Manufacturing method of assembly, assembly, metal paste for joints, and manufacturing method thereof

Abstract

To provide a method for manufacturing a joined body capable of sufficiently suppressing the falling of a member in the manufacture of the joined body using metal paste, the metal paste for joining capable of being used in such a method, a method for manufacturing the same, and the joined body.SOLUTION: The method for manufacturing the metal paste for joints includes a step of adjusting a dispersion liquid by mixing at least metal particles that have a first fatty acid having 10 or more carbon atoms on a surface thereof, a second fatty acid having 10 or more carbon atoms, a reducing agent that is polyhydric alcohol, and a polyether-based compound. The manufacturing method of the assembly includes a first step of forming a coating film of the metal paste for joints by applying the metal paste for joints, which is obtained by the above-described method, onto the first member, a second step of forming the metal particle-containing layer by drying the coating film, a third step of obtaining a laminated body by disposing the second member on the metal particle-containing layer, and a fourth step of sintering the metal particle-containing layer of the laminated body.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a bonded body, a bonded body, a bonding metal paste, and a method for manufacturing the same. [Background technology]

[0002] When manufacturing semiconductor devices, various bonding materials are used to form a bonding layer that bonds a semiconductor element to a lead frame or the like (supporting member). For example, high-lead solder has been used to form the bonding layer for bonding power semiconductors, LSIs, and the like that operate at temperatures up to about 150°C. In recent years, semiconductor elements have become higher capacity and more space-saving, and there is an increasing demand for semiconductors to operate at high temperatures of 175°C or higher. In order to ensure the operational stability of such semiconductor devices, the bonding layer must have connection reliability and high thermal conductivity. However, in the temperature range of 175°C or higher, the bonding layers of the high-lead solder and lead-free solder that have been used in the past have issues with connection reliability and also have insufficient thermal conductivity (30 Wm -1 K -1 ) and therefore alternative materials are needed.

[0003] As one of the joining methods using alternative materials, a joining method utilizing the low-temperature sintering phenomenon of copper fine particles has been proposed. The sintered copper layer formed by this method has excellent mechanical strength, making it easy to achieve connection reliability at high temperatures, and can also keep material costs low. As such a sintered copper layer, a sintered copper layer obtained by reducing and sintering copper oxide particles has been proposed (see Patent Document 1 and Non-Patent Document 1 below). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5006081 [Non-patent literature]

[0005] [Non-Patent Document 1] T. Morita, Y. Yasuda: Materials Transactions, 56(6), 2015, 878-882 Summary of the Invention [Problem to be solved by the invention]

[0006] Power modules and the like in which a support member and a semiconductor element are bonded via a sintered copper layer are typically manufactured through the following process. First, a copper paste is prepared by dispersing copper particles in a liquid dispersion medium. This copper paste is then applied to a support member to form a copper paste coating. Next, the coating is dried to form a copper particle-containing layer, and the semiconductor element is placed on top of this. The resulting laminate is then transported to a sintering furnace or the like, and the copper particle-containing layer is sintered to bond the support member and the semiconductor element.

[0007] Conventional copper pastes, when dried, are difficult to obtain the property (hereinafter also referred to as tackiness) that allows them to temporarily bond semiconductor elements, etc. If the semiconductor elements fall off during transportation of the laminate, this leads to a decrease in yield in the production of joined bodies such as power modules.

[0008] Therefore, an object of the present invention is to provide a method for manufacturing a bonded body that can sufficiently suppress the detachment of components when manufacturing a bonded body using a metal paste, a bonding metal paste that can be used in such a method, a method for manufacturing the same, and a bonded body. [Means for solving the problem]

[0009] The present invention relates to the following [1] to

[11] .

[0010] [1] A method for producing a metal paste for joining, comprising the step of preparing a dispersion by mixing at least metal particles having a first fatty acid having 10 or more carbon atoms on their surfaces, a second fatty acid having 10 or more carbon atoms, a reducing agent which is a polyhydric alcohol, and a polyether-based compound. [2] The method for producing a metal paste for bonding according to [1], wherein the second fatty acid is stearic acid. [3] The method for producing a metal paste for bonding according to [1] or [2], wherein the polyether-based compound is a polyoxyalkylene alkyl ether. [4] The method for producing a metal paste for bonding according to any one of [1] to [3], wherein the polyhydric alcohol is polyethylene glycol. [5] A metal joining paste comprising metal particles having a first fatty acid having 10 or more carbon atoms on their surface, a second fatty acid having 10 or more carbon atoms, a reducing agent which is a polyhydric alcohol, and a polyoxyalkylene alkyl ether. [6] The metal paste for joining according to [5], wherein the second fatty acid is stearic acid. [7] The metal paste for bonding according to [5] or [6], wherein the polyhydric alcohol is polyethylene glycol. [8] A joined body comprising a first member, a second member, and a joining portion that joins them, 8. A joined body, wherein the joint portion comprises a sintered body of the metal bonding paste according to claim 5. [9] A first step of applying a metal bonding paste obtained by the method according to any one of [1] to [4] onto a first member to form a coating film of the metal bonding paste; a second step of drying the coating to form a metal particle-containing layer; a third step of disposing a second member on the metal particle-containing layer to obtain a laminate; a fourth step of sintering the metal particle-containing layer of the laminate; A method for manufacturing a bonded body, comprising:

[10] The method for producing a joined body according to [9], wherein in the third step, a second member is placed on the metal particle-containing layer that has been heated to 90°C or higher.

[11] A first step of applying the metal bonding paste according to any one of [5] to [7] onto a first member to form a coating film of the metal bonding paste; a second step of drying the coating to form a metal particle-containing layer; a third step of disposing a second member on the metal particle-containing layer to obtain a laminate; a fourth step of sintering the metal particle-containing layer of the laminate; A method for manufacturing a bonded body, comprising:

[12] The method for producing a joined body according to

[11] , wherein in the third step, a second member is placed on the metal particle-containing layer that has been heated to 90°C or higher. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a method for manufacturing a bonded body that can sufficiently suppress the detachment of components when manufacturing a bonded body using a metal paste, a metal paste that can be used in such a method, a method for manufacturing the same, and a bonded body. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 2 is a schematic diagram for explaining a method for measuring tack strength. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes in detail an embodiment of the present invention (hereinafter referred to as the "present embodiment"). The present invention is not limited to the following embodiment.

[0014] <Method of manufacturing the bonded body> The method for manufacturing a bonded body of this embodiment includes the following steps: a first step of forming, on a first component, a coating film of a metal paste containing metal particles having, on their surfaces, a first fatty acid having 10 or more carbon atoms, a second fatty acid having 10 or more carbon atoms, a reducing agent that is a polyhydric alcohol, and a polyether compound; a second step of drying the coating film to form a metal particle-containing layer; a third step of arranging a second component on the metal particle-containing layer to obtain a laminate; and a fourth step of sintering the metal particle-containing layer of the laminate.

