Sheet-like bonding material and method for producing same, and bonded body and method for producing same

Abstract

Provided is a bonding material with which sufficient bonding strength can be obtained even when low-temperature bonding is performed at 250 DEG C or less, and with which it is possible to achieve bonding in which unevenness does not easily occur between a sintered state in which a central portion of a pressurized bonding surface is sintered and a sintered state in which a pressurized edge portion is sintered. This sheet-like bonding material contains copper particles and a reducing agent for reducing the copper particles, and is characterized in that the copper particles contain fine copper particles having an average particle diameter of 300 nm or less and optionally contained coarse copper particles having an average particle diameter of 3-11 [mu] m (inclusive), with respect to the total content of the fine copper particles and the coarse copper particles, the total content of the fine copper particles and the coarse copper particles being greater than the total content of the fine copper particles and the coarse copper particles being greater than the total content of the fine copper particles and the coarse copper particles. The content of the fine copper particles is 50-100% by mass (inclusive), the reducing agent is composed of triethanolamine, and the content of the triethanolamine is 1.5-10.0% by mass (inclusive) with respect to the total content of the fine copper particles and the coarse copper particles.

Description

Technical Field

[0001] The present invention relates to a sheet-like bonding material, a method for manufacturing the sheet-like bonding material, a bonded body, and a method for manufacturing the bonded body. Background Art

[0002] Conventionally, a solder material has been generally used as a bonding material for electronic components. However, the solder material has a problem of poor heat resistance. Therefore, for example, in a power device using a silicon carbide (SiC) element that is expected to be used at a temperature of 150°C or higher, it is difficult to use the solder material as a bonding material.

[0003] Therefore, as a sintered bonding material, a bonding material using silver particles has been proposed. In addition, copper nanoparticles are highly expected from the viewpoints of cost and ion migration.

[0004] Patent Document 1 describes "a plate-like or sheet-like bonding material containing a sintered body of fine particles mainly composed of copper with an average particle diameter of 300 nm or less, and the resistivity value of the bonding material is 1×10 -5 Ω·m or less", so that a high bonding force can be exhibited even when two or more members to be bonded are bonded in an inert atmosphere.

[0005] However, although bonding in an inert atmosphere can be achieved in Patent Document 1, when manufacturing the sheet-like bonding material, since sintering is performed while applying pressure to copper nanoparticles in a reducing atmosphere, a reducing gas is required, and there are limitations in gas equipment such as exhaust gas treatment. In addition, since the copper nanoparticles are sintered by the reducing gas, the surface activity unique to the nanoparticles is impaired, and there are also problems of unstable performance depending on the sintering state.

[0006] Therefore, in Patent Documents 2 and 3, a sheet-like bonding material is proposed, which can achieve stable bonding in an inert atmosphere without requiring a reducing gas by adding a reducing agent during the production of the sheet-like bonding material. Specifically, Patent Document 2 describes "a plate-like or sheet-like bonding material containing copper fine particles mainly composed of copper with an average particle diameter of 300 nm or less, and further containing a reducing agent for reducing the copper fine particles", and Patent Document 3 describes "a plate-like or sheet-like bonding material containing copper fine particles with an average particle diameter of 300 nm or less, copper coarse particles with an average particle diameter of 3 μm or more and 11 μm or less, and a reducing agent for reducing the copper fine particles and the copper coarse particles". As the reducing agent, for example, polyol solvents such as ethylene glycol and organic acids.

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: Japanese Patent Laid-Open No. 2018-12871

[0010] Patent Document 2: Japanese Patent Laid-Open No. 2019-203172

[0011] Patent Document 3: Japanese Patent Laid-Open No. 2021-116450 Summary of the Invention

[0012] Problems to be Solved by the Invention

[0013] However, for the sheet-like bonding materials described in Patent Document 2 and Patent Document 3, in the case of low-temperature bonding at 250°C or lower, the reducing effect of the reducing agent cannot be fully exerted, so there are problems such as insufficient bonding strength and uneven sintering states between the central part and the pressure-applied edge part of the pressure-applied bonding surface.

[0014] In view of the above problems, an object of the present invention is to provide a bonding material and a preferred manufacturing method thereof, which can obtain sufficient bonding strength even in the case of low-temperature bonding at 250°C or lower, and can achieve bonding with less unevenness between the sintering states of the central part and the pressure-applied edge part of the pressure-applied bonding surface.

[0015] In addition, an object of the present invention is to provide a bonded body that realizes the above-mentioned good bonding using such a bonding material and a preferred manufacturing method thereof.

[0016] Means for Solving the Problems

[0017] The general configuration of the present invention for solving the above problems is as follows.

