner 15 is peeled off from the conductive sheet 1.

[0088] As shown in Figure 2, the conductive sheet 1 has, for example, a matrix 3 and conductive particles 5 dispersed in the matrix 3. More specifically, the matrix 3 surrounds the conductive particles 5. In the matrix 3, the conductive particles 5 may be spaced apart from each other or partially aggregated. In this embodiment, it is preferable that the matrix 3 contains the above-mentioned resin.

[0089] As the release liner 15, the release liner described in section 2-2, "Method for Manufacturing Conductive Sheets," can be used. In the example shown in Figure 2, the conductive sheet 1 is placed on one release liner 15. However, the conductive sheet 1 may be placed between two release liners 15.

[0090] <2-2. Method for Manufacturing a Conductive Sheet> A conductive sheet according to an embodiment of the present invention can be manufactured, for example, by the following method. First, the above-mentioned conductive composition is prepared. Next, the conductive composition is applied to a release liner to form a coating film. A conductive sheet can be formed by drying the coating film. The drying conditions for the coating film are not particularly limited, and for example, the drying temperature is 40°C to 100°C and the drying time is 1 minute to 60 minutes.

[0091] Known materials can be used as the release liner. Examples of the base material for the release liner (hereinafter referred to as "liner base material") include resin films. Examples of resins that make up the resin film include polyester such as polyethylene terephthalate, acetate resin, polyethersulfone, polycarbonate, polyamide, polyimide, polyolefin, (meth)acrylic resin, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl alcohol, polyarylate, and polyphenylene sulfide. Preferably, the resin that makes up the resin film is polyester such as polyethylene terephthalate. The thickness of the release liner is, for example, 1 μm to 100 μm.

[0092] The peel-off liner may include layers other than the liner substrate. The peel-off liner may include a release layer. For example, the peel-off liner includes a liner substrate and a release layer formed on one side of the liner substrate. In the peel-off liner, the release layer may be on the side of the coating film.

[0093] <2-3. Physical Properties of Conductive Sheets> The thickness of the conductive sheet is, for example, 50 μm or less, and may be 25 μm or less, 15 μm or less, or even 10 μm or less. The thickness of the conductive sheet is, for example, 1 μm or more.

[0094] ≪3. Connection Structure≫ <3-1. Configuration of the Connection Structure> An example of a connection structure according to an embodiment of the present invention is shown in Figure 3. The connection structure 100 shown in Figure 3 comprises a first substrate 20, a second substrate 30, and a connecting member 10. A first electrode 21 is arranged on the first substrate 20, and a second electrode 31 is arranged on the second substrate 30. The connecting member 10 is formed from the conductive composition described above and connects the first substrate 20 and the second substrate 30. The first substrate 20, the connecting member 10, and the second substrate 30 are arranged in this order in the stacking direction Y.

[0095] The first substrate 20 is typically a wiring circuit board. The first substrate 20 has, for example, a flat plate shape and a pair of main surfaces (the surfaces of the first substrate 20 that have the largest surface area). Of the pair of main surfaces, the first electrode 21 is arranged on the main surface facing the connecting member 10.

[0096] Examples of materials for the first substrate 20 include insulating materials and semiconductor materials. The thickness of the first substrate 20 is, for example, 5 μm to 1000 μm.

[0097] The first electrodes 21 are arranged in a pattern on the first substrate 20, for example. For example, the first electrodes 21 may be arranged in a dot pattern. In this case, the shape of the first electrodes 21 is typically columnar (such as cylindrical or prismatic). In this embodiment, a plurality of columnar first electrodes 21 may be arranged in an evenly aligned plane direction X perpendicular to the stacking direction Y. Figure 3 shows an example in which two first electrodes 21 are arranged on the first substrate 20.

[0098] Examples of materials for the first electrode 21 include metals such as gold, copper, and nickel.

[0099] The thickness of the first electrode 21 is, for example, 0 μm to 20 μm, and may be 0.001 μm to 5 μm. At least a portion of the first electrode 21 may be embedded in the first substrate 20. In this case, the thickness of the portion of the first electrode 21 that protrudes from the first substrate 20 is considered to be the thickness of the first electrode 21. That is, if the first electrode 21 does not protrude from the first substrate 20 and the surface of the first electrode 21 coincides with the surface of the first substrate 20, the thickness of the first electrode 21 is 0 μm.

