Bonded body, metal paste for bonding, and method for manufacturing bonded body

Abstract

This bonded body comprises: a first member having a metal layer; a second member; and a sintered body of a metal paste for bonding that bonds the metal layer and the second member. The bonding coverage of the sintered body with respect to the metal layer, as determined from formula (I) below using a cross-sectional image of the bonded body observed with a scanning electron microscope, is 65% or more. (I): Bonding coverage (units: %) = 100 × [total length of contacting portion between the sintered body and the metal layer in the cross-sectional image] / [length of interface between the metal layer and the sintered body in the cross-sectional image]

Description

Joint, metal paste for joining, and method for manufacturing the joint.

[0001] This disclosure relates to a joint, a metal paste for joining, and a method for manufacturing a joint.

[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 bonding power semiconductors, LSIs, etc.

[0003] However, due to factors such as the increased operating temperature resulting from higher capacitance and space-saving semiconductor devices, and the strengthening of RoHS regulations, metal paste containing copper particles has been proposed as an alternative to high-lead solder (see, for example, Patent Document 1). In this method, a sintered body of the metal paste is formed by sintering it in contact with a metal layer provided on the surface of the members to be joined. At the same time, a metal bond is formed at the interface between the sintered body and the metal layer, so that the sintered body and the metal layer are firmly bonded together and the members are joined. Therefore, with the above-mentioned metal paste, it is possible to increase the mechanical strength and reliability of the joining layer while keeping material costs low.

[0004] Japanese Patent Publication No. 2008-244242

[0005] In recent years, as semiconductor elements and other components have become smaller, the bonding area in bonded structures has also decreased, creating a need for further improvements in the bonding strength of these structures.

[0006] Therefore, the present disclosure aims to provide a joint with excellent bonding strength, a bonding metal paste capable of forming such a joint, and a method for manufacturing a joint using such bonding metal paste.

[0007] The inventors of this disclosure have found that in conventional methods using metal paste for joining, fracture (interfacial fracture) is likely to occur at the interface between the joining layer (sintered body) and the metal layer in the joined body. From the viewpoint of suppressing the above-mentioned interfacial fracture, they conducted further studies and arrived at this disclosure.

[0008] Some aspects of this disclosure relate to the following [1] to [8]. [1] A joint comprising a first member having a metal layer, a second member, and a sintered body of a bonding metal paste for joining the metal layer and the second member, wherein the bonding adhesion rate of the sintered body to the metal layer, determined from the following formula (I) using a cross-sectional image of the joint observed with a scanning electron microscope, is 65% or more. Bonding adhesion rate (unit: %) = 100 × [total length of the contact portion between the sintered body and the metal layer in the cross-sectional image] / [length of the interface between the metal layer and the sintered body in the cross-sectional image] ... (I) [2] The joint according to [1], wherein the maximum height roughness Rz and the average length RSm of the roughness curve elements of the surface forming the interface in the metal layer are 1 to 40 nm and 100 to 600 nm, respectively. [3] The bonded body according to [1] or [2], having a contact portion in which the length of the contact portion between the sintered body and the metal layer in the cross-sectional image is 1.05 μm or more. [4] A bonding metal paste containing metal particles and a dispersion medium, wherein the metal particles have a BET specific surface area of ​​3.5 to 7.5 m². ２ A bonding metal paste comprising 5% by mass or more of a group of copper particles at a density of / g. [5] The bonding metal paste according to [4], wherein the 10% cumulative particle diameter, 50% cumulative particle diameter, and 90% cumulative particle diameter in the volume-based cumulative particle size distribution of the group of copper particles are 100-250 nm, 250-450 nm, and 400-750 nm, respectively. [6] The metal particles have a BET specific surface area of ​​0.1-1.5 m². ２ A bonding metal paste according to [4] or [5], further comprising a second group of copper particles at 1 / g. [7] A bonding metal paste according to any one of [4] to [6], further comprising a reducing agent. [8] A method for manufacturing a bonded body, comprising the steps of: preparing a laminate in which a first member having a metal layer, a bonding metal paste according to any one of [4] to [7], and a second member are laminated in this order; and joining the metal layer and the second member via a sintered body of the bonding metal paste by sintering the bonding metal paste in the laminate.