[0015] In the method for producing a bonded body of this embodiment, the metal particle-containing layer has excellent tackiness, which improves the tack strength between the first and second members in the laminate, thereby preventing the first or second member from falling off during transport of the laminate.

[0016] The inventors speculate as follows as to why the metal particle-containing layer has excellent tack strength. The surfaces of metal particles protected with a first fatty acid having 10 or more carbon atoms exhibit hydrophobic properties because the long-chain alkyl groups are arranged outward. The polyhydric alcohol added as a reducing agent is hydrophilic and therefore has poor wettability with the metal particles protected with the fatty acid. However, when the metal paste contains a combination of a second fatty acid having 10 or more carbon atoms and a polyether compound, these are coordinated in multiple layers on the surfaces of the metal particles, buffering the hydrophobicity. This is thought to result in improved wettability between the metal particles and the polyhydric alcohol. The inventors speculate that this causes a liquid film of the polyhydric alcohol to form on the surfaces of the metal particles, making the metal particle-containing layer more susceptible to plastic deformation, thereby improving tack strength.

[0017] Furthermore, by including a combination of a second fatty acid having 10 or more carbon atoms and a polyether compound in the metal paste, the second fatty acid and the polyether compound can be coordinated in a multilayer structure without being detached from the surface of the metal particles, even if the drying time of the coating film is extended in the second step. As a result, the tack strength is improved even if the drying time of the coating film is extended and the drying temperature is increased in the second step.

[0018] Examples of the first member and the second member include semiconductor elements such as IGBTs, diodes, Schottky barrier diodes, MOS-FETs, thyristors, logic, sensors, analog integrated circuits, LEDs, semiconductor lasers, and oscillators; base materials for mounting semiconductor elements such as lead frames, metal plate-attached ceramic substrates (e.g., DBCs), and LED packages; power supply members such as copper ribbons, metal blocks, and terminals; heat sinks; and water-cooled plates.

[0019] The first and second members may have a metal layer on their joining surfaces that forms a metal bond with the sintered body of the metal paste. Examples of metals constituting the metal layer include copper, nickel, silver, gold, palladium, platinum, lead, tin, and cobalt. These metals may be used singly or in combination of two or more. The metal layer may also be an alloy containing the above metals. In addition to the above metals, examples of metals used in alloys include zinc, manganese, aluminum, beryllium, titanium, chromium, iron, and molybdenum. Examples of members having a metal layer include members plated with various metals, wires, chips plated with metals, heat spreaders, ceramic substrates with metal plates attached, lead frames plated with various metals or made of various metals, copper plates, and copper foils.

[0020] (1st step) The metal paste used in this embodiment may contain metal particles having a first fatty acid having 10 or more carbon atoms on their surface, a second fatty acid having 10 or more carbon atoms, a reducing agent which is a polyhydric alcohol, a polyether compound, and a liquid dispersion medium.

[0021] [First fatty acid] Examples of the first fatty acid having 10 or more carbon atoms include acetic acid, propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, caprylic acid, methylheptanoic acid, ethylhexanoic acid, propylpentanoic acid, pelargonic acid, methyloctanoic acid, ethylheptanoic acid, propylhexanoic acid, capric acid (decanoic acid), methylnonanoic acid, ethyloctanoic acid, propylheptanoic acid, butylhexanoic acid, undecanoic acid, methyldecanoic acid, ethylnonanoic acid, propyloctanoic acid, butyl Heptanoic acid, lauric acid, methyl undecanoic acid, ethyl decanoic acid, propyl nonanoic acid, butyl octanoic acid, pentyl heptanoic acid, tridecanoic acid, methyl dodecanoic acid, ethyl undecanoic acid, propyl decanoic acid, butyl nonanoic acid, pentyl octanoic acid, myristic acid, methyl tridecanoic acid, ethyl dodecanoic acid, propyl undecanoic acid, butyl decanoic acid, pentyl nonanoic acid, hexyl octanoic acid, pentadecanoic acid, methyl tetradecanoic acid, ethyl tridecanoic acid, propyl dodecanoic acid Saturated fatty acids such as octenoic acid, butylundecanoic acid, pentyldecanoic acid, hexylnonanoic acid, palmitic acid, methylpentadecanoic acid, ethyltetradecanoic acid, propyltridecanoic acid, butyldodecanoic acid, pentylundecanoic acid, hexyldecanoic acid, heptylnonanoic acid, heptadecanoic acid, octadecanoic acid, methylcyclohexanecarboxylic acid, ethylcyclohexanecarboxylic acid, propylcyclohexanecarboxylic acid, butylcyclohexanecarboxylic acid, pentylcyclohexanecarboxylic acid, hexylcyclohexanecarboxylic acid, heptylcyclohexanecarboxylic acid, octylcyclohexanecarboxylic acid, and nonylcyclohexanecarboxylic acid; and unsaturated fatty acids such as octenoic acid, nonenoic acid, methylnonenoic acid, decenoic acid, undecenoic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, myristoleic acid, pentadecenoic acid, hexadecenoic acid, palmitoleic acid, sapienic acid, oleic acid, vaccenic acid, linoleic acid, linoleic acid, and linolenic acid.

[0022] The first fatty acid may be a fatty acid having 10 to 18 carbon atoms from the viewpoint of particle dispersion stability and oxidation prevention, and may be lauric acid or decanoic acid from the viewpoint of low-temperature decomposition and low-temperature sintering properties.

[0023] The first fatty acid may be used alone or in combination of two or more.

[0024] [Metal particles] Examples of metal particles include copper particles, silver particles, gold particles, platinum group particles (platinum, palladium, rhodium, iridium), magnetic particles (iron, cobalt, nickel), light metal particles (aluminum, beryllium, magnesium, titanium, alkali metals, alkaline earth metals), low-melting point particles (tin, indium, lead, germanium), other common transition metal particles, and semi-metal particles, as well as alloy particles that combine two or more of these.

[0025] The metal particles may be sinterable in a temperature range of 200°C or higher and 300°C or lower.

[0026] Metal paste can contain copper particles as metal particles. In this case, the metal oxide film on the particle surface is easily reduced by the reducing solvent used in the paste, making it possible to sinter under mild conditions of low temperature (300°C or less) and low pressure (10 MPa or less).

[0027] The copper particles include submicro copper particles and micro copper particles. The copper particles refer to particles containing copper as a main component, for example, particles having a copper content of 80% by mass or more. The copper content of the copper particles may be 85% by mass or more, 90% by mass or more, 95% by mass or more, 99% by mass or more, or 100% by mass.