[0100] When the first electrode 21 is cylindrical, the diameter of the first electrode 21 in plan view is, for example, 1 μm to 200 μm, and may be 1 μm to 100 μm, 1 μm to 50 μm, or even 1 μm to 20 μm.

[0101] The distance (pitch) between two adjacent first electrodes 21 in the planar direction X is, for example, 3 μm to 400 μm, and may be 5 μm to 200 μm, 7 μm to 100 μm, or even 10 μm to 40 μm.

[0102] The second substrate 30 is typically a wiring circuit board. However, the second substrate 30 may also be a chip component such as a mini / micro LED. The second substrate 30 has, for example, a flat plate shape and a pair of main surfaces. The second electrode 31 is placed on the main surface of the pair of main surfaces that faces the connecting member 10.

[0103] The material and thickness of the second substrate 30 are as described above for the first substrate 20.

[0104] The second electrodes 31 are arranged in a pattern on the second substrate 30, for example. For example, the second electrodes 31 may be arranged in a dot pattern. In this case, the shape of the second electrodes 31 is typically columnar (such as cylindrical or prismatic). In this embodiment, a plurality of columnar second electrodes 31 may be arranged evenly aligned in the planar direction X. Figure 3 shows an example in which two second electrodes 31 are arranged on the second substrate 30.

[0105] The material and dimensions, such as thickness, of the second electrode 31 are as described above for the first electrode 21.

[0106] Preferably, the distance (pitch) between two adjacent second electrodes 31 in the planar direction X is the same as the distance (pitch) between two adjacent first electrodes 21 in the planar direction X. In other words, it is preferable that the second electrodes 31 face the first electrodes 21, and that these electrodes 21 and 31 are aligned along the stacking direction Y. More specifically, it is preferable that the second electrodes 31 overlap the first electrodes 21 in a plan view.

[0107] The connecting member 10 has a conductive portion 6 and an insulating portion 7. The conductive portion 6 is in direct contact with the first electrode 21 arranged on the first substrate 20 and the second electrode 31 arranged on the second substrate 30, and electrically connects them. The conductive portion 6 makes it possible to exhibit conductivity in the stacking direction Y.

[0108] It is preferable that the conductive portion 6 overlaps the first electrode 21 and the second electrode 31 in a plan view. If the first electrode 21 and the second electrode 31 are arranged in a pattern, it is preferable that the conductive portion 6 is also arranged in a pattern. For example, the conductive portion 6 may be arranged in a dot pattern. In this case, the shape of the conductive portion 6 is typically columnar (such as cylindrical or prismatic). In this embodiment, a plurality of columnar conductive portions 6 may be arranged evenly aligned in the planar direction X. Figure 3 shows an example in which two conductive portions 6 are arranged within the connecting member 10.

[0109] The conductive portion 6 is formed by the aggregation of conductive particles. Therefore, the conductive portion 6 typically contains a material derived from the conductive particles. If the conductive particles are solder particles, the conductive portion 6 may be formed by the melting and aggregation of the solder particles.

[0110] The insulating portion 7 surrounds the conductive portion 6 and fills the space between the first substrate 20 and the second substrate 30 where the conductive portion 6 is not present. The insulating portion 7 is in direct contact with the surface of the first substrate 20 where the first electrode 21 is not placed, and with the surface of the second substrate 30 where the second electrode 31 is not placed. The insulating portion 7 can function as an adhesive portion that adheres to the first substrate 20 and the second substrate 30, respectively. The insulating portion 7 ensures insulation in the plane direction X.

[0111] The insulating portion 7 is formed by the curing of a resin such as epoxy resin, as described later. Typically, the insulating portion 7 includes a material derived from the matrix of the conductive sheet.

[0112] The thickness of the connecting member 10 is, for example, 50 μm or less, and may be 25 μm or less, 15 μm or less, or even 5 μm or less. The thickness of the connecting member 10 is, for example, 1 μm or more.

[0113] <3-2. Method for Manufacturing a Connecting Structure> A method for manufacturing a connecting structure 100 according to an embodiment of the present invention includes, for example, placing a conductive composition (typically a conductive sheet 1 composed of the conductive composition) between a first substrate 20 and a second substrate 30, and heating the conductive composition to form a connecting member 10.

