Sheet-shaped joining material, method for producing joined body, and joined body

Abstract

Provided is a sheet-like bonding material which contains a medium and fine copper oxide-coated copper particles provided with copper particles as a core and a shell containing one or more fine copper oxides among Cu64O and Cu8O, the fine copper oxide particles being fine copper oxide particles having an average particle diameter of 1-20 nm (inclusive), and the fine copper oxide particles containing copper particles as a core and one or more fine copper oxides among Cu64O and Cu8O being fine copper oxide particles having an average particle diameter of 1-20 nm (inclusive). The content of the micro copper oxide-coated copper particles is greater than 85 mass%.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a sheet-shaped joining material, a manufacturing method of a joined body, and a joined body. BACKGROUND

[0002] Conventionally, a solder has been used in joining between members such as joining of a substrate and a component of a semiconductor device, joining between circuits. In joining of a power semiconductor, LSI, and the like that operate at a high temperature of 150°C or higher in a semiconductor device, a high-melting-point lead solder has been used as a joining material. In addition, as a joining material that does not contain lead, a technique in which silver nanoparticles are subjected to low-temperature sintering to form a sintered silver layer, and the like have been proposed in the past.

[0003] Further, in Patent Literature 1, a technique of obtaining a joined body using a thin-plate-shaped copper particle as a joining material is exhibited. Specifically, a joined body having a sintered metal layer that has sufficient connection reliability in a temperature cycle test including a high-temperature condition, having a first member, a second member, and a sintered metal layer that joins the first member and the second member, the sintered metal layer including a structure from a thin-plate-shaped copper particle that is oriented substantially in parallel with an interface of the first member or the second member and the sintered metal layer, and an orientation order S calculated according to a given formula (1) of the structure from the thin-plate-shaped copper particle being 0.88 or more and 1.00 or less is exhibited. In addition, in Patent Literature 2, as a joining sheet in which reduction in sinterability due to oxidation of copper particles is less likely to occur, a dense and void-poor joining layer can be formed, and an electronic component or the like can be joined with high strength, a joining sheet including a copper particle and a solvent having a boiling point of 150°C or higher, a content ratio of the copper particle and the solvent being 99:1 to 90:10 in terms of mass ratio, a BET diameter of the copper particle being in a range of 40 nm or more and 750 nm or less, and the solvent having an OH group in a structure is exhibited.

[0004] Note that, as a copper particle, various forms of copper particles, copper oxide particles are exhibited in Patent Literatures 3 to 7.

[0005] Prior Art Documents

[0006] Patent Literature

[0007] Patent Literature 1: Japanese Patent Application Publication No. 2021-63300

[0008] Patent Literature 2: Japanese Patent Application Publication No. 2022-113002

[0009] Patent Literature 3: International Publication No. 2019 / 106739

[0010] Patent Literature 4: International Publication No. 2022 / 045252

[0011] Patent Literature 5: Japanese Patent Application Laid-Open No. 2020-29392

[0012] Patent Literature 6: Japanese Patent Application Laid-Open No. 2020-100896

[0013] Patent Literature 7: Japanese Patent Application Laid-Open No. 2019-203172 SUMMARY

[0014] PROBLEMS TO BE SOLVED BY THE INVENTION

[0015] In recent years, for example, in a semiconductor device including a SiC power semiconductor or the like, it is required that a bonding portion between members constituting the semiconductor device exhibits sufficiently high adhesive strength (also referred to as "bonding strength"). On the other hand, in the bonding methods and the bonded bodies proposed in the past including Patent Literatures 1 and 2, sufficiently high adhesive strength cannot be achieved. In addition, Patent Literatures 3 to 7 have not studied bonding. The present disclosure is completed in view of the above, and one of the objects thereof is to provide a sheet-shaped bonding material useful for manufacturing a bonded body exhibiting high adhesive strength, a manufacturing method of a bonded body using the sheet-shaped bonding material, and a bonded body exhibiting high adhesive strength.

[0016] MEANS FOR SOLVING THE PROBLEMS

[0017] Mode 1 of the present invention is a sheet-shaped bonding material including micro-copper oxide-coated copper particles and a medium,

[0018] The micro-copper oxide-coated copper particles have copper particles as a core and a shell including Cu 64 O and one or more kinds of micro-copper oxides selected from CuO and Cu8O, 64 The one or more kinds of micro-copper oxides selected from CuO and Cu8O are micro-copper oxide particles having an average particle diameter of 1 nm or more and 20 nm or less,

[0019] The content of the micro-copper oxide-coated copper particles is more than 85% by mass.

[0020] Mode 2 of the present invention is the sheet-shaped bonding material described in Formula 1, in which

[0021] The copper particles as a core have an average particle diameter of 20 nm or more and less than 2 μm.

[0022] Mode 3 of the present invention is the sheet-shaped bonding material described in Mode 1 or 2, which has a thickness of 1 μm or more and 1 mm or less.

[0023] Mode 4 of the present invention is a manufacturing method of a bonded body, the manufacturing method including:

[0024] A laminate is obtained by placing the sheet-like bonding material described in any of methods 1 to 3 between the first member and the second member; and

[0025] The laminate is heated at 100 to 500°C, and the first component and the second component are joined together by sintering of the sheet bonding material.

[0026] Embodiment 5 of the present invention is a method for manufacturing the joint as described in Embodiment 4, wherein,

[0027] The above-mentioned laminated body was heated under a pressure of 40 kPa or higher.

[0028] Embodiment 6 of the present invention is a method for manufacturing an assembly according to Embodiment 4 or 5, wherein,

[0029] At least one of the first component and the second component is a semiconductor element, and the junction is a semiconductor device.

[0030] Embodiment 7 of the present invention is a joint comprising a first member, a second member, and a sintered product of a sheet-like bonding material described in any one of Embodiments 1 to 3 for joining the first member and the second member.

[0031] Embodiment 8 of the present invention is a joint body according to Embodiment 7, wherein,

[0032] At least one of the first component and the second component is a semiconductor element, and the junction is a semiconductor device.

[0033] Invention Effects

[0034] According to this disclosure, a sheet bonding material useful for manufacturing a joint exhibiting high adhesive strength, a method for manufacturing a joint using the sheet bonding material, and a joint exhibiting high adhesive strength can be provided. Attached Figure Description

[0035] Figure 1 It is a graph illustrating the relationship between the particle size (nuclear particle size) of a nuclear particle and the number of granulation points per piece.

[0036] Figure 2 This is a schematic cross-sectional view illustrating the sintering state of particles in the past.

[0037] Figure 3 This is a schematic cross-sectional view illustrating the sintering state of the nanoparticles in this embodiment.

[0038] Figure 4 It is a graph illustrating the relationship between the content of copper particles and the volume of the medium.

[0039] Figure 5AThis diagram illustrates the reason for setting the load during sintering to 40 kPa or higher, and it shows the state before sintering.

[0040] Figure 5B This diagram illustrates the reason for setting the load during sintering to 40 kPa or higher, and it shows the case without pressure.

[0041] Figure 5C This diagram illustrates the reason for setting the load during sintering to 40 kPa or higher, and it shows the situation where pressure is applied.

[0042] Figure 6 These are TEM images of the particles obtained in the examples.

[0043] Figure 7 These are STEM images of the particles obtained in the embodiments. The STEM image on the right is a magnified image of the lattice plane spacings given in the STEM image on the left.

[0044] Figure 8 The results are TG-DTA measurements from the example.

[0045] Figure 9 This is a diagram illustrating the steps involved in preparing a sample for evaluation of the bonding firing process in an embodiment.

[0046] Figure 10A This is a schematic diagram of the copper test piece used in the preparation of the sample for evaluation of the bonding firing process in the embodiment.