[0018] [1] A sheet-like bonding material, characterized in that:

[0019] It contains copper particles and a reducing agent for reducing the copper particles,

[0020] The copper particles contain copper fine particles with an average particle size of 300 nm or less and selectively contained copper coarse particles with an average particle size of 3 μm or more and 11 μm or less,

[0021] The content of the copper fine particles is 50% by mass or more and 100% by mass or less relative to the total content of the copper fine particles and the copper coarse particles,

[0022] The reducing agent consists of triethanolamine, and the content of the triethanolamine is 1.5% by mass or more and 10.0% by mass or less relative to the total content of the copper fine particles and the copper coarse particles.

[0023] [2] The sheet-like bonding material according to [1] above, wherein the ratio of the oxygen mass concentration of the copper fine particles to the specific surface area is 0.1% by mass·g / m 2 or more and 1.2% by mass·g / m 2 or less.

[0024] [3] The sheet-like bonding material according to [1] or [2] above, wherein the ratio of the carbon mass concentration of the copper fine particles to the specific surface area is 0.008% by mass·g / m 2 or more and 0.3% by mass·g / m 2 or less.

[0025] [4] A method for manufacturing a sheet-like bonding material, characterized by comprising:

[0026] a mixing step of mixing copper particles and a reducing agent for reducing the copper particles to obtain a mixture; and

[0027] a pressure molding step of pressure molding the mixture to obtain a sheet-like bonding material,

[0028] wherein the copper particles contain copper fine particles with an average particle size of 300 nm or less and optionally contained copper coarse particles with an average particle size of 3 μm or more and 11 μm or less,

[0029] in the mixture, the content of the copper fine particles is 50% by mass or more and 100% by mass or less relative to the total content of the copper fine particles and the copper coarse particles,

[0030] the reducing agent consists of triethanolamine, and in the mixture, the content of the triethanolamine is 1.5% by mass or more and 10.0% by mass or less relative to the total content of the copper fine particles and the copper coarse particles.

[0031] [5] The method for manufacturing a sheet-like bonding material according to [4] above, wherein the mixing step includes a step of mixing the copper particles, the reducing agent, and an organic solvent to obtain a slurry, and a step of drying the slurry to obtain the mixture.

[0032] [6] A bonded body, which has a first component, a second component, and the bonding material according to any one of [1] to [3] above,

[0033] and the bonding material is located between the first component and the second component.

[0034] [7]A method for manufacturing a bonded body, comprising the following steps: pressurizing in a state where the bonding material according to any one of [1] to [3] above is disposed between a first member and a second member, to obtain a bonded body in which the first member and the second member are bonded by the bonding material.

[0035] [8]The method for manufacturing a bonded body according to [7] above, wherein the bonding temperature is set to 250°C or lower.

[0036] Advantages of the Invention

[0037] According to the bonding material of the present invention, even in the case of low-temperature bonding at 250°C or lower, sufficient bonding strength can be obtained, and a bonding in which non-uniformity is unlikely to occur between the sintered state at the center of the pressure-bonded surface and the sintered state at the pressure-bonded edge can be achieved. According to the method for manufacturing the bonding material of the present invention, such a bonding material can be manufactured.

[0038] The bonded body of the present invention uses such a bonding material to achieve the good bonding as described above. According to the method for manufacturing the bonded body of the present invention, a bonded body that achieves the good bonding as described above can be manufactured using such a bonding material. Detailed Description of the Invention

[0039] [Sheet-like Bonding Material]

[0040] The sheet-like bonding material according to an embodiment of the present invention includes copper particles and a reducing agent for reducing the copper particles. The copper particles include copper fine particles (also referred to as "copper nanoparticles") and copper coarse particles, and are preferably composed of copper fine particles and copper coarse particles. Here, "copper fine particles" refers to copper particles having a particle size of less than 800 nm, and "copper coarse particles" refers to copper particles having a particle size of 800 nm or more.

[0041] (Copper Fine Particles)

[0042] The copper fine particles have copper as the main component. In the copper fine particles, relative to 100 mass% of the copper fine particles, it is preferable to contain 95 mass% or more and 100 mass% or less of copper element, and more preferably to contain 97 mass% or more of copper element. When containing 95 mass% or more of copper element, the heat resistance of the bonding material is excellent and the bonding force is better.

[0043] The average particle size of the copper fine particles is 300 nm or less. However, the average particle size of the copper fine particles is more preferably 150 nm or less. By making the average particle size of the copper particles 300 nm or less, the bonding force of the bonding material is excellent. The average particle size of the copper fine particles is preferably 5 nm or more. If the average particle size of the copper fine particles is 5 nm or more, it becomes easier to obtain the copper fine particles.

