Conductive adhesive, conductive sheet and dicing die-boding film

Abstract

The conductive adhesive of the present invention comprises an elastomer and metal particles, wherein the metal particles include copper particles, and the molar concentration of carboxyl groups in the conductive adhesive is less than 2.0 μmol / g.

Description

[Technical Field]

[0001] This invention relates to a conductive adhesive, a conductive sheet, and a crystal-cut bonding film. [Previous Technology]

[0002] Previously, as a method for attaching semiconductor elements (semiconductor wafers) to a bonding body such as a metal lead frame in the manufacture of semiconductor devices (die-cutter bonding method), a method using conductive sheets is known (for example, Patent Document 1 below).

[0003] According to Patent Document 1 below, this conductive sheet is formed by: obtaining a conductive adhesive composition obtained by suspending metal particles and resin in an organic solvent; applying the conductive adhesive composition onto a substrate and drying it to allow volatile components such as the organic solvent to evaporate, thereby forming the sheet. Furthermore, the conductive adhesive composition typically includes an elastomer as the resin to give the conductive sheet appropriate flexibility and improve its conformability to the substrate. For example, Patent Document 1 below discloses that a conductive sheet is obtained by using a conductive adhesive composition containing an epoxy-containing ethyl acrylate-butyl acrylate-acrylonitrile copolymer belonging to acrylic resin as the elastomer. [Prior Art Documents] [Patent Documents]

[0004] [Patent Document] Japanese Patent Application Publication No. 2019-21813 [Summary of the Invention]

[0005] [The problem the invention aims to solve]

[0006] On the other hand, the viscosity of the conductive adhesive composition described above sometimes increases over time. Furthermore, if the viscosity of the conductive adhesive composition increases, it becomes difficult to apply the conductive adhesive composition to the substrate in order to obtain the conductive sheet. That is, the conductive adhesive composition sometimes becomes difficult to work with. Also, if it becomes difficult to apply the conductive adhesive composition to the substrate, it is difficult to achieve a uniform thickness for the conductive sheet formed on the substrate.

[0007] Furthermore, even if a conductive adhesive is produced by directly coating the conductive adhesive composition onto a substrate such as a metal lead frame (e.g., coating it in layers) without producing a conductive sheet and then drying it, if, as mentioned above, the viscosity of the conductive adhesive composition is high, it becomes difficult to coat, which is not ideal.

[0008] However, the suppression of the time-dependent increase in viscosity of the above-mentioned conductive adhesive composition has not been adequately studied.

[0009] Therefore, the object of the present invention is to provide a conductive adhesive capable of suppressing the time-dependent increase in viscosity of the above-mentioned conductive adhesive composition, a conductive sheet formed from the conductive adhesive, and a crystalline adhesive film having the conductive sheet. [Technical Means for Solving the Problem]

[0010] The conductive adhesive of the present invention comprises an elastomer and metal particles, wherein the metal particles include copper particles, and the molar concentration of carboxyl groups in the conductive adhesive is less than 2.0 μmol / g.

[0011] The conductive sheet of the present invention is formed from the above-mentioned conductive adhesive.

[0012] The diced adhesive film of the present invention comprises: a diced strip obtained by depositing an adhesive layer on a substrate layer, and a conductive sheet deposited on the adhesive layer of the diced strip, wherein the conductive sheet is the aforementioned conductive sheet.

Implementation Method

[0014] Hereinafter, one embodiment of the present invention will be described.

[0015] [Conductive Adhesive] The conductive adhesive of this embodiment includes an elastomer and metal particles. In the conductive adhesive of this embodiment, the metal particles include copper particles. In the conductive adhesive of this embodiment, the molar concentration of carboxyl groups is 2.0 μmol / g or less.

[0016] When the conductive adhesive of this embodiment does not contain resin other than elastomer, or when it contains resin other than elastomer but the resin is other than resin containing Brinzyl acid (e.g., phenolic resin), the molar concentration of carboxyl groups in the conductive adhesive can be determined as follows: For a sample taken from the conductive adhesive, the acid value of the conductive adhesive is evaluated according to JIS K 0070-1992 (potential difference titration method), and the molar concentration of carboxyl groups is calculated based on the acid value, thereby determining (evaluation method 1). Furthermore, the acid value of the conductive adhesive described above can be evaluated as follows. (1) Phenolphthalein solution is added as an indicator to a mixed solvent obtained by mixing diethyl ether and ethanol at a volume ratio of 4:1 (volume of diethyl ether:volume of ethanol), and then the mixed solvent containing the indicator is neutralized with 0.1 mol / L potassium hydroxide ethanol solution (titrile). Therefore, the coefficient f of the 0.1 mol / L potassium hydroxide ethanol solution used as the titrant is determined. (2) Approximately 5 g of the sample (conductive adhesive) is accurately weighed into a beaker, and the above mixed solvent is added to the beaker. The sample is stirred and dissolved in the mixed solvent on a panel heater (80°C). (3) The above mixed solution containing the sample is titrated using a 0.1 mol / L potassium hydroxide ethanol solution (titer). Then, the acid value of the sample is determined using the following formula (1).

[0017] …(1) Furthermore, in the above formula (1), B is the amount (mL) of 0.1 mol / L potassium hydroxide ethanol solution required for potentiometric titration, f is the coefficient of 0.1 mol / L potassium hydroxide ethanol solution, and S is the amount of sample taken (g).

[0018] On the other hand, when the conductive adhesive of this embodiment includes a resin other than an elastomer and the resin is a resin containing Brønsted acid (e.g., a phenolic resin), the molar concentration of carboxyl groups in the conductive adhesive can be determined based on the mixing ratio of the elastomer in the conductive adhesive after the acid value of the elastomer resin is determined in the same manner as above before the elastomer resin is mixed (Evaluation Method 2). Furthermore, when the conductive adhesive of this embodiment includes a resin other than an elastomer and the resin is a resin containing Brønsted acid (e.g., a phenolic resin), the molar concentration of carboxyl groups in the conductive adhesive can also be determined based on the mass ratio of the elastomer in the conductive adhesive and the acid value of the conductive adhesive (Evaluation Method 3). In this case, the acid value of the conductive adhesive can be determined by performing IR analysis or NMR analysis on the conductive adhesive. Specifically, the acid value of the aforementioned conductive adhesive can be determined by converting the molar ratio of functional groups such as carboxyl groups based on the spectra obtained from IR or NMR analysis of the aforementioned conductive adhesive.

[0019] The conductive adhesive of this embodiment can be obtained by directly coating a conductive adhesive composition obtained by suspending elastomer and metal particles in an organic solvent onto a substrate such as a metal lead frame (for example, after coating in layers) and then drying it. That is, the conductive adhesive of this embodiment is obtained by causing volatile components such as organic solvents to evaporate from the above-mentioned conductive adhesive composition.