[0047] Figure 10B This is a schematic diagram of the hot press used in the bonding firing evaluation test in the illustrative embodiment.

[0048] Figure 10C This is a schematic cross-sectional view illustrating the method of the bonding firing evaluation test in the embodiments.

[0049] Figure 11 This is a graph showing the results of the bonding firing evaluation test (15 MPa pressure, 15 minutes bonding time) in the embodiment. Detailed Implementation

[0050] Copper oxides: in CuO, Cu2O, Cu4O3, Cu8O, Cu 64 Of the five types of O, Cu 64 O and Cu8O have a lower proportion of oxygen atoms and lower stability compared to other copper oxides, thus they can be reduced to metallic copper using low energy. The interatomic distances in these copper oxides are longer than in metallic copper, and the reduction reaction of metallic copper, accompanied by changes in crystal structure, facilitates the diffusion of copper atoms, significantly promoting particle sintering. The inventors have long focused on the aforementioned Cu... 64O and Cu8O (collectively referred to as "micro-copper oxide") are useful for sintering at low temperatures, and micro-copper oxide-containing particles having at least one of these micro-copper oxides on their surface were studied. Furthermore, micro-copper oxide-coated copper particles with a copper core and a shell containing micro-copper oxide were discovered.

[0051] If the aforementioned copper particles containing micro-copper oxide are used in a paste, low-temperature sintering becomes easier. Therefore, this paste is considered useful as a conductive paste for printed electronics or as a bonding paste. Consequently, its application as a core-sheet bonding paste was first evaluated. The results showed that the higher the concentration of micro-copper oxide particles in the paste, the more the concentration of the dispersion medium is suppressed, thus suppressing the formation of voids and cracks associated with the volatilization of the dispersion medium, resulting in higher bonding strength. However, if the concentration of micro-copper oxide particles in the paste exceeds 85% by mass, the paste becomes clay-like or powdery, making coating very difficult. Furthermore, even when using clay-like or powdery pastes for coating, a uniform coating film cannot be obtained, leading to increased workload.

[0052] In view of these problems, the inventors have discovered that if a sheet bonding material is manufactured, it comprises copper particles coated with micro-copper oxide and a medium, wherein the copper particles coated with micro-copper oxide have copper particles as a core and contain Cu. 64 The shell of one or more micro-copper oxides, namely O and Cu8O, and the above-mentioned Cu 64 If one or more of the copper oxides, O and Cu8O, are copper oxide particles with an average particle size of 1 nm or more and 20 nm or less, and the content of the copper oxide-coated copper particles is greater than 85% by mass, then, for example, the bonding process can be simplified, and a bond with high bonding strength can be obtained by sintering at a low temperature. Hereinafter, the material for sheet bonding, the manufacturing method of the bond, and the bond will be described in sequence.

[0053] <Materials for sheet bonding>

[0054] The micro-coated copper particles and the medium contained in the sheet bonding material are described in turn.

[0055] [Micro-coated copper particles]

[0056] The sheet bonding material of this embodiment contains micro-copper oxide-coated copper particles, which are core-shell micro-copper oxide particles (micro-copper oxide-coated copper particles), and have copper particles as the core and Cu-containing... 64 One or more of the following micro-copper oxides (containing Cu₂O and Cu₈O) 64One or more of the micro-copper oxides, namely O and Cu8O, are micro-copper oxide particles with an average particle size of 1 nm or more and 20 nm or less. It should be noted that when simply referred to as "copper" as in "copper particles," it refers to metallic copper to distinguish it from copper oxide. Because the sheet bonding material contains these core-shell-shaped micro-copper oxide particles and a medium that also acts as a reducing agent, the Cu forming the shell is reduced to metallic copper upon heating. 64 O and Cu8O nanoparticles tightly connect adjacent copper microparticle cores, significantly promoting sintering between the core particles. The resulting sintered product has a structure with highly crystalline copper microparticle cores tightly connected, and high mechanical strength can be expected. Additionally, for example, conventional Cu... 64 Compositions of at least one type of micro-copper oxide particles, copper particles, and copper clusters, including O particles and Cu8O particles, are difficult to disperse uniformly. However, in the aforementioned micro-copper oxide-coated copper particles with a core-shell structure, the dispersion problem is solved. During sintering, as described above, the Cu on the surface of the copper particles, which act as the core, can be promoted. 64 Sintering between micro-copper oxide particles such as O. It should be noted that the copper particles and copper microparticles in Patent Documents 2, 5 to 7 are not in the core-shell shape as described above, but are compositions (mixed particles), etc., which do not help solve the above problems.

[0057] As for the size of the copper particles as the core of the micro-oxidized copper-coated copper particles, it is preferable that the average particle diameter be 20 nm or more, and more preferably be greater than 20 nm and less than 2 μm, from the following viewpoints. The reason why the average particle diameter of the core copper particles is set to 20 nm or more is explained as follows. The smaller the size of the fine particles and nano-particles, the higher the coagulation force, and the more difficult it is to disperse them easily in a medium. Therefore, from the viewpoint of uniform and easy dispersion and stabilization of the dispersed state, the average particle diameter of the core copper particles is set to 20 nm or more. Further, in order to maintain the strength of the obtained sintered body, from the viewpoint of the material for bonding, it is required that the core copper particles be highly crystalline. In order to obtain particles having high crystallinity, a synthesis means reaching the vicinity of the melting point of the metal, such as a high-temperature thermal decomposition method, an atomization method, an oxygen combustion method, and the like, is generally used. The crystallite size of the sub-micron-sized copper fine particles obtained by these methods is about 50 nm. On the other hand, in the liquid phase reduction method as a low-temperature synthesis method, by optimizing the synthesis method, fine particles having a crystallite size of 17 to 50 nm can be obtained with respect to the sub-micron-sized copper fine particles. The present inventors and others have confirmed by experiments that a copper particle paste having a crystallite size of about 20 nm can obtain a practical adhesive strength. Therefore, the crystallite size of the core copper particles is at least 20 nm, and in order to obtain a sintered body having higher strength, it is preferable that the crystallite size be 40 nm or more. Thus, the average particle diameter of the core copper particles is set to 20 nm or more (because the particle diameter cannot be smaller than the crystallite size). Note that, from the viewpoint of providing the given size of the micro-oxidized copper particles on the surface of the core copper particles, the average particle diameter of the core copper particles is also set to 20 nm or more. As for the average particle diameter of the core copper particles, it is preferable that the average particle diameter be 40 nm or more from the viewpoint of the crystallite size as described above.

[0058] The reason why the average particle diameter of the core copper particles is set to less than 2 μm is explained as follows. The sintered body becomes a structure in which the core particles are neck-bonded to each other by the sintering of the shell nano-particles. The larger the particle diameter of the core particles, the fewer the number of core particles per unit volume, and in conjunction therewith, the fewer the number of sintering joints bonding the core particles to each other. Figure 1 is a graph in which the relationship between the particle diameter of the core particles (core particle diameter) and the number of sintering joints (number of joints per 1 sheet) is arranged for the sheet-shaped bonding material A of the embodiment described later. According to the graph, the number of sintering joints is the largest when the average particle diameter of the core copper particles is 40 nm or more and less than 2 μm. Therefore, from the viewpoint of the number of sintering joints, the average particle diameter of the core copper particles is preferably 40 nm or more and less than 2 μm. Figure 1For example, if we compare the number of junctions with a core particle size of 100 nm and a core particle size of 2 μm, the number of junctions with a core particle size of 100 nm is 8000 times that with a core particle size of 2 μm, which is significantly different. When applying equal loads to these sintered bodies, the load on each sintering junction of particles with a core particle size of 2 μm is 8000 times that of particles with a core particle size of 100 nm, resulting in a heavy load burden and making it difficult to ensure strength. Experimental observations also confirm that the adhesive strength when using core particles with a core particle size of 2 μm is less than the practical strength of 20 MPa. Therefore, the average particle size of the copper core particles is set to be less than 2 μm. In addition, the surface roughness of copper foil for semiconductors is about 1 to 3 μm. From the viewpoint of expecting a good adhesion effect to copper foil for semiconductors, it is also preferable to set the average particle size of the copper core particles to be less than 2 μm. The average particle size of the copper core particles is preferably 300 nm or less.

