Conductive adhesive composition

Abstract

The present invention provides a conductive adhesive composition which can achieve good electrical characteristics including connection resistance without compromising conductivity even if the amount of silver powder blended is relatively reduced. The conductive adhesive composition contains (A) a silver powder and (B) a resin component. Wherein (A) the silver powder contains (a1) flaky silver powder and (a2) spherical silver powder. (a1) The sheet-like silver powder has a thickness of 0.3 [mu] m or less, an average particle diameter D50 in the range of 4 to 9 [mu] m, and a BET specific surface area of 1.5 to 2.5 m2 / g. (a2) The spherical silver powder has an average particle diameter D50 of 0.01 to 3 [mu] m, a BET specific surface area of 0.5 to 2.5 m2 / g, and a tap density of less than 2 g / cm3. In addition, the ratio of the silver powder (A) in the solid content is 70 mass% or less.

Description

TECHNICAL FIELD

[0001] The present application relates to an electrically conductive adhesive composition, and particularly to an electrically conductive adhesive composition containing a silver powder and a resin component. BACKGROUND

[0002] Conventionally, in an electrically conductive adhesive composition (or an electrically conductive paste composition), as an electrically conductive powder, a noble metal powder typified by silver has been widely used from the viewpoint of obtaining good electrical conductivity and good reliability. However, since the noble metal powder such as silver powder is expensive, reduction of the content of the electrically conductive powder is being studied in order to reduce the cost.

[0003] If the content of the electrically conductive powder is reduced, the resulting electrically conductive adhesive composition cannot obtain good electrical conductivity, resulting in deterioration of electrical characteristics. Thus, for example, in order to achieve good electrical characteristics, a copper powder or a silver-coated copper powder or the like is studied instead of silver powder. However, if such a copper-based powder is used as an electrically conductive powder, reliability can be reduced due to oxidation of copper or the like.

[0004] Thus, for example, Patent Document 1 discloses an electrically conductive paste composition in which two kinds of flaky silver powders (thin plate-like silver powders) are used in order to reduce the content of silver powder and achieve good electrical conductivity. In Patent Document 1, for the two kinds of flaky silver powders, the average particle diameter, the specific surface area, and the apparent density are optimized, respectively, and the blending ratio and the content with respect to the resin component are specified.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT DOCUMENTS

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2004-111057 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] In Patent Document 1, reduction of the content of silver powder in the electrically conductive paste composition is attempted by blending two different kinds of flaky silver powders at predetermined ratios. However, as a result of intensive studies by the inventors, it has been found that if the electrically conductive powder is only a flaky silver powder, it can be practically impossible to sufficiently achieve good connection resistance (resistance in the thickness direction) after curing of the electrically conductive adhesive composition.

[0010] The present application has been achieved in order to solve such a problem, and aims to provide an electrically conductive adhesive composition which can achieve good electrical characteristics including connection resistance even if the blending amount of silver powder is relatively reduced without impairing the electrical conductivity.

[0011] MEANS OF SOLVING THE PROBLEM

[0012] To address the aforementioned issues, the conductive adhesive composition disclosed herein comprises (A) silver powder and (B) a resin component. The (A) silver powder contains (a1) flake-shaped silver powder and (a2) spherical silver powder. The (a1) flake-shaped silver powder has a thickness of 0.3 μm or less, an average particle size D50 in the range of 4 to 9 μm, and a BET specific surface area in the range of 1.5 to 2.5 m². 2 Within the range of / g, the average particle size D50 of the above (a2) spherical silver powder is in the range of 0.01 to 3 μm, and the BET specific surface area is in the range of 0.5 to 2.5 m². 2 Within the range of / g, the tap density is less than 2g / cm³. 3 Furthermore, the proportion of the silver powder in the solid composition is less than 70% by mass.

[0013] Based on the above structure, since (a1) flake silver powder and (a2) spherical silver powder that meet predetermined conditions are used as (A) silver powder, even if the amount of (A) silver powder is relatively reduced in the conductive adhesive composition, the conductivity is not compromised, and good electrical properties, including connection resistance, can be achieved. Moreover, since the amount of expensive (A) silver powder used can be reduced (compound amount), the high cost of the conductive adhesive composition can be suppressed or avoided.

[0014] Furthermore, in conventional conductive adhesive compositions, copper-containing powders such as copper powder or silver-coated copper powder are sometimes used as conductive powders to suppress high costs. However, the reliability of such conductive adhesive compositions is questionable due to copper oxidation and other factors. Therefore, conductive adhesive compositions using copper-containing powders tend to be difficult to use in applications requiring high reliability. In contrast, according to the above structure, since the amount (content) of silver powder can be reduced by not using copper-containing powder, it can be used in applications requiring high reliability.

[0015] The conductive adhesive composition with the structure described above may also be configured such that the above-described (a1) flake silver powder and the above-described (a2) spherical silver powder are combined in a mass ratio ranging from 20 / 80 to 80 / 20.

[0016] Furthermore, the conductive adhesive composition with the above structure may also be configured such that the resin component (B) is a thermosetting resin and its curing agent or reaction initiator.

[0017] Furthermore, the conductive adhesive composition with the above structure may also be configured such that the thermosetting resin is at least one resin selected from the group consisting of epoxy resin, phenolic resin, acrylic resin, polyurethane resin, and silicone resin.

[0018] Furthermore, the conductive adhesive composition with the structure described above can also be configured to be applied to a substrate using a printing press or a dispensing machine.

[0019] Furthermore, the conductive adhesive composition with the structure described above can also be configured for bonding electronic components.

[0020] Furthermore, the conductive adhesive composition with the structure described above can also be configured such that the electronic component is a solar cell module.

[0021] Invention Effects

[0022] In this invention, the above-described configuration achieves the following effect: it provides a conductive adhesive composition that achieves good electrical properties, including connection resistance, without compromising conductivity even with a relatively reduced amount of silver powder. Attached Figure Description

[0023] Figure 1 (A) is a schematic model diagram showing the state of the solid components in a conductive adhesive composition containing only flake silver powder. Figure 1 (B) is a schematic diagram illustrating the number of interfacial contacts between a conductive adhesive composition containing only flake silver powder and the conductive adhesive composition involved in this disclosure, including conductivity and silver powder.

[0024] Figure 2 This is a top view schematically illustrating the configuration of an evaluation conductor pattern used in evaluating the conductivity and bond strength of a conductive adhesive composition after curing, as in embodiments of the present disclosure.

[0025] Figure 3 This is a schematic diagram illustrating the configuration of an evaluation sample used in evaluating the connection resistance and bond strength of a conductive adhesive composition after curing, as in embodiments of this disclosure. Detailed Implementation

[0026] The following describes typical embodiments of this disclosure.

[0027] The conductive adhesive composition disclosed herein has the following composition: it contains (A) silver powder and (B) resin components; (A) the silver powder contains (a1) flake-shaped silver powder and (a2) spherical silver powder; the thickness of (a1) the flake-shaped silver powder is less than 0.3 μm, the average particle size D50 is in the range of 4 to 9 μm, and the BET specific surface area is in the range of 1.5 to 2.5 m². 2 Within the range of / g, (a2) the average particle size D50 of the spherical silver powder ranges from 0.01 to 3 μm, and the BET specific surface area ranges from 0.5 to 2.5 m². 2 Within the range of / g, the tap density is less than 2g / cm³. 3Furthermore, the proportion of silver powder in the solid composition is less than 70% by mass.

[0028] [(A) Silver powder]

[0029] The conductive adhesive composition disclosed herein contains (A) silver powder, which is composed of a mixture of (a1) flake-shaped silver powder and (a2) spherical silver powder. That is, in this disclosure, two types of silver powder with different shapes are used as conductive components. These silver powders all meet predetermined conditions (predetermined physical properties).

[0030] First, (a1) the flake-shaped silver powder only needs to meet the following predetermined properties: its shape is flake-like (scaly or thin-film), its thickness is less than 0.3 μm, its average particle size D50 is in the range of 4 to 9 μm, and its BET specific surface area is in the range of 1.5 to 2.5 m². 2 Within the range of / g. Furthermore, the apparent density of (a1) flake silver powder can also be less than 1.0 g / cm³. 3 The tap density can also be less than 2 g / cm³. 3 .

