Metal paste for joining, and joined body and method for producing same

Abstract

This metal paste for joining contains metal particles, a dispersion medium, and a reducing agent, contains polyethylene glycol as the reducing agent, and contains a compound A having, in a molecule, at least one group selected from the group consisting of an amino group, a carboxyl group, and an acetylene group, and a hydroxy group.

Description

Metal paste for bonding, and bonded body and method for manufacturing the same.

[0001] The present invention relates to a metal paste for joining, a joined body, and a method for manufacturing the same.

[0002] When manufacturing semiconductor devices, various bonding materials are used to form a bonding layer that joins semiconductor elements to lead frames and other support members. For example, high-lead solder has been used to form the bonding layer for power semiconductors, LSIs, etc., that operate at temperatures up to about 150°C. In recent years, with the increasing capacitance and space-saving of semiconductor elements, there has been a growing demand for high-temperature operation of semiconductors at 175°C or higher. To ensure the operational stability of such semiconductor devices, the bonding layer needs to have connection reliability and high thermal conductivity. However, in the temperature range above 175°C, conventionally used high-lead solder bonding layers have connection reliability issues and insufficient thermal conductivity (30 Wm²). －１ K －１ Therefore, alternative materials are needed.

[0003] As one alternative material, a sintered silver layer formed by the sintering phenomenon of silver particles has been proposed (see Patent Document 1 below). The sintered silver layer has high thermal conductivity (>100 Wm). －１ K －１ ), and its high connection reliability against power cycling has been reported and is attracting attention (see Non-Patent Document 1 below). However, ensuring connection reliability requires a thermocompression bonding process involving high pressure to improve the density of the sintered silver layer, which presents challenges such as damage to semiconductor chips and a decrease in the throughput of the thermocompression bonding process. Furthermore, the high material cost of silver is also a challenge.

[0004] As an alternative material, a sintered copper layer using copper has been proposed. Copper has superior mechanical strength compared to silver, and high-temperature reliability can be easily achieved without increasing the density as much as with a sintered silver layer, while also keeping 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 2 and Non-Patent Document 2 below). In this case, a reducing agent may be used in combination to facilitate the removal of the oxide film on the copper particles and the adherend, while maintaining the metal surface and promoting sintering (creating metallic bonding).

[0005] Patent No. 4247800, Patent No. 5006081

[0006] R. Khazaka, L. Mendizabal, D. Henry: J. ElecTron. Mater, 43(7), 2014, 2459-2466T. Morita, Y. Yasuda: Materials Transactions, 56(6), 2015, 878-882

[0007] The inventors have found that metal pastes containing polyethylene glycol (PEG) as a reducing agent have the advantage that PEG functions as a highly polar solvent and can exert its reducing effect at the heating temperature of the metal paste, thus ensuring sufficient sinterability. However, they also found that solvent separation (precipitation) is likely to occur in high-humidity environments.

[0008] Generally, when joining components via a sintered metal layer, a metal paste containing metal particles and a dispersion medium is dispersed and then coated onto one of the components using a printing method. Although the working environment is subject to prescribed controls, it may sometimes be an open system. During storage, dispersion, coating, or after coating, solvent separation due to a high-humidity environment may occur, potentially leading to printing defects, poor coating appearance, or reduced sinterability.

[0009] Therefore, the present invention aims to provide a bonding metal paste that contains PEG but is less prone to solvent separation even in high humidity environments, a method for manufacturing a bonded body using the same, and a bonded body.

[0010] The present invention relates to the following [1] to [8]. [1] A bonding metal paste comprising metal particles, a dispersion medium, and a reducing agent, wherein the reducing agent comprises polyethylene glycol and compound A having at least one group selected from the group consisting of an amino group, a carboxyl group, and an acetylene group, and a hydroxyl group in its molecule. [2] The bonding metal paste according to [1], wherein the metal particles are surface-treated with a fatty acid having 12 to 18 carbon atoms. [3] The bonding metal paste according to [1] or [2], wherein compound A comprises at least one selected from the group consisting of triethanolamine, diethanolamine, monoethanolamine, bis(2-hydroxyethyl)iminotris(hydroxymethyl)methane, hydroxyacetic acid, and an acetylene alcohol-based surfactant. [4] A bonding metal paste according to any one of [1] to [3], wherein the metal particles include sub-micro copper particles having a volume average particle size of 0.01 μm or more and 0.8 μm or less, and micro copper particles having a volume average particle size of 2 μm or more and 50 μm or less. [5] A bonding metal paste according to [4], wherein the micro copper particles are in the form of flakes. [6] A method for manufacturing a bonded body, comprising the steps of: preparing a laminate in which a first member, a bonding metal paste according to any one of [1] to [5], and a second member are stacked in this order; and a sintering step of sintering the bonding metal paste in the laminate. [7] A method for manufacturing a bonded body according to [6], wherein at least one of the first member and the second member is a semiconductor element. [8] A bonded body comprising a first member, a second member, and a sintered body of a bonding metal paste according to any one of [1] to [5] that bonds the first member and the second member.

[0011] According to the present invention, it is possible to provide a bonding metal paste that contains PEG but is less prone to solvent separation even in high humidity environments, a method for manufacturing a bonded body using the same, and a bonded body.

[0012] Furthermore, the bonding metal paste of the present invention can suppress the aggregation of metal particles and have sufficient printability even when prepared in a high-humidity environment.

[0013] It is a schematic cross-sectional view showing an example of a joined body manufactured using the metal paste for joining of the present embodiment. It is a schematic cross-sectional view showing an example of a joined body manufactured using the metal paste for joining of the present embodiment.

[0014] Hereinafter, a mode for carrying out the present invention (hereinafter referred to as "the present embodiment") will be described in detail. The present invention is not limited to the following embodiments.

[0015] <Metal paste for joining> The metal paste for joining of the present embodiment contains metal particles, a dispersion medium, and a reducing agent. The metal paste for joining contains polyethylene glycol as a reducing agent, and contains Compound A having at least one group selected from the group consisting of an amino group, a carboxyl group, and an acetylene group and a hydroxy group in the molecule.

[0016] According to the metal paste for joining of the present embodiment, even though it contains polyethylene glycol as a reducing agent, the occurrence of solvent separation can be suppressed even in a high-humidity environment. The present inventors speculate the reason for obtaining such an effect as follows. First, the present inventors consider that the factor causing solvent separation in a high-humidity environment is that the absorbed PEG repels the metal particles and precipitates. On the other hand, by blending Compound A, it is considered that the absorbed PEG can be affinity with the surface of the metal particles through Compound A and is less likely to precipitate.

[0017] [Metal particles] Examples of the metal particles according to the present embodiment include copper particles such as sub-micro copper particles and micro copper particles, and other metal particles other than these copper particles.

