Conductive adhesive

Abstract

To provide a conductive adhesive enabling formation of an adhesive layer exhibiting a low linear expansion coefficient, high adhesive strength, and excellent conductivity.SOLUTION: A conductive adhesive comprises a coordination polymer containing a transition metal such as cobalt and an azole such as an imidazole, and conductive particles such as silver particles, copper particles, or gold particles.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an electrically conductive adhesive. [Background technology]

[0002] In electronic component materials such as semiconductor elements and liquid crystal display elements, various members (adherends) are bonded together using adhesives. Polymer-based adhesives such as epoxy resin adhesives have traditionally been used as adhesives for such electronic component materials. However, polymer-based adhesives have a high linear expansion coefficient, and when used to bond metal adherends, there is a problem in that the bonded portions are damaged by temperature changes.

[0003] Therefore, Japanese Patent Laid-Open Publication No. 2022-530 (Patent Document 1) discloses an adhesive composition capable of suppressing peeling after high-temperature, high-humidity treatment, which contains (a) a thermoplastic resin, (b) a silane compound having a urethane bond and an alkoxysilyl group in the molecule, (c) a radically polymerizable compound, and (d) a radical polymerization initiator, and contains (e) a compound having a urethane bond as a component other than the (a), (c), and (d) components, or the (a), (b), (c), and (d) components, and the cured product has an average linear expansion coefficient of 800 ppm / K or less at 30 to 90 °C. It also discloses that adding an insulating filler to the adhesive composition further suppresses peeling after high-temperature, high-humidity treatment. However, the adhesive composition described in Patent Document 1 has a problem in that, even when an insulating filler is added, the average linear expansion coefficient is greater than the linear expansion coefficient of the metal, and therefore, when bonding metal adherends together, the bonded portion can be damaged by temperature changes. Furthermore, there is also the problem that the addition of insulating fillers reduces adhesive strength.

[0004] In addition, Yanyi Zhao et al., ACS Nano, 2017, Vol. 11, pp. 3662-3670 (Non-Patent Document 1), have investigated adhesives using the Hoffmann-type cyano-bridged coordination polymer Ni(HO)2[Ni(CN)4]·4HO, and have disclosed that nanoflakes of platelet crystals of this Ni(HO)2[Ni(CN)4]·4HO can be used to bond adherends such as glass, plastic, and metal. However, paste-type adhesives containing solid powders have the problem of insufficient adhesive strength due to the tendency for voids to form in the adhesive layer after the solvent is removed by drying or other methods.

[0005] Furthermore, the adhesive composition described in Patent Document 1 and the adhesive described in Non-Patent Document 1 also have insufficient electrical conductivity, and are unsuitable for bonding between materials with different linear expansion coefficients, which require high adhesive strength and high electrical conductivity. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-530 [Non-patent literature]

[0007] [Non-Patent Document 1] Yanyi Zhao et al., ACS Nano, 2017, Vol. 11, pp. 3662-3670 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in consideration of the problems associated with the above-mentioned conventional technology, and aims to provide a conductive adhesive that has a low linear expansion coefficient, high adhesive strength, and is capable of forming an adhesive layer with excellent conductivity. [Means for solving the problem]

[0009] As a result of extensive research to achieve the above object, the inventors discovered that by using a conductive adhesive containing a coordination polymer such as a metal-organic framework (MOF) containing a transition metal and an azole, and conductive particles, it is possible to form an adhesive layer that has a low linear expansion coefficient, high adhesive strength, and excellent conductivity, and thus completed the present invention.

[0010] That is, the present invention provides the following aspects. [1] A conductive adhesive containing a coordination polymer containing a transition metal and an azole, and conductive particles. [2] The conductive adhesive according to [1], wherein the azole is at least one selected from the group consisting of imidazoles, triazoles, pyrazoles, tetrazoles, and furazans. [3] The conductive adhesive according to [1] or [2], wherein the conductive particles are at least one selected from the group consisting of silver particles, copper particles, gold particles, and aluminum particles.

