Method for producing joined body, joined body, metal paste for joining, and method for producing same

Abstract

This method for producing a metal paste for joining includes a step in which at least metal particles that each have a first fatty acid having 10 or more carbon atoms on the surface, a second fatty acid having 18 or less carbon atoms, and a reducing agent that is a polyhydric alcohol are mixed with each other. This method for producing a joined body includes: a first step for forming a coating film of a metal paste for joining on a first member by applying the metal paste for joining, which is obtained by the above-described method; a second step for forming a metal particle-containing layer by drying the coating film; a third step for obtaining a laminate by disposing a second member on the metal particle-containing layer; and a fourth step for sintering the metal particle-containing layer of the laminate.

Description

Method for manufacturing a bonded body, bonded body, metal paste for bonding, and method for manufacturing the same

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

[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 problems with connection reliability and also have insufficient thermal conductivity (30 Wm －１ K －１ ) and therefore alternative materials are needed.

[0003] As a joining method using an alternative material, 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, is likely to achieve connection reliability at high temperatures, and can 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).

[0004] Patent No. 5006081

[0005] T. Morita, Y. Yasuda: Materials Transactions, 56(6), 2015, 878-882

[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 bonded 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.

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

[15] .

[0010] [1] A method for producing a metal paste for bonding, comprising a step of mixing at least metal particles having a first fatty acid having 10 or more carbon atoms on their surfaces, a second fatty acid having 18 or less carbon atoms, and a reducing agent that is a polyhydric alcohol. [2] The method for producing a metal paste for bonding according to [1], wherein the second fatty acid is at least one fatty acid selected from the group consisting of decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, and isostearic acid. [3] The method for producing a metal paste for bonding according to [1] or [2], wherein the second fatty acid is decanoic acid. [4] The method for producing a metal paste for bonding according to [1] or [2], wherein the second fatty acid is isostearic acid. [5] The method for producing a metal paste for bonding according to any one of [1] to [4], wherein the polyhydric alcohol is polyethylene glycol. [6] A metal paste for bonding, comprising metal particles having a first fatty acid having 10 or more carbon atoms on their surfaces, a second fatty acid having 18 or less carbon atoms, and a reducing agent that is a polyhydric alcohol. [7] The metal paste for joining according to [6], wherein the second fatty acid is at least one fatty acid selected from the group consisting of decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, and isostearic acid. [8] The metal paste for joining according to [6] or [7], wherein the second fatty acid is decanoic acid. [9] The metal paste for joining according to [6] or [7], wherein the second fatty acid is isostearic acid.

[10] The metal paste for joining according to any one of [6] to [9], wherein the polyhydric alcohol is polyethylene glycol.

[11] A joined body comprising a first member, a second member, and a joining part joining them, wherein the joining part comprises a sintered body of the metal paste for joining according to any one of [6] to

[10] .

[12] A method for producing a joined body, comprising: a first step of applying a metal bonding paste obtained by the method according to any one of [1] to [5] onto a first member to form a coating film of the metal bonding paste; a second step of drying the coating film to form a metal particle-containing layer; a third step of arranging a second member on the metal particle-containing layer to obtain a laminate; and a fourth step of sintering the metal particle-containing layer of the laminate.

[13] A method for producing a bonded body according to

[12] , 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.

[14] A method for producing a bonded body, comprising: a first step of applying the bonding metal paste according to any one of [6] to

[10] onto a first member to form a coating film of the bonding metal paste; a second step of drying the coating film to form a metal particle-containing layer; a third step of placing a second member on the metal particle-containing layer to obtain a laminate; and a fourth step of sintering the metal particle-containing layer of the laminate.

[15] A method for producing a bonded body according to

[14] , 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.

[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.

[0012] FIG. 2 is a schematic diagram for explaining a method for measuring tack strength.

[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 for manufacturing bonded body> The method for manufacturing a bonded body of the present embodiment includes a first step of forming, on a first member, 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 18 or less carbon atoms, and a reducing agent which is a polyhydric alcohol; a second step of drying the coating film to form a metal particle-containing layer; a third step of arranging a second member 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 according to the present 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, the second fatty acid having 18 or fewer carbon atoms is coordinated in multiple layers on the surfaces of the metal particles, buffering the hydrophobicity, which is thought to improve the wettability between the metal particles and the polyhydric alcohol. The inventors speculate that this results in the formation of a liquid film of the polyhydric alcohol on the surfaces of the metal particles, making the metal particle-containing layer more susceptible to plastic deformation, thereby improving the tack strength.