[0114] The connecting structure 100 can be manufactured in detail by the following method. First, as shown in Figure 4A, a conductive sheet 1 made of a conductive composition is placed between the first substrate 20 and the second substrate 30. At this time, it is preferable that the conductive sheet 1 is in contact with both the first electrode 21 and the second electrode 31.

[0115] Next, the conductive sheet 1 is heated. The conductive sheet 1 is typically heated by the following first heating. If the conductive particles 5 are solder particles, it is preferable to heat the conductive sheet 1 by first heating and second heating. In the first heating, the conductive sheet 1 is heated to a temperature above the softening point of the resin in the conductive sheet 1 (for example, solid epoxy resin or solid polymer resin). If the conductive particles 5 are solder particles, it is preferable that the temperature of the first heating is below the melting point T0 of the solder particles. As a result of the first heating, the conductive sheet 1 softens and the first electrode 21 and the second electrode 31 each become embedded in the conductive sheet 1 (Figure 4B). As a result, the first electrode 21 and the second electrode 31 each become embedded in the conductive sheet 1. The conductive sheet 1 comes into contact with the surface of the first substrate 20 where the first electrode 21 is not placed and the surface of the second substrate 30 where the second electrode 31 is not placed.

[0116] The heating temperature in the first heating stage is, for example, 180°C or lower, and may be 100°C or lower, 80°C or lower, or even 70°C or lower. The above heating temperature is, for example, 40°C or higher.

[0117] In the first heating stage, pressure may be applied to the laminate of the first substrate 20, the conductive sheet 1, and the second substrate 30 in the stacking direction Y to cause them to be pressed together (thermocompressed). The pressure applied to the laminate in the first heating stage may be, for example, 0.001 MPa to 10 MPa, 0.005 MPa to 5 MPa, or even 0.01 MPa to 1 MPa.

[0118] As described above, if the conductive particles 5 are solder particles, it is preferable to perform a second heating on the conductive sheet 1. The second heating is typically performed after the first heating. In the second heating, the conductive sheet 1 is heated to a temperature above the melting point T0 of the conductive particles (solder particles) 5. Due to the second heating, the conductive particles (solder particles) 5 in the conductive sheet 1 melt and aggregate (self-aggregate) between the first electrode 21 and the second electrode 31. This forms a conductive portion 6 that electrically connects the first electrode 21 and the second electrode 31. At this time, the resin constituting the matrix 3 of the conductive sheet 1 hardens while surrounding the conductive portion 6, thereby forming an insulating portion 7. In this way, the connecting member 10 is formed from the conductive sheet 1 by the first and second heating, and a connecting structure 100 (Figure 3) can be obtained. Note that if the conductive particles 5 are not solder particles, the above second heating is not necessarily required.

[0119] The heating temperature for the second heating step is, for example, 70°C or higher, and may be 100°C or higher, 120°C or higher, 130°C or higher, 150°C or higher, or even 200°C or higher. The above heating temperature is, for example, 300°C or lower, and may be 280°C or lower, or even 270°C or lower.

[0120] The second heating step may be performed using a pressure oven. A pressure oven allows the conductive sheet 1 to be heated under pressure in a sealed space. This tends to suppress the volatilization of some of the components of the conductive sheet 1 and the generation of voids. Examples of pressure ovens include automatic heating and pressurizing equipment, pressurizing ovens, voidless pressurizing ovens, autoclaves, and vacuum pressurizing reflow apparatus.

[0121] The present invention will be specifically described below with reference to examples, but the present invention is not limited in any way to these examples. Where "parts" is mentioned, it means "parts by weight" unless otherwise specified, and where "%" is mentioned, it means "percent by weight" unless otherwise specified.

[0122] (Example 1) First, a varnish (solid content concentration 60% by weight) was prepared by dissolving a dicyclopentadiene type epoxy resin (DIC Corporation, trade name "EPICLON HP-7200HHH", epoxy equivalent 280-292 g / eq, solid (25°C)) as a solid epoxy resin in methyl ethyl ketone.