[0028] The submicron copper particles may be copper particles that are sinterable in a temperature range of 200°C to 380°C. Examples of submicron copper particles include copper particles having a particle size of 0.05 μm to 0.8 μm. For example, copper particles having a volume average particle size of 0.05 μm to 0.8 μm can be used. When the volume average particle size of the submicron copper particles is 0.05 μm or more, effects such as reduced synthesis costs, good dispersibility, and reduced amounts of organic protective agents used are easily achieved. When the volume average particle size of the submicron copper particles is 0.8 μm or less, the effect of excellent sinterability of the submicron copper particles is easily achieved. From the viewpoint of further achieving the above effects, the volume average particle size of the submicron copper particles may be 0.6 μm or less, 0.5 μm or less, or 0.4 μm or less. Furthermore, the volume average particle size of the submicron copper particles may be 0.05 μm or more, 0.07 μm or more, or 0.1 μm or more. The volume average particle size of the submicron copper particles may be, for example, 0.05 μm or more and 0.5 μm or less, 0.07 μm or more and 0.8 μm or less, 0.08 μm or more and 0.8 μm or less, 0.08 μm or more and 0.6 μm or less, 0.1 μm or more and 0.5 μm or less, or 0.2 μm or more and 0.45 μm or less.

[0029] In this specification, the volume average particle size refers to the 50% volume average particle size. The volume average particle size of metal particles can be determined by, for example, dispersing raw material metal particles or dried copper particles obtained by removing volatile components from a metal paste in a dispersion medium using a dispersant, and measuring the resulting dispersion medium with a light scattering particle size distribution analyzer (e.g., a Shimadzu nanoparticle size distribution analyzer (SALD-7500nano, manufactured by Shimadzu Corporation)). When using a light scattering particle size distribution analyzer, the dispersion medium can be, for example, hexane, toluene, α-terpineol, 4-methyl-1,3-dioxolan-2-one, or water.

[0030] The content of the submicron copper particles may be 20% by mass or more, 30% by mass or more, 35% by mass or more, 40% by mass or more, 90% by mass or less, 85% by mass or less, or 80% by mass or less, or 20% by mass or more to 90% by mass or less, 30% by mass or more to 90% by mass or less, 35% by mass or more to 85% by mass or less, 40% by mass or more to 80% by mass or less, or 60% by mass or more to 80% by mass or less, based on the total mass of the metal particles. If the content of the submicron copper particles is within the above range, it is easy to ensure the bonding strength of the bonded body, and when the bonded members are semiconductor elements, the semiconductor device tends to exhibit good die shear strength and connection reliability.

[0031] The content of the submicron copper particles may be 20% by mass or more and 90% by mass or less, based on the total mass of the copper particles. When the content of the submicron copper particles is 20% by mass or more, when used in combination with microcopper particles such as flaky microcopper particles, the spaces between the copper particles can be sufficiently filled, making it easier to ensure the bonding strength of the bonded body. When the bonded members are semiconductor elements, the semiconductor device tends to exhibit good die shear strength and connection reliability. When the content of the submicron copper particles is 90% by mass or less, the volumetric shrinkage of the sintered layer in the in-plane directions (X and Y directions) during sintering with or without pressure can be sufficiently suppressed, making it easier to ensure the bonding strength of the bonded body. When the bonded members are semiconductor elements, the semiconductor device tends to exhibit good die shear strength and connection reliability. From the viewpoint of further achieving the above-mentioned effect, the content of the submicron copper particles may be 30% by mass or more, 35% by mass or more, 40% by mass or more, 85% by mass or less, 83% by mass or less, 80% by mass or less, 30% by mass or more and 85% by mass or less, 35% by mass or more and 85% by mass or less, 40% by mass or more and 80% by mass or less, or 60% by mass or more and 80% by mass or less, based on the total mass of the copper particles.

[0032] The shape of the submicron copper particles is not particularly limited. Examples of the shape of the submicron copper particles include spherical, blocky, needle-like, flake-like, approximately spherical, and aggregates thereof. From the viewpoint of dispersibility and packing property, the shape of the submicron copper particles may be spherical, approximately spherical, or flake-like. From the viewpoint of combustibility, dispersibility, mixability with flaky microparticles, etc., the shape may be spherical or approximately spherical. In this specification, the term "flake-like" includes flat shapes such as plate-like and scale-like.

[0033] From the viewpoints of dispersibility, packing property, and mixability with flaky microparticles, the aspect ratio of the submicron copper particles may be 5 or less, 4 or less, or 3 or less. In this specification, the "aspect ratio" refers to the long side (major axis) / thickness of the particle. The long side (major axis) and thickness of the particle can be measured, for example, from an SEM image of the particle.

[0034] The submicron copper particles may be treated with a surface treatment agent comprising the first fatty acid described above.

[0035] The amount of the surface treatment agent to be used for treatment may be an amount that allows one to three molecular layers to adhere to the surface of the sub-micron copper particles. This amount depends on the number of molecular layers (n) attached to the surface of the sub-micron copper particles and the specific surface area (A p ) (unit: m 2 / g) and the molecular weight of the surface treatment agent (M s ) (unit: g / mol) and the minimum coverage area of ​​the surface treatment agent (S S ) (unit: m 2 / unit) and Avogadro's number (N A )(6.02×10 23 Specifically, the amount of surface treatment agent can be calculated by the following formula: Treatment amount of surface treatment agent (mass%) = {(n·A p M s ) / (S S N A +n·A p M s )}×100%.

[0036] The specific surface area of ​​submicro copper particles can be calculated by measuring the dried submicro copper particles using the BET specific surface area measurement method. The minimum coverage area of ​​the surface treatment agent is 2.05 × 10 when the surface treatment agent is a linear saturated fatty acid. -19 m 2 The carbon content of the surface treatment agent is 1 / molecule. For other surface treatment agents, measurement can be performed, for example, by calculation using a molecular model or by the method described in "Chemistry and Education" (Kamieda Katsuhiro, Inafuku Sumio, Mori Iwao, 40(2), 1992, pp. 114-117). Here is an example of a method for quantifying the surface treatment agent. The surface treatment agent can be identified by thermal desorption gas chromatography-mass spectrometry of the dried powder obtained by removing the dispersant from the metal paste, thereby determining the carbon number and molecular weight of the surface treatment agent. The carbon content of the surface treatment agent can be analyzed by carbon content analysis. Examples of carbon content analysis methods include high-frequency induction heating furnace combustion / infrared absorption. The amount of the surface treatment agent can be calculated using the above formula from the carbon number, molecular weight, and carbon content of the identified surface treatment agent.

[0037] The amount of the surface treatment agent may be 0.1% by mass or more, 1% by mass or more, 5% by mass or more, 8% by mass or more, 15% by mass or less, 12% by mass or less, 0.1% by mass or more and 15% by mass or less, 1% by mass or more and 15% by mass or less, 5% by mass or more and 15% by mass or less, or 8% by mass or more and 12% by mass or less, based on the mass of the submicron copper particles having the surface treatment agent.