[0009] According to this disclosure, it is possible to provide a joint with excellent bonding strength, a bonding metal paste capable of forming said joint, and a method for manufacturing said joint using said bonding metal paste.

[0010] This is a schematic cross-sectional view showing a joint of one embodiment. This is a schematic diagram of a cross-sectional image of the joint of Figure 1 as observed with a scanning electron microscope. This is a binarized image of a scanning electron microscope image showing the interface between the metal layer and the sintered body in the joint cross-section of the joint of Example 3c. This is a binarized image of a scanning electron microscope image showing the interface between the metal layer and the sintered body in the joint cross-section of the joint of Comparative Example 2c.

[0011] The following describes several embodiments of this disclosure, but this disclosure is not limited thereto. In the embodiments described below, components (including elemental steps, etc.) are not essential unless they are clearly essential in principle, as specifically stated. The same applies to numerical values ​​and their ranges, and these do not unduly limit this disclosure.

[0012] In this disclosure, the term "process" includes not only independent processes but also processes that are indistinguishable from other processes as long as their intended function is achieved. The term "layer" includes not only structures that are formed over the entire surface when viewed as a plan view, but also structures that are formed in only a part of the surface.

[0013] In this disclosure, numerical ranges indicated using "~" represent a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. Furthermore, unless otherwise explicitly stated, the units of the numbers before and after "~" are the same. In numerical ranges described in stages within this disclosure, the upper or lower limit of one stage of the numerical range may be replaced by the upper or lower limit of another stage of the numerical range, or by the values ​​shown in the examples. In this disclosure, for example, "10 or more" means 10 and numbers greater than 10, and this applies even if the numbers are different. Similarly, for example, "10 or less" means 10 and numbers less than 10, and this applies even if the numbers are different.

[0014] In the present disclosure, the content of each component in the composition means the total content of the plurality of substances corresponding to each component in the composition, unless otherwise specified, when there are a plurality of substances corresponding to each component in the composition. In the present disclosure, the "solid content" refers to the components remaining after removing the dispersion medium contained in the metal paste for bonding, and includes components that are liquid, syrup-like, or wax-like at room temperature (around 25°C). The "solid content" in the present disclosure may be read as "non-volatile content". In this case, the "non-volatile content" refers to substances that volatilize at a temperature of 200°C or lower contained in the metal paste for bonding.

[0015] <Metal paste for bonding> A metal paste for bonding according to one embodiment contains metal particles and a dispersion medium. The metal particles contain 5 mass% or more of a group of copper particles having a BET specific surface area of 3.5 to 7.5 m ２ / g.

[0016] The above metal paste for bonding is a metal paste used for bonding members. By heating and sintering the metal paste in a state where it is interposed between the opposing members, the members can be bonded via the sintered body of the metal paste. According to the metal paste for bonding having the above configuration, peeling (interface fracture) can be suppressed in the vicinity of the interface between the sintered body and the metal layer in the bonded body, and a bonded body having excellent bonding strength can be formed.

[0017] Hereinafter, each component used in the metal paste for bonding of the present embodiment will be described in more detail.

[0018] (Metal particles) The metal particles of the present embodiment contain 5 mass% or more of a group of copper particles (hereinafter, may be referred to as "first group of copper particles") having a BET specific surface area of 3.5 to 7.5 m ２ / g.

[0019] The first group of copper particles is composed of copper particles. In the present disclosure, copper particles refer to particles containing copper as a main component. The content ratio of copper in the copper particles is, for example, 80 mass% or more. The content ratio of copper in the copper particles may be 85 mass% or more, 90 mass% or more, 95 mass% or more, 99 mass% or more, or 100 mass%.