[0017] 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; lead frames, metal plate-attached ceramic substrates (e.g., DBCs), and substrates for mounting semiconductor elements such as LED packages; power supply members such as copper ribbons, metal blocks, and terminals; heat sinks; and water-cooled plates.

[0018] The first member and the second member 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 alone 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 the alloy 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.

[0019] (Step 1) The metal paste used in this embodiment may contain metal particles having a first fatty acid having 10 or more carbon atoms on their surfaces, a second fatty acid having 18 or less carbon atoms, a reducing agent which is a polyhydric alcohol, and a liquid dispersion medium.

[0020] [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 Examples of saturated fatty acids include octadecanoic 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.

[0021] The first fatty acid may be a fatty acid having 10 to 18 carbon atoms from the viewpoint of dispersion stability of the metal particles and prevention of oxidation, or may be lauric acid or decanoic acid from the viewpoint of low-temperature decomposition property and hence low-temperature sintering property.

[0022] The first fatty acid may be used alone or in combination of two or more.

[0023] [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 made by combining two or more of these.

[0024] The metal particles may be sinterable in a temperature range of 200°C or higher and 300°C or lower.

[0025] The metal paste may contain copper particles as the 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 the material under mild conditions of low temperature (300°C or less) and low pressure (10 MPa or less).

[0026] 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.

[0027] 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.

[0028] In this specification, the volume average particle size refers to the 50% volume average particle size. When determining the volume average particle size of metal particles, the metal particles to be used as raw materials, or dried copper particles obtained by removing volatile components from a metal paste, are dispersed in a dispersion medium using a dispersant, and the resulting dispersion medium is measured using a light scattering particle size distribution analyzer (for example, a Shimadzu nanoparticle size distribution analyzer (SALD-7500nano, manufactured by Shimadzu Corporation)). When using a light scattering particle size distribution analyzer, hexane, toluene, α-terpineol, 4-methyl-1,3-dioxolan-2-one, water, or the like can be used as the dispersion medium.

[0029] 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, based on the total mass of the metal particles, 20% by mass or more, 30% by mass or more, 35% by mass or more, 40% by mass or more, 80% by mass or less, 20% by mass or more, 30% by mass or more, 35% by mass or more, 85% by mass or less, 40% by mass or more, 80% by mass or less, or 60% by mass or more, 80% by mass or less. 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.

[0030] 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. If 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. If the content of the submicron copper particles is 90% by mass or less, the volume shrinkage in the in-plane direction (XY direction) of the sintered layer when sintered without pressure or under 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.

[0031] 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.

[0032] 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.

[0033] The sub-micron copper particles may be treated with a surface treatment agent comprising the first fatty acid described above.

[0034] The amount of the surface treatment agent to be used for the treatment may be an amount that allows one to three molecular layers to adhere to the surface of the submicron copper particles. This amount depends on the number of molecular layers (n) attached to the surface of the submicron copper particles, 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 / piece) and Avogadro's number (N Ａ ) (6.02 x 10 ２３ Specifically, the amount of surface treatment agent can be calculated from 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%.

[0035] The specific surface area of ​​the submicron copper particles can be calculated by measuring the dried submicron copper particles using the BET specific surface area measurement method. When the surface treatment agent is a linear saturated fatty acid, the minimum coverage area of ​​the surface treatment agent is 2.05 × 10 －１９ m ２ / 1 molecule. In the case of other surface treatment agents, it can be measured, for example, by calculation from a molecular model or by the method described in "Chemistry and Education" (Kamieda Katsuhiro, Inafuku Sumio, Mori Iwao, 40(2), 1992, pp. 114-117). An example of a method for quantifying the surface treatment agent is shown below. The surface treatment agent can be identified by a thermal desorption gas / gas chromatograph mass spectrometer for 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 method. 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.

[0036] The amount of the surface treatment agent may be 0.1 to 15% by weight, 1 to 15% by weight, 5 to 15% by weight, or 8 to 12% by weight based on the weight of the submicron copper particles having the surface treatment agent.

[0037] Commercially available submicron copper particles can be used, such as CH-0200 (manufactured by Mitsui Mining & Smelting Co., Ltd.) and Tn-Cu100 (manufactured by Taiyo Nippon Sanso Co., Ltd.).

[0038] As the micro copper particles, copper particles having a particle size of 2 μm to 50 μm can be used, 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 pressure 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.

[0039] The shape of the micro copper particles is preferably flake-shaped. By using flake-shaped 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-shaped 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.

[0040] 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.

[0041] There is no particular limitation on whether or not the micro copper particles are treated with a surface treatment agent. However, 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.