[0038] The submicron copper particles can be commercially available. Examples of commercially available submicron particles include CH-0200 (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 0.36 μm), CH-0200A-L1 (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 0.21 μm), HT-14 (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 0.41 μm), CT-500 (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 0.72 μm), and Tn-Cu100 (manufactured by Taiyo Nippon Sanso Co., Ltd., volume average particle size 0.12 μm).

[0039] The micro copper particles may be copper particles having a particle size of 2 μm to 50 μm, for example, copper particles having a volume average particle size of 2 μm to 50 μm. When the volume average particle size of the micro copper particles is within the above range, volume shrinkage in the in-plane direction (XY direction) of the sintered layer and the generation of voids during sintering without or under pressure can be sufficiently reduced, making it easier to ensure the bonding strength of the bonded body. When the bonded components are semiconductor elements, the semiconductor device tends to exhibit good die shear strength and connection reliability. To further achieve the above effects, the volume average particle size of the micro copper particles may be 2 μm or more, 3 μm or more, 20 μm or less, 15 μm or less, 10 μm or less, 2 μm to 20 μm, 2 μm to 10 μm, 3 μm to 20 μm, or 3 μm to 10 μm.

[0040] The shape of the micro copper particles is preferably flake-like. By using flake-like micro copper particles, the micro copper particles in the metal particle-containing layer are oriented approximately parallel to the bonding surface, thereby suppressing volume shrinkage when the metal particle-containing layer is sintered, making it easier to ensure the bonding strength of the bonded body. When the members to be bonded are semiconductor elements, the semiconductor device tends to exhibit good die shear strength and connection reliability. From the viewpoint of further achieving the above effects, the flake-like micro copper particles may have an aspect ratio of more than 2, 4 or more, 6 or more, 10 or more, or 50 or more.

[0041] The content of the micro copper particles may be 10% by mass or more and 90% by mass or less, 15% by mass or more and 65% by mass or less, or 20% by mass or more and 60% by mass or less, based on the total mass of the copper particles. If the content of the micro copper particles is within the above range, it is easy to ensure the bonding strength of the bonded body, and when the bonded members are semiconductor elements, the semiconductor device tends to exhibit good die shear strength and connection reliability.

[0042] There is no particular limitation on whether or not the micro copper particles are treated with a surface treatment agent, but from the viewpoint of dispersion stability and oxidation resistance, the micro copper particles may be treated with a surface treatment agent containing the above-mentioned first fatty acid.

[0043] The amount of the surface treatment agent may be an amount equal to or greater than one molecular layer on the particle surface. The amount of the surface treatment agent varies depending on the specific surface area of ​​the micro copper particles, the molecular weight of the surface treatment agent, and the minimum coverage area of ​​the surface treatment agent. The amount of the surface treatment agent may be 0.1% by mass or more, 1% by mass or more, 5% by mass or more, 8% by mass or more, 15% by mass or less, 12% by mass or less, 0.1% by mass or more to 15% by mass or less, 1% by mass or more to 15% by mass or less, 5% by mass or more to 15% by mass or less, or 8% by mass or more to 12% by mass or less, based on the mass of the micro copper particles containing the surface treatment agent. The specific surface area of ​​the micro copper particles, the molecular weight of the surface treatment agent, and the minimum coverage area of ​​the surface treatment agent can be calculated using the same method as for the submicro copper particles described above.

[0044] Commercially available micro copper particles can be used. Commercially available spherical microparticles include, for example, Cu-HWQ1.5 μm (manufactured by Fukuda Metal Foil & Powder Co., Ltd., volume average particle size 1.5 μm), Cu-HWQ3 μm (manufactured by Fukuda Metal Foil & Powder Co., Ltd., volume average particle size 3 μm), Cu-HWQ5 μm (manufactured by Fukuda Metal Foil & Powder Co., Ltd., volume average particle size 5 μm), Cu-HWQ10 μm (manufactured by Fukuda Metal Foil & Powder Co., Ltd., volume average particle size 10 μm), 1110 (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 3.6 μm), 1100Y (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 1.1 μm), 1200Y (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 2.1 μm), 1300Y (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 3.5 μm), and MA-C02K (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 2.1 μm). volume average particle size 1.8 μm), MA-C025K (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 2.4 μm), MA-C03K (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 3.4 μm), MA-C05K (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 5.8 μm), MA-C05K-2 (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 5.1 μm), MA-C08K-2 (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 8.2 μm), MA-CKU (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 11.1 μm), MA-C04J (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 4.3 μm), MA-C08J (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 8.2 μm), and MA-CJU (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 17.7 μm).

[0045] Commercially available flake-shaped microparticles include, for example, 1100YP (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 1.4 μm), 1200YP (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 3.1 μm), MA-C08JF (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 11.9 μm), MA-C03KP (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 3.5 μm), MA-C05KP (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 5.8 μm), MA-C025KFD (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 4.7 μm), MA-C05KFD (manufactured by Mitsui Mining & Smelting Co., Ltd.), Examples of such fluororesin include 1110F (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 7.3 μm), 1110F (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 3.8 μm), 3L3N (manufactured by Fukuda Metal Foil & Powder Co., Ltd., volume average particle size 6 μm), 2L3N (manufactured by Fukuda Metal Foil & Powder Co., Ltd., volume average particle size 9.9 μm), 4L3N (manufactured by Fukuda Metal Foil & Powder Co., Ltd., volume average particle size 3 μm), C3 (manufactured by Fukuda Metal Foil & Powder Co., Ltd., volume average particle size 37 μm), Cu-HWF-6 (manufactured by Fukuda Metal Foil & Powder Co., Ltd., volume average particle size 6 μm), and ST-Cu-325 (manufactured by Yamaishi Metal Co., Ltd., volume average particle size 30 μm).

[0046] The metal paste may contain submicron copper particles and micron copper particles as metal particles, which can suppress volume shrinkage and sintering shrinkage that accompany drying of the dispersion medium, and facilitate preventing peeling between the joining surfaces of the members and the sintered body of the metal particle-containing layer.

[0047] From the above viewpoint, the metal paste comprises sub-micro copper particles having a volume average particle size of 0.05 μm or more and 0.8 μm or less and spherical micro copper particles having a volume average particle size of 2 μm or more and 50 μm or less, and the sum of the content of the sub-micro copper particles and the content of the micro copper particles is 80 mass % or more or 90 mass % or more based on the total mass of the metal particles, and the content of the sub-micro copper particles may be 30 mass % or more and 90 mass % or less based on the sum of the mass of the sub-micro copper particles and the mass of the micro copper particles.

[0048] The metal paste may contain submicro copper particles, flake-shaped micro copper particles, and spherical micro copper particles from the viewpoints of low-temperature sintering, suppression of volumetric shrinkage in the XY directions (directions parallel to the joining surface), and improvement of the packing of metal particles in the metal particle-containing layer.