[0020] The BET specific surface area of the first copper particle group is 3.5 to 7.5 m ２ / g. From the viewpoint of enhancing the effect of improving the bonding strength, it may be 3.8 m ２ / g or more, or 4.2 m ２ / g or more, and may be 7.0 m ２ / g or less, 6.0 m ２ / g or less, 5.5 m ２ / g or less, 5.2 m ２ / g or less, or 4.8 m ２ / g or less, and may be 3.5 to 7.0 m ２ / g, 3.5 to 6.0 m ２ / g, 3.5 to 5.5 m ２ / g, 3.8 to 5.2 m ２ / g, or 4.2 to 4.8 m ２ / g. In the present disclosure, the BET specific surface area is the specific surface area calculated under the following conditions using the BET (Brunauer-Emmett-Teller) method. [Conditions] Sample pretreatment: Flow N ２ (nitrogen) gas at 25°C for 15 minutes Measurement gas: N ２ (nitrogen) gas Measurement method: One-point method

[0021] From the viewpoint of enhancing the effect of improving the bonding strength, the BET diameter of the copper particles constituting the first copper particle group may be 9​​​​​​​​​​In one embodiment, the 10% cumulative particle diameter (D10), 50% cumulative particle diameter (D50), and 90% cumulative particle diameter (D90) in the volume-based cumulative particle size distribution of the first copper particle group may be 100-250 nm, 250-450 nm, and 400-750 nm, respectively. Here, X% cumulative particle diameter (D(X)) refers to the particle diameter at which the cumulative volume accumulated from the smallest particle diameters in the volume-based cumulative particle size distribution of the first copper particle group becomes X% of the total volume of the first copper particle group. When the first copper particle group has such a particle size distribution, it is easier to obtain a bonded body with superior bonding strength. In this disclosure, the 50% cumulative particle diameter (D50) is also referred to as the volume-average particle size.

[0024] The 10% cumulative particle size (D10) in the volume-based cumulative particle size distribution of the first copper particle group may be 100-250 nm, 100-200 nm, or 100-180 nm, from the viewpoint of enhancing the effect of improving bonding strength.

[0025] The 50% cumulative particle size (D50) in the volume-based cumulative particle size distribution of the first copper particle group may be 260-450 nm, 260-400 nm, or 260-350 nm, from the viewpoint of enhancing the effect of improving bonding strength.

[0026] The 90% cumulative particle size (D90) in the volume-based cumulative particle size distribution of the first copper particle group may be 410-750 nm, 410-700 nm, 410-680 nm, or 410-650 nm, from the viewpoint of enhancing the effect of improving bonding strength.

[0027] To determine the cumulative particle size as described above, a sample can be prepared by dispersing a group of copper particles, either raw material copper particles or copper particles obtained by removing volatile components from a bonding metal paste, in a dispersion medium using a dispersant. This sample can then 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.

[0028] The shape of the copper particles constituting the first group of copper particles is not particularly limited. Examples of copper particle shapes include spherical, lumpy, needle-shaped, flake-shaped, substantially spherical, and aggregates thereof. From the viewpoint of dispersibility and packing, the shape of the copper particles may be spherical, substantially spherical, or flake-shaped, and from the viewpoint of flammability, dispersibility, and mixability, they may be spherical or substantially spherical. In this disclosure, "flake-shaped" includes plate-like shapes such as plate-like and flaky shapes.

[0029] The copper particles constituting the first group of 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 mixability. In this disclosure, "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 determined, for example, from a scanning electron microscope image of the particle.

[0030] The copper particles constituting the first group of copper particles may be treated with a surface treatment agent containing a fatty acid having 10 or more carbon atoms, from the viewpoint of improving dispersibility and stability.

[0031] Examples of fatty acids with 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, and butylheptanoic acid. Tannic 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 octenic acid, butyl undecanoic acid, pentyldecanoic acid, hexylnonanoic acid, palmitic acid, methylpentadecanoic acid, ethyltetradecanoic acid, propyltridecanoic acid, butyldodecanoic acid, pentyl undecanoic 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 include octenic acid, nonenic acid, methylnonenic acid, decenoic acid, undecenoic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, myristoleic acid, pentadecenoic acid, hexadecenoic acid, palmitoleic acid, sapienic acid, oleic acid, vaccenic acid, linoleic acid, linolenic acid, and linolenic acid.