[0031] (a2) Spherical silver powder only needs to meet the following predetermined physical properties: its shape is spherical (granular), the average particle size D50 is in the range of 0.01 to 3 μm, and the BET specific surface area is in the range of 0.5 to 2.5 m². 2 Within the range of / g, the tap density is less than 2g / cm³. 3 Furthermore, (a2) the apparent density of the spherical silver powder can also be less than 1.0 g / cm³. 3 .

[0032] In addition, in this disclosure, the average particle size, BET specific surface area, tap density and apparent density of (a1) flake silver powder and (a2) spherical silver powder, as well as the thickness of (a1) flake silver powder, are determined or calculated by the methods shown in the embodiments described later.

[0033] Furthermore, the various conditions in the various determination or evaluation methods related to silver powder can be conditions known in the field of conductive adhesive compositions or resin-based conductive pastes (e.g., the conditions described in the publication of the applicant's prior patent).

[0034] In the conductive adhesive composition disclosed herein, it is important to use both (a1) flake silver powder and (a2) spherical silver powder, which satisfy predetermined physical properties, as (A) silver powder. For example Figure 1 As shown in (A), the cured product of the conductive adhesive composition is assumed to have the following composition: thick sheet silver powder 11 or thin sheet silver powder 12 dispersed in the resin component 10.

[0035] likeFigure 1 As schematically shown in (A), in the case of any sheet silver powder 11, when formulated with the same mass as sheet silver powder 12, the density of silver powder 11 in the resin component 10 is relatively lower. As a result, the (lateral) conductor resistance of the cured product tends to increase relatively easily. In particular, if the predetermined physical properties set by the sheet silver powder of this disclosure (a1) are not met, the conductor resistance of the cured product tends to increase further.

[0036] Moreover, such as Figure 1 As illustrated in (B), if we consider the resistance in the thickness direction, it is assumed that the number of interfacial contacts of the thicker flake silver powder 11 is less than that of the thinner flake silver powder 12. Therefore, it is considered that in the obtained cured product, the interfacial contacts with... Figure 1 (A) On the contrary, thick sheet-like silver powder 11 can reduce the connection resistance in the thickness direction.

[0037] In contrast, in the conductive adhesive composition of this disclosure, since both (a1) flake silver powder and (a2) spherical silver powder satisfy the aforementioned predetermined properties, the spherical powder can easily and effectively contact the flake powder. As a result, it can be considered that the increase in the number of interfacial contacts of the (A) silver powder in the cured product can be effectively suppressed. Based on this, the (lateral) conductor resistance and the connection resistance in the thickness direction in the cured product can be effectively reduced.

[0038] In the conductive adhesive composition of this disclosure, the mixing ratio (a1) of flake silver powder to spherical silver powder in the total amount of silver powder (A) is not particularly limited. Typically, as shown in the examples described later, the mixing ratio ((a1) / (a2)) of flake silver powder to spherical silver powder is in the range of 20 / 80 to 80 / 20 by mass. If the mixing ratio of flake silver powder to spherical silver powder is within this range, the cured product of the conductive adhesive composition of this disclosure can easily possess both good electrical properties and good adhesive strength.

[0039] In the conductive adhesive composition disclosed herein, in (A) the silver powder, as (a1) the flake silver powder, only one type of silver powder satisfying the predetermined properties may be used, or two or more types of silver powder satisfying the predetermined properties may be used in appropriate combination. Similarly, as (a2) the spherical silver powder, only one type of silver powder satisfying the predetermined properties may be used, or two or more types of silver powder satisfying the predetermined properties may be used in appropriate combination.

[0040] The conductive adhesive composition disclosed herein may also contain conductive powder (particles) made of materials other than (A) silver powder. However, the conductive adhesive composition of this disclosure must relatively reduce the content of (A) silver powder while achieving good electrical properties. Therefore, it is desirable to contain conductive powders that do not contain materials with lower conductivity than silver (Ag). Examples of conductive powders that can be used in conjunction with (A) silver powder include gold (Au) or palladium (Pd).

[0041] Furthermore, (A) silver powder contains no other metallic components besides trace amounts of impurities. That is, the (A) silver powder in this disclosure is simply a metallic powder composed of silver alone. The trace amounts mentioned here are within the range known in the art of manufacturing silver powder and are not specifically limited. On the other hand, the material composition of other conductive powders that can be used with (A) silver powder is not particularly limited; they can be powders composed of a single metal (or conductive material) (metal powder) or alloy powders composed of multiple metals.

[0042] Furthermore, the shape of the silver powder (A) is as described above, and is not limited to (a1) flake silver powder and (a2) spherical silver powder; it may also contain silver powder of other shapes as required. The shape of other conductive powders that can be used with the silver powder (A) is not particularly limited; they may be spherical, flake, or other shapes.

[0043] Furthermore, even if the flake-like silver powder in (a1) of this disclosure has some unevenness and appears deformed, it is acceptable as long as the powder as a whole appears to be a flat or thin rectangular prism. "Flake-like" can also be referred to as flaky or scaly. Moreover, even if the spherical silver powder in (a2) of this disclosure has some unevenness and appears deformed, it is acceptable as long as the powder as a whole appears to be a three-dimensional powder that is closer to a cube than a rectangular prism. Additionally, "spherical" can also be referred to as granular.

[0044] (A) There is no particular limitation on the method of manufacturing silver powder, and known methods can be used. If it is (a2) spherical silver powder, examples include powder manufactured by wet reduction, powder manufactured by other known methods such as electrolysis or atomization, etc., and there is no particular limitation. If it is (a1) flake silver powder, flake silver powder can be manufactured by using spherical silver powder manufactured by known methods as raw powder and subjecting the raw powder to known mechanical processing.

[0045] [(B) Resin Composition]

[0046] The conductive adhesive composition disclosed herein contains the aforementioned (A) silver powder and (B) resin component. In this disclosure, the total amount of (A) silver powder and (B) resin component constitutes the solid component of the conductive adhesive composition. However, in this disclosure, it is also permissible to include other components as solid components.

[0047] In the conductive adhesive compositions disclosed herein, the specific type of resin component (B) is not particularly limited, but is typically a thermosetting resin and its curing agent, or a thermosetting resin and its reaction initiator (or polymerization initiator). Furthermore, in the following description, the reaction initiator (polymerization initiator) is sometimes appropriately referred to simply as "initiator".

[0048] In this disclosure, there is no particular limitation on the specific types of thermosetting resins that can be used as resin component (B). Typical examples include at least one resin selected from the group consisting of epoxy resin, phenolic resin, acrylic resin, polyurethane resin, and silicone resin. That is, in this disclosure, as resin component (B), only one of these resins may be used, or two or more may be appropriately selected and used.

[0049] In addition, the term "thermosetting resin" in this disclosure includes curable compositions (e.g., monomers or prepolymers, etc.) that, upon curing, become epoxy resins, phenolic resins, acrylic resins, polyurethane resins, silicone resins, or other resins.

[0050] Furthermore, in this disclosure, even when only one type of resin constituting these groups is used, two or more resins classified as such may be appropriately combined and used. The same applies when two or more resins constituting these groups are used. For convenience, if epoxy resin, phenolic resin, acrylic resin, polyurethane resin, silicone resin, etc., are designated as "superior categories," and specific resins belonging to epoxy resin are designated as "sub-categories," then either one or more resins from the superior category or one or more resins from the sub-category can be used.

[0051] For example, in Examples 1 to 7, as resin component (B), epoxy resin belonging to the higher classification and phenolic resin belonging to the higher classification were used in combination, but as epoxy resin, two epoxy resins belonging to the lower classification were used (only one phenolic resin belonging to the lower classification was used). Moreover, in Examples 8 to 14, as resin component (B), although only acrylic resin belonging to the higher classification was used, a total of four acrylic resins belonging to the lower classification were used.