[0049] In view of the above, the metal paste comprises submicro copper particles having a volume average particle size of 0.05 μm to 0.8 μm, spherical micro copper particles having a volume average particle size of 2 μm to 50 μm and an aspect ratio of 2 or less, and flaky micro copper particles having an aspect ratio of more than 2, wherein the total content of the submicro copper particles, the spherical micro copper particles, and the flaky micro copper particles is 80% by mass or more or 90% by mass or more based on the total mass of the metal particles, and the content of the submicro copper particles, the spherical micro copper particles, and the flaky micro copper particles may be 20% by mass to 80% by mass, 5% by mass to 50% by mass, and 5% by mass to 50% by mass, respectively, or may be 60% by mass to 80% by mass, 10% by mass to 20% by mass, and 10% by mass to 20% by mass, respectively, based on the total mass of the submicro copper particles, the spherical micro copper particles, and the flaky micro copper particles.

[0050] The metal paste may contain metal particles containing metal elements other than copper (other metal particles). The other metal particles may include, for example, particles of zinc, gold, palladium, silver, nickel, platinum, brass, manganese, tin, antimony, indium, aluminum, vanadium, etc. The other metal particles may have a volume average particle size of 0.01 μm to 10 μm, 0.01 μm to 5 μm, or 0.05 μm to 3 μm.

[0051] When the metal paste contains other metal particles, a sintered body in which multiple types of metals are dissolved or dispersed can be obtained, which improves the mechanical properties of the sintered body, such as yield stress and fatigue strength, and tends to improve connection reliability. Furthermore, by adding multiple types of metal particles, the sintered body of the metal particle-containing layer can have sufficient bonding strength to a predetermined adherend. When the member to be bonded is a semiconductor element, the die shear strength and connection reliability of the semiconductor device can be easily improved.

[0052] When the metal paste contains other metal particles, the content of the other metal particles may be less than 5 mass % or 3 mass % or less based on the total mass of the metal particles, from the viewpoint of obtaining sufficient bonding properties. The other metal particles may not be included. The shape of the other metal particles is not particularly limited.

[0053] The content of inorganic particles other than metal particles in the metal paste may be 30% by mass or less, 20% by mass or less, or 0% by mass based on the total amount of the metal paste.

[0054] [Second fatty acid] Examples of fatty acids having 10 or more carbon atoms include capric acid (decanoic acid), methyl nonanoic acid, ethyl octanoic acid, propyl heptanoic acid, butyl hexanoic acid, undecanoic acid, methyl decanoic acid, ethyl nonanoic acid, propyl octanoic acid, butyl heptanoic acid, lauric acid, methyl undecanoic acid, ethyl decanoic acid, propyl nonanoic acid, butyl octanoic acid, pentyl heptanoic acid, tridecanoic acid, methyl dodecanoic acid, ethyl undecanoic acid, propyl decanoic acid, butyl nonanoic acid, pentyl octanoic acid, myristic acid, methyl tridecanoic acid, ethyl dodecanoic acid, propyl undecanoic acid, butyl decanoic acid, pentyl nonanoic acid, hexyl octanoic acid, pentadecanoic acid, methyl tetradecanoic acid, ethyl tridecanoic acid, propyl dodecanoic acid, butyl undecanoic acid, pentyl decanoic acid, hexyl nonanoic acid, palmitic acid, methyl pentadecanoic acid, ethyl ... Saturated fatty acids such as tridecanoic acid, propyl tridecanoic acid, butyl dodecanoic acid, pentyl undecanoic acid, hexyl decanoic acid, heptyl nonanoic acid, heptadecanoic acid, octadecanoic acid (stearic acid), methyl cyclohexane carboxylic acid, ethyl cyclohexane carboxylic acid, propyl cyclohexane carboxylic acid, butyl cyclohexane carboxylic acid, pentyl cyclohexane carboxylic acid, hexyl cyclohexane carboxylic acid, heptyl cyclohexane carboxylic acid, octyl cyclohexane carboxylic acid, and nonyl cyclohexane carboxylic acid; and unsaturated fatty acids such as octenoic acid, nonenoic acid, methylnonenoic acid, decenoic acid, undecenoic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, myristoleic acid, pentadecenoic acid, hexadecenoic acid, palmitoleic acid, sapienic acid, oleic acid, vaccenic acid, linoleic acid, linolenic acid, and linolenic acid.

[0055] The number of carbon atoms of the second fatty acid is preferably 12 or more, more preferably 14 or more, and even more preferably 16 or more, since this further improves the tack strength. The number of carbon atoms of the second fatty acid may be 20 or less, 18 or less, or 16 or less, from the viewpoint of suppressing inhibition of copper sintering by residual components.

[0056] The second fatty acid may be used alone or in combination of two or more.

[0057] The content of the second fatty acid in the metal paste may be 0.5% by mass or more, 1% by mass or more, 5% by mass or less, 3% by mass or less, 0.5% by mass or more and 5% by mass or less, or 1% by mass or more and 3% by mass or less, based on the total mass of the metal particles. If the content of the second fatty acid is within the above range, flexibility can be imparted to the metal paste, while preventing copper sintering from being inhibited by residual components.

[0058] From the same viewpoint as above, the content of the second fatty acid in the metal paste may be 10 parts by mass or more and 100 parts by mass or less, or 20 parts by mass or more and 60 parts by mass or less, per 100 parts by mass of the polyhydric alcohol blended as a reducing agent.

[0059] [Reducing agent] Examples of polyhydric alcohols that can be incorporated as reducing agents include pentaethylene glycol, hexaethylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, polyethylene glycols such as polyethylene glycol 200, polyethylene glycol 300, and polyethylene glycol 400, polypropylene glycols such as polypropylene glycol 200, polypropylene glycol 300, polypropylene glycol 400, polypropylene glycol 700, and polypropylene glycol 4000, polyethylene glycol monooleate, polyethylene glycol monostearate, polyethylene glycol monolaurate, polyoxyethylene sorbitan monolaurate, and polyoxyethylene polyoxypropylene glycol.

[0060] The polyhydric alcohol may be polyethylene glycol, which functions as a highly polar solvent, exhibits a reducing effect at the heating temperature of the metal paste, and can easily ensure sufficient sinterability. Examples of polyethylene glycol include polyethylene glycol 200, polyethylene glycol 300, and polyethylene glycol 400.

[0061] The polyhydric alcohols can be used alone or in combination of two or more.

[0062] The content of polyhydric alcohol blended as a reducing agent in the metal paste may be 5 to 10 parts by mass, or 3 to 5 parts by mass, relative to 100 parts by mass of the total mass of the metal particles, from the viewpoint of suppressing poor sintering and ensuring bonding strength.

[0063] [Polyether compounds] The polyether-based compound is amphiphilic, and examples of the polyether-based compound include polyoxyalkylene alkyl ethers.