[0032] The fatty acid with 10 or more carbon atoms may be a fatty acid with 10 to 18 carbon atoms, from the viewpoint of dispersion stability of copper particles and oxidation prevention, and may also be lauric acid or decanoic acid, from the viewpoint of exhibiting low-temperature sinterability due to low-temperature decomposition. The fatty acid with 10 or more carbon atoms may be used individually or in combination of two or more types.

[0033] The amount of surface treatment agent applied may be an amount that adheres to the surface of the copper particles in one to three molecular layers. This amount depends on the number of molecular layers (n) attached to the surface of the copper particles and the specific surface area (A) of the copper particles. ｐ ) (Unit: m) ２ ( / g) and the molecular weight (M) of the surface treatment agent. ｓ ) (unit: g / mol) and the minimum coverage area (S) of the surface treatment agent. Ｓ ) (Unit: m) ２ ( / item) and Avogadro's number (N) Ａ ) (6.02 x 10 ２３ It can be calculated from the number of units. Specifically, the amount of surface treatment agent processed is: Amount of surface treatment agent processed (unit: mass%) = {(n・A ｐ ・M ｓ ) / (S Ｓ ・N Ａ +n・A ｐ ・M ｓ It is calculated according to the formula )} × 100%. The minimum coverage area of ​​the surface treatment agent is 2.05 × 10 if the surface treatment agent is a straight-chain saturated fatty acid. －１９ I understand ２ It is one molecule. For 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 Ueeda, Sumio Inafuku, Iwao Mori, 40(2), 1992, pp. 114-117).

[0034] The amount of surface treatment agent used may be 0.1 to 5% by mass, 0.5 to 4% by mass, 1 to 3.5% by mass, or 1 to 3.0% by mass, based on the mass of copper particles having the surface treatment agent, from the viewpoint of stability and sinterability.

[0035] From the viewpoint of enhancing the effect of improving bonding strength, the content of the first group of copper particles in the metal particles may be 10% by mass or more, 30% by mass or more, 50% by mass or more, or 70% by mass or more, based on the total mass of the metal particles, or it may be 100% by mass or less, 95% by mass or less, or 90% by mass or less. From the above viewpoint, the content of the first group of copper particles in the metal particles may be 5 to 100% by mass, 10 to 95% by mass, 30 to 90% by mass, 50 to 90% by mass, or 70 to 90% by mass, based on the total mass of the metal particles.

[0036] The content of the first group of copper particles may be 5 to 100% by mass, 10 to 95% by mass, 30 to 90% by mass, 50 to 90% by mass, or 70 to 90% by mass, based on the total solid content of the bonding metal paste, from the viewpoint of enhancing the effect of improving bonding strength.

[0037] The first group of copper particles can be manufactured by known and conventional methods to achieve the specific surface area described above. Alternatively, commercially available copper particles can be prepared by classification or other means.

[0038] The metal particles have a BET specific surface area of ​​0.1 to 1.5 m². ２ The material may further contain a second group of copper particles, which is concentrated at a concentration of / g. When the metal particles contain this second group of copper particles, it is easier to reduce in-plane volume shrinkage and void formation in the sintered body when sintered under no pressure or under pressure. This tends to result in higher bonding strength in the joined body.

[0039] The BET specific surface area of ​​the second group of copper particles is set to 0.3 m² from the viewpoint of enhancing the effect of improving bonding strength. ２ It may be 1.3 m or more ２ / g or less or 1.0m ２ It may be less than or equal to / g. From the above viewpoint, the BET specific surface area of ​​the second group of copper particles is 0.1 to 1.3 m². ２ / g, 0.3-1.3m ２ / g, 0.1-1.0m ２ / g or 0.3-1.0m ２ / g is also acceptable.