[0018] Examples of the copper particles include sub-micro 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 ratio in the particles of 80% by mass or more are referred to. The copper content ratio in 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.

[0019] (Submicro copper particles) The submicro copper particles may be copper particles that are sinterable in a temperature range of 250°C to 380°C. Examples of submicro copper particles include those containing copper particles with a particle size of 0.01 μm to 0.8 μm. For example, copper particles with a volume average particle size of 0.01 μm to 0.8 μm can be used. If the volume average particle size of the submicro copper particles is 0.01 μm or more, it is easier to obtain effects such as reduced synthesis costs, good dispersibility, and reduced use of organic protective agents. If the volume average particle size of the submicro copper particles is 0.8 μm or less, it is easier to obtain the effect of excellent sinterability of the submicro copper particles. From the viewpoint of achieving the above effects even more, the volume average particle size of the submicro 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 submicro copper particles may be 0.02 μm or larger, 0.05 μm or larger, or 0.1 μm or larger. For example, the volume-average particle size of the submicro copper particles may be 0.01 μm or larger and 0.5 μm or smaller, 0.12 μm or larger and 0.8 μm or smaller, 0.15 μm or larger and 0.8 μm or smaller, 0.15 μm or larger and 0.6 μm or smaller, 0.2 μm or larger and 0.5 μm or smaller, or 0.3 μm or larger and 0.45 μm or smaller.

[0020] In this specification, volume-average particle size refers to the 50% volume-average particle size. To determine the volume-average particle size of copper particles, dry copper particles, obtained by removing volatile components from raw copper particles or bonding metal paste, are dispersed in a dispersion medium using a dispersant, and the particle size can be measured using a light scattering particle size distribution analyzer (for example, the 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, etc., can be used as the dispersion medium.

[0021] The content of the sub-micro 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, 80% by mass or less, may be 20% by mass or more and 90% by mass or less, may be 30% by mass or more and 90% by mass or less, may be 35% by mass or more and 85% by mass or less, or may be 40% by mass or more and 80% by mass or less, based on the total mass of the metal particles. If the content of the sub-micro copper particles is within the above range, it becomes easy to ensure the bonding strength of the bonded body manufactured by sintering the copper paste for bonding. When the copper paste for bonding is used for bonding semiconductor elements, the semiconductor device tends to exhibit good die shear strength and connection reliability.

[0022] The content of the sub-micro copper particles is preferably 20% by mass or more and 90% by mass or less based on the total mass of the copper particles. If the above content of the sub-micro copper particles is 20% by mass or more, it can sufficiently fill the space between the copper particles when used in combination with micro copper particles such as flaky micro copper particles, and it becomes easy to ensure the bonding strength of the bonded body manufactured by sintering the copper paste for bonding. When the copper paste for bonding is used for bonding semiconductor elements, the semiconductor device tends to exhibit good die shear strength and connection reliability. If the content of the sub-micro copper particles is 90% by mass or less, the volume shrinkage when sintering the copper paste for bonding without pressure can be sufficiently suppressed, so it becomes easy to ensure the bonding strength of the bonded body manufactured by sintering the copper paste for bonding. When the copper paste for bonding is used for bonding 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 content of the sub-micro 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, may be 30% by mass or more and 85% by mass or less, may be 35% by mass or more and 85% by mass or less, or may be 40% by mass or more and 80% by mass or less, based on the total mass of the copper particles.

[0023] The shape of the submicro copper particles is not particularly limited. Examples of submicro copper particle shapes include spherical, lumpy, needle-shaped, flake-shaped, approximately spherical, and aggregates thereof. From the viewpoint of dispersibility and packing, the shape of the submicro copper particles may be spherical, approximately spherical, or flake-shaped, and from the viewpoint of flammability, dispersibility, and miscibility with flake-shaped microparticles, they may be spherical or approximately spherical. In this specification, "flake-shaped" includes plate-like shapes such as plate-like and flaky shapes.

[0024] The submicro copper particles may have an aspect ratio of 5 or less, 4 or less, or 3 or less, from the viewpoint of dispersibility, packing, and miscibility with flake-like microparticles. In this specification, "aspect ratio" refers to the longest side (major axis) / thickness of the particle. The longest side (major axis) and thickness of the particle can be determined, for example, from an SEM image of the particle.

[0025] The submicro copper particles may be treated with a surface treatment agent. Examples of surface treatment agents include organic acids having 2 to 18 carbon atoms.Examples of organic acids with 2 to 18 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, methylnonanoic acid, ethyloctanoic acid, propylheptanoic acid, butylhexanoic acid, undecanoic acid, methyldecanoic acid, ethylnonanoic acid, propyloctanoic acid, butylheptanoic acid, dodecanoic acid (lauric acid), methylundecanoic acid, ethyldecanoic 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 tetradecanoic acid, pr Saturated fatty acids such as propyltridecanoic acid, butyldodecanoic acid, pentylundecanoic acid, hexyldecanoic acid, heptylnonanoic acid, heptadecanoic acid, octadecanoic acid (stearic acid), methylcyclohexanecarboxylic acid, ethylcyclohexanecarboxylic acid, propylcyclohexanecarboxylic acid, butylcyclohexanecarboxylic acid, pentylcyclohexanecarboxylic acid, hexylcyclohexanecarboxylic acid, heptylcyclohexanecarboxylic acid, octylcyclohexanecarboxylic acid, nonylcyclohexanecarboxylic acid, etc.; octenic acid, nonenic acid, Examples of organic acids include unsaturated fatty acids such as methylnonenic acid, 10-hydroxy-2-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; and aromatic carboxylic acids such as terephthalic acid, pyromellitic acid, o-phenoxybenzoic acid, methylbenzoic acid, ethylbenzoic acid, propylbenzoic acid, butylbenzoic acid, pentylbenzoic acid, hexylbenzoic acid, heptylbenzoic acid, octylbenzoic acid, and nonylbenzoic acid. Organic acids may be used individually or in combination of two or more.By combining such an organic acid with the above submicro copper particles, it tends to be possible to achieve both the dispersibility of the submicro copper particles and the desorbability of the organic acid during sintering.

[0026] The treatment amount of the surface treatment agent may be an amount that adheres to the surface of the submicro copper particles in a monolayer to a trilayer. This amount depends on the number of molecular layers (n) adhering to the surface of the submicro copper particles, the specific surface area (A ｐ ) (unit: m 2 / g) of the submicro copper particles, the molecular weight (M ｓ ) (unit: g / mol) of the surface treatment agent, the minimum coating area (S Ｓ ) (unit: m ２ / particle) of the surface treatment agent, and Avogadro's number (N Ａ ) (6.02×10 ２３ particles). Specifically, the treatment amount of the surface treatment agent is calculated according to the formula: treatment amount of the surface treatment agent (mass%) = { (n·A ｐ ·M ｓ ) / (S Ｓ ·N Ａ + n·A ｐ ·M ｓ )} × 100%.