[0042] The amount of the surface treatment agent may be an amount equivalent to one molecular layer or more on the particle surface. The amount of such a 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 to 15 mass%, 1 to 15 mass%, 5 to 15 mass%, or 8 to 12 mass% based on the mass of the micro copper particles having 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 in the case of the submicro copper particles described above.

[0043] Commercially available micro copper particles can be used. Examples of commercially available spherical micro particles include Cu-HWQ series (manufactured by Fukuda Metal Foil & Powder Co., Ltd.), 1100Y (manufactured by Mitsui Mining & Smelting Co., Ltd.), 1200Y (manufactured by Mitsui Mining & Smelting Co., Ltd.), 1300Y (manufactured by Mitsui Mining & Smelting Co., Ltd.), MA-C08J (manufactured by Mitsui Mining & Smelting Co., Ltd.), and MA-CJU (manufactured by Mitsui Mining & Smelting Co., Ltd.).

[0044] Examples of commercially available flake-shaped microparticles include 1100YP (manufactured by Mitsui Mining & Smelting Co., Ltd.), 1200YP (manufactured by Mitsui Mining & Smelting Co., Ltd.), and 3L3N (manufactured by Fukuda Metal Foil & Powder Co., Ltd.).

[0045] 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.

[0046] 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.

[0047] In order to improve sinterability, the metal paste may contain spherical submicro copper particles and spherical micro copper particles as metal particles, in which the mass ratio of the spherical submicro copper particles to the spherical micro copper particles may be 30:70 to 90:10, or 40:60 to 80:20.

[0048] When the metal paste contains spherical submicro copper particles and spherical micro copper particles as the metal particles, the volume average particle size of the submicro copper particles is preferably 0.1 μm to 0.8 μm, more preferably 0.1 μm to 0.6 μm, and even more preferably 0.1 μm to 0.5 μm, and the volume average particle size of the micro copper particles is preferably 2 μm to 50 μm, more preferably 2 μm to 20 μm, more preferably 2 μm to 15 μm, and even more preferably 2 μm to 10 μm.

[0049] To prevent cracking after drying of the metal paste, the metal paste may contain spherical submicro copper particles and flaky micro copper particles as metal particles, in which the mass ratio of the spherical submicro copper particles to the flaky micro copper particles may be 30:70 to 90:10, or 40:60 to 80:20.

[0050] The metal paste may contain submicro copper particles, flaky micro copper particles, and spherical micro copper particles from the viewpoints of low-temperature sintering properties, suppression of volumetric shrinkage in the XY directions (directions parallel to the joining surface), and improving the packing of metal particles in the metal particle-containing layer.

[0051] From the above viewpoint, 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.

[0052] 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 or more and 10 μm or less, 0.01 μm or more and 5 μm or less, or 0.05 μm or more and 3 μm or less.

[0053] 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.

[0054] When the metal paste contains other metal particles, the content of the other metal particles may be less than 5 mass % or may be 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.

[0055] 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.

[0056] [Second Fatty Acid] Examples of fatty acids having 18 or less carbon atoms include acetic acid, propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, caprylic acid (octanoic 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, propyloct ... Butanoic 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, butyric acid Saturated fatty acids such as undecanoic 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 (stearic acid), isostearic 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.

[0057] The second fatty acid may be a fatty acid having 8 to 18 carbon atoms from the viewpoint of affinity with the reducing agent, or may be at least one fatty acid selected from the group consisting of decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, and isostearic acid from the viewpoint of reducing residue after the drying step.

[0058] The second fatty acid may be used alone or in combination of two or more.

[0059] 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 inhibition due to residual components.

[0060] 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.

[0061] [Reducing Agent] Examples of polyhydric alcohols that can be used 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, polyoxyethylene polyoxypropylene glycol, bis(2-hydroxyethyl)iminotris(hydroxymethyl)methane, 2-amino-2-(hydroxymethyl)-1,3-propanediol, and 1,3-bis(tris(hydroxymethyl)methylamino)propane.

[0062] The polyhydric alcohol may be polyethylene glycol, or may be polyethylene glycol 200, polyethylene glycol 300, or polyethylene glycol 400, from the viewpoint that it functions as a highly polar solvent, can exhibit a reducing effect at the heating temperature of the metal paste, and can easily ensure sufficient sinterability.

[0063] The polyhydric alcohols can be used alone or in combination of two or more.

[0064] The content of the 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.

[0065] [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, and diethylene glycol isopropyl methyl ether. ethers such as ethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, dipropylene glycol dimethyl ether, tripropylene glycol methyl ether, 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;Examples of mercaptans having an alkyl group having 1 to 18 carbon atoms include mercaptans having a cycloalkyl group having 5 to 7 carbon atoms. Examples of 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. Examples of mercaptans having a cycloalkyl group having 5 to 7 carbon atoms include cyclopentyl mercaptan, cyclohexyl mercaptan, and cycloheptyl mercaptan.

