JP7139590B2 - COMPOSITION FOR CONDUCTOR-FORMING, JOINT AND METHOD FOR MANUFACTURING THE SAME - Google Patents

Description

TECHNICAL FIELD The present invention relates to a conductor-forming composition, a joined body, and a method for producing the same.

Copper has high electrical and thermal conductivity, so it is widely used as a conductor wiring material, a heat transfer material, a heat exchange material, a heat dissipation material, and the like.

In recent years, as a method of forming a copper pattern as an alternative to photolithography, a process of forming a layer containing a metal on a substrate by ink, paste, etc. containing a metal by inkjet printing, screen printing, etc., and heating to express conductivity So-called printed electronics are known, including a conductive process.

As printing inks or printing pastes for forming copper patterns by printing, dispersions of copper nanoparticles, solutions or dispersions of metal complexes, and the like have been investigated. However, since copper is stable in its oxidation state at room temperature, it always contains copper in its oxidation state. Therefore, in order for copper to exhibit electrical conductivity and thermal conductivity, it is necessary to reduce copper in an oxidized state and further convert it into a copper continuum.

As a method for solving this problem, Patent Document 1 describes a coated copper particle that can be sintered at a low temperature and exhibits good electrical conductivity, and a method for producing the same. The copper particles described in Patent Document 1 are obtained by mixing a copper precursor such as copper oxalate and a reducing compound such as hydrazine to obtain a composite compound, and a step of heating the composite compound in the presence of an alkylamine. It is manufactured by a method having In the example of Patent Document 1, the ink containing the produced copper particles is heated to 300° C. at 60° C./min in an argon atmosphere and held for 30 minutes to achieve conductivity. Moreover, Patent Document 2 describes a conductive paste composition containing a conductive metal powder, an organic vehicle, and the like. For the purpose of removing the organic binder, heat treatment is usually performed at 250°C to 330°C in an air atmosphere, a nitrogen atmosphere, or the like to burn the organic vehicle, and then the metal powder is heated at 850°C to 850°C in a neutral or reducing atmosphere so that the metal powder is not oxidized. Sintering at 1300° C. is described.

JP 2012-072418 A JP 2012-226865 A

By the way, in the process of forming a copper pattern used as a bonding material for terminals of electronic parts, it is desired that the copper pattern can be made conductive at a lower temperature. For example, in the examples of Patent Document 1, the conductive property is exhibited by heating up to 300° C., and there is a demand for a conductor-forming composition that can be made conductive at a temperature lower than this.

The present invention has been made in view of such circumstances, and provides a conductor-forming composition that can be formed into a conductor at a low temperature (e.g., 250° C. or lower) and that can be used as a metal bonding material. is the main purpose.

The present invention provides a conductor-forming composition shown in (1) to (3) below, a method for producing a joined body shown in (4) and (5) below, and a joined body shown in (6) below.

(1) A conductor containing first particles having a core particle containing metallic copper and an organic substance covering at least a part of the surface of the core particle, second particles containing copper oxide, and a dispersion medium Forming composition.
(2) The conductor-forming composition according to (1), wherein the content of the second particles is 0.5 parts by mass to 12 parts by mass with respect to 100 parts by mass of the first particles.
(3) The conductor-forming composition according to (1) or (2), further containing a reducing agent.
(4) a first base material, a composition layer made of the conductor-forming composition according to any one of (1) to (3), and a second base material, which are laminated in this order. A method of manufacturing a bonded body, comprising the steps of: preparing; and heating a bonding precursor at 120° C. to 250° C. in an atmosphere of an inert gas, a reducing gas, or a mixed gas thereof.
(5) The method for producing a joined body according to (4), wherein the gas atmosphere is an atmosphere containing hydrogen gas or formic acid gas.
(6) A first base material, a second base material, and a conductor layer that joins the first base material and the second base material, wherein the conductor layer comprises (1) to (3) A joined body, comprising a sintered body obtained by sintering the first particles and the second particles contained in the conductor-forming composition according to any one of the above.

According to the present invention, a conductor-forming composition that can be formed into a conductor at a low temperature (e.g., 250° C. or lower) and can be used as a metal bonding material, a bonded body using the same, and a method for producing the same are provided. be done.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic cross section for demonstrating one Embodiment of the manufacturing method of the joined body using the composition for conductor formation. 4 is an X-ray diffraction (XRD) spectrum in the diffraction angle range of 30 to 80° of the first particles synthesized in Production Example 2. FIG.