[0027] The specific surface area of the submicro copper particles can be calculated by measuring the dried submicro copper particles by the BET specific surface area measurement method. The minimum coating area of the surface treatment agent is 2.05×10 －１９ m ２ / molecule when the surface treatment agent is a straight-chain saturated fatty acid. 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" (Katsuhiro Ueda, Junio Inafuku, Iwao Mori, 40(2), 1992, p114 - 117). An example of a method for quantifying the surface treatment agent is shown. The surface treatment agent can be identified by thermodesorption gas / gas chromatograph mass spectrometer of the dry powder obtained by removing the dispersion medium from the copper paste for bonding, and thereby the carbon number and molecular weight of the surface treatment agent can be determined. The carbon content ratio of the surface treatment agent can be analyzed by carbon content analysis. Examples of the carbon content analysis method include, for example, high-frequency induction heating furnace combustion / infrared absorption method. The amount of the surface treatment agent can be calculated from the carbon number, molecular weight, and carbon content ratio of the identified surface treatment agent using the above formula.

[0028] The amount of surface treatment agent used may be 0.07% by mass or more and 2.1% by mass or less, 0.10% by mass or more and 1.6% by mass or less, or 0.2% by mass or more and 1.1% by mass or less, based on the mass of the submicro copper particles having the surface treatment agent.

[0029] Commercially available submicro copper particles can be used. Examples of commercially available submicro particles include CH-0200L1 (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 0.2 μm), 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 Corporation, volume average particle size 0.12 μm).

[0030] Because submicro copper particles have good sinterability, they can reduce the problems associated with bonding materials that mainly use copper nanoparticles, such as high synthesis costs, poor dispersibility, and reduced volume shrinkage after sintering.

[0031] (Micro-copper particles) As micro-copper particles, copper particles with a particle size of 2 μm or more and 50 μm or less can be used. For example, copper particles with a volume average particle size of 2 μm or more and 50 μm or less can be used. If the volume average particle size of the micro-copper particles is within the above range, volume shrinkage and void generation when the bonding copper paste is sintered without pressure can be sufficiently reduced, making it easier to ensure the bonding strength of the bonded body manufactured by sintering the bonding copper paste without pressure. When the bonding copper paste is used to bond semiconductor elements, the semiconductor device tends to exhibit good die-shear strength and connection reliability. From the viewpoint of achieving the above effects even more, the volume average particle size of the micro-copper particles may be 2 μm or more and 20 μm or less, 2 μm or more and 10 μm or less, 3 μm or more and 20 μm or less, or 3 μm or more and 10 μm or less.

[0032] The shape of the micro-copper particles is preferably flake-shaped. By using flake-shaped micro-copper particles, the micro-copper particles in the bonding copper paste are oriented substantially parallel to the bonding surface, thereby suppressing volume shrinkage when the bonding copper paste is sintered, and making it easier to ensure the bonding strength of the bonded body manufactured by sintering the bonding copper paste. When the bonding copper paste is used to bond semiconductor elements, the semiconductor device tends to exhibit good die-shear strength and connection reliability. From the viewpoint of achieving the above effects even more, the aspect ratio of the flake-shaped micro-copper particles may be 4 or more, 6 or more, 10 or more, or 50 or more.

[0033] The content of micro copper particles may be 10% by mass or more, 15% by mass or more, 20% by mass or more, 90% by mass or less, 65% by mass or less, 60% by mass or less, 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 copper particles. If the content of micro copper particles is within the above range, it becomes easier to ensure the bonding strength of the bonded body manufactured by sintering the bonding copper paste, and when the bonding copper paste is used to bond semiconductor elements, the semiconductor device tends to exhibit good die-shear strength and connection reliability.

[0034] In the case of micro copper particles, there is no particular limitation on whether or not they 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. The surface treatment agent may be removed during bonding. Examples of such surface treatment agents include aliphatic carboxylic acids such as dodecanoic acid (lauric acid), palmitic acid, heptadecanoic acid, octadecanoic acid (stearic acid), arachidic acid, linoleic acid, linolenic acid, and oleic acid; aromatic carboxylic acids such as terephthalic acid, pyromellitic acid, and o-phenoxybenzoic acid; aliphatic alcohols such as cetyl alcohol, stearyl alcohol, isobornylcyclohexanol, and tetraethylene glycol; aromatic alcohols such as p-phenylphenol; alkylamines such as octylamine, dodecylamine, and stearylamine; aliphatic nitriles such as stearonitrile and decanonitrile; silane coupling agents such as alkylalkoxysilanes; and polymeric treatment agents such as polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, and silicone oligomers. The surface treatment agent may be used individually or in combination of two or more types.

[0035] The amount of surface treatment agent applied may be one molecular layer or more on the particle surface. The amount of surface treatment agent applied 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 surface treatment agent applied may be 0.001% by mass or more, 0.4% by mass or more, 0.5% by mass or more, 2.0% by mass or less, 1.7% by mass or less, 0.001% by mass or more and 2.0% by mass or less, 0.4% by mass or more and 2.0% by mass or less, or 0.5% by mass or more and 1.7% by mass or less, 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 described above for sub-micro copper particles.

[0036] Commercially available micro-copper particles can be used. Examples of commercially available flake-shaped microparticles include MA-05KFD (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 8 μm), MA-C025KFD (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 7.5 μm), 3L3N (manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd., volume average particle size 6 μm), 2L3N (manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd., volume average particle size 9.9 μm), 4L3N (manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd., volume average particle size 3 μm), C3 (manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd., volume average particle size 37 μm), and 1110F (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 3.8 μm). An example of a commercially available spherical microparticle is FMC-10 (manufactured by Furukawa Chemicals Corporation, volume average particle size 2 μm).

[0037] The bonding copper paste according to this embodiment can include sub-micro copper particles and micro copper particles. When a bonding copper paste is prepared using only the sub-micro copper particles, the volume shrinkage and sintering shrinkage associated with the drying of the dispersion medium are large, making it easy for the bonding copper paste to peel off from the bonded surface during sintering, and making it difficult to obtain sufficient die-shear strength and connection reliability when bonding semiconductor elements. When a bonding copper paste is prepared using only the micro copper particles, the sintering temperature tends to be high, requiring a sintering process of 400°C or higher. By using sub-micro copper particles and micro copper particles in combination, volume shrinkage when the bonding copper paste is sintered is suppressed, and the bonded body can have sufficient bonding strength. When the bonding copper paste is used to bond semiconductor elements, the semiconductor device exhibits good die-shear strength and connection reliability.