[0066] 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 metal paste 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 dispersion of the metal particles due to low viscosity and sintering inhibition due to residue during sintering can be suppressed.

[0067] In this embodiment, two or more liquid dispersion media can be used in combination.

[0068] 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 can 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.

[0069] 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, and may be 10 Pa s or less or 50 Pa s or less.

[0070] [Method for producing metal paste] 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 liquid dispersion medium, and, if necessary, other metal particles and any 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 a classification operation.

[0071] The method may include the step of surface treating the metal particles with a first fatty acid.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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, a dispenser, a jet dispenser, a needle dispenser, a comma coater, a slit coater, a die coater, a gravure coater, a slit coat, letterpress printing, intaglio printing, gravure printing, stencil printing, soft lithography, a bar coater, an applicator, a particle deposition method, a spray coater, a spin coater, a dip coater, and electrodeposition coating.

[0076] 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.

[0077] (Second Step) 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 vacuum drying.

[0078] 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.

[0079] 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.

[0080] (Third Step) In the third step, a second member is disposed on the metal particle-containing layer to obtain a laminate.

[0081] 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 carbon or ceramic positioning jig.

[0082] 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.

[0083] 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.

[0084] The obtained laminate can be transported to a sintering furnace or the like for carrying out the fourth step. Examples of transporting means include manual transport, an automatic conveyor, a transport machine, an automatic cart, a robot arm, etc. In the laminate, the second member is sufficiently temporarily fixed by the metal particle-containing layer having excellent tackiness, so that the problem of the second member falling off during the transport is unlikely to occur.

[0085] (Step 4) In step 4, 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 containing no hydrogen or having a hydrogen concentration of 10% or less. Note that the oxygen-free atmosphere refers to an atmosphere having 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.

[0086] 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.

[0087] 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.

[0088] 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 a concentration below the lower explosion limit (e.g., 5% or less or 3% or less)) or low-molecular-weight alcohol (e.g., methanol, ethanol) vapor.

[0089] 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.

[0090] The maximum temperature holding time may be 1 minute or more and 60 minutes or less, 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 more, sintering tends to proceed sufficiently with a holding time of 10 minutes or less.

[0091] 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.

[0092] 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 Corporation) or the like.

[0093] In the bonded structure, at least one of the first member and the second member 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.

[0094] Examples of semiconductor devices 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, high-brightness LED modules, semiconductor laser modules, logic, and sensors.

[0095] The present invention can provide a metal-paste-applied member comprising a member and the above-described metal paste coating film provided on the member. This metal-paste-applied member can be obtained by the above-described first step.

[0096] <Jointed Body> The joined body of this embodiment is a joined body including a first member, a second member, and a joining portion joining them, wherein the joining portion includes a sintered body of the bonding metal paste of this embodiment described above. The joined body of this embodiment can be obtained by the method described above.

[0097] 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.

[0098] [Preparation of Metal Particles Having First Fatty Acid on Their Surfaces] (Submicron Copper Particles A) Submicron copper particles having a volume average particle size of 0.21 μm and a treatment amount of lauric acid of 10% by mass were prepared as submicron copper particles A having lauric acid on their surfaces.

[0099] (Submicron Copper Particles B) Copper particles having a volume average particle size of 0.18 μm and treated with 2% by mass of octanoic acid were prepared as submicron copper particles B having octanoic acid on the surface thereof.

[0100] (Micro copper particles A) A mixture of spherical copper particles having a volume average particle size of 7.3 μm and treated with 10% by mass of lauric acid and flake-shaped copper particles having a volume average particle size of 1.7 μm and treated with 10% by mass of lauric acid was prepared as micro copper particles A.

[0101] (Micro Copper Particles B) Flake-shaped copper particles having a volume average particle size of 5 μm and a treatment amount of lauric acid of 3% by mass were prepared as micro copper particles B having lauric acid on the surface.

[0102] [Preparation of Metal Paste] Metal pastes were prepared according to the procedure described 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.

[0103] (Example 1) In an environment of room temperature 25 ° C. and humidity 60%, dihydroterpineol (manufactured by Nippon Terpene Chemical Co., Ltd.) as a dispersion medium, submicro copper particles A, and micro copper particles A were mixed and stirred for 30 minutes at a rotation speed of 300 rpm using a planetary mixer (manufactured by Primix Co., Ltd.). The resulting mixture was dispersed once using a dispersizer (manufactured by Shinto Kogyo Co., Ltd.) under conditions of a gap of 50 μm and a rotation speed of 12,000 rpm to obtain a 93 mass% dispersion.