[0011] Although the reasons why the conductive adhesive of the present invention can form an adhesive layer with high reliability against temperature changes, high adhesive strength, and excellent conductivity, even when bonding metal adherends, are not entirely clear, the inventors speculate as follows. Specifically, the conductive adhesive of the present invention contains a coordination polymer containing a transition metal and an azole, and conductive particles. Therefore, by heating and curing the conductive adhesive, crystalline particles of the coordination polymer are generated. The coordination polymer crystals have a linear expansion coefficient that is significantly smaller than that of polymer-based adhesives and comparable to that of metals. Therefore, it is speculated that the conductive adhesive of the present invention is less likely to expand with temperature changes and exhibits high reliability, even when bonding metal adherends. Furthermore, heating the conductive adhesive of the present invention densifies the crystalline particles of the coordination polymer, enabling sufficient removal of impurities such as unreacted raw materials and dispersion medium. This reduces the likelihood of impurities remaining in the conductive adhesive layer, further densifying the crystalline particles of the coordination polymer and resulting in high adhesive strength. Furthermore, since the conductive adhesive of the present invention contains conductive particles, it is presumed that an adhesive layer with excellent conductivity can be formed. Note that a "coordination polymer (CP)" is a complex having a continuous structure consisting of multidentate ligands and metal ions, and a "metal-organic framework (MOF)" is a coordination polymer (CP) that has pores. [Effects of the Invention]

[0012] According to the present invention, it is possible to form an adhesive layer that has a low linear expansion coefficient, high adhesive strength, and excellent electrical conductivity. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram showing a method for producing a test piece for measuring electrical resistance using a conductive adhesive. [Figure 2] 1A to 1C are schematic diagrams illustrating a method for producing a bonded body using a conductive adhesive. [Figure 3]1 is a graph showing the pressure dependency during heating of the shear strength (adhesive strength) of a bonded structure produced using the conductive adhesive prepared in Example 2. [Figure 4] 1 is a graph showing the shear strength (adhesive strength) of a bonded body produced using the conductive adhesive prepared in Example 2 before and after a heat resistance test (400° C., 100 hours). DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described in detail below based on preferred embodiments thereof.

[0015] [Conductive adhesive] First, the conductive adhesive of the present invention will be described. The conductive adhesive of the present invention contains a coordination polymer (CP) containing a transition metal and an azole, and conductive particles. The coordination polymer has a structure in which the azole is coordinated to the transition metal, and the polymer structure is formed by van der Waals forces and coordinate bonds.

[0016] (transition metal) The transition metal is not particularly limited as long as it can form a coordination polymer coordinated with an azole, but from the viewpoint of environmental friendliness and rarity, Group 6 elements such as Cr, Group 7 elements such as Mn, Group 8 elements such as Fe, Group 9 elements such as Co, Group 10 elements such as Ni, Group 11 elements such as Cu, and Group 12 elements such as Zn and Cd are preferred, with Cr, Mn, Fe, Co, Ni, Cu, Zn, and Cd being more preferred, Zn, Co, Mn, Ni, and Cu being even more preferred, and Zn and Co being particularly preferred. Furthermore, from the viewpoint of obtaining a conductive adhesive layer having high adhesive strength either before or after exposure to high temperatures, the transition metal preferably includes at least one selected from the group consisting of Zn and Co, and from the viewpoint of obtaining a conductive adhesive layer having high adhesive strength both before and after exposure to high temperatures, at least one selected from the group consisting of Zn and Co is more preferred.