[0038] From the above viewpoint, the copper paste for bonding according to this embodiment contains, as copper particles, sub-micro copper particles having a volume average particle size of 0.15 μm or more and 0.8 μm or less, and micro copper particles having a volume average particle size of 2 μm or more and 50 μm or less, and the total content of sub-micro copper particles and micro copper particles is 80% by mass or more based on the total mass of metal particles, and the content of sub-micro copper particles may be 30% by mass or more, 90% by mass or less, or 30% by mass or more and 90% by mass or less, based on the total mass of sub-micro copper particles and micro copper particles.

[0039] The copper paste for joining according to this embodiment may contain sub-micro copper particles, flake-shaped micro copper particles, and spherical micro copper particles, from the viewpoint of low-temperature sinterability, suppression of volume shrinkage in the XY direction (direction parallel to the joining surface), and improvement of copper particle filling properties.

[0040] (Metal particles other than copper particles) The bonding metal paste of this embodiment may contain metal particles containing metal elements other than copper (other metal particles). Other metal particles may include, for example, particles of zinc, gold, palladium, silver, nickel, platinum, brass, manganese, tin, antimony, indium, aluminum, vanadium, etc. The volume average particle size of the other metal particles may be 0.01 μm or more, 0.03 μm or more, 0.05 μm or more, 10 μm or less, 5 μm or less, 3 μm or less, 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.

[0041] When the bonding copper paste contains other metal particles, a sintered body can be obtained in which multiple types of metals are dissolved or dispersed. This improves the mechanical properties of the sintered body, such as yield stress and fatigue strength, and enhances connection reliability. Furthermore, by adding multiple types of metal particles, the sintered body of the bonding copper paste can have sufficient bonding strength for a specific adherend. When the bonding copper paste is used for bonding semiconductor elements, the die shear strength and connection reliability of the semiconductor device tend to improve.

[0042] If the copper bonding paste contains other metal particles, the amount of these particles may be less than 5% by mass, 3% or less by mass, or 1% or less by mass, based on the total mass of the metal particles, from the viewpoint of obtaining sufficient bonding properties. The copper bonding paste does not need to contain other metal particles. The shape of the other metal particles is not particularly limited.

[0043] In the bonding metal paste of this embodiment, the metal particles may be surface-treated with a fatty acid having 12 to 18 carbon atoms. The fatty acid having 12 to 18 carbon atoms may be dodecanoic acid (lauric acid) or octadecanoic acid (stearic acid), and one type may be used alone or in combination of two or more types. If the bonding metal paste of this embodiment contains the above-mentioned sub-micro copper particles and micro copper particles as metal particles, these copper particles may be surface-treated with a fatty acid having 12 to 18 carbon atoms.

[0044] Since the surface of the metal particles subjected to the above surface treatment exhibits strong hydrophobicity, it is thought that the repulsion with water-absorbing PEG will become stronger (solvent separation will be more likely to occur). However, by incorporating compound A as described above, the particle surface can be made partially hydrophilic, thereby suppressing the occurrence of solvent separation even in a high-humidity environment.

[0045] The bonding metal paste of this embodiment may contain inorganic particles other than metal particles at a rate of 30% by mass or less, 20% by mass or less, or 1% by mass or less, based on the total amount of bonding metal paste. The bonding copper paste may not contain any inorganic particles other than metal particles.

[0046] [Reducing agent] The copper paste for bonding contains polyethylene glycol as a reducing agent.

[0047] Examples of polyethylene glycol include polyethylene glycol 200, polyethylene glycol 300, and polyethylene glycol 400. These can be used individually or in combination of two or more types.

[0048] The copper paste for bonding may contain polyethylene glycol 200, from the viewpoint of volatile behavior and the timing of reduction activity.

[0049] The polyethylene glycol content in the copper bonding paste may be 1 to 10 parts by mass per 100 parts by mass of total copper particles, from the viewpoint of suppressing sintering defects and ensuring bonding strength, or it may be 5 parts by mass or less, from the viewpoint of suppressing a decrease in bonding strength due to excess reducing agent.

[0050] When the bonding copper paste contains copper particles and other metal particles, the polyethylene glycol content may be within the range described above, relative to 100 parts by mass of the total mass of the metal particles. Examples of other metal particles include zinc, gold, palladium, silver, nickel, platinum, brass, manganese, tin, antimony, indium, aluminum, and vanadium.

[0051] The copper paste for bonding may further contain reducing agents other than polyethylene glycol. Examples of such reducing agents include diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol, dipropylene glycol, trippropylene glycol, tetrapropylene glycol, polypropylene glycol, polypropylene glycol 200, polypropylene glycol 300, polypropylene glycol 400, polypropylene glycol 700, polypropylene glycol 4000, polyethylene glycol monooleate, polyethylene glycol monostearate, polyethylene glycol monolaurate, polyoxyethylene sorbitan monolaurate, and polyoxyethylene polyoxypropylene glycol. These can be used individually or in combination of two or more.

[0052] The reducing agent content in the copper paste for bonding may be 1.6 parts by mass or more, 1.8 parts by mass or more, 2.0 parts by mass or more, or 4.0 parts by mass or more per 100 parts by mass of total copper particles, from the viewpoint of suppressing sintering defects and ensuring bonding strength. Alternatively, from the viewpoint of suppressing a decrease in bonding strength due to an excess of reducing agent, it may be 10 parts by mass or less, 9.0 parts by mass or less, or 8.5 parts by mass or less.

[0053] Furthermore, if the bonding copper paste contains copper particles and other metal particles, the reducing agent content may be within the range described above, relative to 100 parts by mass of the total mass of the metal particles. Examples of other metal particles include zinc, gold, palladium, silver, nickel, platinum, brass, manganese, tin, antimony, indium, aluminum, and vanadium.

[0054] [Dispersion medium] Examples of dispersion mediums include monohydric and polyhydric alcohols such as pentanol, hexanol, heptanol, octanol, decanol, dihydroterpineol, terpineol, and isobornylcyclohexanol (MTPH); polyethylene glycol, 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, triethylene glycol dimethyl ether, triethylene glycol butyl methyl ether, propylene glycol propyl ether, dipropylene glycol methyl ether, dipropylene Examples include ethers such as ethylene 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, and xylene; mercaptans having alkyl groups with 1 to 18 carbon atoms; and mercaptans having cycloalkyl groups with 5 to 7 carbon atoms.Examples of mercaptans having an alkyl group with 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 with 5 to 7 carbon atoms include cyclopentyl mercaptan, cyclohexyl mercaptan, and cycloheptyl mercaptan.

[0055] The dispersion medium may contain a solvent with a boiling point of 140°C or higher, a solvent with a boiling point of 170°C or higher, or a solvent with a boiling point of 200°C or higher, from the viewpoint of printing life (printing life). Furthermore, the boiling point of the solvent may be 400°C or lower, 380°C or lower, or 360°C or lower, as it is necessary for the solvent to be removed after sintering.