[0020] As the elastomer described above, it is preferable to use an elastomer with an acid value of 1 mgKOH / g or less. By using an elastomer with an acid value of 1 mgKOH / g or less, it becomes easier to adjust the molar concentration of the carboxyl group to 2.0 μmol / g or less in the conductive adhesive of this embodiment. Furthermore, the acid value of the elastomer is most preferably 0 mgKOH / g. The acid value of the elastomer can be evaluated according to JIS K 0070-1992 (potential difference titration method). Specifically, it can be evaluated as follows: (1) Phenolphthalein solution is added as an indicator to a mixed solvent obtained by mixing diethyl ether and ethanol at a volume ratio of 4:1 (volume of diethyl ether:volume of ethanol), and then the mixed solvent containing the indicator is neutralized with a 0.1 mol / L potassium hydroxide ethanol solution (titrate). Herein, the coefficient f of the 0.1 mol / L potassium hydroxide ethanol solution as the titrate is determined. (2) Accurately weigh approximately 5 g of the sample (elastomer) into a beaker, add the above mixed solvent to the beaker, and stir the sample in the mixed solvent on a panel heater (80°C) to dissolve it. (3) Perform a potentiometric titration on the above mixed solution containing the sample using a 0.1 mol / L potassium hydroxide ethanol solution (titrile). Then, determine the acid value of the sample using the following formula (1).

[0021] …(1) Furthermore, in the above formula (1), B is the amount (mL) of 0.1 mol / L potassium hydroxide ethanol solution required for potentiometric titration, f is the coefficient of 0.1 mol / L potassium hydroxide ethanol solution, and S is the amount of sample taken (g).

[0022] Examples of such elastomers include butyl rubber, isoprene rubber, and chloroprene rubber. Examples of such elastomers include ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers, ethylene-acrylate copolymers, and acrylic resins obtained using monomers with fewer carboxyl residues. Among these, acrylic resins are preferred from the viewpoint of easily ensuring the bonding reliability of the conductive adhesive due to their low ionic impurities and high heat resistance. Only one type of elastomer may be used, or two or more may be used in combination. Among these, acrylic resins are preferred.

[0023] Preferably, the above-mentioned acrylic resin is a polymer containing monomer units derived from (meth)acrylates as the most abundant monomer units by mass proportion. Examples of (meth)acrylates include, for example, alkyl (meth)acrylates, cycloalkyl (meth)acrylates, and aryl (meth)acrylates. The above-mentioned acrylic resin may also contain monomer units derived from other components that can copolymerize with (meth)acrylates. Examples of such other components include, for example, anhydride monomers, hydroxyl-containing monomers, glycidyl-containing monomers, sulfonic acid-containing monomers, phosphate-containing monomers, acrylamide, acrylonitrile, and other monomers containing functional groups.

[0024] The content of functional groups such as glycidyl groups and amino groups in the above-mentioned acrylic resin is preferably below a certain value. Specifically, the content of the above-mentioned functional groups in the above-mentioned acrylic resin is preferably below 20 μmol / g, and more preferably below 5 μmol / g.

[0025] Regarding the conductive adhesive of this embodiment, based on the total mass of the conductive adhesive, it is preferable to contain 2% by mass or more, and more preferably 4% by mass or more of the aforementioned elastomer. Furthermore, regarding the conductive adhesive of this embodiment, based on the total mass of the conductive adhesive, it is preferable to contain 20% by mass or less, and more preferably 10% by mass or less of the aforementioned elastomer.

[0026] The aforementioned copper particles are composed of copper and other elements (metallic elements, etc.) contained as unavoidable impurities. At least a portion of the surface of the aforementioned copper particles may also be plated with a metal other than copper, such as gold or silver. That is, a coating layer (hereinafter also referred to as a metal coating layer) composed of the aforementioned metal can be formed on at least a portion of the surface of the aforementioned copper particles. As described above, the formation of a metal coating layer on at least a portion of the surface of the aforementioned copper particles further improves the conductivity of the aforementioned conductive adhesive. The metal forming the aforementioned metal coating layer is preferably silver. That is, a silver coating layer is preferably formed on at least a portion of the surface of the aforementioned copper particles.

[0027] At least a portion of the surface of the copper particles can also be treated with a surface treatment agent (e.g., a silane coupling agent). Examples of such surface treatment agents include fatty acid-based surface treatment agents, amine-based surface treatment agents, and epoxy-based surface treatment agents. That is, a coating layer (hereinafter also referred to as a treatment agent coating layer) composed of the aforementioned surface treatment agent can be formed on at least a portion of the surface of the copper particles. As described above, the formation of the treatment agent coating layer on at least a portion of the surface of the copper particles improves the affinity between the copper particles and the resin contained in the conductive adhesive. This makes the copper particles easier to disperse in the conductive adhesive.

[0028] Furthermore, when a coating is formed on the surface of the copper particles as described above, although the coating is usually formed in a way that covers the entire surface, even in this case, the coating will have defects. Therefore, in most cases, a portion of the copper particles will be exposed on the surface.

[0029] The shape of the copper particles can be, for example, sheet-like, needle-like, filamentous, spherical, or flat (including scale-like) particles. Among these, spherical particles are preferred. By making the copper particles spherical, the dispersibility of the copper particles in the conductive adhesive can be improved.

[0030] The conductive adhesive of this embodiment may also contain metal particles other than copper particles. Examples of metal particles other than copper particles include silver particles, gold particles, nickel particles, and aluminum particles. The conductive adhesive of this embodiment may contain only one type of metal particle other than copper particles, or it may contain two or more types. Among these, the conductive adhesive of this embodiment preferably contains silver particles as a metal particle other than copper particles. By including silver particles in the conductive adhesive of this embodiment, the thermal conductivity and electrical conductivity of the conductive adhesive can be further improved.

[0031] The aforementioned silver particles are composed of silver and other elements (metallic elements, etc.) included as unavoidable impurity elements. At least a portion of the surface of the aforementioned silver particles may also be treated with a surface treatment agent (e.g., a silane coupling agent). Examples of such surface treatment agents include fatty acid-based surface treatment agents, amine-based surface treatment agents, and epoxy-based surface treatment agents. That is, a coating layer (hereinafter also referred to as a treatment agent coating layer) composed of the aforementioned surface treatment agent and covering the surface may be formed on at least a portion of the surface of the aforementioned silver particles. As described above, the formation of the treatment agent coating layer on at least a portion of the surface of the aforementioned silver particles improves the affinity between the silver particles and the resin contained in the aforementioned conductive adhesive. This facilitates the dispersion of the aforementioned silver particles in the aforementioned conductive adhesive.

[0032] The shape of the silver particles can be, for example, flake-shaped, needle-shaped, filament-shaped, spherical, or flat (including scale-like) particles. Among these, spherical particles are preferred. By making the shape of the silver particles spherical, the dispersibility of the silver particles in the conductive adhesive can be improved.