[0064] Examples of polyoxyalkylene alkyl ethers include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, polyoxyethylene behenyl ether, polyoxyethylene 2-ethylhexyl ether, and polyoxyethylene isodecyl ether. The polyoxyalkylene alkyl ether is preferably polyoxyethylene oleyl ether, from the viewpoint of preventing copper sintering from being inhibited by residual components.

[0065] The HLB value of the polyether compound may be 10-16, 11-15, or 12-14.

[0066] The polyether compounds can be used alone or in combination of two or more.

[0067] The content of the polyether compound in the metal paste may be 0.3 mass% or more, 0.5 mass% or more, 1.0 mass% or more, 3.0 mass% or less, 2.0 mass% or less, 1.0 mass% or less, or even 0.3 mass% to 1.0 mass% or less, based on the total mass of the metal particles. If the content of the polyether compound is within the above range, it is possible to impart flexibility to the metal paste while suppressing the occurrence of copper sintering inhibition due to residual components.

[0068] From the same viewpoint as above, the content of the polyether-based compound in the metal paste may be 6 parts by mass or more and 60 parts by mass or less, 10 parts by mass or more and 40 parts by mass or less, or 15 parts by mass or more and 20 parts by mass or less, relative to 100 parts by mass of the polyhydric alcohol blended as a reducing agent.

[0069] [Liquid dispersion medium] Examples of liquid dispersion media include monohydric and polyhydric alcohols such as pentanol, hexanol, heptanol, octanol, decanol, dihydroterpineol, terpineol, isobornylcyclohexanol (MTPH), 1,5-pentanediol, ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, triethylene glycol, tetraethylene glycol, α-terpineol (α-terpineol), dihydroterpineol (dihydroterpineol), and geraniol; ethylene glycol butyl ether, ethylene glycol phenyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol butyl ether, diethylene glycol isobutyl ether, diethylene glycol hexyl ether, triethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol butyl methyl ether, diethylene glycol isopropyl methyl ether, and triethylene glycol di Ethers such as methyl ether, triethylene glycol butyl methyl ether, propylene glycol propyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, dipropylene glycol dimethyl ether, tripropylene glycol methyl ether, and tripropylene glycol dimethyl ether; esters such as ethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, dipropylene glycol methyl ether acetate (DPMA), ethyl lactate, butyl lactate, γ-butyrolactone, and propylene carbonate; acid amides such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide; aliphatic hydrocarbons such as cyclohexanone, octane, nonane, decane, and undecane; aromatic hydrocarbons such as benzene, toluene, xylene, and 1-methylnaphthalene; and mercaptans having an alkyl group having 1 to 18 carbon atoms.Examples of mercaptans having a cycloalkyl group having 5 to 7 carbon atoms include: mercaptans having an alkyl group having 1 to 18 carbon atoms include ethyl mercaptan, n-propyl mercaptan, i-propyl mercaptan, n-butyl mercaptan, i-butyl mercaptan, t-butyl mercaptan, pentyl mercaptan, hexyl mercaptan, and dodecyl mercaptan; and examples of mercaptans having a cycloalkyl group having 5 to 7 carbon atoms include cyclopentyl mercaptan, cyclohexyl mercaptan, and cycloheptyl mercaptan.

[0070] The content of the liquid dispersion medium in the metal paste may be 2% by mass or more, or 5% by mass or more, or 50% by mass or less, 30% by mass or less, or 20% by mass or less, based on the total mass of the metal paste. For example, the content of the liquid dispersion medium may be 2 to 50% by mass, 5 to 30% by mass, or 5 to 20% by mass, based on the total mass of the metal paste. Furthermore, the content of the liquid dispersion medium may be 5 to 50 parts by mass, 5 to 40 parts by mass, or 7 to 35 parts by mass, based on 100 parts by mass of the total mass of the metal particles contained in the metal paste. If the content of the liquid dispersion medium is within the above range, the viscosity of the metal paste can be adjusted to a more appropriate level, and uneven particle dispersion due to low viscosity and sintering inhibition due to residue during sintering can be suppressed.

[0071] In this embodiment, two or more liquid dispersion media can be used in combination.

[0072] The metal paste may contain additives such as wetting improvers (e.g., nonionic surfactants, fluorine-based surfactants, etc.); surface tension adjusters; dispersants (e.g., alkylamines, alkylcarboxylic acids, etc.); antifoaming agents (e.g., silicone oils, etc.); and ion trapping agents (e.g., inorganic ion exchangers, etc.). The content of the additives may be adjusted appropriately within a range that does not impair the effects of the present invention. Furthermore, the metal paste may have a total content of nonmetallic inorganic particles (e.g., glass particles, etc.) of 1% by mass or less, or 0.1% by mass or less, based on the total amount of metal particles. Furthermore, the metal paste may be free of nonmetallic inorganic particles.

[0073] The viscosity of the metal paste is not particularly limited, and when it is applied by a method such as printing, it may be adjusted to a viscosity suitable for the application method. The Casson viscosity of the metal paste at 25°C may be 1 Pa·s or more or 100 Pa·s or more, or 10 Pa·s or less or 50 Pa·s or less.

[0074] [Metal paste manufacturing method] The metal paste can be prepared by mixing metal particles (e.g., submicro copper particles and micro copper particles) having the first fatty acid on their surface, the second fatty acid, the reducing agent (polyhydric alcohol), the polyether compound, the liquid dispersion medium, and, if necessary, other metal particles and optional additives. After mixing the components, a stirring treatment or a dispersion treatment may be performed. The maximum particle size of the metal paste dispersion may be adjusted by classification.

[0075] The method may include the step of surface treating the metal particles with a first fatty acid.

[0076] The stirring treatment can be carried out using a stirrer, such as an Ishikawa stirrer, a Silverson stirrer, a cavitation stirrer, a rotation-revolution type stirrer, an ultra-thin film high-speed rotary disperser, an ultrasonic disperser, a Raikai mixer, a twin-screw kneader, a bead mill, a ball mill, a three-roll mill, a homomixer, a planetary mixer, an ultra-high pressure type disperser, a thin layer shear disperser, or a dispersizer.

[0077] Examples of the dispersion treatment include a thin layer shear disperser, a dispersizer, a bead mill, an ultrasonic homogenizer, a high shear mixer, a narrow gap three-roll mill, a wet ultra-atomizer, a supersonic jet mill, and an ultra-high pressure homogenizer.

[0078] The classification can be carried out by, for example, filtration, natural sedimentation, or centrifugation. Examples of filters for filtration include a water comb, a metal mesh, a metal filter, and a nylon mesh.

[0079] Methods that can be used to apply the metal paste onto the first member include inkjet printing, super inkjet printing, screen printing, transfer printing, offset printing, jet printing, dispenser, jet dispenser, needle dispenser, comma coater, slit coater, die coater, gravure coater, slit coat, letterpress printing, intaglio printing, gravure printing, stencil printing, soft lithography, bar coat, applicator, particle deposition method, spray coater, spin coater, dip coater, and electroplating.