[0040] The 50% cumulative particle size (D50) of the second copper particle group may be, for example, 2 to 50 μm. The 50% cumulative particle size (D50) of the second copper particle group may be 3 μm or more, 20 μm or less, 15 μm or less, or 10 μm or less, and may be 3 to 20 μm, 3 to 15 μm, or 3 to 10 μm.

[0041] The shape and aspect ratio of the copper particles constituting the second group of copper particles are not particularly limited and may be the same as those of the copper particles constituting the first group of copper particles.

[0042] In one embodiment, the copper particles constituting the second group of copper particles may be flake-shaped. By using flake-shaped copper particles, the second group of copper particles oriented substantially parallel to the joint surface after the application of the metal paste, which tends to suppress volume shrinkage of the sintered body, reduce cracking after drying, and improve the joint strength of the joint. The aspect ratio of the flake-shaped copper particles may be greater than 2, and may be 4 or more, 6 or more, 10 or more, or 50 or more. The aspect ratio of the flake-shaped copper particles may be 100 or less.

[0043] The content of the second group of copper particles in the metal particles may be 5% by mass or more, 9% by mass or more, or 12% by mass or more, based on the total mass of the metal particles, and may be 40% by mass or less, 30% by mass or less, or 20% by mass or less, or 5 to 40% by mass, 9 to 30% by mass or 12 to 20% by mass.

[0044] The content of the second group of copper particles may be 5 to 40% by mass, 9 to 30% by mass, or 12 to 20% by mass, based on the total solid content of the bonding metal paste, from the viewpoint of enhancing the effect of improving bonding strength.

[0045] While there are no particular limitations on whether or not the copper particles constituting the second group of copper particles are treated with a surface treatment agent, from the viewpoint of dispersion stability and oxidation resistance, the copper particles constituting the second group of copper particles may be treated with a surface treatment agent containing a fatty acid having 10 or more carbon atoms as described above.

[0046] The amount of surface treatment agent applied to the copper particles constituting the second group of copper particles may be one molecular layer or more on the particle surface. This amount of surface treatment agent varies depending on the BET specific surface area of ​​the second group of 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 may be 0.1 to 15% by mass, 1 to 15% by mass, 5 to 15% by mass, or 8 to 12% by mass, based on the mass of the copper particles having the surface treatment agent. The BET specific surface area of ​​the second group of copper particles, the molecular weight of the surface treatment agent, and the minimum coverage area of ​​the surface treatment agent can be calculated by the method described above.

[0047] Commercially available products can be used as the second group of copper particles. Examples of commercially available products for the second group of copper particles include MA-05KFD (Mitsui Mining & Smelting), MA-C08JF (Mitsui Mining & Smelting), 3L3 (Fukuda Metal Foil & Powder Industry), and 4L3 (Fukuda Metal Foil & Powder Industry).

[0048] The metal particles have a BET specific surface area of ​​2.0 to 3.0 m². ２ A third group of copper particles, which is / g, may further be included. The BET specific surface area of ​​the third group of copper particles is 2.2 to 3.0 m². ２ / g or 2.5-3.0m ２ / g is also acceptable.

[0049] The BET diameter of the third copper particle may be 170–270 nm, 190–250 nm, or 200–250 nm.

[0050] The 50% cumulative particle size (D50) of the third copper particle group may be 250–600 nm, 250–500 nm, or 300–500 nm.

[0051] The shape and aspect ratio of the copper particles constituting the third group of copper particles are not particularly limited and may be the same as those of the copper particles constituting the first group of copper particles.

[0052] The copper particles constituting the third group of copper particles may be treated with a surface treatment agent. The type and amount of surface treatment agent used are the same as in the case of the first group of copper particles.

[0053] The content of the third group of copper particles in the metal particles may be 5 to 80% by mass, 10 to 65% by mass, or 15 to 50% by mass, based on the total mass of the metal particles. The content of the third group of copper particles may be 5 to 80% by mass, 10 to 70% by mass, or 15 to 50% by mass, based on the total solid content of the bonding metal paste.