[0056] The dispersion medium can be used individually or in combination of two or more types.

[0057] The copper paste for bonding in this embodiment may contain polyethylene glycol and terpineol with a molecular weight of 200 to 300 as a reducing agent and dispersion medium, or it may contain polyethylene glycol and dihydroterpineol with a molecular weight of 200 to 300.

[0058] [Compound A] Compound A has at least one group selected from the group consisting of an amino group, a carboxyl group, and an acetylene group, and a hydroxyl group within its molecule.

[0059] Examples of compound A include triethanolamine, diethanolamine, monoethanolamine, amino alcohol compounds represented by the following general formulas (1) or (2), hydroxyacetic acid, and acetylene alcohol-based surfactants. Compound A can be used individually or in combination of two or more.

[0060] [In formula (1), R １１ ~R １５Each of these independently represents a hydrogen atom, a hydroxyl group, a hydrocarbon group having 1 to 10 carbon atoms, or a hydrocarbon group having 1 to 10 carbon atoms that has a hydroxyl group, R １１ ~R １５ At least one of these is a hydroxyl group or a hydrocarbon group having 1 to 10 carbon atoms that contains a hydroxyl group. [In formula (2), R ２１ ~R ２２ and R ２５ ~R ２７ Each of these independently represents a hydrogen atom, a hydroxyl group, a hydrocarbon group having 1 to 10 carbon atoms, or a hydrocarbon group having 1 to 10 carbon atoms that has a hydroxyl group, R ２４ R represents a divalent hydrocarbon group having 1 to 10 carbon atoms or a divalent hydrocarbon group having 1 to 10 carbon atoms that has a hydroxyl group, ２１ ~R ２２ and R ２５ ~R ２７ And R ２４ At least one of them is a group containing a hydroxyl group.

[0061] In equation (1), R １１ ~R １５ Two or more, three or more, four or more, or five of these may contain hydroxyl groups, R １１ ~R １５ At least two of these may be hydroxyalkyl groups having 1 to 4 carbon atoms. In formula (2), R ２１ ~R ２２ and R ２５ ~R ２７ Two or more, three or more, four or more, or five or more of these may contain hydroxyl groups, R ２１ ~R ２２ and R ２５ ~R ２７ At least two of these may be hydroxyalkyl groups having 1 to 4 carbon atoms.

[0062] The amino alcohol compound represented by general formula (1) or (2) may be solid at 25°C. In this case, it may be dissolved in a dispersion medium and incorporated into the copper paste for bonding.

[0063] Examples of amino alcohol compounds represented by general formula (1) include bis(2-hydroxyethyl)iminotris(hydroxymethyl)methane, N-ethyldiethanolamine, N-ethyldiethanolamine, 2-(diethylamino)ethanol, 3-diethylamino-1-propanol, N-butyldiethanolamine, N-(2-hydroxyethyl)iminodiacetic acid, bicine, 1-[N,N-bis(2-hydroxyethyl)amino]-2-propanol, N,N-diisopropylethanolamine, N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid, 2-amino-2-(hydroxymethyl)-1,3-propanediol, and N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine. Examples of amino alcohol compounds represented by general formula (2) include 1,3-bis(tris(hydroxymethyl)methylamino)propane.

[0064] The acetylene alcohol-based surfactant may be an acetylene glycol compound represented by the following general formula (A-1).

[0065] [In formula (A-1), R １ and R ２ This represents a hydrocarbon group having 6 to 12 carbon atoms, L １ and L ２ R represents an ethylene group or a propylene group, and n and m represent integers of 0 or 1 or more. １ and R ２ They may be the same or they may be different. １ and L ２ They may be the same or they may be different.

[0066] The acetylene glycol compound represented by general formula (A-1) may be acetylene glycol or an acetylene glycol alkylene oxide adduct. Examples of acetylene glycols include 5,8-dimethyl-6-dodecine-5,8-diol, 4,7-dimethyl-5-decine-4,7-diol, 2,4,7,9-tetramethyl-5-decine-4,7-diol, 2,3,6,7-tetramethyl-4-octin-3,6-diol, 3,6-dimethyl-4-octin-3,6-diol, 3,6-diethyl-4-octin-3,6-diol, and 2,5-dimethyl-3-hexyne-2,5-diol.

[0067] Acetylene glycol alkylene oxide adducts can be obtained by alkylating the above-mentioned acetylene glycol. The average number of added moles of alkylene oxide may be 1 to 6.

[0068] Acetylene alcohol-based surfactants such as "Acetylenel E00," "Acetylenel E40," and "Acetylenel E13T" (all manufactured by Kawasaki Fine Chemical Co., Ltd., trade names) and "Orphine" (manufactured by Nisshin Chemical Industry Co., Ltd., trade name) may be used as commercially available products.

[0069] Compounds containing both a carboxyl group and a hydroxyl group include hydroxyacetic acid, citric acid, ascorbic acid, tartaric acid, glyoxylic acid, lactic acid, and malic acid.

[0070] Compound A may be included as is, or it may be included after being dispersed in a dispersion medium.

[0071] The content of compound A in the copper paste for bonding may be 0.5 to 5 parts by mass per 100 parts by mass of the total mass of copper particles, from the viewpoint of suppressing solvent separation, and may be 3 parts by mass or less, from the viewpoint of suppressing a decrease in bonding strength due to excess compound A.

[0072] Furthermore, if the bonding copper paste contains copper particles and other metal particles, the content of compound A may be within the range described above, relative to 100 parts by mass of the total mass of the metal particles.

[0073] [Additives] The bonding metal paste may further contain additives such as dispersants, surface protectants, thickeners, and thixotropic agents as needed.

[0074] When the bonding metal paste contains additives, from the viewpoint of suppressing a decrease in the sinterability of the bonding metal paste, the content of additives that are non-volatile or non-degradable at temperatures of 200°C or below may be 20% by mass or less, 5% by mass or less, or 1% by mass or less, based on the total amount of the bonding metal paste.

[0075] <Method for preparing bonding metal paste> The bonding metal paste of this embodiment can be prepared by mixing the above-mentioned copper particles (e.g., sub-micro copper particles and micro copper particles), a reducing agent (e.g., PEG), compound A, a dispersion medium, and, if necessary, other metal particles and any additives. After mixing each component, stirring may be performed. The maximum particle size of the dispersion liquid may be adjusted by a classification operation.