[0123] Next, solder particles (manufactured by DUKSAN Hi-Metal, product name "Aurora SAC305") 200 parts by weight of EN (0-3 μm), Sn 96.5% by weight, Ag 3.0% by weight, Cu 0.5% by weight, melting point 218°C, spherical shape, average primary particle diameter 1 μm), 20 parts by weight of bisphenol A type epoxy resin as a liquid epoxy resin (manufactured by Mitsubishi Chemical Corporation, trade name "jER828", epoxy equivalent 184-194 g / eq, liquid (25°C)), 70 parts by weight of the above varnish as a solid epoxy resin (calculated on a solid content basis), 10 parts by weight of varnish (calculated on a solid content basis) obtained by dissolving bisphenol A type epoxy resin (weight-average molecular weight 45000, epoxy equivalent 8500 g / eq, solid (25°C)) in methyl ethyl ketone (manufactured by Mitsubishi Chemical Corporation, trade name "jER1256B40", solid content concentration 40% by weight), and 3,3-dimethylglutaric acid as a flux (Changzhou Liren Medical The conductive composition of Example 1 was obtained by mixing 15 parts by weight of (manufactured by Technology Inc.) with methyl ethyl ketone, which is a diluent, so that the solid content was 40% by volume, and stirring.

[0124] (Examples 2-13 and Comparative Examples 1-3) Conductive compositions of Examples 2-13 and Comparative Examples 1-3 were obtained by the same method as in Example 1, except that the types and contents of the materials used were changed as shown in Tables 1-3. In Examples 2-13 and Comparative Examples 1-3, solid epoxy resins, polymer resins, fluxes, etc., were dissolved in a solvent such as methyl ethyl ketone beforehand as needed to prepare a varnish, and the varnish was mixed with other materials to prepare the conductive composition. Solder particles were used as conductive particles in all of these examples and comparative examples.

[0125] <Measurement of Storage Modulus> The storage modulus E at 50°C was measured for the conductive compositions of the examples and comparative examples by the following method. First, the conductive composition was applied to a release liner (Mitsubishi Chemical Corporation, product name "MRA50" (thickness 50 μm)) using an applicator to form a coating film. Multiple conductive sheets with a thickness of 50 μm were prepared by drying the coating film at 80°C for 5 minutes. Multiple conductive sheets were laminated to create a laminate with a thickness of 500 ± 50 μm, and a measurement sample S1 with a bottom diameter of 25.0 mm was obtained by punching out this laminate into a disc shape. This measurement sample S1 was set in a rheometer (Anton Paar, product name "MCR302e"), and dynamic viscoelasticity measurement was performed under the following measurement conditions. From the results of the dynamic viscoelasticity measurement, the storage modulus of measurement sample S1 at 50°C was determined, and the obtained value was considered to be the storage modulus E of the conductive composition. Measurement conditions: Measurement environment: atmospheric atmosphere; Strain value: 0.5%; Measurement frequency: 1 Hz; Temperature range: 25°C to 300°C; Heating rate: 10°C / min; Shape: Parallel plate, 25.0 mm diameter

[0126] <Measurement of Peel Force> The peel force of the conductive compositions of the examples and comparative examples was measured by the following method. First, the conductive composition was applied to a biaxially oriented PET film (product name "Lumirror S10" manufactured by Toray Industries, Inc., 50 μm thick) using an applicator to form a coating film. By drying the coating film at 60°C for 5 minutes, a laminate of a 20 μm thick conductive sheet and a support substrate was prepared.

[0127] Next, this laminate was cut into strips measuring 50 mm in length and 20 mm in width to form test specimens. At this time, the length direction of the test specimens was aligned with the TD direction of the conductive sheet. Next, the test specimens were bonded to a stainless steel plate (SUS304 plate, manufactured by Nippon Test Panel Co., Ltd.) via the conductive sheet, and a pressure of 0.3 MPa was applied for 2 seconds at a temperature of 80°C. This operation was performed using a vacuum bonding device (V-SE340naaH, manufactured by Climb Products Co., Ltd.).

[0128] Next, the test specimen was allowed to cool to room temperature (23°C), and then, using a tensile testing machine (Shimadzu Corporation, Autograph AGX-V2), the specimen was peeled from the stainless steel plate under conditions of 23°C, 50% RH atmosphere, peeling speed of 3000 mm / min, and peeling angle of 180°. At this time, the maximum force required to peel the test specimen from the stainless steel plate (peel strength) was identified as the peeling force.