[0080] The thickness of the coating film may be 1 μm or more, 5 μm or more, 10 μm or more, or 20 μm or more. The thickness of the coating film may be 3000 μm or less, 1000 μm or less, 500 μm or less, 300 μm or less, 250 μm or less, 200 μm or less, or 150 μm or less.

[0081] (2nd process) In the second step, the coating film is dried to form a metal particle-containing layer. Methods for drying the coating film include heat drying and reduced pressure drying.

[0082] The gas atmosphere during heat drying or reduced pressure drying may be air, an oxygen-free atmosphere such as nitrogen or a rare gas, or a reducing atmosphere such as hydrogen or formic acid.

[0083] For heat drying or reduced pressure drying, for example, a hot plate, a warm air dryer, a warm air heating furnace, a nitrogen dryer, an infrared dryer, an infrared heating furnace, a far-infrared heating furnace, a microwave heating device, a laser heating device, an electromagnetic heating device, a heater heating device, a steam heating furnace, a hot plate press device, etc. The drying temperature and time may be appropriately adjusted depending on the type and amount of the dispersion medium used.

[0084] In the second step, the drying time of the coating film may be 30 minutes or more, 60 minutes or more, or 90 minutes or more. By including a combination of a second fatty acid having 10 or more carbon atoms and a polyether-based compound in the metal paste, the second fatty acid and the polyether-based compound can be coordinated in multiple layers without being detached from the surface of the metal particles, even when the drying time of the coating film is long. As a result, the tack strength is improved even when the drying time of the coating film is within the above numerical range. The drying time of the coating film may be 30 minutes or less, 20 minutes or less, or 10 minutes or less.

[0085] (3rd step) In the third step, a second member is placed on the metal particle-containing layer to obtain a laminate.

[0086] Examples of methods for placing the second member on the metal particle-containing layer include using a chip mounter, a flip chip bonder, and a positioning jig made of carbon or ceramics.

[0087] From the viewpoint of improving tack strength, the second member may be placed on the metal particle-containing layer that has been heated to 90° C. or higher. The heating temperature may be equal to or higher than the melting point of the second fatty acid, and from the viewpoint of suppressing volatilization of the second fatty acid and suppressing oxidation of the metal particles (e.g., copper particles), the heating temperature may be 150° C. or lower, or 120° C. or lower.

[0088] The metal particle-containing layer can be heated using, for example, a hot plate, a flip-chip bonder, etc. A flip-chip bonder can heat the substrate side and the member side separately.

[0089] The obtained laminate can be transported to a sintering furnace or the like to carry out the fourth step. Examples of transporting means include manual transport, an automatic conveyor, a transport machine, an automatic cart, and a robot arm. Since the second member of the laminate is sufficiently temporarily fixed by the metal particle-containing layer having excellent tackiness, the second member is less likely to fall off during the transport.

[0090] (4th step) In the fourth step, the metal particle-containing layer of the laminate can be sintered by heat treatment in an oxygen-free atmosphere. The oxygen-free atmosphere may be an atmosphere that does not contain hydrogen or has a hydrogen concentration of 10% or less. Note that the oxygen-free atmosphere refers to an atmosphere with an oxygen concentration of 1% by volume or less, and the oxygen concentration may be 0.1% by volume or less, 0.01% by volume or less, or 0.001% by volume or less.

[0091] The heat treatment can be performed using a heating device having a pressure bonding mechanism, such as a hot plate, a warm air dryer, a warm air heating furnace, a nitrogen dryer, an infrared dryer, an infrared heating furnace, a far-infrared heating furnace, a microwave heating device, a laser heating device, an electromagnetic heating device, a heater heating device, or a steam heating furnace.

[0092] The hydrogen-free atmosphere may be a non-oxidizing gas such as nitrogen, a rare gas, a heat-resistant organic gas, water vapor, or a mixture thereof, or may be under vacuum.

[0093] The gas atmosphere during sintering may be a reducing atmosphere. Examples of reducing atmospheres include nitrogen containing formic acid gas, a rare gas containing formic acid gas, and a non-oxidizing gas containing 10% or less hydrogen. The gas atmosphere during sintering may also be forming gas (nitrogen containing hydrogen at or below the lower explosion limit (e.g., 5% or less or 3% or less)) or low-molecular-weight alcohol (e.g., methanol, ethanol) vapor.

[0094] From the viewpoint of reducing thermal damage to the members to be joined and improving yield, the maximum temperature reached during the heat treatment may be 200°C or higher and 450°C or lower, 230°C or higher and 400°C or lower, 240°C or higher and 350°C or lower, or 250°C or higher and 300°C or lower.

[0095] The maximum temperature holding time may be 1 minute or more and 60 minutes or less, or 1 minute or more and less than 40 minutes, or 1 minute or more and less than 30 minutes, from the viewpoint of volatilizing all of the dispersion medium and improving the yield. In particular, when the maximum temperature to be reached is 250°C or higher, sintering tends to proceed sufficiently with a holding time of 10 minutes or less.

[0096] Through the fourth step, a bonded body including the first member, the second member, and the sintered body of the metal particle-containing layer bonding them together can be obtained.

[0097] From the viewpoint of sufficiently bonding the first member and the second member, the die shear strength of the bonded body may be 40 MPa or more, 50 MPa or more, 60 MPa or more, or 30 MPa or more. The die shear strength can be measured using a universal bond tester (4000 series, manufactured by DAGE) or the like.

[0098] In the bonded structure, at least one of the first and second members may be a semiconductor element. Examples of semiconductor elements include power modules including diodes, rectifiers, thyristors, MOS gate drivers, power switches, power MOSFETs, IGBTs, Schottky diodes, and fast recovery diodes, as well as transmitters, amplifiers, and LED modules. In such cases, the bonded structure becomes a semiconductor device. The resulting semiconductor device can have sufficient die shear strength and connection reliability.

[0099] Examples of semiconductor devices include power modules consisting of diodes, rectifiers, thyristors, MOS gate drivers, power switches, power MOSFETs, IGBTs, Schottky diodes, fast recovery diodes, etc., transmitters, amplifiers, high-brightness LED modules, semiconductor laser modules, logic, sensors, etc.

[0100] The present invention can provide a metal paste-applied member comprising a member and a coating film of the above-described metal paste provided on the member. This metal paste-applied member can be obtained by the above-described step 1. The metal paste-applied member of this embodiment can be converted into a member with a metal particle-containing layer having tackiness by performing the above-described step 2 at a predetermined timing.

[0101] <zygote> The bonded body of this embodiment includes a first member, a second member, and a bonding part that bonds them together, and the bonding part includes the sintered body of the bonding metal paste of this embodiment described above. The bonded body of this embodiment can be obtained by the method described above. [Example]

[0102] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to the following examples.