[0076] The bonding metal paste may be prepared by pre-mixing submicro copper particles, an organic protective agent (e.g., a fatty acid with 12 to 18 carbon atoms), and a dispersion medium, performing a dispersion treatment to prepare a dispersion of submicro copper particles, and then further mixing in the remaining components (e.g., a reducing agent, compound A, micro copper particles, etc.). The remaining components may be dispersed in a dispersion medium (e.g., alcohols) before being mixed with the submicro copper particle dispersion. This procedure improves the dispersibility of the submicro copper particles and improves their mixability with micro copper particles (e.g., flake-shaped micro copper particles), thereby further improving the performance of the bonding copper paste. Aggregates may also be removed from the submicro copper particle dispersion by a classification operation. The submicro copper particles and organic protective agent may be submicro copper particles treated with the organic protective agent. If compound A is a solid, it may be pulverized by methods such as freeze-drying and added. In this case, it may be pulverized to a degree similar to that of copper particles.

[0077] The stirring process can be carried out using a stirrer. Examples of stirrers include the Ishikawa stirrer, Silverson stirrer, cavitation stirrer, rotational stirring device, ultra-thin film high-speed rotary disperser, ultrasonic disperser, Raikai machine, twin-screw kneader, bead mill, ball mill, three-roll mill, homomixer, planetary mixer, ultra-high pressure disperser, thin-layer shear disperser, and disparizer.

[0078] Examples of dispersion processes include thin-layer shear dispersers, disparizers, bead mills, ultrasonic homogenizers, high-shear mixers, narrow-gap three-roll mills, wet-type ultra-fine atomizers, supersonic jet mills, and ultra-high-pressure homogenizers.

[0079] Classification operations can be carried out, for example, by filtration, natural sedimentation, or centrifugal separation. Examples of filters used for filtration include water combs, metal mesh, metal filters, and nylon mesh.

[0080] The bonding copper paste may be adjusted to a viscosity suitable for the printing and coating method. The viscosity of the bonding copper paste may, for example, be 0.05 Pa·s or higher, 0.06 Pa·s or higher, 2.0 Pa·s or lower, 1.0 Pa·s or lower, 0.05 Pa·s to 2.0 Pa·s or lower, or 0.06 Pa·s to 1.0 Pa·s or lower at 25°C. The Casson viscosity at 25°C can be measured using a viscoelasticity measuring device.

[0081] <Method for manufacturing a bonded body> The method for manufacturing a bonded body according to this embodiment comprises a laminate preparation step of preparing a laminate in which a first member, the bonding metal paste according to this embodiment described above, and a second member are stacked in this order, and a sintering step of sintering the bonding metal paste in the laminate.

[0082] (Laminate preparation process) Examples of the first and second components include semiconductor elements such as IGBTs, diodes, Schottky barrier diodes, MOS-FETs, thyristors, logic circuits, sensors, analog integrated circuits, LEDs, semiconductor lasers, and oscillators; lead frames, metal plate-attached ceramic substrates (e.g., DBC); substrates for mounting semiconductor elements such as LED packages; power supply components such as copper ribbons, metal blocks, and terminals; heat sinks; water cooling plates; and the like.

[0083] The first and second members may have a metal layer on their joint surface that forms a metallic bond with the sintered body of the joining metal paste. Examples of metals that make up the metal layer include copper, nickel, silver, gold, palladium, platinum, lead, tin, and cobalt. These metals may be used individually or in combination of two or more. The metal layer may also be an alloy containing the above metals. Examples of metals that can be used in alloys, in addition to the above metals, include zinc, manganese, aluminum, beryllium, titanium, chromium, iron, and molybdenum. Examples of members having a metal layer include members with various metal platings, wires, metal-plated chips, heat spreaders, ceramic substrates with metal plates attached, lead frames with various metal platings or lead frames made of various metals, copper plates, and copper foils.

[0084] The laminate can be prepared, for example, by applying the bonding metal paste of this embodiment to the necessary portion of the second member described above, and then placing the first member described above on the bonding metal paste. In this case, a laminate can be prepared in which the first member, the bonding metal paste, and the second member are laminated in this order on the side in which the weight of the first member acts, and the bonding metal paste of this laminate can be sintered without pressure, that is, under the weight of only the weight of the first member, or the weight of the first member and the weight of a weight used to prevent tilting of the chip or to reduce voids. The weight of the weight may be 0.01 MPa or less when converted to pressure. Note that the direction in which the weight of the first member acts can also be said to be the direction in which gravity acts.

[0085] Suitable weights include metal weights that are roughly the same size as the chip and have a thickness of 20 mm or less. For metal weights, stainless steel weights with a thickness of 5 mm or less can be used.

[0086] The method for applying the bonding metal paste of this embodiment to the required portion of the second member can be any method that allows for the deposition of bonding copper paste. Such methods include inkjet printing, super inkjet printing, screen printing, transfer printing, offset printing, jet printing, dispensers, jet dispensers, needle dispensers, comma coaters, slit coaters, die coaters, gravure coaters, slit coats, letterpress printing, intaglio printing, gravure printing, stencil printing, soft lithography, bar coating, applicators, particle deposition methods, spray coaters, spin coaters, dip coaters, electrodeposition coating, and the like.

[0087] The thickness of the bonding metal paste may be 1 μm or more, 5 μm or more, 10 μm or more, or 20 μm or more. Furthermore, the thickness of the bonding metal paste 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.

[0088] The applied bonding metal paste may be dried as appropriate to suppress flow and void formation during sintering. The gas atmosphere during drying may be air, an oxygen-free atmosphere such as nitrogen or a noble gas, or a reducing atmosphere such as hydrogen or formic acid. The drying method may be drying at room temperature, heating, or reduced pressure.

[0089] For heating and drying or vacuum drying, for example, a hot plate, hot air dryer, hot air heating furnace, nitrogen dryer, infrared dryer, infrared heating furnace, far-infrared heating furnace, microwave heating device, laser heating device, electromagnetic heating device, heater heating device, steam heating furnace, hot plate press device, etc. may be used. The drying temperature and time may be adjusted as appropriate according to the type and amount of dispersion medium used. Ideally, drying should be done in air or an oxygen-free atmosphere at a temperature between 50°C and 150°C.

[0090] Methods for positioning the first component on the bonding metal paste include, for example, a chip mounter, a flip-chip bonder, and a positioning jig made of carbon or ceramic.

[0091] (Sintering Process) In the sintering process, the copper paste for joining can be sintered by heat treatment in an oxygen-free atmosphere under no-pressure conditions. The oxygen-free atmosphere may be an atmosphere that does not contain hydrogen or has a hydrogen concentration of 10% or less. Note that an oxygen-free atmosphere refers to an atmosphere with an oxygen concentration of 1 volume percent or less, and the oxygen concentration may be 0.1 volume percent or less, 0.01 volume percent or less, or 0.001 volume percent or less.

[0092] For the heat treatment, a heating device without a compression mechanism can be used. Examples of heating devices include hot plates, hot air dryers, hot air heating furnaces, nitrogen dryers, infrared dryers, infrared heating furnaces, far-infrared heating furnaces, microwave heating devices, laser heating devices, electromagnetic heating devices, heater heating devices, steam heating furnaces, and the like.