[0017] (Azoles) The azoles are not particularly limited as long as they can be coordinated with the transition metal to form a coordination polymer, and examples thereof include pyrroles, diazoles (e.g., imidazoles, pyrazoles), triazoles, and tetrazoles. Among these azoles, imidazoles, pyrazoles, and triazoles are preferred from the viewpoint of coordination, imidazoles and triazoles are more preferred, and imidazoles are particularly preferred. Furthermore, examples of the imidazoles include imidazole, methylimidazole, and benzimidazole. From the viewpoint of obtaining a conductive adhesive layer having high adhesive strength before or after exposure to high temperatures, imidazole, methylimidazole, or a mixture thereof is preferred, and from the viewpoint of obtaining a conductive adhesive layer having high heat resistance, imidazole or methylimidazole is more preferred.

[0018] (coordination polymer) The decomposition temperature of the coordination polymer is preferably higher than the heating temperature (hereinafter also referred to as the "curing temperature") when the conductive adhesive of the present invention is cured. If the decomposition temperature of the coordination polymer is lower than the curing temperature, the coordination polymer will be decomposed by heating when the conductive adhesive is cured, which tends to make it difficult to form a conductive adhesive layer with high adhesive strength. The decomposition temperature of the coordination polymer can be measured by thermal analysis such as thermogravimetry (TGA).

[0019] Furthermore, the coordination polymer preferably has a crystal linear expansion coefficient of 20 ppm / K or less, more preferably 10 ppm / K or less. A conductive adhesive containing a coordination polymer whose crystals have such a linear expansion coefficient exhibits high reliability against temperature changes, even when bonding metal adherends together. The linear expansion coefficient of the coordination polymer crystal can be determined from the slope of the relationship between the lattice constant and temperature by measuring the temperature dependence of the lattice constant of the coordination polymer crystal, which is determined based on the XRD spectrum obtained by X-ray diffraction (XRD) measurement.

[0020] Specific examples of such coordination polymers include those shown in Table 1.

[0021] [Table 1]

[0022] Among these coordination polymers, from the viewpoint of ease of preparation of the conductive adhesive, coordination polymers containing at least one transition metal selected from the group consisting of Zn, Co, and Cd and in which the azoles are imidazoles (e.g., [Zn(2-MeIm)2], [Co(2-MeIm)2], [Zn(Im)2], [Cd(2-MeIm)2]) are preferred, and coordination polymers in which the transition metal is at least one selected from the group consisting of Zn and Co and in which the azoles are methylimidazoles (e.g., [Zn(2-MeIm)2], [Co(2-MeIm)2]) are more preferred. Furthermore, from the viewpoint of obtaining a conductive adhesive layer having high adhesive strength either before or after exposure to high temperatures, coordination polymers containing at least one selected from the group consisting of Zn and Co as the transition metal and in which the azoles are imidazoles (e.g., [Zn(2-MeIm)2], [Co(2-MeIm)2], [CoMn(2-MeIm)2], [CoNi(2-MeIm)2], [Zn(Im)2], [Zn2(2-MeIm)(Im)3]) are preferred, and from the viewpoint of obtaining a conductive adhesive layer having high heat resistance, coordination polymers containing at least one selected from the group consisting of Zn and Co as the transition metal are preferred. Coordination polymers in which the azole is imidazole or methylimidazole (e.g., [Zn(2-MeIm)2], [Co(2-MeIm)2], [CoMn(2-MeIm)2], [CoNi(2-MeIm)2], [Zn(Im)2]) are more preferred, and from the viewpoint of obtaining a conductive adhesive layer that has high adhesive strength both before and after exposure to high temperatures and high heat resistance, coordination polymers in which the transition metal is at least one selected from the group consisting of Zn and Co and the azole is methylimidazole (e.g., [Zn(2-MeIm)2], [Co(2-MeIm)2]) are even more preferred.

[0023] In the conductive adhesive of the present invention, when the coordination polymer is in a particulate form, the average particle size is not particularly limited, but is preferably, for example, 1 nm to 1 μm, and more preferably 1 nm to 100 nm.