[0052] Furthermore, in this disclosure, as resin component (B), thermosetting resins other than epoxy resins, phenolic resins, acrylic resins, polyurethane resins, and silicone resins (curable compositions that become resins through curing) may also be used in combination. Moreover, when epoxy resins, phenolic resins, acrylic resins, polyurethane resins, silicone resins, or other thermosetting resins are used in combination, their mixing ratio is not particularly limited. Not only is the combination of resins in the higher-level classification not particularly limited, but the mixing ratio when multiple lower-level classification resins are used in combination is also not particularly limited.

[0053] Next, each resin used in this disclosure that constitutes the above-mentioned group and is equivalent to the higher-level classification will be specifically described with a focus on the lower-level classification.

[0054] First, the specific composition of the epoxy resin used as resin component (B) in this disclosure is not particularly limited. Typically, for example, a multi-component epoxy resin having two or more ethylene oxide rings (epoxy groups) in one molecule can be cited.

[0055] Examples of such multi-component epoxy resins include glycidyl ether type, glycidyl amine type, glycidyl ester type, and alicyclic type. Glycidyl ether type resins can be obtained by reacting epichlorohydrin with phenolic varnishes (novolac), polyphenols, and polyols. Examples of phenolic varnishes include phenolic varnish and cresol varnish; examples of polyphenols include bisphenol A, hydrogenated bisphenol A, bisphenol F, bisphenol AD, and resorcinol; examples of polyols include ethylene glycol, neopentyl glycol, glycerol, trimethylolpropane, neopentyl tertrol, triethylene glycol, and polypropylene glycol. Monofunctional glycidyl ether type epoxy resins can also include phenyl glycidyl ether. Glycidyl amine type resins can be obtained by reacting epichlorohydrin with polyamine compounds such as ethylenediamine, triethylenetetramine, and aniline. Glycidyl ester type epoxy resins can be obtained by reacting epichlorohydrin with polycarboxylic acid, phthalic acid, isophthalic acid, and other polycarboxylic acid compounds. Alicyclic type epoxy resins can be synthesized by oxidation of olefins, etc. These epoxy resins can be used alone or in appropriate combinations of two or more.

[0056] Furthermore, in this disclosure, when using epoxy resin as resin component (B), end-capped polyisocyanate compounds may also be used. The epoxy equivalent of the epoxy resin used in this disclosure is not particularly limited; typically, it can be in the range of 100 to 1000, or even 100 to 400. If the epoxy equivalent is less than 100, it may have some effect on the physical properties of the cured product formed from the resulting conductive adhesive composition. On the other hand, if the epoxy equivalent is greater than 1000, the thixotropic properties of the resulting conductive adhesive composition may decrease.

[0057] In the embodiments described later, in Examples 1 to 7 and Comparative Examples 1 to 7, commercially available phenolic varnish-type glycidyl ether epoxy resin and commercially available phenyl glycidyl ether as a monomer of monofunctional glycidyl ether epoxy resin were used as one of the resin components (B).

[0058] Next, the specific composition of the phenolic resin used as resin component (B) in this disclosure is not particularly limited. Typically, known resins formed by reacting phenols with aldehydes can be appropriately used. Specifically, examples include: phenolic varnish-type phenolic resins, methyl phenolic resins, triphenylmethane-type phenolic resins, naphthyl phenolic resins, cyclopentadiene-type phenolic resins, arylalkylene-type phenolic resins, etc. Among these, phenolic varnish-type phenolic resins or methyl phenolic resins are particularly noteworthy, but there are no particular limitations.

[0059] Phenolic resins for varnishes are not particularly limited to any resins obtained by reacting known phenols with known aldehydes using an acidic catalyst.

[0060] There are no particular limitations on the phenols used in phenolic resin varnishes. Examples include: phenol, cresol, xylenol, ethylphenol, p-phenylphenol, p-tert-butylphenol, p-tert-amylphenol, p-octylphenol, p-nonylphenol, p-cumylphenol, bisphenol A, bisphenol F, resorcinol, etc. Only one of these phenols may be used, or two or more may be used in appropriate combinations.

[0061] There are no particular limitations on the aldehydes used in phenolic resin varnishes. Examples include alkyl aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, and butyraldehyde; and aromatic aldehydes such as benzaldehyde and salicylaldehyde. Only one of these aldehydes may be used, or two or more may be used in appropriate combinations.

[0062] When manufacturing phenolic resin varnishes, there are no particular limitations on the acidic catalyst used to react the phenols and aldehydes; known organic sulfonic acids, inorganic acids, etc., can be used appropriately. Furthermore, there are no particular limitations on the molar ratio of the phenols to the aldehydes during the reaction; a known molar ratio can be selected.

[0063] There are no particular limitations on the type A phenolic resin, as long as it is obtained by reacting known phenols with known aldehydes through catalysts such as alkali metals, amines, or divalent metal salts.

[0064] There are no particular limitations on the phenols used in methyl phenolic resins. Examples include: cresols such as phenol, o-cresol, m-cresol, and p-cresol; xylenes such as 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, and 3,5-xylenol; ethylphenols such as o-ethylphenol, m-ethylphenol, and p-ethylphenol; butylphenols such as isopropylphenol, butylphenol, and p-tert-butylphenol; and p-tert-amylphenol, p-octylphenol, p-nonylphenol, and p-cumylphenol. Alkylphenols such as phenols; halogenated phenols such as fluorophenol, chlorophenol, bromophenol, and iodophenol; monohydric phenols such as p-phenylphenol, aminophenol, nitrophenol, dinitrophenol, and trinitrophenol; monohydric phenols such as 1-naphthol and 2-naphthol; polyhydric phenols such as resorcinol, alkyl resorcinol, pyrogallol, catechol, alkyl catechol, hydroquinone, alkyl hydroquinone, phloroglucin, bisphenol A, bisphenol F, bisphenol S, and dihydroxynaphthalene. Only one of these phenols may be used, or two or more may be used in appropriate combinations.

[0065] There are no particular limitations on the aldehydes used in methyl phenolic resins. Examples include: formaldehyde, paraformaldehyde, trioxane, acetaldehyde, propionaldehyde, polyoxymethylene, trichloroacetaldehyde, hexamethylenetetramine, furfural, glyoxal, n-butyraldehyde, hexanal, allyl aldehyde, benzaldehyde, crotonaldehyde, acrolein, tetraoxymethylene, phenylacetaldehyde, o-tolualdehyde, and salicylaldehyde. Only one of these aldehydes may be used, or two or more may be used in appropriate combinations.

[0066] When manufacturing methyl phenolic resins, there are no particular limitations on the various catalysts used to react phenols and aldehydes. Specifically, examples include hydroxides, oxides, and carbonates of metals from Group 1 or Group 2 of the periodic table, known low-molecular-weight organic amines, and divalent metal acetates. Furthermore, there are no particular limitations on the molar ratio of the phenols to the aldehydes during the reaction; a known molar ratio can be chosen.

[0067] In the embodiments described later, in Examples 1 to 7 and Comparative Examples 1 to 7, commercially available phenolic varnish-type phenolic resin was used as one of the resin components (B).

[0068] Next, the specific composition of the acrylic resin used as resin component (B) in this disclosure is not particularly limited. Generally, polymers of polymerizable acrylic compounds such as acrylic acid (acrylate) or methacrylic acid (methacrylate) or their esters can be included. The acrylic resin in this disclosure may also be used in conjunction with other monomers or prepolymers that can polymerize with acrylic compounds.