[0044] The particle size distribution of the copper fine particles does not overlap with that of the copper coarse particles. For example, the particle size distribution of the copper fine particles can be D10: 40 nm, D50: 110 nm, D90: 300 nm.

[0045] The shape (morphology) of the copper fine particles is not particularly limited. Examples of the shape of the copper fine particles include spherical (sphere), elliptical (ellipsoid), plate-like, etc. Among them, spherical or elliptical is preferred, and spherical is more preferred.

[0046] Using a scanning electron microscope (SEM), observe the copper fine particles in 10 fields of view at a magnification of 10,000 times. For all the copper fine particles (copper particles with a particle size less than 800 nm) selected according to the following selection criteria (1) to (5) in the 10 fields of view, measure the particle size of each copper fine particle, and calculate its arithmetic mean, so as to determine the average particle size of the copper fine particles. In addition, for non-circular particles such as ellipses, use the major axis as the particle size. In addition, the particle size distribution of the copper fine particles is also determined based on the particle sizes of all the copper fine particles that are the above-mentioned measurement objects. Here, when obtaining the average particle size and particle size distribution of the copper fine particles in the sheet-like bonding material, observe the outermost surface part of the sheet. In the powder state before sheet production, place the powder on a carbon adhesive tape with a spatula, remove the excess powder with an air dust remover, and observe the surface of the tape.

[0047] (1) Do not measure the particles whose local part exceeds the image field of view.

[0048] (2) Measure the particles with clear contours and isolated existence.

[0049] (3) Even in the case of particles with a shape deviating from the average, measure the independent particles that can be measured as individual particles.

[0050] (4) For the particles that overlap with each other but have clear boundaries between the two and the overall shape of the particles can be judged, measure each particle as an individual particle.

[0051] (5) For the overlapping particles with unclear boundaries and unable to judge the overall shape of the particles, do not measure them as particles with an undetermined particle shape.

[0052] As the copper fine particles, it is preferable to use copper fine particles that do not require a protective agent, a dispersant, etc. As such copper fine particles, for example, the metal ultrafine powder obtained by the manufacturing method described in Japanese Patent No. 4304221. However, the copper fine particles are not limited to this example.

[0053] The copper particles preferably have a copper carbonate-containing coating film on the surface. By making the copper particles have a copper carbonate-containing coating film on the surface, compared with the prior art, the sintering temperature of the copper particles can be suppressed to be lower, and at the same time, the bonding strength can be improved. In addition, when the copper particles containing copper carbonate are sintered, the copper coarse particles will neck, making the entire copper sintered layer firm. The copper carbonate-containing coating film may also contain copper suboxide.

[0054] From the viewpoints of reducing the reactivity with oxygen in the air and reducing the influence of re-oxidation, the ratio of the oxygen mass concentration of the copper particles to the specific surface area is preferably 0.1 mass%·g / m 2 or more, and more preferably 0.2 mass%·g / m 2 or more. On the other hand, from the viewpoints of easily removing the oxide film during bonding and further improving the bonding strength, the ratio of the oxygen mass concentration of the copper particles to the specific surface area is preferably 1.2 mass%·g / m 2 or less, and more preferably 0.5 mass%·g / m 2 or less.

[0055] From the viewpoints of suppressing the generation of voids and cracks and further improving the bonding strength, the ratio of the carbon mass concentration of the copper particles to the specific surface area is preferably 0.3 mass%·g / m 2 or less, and more preferably 0.1 mass%·g / m 2 or less, and further preferably 0.05 mass%·g / m 2 or less. The ratio of the carbon mass concentration of the copper particles to the specific surface area is preferably 0.008 mass%·g / m 2 or more.

[0056] The ratio of the oxygen mass concentration of the copper particles to the specific surface area can be calculated based on the separately measured specific surface area and oxygen mass concentration. The specific surface area can be measured using a BET adsorption device for nitrogen (for example, "MACSORB HM-1201" manufactured by Mountech Co., Ltd., Japan). The oxygen mass concentration can be measured using an oxygen-nitrogen analyzer (for example, "TC600" manufactured by LECO Corporation).

[0057] The ratio of the carbon mass concentration of the copper particles to the specific surface area can be calculated based on the separately measured specific surface area and carbon mass concentration. The specific surface area can be measured using a BET adsorption device for nitrogen (for example, "MACSORB HM-1201" manufactured by Mountech Co., Ltd., Japan). The carbon mass concentration can be measured using a carbon-sulfur analyzer (for example, "EMIA-920V" manufactured by Horiba, Ltd., Japan).