DETAILED DESCRIPTION OF THE INVENTION Embodiments for carrying out the present invention will be described in detail below. However, the present invention is not limited to the following embodiments.

In this specification, the numerical range indicated using "to" indicates the range including the numerical values before and after "to" as the minimum and maximum values, respectively. Furthermore, in the present specification, the content of each component in the composition refers to the total amount of the multiple substances present in the composition when there are multiple substances corresponding to each component in the composition, unless otherwise specified. means

As used herein, the term "conductor-forming composition" refers to a composition that can be sintered to form a conductive object, that is, a "conductor". “Conductivity” refers to sintering metal-containing particles to transform them into a conductive object. "Conductor" refers to an object having electrical conductivity.

As used herein, the term "substrate" refers to an object having a surface on which a composition layer made of a conductor-forming composition can be formed.

As used herein, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved.

In the present specification, the term "layer" includes not only the configuration of shapes formed over the entire surface but also the configuration of shapes formed partially when observed as a plan view.

In the present specification, the state in which the first particles and the second particles are "sintered" means that the first particles and the second particles are completely or partially fused and integrated (fused). It includes both a state in which the first particle and the second particle are in contact without being fused together.

<Conductor-forming composition>
The conductor-forming composition of the present embodiment comprises first particles having core particles containing metallic copper and an organic material covering at least a part of the surfaces of the core particles, second particles containing copper oxide, and dispersed and a medium. By using such a conductor-forming composition, it may become possible to form a conductor at a low temperature (for example, 250° C. or lower).

(first particle)
The first particle has a core particle containing metallic copper and an organic substance covering at least part of the surface of the core particle. As the first particles, for example, copper-containing particles disclosed in JP-A-2016-037627 can be suitably used.

The copper-containing particles of JP-A-2016-037627 have a core particle containing copper and an organic substance containing an alkylamine-derived substance present on at least a part of the surface of the core particle, and the alkylamine is a hydrocarbon group. contains alkylamines having 7 or less carbon atoms. Since the chain length of the hydrocarbon group of the alkylamine constituting the organic substance is relatively short, thermal decomposition occurs even at a relatively low temperature (for example, 150° C. or less), and the core particles are easily fused together.

The organic substance may contain an alkylamine having a hydrocarbon group with 7 or less carbon atoms. The alkylamine having a hydrocarbon group with 7 or less carbon atoms may be, for example, a primary amine, a secondary amine, an alkylenediamine, or the like. Examples of primary amines include ethylamine, 2-ethoxyethylamine, propylamine, 3-ethoxypropylamine, butylamine, 4-methoxybutylamine, isobutylamine, pentylamine, isopentylamine, hexylamine, cyclohexylamine and heptylamine. be able to. Examples of secondary amines include diethylamine, dipropylamine, dibutylamine, ethylpropylamine, ethylpentylamine and the like. Examples of alkylenediamines include ethylenediamine, N,N-dimethylethylenediamine, N,N'-dimethylethylenediamine, N,N-diethylethylenediamine, N,N'-diethylethylenediamine, 1,3-propanediamine, 2,2-dimethyl- 1,3-propanediamine, N,N-dimethyl-1,3-diaminopropane, N,N'-dimethyl-1,3-diaminopropane, N,N-diethyl-1,3-diaminopropane, 1,4 -diaminobutane, 1,5-diamino-2-methylpentane, 1,6-diaminohexane, N,N'-dimethyl-1,6-diaminohexane, 1,7-diaminoheptane and the like. .

The organic matter covering at least part of the surface of the core particles may contain an organic matter other than the alkylamine having a hydrocarbon group with 7 or less carbon atoms. The proportion of alkylamines having a hydrocarbon group with 7 or less carbon atoms in the total organic substance is preferably 50% by mass or more, more preferably 60% by mass or more, and further preferably 70% by mass or more. preferable.

The ratio of the organic matter covering at least part of the surface of the core particles is preferably 0.1% by mass to 20% by mass with respect to the total of the core particles and the organic matter. When the proportion of organic matter is 0.1% by mass or more, sufficient oxidation resistance tends to be obtained. When the proportion of the organic matter is 20% by mass or less, it tends to be easier to achieve conductivity at low temperatures. The ratio of the organic matter to the total of the core particles and the organic matter is more preferably 0.3% by mass to 10% by mass, more preferably 0.5% by mass to 5% by mass.