[0033] The conductive adhesive of this embodiment preferably contains 70% by mass or more, and more preferably 80% by mass or more of the aforementioned metal particles, based on the total mass of the conductive adhesive. Furthermore, the conductive adhesive of this embodiment preferably contains 95% by mass or less, and more preferably 90% by mass or less of the aforementioned metal particles, based on the total mass of the conductive adhesive. Moreover, when the conductive adhesive of this embodiment contains metal particles other than the aforementioned copper particles, the conductive adhesive of this embodiment preferably contains 20% by mass or more, and more preferably 25% by mass or more of the aforementioned copper particles, based on the total mass of the conductive adhesive. Furthermore, when the conductive adhesive of this embodiment contains metal particles other than the aforementioned copper particles, the conductive adhesive of this embodiment preferably contains 70% by mass or less, and more preferably 65% ​​by mass or less of the aforementioned copper particles, based on the total mass of the conductive adhesive. Furthermore, when the conductive particles of this embodiment include metal particles other than the aforementioned copper particles, the mass percentage of the copper particles in the metal particles is preferably 20% by mass or more, and more preferably 25% by mass or more. Also, when the conductive adhesive of this embodiment includes metal particles other than the aforementioned copper particles, the mass percentage of the copper particles in the metal particles is preferably 90% by mass or less, and more preferably 80% by mass or less.

[0034] The conductive adhesive of this embodiment may also include a thermosetting resin as a resin other than an elastomer. Examples of thermosetting resins include epoxy resin, phenolic resin, amino resin, unsaturated polyester resin, polyurethane resin, polysiloxane resin, and thermosetting polyimide resin. Among these, epoxy resin is preferred.

[0035] Examples of epoxy resins include: bisphenol A type, bisphenol F type, bisphenol S type, brominated bisphenol A type, hydrogenated bisphenol A type, bisphenol AF type, biphenyl type, naphthalene type, fluorene type, phenolic varnish type, cresol varnish type, o-cresol varnish type, trihydroxyphenylmethane type, tetraphenol ethane type, hydantoin type, triglycidyl isocyanurate type, and glycidylamine type epoxy resins. Among these, it is preferable to use at least one of bisphenol A type epoxy resin and cresol varnish type epoxy resin, and more preferably, a combination of bisphenol A type epoxy resin and cresol varnish type epoxy resin. Examples of bisphenol A type epoxy resins include: aliphatic modified bisphenol A type epoxy resin.

[0036] In the case where the conductive adhesive of this embodiment includes epoxy resin as the above-mentioned thermosetting resin, the conductive adhesive of this embodiment preferably includes phenolic resin as the curing agent of the above-mentioned epoxy resin.

[0037] Examples of phenolic resins used as curing agents for epoxy resins include: phenolic varnish-type phenolic resins, soluble phenolic resins, biphenyl-type phenolic resins, and polyhydroxystyrene such as poly(p-hydroxystyrene). Among the above-mentioned phenolic resins, biphenyl-type phenolic resins are preferred.

[0038] When the conductive adhesive of this embodiment includes a thermosetting resin other than an elastomer, the conductive adhesive of this embodiment preferably contains 1% by mass or more, and more preferably 3% by mass or more of the aforementioned thermosetting resin, based on the total mass of the conductive adhesive. Furthermore, when the conductive adhesive of this embodiment includes a thermosetting resin other than an elastomer, the conductive adhesive of this embodiment preferably contains 20% by mass or less, and more preferably 15% by mass or less of the aforementioned thermosetting resin, based on the total mass of the conductive adhesive.

[0039] When the conductive adhesive of this embodiment includes a thermosetting resin, from the viewpoint of ensuring sufficient curing reaction of the thermosetting resin or increasing the curing reaction rate, a thermosetting catalyst may also be included. Examples of thermosetting catalysts include imidazole compounds, triphenylphosphine compounds, amine compounds, phosphorus compounds, and trihaloborane compounds. Phosphorus compounds are preferred as thermosetting catalysts, and tetraphenylphosphonium tetra(4-methylphenyl)borate (TPP-MK) is particularly preferred among these phosphorus compounds.

[0040] The conductive adhesive of this embodiment may also contain one or more other components as needed. Examples of other components include: filler dispersants, flame retardants, silane coupling agents, and ion trapping agents.

[0041] Regarding the reason why the viscosity increase of the conductive adhesive composition used to obtain the conductive adhesive can be suppressed by adopting the structure of the conductive adhesive of this embodiment, the inventors have made the following considerations.

[0042] It is believed that when the conductive adhesive composition comprises an elastomer and copper particles, and the elastomer has carboxyl groups (-COOH) and the copper particles have exposed copper surfaces, the carboxyl groups in the conductive composition are bound to the surface of the copper particles. That is, it is believed that the elastomer is bound to the copper particles via the carboxyl groups. Therefore, it is believed that the more carboxyl groups in the elastomer, the greater the degree of binding of the elastomer to the copper particles via the carboxyl groups over time, and the viscosity of the conductive adhesive composition will increase over time. That is, it is believed that the more carboxyl groups present in the conductive adhesive composition, the more the viscosity of the conductive adhesive composition increases over time. However, in the conductive adhesive of this embodiment, the molar concentration of carboxyl groups is an extremely low value of 2.0 μmol / g or less, so it can be considered that the amount of carboxyl groups present in the conductive adhesive composition is extremely small. Therefore, the inventors believe that, in this embodiment, the degree of constraint of the elastomer via the carboxyl groups on the copper particles in the conductive adhesive composition is mitigated, thereby suppressing the time-dependent increase in the viscosity of the conductive adhesive composition. Furthermore, as described above, the time-dependent increase in the viscosity of the conductive adhesive composition is suppressed in this embodiment, thereby also suppressing gelation of the conductive adhesive composition as shown in the examples described later. Moreover, as described above, the degree of constraint of the elastomer via the carboxyl groups on the copper particles in the conductive adhesive composition is mitigated in this embodiment, therefore, compared to conductive compositions with a high degree of constraint of the elastomer on the copper particles, it is impossible to place the copper particles in a close position, thus hindering contact between the copper particles. Therefore, the conductive adhesive of this embodiment formed from the conductive adhesive composition as described above, as shown in the examples described later, exhibits excellent thermal conductivity.

[0043] Furthermore, in this embodiment, when the conductive adhesive composition contains both an elastomer and a thermosetting resin as a resin, the elastomer and the thermosetting resin undergo phase separation in the conductive adhesive composition, forming a so-called island structure. Specifically, in the conductive adhesive composition, an island structure is formed where the domain structure formed by the thermosetting resin exists within the matrix structure formed by the elastomer. Moreover, in the conductive adhesive of this embodiment formed by the conductive adhesive composition as described above, since the molar concentration of the carboxyl groups is an extremely low value of 2.0 μmol / g or less, the domain structures in the matrix structure are configured with an appropriate size. That is, in the conductive adhesive composition, the size of the matrix structure and the size of the domain structures achieve an appropriate balance. Therefore, it can be inferred that the conductive adhesive of this embodiment, as shown in the examples described later, exhibits excellent thermal conductivity.