[0058] (Copper coarse particles)

[0059] The bonding material of this embodiment may selectively contain coarse copper particles. The coarse copper particles mainly contain copper. In the coarse copper particles, relative to 100% by mass of the coarse copper particles, it is preferably to contain 95% by mass or more and 100% by mass or less of copper element, and more preferably to contain 97% by mass or more of copper element. If it contains 95% by mass or more of copper element, the sinterability of the bonding material is excellent and the bonding strength is better.

[0060] The average particle size of the coarse copper particles is 3 μm or more and 11 μm or less. If the average particle size of the coarse copper particles is 3 μm or more, the shrinkage of the copper fine particles during sintering of the bonding material is reduced, and cracks in the bonded components can be suppressed. From this perspective, the average particle size of the coarse copper particles is preferably 5 μm or more. If the average particle size of the coarse copper particles is 11 μm or less, while maintaining the effect of reducing the shrinkage of the copper fine particles, the bonding material can be sufficiently sintered and the bonding strength of the bonded body will not be impaired. From this perspective, the average particle size of the coarse copper particles is preferably 9 μm or less.

[0061] The particle size distribution of the coarse copper particles does not overlap with the particle size distribution of the copper fine particles. For example, the particle size distribution of the coarse copper particles can be D10: 1.9 μm, D50: 3.8 μm, D90: 8.2 μm.

[0062] The shape (morphology) of the coarse copper particles is not particularly limited. Examples of the shape of the coarse copper particles include spherical (sphere), elliptical (ellipsoid), plate-shaped (flaky), etc. Among them, spherical or elliptical is preferred, and elliptical is more preferred.

[0063] As the coarse copper particles, for example, commercially available flaky copper such as "MA-C03KP" manufactured by Mitsui Mining & Smelting Co., Ltd., "MA-C025KFD" manufactured by Mitsui Mining & Smelting Co., Ltd., and commercially available micron copper such as "1300Y" manufactured by Mitsui Mining & Smelting Co., Ltd. can be used.

[0064] Using a scanning electron microscope (SEM) to observe 10 fields of view of copper particles at a magnification of 2000 times, for all the coarse copper particles (copper particles with a particle size of 800 nm or more) selected according to the following selection criteria (1) to (5) in the 10 fields of view, by measuring the particle size of each coarse copper particle and calculating its arithmetic mean, the average particle size of the coarse copper particles can be determined. In addition, for non-circular particles such as ellipses, the major axis is used as the particle size. In addition, the particle size distribution of the coarse copper particles is also determined based on the particle sizes of all the coarse copper particles as the above measurement objects. Here, when determining the average particle size and particle size distribution of the coarse copper particles in the sheet-shaped bonding material, the outermost surface part of the sheet is observed. In the powder state before sheet production, place the powder on the carbon adhesive tape with a spatula, remove the excess powder with an air dust collector, and observe the surface of the tape.

[0065] (1) Particles that are locally outside the photo field of view are not measured.

[0066] (2) Particles with clear contours and isolated existence are measured.

[0067] (3) Even in the case of particles with a shape deviating from the average, particles that are independent and can be measured as individual particles are measured.

[0068] (4) For particles that overlap with each other, but whose boundaries are clear and the overall shape of the particles can be judged, each particle is measured as an individual particle.

[0069] (5) For particles among the overlapping particles whose boundaries are not clear and the overall shape of the particles cannot be judged, they are not measured as particles with an undetermined shape.

[0070] (Mass ratio of copper fine particles and copper coarse particles)

[0071] With respect to the total content of copper fine particles and copper coarse particles, the content of copper fine particles is 50% by mass or more and 100% by mass or less, preferably 75% by mass or more, more preferably 100% by mass. In other words, with respect to the total content of copper fine particles and copper coarse particles, the content of copper coarse particles is 0% by mass or more and 50% by mass or less, preferably 25% by mass or less, more preferably 0% by mass. Thus, a bonding material having sufficient bonding strength can be produced.

[0072] The "content of copper fine particles with respect to the total content of copper fine particles and copper coarse particles" in the sheet-like bonding material can be calculated, for example, by placing the sheet in an organic solvent such as isopropyl alcohol, centrifuging the dispersed liquid after ultrasonic dispersion to separate the copper fine particles from the copper coarse particles, and measuring their respective weights.

[0073] (Reducing agent)

[0074] The reducing agent is a compound that reduces copper fine particles and copper coarse particles. The reducing agent is preferably a compound that can function as a dispersion medium for the dispersion of copper fine particles and copper coarse particles. A compound that can function as a dispersion medium is preferably a compound that is liquid at room temperature, more preferably a compound that vaporizes at a high temperature of 150 °C or higher. Thus, during bonding, the reducing agent vaporizes, and the reducing agent is not easily left in the bonded body described later. As a result, voids and cracks are not easily generated, and the bonding strength is better.