As for the size of the first particles, the average length of the long axis is preferably in the range of 10 nm to 500 nm. From the viewpoint of lowering the conductive temperature, the average length of the major axis is more preferably 20 nm to 500 nm, and even more preferably 30 nm to 500 nm. The major axis of the first grain means the distance between two planes which are circumscribed to the first grain and are chosen such that the distance between the two planes which are parallel to each other is maximized. The long axis of the first particles can be measured by a known method such as observation with an electron microscope. The average major axis length means the arithmetic average of the major axis lengths measured for 200 randomly selected first particles. When the first particles are randomly selected from the electron microscope image, the first particles having a particle diameter of less than 3 nm are excluded from the measurement targets.

The shape of the first particles is not particularly limited. For example, it may be spherical, long-grained, flattened, or fibrous, and can be selected according to the application of the first particles. From the viewpoint of use as a printing paste, it is preferably spherical or long-grained.

The first particles contain at least metallic copper and may contain other substances as needed. Substances other than metallic copper include metals such as gold, silver, platinum, tin and nickel, compounds containing these metal elements, reducing compounds, organic substances, and the like. From the viewpoint of forming a conductor (layer) with excellent conductivity, the content of metallic copper in the first particles is preferably 50% by mass or more, more preferably 60% by mass or more, and 70% by mass. % or more is more preferable.

The first particles preferably exhibit diffraction peaks at 2θ=44±2°, 2θ=51±2°, and 2θ=75±2° in X-ray diffraction (XRD) using CuKα rays. These peaks correspond to diffraction peaks derived from metallic copper.

X-ray diffraction is measured using, for example, a powder X-ray diffractometer (manufactured by Rigaku Corporation, Geigerflex RAD-2X, CuKα: wavelength (λ)=1.5418 Å).

Since at least part of the surface of the first particles is coated with an organic substance, oxidation of metallic copper is suppressed even during storage in the air, and it is presumed that the content of copper oxide is small. be. Also, the content of copper oxide in the first particles can be measured by, for example, a powder X-ray diffractometer, and the content of copper oxide in the first particles may be 5% by mass or less.

The content of the first particles is preferably 30% by mass to 98% by mass, more preferably 35% by mass to 95% by mass, based on the total amount of the composition, from the viewpoint of the conductivity of the bonded body to be produced. is more preferable, and 40% by mass to 90% by mass is even more preferable.

The method for producing the first particles is not particularly limited. Examples of the production method include the first particle production method of JP-A-2016-037626.

The first method for producing particles disclosed in JP-A-2016-037626 uses a metal salt of a fatty acid having 9 or less carbon atoms and copper as a copper precursor. It is considered that this makes it possible to use an alkylamine having a lower boiling point as a reaction medium than the method described in Patent Document 1 using copper oxalate or the like as a copper precursor. As a result, the organic substance existing on the surface of the obtained first particles is more easily decomposed by heat, and it becomes easier to conduct the conductive formation at a low temperature.

(Second particle)
The second particles are particles containing copper oxide, and the surfaces of the particles are not coated with an organic substance. The second particles are different particles than the first particles. The copper oxide may be at least one selected from the group consisting of copper (I) oxide, copper (II) oxide, and copper oxides having other oxidation numbers. Among these, the copper oxide is preferably copper (I) oxide because it is easily reduced to metallic copper.

In the X-ray diffraction using CuKα rays, the second particles have diffraction peaks derived from metallic copper (for example, the above diffraction peaks of 2θ = 44 ± 2°, 2θ = 51 ± 2°, and 2θ = 75 ± 2°) peak) is not observed (below the detection limit).

The second particles may be commercially available products or those synthesized by a known synthesis method. As a method for synthesizing the second particles, for example, a method of heating a copper acetylacetonato complex in a polyol solvent is known (Angew. Chem. Int. Ed. 2001, 40, 359-362). This synthesis method makes it possible to obtain copper (I) oxide particles having a primary particle size of 100 nm or less.

The average particle size of the second particles is preferably 200 nm or less from the viewpoint of dispersibility in a dispersion medium and smoothness when a composition layer is formed together with oxide particles. The average particle diameter of the second particles is more preferably 80 nm or less, even more preferably 50 nm or less. The average particle size of the second particles is the particle size (D ₅₀ ) when the ratio (volume fraction) to the total volume of the second particles is 50%. The average particle diameter (D ₅₀ ) of the second particles is measured by using a laser scattering particle size measuring device (e.g., Microtrac) to obtain a suspension of the second particles in water by a laser scattering method. It can be obtained by measuring.