[0054] The metal particles may consist solely of copper particles, or they may contain metal particles other than copper. For example, the metal particles may include particles of zinc, gold, palladium, silver, nickel, platinum, brass, manganese, tin, antimony, indium, aluminum, vanadium, etc. The content of other metal particles may be less than 5% by mass, 3% by mass or less, or 0% by mass, based on the total mass of the metal particles.

[0055] (Dispersion medium) Examples of dispersion mediums include monohydric and polyhydric alcohols such as pentanol, hexanol, heptanol, octanol, decanol, dihydroterpineol, terpineol, and isobornylcyclohexanol (MTPH); 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, and dipropylene glycol Examples include ethers such as 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.

[0056] 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.

[0057] The dispersion medium can be used individually or in combination of two or more types.

[0058] The metal paste for bonding may further contain a reducing agent from the viewpoint of improving storage stability and suppressing a decrease in sintering performance. Examples of reducing agents include polyethylene glycols such as polyethylene glycol 200, polyethylene glycol 300, and polyethylene glycol 400. These can be used individually or in combination of two or more.

[0059] Other reducing agents besides polyethylene glycol 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.

[0060] The content of the reducing agent in the metal paste for joining may be 1.6 parts by mass or more, 1.8 parts by mass or more, 2 parts by mass or more, or 4 parts by mass or more per 100 parts by mass of metal particles, from the viewpoint of suppressing sintering defects and enhancing the effect of improving joining strength, and may be 10 parts by mass or less, 9 parts by mass or less, or 8 parts by mass or less, from the viewpoint of suppressing a decrease in joining strength due to an excess of reducing agent. From the above viewpoint, the content of the reducing agent may be 1.6 to 10 parts by mass, 1.8 to 9 parts by mass, 2 to 8 parts by mass, or 4 to 8 parts by mass per 100 parts by mass of metal particles.

[0061] The bonding metal paste of this embodiment may further contain additives such as dispersants, surface protectants, thickeners, and thixotropic agents, as needed.

[0062] If the bonding metal paste contains additives, the amount of additives that are non-volatile or non-degradable at temperatures below 200°C 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, from the viewpoint of suppressing a decrease in the sinterability of the bonding metal paste.

[0063] The above-mentioned bonding metal paste is obtained by mixing the above-mentioned metal particles, dispersion medium, and optional additives such that the content of the first copper particle group is 5% by mass based on the total mass of the metal particles. That is, the method for producing the bonding metal paste according to one embodiment includes a mixing step of mixing the above-mentioned metal particles, dispersion medium, and optional additives such that the content of the first copper particle group is 5% by mass based on the total mass of the metal particles. The mixing step is a step of mixing the first copper particle group, dispersion medium, optional other metal particles, and optional additives, and may be a step of mixing the first copper particle group, second copper particle group, dispersion medium, optional other metal particles, and optional additives, or a step of mixing the first copper particle group, second copper particle group, third copper particle group, dispersion medium, optional other metal particles, and optional additives. After mixing each component, a stirring treatment may be performed. The maximum particle size of the dispersion liquid may be adjusted by a classification operation for the bonding metal paste.

[0064] 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.

[0065] 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.

[0066] Classification operations can be carried out, for example, by filtration, natural sedimentation, or centrifugal separation. Examples of filters for filtration include water combs, metal mesh, metal filters, and nylon mesh.

[0067] The bonding metal paste may be adjusted to a viscosity suitable for the printing and coating method. The Casson viscosity of the bonding metal paste at 25°C may be 0.05 to 2.0 Pa·s, or 0.06 to 1.0 Pa·s. The Casson viscosity at 25°C can be measured using a viscoelasticity measuring device.

[0068] <Jointed Body> Figure 1 is a schematic cross-sectional view showing a jointed body according to one embodiment. The jointed body 10 in Figure 1 comprises a first member 1 having a metal layer 1b, a second member 3, and a sintered body 2 of joining metal paste that joins the metal layer 1b and the second member 3. The metal layer 1b and the sintered body 2 are in contact with each other and form an interface S. In the first member 1, the metal layer 1b is provided on the base portion 1a. Although not shown, the second member 3 may have a metal layer similar to the metal layer 1b on the surface that is in contact with the sintered body 2.