[0075] As a reducing agent that can function as a dispersion medium, an amine solvent is preferred. Specific examples include ethanolamine, diethanolamine, and triethanolamine. However, in the present embodiment, it is characterized in that the reducing agent consists of triethanolamine. Thus, even for low-temperature bonding below 250°C, sufficient bonding strength can be obtained, and a bonding state can be achieved in which unevenness is less likely to occur between the sintering state at the center of the pressure-bonded surface and the sintering state at the pressure-bonded edge. The reason why using triethanolamine as the reducing agent can achieve this effect is not yet clear, but the inventors of the present application believe there are the following points. It is speculated that the reducing agent present in the pressure center is difficult to escape to the outside, while the reducing agent present around the pressure edge is easy to escape to the outside. For a reducing agent such as triethanolamine with a high boiling point and low volatility, even at the pressure edge, it is difficult for the reducing agent to escape to the outside, and since it remains at a temperature of around 200°C until the reduction of copper particles begins, it is difficult to produce sintering unevenness.

[0076] Relative to the total content of 100% by mass of copper particles and copper coarse particles, the content of the reducing agent, i.e., triethanolamine, is preferably 1.5% by mass or more, more preferably 3.8% by mass or more, and still more preferably 5.5% by mass or more. Thus, the bonding force during bonding in a nitrogen atmosphere is more excellent, and a higher bonding force can be obtained compared to the bonding force during bonding in a reducing atmosphere, and there is less sintering unevenness between the pressure center and the edge.

[0077] Relative to the total content of 100% by mass of copper particles and copper coarse particles, the content of the reducing agent, i.e., triethanolamine, is preferably 10.0% by mass or less, more preferably 7.5% by mass or less. Thus, voids and cracks are less likely to occur, the bonding force is more excellent, and it is easy to form the bonding material into a plate shape or a sheet shape.

[0078] It should be noted that the content of the reducing agent in the sheet-shaped bonding material is equal to the content of the reducing agent in the mixture. However, the "content of the reducing agent" in the sheet-shaped bonding material can be measured, for example, by the weight reduction from 175°C to 600°C in the thermogravimetric test of the sheet bonding material to determine the amount of the reducing agent, and then the "content of the reducing agent" can be calculated.

[0079] (Other components)

[0080] Within the range that does not affect the effects of the present invention, in addition to copper particles and a reducing agent, the bonding material of the present embodiment may further contain optional components such as a dispersant. However, relative to the copper particles, the content of the optional components is preferably 2% by mass or less.

[0081] (Sheet-shaped)

[0082] The bonding material of the present embodiment is in sheet form, so it is easier to handle compared to the paste-like products of the prior art. Further, even when the bonding material is stored for a long time, it is easy to maintain the dispersibility of the copper particles. In addition, there is no need for cryopreservation, nor is there a need to mix an excessive amount of dispersant. Therefore, the quality of the bonding material and the bonding body described later is excellent.

[0083] The bonding material of the present embodiment, as described later, is a bonding material in sheet form obtained by mixing copper particles with a required reducing agent and subjecting the mixture to pressure molding. Here, the thickness of the bonding material (the thickness in the pressing direction) is not particularly limited. For example, it can be 100 μm or more and less than 1 mm.

[0084] In addition, the shape of the bonding material (the shape when viewed from the thickness direction) is not particularly limited and can be appropriately selected according to the shape of the bonding surface of the component to be bonded, etc. It can also be the shape of the pressing surface when the above mixture is pressure molded at a required pressure to form a sheet. Specifically, for example, a rectangle or a circle can be cited.

[0085] [Manufacturing method of sheet-like bonding material]

[0086] The manufacturing method of the sheet-like bonding material according to an embodiment of the present invention is preferably a method for manufacturing the sheet-like bonding material according to an embodiment of the present invention described above.

[0087] Therefore, the details and preferred forms of the copper fine particles, copper coarse particles, and reducing agent are the same as those described in the item [Sheet-like bonding material]. In addition, regarding the respective contents of the copper fine particles, copper coarse particles, and reducing agent, they are also the same as those described above in the item [Sheet-like bonding material].

[0088] In the manufacturing method of the sheet-like bonding material of the present embodiment, first, a mixing step of mixing copper particles (copper fine particles and optional copper coarse particles) with a reducing agent for reducing the copper particles to obtain a mixture is performed. The method of mixing the copper particles and the reducing agent is not particularly limited. As the mixing method, for example, methods such as using a rotation-revolution type mixer, mortar, grinding machine stirring, and stirrer stirring can be cited.