[0059] Cu forming a shell of micro-copper oxide coating on copper particles 64 The micro-copper oxide, consisting of one or more of O and Cu8O, is in the form of multiple particles, with an average particle size of 1 nm or more, preferably greater than 1 nm and less than 20 nm. The shell of this embodiment, as described above, is composed of nanoparticles of 1 nm or more and 20 nm or less. Regarding the advantages of this over conventional technologies, the following will use… Figure 2 and Figure 3 To illustrate. For example, in the case of conventional particles, such as those in Patent Documents 3 and 4, where an oxide film 13 is formed on the surface of the copper core particle 11, the sintering of multiple particles is as follows: Figure 2 As shown in the upper part, it occurs in a point contact manner; however, in the nanoparticle shell of this embodiment, as... Figure 3 As shown in the upper part, the sintering of nanoparticles 17, which are spread over a large area, occurs over a large area around the copper core particles 11. As a result, in conventional particles, such as... Figure 2 As shown in the lower part, a sintered body 15A with small bonding points obtained with point contact sintering is obtained. However, in the nanoparticles of this embodiment, a sintered body 15B with a large necking range and strong structure is obtained. Based on this result, the micro-copper oxide coated copper particles of this embodiment, whose shell is composed of multiple micro-copper oxide particles with an average particle size of 1 nm or more and 20 nm or less, are suitable for bonding materials.

[0060] The thickness of the shell (the thickness of the stacked particles) can be, for example, 1–20 nm. Containing Cu 64 The shell of one or more micro-copper oxides, such as O and Cu8O, is sintered during the reduction to copper. However, since its crystallinity is not as high as that of the copper particles in the core, the mechanical strength may decrease if the shell thickness is too thick. From these points of view, the shell thickness is preferably set to 20 nm or less as described above.

[0061] The microcupric oxide forming the shell of the microcupric oxide-coated copper particle can be mixed with microcupric oxide particles having different sizes, for example, CuO having an average particle diameter of 1 nm to 20 nm 64 one or more of O and Cu8O and Cu having an average particle diameter of 0.1 μm to 1 μm 64 O.

[0062] In the shell, one or more of O and Cu8O and Cu having an average particle diameter of 0.1 μm to 1 μm 64 In addition to one or more of O and Cu8O, it is also permissible to contain, for example, cupric oxide such as CuO and Cu20 used as a raw material in an amount that does not hinder sinterability and electrical conductivity. It is preferable not to contain cupric oxide such as CuO and Cu20 used as a raw material. The above shell is preferably formed of microcupric oxide particles including Cu 64 O and Cu8O having an average particle diameter of 1 nm to 20 nm, and more preferably by microcupric oxide particles including Cu 64 O or Cu8O having an average particle diameter of 1 nm to 20 nm. 64 O and Cu8O having an average particle diameter of 1 nm to 20 nm.

[0063] The microcupric oxide-coated copper particle can be manufactured by the following method, but is not limited thereto and can be manufactured by a method different from the following manufacturing method.

[0064] Method for manufacturing microcupric oxide-coated copper particle

[0065] The microcupric oxide-coated copper particle of the present embodiment having a copper particle as a core and a shell including one or more of O and Cu8O (the Cu 64 O and Cu8O having an average particle diameter of 1 nm to 20 nm) includes: 64 O and Cu8O having an average particle diameter of 1 nm to 20 nm) includes:

[0066] providing a cupric oxide-coated copper raw material particle having a copper raw material particle as a core and a shell including one or more of cupric oxide such as CuO and Cu20; and

[0067] The above cupric oxide-coated copper raw material particle is mixed with a solution including an amine compound and a complexing agent, and then a reducing agent is added and reacted in an oxygen-containing atmosphere. The conditions of the above manufacturing method are described in detail below.

[0068] Process for preparing cupric oxide-coated copper raw material particle

[0069] First, a copper oxide-coated copper raw material particle in which a copper oxide film containing one or more of CuO and Cu2O is coated on a copper raw material particle is prepared. The particle is preferably a core-shell type copper oxide-coated copper raw material particle in which a copper raw material particle is a core and is coated with a copper oxide containing one or more of CuO and Cu2O, more preferably a copper oxide containing Cu2O. If the copper oxide-coated copper raw material particle is of this configuration, reduction from copper oxide to copper and oxidation from copper to a fine oxide occur on the surface of the core copper particle in the reaction step described later, so that the desired core-shell type particle is easily obtained, and thus is suitable.

[0070] As the copper oxide-coated copper raw material particle, a commercially available product can be used, a particle in which a surface oxidation film is formed by natural oxidation of a copper particle can be used, and a particle in which a surface oxidation film is formed by performing oxidation treatment on the surface of a copper particle can be used. In addition, although the form is different from that of the copper oxide-coated copper raw material particle, for a copper raw material particle on the surface of which copper oxide is not formed at all or substantially, a mixture obtained by supplying, for example, by adding, coating, or the like, a copper oxide containing one or more of CuO and Cu2O (for example, as a copper oxide in the form of a powder) to a dispersion liquid containing the above-described copper raw material particle can be used as a raw material particle. Although this form is not necessarily a copper oxide covering the surface of a core copper particle, and thus cannot be said to be a suitable raw material, the same particle can be obtained more easily. Note that a surface oxidation film formed by natural oxidation is formed only by the presence of a copper particle in the atmosphere. Thus, a commercially available copper particle is also considered to be naturally oxidized by being present in the atmosphere, and among particles in which a surface oxidation film is formed by natural oxidation of the above-described copper particle, a commercially available copper particle is also included.

[0071] Regarding the copper raw material particle as a core, based on the same reasons as the average particle diameter of the aforementioned core copper particle, the average particle diameter is preferably, for example, 20 nm or more and less than 2 μm. In addition, the film thickness of the copper oxide film containing one or more of CuO and Cu2O on the surface of the copper raw material particle as a core can be 20 nm or less. Note that in this specification, the "particle diameter" refers to the primary particle diameter and refers to the equivalent circle diameter, and the "average particle diameter" refers to the median diameter of 150 or more particles randomly selected from a SEM image or a TEM image.

[0072] A copper oxide film containing one or more of CuO and Cu2O (preferably copper oxide containing Cu2O) present on the surface of the aforementioned copper oxide-coated copper raw material particles is sufficient even if it is an oxide film of a natural oxidation degree that cannot be detected by X-ray diffraction. The copper oxide film on the aforementioned copper oxide-coated copper raw material particles can be more than a natural oxide film. For example, the proportion of one or more of CuO and Cu2O in the aforementioned copper oxide-coated copper raw material particles can be set to 1% by mass or more. The intention is to form a thick core-shell type micro copper oxide-coated copper particles containing CuO. 64 In the case of a shell containing one or more copper oxides, such as O and Cu8O, the copper oxide-coated copper raw material particles can be actively oxidized. In this case, if the proportion of surface copper oxide in the aforementioned copper oxide-coated copper raw material particles is excessive, then the copper content may exceed the limits of Cu. 64 In addition to forming a shell, particles of one or more of the copper oxides in O and Cu8O tend to exist as individual aggregates. Furthermore, Cu... 64 Compared to copper particles with highly crystalline cores, the shell of one or more copper oxides, namely O and Cu8O, exhibits lower crystallinity during low-temperature sintering. Therefore, if the shell thickness is large, the mechanical strength may decrease. From these perspectives, the proportion of copper oxides containing one or more of CuO and Cu2O in the aforementioned copper oxide-coated copper raw material particles is preferably 10% by mass or less.