[0024] (Conductive particles) The conductive particles are not particularly limited as long as they are conductive particles, and examples thereof include particles made of metals such as silver, copper, gold, and aluminum, particles made of conductive compounds such as indium tin oxide and gallium zinc oxide, particles made of conductive inorganic compounds containing carbon such as carbon particles, fullerenes, and carbon nanotubes, and particles made of conductive organic compounds having a π bond such as polyacetylene, polythiophene, polyaniline, and polyphenylene. Of these conductive particles, silver particles, copper particles, gold particles, and aluminum particles are preferred from the viewpoint of high electrical conductivity, and silver particles are more preferred.

[0025] The average particle size of the conductive particles is not particularly limited, and is preferably 100 nm to 100 μm, and more preferably 1 μm to 10 μm. When the average particle size of the conductive particles is larger than the thickness of the resulting conductive adhesive layer, the conductivity of the adhesive layer is ensured by a single particle. On the other hand, when the average particle size of the conductive particles is smaller than the thickness of the resulting conductive adhesive layer, the conductivity of the adhesive layer is ensured according to percolation theory.

[0026] (Conductive adhesive) The conductive adhesive of the present invention contains the coordination polymer and the conductive particles. By blending the conductive particles into the adhesive containing the coordination polymer, the resulting adhesive layer is imparted with conductivity. Furthermore, since the coordination polymer is thermally stable in the adhesive containing the coordination polymer, the resulting adhesive layer is resistant to thermal decomposition even when exposed to high temperatures and has excellent heat resistance. However, since the conductive adhesive of the present invention further contains conductive particles, the resulting adhesive layer tends to have the same or improved heat resistance.

[0027] The mass ratio of the coordinating polymer to the conductive particles (coordinating polymer:conductive particles) is, for example, preferably 1:1 to 1:64, more preferably 1:2 to 1:32, and even more preferably 1:4 to 1:16. If the mass ratio (coordinating polymer:conductive particles) is less than the lower limit, the resulting adhesive layer tends not to have sufficient conductivity, while if the mass ratio (coordinating polymer:conductive particles) exceeds the upper limit, the resulting conductive adhesive layer tends to have a high linear expansion coefficient and low adhesive strength.

[0028] There are no particular limitations on the method for preparing the conductive adhesive of the present invention, and examples include a method in which a compound containing the transition metal (preferably a salt, complex, or the like of the transition metal) and the azole are dissolved in a solvent to prepare a coordination polymer containing the transition metal and the azole, and if necessary, the solvent is removed to prepare a powder, paste, concentrated liquid, or the like comprising the coordination polymer, to which the conductive particles are added and mixed. Therefore, examples of the form of the conductive adhesive of the present invention include a powder mixture of particles comprising the coordination polymer and the conductive particles, and a paste or concentrated liquid containing the coordination polymer, the conductive particles, and the solvent.

[0029] Examples of the solvent include alcohols such as methanol and ethanol; amides such as dimethylformamide and diethylformamide; amines such as diethylamine and triethylamine; sulfoxides such as dimethyl sulfoxide and diethyl sulfoxide; ketones such as acetone and diethyl ketone; and water. From the viewpoint of ease of curing by heating, alcohols and water are preferred, and methanol is particularly preferred.

[0030] [Adhesion method] Next, a bonding method using the conductive adhesive of the present invention will be described. The bonding method using the conductive adhesive of the present invention is a method in which a conductive adhesive layer made of the conductive adhesive of the present invention is formed between adherends, and then the conductive adhesive layer is cured by heating.

[0031] (Conductive adhesive layer formation process) In the bonding method of the present invention, first, a conductive adhesive layer made of the conductive adhesive of the present invention is formed between the adherends. Specifically, an appropriate amount of the conductive adhesive of the present invention is applied to an adherend (preferably a metal adherend), and another adherend (preferably a metal adherend) is placed on top of it, thereby forming the conductive adhesive layer between the adherends.