[0129] <Measurement of Minimum Complex Viscosity> For the examples and comparative examples, the minimum complex viscosity V1 was measured using conductive compositions from which solder particles had been removed, by the following method. First, conductive compositions were prepared in the same manner as in each example and comparative example, except that solder particles were not included. This conductive composition was applied to a release liner (Mitsubishi Chemical Corporation, product name "MRA50" (thickness 50 μm)) to form a coating film. Multiple conductive sheets with a thickness of 50 μm were prepared by drying the coating film at 80°C for 5 minutes. Multiple conductive sheets were laminated to create a laminate with a thickness of 500 ± 50 μm, and a measurement sample S2 with a bottom diameter of 25.0 mm was obtained by punching out this laminate into a disc shape. This measurement sample S2 was set in a rheometer (Anton Paar, product name "MCR302e"), and dynamic viscoelasticity measurement was performed under the same measurement conditions as for the storage modulus E. Based on the results of dynamic viscoelasticity measurements, a temperature-complex viscosity profile was created, and based on this profile, the minimum value V1 of the complex viscosity was identified in the range from 25°C to a temperature 30°C higher than the melting point T0 of the solder particles (T0 + 30°C).

[0130] <Adhesion Test> The adhesive properties (temporary adhesion) of the conductive compositions of the examples and comparative examples were evaluated by the following method. First, the conductive composition was applied to a release liner (Mitsubishi Chemical Corporation, product name "MRA50" (thickness 50 μm)) using an applicator to form a coating film. A conductive sheet was prepared by drying the coating film at 60°C for 5 minutes. Considering the average primary particle size of the solder particles used, the thickness of the conductive sheet was adjusted to 5 μm in Examples 1 to 10 and Comparative Examples 1 to 2, and to 20 μm in Examples 11 to 13 and Comparative Example 3.

[0131] Next, a wafer (10 mm long x 10 mm wide, 50 μm thick) was prepared and bonded to a die attach film (DAF, manufactured by Nitto Denko Corporation, product name "Elepmount EM-350", 20 μm thick), and heated at 170°C for 1 hour. As a result, the wafer and die attach film laminate warped, with the die attach film side becoming concave.

[0132] Next, the release liner was peeled off the fabricated conductive sheet, and the conductive sheet was placed on top of the wafer-side surface of the laminate. In this state, it was set in a vacuum bonding apparatus and a pressure of 0.3 MPa was applied for 2 seconds at a temperature of 65°C. Furthermore, alkali-free glass (15 mm long x 15 mm wide, 0.3 mm thick) was placed on the exposed surface of the conductive sheet, set in the vacuum bonding apparatus, and a pressure of 0.3 MPa was applied for 2 seconds at a temperature of 65°C. This created a test chip in which the die attach film, wafer, conductive sheet, and alkali-free glass were laminated in this order. The test chip was observed with an optical microscope (digital microscope, manufactured by Keyence Corporation, product name "VHX-8000") to confirm that there were no trapped air bubbles.

[0133] Next, the test chips were placed on a hot plate set to 50°C for 60 seconds. After heating, the test chips were observed from the alkali-free glass side using an optical microscope (digital microscope, manufactured by Keyence Corporation, product name "VHX-8000"). The observation of the test chips was performed under conditions of 200x magnification. The peeling of the conductive sheet on the test chips was observed and evaluated based on the following criteria: Evaluation Criteria 2: Peeling of less than 100 μm in length is observed from the end face of the test chip toward the inside, or no peeling is observed. 1: Peeling of 100 μm or more but less than 500 μm in length is observed from the end face of the test chip toward the inside. 0: Peeling of 500 μm or more in length is observed from the end face of the test chip toward the inside.

[0134] <Integration Test> Using the conductive compositions of the examples and comparative examples, connection structures were fabricated by the following method, and the solder integration was evaluated. Solder integration is an indicator of the reliability of the electrical connection in the connection structure.

[0135] (Preparation of connecting structures) First, conductive sheets were prepared from the conductive compositions of the examples and comparative examples using the method described above for adhesion testing. Considering the average primary particle size of the solder particles used, the thickness of the conductive sheets was adjusted to 5 μm in Examples 1 to 10 and Comparative Examples 1 to 2, and to 20 μm in Examples 11 to 13 and Comparative Example 3.

[0136] Next, a dummy wafer with an Au electrode (10 mm x 10 mm, electrode square 50 μm, electrode end-to-end distance 50 μm) and alkali-free glass (10 mm x 10 mm) were prepared. Then, the release liner was peeled off the fabricated conductive sheet, and the conductive sheet was placed between the dummy wafer and the alkali-free glass.