[0073] [Reaction process]

[0074] The copper oxide-coated copper raw material particles described above are mixed with a solution containing an amine compound and a complexing agent, and then a reducing agent is added to initiate the reaction. The complexing agents and other components necessary for the reaction, as mentioned above, are explained below.

[0075] (Complexing agent)

[0076] In this embodiment, the copper oxide contained in the copper oxide-coated copper raw material particles reacts with a complexing agent to form a copper complex ion. By ionizing the copper in the copper oxide-coated copper raw material particles in this way, the reduction rate of the reducing agent can be significantly faster than the reduction of solid copper oxide. Carboxylic acids can be used as the complexing agent. Examples of carboxylic acids include formic acid, saturated fatty acids, unsaturated fatty acids, hydroxy acids, aromatic carboxylic acids, and terpene carboxylic acids. These can be monocarboxylic acids or dicarboxylic acids. Furthermore, they can be used alone or in combination of two or more. Aliphatic monocarboxylic acids can be either linear or branched, and can also be either saturated or unsaturated aliphatic monocarboxylic acids. Examples of linear saturated aliphatic monocarboxylic acids include acetic acid (2 carbons), propionic acid (3 carbons), butyric acid (4 carbons), valeric acid (5 carbons), and hexanoic acid (6 carbons).

[0077] The aliphatic dicarboxylic acid can be either linear or branched, and can also be either a saturated aliphatic dicarboxylic acid or an unsaturated aliphatic dicarboxylic acid. One or more than two kinds of aliphatic dicarboxylic acids can be used alone or in combination. As the aliphatic dicarboxylic acid, for example, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,0-azelaic acid, 1,10-sebacic acid, brassylic acid (tridecyldioic acid), 1,12-dodecanedioic acid, 1,13-tridecanedioic acid, tapyric acid (hexadecanedioic acid), 1,15-pentadecanedioic acid, 1,16-hexadecanedioic acid, and the like can be given. As the aromatic carboxylic acid, for example, benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, hemimellitic acid, trimellitic acid, trimesic acid, and the like can be given. As the terpene carboxylic acid, a terpene carboxylic acid contained in rosin and the like can be used. For example, abietic acid, neoabietic acid, palustric acid, pimaric acid, isopimaric acid, dehydroabietic acid, and the like can be given.

[0078] Among them, acetic acid, which is easy to handle and easy to dispose after the reaction, is preferably used as the complexing agent.

[0079] The amount of the complexing agent used in the reaction is not particularly limited, however, in order to promote the formation of Cu 64 O and Cu8O, from the viewpoint of promoting the formation of copper complex ions, the molar ratio of the complexing agent to the copper contained in the copper raw material particle coated with copper oxide as a starting material is preferably 0.05 times or more and 15 times or less, and can also be 2 times or more and 15 times or less.

[0080] (Amine-based compound)

[0081] A compound having an amino group (hereinafter referred to as "amine-based compound") is added as a protective agent. The amine-based compound also contributes to the formation of copper complex ions. The amine-based compound is not particularly limited, and for example, alkanolamine, diamine, and aminocarboxylic acid, and the like are preferably used. Among them, alkanolamine is more preferably used. As the alkanolamine, for example, 2-amino-1-butanol, 1-amino-2-propanol, 2-amino-2-ethyl-1,3-propanediol, 2-amino-2-hydroxymethyl-1,3-propanediol, 1,3-diamino-2-propanol, 1-amino-2-butanol, 2-aminoethanol, and the like can be given.

[0082] The amount of the amine-based compound used in the reaction is not particularly limited, however, from the viewpoint of promoting the formation of Cu 64 O and Cu8O, the molar ratio of the amine-based compound to the copper contained in the copper raw material particle coated with copper oxide is preferably 0.1 times or more, and can also be 5 times or more. The above molar ratio can be, for example, 20 times or less.

[0083] (solvent)

[0084] The solvent is not particularly limited, and for example, a polyhydric alcohol such as ethylene glycol, a lower alcohol such as methanol, ethanol, 2-propanol, a ketone such as acetone, water, or the like can be used.

[0085] (reducing agent)

[0086] The reducing agent is not particularly limited, and a hydrazine-based reducing agent such as hydrazine, hydrazine hydrochloride, hydrazine sulfate, hydrazine hydrate, citric acid, ascorbic acid, sodium borohydride, a borohydride salt, or the like can be used. The timing of addition of the reducing agent is set to be after the raw material containing the copper oxide-coated copper raw material particle, the complexing agent, the amine-based compound, and the solvent are put in and mixed. After the reducing agent is added, stirring is performed until the formation of the desired micro-oxidized copper is confirmed, and preferably, the stirring is performed until the reducing agent disappears so as to allow sufficient reaction.

[0087] (cooling during the reaction)

[0088] In the method for producing a micro-oxidized copper-coated copper particle, for example, in the case where hydrazine is used as the reducing agent, heat generation due to the addition of the reducing agent, such as a decomposition reaction of hydrazine, sometimes occurs, and the temperature of the reaction solution rises. From the viewpoint of suppressing the temperature rise of the reaction solution, suppressing the formation of CuO and Cu8O that have already been formed, and the like, it is preferable to set a temperature control mechanism such as cooling of the reaction solution, so that the reaction is performed at 50°C or lower. For example, it is preferable to add the reducing agent in a state where the reaction vessel is subjected to water bath. 64 From the viewpoint that CuO and Cu8O are reduced to metallic copper, it is preferable to provide a temperature control mechanism such as cooling of the reaction solution, so that the reaction is performed at 50°C or lower. For example, it is preferable to add the reducing agent in a state where the reaction vessel is subjected to water bath.

[0089] (atmosphere during the reaction)

[0090] The atmosphere during the reaction is, for example, limited to an oxygen-containing atmosphere in the air, and it is necessary to be always exposed to this oxygen-containing atmosphere during the reaction. In the case where a non-active gas atmosphere such as nitrogen gas, argon gas, or the like is set, or even in the case where the reaction vessel is closed in the air, the oxide formation reaction of CuO or Cu8O is not advanced, and instead, copper particles are formed, and thus this is not preferable. 64 From the viewpoint that CuO and Cu8O are reduced to metallic copper, it is preferable to provide a temperature control mechanism such as cooling of the reaction solution, so that the reaction is performed at 50°C or lower. For example, it is preferable to add the reducing agent in a state where the reaction vessel is subjected to water bath.

[0091] (other processes)

[0092] The method for producing a micro-oxidized copper-coated copper particle can further include a process other than the above. For example, a purification process, a drying process, or the like can be included. In the purification process, purification is preferably performed using a washing solvent. The washing solvent is not particularly limited, and for example, an organic solvent such as N,N-dimethylacetamide, toluene, hexane, or the like can be used.