[0069] Typical acrylic compounds include, for example, (meth)acrylates (acrylates or methacrylates), ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isopentyl (meth)acrylate, isoopentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate (laurate), stearyl (meth)acrylate (octadecyl (meth)acrylate), and other chain alkyl (meth)acrylates. Cyclohexyl methacrylate, isobornyl methacrylate, and other cyclic alkyl methacrylates; alkoxy-containing methacrylates such as 1-methoxyethyl methacrylate, ethoxy-diethylene glycol methacrylate, and methoxy-triethylene glycol methacrylate; phosphate methacrylates, 2-(meth)acryloyloxyethyl acid phosphate, di-(2-methacryloyloxyethyl)-phosphate, 2-(meth)acryloyloxypropyl acid phosphate, 2-(meth)acryloyloxybutyl acid phosphate, acid phosphoryloxy polyoxypropylene glycol mono(meth)acrylate, acid phosphoryloxy polyoxyethylene glycol mono(meth)acrylate, butyrolactone-modified phosphate methacrylate, and valproic acid phosphate. Modified phosphate (meth)acrylates, proprolactone-modified phosphate (meth)acrylates, caprolactone-modified phosphate (meth)acrylates, and other phosphate-containing (meth)acrylates; benzyl (meth)acrylate, phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxytetraethylene glycol (meth)acrylate, nonylphenoxyethyl (meth)acrylate, nonylphenoxytetraethylene glycol (meth)acrylate, and other (meth)acrylate aromatic esters; phenyl glycidyl ether acrylate hexamethylene diisocyanate urethane prepolymer, neopentyl tetraacrylate hexamethylene diisocyanate urethane prepolymer, neopentyl tetraacrylate toluene diisocyanate urethane prepolymer, di-neoptiol... (Meth)acrylate prepolymers such as tetraol pentaacrylate, hexamethylene diisocyanate, and urethane prepolymers; (meth)acrylate epoxy esters such as bisphenol A diglycidyl ether (meth)acrylate adduct and 2-hydroxy-3-phenoxypropyl (meth)acrylate; (meth)acrylate amino esters such as dimethylaminoethyl (meth)acrylate and dimethylaminopropyl (meth)acrylate; poly(meth)acrylates such as polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, di-trimethylolpropane tetra(meth)acrylate, ethylene glycol di(meth)acrylate, and diethylene glycol di(meth)acrylate.These acrylic compounds can be used alone or in appropriate combinations of two or more.

[0070] In the examples described later, in Examples 8 to 14 and Comparative Examples 8 to 13, as resin component (B), an acrylic resin was used with commercially available isoamyl acrylate, phenoxyethyl acrylate, 2-methacryloyloxyethyl phosphate and phenyl glycidyl acrylate hexamethylene diisocyanate carbamate prepolymer as monomers.

[0071] Next, the specific composition of the polyurethane resin used as resin component (B) in this disclosure is not particularly limited. Typically, examples include those formed by capping the isocyanate groups of a known polyisocyanate compound (capped polyisocyanate compound).

[0072] Specific examples of the polyisocyanate compounds used include: phenylene diisocyanate, toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymethylene polyphenyl polyisocyanate, polyaryl polyisocyanate, bitoluene diisocyanate, xylene diisocyanate, naphthalene diisocyanate, and other aromatic isocyanate compounds; ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), dodecamethyl diisocyanate, isophorone diisocyanate (IPDI), and hydrogenated xylene diisocyanate. Aliphatic polyisocyanate compounds such as dicyclohexylmethane diisocyanate (hydrogenated MDI), cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, octamethylene diisocyanate, and trimethylhexamethylene diisocyanate; modified polyisocyanate compounds containing carbamate, carbodiimide, urea, biuret, ureadiketone, ureaimide, isocyanurate, or oxazolidinone groups; and cyclized trimers of these polyisocyanate compounds, i.e., isocyanurate compounds (which can also be classified as modified isocyanurate compounds), are not particularly limited.

[0073] Among these polyisocyanate compounds, those containing, for example, trinuclear poly(phenyl) polyisocyanates in their composition can be used. Furthermore, compounds containing terminal isocyanate groups, synthesized by reacting polyisocyanates with polyols using known methods, can also be used as the polyurethane resins of this disclosure. The polyol used in this case is not particularly limited; general polyether polyols, polyester polyols, polycarbonate polyols, etc., can be appropriately used.

[0074] Among these polyols, examples of polyether polyols (or polyalkylene polyols) include those formed by the addition of polyols or phenolic compounds such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, bisphenol A, hydrogenated bisphenol A, glycerol, trimethylolpropane, or neopentyl tertrol to ethylene oxide, propylene oxide, or butane oxide.

[0075] Furthermore, examples of polyester polyols include those formed by condensing polyols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-cyclohexanediol, and trimethylolpropane with polyacids such as malonic acid, succinic acid, adipic acid, phthalic acid, and terephthalic acid.

[0076] Furthermore, examples of polycarbonate polyols include those formed by reacting polyols or phenolic compounds such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanediol, 1,4-cyclohexanediol, and bisphenol A with dimethyl carbonate, diphenyl carbonate, or phosgene.

[0077] Furthermore, there are no particular limitations on the end-capping agents for polyisocyanate compounds. Specific examples include: imidazoles such as 2-methylimidazolium, pyrazole, 3-methylpyrazole, 3,5-dimethylpyrazole, and 1,2,4-triazole; phenols such as phenol, cresol, ethylphenol, n-propylphenol, isopropylphenol, n-butylphenol, octylphenol, nonylphenol, xylenol, diisopropylphenol, di-tert-butylphenol, xylenol, chlorophenol, and ethylphenol; and oximes such as formaldehyde oxime, acetaldehyde oxime, acetoxime, methyl ethyl ketone oxime (MEK Oxime), methyl isobutyl ketone oxime (MIBK Oxime), diacetyl monooxime, and cyclohexanone oxime.

[0078] In this disclosure, the above-mentioned compounds used as polyurethane resins may be used in combination or only one of them may be used.

[0079] Next, the specific composition of the silicone resin used as resin component (B) in this disclosure is not particularly limited. Typically, known thermosetting silicone resins can be cited as examples.

[0080] Specifically, examples include structures having a skeletal structure such as silane, organosilicon oligomer, organosilicon resin, organosiloxane, diorganosiloxane, organopolysiloxane, or diorganopolysiloxane, and such skeletal structure having one or more reactive functional groups. The aforementioned skeletal structure can be a straight-chain structure or a branched chain.

[0081] Furthermore, as reactive functional groups, examples include hydroxyl, alkenyl, hydrosilyl, (meth)acryloyl, epoxy, amino, carbinol group, mercapto, carboxyl, and phenolic groups bonded to the silicon atoms contained in the above-mentioned framework structure, without particular limitation. Moreover, in addition to the aforementioned reactive functional groups, the above-mentioned framework structure may also contain alkyl, alkenyl, aromatic, and other functional groups.

[0082] The thermosetting silicone resin used as resin component (B) in this disclosure may have a single skeletal structure and a single reactive functional group, or it may have multiple skeletal structures and multiple reactive functional groups. Furthermore, as mentioned above, a skeletal structure may contain more than one reactive functional group; in other words, a single molecule of silicone resin (having any skeletal structure) may have at least one reactive functional group. Additionally, the reactive functional group may be located at the end of the skeletal structure, on a side chain, or at both the end and side chain.

[0083] [Other ingredients]

[0084] The conductive adhesive compositions disclosed herein may also contain components other than (A) silver powder and (B) resin components. Typically, as previously mentioned, examples include: curing catalysts or reaction initiators (polymerization initiators).

[0085] In this disclosure, when epoxy resin is used as resin component (B), a curing agent is used during curing. The curing agent used in this disclosure is not particularly limited, as long as it cures the epoxy resin described above.

[0086] Specific curing agents include, for example: phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, succinic anhydride, and other acid anhydrides; imidazoles, 2-methylimidazolium, 2-ethyl-4-methylimidazolium, 2-undecylimidazolium, 2-heptadecylimidazolium, 1-benzyl-2-methylimidazolium, 2-phenyl-4-methylimidazolium, 1-cyanoethyl-2-methylimidazolium, 1-aminoethyl-2-methylimidazolium, 1-methylimidazolium, 2-ethylimidazolium, and other imidazoles; dimethyloctylamine, dimethyldecylamine, dimethyllaurylamine, dimethyltetradecylamine, dimethylpalmitoylamine, dimethylstearylamine, dimethyldocoylamine, dimethyldodecylamine, dilaurylamine, etc. Monoethylamine, methyldidecylamine, methyldioleylamine, triallylamine, triisopropanolamine, triethylamine, 3-(dibutylamino)propylamine, tri-n-octylamine, 2,4,6-tris(dimethylaminomethyl)phenol, triethanolamine, methyldiethanolamine, diazabicycloundecene and other tertiary amines; boron trifluoride ether, boron trifluoride phenol, boron trifluoride piperidine, boron trifluoride acetate, trifluoride... Lewis acids or their compounds containing boron fluoride, such as boron monoethylamine, boron trifluoride triethanolamine, and boron trifluoride monoethanolamine; amine adducts such as PN-23 or MY-24 from the Amichua series sold by Ajinomoto Co., Ltd., and FXR-1020 or FXR-1030 from the Fuji Chemical Industry Co., Ltd.; dicyandiamide, etc.