[0137] Next, a laminate of a dummy wafer, a conductive sheet, and alkali-free glass was subjected to a first heating (thermocompression bonding) for 2 seconds at a temperature of 60°C and a pressure of 0.3 MPa. After the first heating, the laminate was observed with an optical microscope (digital microscope, manufactured by Keyence Corporation, product name "VHX-8000") to confirm that there were no trapped air bubbles.

[0138] Next, the laminate was placed in a vacuum pressure reflow apparatus (SST Vacuum Reflow System, product name "Model1200 Table Top Furnace"), vacuuming was performed, and then a second heating was carried out. For Examples 1 to 11 and Comparative Examples 1 to 3, which used SAC305 solder particles, the second heating was performed under the following conditions: pressurized to 4.5 atmospheres with nitrogen, heating rate of 200°C / min, maximum temperature of 260°C, and holding time of 60 seconds. For Examples 12 to 13, which used SnBi58 solder particles, the second heating was performed under the following conditions: pressurized to 4.5 atmospheres with nitrogen, heating rate of 100°C / min, maximum temperature of 170°C, and holding time of 60 seconds. As a result, a connecting member was formed from the conductive sheet, and a connecting structure was obtained.

[0139] (Evaluation of Solder Integration) The solder integration of the fabricated connection structure was evaluated using the following method. First, the connection structure was observed from the alkali-free glass side using an optical microscope (digital microscope, manufactured by Keyence Corporation, product name "VHX-8000"). The connection structure was observed at a magnification of 500x in four different field-of-view areas.

[0140] Next, for the 35 electrodes within the observation field, electrodes that were completely covered with solder were evaluated as pass, and those with part or all of their surface exposed were evaluated as fail. The ratio of electrodes evaluated as pass was considered the solder density, and evaluation was performed based on the following criteria: Evaluation Criteria 4: Solder density is 95% or higher. 3: Solder density is 90% or higher but less than 95%. 2: Solder density is 80% or higher but less than 90%. 1: Solder density is 50% or higher but less than 80%. 0: Solder density is less than 50%.

[0141] <Connection Evaluation> Using the conductive compositions of Examples 1, 9, 11, and 13, connection structures were fabricated using the following method, and connection evaluation was performed.

[0142] [Solder Connection Evaluation] (Examples 1, 9 and 11) First, a conductive composition was applied to a release liner (Mitsubishi Chemical Corporation, product name "MRA50" (thickness 50 μm)) using an applicator to form a coating film. A conductive sheet was prepared by drying the coating film at 60°C for 5 minutes. In Examples 1 and 9, the thickness of the conductive sheet was adjusted to 5 μm, taking into consideration the average primary particle size of the solder particles used, and in Example 11, the thickness of the conductive sheet was adjusted to 20 μm.

[0143] Next, two dummy wafers with Au electrodes (10 mm long x 10 mm wide) were prepared. In Example 1, a dummy wafer with an electrode square of 10 μm and an electrode end-to-end distance of 10 μm was used. In Examples 9 and 11, a dummy wafer with an electrode square of 50 μm and an electrode end-to-end distance of 50 μm was used. Next, the release liner was peeled off the fabricated conductive sheet, and the conductive sheet was placed between the two dummy wafers. At this time, a high-precision die bonding device (Finetech, product name "FINEPLACER lambda 2") was used to adjust the position of the electrodes of the opposing wafers so that they aligned via the conductive sheet.

[0144] Next, the laminate was placed in a vacuum pressure reflow apparatus (SST Vacuum Reflow System, product name "Model1200 Table Top Furnace"), and then vacuum was applied. Subsequently, it was pressurized to 4.5 atmospheres with nitrogen and heated under the conditions of a heating rate of 200°C / min, a maximum temperature of 260°C, and a holding time of 60 seconds. As a result, connecting members were formed from the conductive sheets, and a connecting structure was obtained.

[0145] The obtained connection structures were embedded in resin, and the laminated cross-section was exposed by mechanical polishing. The laminated cross-section was observed with an optical microscope (name "VHX-7000", manufactured by Keyence Corporation), and the solder connection between opposing electrodes was evaluated based on the following criteria: • Evaluation Criteria 2: Solder connection between opposing electrodes was observed. 1: Solder connection between opposing electrodes was not observed.

[0146] [Electrical Connection Evaluation] (Example 13) First, a conductive composition was applied to a release liner (Mitsubishi Chemical Corporation, product name "MRA50" (thickness 50 μm)) using an applicator to form a coating film. A conductive sheet (thickness 20 μm) was prepared by drying the coating film at 60°C for 5 minutes.