[0032] (hardening process) Next, the conductive adhesive layer formed between the adherends is heated and cured, which crystallizes the coordination polymer in the conductive adhesive layer and removes impurities such as unreacted raw materials and solvents from the conductive adhesive layer, forming a densified cured layer of the conductive adhesive (cured conductive adhesive layer) in which the crystalline particles of the coordination polymer aggregate, thereby bonding the adherends with high adhesive strength.

[0033] The lower limit of the heating temperature (curing temperature) when curing the conductive adhesive layer is preferably 150°C or higher, more preferably 200°C or higher, and particularly preferably 250°C or higher, from the viewpoint that impurities such as unreacted raw materials and solvents can be sufficiently removed and impurities are less likely to remain in the resulting cured conductive adhesive layer, thereby further increasing the density of the crystalline particles of the coordination polymer and improving the adhesive strength. On the other hand, the upper limit of the heating temperature (curing temperature) when curing the conductive adhesive layer is preferably a temperature lower than the decomposition temperature of the coordination polymer, more preferably a temperature 30°C lower than the decomposition temperature of the coordination polymer, from the viewpoint of suppressing decomposition of the coordination polymer due to heating and forming a cured conductive adhesive layer with high adhesive strength.

[0034] Furthermore, when curing the conductive adhesive layer, it is preferable to heat it while applying pressure. This further removes impurities such as unreacted raw materials and solvents, making it even less likely that impurities will remain in the cured conductive adhesive layer, further increasing the density of the crystalline particles of the coordination polymer and further improving the adhesive strength. The pressure condition is preferably 1 MPa or higher, more preferably 5 MPa or higher, and even more preferably 10 MPa or higher. [Example]

[0035] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0036] Example 1 Cobalt(II) acetate tetrahydrate and 2-methylimidazole (2-MeIm) were dissolved in methanol in a molar ratio of Co:2-MeIm = 1:2 to prepare a ZIF-67 ([Co(2-MeIm)2]) precursor solution. This ZIF-67 precursor solution was vacuum dried at room temperature for one day and then left to dry thoroughly under a nitrogen atmosphere for several days, yielding a purple ZIF-67 microparticle-containing material (average particle size: 40 nm). This ZIF-67 microparticle-containing material was mixed with silver particles (average particle size: 45 μm) in a mass ratio of ZIF-67:Ag = 1:4 to prepare a conductive adhesive.

[0037] Example 2 A conductive adhesive was prepared in the same manner as in Example 1, except that the mass ratio of the ZIF-67 microparticle-containing material to the silver particles was changed to ZIF-67:Ag=1:8.

[0038] Example 3 A conductive adhesive was prepared in the same manner as in Example 1, except that the mass ratio of the ZIF-67 microparticle-containing material to the silver particles was changed to ZIF-67:Ag=1:15.

[0039] Example 4 A conductive adhesive having a mass ratio of ZIF-67 microparticle-containing material to copper particles of ZIF-67:Cu=1:8 was prepared in the same manner as in Example 2, except that copper particles (average particle size: 1 μm) were used instead of silver particles.

[0040] Example 5 A conductive adhesive having a mass ratio of ZIF-67 microparticle-containing material to gold particles of ZIF-67:Au = 1:8 was prepared in the same manner as in Example 2, except that gold particles (average particle size: 5 μm) were used instead of silver particles.

[0041] (Comparative Example 1) A conductive adhesive was prepared in the same manner as in Example 1, except that silica particles (average particle size: 5 μm) were used instead of silver particles, and the mass ratio of the ZIF-67 microparticle-containing material to the silica particles was changed to ZIF-67:SiO2 = 1:2.