[0087] These curing agents can be used alone or in appropriate combinations of two or more. Furthermore, there are no particular limitations on the amount or conditions under which the curing agent is used; known amounts or conditions can be used as is.

[0088] In the examples described later, 2-ethyl-4-methylimidazole was used as the (C) curing catalyst in Examples 1 to 7 and Comparative Examples 1 to 7.

[0089] In this disclosure, when a free radical reaction initiator (polymerization initiator) is used as a resin component (B), such as an acrylic resin or a silicone resin, in the case of free radical polymerization of the curable composition that is the resin. There are no particular limitations on the specific initiator; typically, organic peroxides or azo initiators can be listed.

[0090] Typical examples of organic peroxides include: tert-butylperoxy-2-ethylhexanoate, tert-hexylperoxyisopropyl monocarbonate, tert-butylperoxybenzoate, tert-butylperoxyneodecanate, tert-butylperoxylaurate, tert-butylcumyl peroxide, tert-butylperoxyacetic acid ester, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, and other peroxy esters; ketone peroxides such as methyl ethyl ketone peroxide; hydrogen peroxides such as 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, and p-menthane hydroperoxide; and dialkyl peroxides such as di-tert-butyl peroxide.

[0091] Furthermore, typical azo initiators include: 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylpentanitrile), 1,1'-azobis-1-cyclohexanecarboxylonitrile, dimethyl-2,2'-azobisisobutyrate, 2-(carbamoylazo)isobutyronitrile, 2-phenylazo-4-methoxy-2,4-dimethylpentanitrile, azobis-tert-octane, azobis-tert-butane, etc.

[0092] These initiators can be used alone or in appropriate combinations of two or more. Furthermore, there are no particular limitations on the amount or conditions of use of the initiator; known amounts or conditions can be used. In this disclosure, organic peroxides are cited as more preferred initiators.

[0093] In the examples described later, in Examples 8 to 14 and Comparative Examples 8 to 13, tert-butylperoxy-2-ethylhexanoate was used as an initiator for the acrylic resin.

[0094] Furthermore, in addition to the aforementioned components ((A) silver powder and (B) resin components, as well as the curing catalyst or initiator), the conductive adhesive composition of this disclosure may also contain various additives known in the field of conductive adhesive compositions, as needed. These additives are not particularly limited, but examples include, for instance, solvents, leveling agents, antioxidants, ultraviolet absorbers, silane coupling agents, defoamers, viscosity modifiers, etc. These additives may be added to a extent that does not impair the effectiveness of this disclosure.

[0095] [Preparation and use of conductive adhesive compositions]

[0096] The method for manufacturing the conductive adhesive composition disclosed herein is not particularly limited, and methods known in the field of conductive adhesive compositions may be appropriately used. As a typical example, a method can be described that involves mixing the above-mentioned components in a predetermined proportion (by weight) and then performing slurry preparation using a known mixing apparatus. Examples of mixing apparatus include, for instance, a three-roll mill.

[0097] In the conductive adhesive composition of this disclosure, as previously described, the amount (content) of (A) silver powder is preferably relatively small. Specifically, the conductive adhesive composition of this disclosure uses (A) silver powder and (B) resin component as basic components (solid components). When the total amount of these basic components (solid components) is set to 100% by mass, the proportion of (A) silver powder can be 70% by mass or less of the solid components. Making the proportion of (A) silver powder 70% by mass or less of the solid components means that the content of (A) silver powder can be relatively reduced in the conductive adhesive composition.

[0098] Furthermore, there are no particular limitations on the method for forming the pattern as a cured adhesive layer using the conductive adhesive composition of this disclosure, and various known forming methods can be appropriately used. Typical examples include: screen printing, gravure printing, offset printing, inkjet printing, dispensing, dipping, and other printing methods. Therefore, the conductive adhesive composition of this disclosure can be used as long as it is applied to a substrate by means of a printing press or a dispensing machine.

[0099] The method for curing the conductive adhesive composition of this disclosure is not particularly limited, and known heating methods can be appropriately used depending on the type of resin component (as needed, the type of curing catalyst or initiator). In the examples described later, when preparing evaluation samples, the conductive adhesive composition is applied to a substrate and heated at 200°C for 60 minutes using a hot air dryer, or heated at 150°C for 30 seconds using a heating plate. However, the type of heater, heating temperature, or heating time can be appropriately selected depending on the conditions accompanying the use of the conductive adhesive composition. Therefore, this disclosure is by no means limited to the heating methods of these embodiments. Moreover, the method for measuring or evaluating various physical properties of the cured conductive adhesive composition is not particularly limited in this disclosure, and the methods exemplified in the examples described later can be appropriately used.

[0100] The conductive adhesive composition disclosed herein can be widely used in the formation of high-precision electrodes or wiring, or in the bonding of electronic components. Specifically, it can be suitably used, for example, for bonding solar cell modules; bonding internal or external electrodes of chip-type electronic components; and for bonding electrodes or wiring of parts used in RFID (Radio Frequency Identification), electromagnetic wave shielding, vibrator bonding, membrane switches, or electroluminescence.

[0101] Of the above applications, the conductive adhesive composition of this disclosure is particularly suitable for the field of solar cells. Specifically, the conductive adhesive composition of this disclosure is suitable, for example, for bonding solar cell modules.

[0102] Thus, the conductive adhesive composition disclosed herein only needs to have the following composition: containing (A) silver powder and (B) resin components, wherein (A) silver powder contains (a1) flake silver powder and (a2) spherical silver powder, the thickness of (a1) flake silver powder is less than 0.3 μm, the average particle size D50 is in the range of 4 to 9 μm, and the BET specific surface area is in the range of 1.5 to 2.5 m². 2 Within the range of / g, (a2) the average particle size D50 of the spherical silver powder ranges from 0.01 to 3 μm, and the BET specific surface area ranges from 0.5 to 2.5 m². 2 Within the range of / g, the tap density is less than 2g / cm³. 3 Furthermore, the proportion of the silver powder in the solid composition is less than 70% by mass.

[0103] Based on this configuration, since (a1) flake silver powder and (a2) spherical silver powder that meet predetermined conditions are used as (A) silver powder, even if the amount of (A) silver powder in the conductive adhesive composition is relatively reduced, the conductivity will not be compromised, and good electrical properties, including connection resistance, can be achieved. Moreover, since the amount of expensive (A) silver powder used can be reduced (the amount in which it is added), the high cost of the conductive adhesive composition can be suppressed or avoided.

[0104] Furthermore, in conventional conductive adhesive compositions, copper-containing powders such as copper powder or silver-coated copper powder are sometimes used as conductive powders to suppress high costs. However, the reliability of such conductive adhesive compositions is questionable due to copper oxidation and other factors. Therefore, conductive adhesive compositions using copper-containing powders tend to be unsuitable for applications requiring high reliability. In contrast, according to the above structure, since the amount (content) of silver powder (A) can be reduced without using copper-containing powder, it can be used for applications requiring high reliability.

[0105] Example

[0106] This disclosure is described in more detail with reference to embodiments and comparative examples, but the invention is not limited thereto. Various changes, modifications, and alterations can be made by those skilled in the art without departing from the scope of the invention. Furthermore, the evaluation methods for silver powder and cured products in (A) of the following embodiments are performed in the following manner.

[0107] [(A) Evaluation method for silver powder]

[0108] (1) Average particle size D50

[0109] The average particle size D50 of (a1) flake silver powder and (a2) spherical silver powder shown in Table 1 was evaluated using laser diffraction. 0.3 g of either (a1) flake silver powder or (a2) spherical silver powder was weighed into a 50 ml beaker, and 30 ml of isopropanol was added. The powder was then dispersed using an ultrasonic cleaner (AS ONE Co., Ltd., product name: USM-1) for 5 minutes. The average particle size D50 was measured and evaluated using a Microtrac particle size distribution measuring device (Nikkiso Co., Ltd., product name: Microtrac Particle Size Distribution Measuring Device 9320-HRA X-100).