[0089] The viscosity of triethanolamine as a reducing agent is very high, and it is difficult to uniformly mix with copper particles. Therefore, it is preferable to add an organic solvent to the copper particles and triethanolamine, mix them to obtain a slurry, and dry the slurry to volatilize the organic solvent, thereby obtaining a mixture. The organic solvent is preferably an alcohol or ketone solvent with a low boiling point (less than 100 °C) and high volatility. If a low-boiling-point and high-volatility organic solvent is used, in the temperature range where triethanolamine is difficult to evaporate (less than 100 °C), it is easy to remove the dilution organic solvent that is not required for the bonding material, so it has the advantage that the concentration of triethanolamine required for the reduction and sintering of copper particles hardly changes.

[0090] In the method for manufacturing the sheet-like bonding material of the present embodiment, a compression molding step of compression molding the mixture obtained in the mixing step to obtain the sheet-like bonding material is then performed. The method of compression is not particularly limited. As the method of compression, for example, a method using a metal jig, a compression molding machine, etc. can be cited.

[0091] The atmosphere during compression is not particularly limited and can be an inert atmosphere or an air atmosphere. However, from the perspective of convenience, compression is preferably performed in the air.

[0092] The pressure during compression is preferably 10 MPa or more, more preferably 40 MPa or more. If the pressure during compression is 10 MPa or more, the durability of the bonding material formed into a sheet becomes higher. In addition, the higher the compression pressure, the higher the density of the copper fine particles contained in the bonding material, and the higher the shear strength of the bonding surface of the bonded body. On the other hand, if the pressure during compression is too high, cracks may occur in the molded body, so the pressure during compression is preferably 500 MPa or less.

[0093] The molding temperature during compression is not limited, but considering operability, molding is preferably performed at room temperature (10°C to 30°C). The molding time during compression is not particularly limited and can be, for example, 1 minute or more and 10 minutes or less.

[0094] [Bonded body]

[0095] The bonded body of one embodiment of the present invention has a first member (first member to be bonded), a second member (second member to be bonded), and the above-described bonding material according to one embodiment of the present invention. The bonded body is a bonded product in which the compressed product of the bonding material is located between the first member and the second member and the first member and the second member are bonded by the bonding material.

[0096] The materials of the first member and the second member are not particularly limited as long as they can be bonded when compression-bonded using the above-described bonding material. Examples of such materials include metals such as copper, silicon, aluminum, copper oxide, silicon oxide, aluminum oxide, silicon nitride, aluminum nitride, boron nitride, and silicon carbide; alloys thereof; mixtures thereof, etc. The first member and the second member can be made of a single material alone or two or more materials can be used in combination. The first member and the second member can be made of the same material or different materials.

[0097] The shear strength of the joint surface between the first component and the second component is preferably 35 MPa or more, more preferably 45 MPa or more, and still more preferably 55 MPa or more. If the shear strength of the joint surface between the first component and the second component is 35 MPa or more, the bonding material is less likely to peel off from the components to be joined even when the joined body is repeatedly subjected to thermal shock, and the bonding reliability is excellent.

[0098] The shear strength can be adjusted according to the content of the reducing agent in the bonding material, the pressure during compression molding of the bonding material, the pressure during bonding, and the atmosphere conditions during bonding (reducing atmosphere or inert atmosphere).

[0099] [Method for manufacturing a joined body]

[0100] The method for manufacturing a joined body according to an embodiment of the present invention includes the following step: applying pressure in a state where the above-described bonding material according to an embodiment of the present invention is disposed between a first component and a second component to obtain a joined body in which the first component and the second component are joined by the bonding material.

[0101] The bonding conditions are not particularly limited and can be appropriately selected according to the materials and combinations of the first component and the second component. The atmosphere during bonding is preferably an inert atmosphere. The bonding pressure in an inert atmosphere can be, for example, 1 MPa or more and 40 MPa or less. The bonding temperature in an inert atmosphere can be, for example, 150°C or more and 400°C or less. In particular, in an embodiment of the present invention, good bonding can be achieved even when the bonding temperature (atmosphere temperature during bonding) is 250°C or less. The bonding time in an inert atmosphere can be, for example, 1 minute or more and 60 minutes or less.