[0093] The proportion of micro-coated copper particles in the sheet bonding material is greater than 85% by mass. The rationale for determining this proportion is as follows: In the case of a sheet bonding material composed, for example, of copper particles and a dielectric, the relationship between the volume (volume%) of the dielectric and the content (mass%) of the copper particles is as follows: Figure 4 As shown. The medium described above is envisioned to be a liquid or a solid such as a resin, with a specific gravity ranging from approximately 0.8 to 2. Since the volume of the medium changes with its specific gravity, therefore... Figure 4 As a representative example, the relationship between the copper particle content (mass%) and the volume (volume%) of the medium was plotted for three cases with specific gravities of 1.0, 1.5, and 2.0. Based on... Figure 4 When the copper particle content is 85% by mass, the volume of the medium is 44% by volume at a specific gravity of 2.0, 51% by volume at a specific gravity of 1.5, and 61% by volume at a specific gravity of 1.0. On the other hand, the interparticle voids of the core copper particles, even in the densest filling, are 26% by volume, and in the case of random filling, they are 35.9–44% by volume. Based on the above explanation, when using a medium with the lowest volume at a specific gravity of 2.0, if the copper content is below 85% by mass, the volume of the medium is greater than the volume of the interparticle voids, reducing the probability of particle-to-particle contact. Sintering copper microparticles requires particle-to-particle contact; however, with such a low probability of particle-to-particle contact, the possibility of sintering being hindered increases. Furthermore, when a medium larger than the interparticle voids is used, voids are easily left after the medium is removed due to volatilization or thermal decomposition, reducing the strength of the sintered structure. Furthermore, when the medium is liquid, if the interparticle voids are filled by the medium at a rate of less than 85% by mass, viscoelastic behavior will occur, making it difficult to process into sheets. Therefore, the proportion of micro-coated copper particles in the sheet bonding material is set to be greater than 85% by mass.

[0094] The proportion of micro-coated copper oxide particles in the sheet bonding material is preferably 90% by mass or more. From the viewpoint of improving adhesive strength, the higher the proportion of micro-coated copper oxide particles in the sheet bonding material, the better; however, the above proportion can be, for example, 98% by mass or less.

[0095] [medium]

[0096] In the sheet jointing material of the present embodiment, a medium is contained in addition to the micro-oxidized copper-coated copper particles. The medium can be liquid or solid. The liquid medium can be a dispersion medium used in the production of the sheet jointing material, or a medium caused by a solvent or the like. As the solid medium, a resin binder or the like can be given. As the liquid medium and the solid medium, known materials can be used. As the liquid medium, for example, in the case of amine, 2-(dimethylamino)ethanol, N-butyl diethanolamine, N-methyl diethanolamine, N-ethyl diethanolamine, diethanolamine, triethanolamine, 1- [bis(2-hydroxyethyl)amino] -2-propanol, ethylenediamine-N,N,N',N'-tetraethanol; in the case of glycol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, hexaethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, polypropylene glycol (diol type, triol type); and one or more of glycerin can be given.

[0097] [Other contents]

[0098] In the sheet jointing material of the present embodiment, a metal atom complex such as a copper particle monomer or a copper cluster can be contained in addition to the micro-oxidized copper-coated copper particles and the medium, within a range that does not interfere with the effects of the present embodiment. In the sheet jointing material of the present embodiment, an additive such as a dispersant can be contained as needed, within a range that does not interfere with the effects of the present embodiment. As the additive, known materials can be used.

[0099] The total proportion of the above-mentioned medium and other contents in the sheet jointing material is 15% by mass or less, more preferably 10% by mass or less, and further preferably 5% by mass or less.

[0100] The thickness of the sheet jointing material of the present embodiment can be appropriately set according to the desired joint. The thickness is preferably 1 μm or more and 1 mm or less. For example, the surface roughness of a copper foil for semiconductors is about 1 to 3 μm, and in order to obtain a joint with high strength integrated with a substrate, the jointing sheet needs to have a thickness sufficient to absorb the unevenness. Thus, the thickness is preferably 1 μm or more. On the other hand, the thickness is preferably 1 mm or less from the viewpoint of ensuring the structural strength of a power semiconductor, improving reliability, and preventing undesirable conditions such as exposure to the outside of the joint site during press bonding. The thickness can further be 0.5 mm or less, further 0.3 mm or less, further 0.10 mm or less, further 0.050 mm or less, and further 0.020 mm or less.

[0101] [Method for producing sheet jointing material]

[0102] The method for producing the sheet-shaped joining material is not limited, and for example, the following method can be used. As an example, the following method can be used: a slurry containing a cleaning solvent (for example, N,N-dimethylacetamide, toluene, hexane, or the like) and copper microparticles coated with copper oxide obtained in a purification step of producing the copper microparticles coated with copper oxide is subjected to solvent replacement with an alcohol solvent such as ethanol or the like, and the alcohol solvent of the supernatant is removed by centrifugal separation to obtain a wet cake of the copper microparticles coated with copper oxide. Although it is not necessarily required to replace with the alcohol solvent, since the slurry of the non-polar solvent such as toluene, hexane, or the like is not soluble in most of the dispersion medium described later, it is important to add the dispersion medium after replacing with the alcohol as a dissolving aid in order to obtain a mixture having high dispersibility.

[0103] Thereafter, as the dispersion medium, for example, in the case of amines, 2-(dimethylamino)ethanol, N-butyl diethanolamine, N-methyl diethanolamine, N-ethyl diethanolamine, diethanolamine, triethanolamine, 1- [bis(2-hydroxyethyl)amino] -2-propanol, triethanolamine, ethylenediamine-N,N,N',N'-tetraethanol are added, in the case of glycols, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, hexaethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, polypropylene glycol (diol type, triol type), and one or more of glycerol are added, and stirring and dispersion treatment are performed to obtain a paste. The above stirring and dispersion treatment can be performed using a disperser. As the disperser, for example, a twin-screw kneader, a three-roll mill, a planetary mixer, a self-rotation and revolution type stirring device, an ultrahigh-pressure disperser, a thin-film rotary type high-speed stirrer, a ball mill, a bead mill, or the like can be used. Thereafter, the obtained paste is maintained in a normal temperature vacuum until the mass is not changed to remove the alcohol solvent, and a powdery mixture of the copper microparticles coated with copper oxide and the medium from the above dispersion medium is obtained, in which the proportion of the copper microparticles coated with copper oxide is greater than 85% by mass.

[0104] The above powdery mixture is sufficiently kneaded to obtain a slightly sticky powder. As the kneader, for example, a continuous kneader of a single screw or a twin screw, an intermittent kneader using a roll mill, a mortar, an automatic mortar, a Hoover grinder, or the like can be used. Then, using the powder, molding is performed by cold rolling. For example, the powder is sandwiched in a PTFE sheet, pre-calendered using a rolling pin, and then press-molded to obtain a sheet-shaped joining material having a desired thickness. Subsequently, the molded body obtained by the above press-molding is sandwiched in a stainless steel sheet as needed, and is stage-calendered using a roll press to obtain a thinner sheet-shaped joining material having a desired thickness, for example, a thickness of about 0.05 to 0.4 mm.

[0105] After the thickness of the sheet-shaped joining material is made to have a desired thickness as described above, it can be punched to have a desired size and shape using a punch, a die, or the like as needed.

[0106] [Method for manufacturing bonded body]

[0107] In the present embodiment, a method for manufacturing a bonded body using the above-described sheet-shaped joining material is also included.

[0108] The method for manufacturing a bonded body includes:

[0109] arranging the above-described sheet-shaped joining material between the first member and the second member to obtain a laminate; and

[0110] heating the above-described laminate at 100 to 500°C to join the first member and the second member via the sintered product of the sheet-shaped joining material. If the sheet-shaped joining material of the present embodiment is used, the joining can be performed simply by arranging the sheet-shaped joining material between the first member and the second member at the time of joining, without the need for coating treatment such as printing or spraying on the surface of the members. Hereinafter, each step of the method for manufacturing a bonded body is described.