The content of the second particles is preferably 0.5 parts by mass to 12 parts by mass, more preferably 0.3 parts by mass to 10 parts by mass with respect to 100 parts by mass of the first particles, More preferably, it ranges from 0.5 parts by mass to 5 parts by mass. When the content of the second particles is 12 parts by mass or less, the dispersibility of the second particles in the dispersion medium tends to be better. When the content of the second particles is 0.5 parts by mass or more, the adhesion of the joined body tends to be further improved.

(dispersion medium)
The dispersion medium is not particularly limited, and can be appropriately selected from organic solvents generally used for producing conductive inks, conductive pastes, etc., depending on the application. A dispersion medium may be used individually by 1 type, or may use 2 or more types together. From the viewpoint of viscosity adjustment, the dispersion medium preferably contains at least one selected from the group consisting of terpineol, isobornylcyclohexanol, dihydroterpineol, and dihydroterpineol acetate.

The content of the dispersion medium is preferably 1 part by mass to 300 parts by mass, more preferably 3 parts by mass to 200 parts by mass, and 5 parts by mass to 150 parts by mass with respect to 100 parts by mass of the first particles. Part is more preferred. When the mass ratio of the dispersion medium is 300 parts by mass or less, the resulting conductor (layer) tends to exhibit better conductivity. Moreover, when it is 1 part by mass or more, the dispersibility tends to be better.

(reducing agent)
The conductor-forming composition may further contain a reducing agent. Here, the reducing agent may be a compound having reducing properties and acting as a dispersion medium. Examples of reducing agents include phenolic compounds such as phloroglucinol and resol, phosphorous compounds such as diisopropyl phosphite and diphenyl phosphite, formic acid compounds such as formic acid and stearylamine formate, dihydroxynaphthoic acid, and dihydroxybenzoic acid. , Aromatic hydroxycarboxylic acid compounds such as 3-hydroxy-2-methylbenzoic acid, Aliphatic hydroxycarboxylic acid compounds such as citric acid, Sugars such as glucose and sucrose, Diglycerin, Ethylene glycol, Dipropylene glycol, Triethylene Polyols such as glycol, organic acid compounds such as ascorbic acid, oxalic acid, glyoxylic acid, alkyl alcohols such as ethanol, propanol, butyl alcohol, alkylamines such as butylamine, pentylamine, hexylamine, 2-ethylhexylamine, etc. is mentioned. One reducing agent may be used alone, or two or more reducing agents may be used in combination. Among these, the reducing agent may be polyols from the viewpoint of compatibility with the dispersion medium.

The content of the reducing agent may be 1 part by mass to 20 parts by mass with respect to 100 parts by mass of the first particles.

(other ingredients)
The conductor-forming composition may contain components other than the first particles, the second particles, the dispersion medium, and the reducing agent as other components. Other components include, for example, a cross-linking agent such as a silane coupling agent. The content of other components may be, for example, 0.1 to 5.0 parts by mass with respect to 100 parts by mass of the first particles.

The viscosity of the conductor-forming composition is not particularly limited and can be selected depending on the application. For example, when the conductor-forming composition is applied to screen printing, the viscosity is preferably 0.1 Pa·s to 30 Pa·s, more preferably 1 Pa·s to 30 Pa·s. When the conductor-forming composition is applied to the spin coating method, the viscosity is preferably 0.3 mPa·s to 1000 mPa·s, more preferably 1 mPa·s to 800 mPa·s. The viscosity of the conductor-forming composition is the viscosity at 25° C. measured using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., product name: VISCOMETER-TV22, applicable cone-plate rotor: 3°×R17.65). means

The method for producing the conductor-forming composition is not particularly limited, and methods commonly used in the art can be used. For example, it can be prepared by dispersing the first particles, the second particles, and optionally the reducing agent and other components in a dispersion medium. Dispersion processing includes media dispersers such as Ishikawa type agitators, rotation/revolution agitators, ultra-thin film high-speed rotary dispersers, roll mills, ultrasonic dispersers, and bead mills, cavitation agitators such as homomixers and Silverson agitators, A facing collision method such as an altemizer can be used. Moreover, you may use these methods, combining them suitably.