[0110] (2) Evaluation of BET specific surface area

[0111] The BET specific surface areas of (a1) flake-shaped silver powder and (a2) spherical silver powder shown in Table 1 were evaluated using a surface area analyzer (QuantaChrome, product name: Monosorb). 1 g of sample of (a1) flake-shaped silver powder or (a2) spherical silver powder was fed into the surface area analyzer, and the specific surface area was determined and evaluated using the BET 1-point method based on nitrogen adsorption. Furthermore, in this BET specific surface area determination, the exhaust conditions before measurement were 60°C for 10 minutes.

[0112] (3) Evaluation of apparent density

[0113] The apparent densities of the (a1) flake silver powder or (a2) spherical silver powder shown in Table 1 were evaluated using the following formula (1). The (a1) flake silver powder or (a2) spherical silver powder was filled into a funnel and gently tapped with a metal wire as it fell into a cup below, filling the cup until it overflowed. The overflowing (a1) flake silver powder or (a2) spherical silver powder was leveled along the top of the cup with a scraper, and the apparent density was calculated and evaluated using the following formula (1).

[0114] Apparent density = (cup mass + sample mass) - cup mass / cup volume...(1)

[0115] (4) Evaluation of tap density

[0116] The tapped densities of (a1) flake silver powder or (a2) spherical silver powder shown in Table 1 were evaluated using a tapped density measuring device (manufactured by Shibayama Scientific Instruments Co., Ltd., product name: Kasa Specific Gravity Measuring Device SS-DA-2) according to the following formula (2). 15g of the (a1) flake silver powder or (a2) spherical silver powder sample was placed in a 20ml test tube and tapped 1,000 times with a drop height of 20mm. The volume (cm³) of the sample after tapping was measured using the tapped density measuring device. 3The tap density is calculated and evaluated using the following formula (2).

[0117] Tapped density = mass of sample / volume of sample after tapping...(2)

[0118] (5) Evaluation of thickness

[0119] The thickness of the (a1) flake silver powder shown in Table 1 was evaluated using a scanning electron microscope (JEM Co., Ltd., product name: JSM-5500). The (a1) flake silver powder sample was observed using a scanning electron microscope. One hundred silver particles ((a1) flake silver powder) were randomly selected from the image magnified to 20,000x, and their thickness (minor axis in the image) was measured. The thickness of these 100 silver particles was averaged to evaluate the thickness of the (a1) flake silver powder.

[0120] [Evaluation methods for solidified products]

[0121] (1) Evaluation of conductor resistance

[0122] The conductive adhesive composition of the examples or comparative examples is printed using a printing press. Figure 2 The printed pattern 21 is shown to be printed on the alumina substrate 12. The printed pattern 21 consists of one wiring pattern 21a and five pad patterns 21d. The wiring pattern 21a has rectangular terminals 21b at both ends, and the wiring portion 21c is hairpin bent with an aspect ratio of 75. The five pad patterns 21d are arranged in a row adjacent to the wiring pattern 21a, each forming a 2mm × 2mm square.

[0123] Then, an aluminum rivet with a circular fixing surface of 4 mm in diameter is placed on the pad pattern 21d (2 mm × 2 mm) on the alumina substrate 12. For the alumina substrate 12 with the rivet, a hot air dryer is used to heat it at 200°C for 60 minutes in Examples 1 to 7 and Comparative Examples 1 to 7, and a heating plate is used to heat it at 150°C for 30 seconds in Examples 8 to 14 and Comparative Examples 8 to 13, so that the conductive adhesive composition (printed pattern 21) is cured (formation of cured adhesive layer), and a test piece for evaluating conductivity and adhesive strength is obtained.

[0124] The conductivity of the cured adhesive layer was evaluated using the volume resistivity of the wiring pattern 21a in the aforementioned test piece. Specifically, the film thickness of the wiring pattern 21a was measured using a surface roughness meter (Salficom 480A manufactured by Tokyo Seimitsu Co., Ltd.), and the resistance was measured using a digital multimeter (R6551 manufactured by Advantage Co., Ltd.). Based on these film thicknesses, resistances, and the aspect ratio of the wiring portion 21c, the volume resistivity (Ω·cm) of the wiring pattern 21a was calculated. This volume resistivity was then evaluated as the resistance value (conductor resistance) of the cured adhesive layer.

[0125] (2) Evaluation method of connection resistance

[0126] like Figure 3 As shown, the conductive adhesive composition of the examples or comparative examples was applied to a tin-plated (Sn) substrate 31 using a dispensing machine with a diameter of 2.5 mm to form an adhesive layer 32. Then, gold-plated rivets 33 with circular fixing surfaces having a diameter of 5 mm were deposited on the adhesive layer 32. At this time, a 200 μm thick polyimide film was used as a spacer to set the thickness of the adhesive layer to 200 μm. Then, in Examples 1 to 7 and Comparative Examples 1 to 7, the tin-plated substrate 31 was heated to 200°C for 60 minutes using a hot air dryer; in Examples 8 to 14 and Comparative Examples 8 to 13, the tin-plated substrate 31 was heated to 150°C for 30 seconds using a heating plate to cure the adhesive layer 32 and form a cured layer. Based on this, a sample 30 for evaluating the connection resistance was prepared.

[0127] In the evaluation sample 30, the resistance between the tin-plated substrate 31 and the gold-plated rivet 33 was measured using a resistance meter 34 (digital multimeter, manufactured by Advantage Co., Ltd., product name: R6551) as the connection resistance of the cured layer. If the measured connection resistance is less than 0.03Ω, it is rated "A"; if it is 0.03Ω or more but less than 0.05Ω, it is rated "B"; and if it is 0.05Ω or more, it is rated "C".

[0128] (3) Evaluation of bond strength

[0129] The adhesive strength of the cured adhesive layer was evaluated by assessing the adhesion of the rivet to the pad pattern 21d in the test piece described in (1) for evaluating conductor resistance. Specifically, a shear force was applied to the rivet mounted on the pad pattern 21d in the horizontal direction, and the strength of the rivet when it detached from the pad pattern 21d was measured. The adhesive strength of the cured adhesive layer was evaluated by assigning a strength of 10 MPa as “A”, a strength of 5 MPa or more but less than 10 MPa as “B”, and a strength of less than 5 MPa as “C”.

[0130] [(A) Silver powder]

[0131] In the conductive adhesive compositions of the examples or comparative examples, the five types of (a1) flake silver powder and the four types of (a2) spherical silver powder shown in Table 1 were appropriately combined to form (A) silver powder. Furthermore, in each example or comparative example, the numbers shown in Table 1 were used to designate each (A) silver powder.

[0132] [Table 1]

[0133]

[0134] [(B) Resin composition, (C) Curing catalyst, (D) Initiator]

[0135] In the conductive adhesive compositions of the examples or comparative examples, the seven resins shown in Table 2 were appropriately combined as resin component (B). Furthermore, the curing catalyst (C) or initiator (D) shown in Table 2 was used to cure these resins. Additionally, in each example or comparative example, similar to the silver powder in (A), the numbers shown in Table 2 were used to label each resin, curing catalyst, or initiator.

[0136] [Table 2]

[0137]

[0138] (Example 1)

[0139] Select flake silver powder (a1) with number A-01 and spherical silver powder (a2) with number A-11 from Table 1 as (A) silver powder, select epoxy resin (B-01), epoxy resin (B-02), and phenolic resin (B-03) from Table 2 as (B) resin components, and select curing catalyst (C) with number C-01 from Table 2. Mix these components according to the composition (mixing ratio) shown in Table 3.

[0140] In addition, in Table 3 (and Tables 4 to 6 described below), the total proportion of the two types of (A) silver powder is 100% by mass. In Example 1, the mass ratio of (a1) flake silver powder to (a2) spherical silver powder ((a1) / (a2)) is 50 / 50.

[0141] Furthermore, in Table 3 (and Tables 4 to 6 described below), the composition of resin component (B) is a total of 100% by mass of the three resins. In Example 1, the mass ratio (B-01 / B-02 / B-03) of epoxy resin B-01, epoxy resin B-02, and phenolic resin B-03 is 50 / 20 / 25. Moreover, in Table 3 (and Table 4 described below), the amount of curing catalyst (C) is 1 part by mass relative to the total 100 parts by mass of resin component (B).