[0111] (Formation of laminate)

[0112] arranging the above-described sheet-shaped joining material between the first member and the second member to obtain a laminate. The material, shape, etc. of the first member and the second member constituting the above-described laminate are not limited, and can be determined according to the desired bonded body. At least one of the first member and the second member can be an IGBT, a diode, a power MOSFET, a power switch, a MOS-FET, a thyristor, a logic device, a sensor, an analog integrated circuit, an LED, a semiconductor laser, a rectifier, a transmitter, etc. as a semiconductor element, a lead frame, a metal-clad ceramic substrate (for example, DBC), a semiconductor element mounting substrate such as an LED package, a power supply member such as a copper foil tape, a metal block, a terminal, a heat dissipation plate, a water-cooling plate, etc. as a member other than a semiconductor element. At least one of the first member and the second member can be a semiconductor core sheet including the above-described semiconductor element. At least one of the first member and the second member is preferably a semiconductor element. For example, the laminate can be formed by sandwiching the sheet-shaped joining material of the present embodiment between a substrate and a semiconductor core sheet as the first member and the second member. On one or more of the first member and the second member, a metal layer such as a metal plating layer can be formed, as long as it does not interfere with the desired properties. As a metal element constituting the above-described metal layer, for example, nickel, palladium, copper, silver, gold, platinum, lead, tin, cobalt, zinc, manganese, aluminum, titanium, chromium, iron, molybdenum, etc. can be mentioned.

[0113] (Formation of bonded body obtained by heating laminate)

[0114] The above-described laminate is heated at a heating temperature of 100 to 500°C. If the sheet-shaped joining material of the present embodiment is used, sintering can be performed at a low temperature, and thus heating to 100°C or higher is sufficient. The heating temperature is preferably 150°C or higher. On the other hand, from the viewpoint of the heat resistance of the members constituting the electronic component, the heating temperature is preferably 500°C or lower. The holding time at the above-described heating temperature can be appropriately determined from the viewpoint of obtaining a sintered product, in accordance with the size of the joining body as the object, the amount of use of the sheet-shaped joining material, and the like. The holding time at the above-described heating temperature can be set to 1 minute or more and 60 minutes or less, for example. If the sheet-shaped joining material of the present embodiment is used, sintering can be promoted, and thus the holding time can also be set to 30 minutes or less, and can further be set to 20 minutes or less.

[0115] The above-described heating can be performed while pressing the laminate, or can be performed without pressing the laminate. By pressing the laminate, the growth of bubbles and cracks due to thermal expansion of voids in the laminate can be suppressed. In addition, by performing the pressing and heating treatment, a joining body having high adhesive strength can be manufactured in a short time. In the case of heating while pressing the laminate, it is preferable to perform heating in a state in which a load of 40 kPa or more is applied. The reason why the load is preferably set to 40 kPa or more is described below.

[0116] As described above, the sheet is composed of micro-oxidized copper-coated copper particles and a medium, and the lower limit value of the copper content is 85 mass%, and thus there can be inter-particle voids. In addition, at the time of joining, the joining sheet is sandwiched by the substrates, and becomes a state close to a closed system. Assuming that the sintered layer is a closed system, and assuming that it instantaneously reaches 200°C from 20°C, according to the Boyle-Charles law, the internal pressure is (473K / 293K) x atmospheric pressure = 164 kPa (absolute pressure). Since the atmospheric pressure is about 100 kPa, an internal pressure of 64 kPa can be generated in calculation. In addition, an increase in the internal pressure due to volatilization and thermal decomposition of the medium is also considered. In contrast, the pressure generated in the downward direction accompanying the weight of the substrate is extremely small, 0.4 kPa, in the mode of the embodiment. Thus, the state before heating is Figure 5A , however, in the case where the above-described internal pressure increases due to rapid heating, for example, as shown in Figure 5B , the substrate 21 is lifted and a void 25 is generated. The generation of the void 25 reduces the strength of the sintered structure, and thus is not preferable. Thus, as shown in Figure 5C , it is necessary to apply a pressure 27 higher than the increase in the internal pressure generated at the time of firing at the time of firing Figure 5CIn order to illustrate the image of the pressurization by the weight, however, the pressurization method can be a method generally used as described later). In an actual system, the temperature increasing rate is slower than the above-mentioned assumed condition, and since gas leaks from the side surface of the sheet as well, the internal pressure generated is smaller than the calculated value, and a load of 64 kPa does not need to be applied. However, according to the insight confirmed by another experiment using the joining paste, in order to obtain a sintered body in which voids are preferably sufficiently suppressed, more preferably a sintered body in which voids are not present at all, it is preferable to apply a pressure of about 40 kPa. Thus, as described above, the preferable load is set to 40 kPa or more.

[0117] As for the above-mentioned load, from the viewpoint of joining the particles more closely, 1 MPa or more is more preferable, and from the viewpoint of sintering in a shorter time, 10 MPa or more is further preferable. The above-mentioned pressurization and heating treatment can be exemplified by a method in which, for example, a laminated body is set to a pressurized state using a hot press, a jig, and then heated using a heating device such as a heater, an infrared heating furnace, an electromagnetic heating device, a hot plate, a hot air heating furnace, or the like.

[0118] As for the atmosphere in the manufacture of the joined body including the above-mentioned heating, from the viewpoint of preventing oxidation, it is preferable to be performed in a non-active atmosphere such as nitrogen, argon, or the like, and from the viewpoint of cost, it is preferable to be set to a nitrogen atmosphere. However, it is not limited thereto, and can be performed in the air depending on the heating conditions such as low temperature, short time, or the like.

[0119] The manufacturing method of the joined body can include only the process of forming the above-mentioned laminated body and the process of heating the laminated body to join the members, and other processes are not limited. As the other processes, for example, in order to form the laminated body, a preparation process such as making the first member, the second member, and the sheet-shaped joining material into a desired size, performing cleaning, or the like can be exemplified.

[0120] The manufacturing method of the joined body of the present embodiment can be applied to a manufacturing method of a semiconductor device. That is, at least one of the above-mentioned first member and the second member is a semiconductor element, and the above-mentioned joined body can be a semiconductor device.

[0121] [JOINED BODY]

[0122] In the present embodiment, a bonded body including a first member, a second member, and a sintered product of a sheet-like bonding material that bonds the first member and the second member is also included. The first member and the second member in the bonded body are as described above. The sheet-like bonding material as a precursor of the sintered product is as described above. The sintered product of the sheet-like bonding material refers to a sintered product obtained by heating the sheet-like bonding material, for example, under the conditions described above. The bonded body of the present embodiment can be bonded in the order of the first member - the sintered product of the sheet-like bonding material - the second member, that is, in a manner in which the first member is in direct contact with the sintered product of the sheet-like bonding material, and in addition to this, at least either one of between the first member and the sintered product of the sheet-like bonding material and between the second member and the sintered product of the sheet-like bonding material, a metal layer such as a metal plating layer formed on the surface of the member can be interposed, as long as it does not hinder the desired properties. As the metal that constitutes the metal layer, the aforementioned metal elements can be given.

[0123] The bonded body of the present embodiment can achieve a high adhesive strength of 30 MPa or more, further 50 MPa or more, and more further 70 MPa or more when the adhesive strength is measured by the method shown in the Examples described below.

[0124] As an example of the bonded body of the present embodiment, a semiconductor device in which at least one of the first member and the second member is a semiconductor element can be given. As the semiconductor element, the aforementioned semiconductor elements can be specifically given.

[0125] Examples

[0126] Hereinafter, the present application will be described more specifically by giving examples. The present application is not limited by the following examples, and can be appropriately changed within a range that can achieve the aforementioned and the following objects, and they are all included in the technical scope of the present application.