<Method for manufacturing joined body>
The manufacturing method of the bonded body of the present embodiment includes a step of preparing a bonding precursor in which a first base material, a composition layer made of the above-described conductor-forming composition, and a second base material are laminated in this order. (bonding precursor preparation step); and a step of heating the bonding precursor at 120° C. to 250° C. in a gas atmosphere of an inert gas, a reducing gas, or a mixed gas thereof (heating step). Prepare. An example of a method for manufacturing a joined body will be described below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view for explaining an embodiment of a method for producing a joined body using a conductor-forming composition. As shown in FIG. 1, the method of the present embodiment comprises a first substrate 1, a composition layer 3 comprising the above conductor-forming composition and containing first particles 4a and second particles 4b, A bonding precursor 10 in which the second base materials 2 are laminated in this order is prepared (FIG. 1(a)). The bonding precursor 10 is formed by, for example, forming a composition layer 3 containing first particles 4a and second particles 4b on a first base material using the above-described conductor-forming composition. It can be obtained by placing a second substrate 2 on layer 3 . Next, the prepared bonding precursor 10 is heated at a specific temperature in a specific gas atmosphere (FIG. 1(b)). At this time, for example, the heating may be performed from the direction A while applying a load (pressurizing). By going through these steps, a joined body 20 comprising a first base material 1, a second base material 2, and a conductor layer 5 that joins the first base material 1 and the second base material 2 is obtained (FIG. 1(c)). The conductor layer 5 includes a sintered body obtained by sintering the first particles 4a and the second particles 4b contained in the conductor-forming composition.

The first substrate 1 contains metal in the substrate. Specific examples of metals include metals such as gold, silver, copper, platinum, palladium, zinc, nickel, tin, cobalt, iron, and aluminum, and alloys containing these metals. The substrate may be a metallic copper substrate. Also, the substrate may have a curved surface.

The ratio of the first particles 4a and the second particles 4b to the entire first base material 1 is preferably 50% by mass or more, more preferably 70% by mass or more, and 80% by mass or more. is more preferable, and 90% by mass or more is particularly preferable. When the ratio of the first particles and the second particles is 50% by mass or more, there is a tendency to easily form a metallic bond between the obtained conductor (layer) and the metal contained in the substrate.

The method for forming the composition layer 3 on the first base material 1 is not particularly limited as long as the composition layer 3 can be formed on the base material in an arbitrary shape. Such methods include, for example, an inkjet method, a super inkjet method, a screen printing method, a transfer printing method, an offset printing method, a jet printing method, a dispensing method, a jet dispensing method, a needle dispensing method, a comma coating method, and a bar coating method. , slit coating method, die coating method, gravure coating method, relief printing method, intaglio printing method, gravure printing method, soft lithography method, dip pen lithography method, particle deposition method, spray coating method, spin coating method, dip coating method, electro Examples include a coating method and the like.

The shape and thickness of the composition layer 3 are not particularly limited and can be appropriately selected according to the purpose. Moreover, the thickness of the composition layer 3 is preferably, for example, 0.2 μm to 2000 μm. From the viewpoint of electrical conductivity and connection reliability of the joined body, it is more preferably 1 μm to 1000 μm.

As the second base material 2, those exemplified for the first base material 1 can be used. The second substrate 2 may be the same as the first substrate 1 or may be different.

In the heating step, the bonding precursor is heated under specific temperature conditions in a specific atmosphere. As a result, the joined body 20 including the first base material 1, the second base material 2, and the conductor layer 5 that joins the first base material 1 and the second base material 2 is obtained.

The gas atmosphere in the heating step is an inert gas such as nitrogen or argon, a reducing gas such as hydrogen or formic acid, or a mixed gas of these inert gases and reducing gases. The gas atmosphere may be a reducing gas atmosphere containing hydrogen gas or formic acid gas. By heating in a reducing gas atmosphere, desorption of organic matter on the surface of the first particles and reduction of copper oxide contained in the second particles to metallic copper are facilitated, and core particles containing copper of the particles are separated from each other. and promotes sintering (fusion) between the metal contained in the base material and the copper contained in the core particles.

The atmospheric pressure conditions in the atmosphere in the heating step are not particularly limited, and may be atmospheric pressure conditions or reduced pressure conditions. tend to be promoted.