[0103] [Preparation of metal particles having a first fatty acid on the surface] (Submicron copper particles A) Sub-micro copper particles having a volume average particle size of 0.21 μm and a treatment amount of lauric acid of 10 mass % were prepared as sub-micro copper particles A having lauric acid on the surface.

[0104] (Micro copper particles A) Flake-shaped micro copper particles having a volume average particle size of 7.3 μm and a treatment amount of lauric acid of 10 mass % were prepared as micro copper particles A having lauric acid on the surface.

[0105] (Micro copper particles B) Spherical micro copper particles having a volume average particle size of 1.7 μm and a treatment amount of lauric acid of 10 mass % were prepared as micro copper particles B having lauric acid on the surface.

[0106] [Preparation of metal paste] The metal pastes were prepared according to the procedure below in the amounts (parts by mass) shown in Table 1. The amounts shown in the table represent the proportions (parts by mass) of each component when the total mass of the metal paste is 100 parts by mass.

[0107] At room temperature of 25°C and humidity of 60%, 7 g of dihydroterpineol (manufactured by Nippon Terpene Chemical Co., Ltd.) as a dispersion medium was mixed with 65.10 g of submicron copper particles A, 13.95 g of micron copper particles A, and 13.950 g of micron copper particles B, and the mixture was stirred at 300 rpm for 30 minutes using a planetary mixer (manufactured by Primix Co., Ltd.). The resulting mixture was dispersed once using a dispersizer (manufactured by Shinto Kogyo Co., Ltd.) at a gap of 50 μm and a rotation speed of 12,000 rpm to obtain a 93% by mass dispersion.

[0108] 87.1 g of the 93 mass% dispersion obtained above was mixed with 6.4 g of dihydroterpineol as the remainder of the dispersion medium, 5.0 g of polyethylene glycol 200 (hereinafter abbreviated as PEG200) (manufactured by NOF Corporation) as a reducing agent, 1.0 g of decanoic acid (manufactured by New Japan Chemical Co., Ltd.) as a second fatty acid, and 0.5 g of polyoxyethylene oleyl ether (manufactured by NOF Corporation, Nonion E212) as a polyether compound, and the mixture was stirred at 2000 rpm under reduced pressure for 3 minutes in a planetary mixer (Thinky, Awatori Rentaro ARE-310) to obtain a metal paste with a metal particle content of 81 mass%.

[0109] Examples 2 to 4 A metal paste was obtained in the same manner as in Example 1, except that the second fatty acid was changed to a compound shown in Table 1 instead of decanoic acid.

[0110] (Comparative Example 1) A metal paste was obtained in the same manner as in Example 1, except that the second fatty acid and polyether compound were not added, and the amount of dihydroterpineol (manufactured by Nippon Terpene Chemical Co., Ltd.) added as the remainder of the dispersion medium was changed to 14.0 g.

[0111] The tack strength of the metal pastes of the examples and comparative examples was evaluated by the following method.

[0112] (1) Tack strength The metal paste obtained above was printed on a copper plate (30 mm × 30 mm × 2 mm thick) to form a coating film measuring 3.0 mm × 3.0 mm × 0.1 mm. The metal paste coating was then dried for 30 minutes on a hot plate heated to 90 ° C., forming a metal particle-containing layer in which the dispersant dihydroterpineol had evaporated. A dummy chip (3 mm × 3 mm × 0.4 mm thick, with a copper layer as the bonding surface (bonding surface)) was mounted on the formed metal particle-containing layer using a tabletop hot mount device (TRESKY, T-3000-FC3) at 1.0 MPa for 3.0 seconds to obtain a laminate. At this time, the dummy chip was mounted while the metal particle-containing layer was heated on a heater heated to 90 ° C.

[0113] The tack strength of the obtained laminate was measured using a die shear tester (STELLAR4000, manufactured by Nordson Corporation) according to the following procedure. As shown in Figure 1, a tool 40 was pressed horizontally against a dummy chip 30 mounted on a metal particle-containing layer 20 provided on a copper substrate 10 at a measurement speed of 500 μm / s and a measurement height H of 0.2 mm, and the shear load was measured. The maximum shear load (N) was calculated as a function of the chip area (mm 2 The value obtained by dividing the measured value by the coefficient of friction coefficient was defined as the tack strength (kPa), and the average value of the measured values ​​for eight laminates was taken as the tack strength.

[0114] [Table 1] [Explanation of symbols]

[0115] 10...copper substrate, 20...metal particle-containing layer, 30...dummy chip, 40...tool.

Claims

1. A method for producing a metal paste for joining, comprising a step of preparing a dispersion by mixing at least metal particles having a first fatty acid having 10 or more carbon atoms on their surfaces, a second fatty acid having 10 or more carbon atoms, a reducing agent which is a polyhydric alcohol, and a polyether-based compound.

2. The method for producing a metal bonding paste according to claim 1 , wherein the second fatty acid is stearic acid.

3. The method for producing a metal bonding paste according to claim 1 , wherein the polyether compound is a polyoxyalkylene alkyl ether.

4. The method for producing a metal bonding paste according to claim 1 , wherein the polyhydric alcohol is polyethylene glycol.

5. A metal joining paste comprising metal particles having a first fatty acid having 10 or more carbon atoms on their surface, a second fatty acid having 10 or more carbon atoms, a reducing agent which is a polyhydric alcohol, and a polyoxyalkylene alkyl ether.

6. The metal bonding paste according to claim 5 , wherein the second fatty acid is stearic acid.

7. The metal bonding paste according to claim 5 , wherein the polyhydric alcohol is polyethylene glycol.

8. A joined body including a first member, a second member, and a joining portion that joins the first member and the second member, A joined body, wherein the joint portion comprises a sintered body of the joining metal paste according to any one of claims 5 to 7.

9. A first step of applying a metal bonding paste obtained by the method according to any one of claims 1 to 4 onto a first member to form a coating film of the metal bonding paste; a second step of drying the coating to form a metal particle-containing layer; a third step of disposing a second member on the metal particle-containing layer to obtain a laminate; a fourth step of sintering the metal particle-containing layer of the laminate; A method for manufacturing a bonded body, comprising:

10. 10. The method for producing a joined body according to claim 9, wherein in the third step, a second member is placed on the metal particle-containing layer that has been heated to 90°C or higher.

11. A first step of applying the bonding metal paste according to any one of claims 5 to 7 onto a first member to form a coating film of the bonding metal paste; a second step of drying the coating to form a metal particle-containing layer; a third step of disposing a second member on the metal particle-containing layer to obtain a laminate; a fourth step of sintering the metal particle-containing layer of the laminate; A method for manufacturing a bonded body, comprising:

12. The method for producing a joined body according to claim 11 , wherein in the third step, a second member is placed on the metal particle-containing layer that has been heated to 90° C. or higher.

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