[0093] Examples of hydrogen-free atmospheres include non-oxidizing gases such as nitrogen, noble gases, heat-resistant organic gases, water vapor, or mixtures thereof, or under vacuum.

[0094] The gas atmosphere during sintering may be a reducing atmosphere. Examples of reducing atmospheres include nitrogen containing formic acid gas, a noble gas containing formic acid gas, and a non-oxidizing gas containing 10% or less hydrogen. Alternatively, the gas atmosphere during sintering may be a forming gas (nitrogen containing hydrogen below the lower explosive limit (e.g., 5% or less or 3% or less)) or low molecular weight alcohol (e.g., methanol, ethanol) vapor.

[0095] The maximum temperature reached during the heat treatment may be 200°C or higher, 220°C or higher, or 250°C or higher, from the viewpoint of improving yield; from the viewpoint of reducing thermal damage to the joining members, it may be 450°C or lower, 400°C or lower, 350°C or lower, or 300°C or lower; and from the viewpoint of reducing thermal damage to the joining members and improving yield, it may be 200°C or higher and 450°C or lower, 250°C or higher and 400°C or lower, 250°C or higher and 350°C or lower.

[0096] The holding time at the maximum temperature reached may be between 1 minute and 60 minutes, between 1 minute and 40 minutes, or between 1 minute and 30 minutes, from the viewpoint of completely volatilizing the dispersion medium and improving yield. In particular, if the maximum temperature reached is 250°C or higher, sintering can proceed sufficiently with a holding time of 60 minutes or less.

[0097] <Bonded Body and Semiconductor Device> Preferred embodiments will be described in detail below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations are omitted. Also, the dimensional ratios in the drawings are not limited to those shown.

[0098] Figure 1 is a schematic cross-sectional view showing an example of a joined body manufactured using a bonding metal paste. The joined body 100 of this embodiment comprises a first member 1 having a first base portion 1a and a first metal layer 1b, a second member 3 having a second base portion 3a and a second metal layer 3b, and a sintered body 2 that joins the first member 1 and the second member 3.

[0099] The first member 1 and the second member 3 are as described above. The first metal layer 1b and the second metal layer 3b are also as described above.

[0100] The sintered body 2 may be a sintered body of the joining metal paste according to this embodiment. In this case, the joined body 100 can be obtained by the method for manufacturing the joined body according to this embodiment described above.

[0101] The die shear strength of the joint may be 10 MPa or more, 15 MPa or more, 20 MPa or more, or 30 MPa or more, from the viewpoint of sufficiently joining the first member and the second member. The die shear strength can be measured using a universal bond tester (4000 series, manufactured by DAGE Corporation) or the like.

[0102] The thermal conductivity of the sintered body may be 100 W / (m·K) or higher, 120 W / (m·K) or higher, or 150 W / (m·K) or higher, from the viewpoint of heat dissipation and connection reliability at high temperatures. The thermal conductivity can be calculated from the thermal diffusivity, specific heat capacity, and density of the sintered body of the joining metal paste.

[0103] In the above-described joint, at least one of the first member and the second member may be a semiconductor element. Examples of semiconductor elements include power modules, oscillators, amplifiers, LED modules, etc., consisting of diodes, rectifiers, thyristors, MOS gate drivers, power switches, power MOSFETs, IGBTs, Schottky diodes, fast recovery diodes, etc. In such cases, the joint becomes a semiconductor device. The resulting semiconductor device can have sufficient die-shear strength and connection reliability.

[0104] Figure 2 is a schematic cross-sectional view showing an example of a semiconductor device manufactured using a bonding metal paste. The semiconductor device 200 shown in Figure 2 comprises a semiconductor element 4 having a metal layer 4b and a base 4a, connected via a sintered body 2 of bonding copper paste to a lead frame 5 having a metal layer 5b and a base 5a, and a mold resin 6 for molding these. The semiconductor element 4 is connected to a lead frame 8 having a metal layer 8b and a base 8a via a wire 7.

[0105] 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., as well as oscillators, amplifiers, high-brightness LED modules, semiconductor laser modules, logic circuits, sensors, and the like.

[0106] The semiconductor device described above can be manufactured in the same manner as the manufacturing method for the bonded body according to the embodiment described above. That is, the manufacturing method for the semiconductor device may include a step of sintering the bonding metal paste by heating the laminate in an oxygen-free atmosphere without pressure, using a semiconductor element in at least one of the first member and the second member, in which order the first member, bonding metal paste, and the second member are stacked, and using a semiconductor element in at least one of the first member and the second member. The oxygen-free atmosphere may be an atmosphere that does not contain hydrogen or has a hydrogen concentration of 10% or less.

[0107] The bonding metal paste may have the same composition as the bonding metal paste according to this embodiment. The preparation of the laminate and the sintering of the bonding metal paste can also be carried out in the same manner as the laminate preparation step and sintering step described above.

[0108] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples.

[0109] [Preparation of bonding metal paste] The bonding metal pastes in the amounts (parts by mass) shown in Table 1 were prepared according to the following procedure.

[0110] (Example 1) In an environment at room temperature (25°C) and 60% humidity, 9 g of dihydroterpineol (manufactured by Nippon Terpene Chemical Co., Ltd.) as a dispersion medium and 91 g of CH-0200L1 (manufactured by Mitsui Mining & Smelting Co., Ltd., product name, volume average particle size 0.2 μm) as submicro copper particles were mixed and stirred for 30 minutes at a rotation speed of 300 rpm using a planetary mixer (manufactured by Primix). The resulting mixture was dispersed once using a disparizer (manufactured by Shinto Kogyo Co., Ltd.) under conditions of a gap of 50 μm and a rotation speed of 12000 rpm to obtain a 91% by mass dispersion.

[0111] As the remaining dispersion medium, 3 g of dihydroterpineol and 6 g of isobornylcyclohexanol (MTPH) were mixed with 4 g of polyethylene glycol 200 (hereinafter abbreviated as PEG200) (manufactured by NOF Corporation) as a reducing agent, 1 g of triethanolamine as compound A, 62 g of the 91% by mass dispersion obtained above, and 12 g of MA-05KFD (manufactured by Mitsui Mining & Smelting Co., Ltd., product name, volume average particle size 8 μm) and 12 g of FMC-10 (manufactured by Furukawa Chemicals Co., Ltd., product name, volume average particle size 2 μm) as micro copper particles. The mixture was stirred at 2000 rpm under reduced pressure for 3 minutes using a rotary mixer (Sinky, Awatori Rentaro ARE-310) to obtain a bonding metal paste.