[0044] When the conductive adhesive of this embodiment includes a thermosetting resin, the thermal conductivity after thermosetting is preferably 1 W / m·K or more, more preferably 3 W / m·K or more, and even more preferably 10 W / m·K or more. By ensuring that the thermal conductivity after thermosetting meets the above-mentioned value range, the thermal conductivity of the conductive adhesive can be further improved. Furthermore, the upper limit of the thermal conductivity of the conductive adhesive of this embodiment after thermosetting is at most 420 W / m·K. The upper limit of the thermal conductivity of the conductive adhesive of this embodiment after thermosetting can also be 200 W / m·K. The thermal conductivity of the conductive adhesive after thermosetting can be measured in the following manner: (1) Prepare a plurality of sheets by forming the conductive adhesive into 5 cm squares. (2) Lay the plurality of sheets in such a way that the thickness reaches 300 μm to obtain a sheet laminate. (3) Press the sheet laminate at 70°C with 8 kN for 10 seconds. Then, heat-cure it at 200°C for 1 hour to obtain the test specimen for thermal conductivity measurement. (4) Blacken the test specimen for thermal conductivity measurement according to ASTM E1461. (5) Measure the thermal conductivity of the blackened test specimen for thermal conductivity measurement using a xenon lamp flash thermal conductivity analyzer (e.g., NETZSCH model "LFA-447"). The measurement conditions are set as follows: temperature 25°C, medium pulse width (approximately 0.2 ms), and charge level (flash intensity) 270 V.

[0045] [Conductive Sheet] The conductive sheet of this embodiment is formed from the conductive adhesive of this embodiment. More specifically, the conductive sheet of this embodiment is obtained by processing the conductive adhesive of this embodiment into a sheet shape. The conductive sheet of this embodiment can be obtained by coating a conductive adhesive composition obtained by suspending elastomer and metal particles in an organic solvent onto a substrate (e.g., a release film) into a sheet shape and then drying it.

[0046] The conductive sheet of this embodiment, like the conductive adhesive of this embodiment, contains an elastomer and metal particles, and the metal particles include copper particles. Furthermore, in the conductive sheet of this embodiment, similar to the conductive adhesive of this embodiment, the molar concentration of carboxyl groups is 2.0 μmol / g or less. Furthermore, the conductive sheet of this embodiment may form a metal coating layer composed of a metal other than copper covering at least a portion of the surface of the copper particles, or a treatment agent coating layer composed of a surface treatment agent covering the surface. Furthermore, the conductive sheet of this embodiment may also contain metal particles other than copper particles, preferably silver particles. Furthermore, a treatment agent coating layer composed of the surface treatment agent covering at least a portion of the surface of the silver particles may be formed.

[0047] In the conductive sheet of this embodiment, the acid value of the elastomer is preferably 1 mgKOH / g or less, and the acid value of the elastomer is most preferably 0 mgKOH / g.

[0048] Based on the total mass of the conductive sheet, the conductive sheet of this embodiment preferably contains 2% or more by mass, and more preferably 4% or more by mass of the aforementioned elastomer. Furthermore, based on the total mass of the conductive sheet, the conductive sheet of this embodiment preferably contains 20% or less by mass, and more preferably 10% or less by mass of the aforementioned elastomer.

[0049] Preferably, the conductive sheet in this embodiment further comprises a thermosetting resin, and the thermal conductivity of the conductive sheet after curing is 1 W / m·K or higher.

[0050] The thickness of the conductive sheet in this embodiment is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more. Furthermore, the thickness of the conductive sheet is preferably 150 μm or less, more preferably 100 μm or less, and even more preferably 80 μm or less. By making the thickness of the conductive sheet 150 μm or less, thermal conductivity can be further improved. The thickness of the conductive sheet can be obtained, for example, by measuring the thickness at any five randomly selected points using a graduated gauge (manufactured by PEACOCK, model R-205) and then arithmetically averaging these thicknesses.

[0051] [Cut-and-adhesive film] Next, the cut-and-adhesive film 20 will be described with reference to FIG1. ​​Furthermore, in the following description, the parts that overlap with the conductive adhesive and conductive sheet will not be repeated.

[0052] As shown in FIG. 1, the die-cutting and die-attachment film 20 of this embodiment includes a die-cutting strip 10 obtained by depositing an adhesive layer 2 on a substrate layer 1, and a conductive sheet 3 deposited on the adhesive layer 2 of the die-cutting strip 10. Semiconductor devices are attached to the conductive sheet 3 on the die-cutting and die-attachment film 20. The semiconductor devices may also be bare wafers. The bare wafers attached to the die-cutting and die-attachment film 20 of this embodiment are cut into a plurality of bare wafers by blade cutting, DBG (Dicing Before Grinding), or SDBG (Stealth Dicing Before Grinding). Then, during the cutting process described above, the conductive sheet 3 is also cut together with the bare wafers. The conductive sheet 3 is cut to a size comparable to the size of the plurality of monolithically formed bare wafers. In this way, a plurality of bare wafers with conductive sheets 3 can be obtained.

[0053] The conductive sheet 3 of the crystal-cutter bonding film 20 is constructed in the same manner as described above.

[0054] The substrate layer 1 supports the adhesive layer 2 and the conductive sheet 3 laminated on the adhesive layer 2. The substrate layer 1 contains resin. Examples of resins include: olefin resins such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer; copolymers with ethylene as a monomer component such as ethylene-vinyl acetate copolymer (EVA), ionomer resins, ethylene-(meth)acrylic acid copolymer, and ethylene-(meth)acrylic acid (random, alternating) copolymer; polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene terephthalate (PBT); acrylic resins; polyvinyl chloride (PVC); polyurethane; polycarbonate; polyphenylene sulfide (PPS); amide resins such as polyamide and fully aromatic polyamide (aramid); polyetheretherketone (PEEK); polyimide; polyetherimide; polyvinylidene chloride; ABS (acrylonitrile-butadiene-styrene copolymer); cellulose resins; polysiloxane resins; and fluoropolymers. From the viewpoint of improving elasticity, the substrate layer 1 is preferably composed of at least one resin selected from the group consisting of polypropylene (PP), polyvinyl chloride (PVC), and ethylene-vinyl acetate copolymer (EVA). Alternatively, the substrate layer 1 may be a laminate in which a first resin layer comprising ethylene-vinyl acetate copolymer (EVA) is used as the central layer, and a second resin layer comprising polypropylene (PP) and a third resin layer comprising polyvinyl chloride (PVC) are respectively laminated on both surfaces of the first resin layer.

[0055] The substrate layer 1 may contain one of the above-mentioned resins, or it may contain two or more of the above-mentioned resins.

[0056] Examples of materials for the substrate layer 1 include polymers such as crosslinked resins (e.g., plastic films). These plastic films can be used without stretching, or, as needed, can be those that have undergone uniaxial or biaxial stretching treatment. If the resin sheet is a heat-shrinkable material acquired through stretching or similar treatment, the adhesion area between the adhesive layer 2 and the conductive sheet 3 is reduced by heat-shrinking the substrate layer 1 after cutting, thus facilitating the recycling of semiconductor wafers (semiconductor devices).

[0057] The surface of the substrate layer 1 may also be subjected to general surface treatment to improve adhesion and retention with adjacent layers. Examples of such surface treatments include chemical or physical treatments such as chromic acid treatment, ozone exposure, flame exposure, high voltage electric shock exposure, and ionization radiation treatment, as well as coating treatment based on a primer.

[0058] The thickness of the substrate layer 1 is preferably 1 μm or more and 1000 μm or less, more preferably 10 μm or more and 500 μm or less, further preferably 20 μm or more and 300 μm or less, and even more preferably 30 μm or more and 200 μm or less. The thickness of the substrate layer 1 can be determined using a graduated gauge (manufactured by PEACOCK, model R-205) in the same manner as the thickness of the conductive sheet 3 described above.