[0147] Next, two FPC substrates with Cu electrodes (electrode square 100 μm, electrode end-to-end distance 100 μm) were prepared. Then, the release liner was peeled off the fabricated conductive sheet, and the conductive sheet was placed between the two FPC substrates. At this time, a high-precision die bonding device (Finetech Co., Ltd., product name "FINEPLACER lambda 2") was used to adjust the position of the electrodes of the opposing FPC substrates so that they were aligned via the conductive sheet.

[0148] Next, the laminate was placed in a vacuum pressure reflow apparatus (SST Vacuum Reflow System, product name "Model1200 Table Top Furnace"), and then vacuum was applied. Subsequently, it was pressurized to 4.5 atmospheres with nitrogen and heated under the conditions of a heating rate of 100°C / min, a maximum temperature of 170°C, and a holding time of 60 seconds. As a result, connecting members were formed from the conductive sheets, and a connecting structure was obtained.

[0149] For this connection structure, the electrical resistance between the opposing electrodes was measured using a digital multimeter (name "PC500a", manufactured by Sanwa Electric Instruments Co., Ltd.), and the electrical connection (conductivity) of the opposing electrodes was evaluated based on the following criteria: 2: Electrical resistance could be measured (electrical resistance was measured as a positive value). 1: Electrical resistance could not be measured (the measurement range of the multimeter was overloaded).

[0150]

[0151]

[0152]

[0153] The abbreviations used in Tables 1-3 are as follows: SAC305 type10: Manufactured by DUKSAN Hi-Metal, product name "Aurora SAC305 EN (0-3μm)", Sn 96.5 wt%, Ag 3.0 wt%, Cu 0.5 wt%, melting point 218℃, spherical shape, average primary particle diameter 1μm SAC305 ST-3: Manufactured by Mitsui Mining & Smelting Co., Ltd., product name "SAC305 ST-3", Sn 96.5 wt%, Ag 3.0 wt%, Cu 0.5 wt%, melting point 218℃, spherical shape, average primary particle diameter 3μm SAC305 STC-7: Manufactured by Mitsui Mining & Smelting Co., Ltd., product name "SAC305 STC-7", Sn 96.5 wt%, Ag 3.0 wt%, Cu 0.5 wt%, melting point 218℃, spherical shape, average primary particle diameter 8μm SnBi58 STC-7: Manufactured by Mitsui Mining & Smelting Co., Ltd., product name "Sn42Bi58 STC-7", Sn42 wt%, Bi58 wt%, melting point 139°C, spherical shape, average primary particle size 8 μm jER828: Bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, product name "jER828", epoxy equivalent 184-194 g / eq, liquid (25°C)) HP7200HHH: Dicyclopentadiene type epoxy resin (manufactured by DIC Corporation, product name "EPICLON HP-7200HHH", epoxy equivalent 280-292 g / eq, solid (25°C)) XD1000: Dicyclopentadiene type epoxy resin (manufactured by Nippon Kayaku Co., Ltd., product name "XD-1000", epoxy equivalent 245-260 g / eq, solid (25°C)) NC7000H: Naphthalene type epoxy resin (manufactured by Nippon Kayaku Co., Ltd., product name "NC-7000H", epoxy equivalent 223-238 g / eq, solid (25°C)) NC3000H: Biphenyl type epoxy resin (manufactured by Nippon Kayaku Co., Ltd., product name "NC-3000H", epoxy equivalent 288 g / eq, solid (25°C)) NPES907: Bisphenol A type epoxy resin (manufactured by Nanya Plastics Co., Ltd., product name "NPES907", epoxy equivalent 1500-1600 g / eq, solid (25°C), softening point 120-130°C) EOCN102070: Cresol novolac type epoxy resin (manufactured by Nippon Kayaku Co., Ltd., product name "EOCN-1020-70", epoxy equivalent weight 191-207 g / eq, solid (25°C))jER1256: A varnish made by dissolving bisphenol A type epoxy resin (weight-average molecular weight 45,000, epoxy equivalent 8,500 g / eq, solid (25°C)) in methyl ethyl ketone (manufactured by Mitsubishi Chemical Corporation, product name "jER1256B40", solid content concentration 40% by weight) SG70L: A varnish made by dissolving (meth)acrylic resin (weight-average molecular weight 900,000, solid (25°C)) in toluene and methyl ethyl ketone (manufactured by Nagase ChemteX Corporation, product name "Teisan Resin SG-70L", solid content concentration 12.5% ​​by weight) UH2170: (meth)acrylic resin (manufactured by Toagosei Co., Ltd., product name "ARUFON UH-2170", weight-average molecular weight 14,000, solid (25°C)) jER4250: Bisphenol F type epoxy resin (manufactured by Mitsubishi Chemical Corporation, product name "jER4250", weight-average molecular weight 60,000, epoxy equivalent 8,200 g / eq, solid (25°C)) HXA9382HP: Curing agent (manufactured by Asahi Kasei Corporation, product name "NovaCure HXA9382HP") Note that the content of each component listed in Tables 1 to 3 is the value excluding the solvent (solid content equivalent).