[0102] Examples

[0103] [Manufacture of bonding material]

[0104] Copper fine particles obtained by the manufacturing method described in Japanese Patent No. 4304221 were prepared as raw materials. The content of copper element in the obtained copper fine particles was 98.8% by mass. For the average particle diameter of the obtained copper fine particles, the result obtained by the above method was 110 nm. The particle size distribution of the obtained copper fine particles was D10: 40 nm, D50: 110 nm, and D90: 300 nm. In addition, the ratio of the oxygen mass concentration to the specific surface area of the obtained copper fine particles was 0.25% by mass·g / m 2 , and the ratio of the carbon mass concentration to the specific surface area was 0.03% by mass·g / m 2 .

[0105] In addition, as the copper coarse particles, "MA-C03KP" manufactured by Mitsui Mining & Smelting Co., Ltd. (average particle size: 3.8 μm, tapped density 5.26 g / cm 3 ) was prepared. The content of copper element in the copper coarse particles was 97.5 mass%. The particle size distribution of the copper coarse particles was D10: 1.9 μm, D50: 3.8 μm, and D90: 8.2 μm. The particle size distribution of the copper fine particles did not overlap with the particle size distribution of the copper coarse particles.

[0106] The copper fine particles and the copper coarse particles were mixed so that the content of the copper fine particles relative to the total content of the copper fine particles and the copper coarse particles reached the values shown in Table 1, and a reducing agent of the type shown in Table 1 was added so that the content of the reducing agent relative to the total content of the mixed copper fine particles and copper coarse particles (at the time of mixing) reached the values shown in Table 1. 2-propanol was added as a diluting solvent, and stirring was carried out using a planetary mixer to obtain a mixed slurry. Then, the obtained mixed slurry was dried for 2 hours at 70 °C to remove 2-propanol, and a mixture of copper fine particles, copper coarse particles (partial examples), and a reducing agent was obtained.

[0107] Then, the mixture was placed into the central hole of a cylindrical jig made of tungsten carbide with a length of 50 mm and a 7 mm square hole in the center. Next, prisms made of tungsten carbide with a side length of 7 mm were vertically inserted into the central hole from both ends of the central hole of the jig, and pressure was applied and formed into a sheet. The pressure forming was carried out at normal temperature in the atmosphere under the condition of a pressure of 74 MPa for 5 minutes. Thus, in each example shown in Table 1, a sheet-like bonding material with a size of 7 mm square and a thickness of 250 μm was obtained. In the sheet-like bonding material, the content of the reducing agent relative to the total content of the copper fine particles and the copper coarse particles was the same as the content of the reducing agent at the time of mixing shown in Table 1.

[0108] [Manufacture of bonded body]

[0109] As the first component, gold-plated SiC (5 mm square, thickness 350 μm) was prepared, and as the second component, oxygen-free copper plate C1020 (20 mm square, thickness 2 mm) was prepared. Using the sheet-like bonding material obtained in each example shown in Table 1, the first component and the second component were pressure-bonded in a 100 vol% nitrogen atmosphere (inert atmosphere) with the bonding temperature (atmosphere temperature) set to the temperature shown in Table 1 at a bonding pressure of 10 MPa and a bonding time of 5 minutes to manufacture a bonded body in each example shown in Table 1.

[0110] [Evaluation of shear strength]

[0111] The shear strength of the bonded body was measured using a bond tester (Bondtester) (manufactured by Dazzy Corporation, Japan, 4000Plus). The tool height was 100 μm and the tool speed was 200 μm / s. The results are shown in Table 1.

[0112] [Sinterability Evaluation of the Press-Fit Surface]

[0113] After measuring the shear strength, the cross-section of the joined sample that was damaged was supplied to SEM, and the sinterability of the copper particles at the center and edge of the press-fit surface was observed. When necking between the copper particles was observed, it was rated as "good"; when necking between the copper particles was partially observed, it was rated as "acceptable"; when no necking between the copper particles was observed, it was rated as "unacceptable". The results are shown in Table 1.

[0114] [Shape Evaluation of the Joining Material]

[0115] The appearance of the joined body was confirmed. If the shape of the joining material was not damaged, it was rated as "good"; if the shape of the joining material was not damaged but seepage of the reducing agent was observed, it was rated as "acceptable"; if the shape of the joining material was damaged and the joining material was observed to flow out from the joining surface, it was rated as "unacceptable". The results are shown in Table 1.

[0116] Table 1

[0117]

[0118]

[0119] [Effect of the Type of Reducing Agent]

[0120] In Invention Example No. 1 using triethanolamine as the reducing agent, the sinterability was good. On the other hand, in Comparative Example No. 12 using ethylene glycol as the reducing agent and Comparative Example No. 14 using diethanolamine, no necking was observed at the edge.