[0142] Then, in Table 3 (and Tables 4 to 6 described below), the mixing ratio of (A) silver powder to (B) resin component is expressed by mass ratio. In Example 1, the mass ratio of the total amount of (A) silver powder to the total amount of (B) resin component (the mass ratio of solid components (A) / (B)) is 70 / 30. The same applies to the following examples or comparative examples.

[0143] The conductive adhesive composition of Example 1 was prepared by mixing components (A) to (C) according to the composition shown in Table 3 using a three-roll mill.

[0144] Using the conductive adhesive composition of Example 1, evaluation samples for conductor resistance and bonding resistance (and bond strength) were prepared as described above. Using these evaluation samples, the cured properties (conductor resistance, bonding resistance, and bond strength) of the conductive adhesive composition were evaluated according to the evaluation method described above. The results are shown in Table 3.

[0145] (Examples 2 to 4)

[0146] The conductive adhesive compositions of Examples 2 to 4 were prepared (manufactured) in the same manner as in Example 1, except that the solid component mass ratio (A) / (B) was set to 65 / 35 and (a1) flake silver powder of number A-02 was used (Example 2), or (A) silver powder of the same type was used and the solid component mass ratio (A) / (B) was set to 65 / 35 (Example 3), or (a2) spherical silver powder of number A-12 was used and the solid component mass ratio (A) / (B) was set to 65 / 35 (Example 4).

[0147] Evaluation samples were prepared using the conductive adhesive compositions of Examples 2 to 4 as described above. The cured properties of these conductive adhesive compositions were evaluated using the evaluation methods described above. The results are shown in Table 3.

[0148] (Example 5)

[0149] The conductive adhesive composition of Example 5 was prepared (manufactured) with the following conditions: the proportion of silver powder (A) was set to (a1) / (a2) = 60 / 40 and the mass ratio of solid components (A) / (B) = 60 / 40.

[0150] Evaluation samples were prepared using the conductive adhesive composition of Example 5 as described above. Using these evaluation samples, the cured properties of the conductive adhesive composition were evaluated according to the evaluation method described above. The results are shown in Table 3.

[0151] (Example 6)

[0152] The conductive adhesive composition of Example 6 was prepared (manufactured) with the following steps: the proportion of silver powder (A) was set to (a1) / (a2) = 60 / 40 and the mass ratio of solid components (A) / (B) = 50 / 50.

[0153] Using the conductive adhesive composition of Example 6, evaluation samples were prepared as described above. Using these evaluation samples, the cured properties of the conductive adhesive composition were evaluated according to the evaluation method described above. The results are shown in Table 3.

[0154] (Example 7)

[0155] The conductive adhesive composition of Example 7 was prepared (manufactured) in the same manner as in Example 1, except that the mass ratio of solid components (A) / (B) was set to 40 / 60.

[0156] Using the conductive adhesive composition of Example 7, evaluation samples were prepared as described above. Using these evaluation samples, the cured properties of the conductive adhesive composition were evaluated according to the evaluation method described above. The results are shown in Table 3.

[0157] [Table 3]

[0158]

[0159] (Comparative Example 1, Comparative Example 2)

[0160] The conductive adhesive compositions of Comparative Example 1 or Comparative Example 2 were prepared (manufactured) in the same manner as in Example 1, except that either the spherical silver powder (a2) of No. A-13 (Comparative Example 1) or the spherical silver powder (a2) of No. A-14 (Comparative Example 2) was used.

[0161] Using the conductive adhesive compositions of Comparative Example 1 or Comparative Example 2, evaluation samples were prepared as described above. Using these evaluation samples, the cured properties of the conductive adhesive compositions were evaluated according to the evaluation method described above. The results are shown in Table 4.

[0162] (Comparative Example 3)

[0163] The conductive adhesive composition of Comparative Example 3 was prepared (manufactured) in the same manner as in Example 2, except that the solid component mass ratio (A) / (B) = 70 / 30 and spherical silver powder (a2) with number A-13 was used.

[0164] Using the conductive adhesive composition of Comparative Example 3, evaluation samples were prepared as described above. Using these evaluation samples, the cured properties of the conductive adhesive composition were evaluated according to the evaluation method described above. The results are shown in Table 4.

[0165] (Comparative Example 4, Comparative Example 5)

[0166] The conductive adhesive compositions of Comparative Example 4 or Comparative Example 5 were prepared (manufactured) in the same manner as in Example 1, except that either (a1) flake silver powder of No. A-03 (Comparative Example 4) or (a1) flake silver powder of No. A-04 (Comparative Example 5) was used.

[0167] Using the conductive adhesive compositions of Comparative Example 4 or Comparative Example 5, evaluation samples were prepared as described above. Using these evaluation samples, the cured properties of the conductive adhesive compositions were evaluated according to the evaluation method described above. The results are shown in Table 4.

[0168] (Comparative Example 6)

[0169] Instead of using (a2) spherical silver powder, two types of (a1) flake silver powder, numbered A-01 and A-05, were used. Otherwise, the conductive adhesive composition of Comparative Example 6 was prepared (manufactured) in the same manner as in Example 1.

[0170] Using the conductive adhesive composition of Comparative Example 6, evaluation samples were prepared as described above. Using these evaluation samples, the cured properties of the conductive adhesive composition were evaluated according to the evaluation method described above. The results are shown in Table 4.

[0171] (Comparative Example 7)

[0172] The conductive adhesive composition of Comparative Example 7 was prepared (manufactured) in the same manner as Comparative Example 5, except that the mass ratio of solid components (A) / (B) was set to 90 / 10.

[0173] Using the conductive adhesive composition of Comparative Example 7, evaluation samples were prepared as described above. Using these evaluation samples, the cured properties of the conductive adhesive composition were evaluated according to the evaluation method described above. The results are shown in Table 4.

[0174] [Table 4]

[0175]

[0176] (Examples 8 to 11)

[0177] Acrylic resins B-11, B-12, B-13, and B-14 from Table 2 were selected as resin component (B), and initiator D-01 from Table 2 was selected as initiator (D). These components were formulated according to the composition (ratio) shown in Table 5. Except for these components, the conductive adhesive composition of Example 8 was prepared (manufactured) in the same manner as in Example 1.

[0178] Furthermore, in Example 8, as shown in Table 5, the mass ratio (B-11 / B-12 / B-13 / B-14) of the acrylic resins numbered B-11, B-12, B-13, and B-14 is 15 / 28 / 2 / 55. Moreover, in Table 5 (and Table 6 described below), the amount of initiator (D) is 1 part by mass relative to a total of 100 parts by mass of resin component (B).

[0179] Evaluation samples were prepared using the conductive adhesive composition of Example 8 as described above. Using these evaluation samples, the cured properties of the conductive adhesive composition were evaluated according to the evaluation method described above. The results are shown in Table 5.

[0180] (Examples 9 to 11)

[0181] The conductive adhesive compositions of Examples 9 to 11 were prepared (manufactured) with the following methods: the solid component mass ratio (A) / (B) = 65 / 35, and either (Example 9) spherical silver powder (a2) of No. A-12 was used, or (Example 10) flake silver powder (a1) of No. A-02 was used, or (Example 11) was used with both flake silver powder (a1) of No. A-02 and spherical silver powder (a2) of No. A-12 was used.

[0182] Evaluation samples were prepared using the conductive adhesive compositions of Examples 9 to 11 as described above. The cured properties of the conductive adhesive compositions were evaluated using these evaluation samples according to the evaluation method described above. The results are shown in Table 5.

[0183] (Example 12)

[0184] The conductive adhesive composition of Example 12 was prepared (manufactured) with the following steps: the proportion of silver powder (A) was set to (a1) / (a2) = 60 / 40 and the mass ratio of solid components (A) / (B) = 50 / 50.

[0185] Evaluation samples were prepared using the conductive adhesive composition of Example 12 as described above. Using these evaluation samples, the cured properties of the conductive adhesive composition were evaluated according to the evaluation method described above. The results are shown in Table 5.