[0042] <Electrical resistivity> As shown in Figure 1, a powder molding die was used to produce tablet-shaped test pieces in which each conductive adhesive prepared in the Examples and Comparative Examples was sandwiched between two copper plates. Specifically, first, the conductive adhesive 11 (180 mg) was sandwiched between two copper plates (7 mm diameter, 0.1 mm thickness) 12a and 12b, which was then sandwiched between upper washer 13a and lower washer 13b and set in die (inner diameter: 7 mm) 14. Next, upper punch 15a and lower punch 15b were set, and a pressure of 4 MPa was applied to produce a tablet in which the conductive adhesive was sandwiched between the two copper plates. This tablet was placed in a muffle furnace without pressure, first heated to 150°C over one hour, then held at 150°C for 30 minutes, then heated to 350°C over one hour, then held at 350°C for 30 minutes, and then naturally cooled to produce a tablet-shaped test piece 17 for measuring electrical resistance, in which a cured layer of the conductive adhesive (cured conductive adhesive layer) 16 was sandwiched between two copper plates 12a and 12b.

[0043] The electrical resistivity of the cured conductive adhesive layer of this test piece for electrical resistance measurement was measured using an insulation resistance meter (manufactured by Keithley, model: 6430). The results are shown in Table 2. In Table 2, "<10 -7 " indicates that the value is below the measurement limit.

[0044] <Linear expansion coefficient> The linear expansion coefficient of each conductive adhesive prepared in the examples was calculated using the following formula, with reference to Takuya Hashimoto, Surface Technology, 2016, Vol. 67, No. 3, pp. 122-127: α=α f ×V f +α m ×(1-V f ) (In the above formula, α is the linear expansion coefficient of the conductive adhesive, α f is the linear expansion coefficient of the mixed conductive particles, αm is the linear expansion coefficient of ZIF-67 particles, V f indicates the volume fraction of the mixed conductive particles.) The results are shown in Table 2. The linear expansion coefficients of each particle were calculated based on Miyazaki I et al., Small, 2023, 2300298, and were as follows: ZIF-67: 8.9 ppm / K, Ag: 19.7 ppm / K, Cu: 16.5 ppm / K, Au: 14.2 ppm / K.

[0045] [Table 2]

[0046] As shown in Table 2, it was confirmed that the adhesives containing ZIF-67 particles and conductive particles prepared in Examples 1 to 5 exhibit high conductivity. On the other hand, it was confirmed that the adhesive containing ZIF-67 particles and silica particles prepared in Comparative Example 1 has extremely low conductivity.

[0047] Furthermore, as shown in Table 2, it was found that the linear expansion coefficients of the conductive adhesives containing ZIF-67 particles and conductive particles prepared in Examples 1 to 5 were all smaller than the linear expansion coefficients of the conductive particles contained therein.

[0048] When bonding materials with different linear expansion coefficients, such as between metal and semiconductor, controlling the linear expansion coefficient is important. If the difference in linear expansion coefficient becomes too large, the bond will be destroyed by thermal stress. For example, when bonding a metal and a semiconductor, the adhesive is required to have a linear expansion coefficient between the linear expansion coefficient of the metal and the linear expansion coefficient of the semiconductor. However, when a resin is used as the matrix, as in conventional conductive adhesives, the linear expansion coefficient of the resin is higher than that of the metal, so the linear expansion coefficient of the conductive adhesive containing conductive particles and a resin is higher than that of the metal, making it unsuitable for bonding between materials with different linear expansion coefficients. On the other hand, the conductive adhesive of the present invention has a linear expansion coefficient lower than that of the metal, and is therefore considered to be suitable for bonding between materials with different linear expansion coefficients.

[0049] <Preparation of junction (1)> 2, the conductive adhesive 21 prepared in the example was applied to a disk-shaped adherend (oxygen-free copper, C1020) 22a having a diameter of 10 mm and a height of 5 mm to form a conductive adhesive layer. A disk-shaped adherend (oxygen-free copper, C1020) 22b having a diameter of 5 mm and a height of 2 mm was placed on the conductive adhesive layer and lightly pressed down from above to produce a temporary bonded body. This temporary bonded body was first heated to 150°C in an unpressurized muffle furnace over one hour, then held at 150°C for 30 minutes, then heated to 350°C over one hour, held at 350°C for 30 minutes, and then naturally cooled to produce a bonded body 24 in which two disk-shaped adherends 22a and 22b were bonded with a cured product of the conductive adhesive (cured conductive adhesive layer) 23.