[0127] Synthesis of core-shell particles (copper oxide-coated copper particles)

[0128] Ethylene glycol (Showa Denko) 1388 g (22.4 mol) as a solvent, 1-amino-2-propanol (Showa Denko) 1182 g (15.7 mol) as a protective agent (amine compound), and acetic acid (Junsei Chemical) 473 g (7.9 mol) as a complexing agent were added to a reaction vessel, and after being sufficiently stirred, copper particles (Taiyo Kagaku TN-Cu100, particle size 50 to 200 nm) 100 g (1.6 mol) as a starting material were added. Note that the copper particles of the above-described commercially available starting material are copper oxide-coated copper raw material particles having a Cu2O layer. While the reaction vessel was subjected to water bath, hydrazine monohydrate (Showa Denko) 788 g (15.7 mol) as a reducing agent was added, and the reaction was performed while being stirred at 1100 rpm. The reaction was performed in the atmosphere. After the reaction, purification based on multiple centrifugation using N,N-dimethylacetamide, toluene, and hexane was performed, and a slurry containing a product was obtained. The mass of the micro copper oxide-coated copper particles in the slurry was calculated using the following formula (1).

[0129] [Num. 1]

[0130]

[0131] In formula (1),

[0132] Y: mass of particles in the slurry (g)

[0133] M s : mass of the slurry (g)

[0134] V s : volume of the slurry (cm 3 )

[0135] p m : density of the solvent (g / cm 3 )

[0136] p Cu : density of copper (g / cm 3 )

[0137] (Electron microscope observation of core-shell particles)

[0138] The resulting products were observed under an electron microscope. SEM images were obtained using a scanning electron microscope (SEM, JEM-6701F, 15kV accelerating voltage), TEM images were obtained using a transmission electron microscope (TEM, JEM-2000FX, 200kV accelerating voltage), and finally, STEM images were obtained using a scanning transmission electron microscope (STEM, JEM-ARM200F, 200kV accelerating voltage). All TEM and STEM observations were performed under conditions where the particles were dispersed without agglomeration.

[0139] As a result of the aforementioned electron microscopy observations, the obtained TEM images of the particles are represented as follows: Figure 6 In the middle. Then the obtained STEM image of the particles is represented on. Figure 7 According to Figure 6 TEM images confirmed that the generated particles were core-shell shaped, according to Figure 7 The STEM image confirms that the lattice spacing is copper at the core, and the surface of the core consists of Cu particles with a diameter of approximately 3 nm. 64 O and Cu8O nanoparticles are core-shell-shaped micro-copper oxide particles covered by a shell.

[0140] Among the aforementioned microparticles, micro-copper oxide nanoparticles with expanded copper oxide nanoparticles on the surface of submicron copper particles can be easily obtained, a phenomenon unattainable by conventional mixing methods. These core-shell micro-copper oxide particles contain Cu, which is reduced to metallic copper upon heating. 64 The O and Cu8O nanoparticle shells tightly connect adjacent copper microparticle cores, thereby significantly promoting the sintering between the core particles. The resulting sintered product has a structure in which highly crystalline copper microparticle cores are tightly connected, and high mechanical strength can be expected.

[0141] [Preparation of a powder mixture of micro-coated copper particles and dispersion medium]

[0142] By centrifugation, the dispersion medium of the slurry containing the synthesized copper micro-coated copper oxide particles was replaced from hexane with ethanol. Further centrifugation was performed to remove the ethanol supernatant, yielding a wet filter cake of copper micro-coated copper oxide particles. 7.5 parts by mass of triethanolamine (Fujifilm and Koujun Pharmaceutical) were added as the dispersion medium, relative to 92.5 parts by mass of copper micro-coated copper oxide particles in the wet filter cake (calculated using formula (1)). After addition, the mixture was stirred for 4 minutes using a rotary mixer (THINKY AR-100), and then dispersed intermittently for 3 minutes using a thin-film rotary high-speed mixer (PRIMIX FILMIX 56-L) to obtain a dispersed paste. Subsequently, the ethanol was removed by maintaining the mixture under vacuum at room temperature until no mass change occurred, yielding a powdery mixture of copper micro-coated copper oxide particles and the medium from the aforementioned dispersion medium.

[0143] (TG-DTA determination of a powder mixture of copper particles coated with micro-copper oxide and dispersion medium)

[0144] Thermogravimetric / differential thermal analysis (TG-DTA) of the obtained powder mixture was performed using a Shimadzu TG / DTA simultaneous determination apparatus under a 3% hydrogen-nitrogen mixed gas atmosphere at a heating rate of 5°C / min. The TG-DTA curves are presented as the analytical results. Figure 8 According to Figure 8 The mass reduction shown by TGA confirms that the resulting mixture contains 93.8% by mass of micro-coated copper oxide particles.

[0145] [Preparation of materials for sheet bonding]

[0146] As a pretreatment, the above-mentioned powder mixture was thoroughly mixed in a mortar to obtain a slightly viscous powder. This powder was spread in squares of several centimeters on a PTFE sheet (made by Nitto Denko, 0.1 mm thick), sandwiched between the PTFE sheet from above, and stretched into a sheet shape using a metal rod on a smooth table. It was then pressed to obtain a uniform sheet bonding material A with a thickness of approximately 0.3 mm. Subsequently, sheet bonding material A was sandwiched between a stainless steel sheet (0.1 mm thick) and rolled in stages using a roller press to obtain sheet bonding material B with a thickness of approximately 0.15 mm. It should be noted that the content of micro-coated copper particles in these sheet bonding materials is substantially the same as that in the above-mentioned mixture, at 93.8% by mass.

[0147] [Evaluation of joint firing]

[0148] Two copper test pieces were bonded together using the obtained sheet bonding material. The bonded sample was then prepared by firing the sheet bonding material, and the bond strength was measured.

[0149] (Production of joint sintering evaluation sample)

[0150] The production steps of the joint sintering evaluation sample are shown in Figure 9 First, from a 5 mm-thick oxygen-free copper plate (C1020P), as a circular copper test piece, a 12 mm-diameter copper test piece 1 and a 5 mm-diameter copper test piece 2 were cut out as shown in Figure 10A The surface of each copper test piece was polished with a polishing cloth impregnated with a 0.5 μm alumina powder suspension, and then degreased to produce the sample. Just before the above-mentioned sheet joint material was attached, each copper test piece was immersed in 2.5 M hydrochloric acid to remove the surface copper oxide film, and then washed thoroughly with pure water and methanol, and dried.

[0151] A 6 mm-diameter sheet 3 cut out from the above-mentioned sheet joint material A and sheet joint material B with a punch was attached between the 12 mm-diameter copper test piece 1 and the 5 mm-diameter copper test piece 2 as shown in Figure 10B After that, in a state where a load of 15 MPa was applied to the attached two copper test pieces in the direction of the arrow of Figure 10B at a high rate of 90°C / min to reach a temperature (3 levels of 150°C, 200°C, and 250°C), and after the temperature was maintained at the reached temperature for 15 minutes, the sample was taken out of the hot press and quenched to room temperature to obtain a joint sintering evaluation sample in which the copper test pieces were bonded together with a sintered product of the sheet joint material.

[0152] (Joint sintering evaluation test (determination of bonding strength))

[0153] The bonding strength of the joint sintering evaluation sample was evaluated using a 5 kN material testing machine (manufactured by Shimadzu Corporation). Specifically, as shown in the schematic cross-sectional view given in Figure 10C , a load was applied in parallel to the coated surface of the test piece at a rate of 1 mm / min, and the breaking load of the copper test piece was determined as the bonding strength.

[0154] As a result of the above determination, the relationship between the sintering temperature (reached temperature, "sintering temperature" in Figure 11 ) and the bonding strength (shear strength, "shear strength" in Figure 11 ) when the sheet joint material A was used is shown in Figure 11The adhesive strength of each of two averages of the sheet-shaped joining material A having a thickness of 0.3 mm was 34 MPa at a firing temperature of 150°C, 59 MPa at 200°C, and 79 MPa at 250°C, which were high values. It was also confirmed that even in the case of the sheet-shaped joining material B having a thickness of 0.15 mm, the adhesive strength of two averages was 56 MPa at a firing temperature of 200°C, which was sufficiently high.