[0186] (Example 13)

[0187] The conductive adhesive composition of Example 13 was prepared (manufactured) with the following steps: the proportion of silver powder (A) was set to (a1) / (a2) = 55 / 45 and the mass ratio of solid components (A) / (B) = 40 / 60.

[0188] Using the conductive adhesive composition of Example 13, evaluation samples were prepared as described above. Using these evaluation samples, the cured properties of the conductive adhesive composition were evaluated according to the evaluation method described above. The results are shown in Table 5.

[0189] (Example 14)

[0190] The conductive adhesive composition of Example 14 was prepared (manufactured) with the following conditions: the proportion of silver powder (A) was set to (a1) / (a2) = 60 / 40, and the mass ratio of solid components (A) / (B) was set to (A) / (B) = 30 / 70.

[0191] Using the conductive adhesive composition of Example 14, evaluation samples were prepared as described above. Using these evaluation samples, the cured properties of the conductive adhesive composition were evaluated according to the evaluation method described above. The results are shown in Table 5.

[0192] [Table 5]

[0193]

[0194] (Compare Example 8 and Compare Example 9)

[0195] The conductive adhesive compositions of Comparative Example 8 or Comparative Example 9 were prepared (manufactured) in the same manner as in Example 8, except that either (a2) spherical silver powder of No. A-14 (Comparative Example 8) or (a2) spherical silver powder of No. A-15 (Comparative Example 9) was used.

[0196] Using the conductive adhesive compositions of Comparative Example 8 or Comparative Example 9, evaluation samples were prepared as described above. Using these evaluation samples, the cured properties of the conductive adhesive compositions were evaluated according to the evaluation method described above. The results are shown in Table 6.

[0197] (Comparative Example 10)

[0198] The conductive adhesive composition of Comparative Example 10 was prepared (manufactured) in the same manner as in Example 10, except that the mass ratio of solid components (A) / (B) was set to 70 / 30 and spherical silver powder (a2) of number A-14 was used.

[0199] Using the conductive adhesive composition of Comparative Example 10, evaluation samples were prepared as described above. Using these evaluation samples, the cured properties of the conductive adhesive composition were evaluated according to the evaluation method described above. The results are shown in Table 6.

[0200] (Comparative Examples 11 to 13)

[0201] The conductive adhesive compositions of Comparative Examples 11 to 13 were prepared (manufactured) in the same manner as in Example 8, except that the solid component mass ratio (A) / (B) was set to 90 / 10 and the solid component (A) / (B) was used.

[0202] Using the conductive adhesive compositions of Comparative Examples 11 to 13, evaluation samples were prepared as described above. Using these evaluation samples, the cured properties of the conductive adhesive compositions were evaluated according to the evaluation method described above. The results are shown in Table 6.

[0203] [Table 6]

[0204]

[0205] (Comparison of Examples and Comparative Examples)

[0206] The results from Examples 1 to 7 and Examples 8 to 14 clearly show that by using (a1) flake silver powder and (a2) spherical silver powder that meet the predetermined properties as (A) silver powder, the resulting cured product can achieve good conductor resistance and connection resistance as well as good adhesive strength.

[0207] In particular, a comparison of the results of Examples 1 to 7 with the results of Examples 8 to 14 clearly shows that, regardless of whether the type of resin component (B) is epoxy resin and phenolic resin or whether the type of resin component (B) is a variety of acrylic resins, the resulting cured product can achieve good electrical properties and adhesive strength.

[0208] In contrast, a comparison of the results of Examples 1 to 4 with the results of Comparative Examples 1 to 3, or a comparison of the results of Examples 8 to 11 with the results of Comparative Examples 8 to 10, clearly shows that even if (a1) the flake silver powder satisfies the predetermined physical properties, when (a2) the spherical silver powder does not satisfy the predetermined physical properties, the electrical properties (conductor resistance and connection resistance) become insufficient.

[0209] Furthermore, a comparison of the results of Examples 1 to 4 with the results of Comparative Examples 4 and 5, or a comparison of the results of Examples 8 to 11 with the results of Comparative Examples 11 and 12, clearly shows that even if the (a2) spherical silver powder meets the predetermined physical properties, when the (a1) flake silver powder does not meet the predetermined physical properties, the conductor resistance is particularly prone to become insufficient, and the connection resistance may also become insufficient.

[0210] Furthermore, the results from Comparative Example 7 or Comparative Example 13 show that even when the (a1) flake silver powder does not meet the predetermined physical properties, good electrical properties can be achieved by increasing the content of (A) silver powder. However, the results from Comparative Example 7 or Comparative Example 13 show that even with good electrical properties, it is difficult to improve the adhesive strength. This can be considered to be the same when the (a2) spherical silver powder does not meet the predetermined physical properties.

[0211] Furthermore, a comparison of the results of Examples 1 to 4 with the results of Examples 5 and 6, or a comparison of the results of Examples 8 to 11 with the results of Examples 12 to 14, clearly shows that the mixing ratio (a1) flake silver powder to (a2) spherical silver powder that satisfies the predetermined physical properties is not limited to a narrow range. These results indicate that, at least when the mixing ratio of (a1) flake silver powder to (a2) spherical silver powder is close to (a1) / (a2) = 1 / 1, and is within the range of 20 / 80 to 80 / 20, good electrical properties and good adhesive strength can be easily achieved.

[0212] Furthermore, a comparison of the results from Examples 1 to 7 or Examples 8 to 14 clearly shows that good electrical properties and good adhesive properties can be achieved by keeping the solid component mass ratio (A) / (B) within a wide range of 70 / 30 to 30 / 70. These results indicate that when the total amount of the solid component (A) silver powder and the total amount of the resin component (B) in the conductive adhesive composition are set to a total of 100% by mass, the proportion of (A) silver powder can be reduced to 70% by mass or less.

[0213] Furthermore, the present invention is not limited to the embodiments described herein. Various changes can be made within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments and multiple variations are also included in the technical scope of the present invention.

[0214] Industrial practicality

[0215] This invention is widely applicable in the fields of electrical machinery or electronic machinery, particularly in areas where materials need to be electrically bonded. Typically, it is especially suitable for applications such as the manufacture of solar cell modules.

[0216] Symbol Explanation

[0217] 10: Resin composition

[0218] 11: Flake silver powder

[0219] 12: Flake silver powder

[0220] 13: Spherical silver powder

[0221] 20: Evaluation Sample

[0222] 31: Tin plated substrate

[0223] 32: Adhesive layer (or cured layer)

[0224] 33: Gold-plated rivets

[0225] 34: Resistance meter

Claims

1. A conductive adhesive composition, characterized in that, It contains (A) silver powder and (B) resin components. The silver powder (A) contains (a1) flake-shaped silver powder and (a2) spherical silver powder. The (a1) flake silver powder has a thickness of less than 0.3 μm, an average particle size D50 in the range of 4 to 9 μm, and a BET specific surface area in the range of 1.5 to 2.5 m². 2 Within the range of / g, The average particle size D50 of the (a2) spherical silver powder is in the range of 0.01 to 3 μm, and the BET specific surface area is in the range of 0.5 to 2.5 m². 2 Within the range of / g, the tap density is less than 2g / cm³. 3 ; Furthermore, the proportion of silver powder in the solid composition is less than 70% by mass.

2. The conductive adhesive composition of claim 1, wherein, The (a1) flake silver powder and the (a2) spherical silver powder are compounded in a mass ratio ranging from 20 / 80 to 80 / 20.

3. The conductive adhesive composition of claim 1, wherein, The resin component (B) is a thermosetting resin and its curing agent or reaction initiator.

4. The conductive adhesive composition of claim 3, wherein, The thermosetting resin is at least one resin selected from the group consisting of epoxy resin, phenolic resin, acrylic resin, polyurethane resin, and silicone resin.

5. The conductive adhesive composition according to any one of claims 1 to 4, wherein, It is used by applying it to a substrate using a printing press or a dispensing machine.

6. The conductive adhesive composition according to any one of claims 1 to 4, wherein, The conductive adhesive composition is used for bonding electronic components.

7. The conductive adhesive composition of claim 6, wherein, The electronic component is a solar cell module.

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