[0059] The substrate layer 1 may also contain various additives. Examples of such additives include: colorants, fillers, plasticizers, anti-aging agents, antioxidants, surfactants, flame retardants, etc.

[0060] The adhesive used to form the adhesive layer 2 is not particularly limited, and general pressure-sensitive adhesives such as acrylic adhesives and rubber adhesives can be used. As the aforementioned pressure-sensitive adhesive, in terms of the cleanability of electronic components such as semiconductor wafers and glass that are susceptible to contamination based on organic solvents such as ultrapure water and alcohols, an acrylic adhesive with an acrylic polymer as the base polymer is preferred.

[0061] Examples of the aforementioned acrylic polymers include acrylic polymers that use one or more of alkyl (meth)acrylates and cycloalkyl (meth)acrylates as monomer components. Examples of alkyl (meth)acrylates include methyl esters, ethyl esters, propyl esters, isopropyl esters, butyl esters, isobutyl esters, dibutyl esters, tributyl esters, pentyl esters, isopentyl esters, hexyl esters, heptyl esters, octyl esters, 2-ethylhexyl esters, isooctyl esters, nonyl esters, decyl esters, isodecanyl esters, undecyl esters, dodecyl esters, tridecyl esters, tetradecyl esters, hexadecyl esters, octadecyl esters, eicosyl esters, and other linear or branched alkyl esters with 1 to 30 carbon atoms, particularly 4 to 18 carbon atoms. Examples of cycloalkyl (meth)acrylates include cyclopentyl esters and cyclohexyl esters. Furthermore, "(meth)acrylate" refers to at least one of acrylates and methacrylates, and the "(methyl)" in this invention represents the same content as described above.

[0062] The above-mentioned acrylic polymers, for the purpose of modifying cohesiveness, heat resistance, etc., may also include, as needed, units corresponding to other monomer components that can copolymerize with the above-mentioned alkyl or cycloalkyl methacrylates. Examples of such monomer components include: acrylic acid, methacrylic acid, carboxyethyl methacrylate, carboxypentyl methacrylate, itconic acid, maleic acid, fumaric acid, crotonic acid, and other carboxyl-containing monomers; maleic anhydride, itconic anhydride, and other anhydride monomers; 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl methacrylate, 8-hydroxyoctyl methacrylate, and other monomers containing carboxyl groups. The copolymerizable monomers include hydroxyl-containing monomers such as 10-hydroxydecyl acrylate, 12-hydroxylaurate (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl methacrylate; sulfonic acid-containing monomers such as styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acryloxynaphthalene sulfonic acid, (meth)acrylamide sulfonylpropyl acrylate, and (meth)acryloxynaphthalene sulfonic acid; phosphate-containing monomers such as 2-hydroxyethylacrylamide phosphate; acrylamide, acrylonitrile, etc. One or more of these copolymerizable monomers may be used. Preferably, the amount of these copolymerizable monomers used is less than 40% by mass of the total monomer composition.

[0063] Furthermore, in order to crosslink, the aforementioned acrylic polymer may also include polyfunctional monomers as copolymerizing monomer components as needed. Examples of such polyfunctional monomers include: hexanediol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, neopentyl glycol dimethacrylate, pentaerythritol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate, dipentaerythritol hexamethacrylate, epoxy methacrylate, polyester methacrylate, and urethane methacrylate. One or more of these polyfunctional monomers may be used. In terms of adhesive properties, the amount of polyfunctional monomer used is preferably 30% by mass or less of the total monomer components.

[0064] The above-mentioned acrylic polymer can be obtained by polymerizing a single monomer or a mixture of two or more monomers. Polymerization can be carried out by any of the following methods: solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, etc. For the purpose of preventing contamination of the clean adhesive, it is preferable to have a lower content of low molecular weight substances. In this regard, the number average molecular weight of the acrylic polymer is preferably 300,000 or more, and more preferably around 400,000 to 3,000,000.

[0065] Furthermore, in the above-mentioned adhesive, in order to increase the number average molecular weight of the acrylic polymer, etc., which serves as the base polymer, an external crosslinking agent may be appropriately added. Specific methods for external crosslinking include adding crosslinking agents such as polyisocyanate compounds, epoxy compounds, aziridine compounds, and melamine-based crosslinking agents to carry out the reaction. When using an external crosslinking agent, its amount is appropriately determined considering the balance with the base polymer to be crosslinked and its intended use as an adhesive. Generally, regarding the external crosslinking agent, it is preferable to prepare about 5 parts by mass or less relative to 100 parts by mass of the base polymer, and more preferably 0.1 to 5 parts by mass.

[0066] In addition to the above-mentioned components, the adhesive may also contain various known adhesive agents, anti-aging agents and other additives as needed.

[0067] The adhesive layer 2 can be formed by a radiation-curing adhesive. The radiation-curing adhesive can increase the degree of cross-linking by irradiation with ultraviolet rays, thereby easily reducing the adhesion. That is, by forming the adhesive layer 2 with a radiation-curing adhesive, before cutting, the conductive sheet 3 is pre-adheded to the adhesive layer 2 without irradiating the adhesive layer 2 with radiation. After cutting, the adhesive layer 2 is irradiated with radiation to reduce the adhesion of the adhesive layer 2, thereby making it easy to pick up (recycle) the semiconductor wafer (semiconductor device).

[0068] Radiation-curing adhesives that have radiation-curing functional groups such as carbon-carbon double bonds and exhibit adhesive properties can be used without particular restrictions. Examples of radiation-curing adhesives include additive-type radiation-curing adhesives obtained by blending radiation-curing monomeric components and oligomer components into general pressure-sensitive adhesives such as acrylic adhesives and rubber adhesives.

[0069] Examples of the aforementioned radiocurable monomer components include: urethane (meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and 1,4-butanediol di(meth)acrylate. Furthermore, examples of the aforementioned radiocurable oligomer components include: various oligomers such as urethane-based, polyether-based, polyester-based, polycarbonate-based, and polybutadiene-based oligomers, with a suitable molecular weight range of approximately 100 to 30,000. The amount of the aforementioned radiocurable monomer component or the aforementioned radiocurable oligomer component is preferably such that it can appropriately reduce the adhesive force of the adhesive layer 2 after radiation irradiation. Typically, the amount of the aforementioned radiocurable monomeric component or the aforementioned radiocurable oligomer component is 5 to 500 parts by mass relative to 100 parts by mass of the basic polymer such as the acrylic polymer constituting the adhesive, and more preferably 40 to 150 parts by mass.

[0070] Furthermore, in addition to the aforementioned additive-type radiation-curing adhesives, intrinsic-type radiation-curing adhesives can also be used as examples, employing a base polymer having carbon-carbon double bonds in the side chain or main chain, or at the end of the main chain. These intrinsic-type radiation-curing adhesives do not need to contain oligomer components that are low molecular weight components, or the content of such oligomer components is relatively small. Therefore, when using the aforementioned intrinsic-type radiation-curing adhesive, the long-term migration of the oligomer components within the adhesive layer 2 can be suppressed. As a result, the adhesive layer 2 can have a more stable layer structure.