The temperature condition in the heating step is in the range of 120°C to 250°C, preferably in the range of 120°C to 230°C. When the temperature is 120° C. or higher, a conductor (layer) having sufficient conductivity tends to be obtained. The temperature rising conditions in the heating step may be raised at a constant rate, or may be raised at an irregular rate. The heating time in the heating step is not particularly limited, and can be selected in consideration of the heating temperature, the heating atmosphere, the amount of particles, and the like. Moreover, the heating method is not particularly limited, and heating can be performed using a hot plate, an infrared heater, a pulse laser, or the like.

The method for manufacturing a joined body may include other steps as necessary. Other steps include a step of removing residual components by immersion in water or an organic solvent after the heating step, and a step of removing residual components by photobaking after the heating step.

The volume resistivity of the conductor (layer) produced using the conductor-forming composition of the present invention is preferably 1000 μΩ·cm or less, more preferably 500 μΩ·cm or less, and 300 μΩ·cm or less. It is more preferable that the resistance is 200 μΩ·cm or less. The shape of the conductor (layer) is not particularly limited, and may be a thin film shape, a bump shape, a pattern shape, or the like.

<Joint body>
The joined body of this embodiment includes a first base material, a second base material, and a conductor layer that joins the first base material and the second base material. The conductor layer includes a structure in which the first particles and the second particles contained in the conductor-forming composition are sintered. The bonded body can be used as a member such as a connection terminal used in electronic parts such as a solar cell, a display, a touch panel, a transistor, a semiconductor package, a laminated ceramic capacitor, and a heat dissipation film. The bonded body of this embodiment can be used, for example, in place of a bonded body manufactured by conventional solder bonding.

A method for measuring the bonding strength of the bonded body is appropriately selected depending on the shape of the manufactured bonded body. Examples include a pull strength test in which the bonded body is peeled off in a direction perpendicular to the bonding surface, a shear strength test in which the bonded body is peeled off in a direction horizontal to the bonding surface, a peel strength test in which a flexible thin film is peeled off, and the like.

EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to these.

[Production Example 1] Synthesis of copper nonanoate 150 mL of 1-propanol (Kanto Chemical Co., Ltd., special grade) was added to 91.5 g (0.94 mol) of copper hydroxide (Kanto Chemical Co., special grade) and stirred. 370.9 g (2.34 mol) of nonanoic acid (Kanto Kagaku Co., Ltd., 90% or more) was added. The obtained mixture was heated and stirred at 90° C. for 30 minutes in a separable flask. The resulting solution was filtered while being heated to remove undissolved matter. After that, it was allowed to cool, and the copper nonanoate formed was filtered by suction and washed with hexane until the washing liquid became clear. The resulting powder was dried in an explosion-proof oven at 50° C. for 3 hours to obtain copper (II) nonanoate. The yield was 340 g (yield 96% by mass).

[Production Example 2] Synthesis of first particles 15.01 g (0.040 mol) of copper (II) nonanoate obtained above and 7.21 g of copper (II) acetate anhydride (Kanto Chemical Co., Ltd., special grade) ( 0.040 mol) is placed in a separable flask, 22 mL of 1-propanol and 32.1 g (0.32 mol) of hexylamine (Tokyo Chemical Industry Co., Ltd.) are added, and dissolved by heating and stirring at 80 ° C. in an oil bath. rice field. After the mixture was transferred to an ice bath and cooled to an internal temperature of 5°C, 7.72 mL (0.16 mol) of hydrazine monohydrate (Kanto Chemical Co., Ltd., special grade) was added, and the mixture was further stirred in an ice bath. The molar ratio of copper:hexylamine is 1:4. Then, the mixture was heated and stirred at 90° C. for 10 minutes in an oil bath. At that time, a reduction reaction accompanied by foaming progressed, the inner wall of the separable flask exhibited a copper luster, and the solution turned dark red. Centrifugation was performed at 9000 rpm (revolutions per minute) for 1 minute to obtain a solid material. The step of washing the solid with 15 mL of hexane was repeated three times to remove the acid residue and obtain a copper cake containing first particles with copper luster.

The first particles synthesized in Production Example 2 were analyzed using a powder X-ray diffractometer (Geigerflex RAD-2X manufactured by Rigaku Corporation, X-ray source: CuKα rays, diffraction angle range 30 to 80°). FIG. 2 shows the X-ray diffraction (XRD) spectrum of the first particles in the diffraction angle range of 30-80°. It was confirmed to have peaks at 2θ=43.7°, 50.9°, and 74.6° in X-ray diffraction. From this X-ray diffraction (XRD) spectrum, it was confirmed that the first particles contained metallic copper and almost no copper oxide.