[0112] (Examples 2-7) As shown in Table 1, bonding metal pastes were obtained in the same manner as in Example 1, except that compound A was replaced with diethanolamine, monoethanolamine, hydroxyacetic acid, acetylenol E40 (manufactured by Kawaken Fine Chemicals Co., Ltd., product name), acetylenol E00 (manufactured by Kawaken Fine Chemicals Co., Ltd., product name), and acetylenol E13T (manufactured by Kawaken Fine Chemicals Co., Ltd., product name).

[0113] (Comparative Example 1) A bonding metal paste was obtained in the same manner as in Example 1, except that triethanolamine was not included.

[0114] [Evaluation of Bonding Metal Paste - 1] Using the bonding metal pastes obtained in the examples and comparative examples, bonded bodies were prepared in a high-humidity environment according to the method described below, and the "solvent separation" and "appearance" of the coating film, as well as the die shear strength, were evaluated. The results are shown in the table.

[0115] A metal paste was applied to a copper plate (30 mm x 30 mm x 2 mm) by stencil printing using an automatic printing press "LZ-0913" (manufactured by Newlong Co., Ltd.) and a stainless steel stencil mask with a thickness of 100 μm and an opening size of 12.6 mm x 11.4 mm. The printing pressure (air pressure) on the squeegee was set to 0.08 MPa. The coating film was then visually observed after being left for 0.5 hours in an environment with humidity of 70% or higher and evaluated according to the following criteria. (Criteria for solvent separation) A: No droplets have formed on the surface B: Droplets have formed on the surface (Criteria for appearance) A: No droplets B: Droplets are present

[0116] After observing the coating, a copper chip (area 2 mm x 2 mm, thickness 0.4 mm) was placed on the applied metal paste to obtain a laminate. The laminate was heated in air at 90°C for 30 minutes on a hot plate (AS ONE Corporation, EC HOTPLATE EC-1200N). The laminate was set in a bonding device (Ayumi Kogyo Co., Ltd.), the pressure was reduced to 13 Pa to remove the air, and then nitrogen gas was flowed to bring the pressure to 80 kPa while the laminate was pressurized and heated under the conditions of 260°C, 10 MPa pressure, and 5 minutes of compression bonding to obtain a bonded body in which the copper plate and copper chip were joined with a copper sintered body. This bonded body was cooled with nitrogen gas and removed into the air when the temperature fell below 50°C.

[0117] Next, a universal bond tester (4000 series, DAGE Corporation) equipped with a 1 kN load cell was used to measure the maximum load by pressing a copper chip horizontally at a measurement speed of 300 μm / s and a measurement height of 50 μm. For the measurement, a sample with 12 copper chips pressed together was prepared, with N=11, and the die shear strength was calculated by dividing the average of the maximum loads by the chip area.

[0118] [Evaluation of bonding metal paste - 2] The bonding metal pastes obtained in the examples and comparative examples were stored for 1 hour in an environment with a humidity of 70% or higher.

[0119] Using the metal paste for bonding after storage, bonded bodies were prepared according to the method described below, and the "solvent separation" and "appearance" of the coating film, as well as the die shear strength, were evaluated in the same manner as described above. The results are shown in the table.

[0120] Using an automatic printing press "LZ-0913" (manufactured by Newlong Co., Ltd., product name) and a stainless steel stencil mask with a thickness of 100 μm and an opening size of 12.6 mm x 11.4 mm, metal paste was applied to a copper plate (30 mm x 30 mm x 2 mm) by stencil printing. The printing pressure (air pressure) applied to the squeegee was set to 0.08 MPa. The coating film was observed visually and evaluated in the same manner as described above.

[0121] After observing the coating film, a joint was obtained in the same manner as described above. The die shear strength of the obtained joint was evaluated in the same manner as described above.

[0122]

[0123] (Examples 8-11 and Comparative Example 2) Bonding metal pastes were obtained in the same manner as in Examples 1, 5-7 and Comparative Example 1, except that they were prepared in an environment with a humidity of 70% or higher.

[0124] [Evaluation of bonding metal paste - 3]

[0125] Using the metal paste for bonding after storage, bonded bodies were prepared according to the method described below, and their "printability," "solvent separation" and "appearance" in the coating film, and die shear strength were evaluated. The results are shown in the table.

[0126] Using an automatic printing press "LZ-0913" (manufactured by Newlong Co., Ltd., product name) and a stainless steel stencil mask with a thickness of 100 μm and an opening size of 12.6 mm x 11.4 mm, metal paste was applied to a copper plate (30 mm x 30 mm x 2 mm) by stencil printing. The printing pressure (air pressure) on the squeegee was set to 0.08 MPa. The printability was evaluated according to the following criteria: (Criteria for evaluating printability) A: No streaks or aggregates after printing B: Streaks or aggregates are present after printing, and the base material may be visible in some cases

[0127] Furthermore, the coating film was visually inspected and evaluated in the same manner as described above.

[0128] After observing the coating film, a joint was obtained in the same manner as described above. The die shear strength of the obtained joint was evaluated in the same manner as described above.

[0129]

[0130] 1...First component, 1a...First base, 1b...First metal layer, 2...Sintered body, 3...Second component, 3a...Second base, 3b...Second metal layer, 4...Semiconductor element, 4a...Base of semiconductor element, 4b...Metal layer of semiconductor element, 5...Lead frame, 5a...Base, 5b...Metal layer, 6...Mold resin, 7...Wire, 8...Lead frame, 8a...Base, 8b...Metal layer, 100...Bonded body, 200...Semiconductor device.

Claims

1. A bonding metal paste comprising metal particles, a dispersion medium, and a reducing agent, wherein the reducing agent comprises polyethylene glycol and compound A having at least one group selected from the group consisting of an amino group, a carboxyl group, and an acetylene group, and a hydroxyl group in its molecule.

2. The bonding metal paste according to claim 1, wherein the metal particles are surface-treated with a fatty acid having 12 to 18 carbon atoms.

3. The bonding metal paste according to claim 1, wherein compound A comprises at least one selected from the group consisting of triethanolamine, diethanolamine, monoethanolamine, bis(2-hydroxyethyl)iminotris(hydroxymethyl)methane, hydroxyacetic acid, and acetylene alcohol-based surfactants.

4. The bonding metal paste according to claim 1, wherein the metal particles include sub-micro copper particles having a volume average particle size of 0.01 μm or more and 0.8 μm or less, and micro copper particles having a volume average particle size of 2 μm or more and 50 μm or less.

5. The bonding metal paste according to claim 4, wherein the micro copper particles are in the form of flakes.

6. A method for manufacturing a bonded body, comprising: a step of preparing a laminate in which a first member, a bonding metal paste according to any one of claims 1 to 5, and a second member are laminated in this order; and a sintering step of sintering the bonding metal paste in the laminate.

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

8. A joining body comprising a first member, a second member, and a sintered body of a joining metal paste according to any one of claims 1 to 5 for joining the first member and the second member.

Images