[0071] If the aforementioned basic polymer having carbon-carbon double bonds has carbon-carbon double bonds and adhesive properties, it can be used without particular restrictions. Preferably, an acrylic polymer is used as the basic backbone. Examples of acrylic polymers as the basic backbone include the aforementioned acrylic polymers.

[0072] There are no particular limitations on the method of introducing carbon-carbon double bonds into the above-mentioned acrylic polymers, and various methods can be used. However, if the method of introducing carbon-carbon double bonds into the side chains of the polymer is adopted, molecular design will become easier. For example, the following method can be used: after copolymerizing the acrylic polymer with a monomer having a functional group, a compound having a functional group capable of reacting with the functional group and a carbon-carbon double bond is subjected to a condensation reaction or an addition reaction in a state that maintains the radiocurability of the carbon-carbon double bond.

[0073] Examples of combinations of these functional groups include: carboxylic acid group and epoxy group, carboxylic acid group and aziridinyl group, hydroxyl group and isocyanate group, etc. Among these combinations of functional groups, the combination of hydroxyl group and isocyanate group is suitable in terms of the ease of tracking the reaction. Furthermore, if the combination of these functional groups is a combination that will generate the above-mentioned acrylic polymer having carbon-carbon double bonds, then any functional group can be located on the acrylic polymer side or the compound having carbon-carbon double bonds side. In the case of the above-mentioned preferred combination, it is preferable that the acrylic polymer has a hydroxyl group and the compound having carbon-carbon double bonds has an isocyanate group. In this case, examples of isocyanate compounds having carbon-carbon double bonds include: methacrylic acid isocyanate, 2-methacrylic acid oxyethyl isocyanate, m-isopropenyl-α,α-dimethylbenzyl isocyanate, etc. Furthermore, as an acrylic polymer, it can be obtained by copolymerizing the above-mentioned ether compounds containing hydroxyl monomers, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether.

[0074] The aforementioned intrinsically type radiation-curable adhesive can be made using the aforementioned base polymer (especially acrylic polymer) having carbon-carbon double bonds alone, or the aforementioned radiation-curable monomer component or the aforementioned radiation-curable oligomer component can be formulated without degrading the properties. Regarding the aforementioned radiation-curable oligomer component, it is generally included in the range of 30 parts by mass or less relative to 100 parts by mass of the base polymer, preferably in the range of 1 to 10 parts by mass.

[0075] The above-mentioned radiation-curing adhesive contains a photopolymerization initiator when it is cured using ultraviolet light or the like. Examples of photopolymerization initiators include: α-keto alcohol compounds such as 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl) ketone, α-hydroxy-α,α'-dimethylacetophenone, 2-methyl-hydroxyacetophenone, and 1-hydroxycyclohexylphenyl ketone; acetophenone compounds such as methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, and 2-methyl-1-[4-(methylthio)-phenyl]-2-morpholinylpropane-1; acetophenone ether compounds such as benzoin ethyl ether, benzoin isopropyl ether, and anisole methyl ether; and benzyl dimethyl ketal. Ketal compounds; aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride; photoactive oxime compounds such as 1-benzophenone-1,1-propanedione-2-(O-ethoxycarbonyl)oxime; benzophenone compounds such as benzoylbenzoic acid and 3,3'-dimethyl-4-methoxybenzophenone; thioxanthone compounds such as 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, and 2,4-diisopropylthioxanthone; camphorquinone; halogenated ketones; acetylsphosphonates; acetylsphosphonates, etc. The amount of photopolymerization initiator is, for example, 0.05 to 20 parts by mass relative to 100 parts by mass of the base polymer such as the acrylic polymer constituting the adhesive.

[0076] Furthermore, examples of radiation-curing adhesives include rubber-based adhesives and acrylic adhesives disclosed in Japanese Patent Application Publication No. 60-196956, which contain: addition polymerizable compounds having two or more unsaturated bonds, photopolymerizable compounds such as alkoxysilanes having epoxy groups; and photopolymerization initiators such as carbonyl compounds, organosulfur compounds, peroxides, amines, and onium salt compounds.

[0077] When curing inhibition occurs due to oxygen during radiation irradiation, it is ideal to shield the surface of the radiation-curable adhesive layer 2 from oxygen (air) using some method. Examples include: covering the surface of the adhesive layer 2 with an isolation film, or irradiating it with ultraviolet or other radiation in a nitrogen atmosphere.

[0078] There is no particular limitation on the thickness of the adhesive layer 2, but in terms of both preventing defects on the wafer cutting surface and maintaining the conductive sheet 3, it is preferably 1 to 50 μm, and more preferably 2 to 30 μm.

[0079] The matters disclosed in this specification include the following.

[0080] (1) A conductive adhesive comprising an elastomer and metal particles, wherein the metal particles comprise copper particles, and wherein the molar concentration of the carboxyl group in the conductive adhesive is 2.0 μmol / g or less.

[0081] According to the above configuration, in the conductive adhesive composition used to obtain the above conductive adhesive, the time-dependent increase in viscosity can be suppressed.

[0082] (2) The conductive adhesive as described in (1) above, wherein a coating layer covering the surface is formed on at least a portion of the surface of the copper particles.

[0083] According to the above configuration, in the conductive composition used to obtain the above-mentioned conductive adhesive, the time-dependent increase in viscosity can be further suppressed.

[0084] (3) The conductive adhesive as described in (1) or (2) above, wherein the acid value of the elastomer is less than 1 mgKOH / g.

[0085] According to the above configuration, in the conductive composition used to obtain the above-mentioned conductive adhesive, the time-dependent increase in viscosity can be further suppressed.

[0086] (4) The conductive adhesive as described in (2) or (3) above, wherein the coating layer is made of metal.

[0087] According to the above configuration, in the conductive composition used to obtain the above-mentioned conductive adhesive, the increase in viscosity over time can be further suppressed. Furthermore, the conductivity of the above-mentioned conductive adhesive can be improved.

[0088] (5) The conductive adhesive described in any one of (1) to (4) above contains 2% or more and 20% or less of the above-mentioned elastomer and contains 70% or more and 95% or less of the above-mentioned metal particles.

[0089] According to the above configuration, in the conductive composition used to obtain the above-mentioned conductive adhesive, the time-dependent increase in viscosity can be further suppressed.

[0090] (6) The conductive adhesive described in any one of (1) to (5) above further includes a thermosetting resin, wherein the thermal conductivity of the conductive adhesive after curing is 1 W / m·K or more.

[0091] According to the above configuration, in the conductive composition used to obtain the above-mentioned conductive adhesive, the increase in viscosity over time can be further suppressed. In addition, the above-mentioned conductive adhesive also has sufficient thermal conductivity.

[0092] (7) A conductive sheet formed from any one of the conductive adhesives described in (1) to (6) above.

[0093] According to the above configuration, the conductive sheet is formed by a conductive adhesive whose viscosity increases over time, thus having a more uniform thickness.

[0094] (8) A diced adhesive film comprising: a diced strip obtained by depositing an adhesive layer on a substrate layer, and a conductive sheet deposited on the adhesive layer of the diced strip, wherein the conductive sheet is the conductive sheet described in (7) above.

[0095] According to the above configuration, the above-mentioned crystal-cutter bonding film has a conductive sheet with a relatively uniform thickness.