[Examples 1 to 6, Comparative Example 1]
Copper cake synthesized above as the first particles, copper (I) oxide particles as the second particles (Takiron C.I. Co., Ltd., product name Nano Tek (registered trademark), average particle size: 48 nm), terpineol as a dispersion medium ( Wako Pure Chemical Industries, Ltd.) and isobornylcyclohexanol (Terusolv MTPH, Nippon Terpene Chemical Co., Ltd.), and ethylene glycol (Wako Pure Chemical Industries, Ltd.) as a reducing agent were mixed in the blending mass parts shown in Table 1. A conductor-forming composition was prepared. Visual inspection of the resulting conductor-forming composition revealed that the composition as a whole was in the form of a homogeneous paste, and that the first particles and the second particles had good dispersibility.

Using the conductor-forming compositions of Examples 1 to 6 and Comparative Example 1, joined bodies were produced. More specifically, a stencil plate having a size of 2×2 mm and a thickness of 0.1 mm was prepared on a metallic copper substrate (first substrate) from which the conductor-forming composition had been ultrasonically cleaned with acetone in advance to remove organic substances. A composition layer was formed by stencil printing using. A 2×2 mm, 0.25 mm thick copper substrate (second substrate) was then placed over the composition layer on the first substrate. After that, heat treatment was performed to obtain joined bodies of Examples 1 to 6 and Comparative Example 1. An atmosphere-controlled thermocompression bonding apparatus (RF-100B, Ayumi Industry Co., Ltd.) was used for the heat treatment. The heat treatment was carried out by heating to 250° C. at a temperature increase rate of 30° C./min under a nitrogen gas atmosphere under negative pressure (8.5×10 ⁴ Pa), followed by introducing a mixed gas of nitrogen and formic acid. 0×10 ⁴ Pa and maintained at 250° C. for 60 minutes.

(bonding strength measurement)
The resulting joined bodies were evaluated by die shear strength (MPa). Using a universal bond tester (4000 series, Nordson Advanced Technology Co., Ltd.) equipped with a DS-100 load cell, the copper substrate (second substrate) is horizontally measured at a measurement speed of 100 μm/sec and a measurement height of 12 μm. After pressing, the die shear strength (MPa) of the joined body was measured. Table 1 shows the results.

The die shear strengths of the joined bodies of Examples 1 to 4 produced using the conductor-forming composition containing the second particles were compared with those of Comparative Example 1 produced using the conductor-forming composition containing no second particles. It was 3 to 14 times better than the die shear strength of the bonded body. In addition, the die shear strength of the joined bodies of Examples 5 and 6, which were produced using the conductor-forming composition further containing a reducing agent, was 17 to 18 times superior to the die shear strength of the joined body of Comparative Example 1. was

From the above, it was confirmed that the conductor-forming composition of the present invention can be formed into a conductor at 250° C. or lower and can be used as a metal bonding material.

DESCRIPTION OF SYMBOLS 1... First base material, 2... Second base material, 3... Composition layer, 4a... First particle, 4b... Second particle, 5... Conductor layer, 10... Bonding precursor, 20... Bonding body.

Claims (5)

a first particle having a core particle containing metallic copper and an organic substance covering at least part of the surface of the core particle;
second particles comprising copper oxide;
a dispersion medium;
contains
The organic substance contains an alkylamine having a hydrocarbon group with 7 or less carbon atoms,
The conductor-forming composition , wherein the content of the second particles is 0.5 parts by mass to 5 parts by mass with respect to 100 parts by mass of the first particles . The conductor-forming composition according to claim 1 , further comprising a reducing agent. a step of preparing a bonding precursor in which a first substrate, a composition layer made of the conductor-forming composition according to claim 1 or 2 , and a second substrate are laminated in this order;
heating the bonding precursor at 120° C. to 250° C. in a gas atmosphere of an inert gas, a reducing gas, or a mixed gas thereof;
A method of manufacturing a joined body, comprising: 4. The method for manufacturing a joined body according to claim 3 , wherein the gas atmosphere is an atmosphere containing hydrogen gas or formic acid gas. A first base material, a second base material, and a conductor layer that joins the first base material and the second base material,
A joined body, wherein the conductor layer includes a sintered body obtained by sintering the first particles and the second particles contained in the conductor-forming composition according to claim 1 or 2 .

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