[0121] [Effect of the Content of Triethanolamine]

[0122] In Invention Examples No. 1 to No. 9 where the content of triethanolamine was 1.5% by mass or more and 10% by mass or less, the sinterability was good. On the other hand, in Comparative Example No. 10 where the content of triethanolamine was 1.0% by mass, joining was not possible. In addition, in Comparative Example No. 11 where the content of triethanolamine was 10.7% by mass, it was not possible to form into a sheet.

[0123] Based on the results of Invention Examples No. 4 and No. 5 and the results of Invention Examples No. 6 to No. 9, it was confirmed that the higher the content of triethanolamine, the higher the bonding strength. However, in Invention Examples No. 5 and No. 9 where the content of triethanolamine was 9.1% by mass, outflow of the bonding material was observed. Therefore, it is known that the content of triethanolamine is preferably 7.5% by mass or less. Furthermore, although outflow of the bonding material was observed in Invention Examples No. 5 and No. 9, the bonding strength was sufficient and there was no unevenness in the sintering state between the central portion and the edge portion, so it can be used as a bonding material.

[0124] [Effect of copper particle content]

[0125] In Invention Examples No. 1 to No. 9 where the content of copper particles relative to the total content of copper particles and copper coarse particles was 50% by mass or more, the sinterability was good. On the other hand, in Comparative Example No. 16 where the copper particles were less, no necking was observed at the edge portion.

[0126] [Effect of bonding temperature]

[0127] Compared with Invention Example No. 3 having the same composition as the bonding material, Invention Example No. 6 had relatively poor sinterability at the pressed edge portion but obtained relatively good results. From this result, it was confirmed that if triethanolamine is used as a reducing agent, bonding can be performed even at a bonding temperature of 200°C.

[0128] Industrial applicability

[0129] The sheet-like bonding material, the method for manufacturing the sheet-like bonding material, the bonded body, and the method for manufacturing the bonded body of the present invention can be industrially used for the purpose of bonding electronic components. Specifically, examples can include bonding applications of components such as substrates and elements in a high-temperature environment where it is difficult to use bonding materials such as solder, such as inside an electronic device called a power device.

Claims

1. A sheet-like bonding material, characterized in that: it contains copper particles and a reducing agent for reducing the copper particles, the copper particles contain copper fine particles with an average particle size of 300 nm or less and optionally contained copper coarse particles with an average particle size of 3 μm or more and 11 μm or less, relative to the total content of the copper fine particles and the copper coarse particles, the content of the copper fine particles is 50% by mass or more and 100% by mass or less, the reducing agent consists of triethanolamine, and relative to the total content of the copper fine particles and the copper coarse particles, the content of the triethanolamine is 1.5% by mass or more and 10.0% by mass or less.

2. The sheet-like bonding material according to claim 1, wherein, The ratio of the oxygen mass concentration of the copper particles to the specific surface area is 0.1 mass%·g / m 2 or more and 1.2 mass%·g / m 2 or less.

3. The sheet-like bonding material according to claim 1, wherein, The ratio of the carbon mass concentration of the copper fine particles to the specific surface area is 0.008 mass%·g / m 2 or more and 0.3 mass%·g / m 2 or less.

4. A method for manufacturing a sheet-like bonding material, characterized in that it has: a mixing step of mixing copper particles and a reducing agent for reducing the copper particles to obtain a mixture; and a compression molding step of compression molding the mixture to obtain a sheet-like bonding material, wherein the copper particles contain copper fine particles with an average particle size of 300 nm or less and optionally contained copper coarse particles with an average particle size of 3 μm or more and 11 μm or less, in the mixture, relative to the total content of the copper fine particles and the copper coarse particles, the content of the copper fine particles is 50% by mass or more and 100% by mass or less, the reducing agent consists of triethanolamine, and in the mixture, relative to the total content of the copper fine particles and the copper coarse particles, the content of the triethanolamine is 1.5% by mass or more and 10.0% by mass or less.

5. The method for manufacturing a sheet-like bonding material according to claim 4, wherein, the mixing step includes: a step of mixing the copper particles, the reducing agent and an organic solvent to obtain a slurry; and a step of drying the slurry to obtain the mixture.

6. An assembly, wherein, it has a first component, a second component and the bonding material according to any one of claims 1 to 3, and the bonding material is located between the first component and the second component.

7. A method for manufacturing an assembly, wherein, it has the following steps: pressurizing in a state where the bonding material according to any one of claims 1 to 3 is disposed between a first component and a second component to obtain an assembly in which the first component and the second component are bonded by the bonding material.

8. The method for manufacturing an assembly according to claim 7, wherein, the bonding temperature is set to 250 °C or less. ​

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