[0096] Furthermore, the conductive adhesive, conductive sheet, and diced crystal bonding film of the present invention are not limited to the above-described embodiments. Also, the conductive adhesive, conductive sheet, and diced crystal bonding film of the present invention are not limited to the effects described above. Various modifications can be made to the conductive adhesive, conductive sheet, and diced crystal bonding film of the present invention without departing from the spirit of the present invention. Examples

[0097] Next, the present invention will be described in more detail by way of examples. The following examples are for the purpose of describing the present invention in more detail and do not limit the scope of the present invention.

[0098] [Example 1] A varnish (conductive adhesive composition) was prepared by mixing a mixture containing the materials in the mass ratio shown in one of the items in Example 1 of Table 1 below for 3 minutes using a mixer (manufactured by Keyence Corporation, trade name: HM-500). Furthermore, the mixing was performed by adding the materials listed in the "First Mixing" column of Tables 1A and 1B below to obtain a first mixture (first mixing), and then further mixing (second mixing) with the materials listed in the "Second Mixing" column. The first mixing was performed for 1 minute, and the second mixing was performed for 2 minutes. After applying the varnish to one side of a release film (manufactured by Mitsubishi Chemical Corporation, trade name: MRA38, thickness 38 μm), it was dried at 100°C for 2 minutes to obtain a conductive sheet with a thickness of 30 μm. Furthermore, the following materials were used as listed in Table 1 below. • Phenolic resin MEHC-7851S (biphenyl type phenolic resin, phenol equivalent 209 g / eq) manufactured by Meiwa Chemical Co., Ltd. • Solid epoxy resin EPICLON N-665-EXP-S (cresol phenolic varnish type multifunctional epoxy resin, epoxy equivalent 200 g / eq) manufactured by Nippon Steel & Sumitomo Chemical Co., Ltd. • Liquid epoxy resin HP-A-4860 (aliphatic modified bisphenol A type epoxy resin (difunctional), epoxy equivalent 403 g / eq) manufactured by DIC Co., Ltd. • Silver-coated copper (Cu) particles: Particles obtained by coating flat copper particles with a 10% by mass silver layer (average particle size 3.5 μm, amorphous. hereinafter referred to as silver-coated copper particles). • Silver (Ag) particle agglomerated nanoparticles (amorphous, average particle size of the agglomerates 1.8 μm. hereinafter referred to as agglomerated silver particles). • Acrylic resin solution PARACRPN manufactured by Nekami Kogyo Co., Ltd. AC-019 (containing MEK and toluene as solvents, solid content 20.1%, acid value zero, mass average molecular weight 1.1 million, glass transfer temperature -15°C, acrylate compound) · Coupling agent OFS-6920 (bis(triethoxysilylpropyl)tetrasulfide) manufactured by Toray Dow Corning Co., Ltd. · Catalyst TPP-MK (tetraphenylphosphonium tetra(4-methylphenyl)borate) manufactured by Beixing Chemical Industry Co., Ltd. · Solvents: Primary blending: methyl isobutyl ketone (MIBK); Secondary blending: methyl ethyl ketone (MEK) Furthermore, the solid content concentration (acrylic resin concentration) in the acrylic resin solution, the mass of the conductive sheet, the acrylic resin ratio in the conductive sheet, the metal particle ratio in the conductive sheet, and the silver-coated copper particle ratio in the conductive sheet are shown in Table 2 below. Moreover, the mass of the conductive sheet was measured after peeling off the release film described above.

[0099] [Example 2] The mixing ratios of each material were changed as shown in Tables 1A and 1B below. Otherwise, the process was the same as in Example 1 to obtain the conductive sheet of Example 2. Furthermore, regarding Example 2, the concentration of solids in the acrylic resin solution (acrylic resin concentration), the mass of the conductive sheet, the acrylic resin ratio in the conductive sheet, the metal particle ratio in the conductive sheet, and the silver-coated copper particle ratio in the conductive sheet are also shown in Table 2 below.

[0100] [Comparative Example 1] As the acrylic resin solution, Teisan Resin SG-70L (containing MEK and toluene as solvents, solid content 12.5%, glass transition temperature -13°C, mass average molecular weight 900,000, acid value 5 mg / KOH, carboxyl-containing acrylic copolymer) manufactured by Nagase ChemteX Corporation was used. The mixing ratio of each material was changed as shown in Tables 1A and 1B below. Otherwise, the process was carried out in the same manner as in Example 1, and the conductive sheet of Comparative Example 1 was obtained. Furthermore, regarding Comparative Example 1, the solid content concentration (acrylic resin concentration) in the acrylic resin solution, the mass of the conductive sheet, the acrylic resin ratio in the conductive sheet, the metal particle ratio in the conductive sheet, and the silver-coated copper particle ratio in the conductive sheet are also shown in Table 2 below.

[0101] [Comparative Example 2] The mixing ratio of each material was changed as shown in Tables 1A and 1B below. Otherwise, the same procedure was performed as in Comparative Example 1 to obtain the conductive sheet of Comparative Example 2.

[0102] Furthermore, regarding Comparative Example 2, the concentration of solids in the acrylic resin solution (acrylic resin concentration), the mass of the conductive sheet, the acrylic resin ratio in the conductive sheet, the metal particle ratio in the conductive sheet, and the silver-coated copper particle ratio in the conductive sheet are also shown in Table 2 below. [Table 1A] unit Example 1 Example 2 Comparative Example 1 Comparative Example 2 One allocation Phenolic resin g 2.04 0.93 2.04 1.05 solid epoxy resin g 1.64 0.61 1.64 0.68 liquid epoxy resin g 0.70 0.26 0.70 0.29 Silver-copper particles g 20.01 11.56 20.01 12.88 Silver particles g 6.32 26.97 6.32 30.06 Methyl isobutyl ketone (MIBK, solvent) g 5.62 7.20 4.97 5.00 Secondary adjustment acrylic resin solution g 9.38 9.00 15.00 16.17 Coupling agent g 0.16 0.20 0.16 0.20 catalyst g 0.02 0.01 0.02 0.01 Methyl ethyl ketone (MEK, solvent) g 1.00 1.00 3.70 3.00 Total g 46.89 57.74 54.56 69.34

[0103] [Table 1B] unit Example 1 Example 2 Comparative Example 1 Comparative Example 2 One allocation Phenolic resin Quality 4.35 1.61 3.74 1.51 solid epoxy resin Quality 3.50 1.06 3.01 0.98 liquid epoxy resin Quality 1.49 0.45 1.28 0.42 Silver-copper particles Quality 42.67 20.02 36.67 18.57 Silver particles Quality 13.48 46.71 11.58 43.35 Methyl isobutyl ketone (MIBK, solvent) Quality 11.98 12.47 9.11 7.21 Secondary adjustment acrylic resin solution Quality 20.00 15.59 27.49 23.32 Coupling agent Quality 0.35 0.35 0.30 0.29 catalyst Quality 0.04 0.02 0.03 0.02 Methyl ethyl ketone (MEK, solvent) Quality 2.13 1.73 6.78 4.33 Total Quality 100.00 100.00 100.00 100.00