[0154] As can be seen from Tables 1 to 3, the conductive compositions of the examples, which had a storage modulus of 10 kPa or more at 50°C, showed better adhesion test results using warped wafers compared to the comparative examples, and were less prone to peeling.

[0155] The conductive composition of the present invention can be used for connecting wiring circuit boards.

Claims

1. A conductive composition comprising conductive particles and a resin, wherein the storage modulus at 50°C is 10 kPa or more.

2. The conductive composition according to claim 1, wherein the peeling force determined by the following test is 0.30 N / 20 mm or more. Test: A conductive sheet (20 μm thick) made of the conductive composition is prepared on a polyethylene terephthalate support substrate, and then cut into strips measuring 50 mm in length and 20 mm in width to be used as test specimens. The test specimen is bonded to a stainless steel plate (SUS304 plate) via the conductive sheet, and a pressure of 0.3 MPa is applied for 2 seconds at a temperature of 80°C. The test specimen is peeled off the stainless steel plate under conditions of 23°C, 50% RH atmosphere, peeling speed of 3000 mm / min, and peeling angle of 180°. The maximum force required at this time is identified as the peeling force.

3. The conductive composition according to claim 1, wherein the conductive particles are solder particles.

4. The conductive composition according to claim 3, wherein the minimum value of the complex viscosity determined by the following test is 10 Pa·s or less. Test: The conductive composition, excluding the solder particles, is heated from 25°C to a temperature 30°C higher than the melting point T0 of the solder particles (T0 + 30°C) at a heating rate of 10°C / min. The complex viscosity of the conductive composition, excluding the solder particles, is measured from 25°C to the aforementioned temperature (T0 + 30°C), and its minimum value is determined.

5. The conductive composition according to claim 1, wherein the resin comprises at least one selected from the group consisting of epoxy resin, (meth)acrylic resin, phenoxy resin, and phenolic resin.

6. The conductive composition according to claim 1, wherein the resin comprises an epoxy resin.

7. The conductive composition according to claim 6, wherein the weight-average molecular weight of the epoxy resin is less than 10,000.

8. The conductive composition according to claim 6, wherein the epoxy resin comprises repeating units having glycidyl groups.

9. The conductive composition according to claim 6, wherein the epoxy resin has at least one selected from the group consisting of a dicyclopentadiene skeleton, a biphenyl skeleton, a naphthalene skeleton, a phenol skeleton, and a cresol skeleton.

10. The conductive composition according to claim 6, wherein the conductive composition comprises a liquid epoxy resin and a solid epoxy resin.

11. The conductive composition according to claim 6, wherein the content ratio of the epoxy resin in the solid portion of the resin is 50% by weight or more.

12. The conductive composition according to claim 1, wherein the resin comprises a polymer resin having a weight-average molecular weight of 10,000 or more.

13. The conductive composition according to claim 12, wherein the content of the polymer resin in the resin is 20% by weight or less.

14. The conductive composition according to claim 1, further comprising flux.

15. A conductive sheet comprising a conductive composition according to any one of claims 1 to 14.

16. A laminate comprising the conductive sheet described in claim 15 and a release liner.

17. A connecting structure comprising: a first substrate on which a first electrode is disposed; a second substrate on which a second electrode is disposed; and a connecting member connecting the first substrate and the second substrate, wherein the connecting member is formed from a conductive composition according to any one of claims 1 to 14.

18. A method for manufacturing a connecting structure according to claim 17, comprising: arranging the conductive composition between the first substrate and the second substrate; and heating the conductive composition to form the connecting member.

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