[0104] The 93% by mass dispersion obtained above was mixed with dihydroterpineol (manufactured by Nippon Terpene Chemical Co., Ltd.) as the remainder of the dispersion medium, polyethylene glycol 200 (hereinafter abbreviated as PEG200) (manufactured by NOF Corporation) as a reducing agent, and decanoic acid (manufactured by New Japan Chemical Co., Ltd.) as a second fatty acid. The mixture was stirred at 2000 rpm under reduced pressure for 3 minutes in a planetary mixer (Thinky Corporation, Awatori Rentaro ARE-310) to obtain a metal paste having a metal particle content of 81% by mass.

[0105] Examples 2 and 3 As shown in Table 1, metal pastes were obtained in the same manner as in Example 1, except that the type of the second fatty acid was changed.

[0106] Example 4 As shown in Table 1, a metal paste was obtained in the same manner as in Example 1, except that the types and amounts of the components used in preparing the metal paste were changed.

[0107] Comparative Example 1 As shown in Table 1, a metal paste was obtained in the same manner as in Example 1, except that the second fatty acid was not added and the amount of dihydroterpineol (manufactured by Nippon Terpene Chemical Co., Ltd.) added was changed.

[0108] The tack strength of the metal pastes of the examples and comparative examples was evaluated by the following method.

[0109] (1) Tack strength The metal paste obtained above was printed on a copper plate (30 mm x 30 mm x 2 mm thick) to provide a coating film of 3.0 mm x 3.0 mm x 0.1 mm thick. Next, the metal paste coating was dried for 30 minutes on a hot plate heated to 90 ° C. to form a metal particle-containing layer in which the dispersant dihydroterpineol was evaporated. On the formed metal particle-containing layer, a tabletop hot mount device (TRESKY, T-3000-FC3) was used to mount a dummy chip (3 mm x 3 mm x 0.4 mm thick, having a copper layer as the adherend surface (bonding surface)) under conditions of 1.0 MPa and 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. When a dummy chip was mounted on the metal particle-containing layer formed using the metal paste of Example 4, the mounting conditions were changed to 2.0 MPa and 1.0 second.

[0110] The tack strength of the obtained laminate was measured using a die shear tester (STELLAR 4000, manufactured by Nordson) 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.

[0111]

[0112] 10... copper substrate, 20... metal particle-containing layer, 30... dummy chip, 40... tool

Claims

1. A method for manufacturing a metal paste for joining, comprising the step of mixing at least metal particles having a first fatty acid with 10 or more carbon atoms on their surface, a second fatty acid with 18 or less carbon atoms, and a reducing agent which is a polyhydric alcohol.

2. A method for producing a metal paste for joining as described in claim 1, wherein the second fatty acid is at least one fatty acid selected from the group consisting of decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid and isostearic acid.

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

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

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

6. A metal joining paste comprising at least metal particles having a first fatty acid having 10 or more carbon atoms on their surface, a second fatty acid having 18 or less carbon atoms, and a reducing agent which is a polyhydric alcohol.

7. The metal bonding paste according to claim 6, wherein the second fatty acid is at least one fatty acid selected from the group consisting of decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, and isostearic acid.

8. The metal joining paste according to claim 6, wherein the second fatty acid is decanoic acid.

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

10. The metal bonding paste according to claim 6, wherein the polyhydric alcohol is polyethylene glycol.

11. A joined body comprising a first member, a second member, and a joining portion joining them, wherein the joining portion comprises a sintered body of the joining metal paste according to any one of claims 6 to 10.

12. A method for manufacturing a joined body, comprising: a first step of applying a joining metal paste obtained by the method according to any one of claims 1 to 5 onto a first member to form a coating film of the joining metal paste; a second step of drying the coating film to form a metal particle-containing layer; a third step of arranging a second member on the metal particle-containing layer to obtain a laminate; and a fourth step of sintering the metal particle-containing layer of the laminate.

13. The method for producing a joined body according to claim 12, 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.

14. A method for manufacturing a joined body, comprising: a first step of applying a joining metal paste according to any one of claims 6 to 10 onto a first member to form a coating film of the joining metal paste; a second step of drying the coating film to form a metal particle-containing layer; a third step of arranging a second member on the metal particle-containing layer to obtain a laminate; and a fourth step of sintering the metal particle-containing layer of the laminate.

15. The method for producing a joined body according to claim 14, 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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