[0155] Based on the above results, according to the present embodiment, a high-concentration copper joining material having few voids and cracks accompanying volatilization of the dispersion medium can be easily obtained, and thus the Cu 64 The O and Cu8O nanoparticle shells tightly sinter and connect between adjacent copper microparticle cores to obtain a firm joining as described above Figure 3 The present embodiment can maximize the characteristics of the core-shell copper oxide particle-containing particles. The sheet-shaped joining material of the present embodiment can be cut to a desired size using a punch, a die, or the like in the joining process, and thus it can be joined by, for example, only being sandwiched between a substrate and a semiconductor core sheet and being hot-pressed, which greatly simplifies the process and significantly contributes to work load reduction.

[0156] [Conductivity Evaluation]

[0157] (Production of Sample for Conductivity Evaluation)

[0158] An alumina plate (AO-5050 manufactured by FURUUCHI CHEMICAL) having a thickness of 1 mm was cut into a size of 5 cm x 2.5 cm, and used as an alumina substrate in the evaluation. On the surface of the alumina substrate, the sheet-shaped joining material A cut into a size of 2 cm square was placed so as to be in close contact with the alumina substrate. This was put into a tubular furnace, and 3% hydrogen / nitrogen mixed gas was supplied at a flow rate of 1 L / min into the tube to perform gas replacement for 30 minutes or more at normal temperature. Thereafter, while nitrogen gas was supplied at a flow rate of 1 L / min into the tube, the temperature was increased to 200°C over about 20 minutes, and after being maintained at 200°C for 1 hour, the temperature was naturally cooled to normal temperature, to obtain a substrate on which a sintered product of the sheet-shaped joining material was formed. Note that the series of operations from the placement of the sheet-shaped joining material A to the maintenance at the evaluation temperature and the natural cooling to normal temperature were performed in a nitrogen atmosphere.

[0159] (Measurement of Volume Resistivity)

[0160] To evaluate the conductivity of the sintered material, the volume resistivity was measured using a resistivity meter (Mitsubishi Chemical ANALYTECH Loresta GP, ASP probe) with a 6-point average. During the volume resistivity measurement, the resistivity correction count (RCF) to account for the shape of the coating was calculated using the Loresta GP. The film thickness of the sintered material was calculated from an image obtained by observing a fractured cross-section of the substrate with the sintered material using a microscope (Keyence VHX-7000 digital microscope). The measured results showed that the volume resistivity of the sintered material was 4 × 10⁻⁶. -6 Ωcm. This value is the resistivity of bulk copper at 0°C (1.55 × 10⁻⁶ Ωcm). -6 It is about 2.5 times that of Ωcm, which is an extremely good value.

[0161] The above results confirm that the sheet bonding material of the present invention can also be used as a conductive sheet, exhibiting extremely high conductivity. In the sheet bonding material of this embodiment, the micro-copper oxide-coated copper particles have metallic copper as their core, and the content of copper oxides such as CuO and Cu2O, which can increase resistance, is suppressed. Therefore, the sintered product (bonding part) obtained by sintering these micro-copper oxide-coated copper particles exhibits high electrical conductivity and is not considered to hinder the characteristics of electronic components and electronic devices used as bonding bodies.

[0162] This implementation may include the following methods.

[0163] Embodiment 1 of the present invention is a sheet bonding material comprising copper particles coated with micro-copper oxide and a medium, wherein the copper particles coated with micro-copper oxide have copper particles as a core and contain Cu. 64 A shell of one or more micro-copper oxides, including O and Cu8O.

[0164] The content of the copper particles coated with the aforementioned micro-copper oxide is greater than 85% by mass.

[0165] Embodiment 2 of the present invention is based on the sheet bonding material described in Embodiment 1, wherein,

[0166] The above Cu 64 One or more of O and Cu8O are micro-copper oxide particles with an average particle size of 1 nm or more and 20 nm or less.

[0167] Embodiment 3 of the present invention is based on the sheet bonding material described in Embodiment 1 or 2, wherein,

[0168] The average particle size of the copper particles used as the core is greater than 20 nm and less than 2 μm.

[0169] The fourth embodiment of the present invention is a sheet bonding material according to any one of embodiments 1 to 3, wherein the thickness is 1 μm or more and 1 mm or less.

[0170] Mode 5 of the present application is a method for manufacturing a bonded body, the method comprising:

[0171] arranging the sheet-like bonding material described in any one of Modes 1 to 4 between the first member and the second member to obtain a laminate; and

[0172] heating the laminate at 100 to 500°C to bond the first member and the second member via the sintered product of the sheet-like bonding material.

[0173] Mode 6 of the present application is the method for manufacturing a bonded body according to Mode 5, wherein

[0174] the heating of the laminate is performed under pressurization of 40 kPa or more.

[0175] Mode 7 of the present application is the method for manufacturing a bonded body according to Mode 5 or 6, wherein

[0176] at least one of the first member and the second member is a semiconductor element, and the bonded body is a semiconductor device.

[0177] Mode 8 of the present application is a bonded body comprising a first member, a second member, and a sintered product of the sheet-like bonding material described in any one of Modes 1 to 4 that bonds the first member and the second member.

[0178] Mode 9 of the present application is the bonded body according to Mode 8, wherein at least one of the first member and the second member is a semiconductor element, and the bonded body is a semiconductor device.

[0179] This application claims priority from Japanese Patent Application No. 2023-063000, which is hereby incorporated by reference into the present specification.

[0180] Industrial Applicability

[0181] The sheet-like bonding material of the present embodiment is preferably used, for example, for the manufacture of electronic parts along with the bonding of members that constitute the electronic parts. It can be suitably used, for example, for the manufacture of semiconductor devices such as SiC power semiconductors that require high adhesive strength between members.

[0182] Explanation of Reference Signs

[0183] 1, 2: copper test pieces, 3: sheet-shaped joining material, 4: fixture for fixing test machine, 11: core copper particles, 13: oxidation film, 15A: conventional sintered body, 15B: sintered body of the present embodiment, 17: nano particles, 21: substrate, 23: micro-oxidized copper-coated copper particles, 25: voids, 27: pressurization.

Claims

1. A sheet-shaped joining material comprising micro-oxidized copper-coated copper particles and a medium, The micro-oxidized copper-coated copper particle has a copper particle as a core and a shell containing one or more of CuO and Cu8O 64 The one or more micro-oxidized coppers of CuO and Cu8O are micro-oxidized copper particles having an average particle diameter of 1 nm or more and 20 nm or less 64 The one or more micro-oxidized coppers of CuO and Cu8O are micro-oxidized copper particles having an average particle diameter of 1 nm or more and 20 nm or less the content of the micro-oxidized copper-coated copper particles is more than 85 mass%.

2. The sheet-shaped joining material according to claim 1, wherein, the average particle diameter of the copper particles as the core is 20 nm or more and less than 2 μm.

3. The sheet-shaped joining material according to claim 1, having a thickness of 1 μm or more and 1 mm or less.

4. A method for manufacturing a joined body, the method comprising: arranging the sheet-shaped joining material according to any one of claims 1 to 3 between a first member and a second member to obtain a laminate; and heating the laminate at 100°C to 500°C to join the first member and the second member via a sintered product of the sheet-shaped joining material.

5. The method for manufacturing a joined body according to claim 4, wherein, the heating of the laminate is performed under pressurization of 40 kPa or more.

6. The method for manufacturing a joined body according to claim 4, wherein, at least one of the first member and the second member is a semiconductor element, and the joined body is a semiconductor device.

7. A joined body comprising a first member, a second member, and a sintered product of the sheet-shaped joining material according to any one of claims 1 to 3 that joins the first member and the second member.

8. The joined body according to claim 7, wherein, at least one of the first member and the second member is a semiconductor element, and the joined body is a semiconductor device.

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