[0050] <Preparation of junction (2)> A temporary bonded body prepared in the same manner as in <Preparation of bonded body (1)> above was heated at 300°C for 5 minutes while being pressurized at 5 MPa or 15 MPa using a small hot press, to prepare a bonded body 24 in which two disk-shaped adherends 22a and 22b were bonded with a cured product of the conductive adhesive (cured conductive adhesive layer) 23.

[0051] <Shear strength> The shear strength of the three types of bonded bodies prepared in the above <Preparation of bonded bodies (1)> and <Preparation of bonded bodies (2)> was measured using a shear strength tester that was homemade using a force gauge (manufactured by Imada Co., Ltd.) and an electric displacement meter.

[0052] The results of measurements on a bonded structure produced using the conductive adhesive prepared in Example 2 are shown in Figure 3. The shear strength values ​​shown in Figure 3 are the average values ​​of shear strengths measured for two bonded structures produced under the same conditions. As shown in Figure 3, it was found that the shear strength (adhesive strength) of the conductive adhesive prepared in Example 2 was improved by increasing the pressure during heating.

[0053] <Heat resistance> As in the above <Preparation of Bonded Structure (2)>, the temporary bonded structure was heated at 300°C for 5 minutes while being pressurized at 15 MPa. The bonded structure was then subjected to a heat resistance test in air at various temperatures for 100 hours. The shear rate of the bonded structure after the heat resistance test was measured in the same manner as in the above <Shear Strength>. Referring to Noriaki Dokoshi et al., Polymer, 1970, Vol. 19, No. 219, pp. 530-535, the temperature at which the bond strength (shear strength) was 30% of the bond strength (shear strength) before the heat resistance test was determined, and this was taken as the heat resistance temperature.

[0054] The results of measurements on the bonded bodies produced using the conductive adhesive prepared in Example 2 are shown in Table 3 and Figure 4. The shear strength values ​​shown in Table 3 and Figure 4 are the average values ​​of shear strengths measured under the same conditions for two bonded bodies produced under the same conditions. The shear strength before the heat resistance test was the average value measured for the bonded bodies produced under a pressure of 15 MPa in the above <Shear strength>.

[0055] [Table 3]

[0056] As shown in Table 3 and Figure 4, the shear strength of the bonded body after the heat resistance test at 400°C for 100 hours was approximately 30% of the shear strength of the bonded body before the heat resistance test, and it was found that the heat resistance temperature was approximately 400°C. [Industrial Applicability]

[0057] As described above, according to the present invention, it is possible to form an adhesive layer that has a low linear expansion coefficient, high adhesive strength, and excellent electrical conductivity. Therefore, the conductive adhesive of the present invention can bond metal adherends together with high adhesive strength and high reliability against temperature changes while ensuring excellent electrical conductivity, and is therefore useful as an adhesive for bonding electronic component materials such as semiconductor elements and liquid crystal display elements to metal or ceramic substrates while ensuring electrical conductivity. [Explanation of symbols]

[0058] 11:Conductive adhesive 12a, 12b: Copper plate 13a: Upper washer 13b: Bottom washer 14: Die 15a: Upper punch 15b: Down punch 16: Conductive adhesive hardened layer 17: Test piece for measuring electrical resistance 21: Conductive adhesive (layer) 22a, 22b: Disc-shaped adherend 23: Conductive adhesive hardened layer 24:Zygote

Claims

1. A conductive adhesive comprising a coordination polymer containing a transition metal and an azole, and conductive particles.

2. 2. The conductive adhesive according to claim 1, wherein the azole is at least one selected from the group consisting of imidazoles, triazoles, pyrazoles, tetrazoles, and furazans.

3. 2. The conductive adhesive according to claim 1, wherein the conductive particles are at least one type selected from the group consisting of silver particles, copper particles, gold particles, and aluminum particles.

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