[0104] [Table 2] unit Example 1 Example 2 Comparative Example 1 Comparative Example 2 Concentration of solids in acrylic resin solution quality% 20.10 20.10 12.50 12.50 Quality of conductive sheets g 32.78 42.35 32.77 47.19 Acrylic resin ratio in conductive sheets quality% 5.75 4.27 5.72 4.28 The ratio of metal particles in conductive sheets quality% 80.36 90.98 80.36 90.99 The ratio of silver-copper particles in conductive sheets quality% 61.05 27.30 61.07 27.29

[0105] <Evaluation of Gelation Inhibition> Gelation inhibition was evaluated for each example of the varnish (conductive adhesive composition). The evaluation was conducted by visually observing the varnish film obtained after coating. Specifically, the evaluation was judged according to the following criteria: Excellent: No pinholes are visible under visual inspection. Undesirable: Only one pinhole is visible under visual inspection. The results are shown in Table 3 below. Furthermore, the filling rate of metal particles in the conductive sheet shown in Table 3 below was obtained by dividing the mass of the metal particles (silver-copper coated particles and silver particles) by the mass of the conductive sheet and then multiplying by 100. Also, the mass ratio of silver-copper coated particles in the metal particles shown in Table 3 below was obtained by dividing the mass of the silver-copper coated particles by the mass of the metal particles and then multiplying by 100. Furthermore, the mass ratio of acrylic resin in the organic components is obtained by dividing the mass of acrylic resin (the solid component in the acrylic resin solution) by the mass of the organic components (phenolic resin, solid epoxy resin, liquid epoxy resin, and acrylic resin) and then multiplying by 100. Similarly, the mass ratio of acrylic resin in the conductive sheet is obtained by dividing the mass of acrylic resin by the mass of the conductive sheet and then multiplying by 100. The molar concentration of carboxyl groups in the conductive sheet is a value measured according to the method described in the conductive adhesive section of the above embodiments. Moreover, the conductive sheets of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 all contain phenolic resin; therefore, the molar concentration of carboxyl groups in these conductive sheets is a value measured according to evaluation method 2 in the method described in the conductive adhesive section of the above embodiments.

[0106] <Viscosity Evaluation> The viscosity of each example varnish (conductive adhesive composition) was evaluated. The viscosity evaluation was performed by measuring the change in viscosity over time using an E-type viscometer. The measurement of the change in viscosity over time using the E-type viscometer was performed at a test temperature of 25°C and a rotation speed of 10 rpm. Furthermore, the viscosity evaluation was judged according to the following criteria: Excellent: The viscosity change is less than 5% after 12 hours. Acceptable: The viscosity change confirmed after 12 hours is 5% or more but less than 50%. Unacceptable: The viscosity change confirmed after 12 hours is 50% or more. The results are shown in Table 3 below.

[0107] <Thermal Conductivity of Conductive Sheets> The thermal conductivity of each conductive sheet after thermosetting was measured. The thermal conductivity of the conductive sheet after thermosetting was measured as follows: (1) A plurality of sheets were prepared by forming a conductive adhesive into 5 cm squares. (2) The plurality of sheets were laminated to a thickness of 300 μm to obtain a laminated sheet. (3) The laminated sheet was pressed at 70°C with 8 kN for 10 seconds. Then, it was thermoset at 200°C for 1 hour to obtain a test specimen for thermal conductivity measurement. (4) The test specimen for thermal conductivity measurement was blackened according to ASTM E1461. (5) The thermal conductivity of the blackened test specimen for thermal conductivity measurement was measured using a xenon flash thermal conductivity analyzer (e.g., NETZSCH model "LFA-447"). The measurement conditions were 25℃, medium pulse width (approximately 0.2ms), and a charging level (flash intensity) of 270V. The measurement results are shown in Table 3 below.

[0108] [Table 3] unit Example 1 Example 2 Comparative Example 1 Comparative Example 2 Metal particles Filling rate of metal particles in conductive sheets quality% 80.36 91.00 80.36 91.00 Mass ratio of silver-copper particles in metal particles quality% 76.00 30.00 76.00 30.00 Mass ratio of silver-coated copper particles in conductive sheets quality% 61.07 27.30 61.07 27.30 The mass ratio of acrylic resin in the organic components quality% 30.00 50.00 30.00 50.00 Mass ratio of acrylic resin in conductive sheets quality% 5.89 4.50 5.89 4.50 molar concentration of carboxyl groups in conductive sheets μmol / g 0.00 0.00 5.26 4.01 Evaluation of gelation inhibition - excellent excellent No excellent Viscosity evaluation - excellent excellent No Can thermal conductivity W / m•K 1.70 10.00 1.30 5.00

[0109] According to Table 3, in the conductive sheets of Examples 1 and 2, the results of the gelation inhibition evaluation and the viscosity evaluation of the varnish (conductive adhesive composition) used to obtain the conductive sheets were both "Excellent," indicating extremely good performance. In contrast, in the conductive sheet of Comparative Example 1, the result of the gelation inhibition evaluation of the varnish (conductive adhesive composition) used to obtain the conductive sheet was "Acceptable," which is a worse result than the examples. Furthermore, in the conductive sheet of Comparative Example 1, the result of the viscosity evaluation of the varnish (conductive adhesive composition) used to obtain the conductive sheet was "Unacceptable." Moreover, in the conductive sheet of Comparative Example 2, the result of the gelation inhibition evaluation of the varnish (conductive adhesive composition) used to obtain the conductive sheet was "Excellent," but the viscosity evaluation result was "Acceptable," which is worse than the examples. Among them, the result of the conductive sheet of Comparative Example 1, which corresponds to the conductive sheet of Example 1, is that the thermal conductivity value is lower than that of the conductive sheet of Example 1. The result of the conductive sheet of Comparative Example 2, which corresponds to the conductive sheet of Example 2, is that the thermal conductivity value is lower than that of the conductive sheet of Example 2. [Simplified Explanation of the Diagram]

[0013] Figure 1 is a cross-sectional view showing the structure of a crystal-cutter bonding film according to one embodiment of the present invention.

Claims

1. A conductive adhesive comprising an elastomer and metal particles, wherein the acid value of the elastomer is less than 1 mgKOH / g, the metal particles comprise copper particles, and the molar concentration of carboxyl groups in the conductive adhesive is less than 2.0 μmol / g.

2. The conductive adhesive of claim 1, wherein a coating layer covering at least a portion of the surface of the copper particles is formed.

3. The conductive adhesive of claim 2, wherein the coating layer is made of metal.

4. The conductive adhesive of claim 1 or 2, comprising 2% by mass and less than 20% by mass of the aforementioned elastomer, and comprising 70% by mass and less than 95% by mass of the aforementioned metal particles.

5. The conductive adhesive of claim 1 or 2, further comprising a thermosetting resin, wherein the thermal conductivity of the conductive adhesive after curing is 1 W / m·K or higher.

6. A conductive sheet formed from a conductive adhesive as claimed in any one of claims 1 to 5.

7. A diced adhesive film comprising: a diced strip obtained by depositing an adhesive layer on a substrate layer, and a conductive sheet deposited on the adhesive layer of the diced strip, wherein the conductive sheet is the conductive sheet as claimed in claim 6.

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