[0069] (First and Second Components) Examples of the first component 1 and the second component 3 include semiconductor elements, lead frames, metal plate-attached ceramic substrates (e.g., DBC), substrates for mounting semiconductor elements such as LED packages, copper ribbons, metal blocks, power supply components such as terminals, heat sinks, and water cooling plates. Examples of semiconductor elements include power modules consisting of diodes, rectifiers, thyristors, MOS gate drivers, power switches, power MOSFETs, IGBTs, Schottky diodes, fast recovery diodes, etc., logic circuits, sensors, analog integrated circuits, semiconductor lasers, oscillators, amplifiers, LEDs, LED modules, MOS-FETs, etc.

[0070] At least one of the first and second members may be a semiconductor element. When at least one of the first and second members is a semiconductor element, the junction becomes a semiconductor device.

[0071] [Metal Layer] Examples of metals constituting the metal layer 1b 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 used in alloys, in addition to the above metals, include zinc, manganese, aluminum, beryllium, titanium, chromium, iron, and molybdenum. The metal layer may be, for example, a layer made of metal plating (plating layer), or a layer formed by metal vapor deposition (metal vapor deposition layer). The metal layer may also be a layer made of metal foil, metal plate, etc.

[0072] The maximum height roughness Rz of the surface (the surface on the sintered body 2 side) forming the interface S in the metal layer 1b may be 0.1 to 60 nm, 1 nm or more, 2 nm or more, or 3 nm or more, 40 nm or less, 20 nm or less, or 10 nm or less, or 1 to 40 nm, 2 to 20 nm, or 3 to 10 nm.

[0073] The average length RSm of the roughness curve elements of the surface (the surface on the sintered body 2 side) forming the interface S in the metal layer 1b may be 10 to 800 nm, 100 nm or more, 150 nm or more, or 200 nm or more, 600 nm or less, 550 nm or less, or 500 nm or less, or 100 to 600 nm, 150 to 550 nm, or 200 to 500 nm.

[0074] In this disclosure, the maximum height roughness Rz refers to the maximum height roughness measured in accordance with the method specified in the JIS standard (JIS B 0601-2001). The average length RSm of the roughness curve elements refers to the average length of the roughness curve elements measured in accordance with the method specified in the JIS standard (JIS B 0601-2001). The maximum height roughness Rz and the average length RSm of the roughness curve elements can be measured, for example, using a nanosearch microscope (Shimadzu Corporation's "SFT-3500").

[0075] The thickness of the metal layer 1b may be 100 to 1000 nm, 200 to 900 nm, or 300 to 800 nm.

[0076] (Sintered body) Sintered body 2 is a sintered body of a bonding metal paste. The bonding metal paste contains, for example, copper particles and a dispersion medium.

[0077] In one embodiment, the bonding metal paste may be the bonding metal paste of the above embodiment. In this case, the bonded body tends to have excellent bonding strength.

[0078] When the bonding metal paste is the bonding metal paste of the above embodiment, a significant improvement in bonding strength tends to be obtained when the maximum height roughness Rz of the surface forming the interface S in the metal layer 1b is in the range of 1 to 40 nm, a more significant improvement in bonding strength tends to be obtained when Rz is in the range of 2 to 20 nm, and an even more significant improvement in bonding strength tends to be obtained when Rz is in the range of 3 to 10 nm.

[0079] When the bonding metal paste is the bonding metal paste of the above embodiment, if the average length RSm of the surface roughness curve elements forming the interface S in the metal layer 1b is in the range of 100 to 600 nm, the bonding adhesion rate described later tends to be higher, and a significant improvement in bonding strength tends to be obtained. This tendency becomes stronger when the RSm is in the range of 150 to 550 nm, and even stronger when the RSm is in the range of 200 to 500 nm.

[0080] The thickness of the layer (bonding layer) made of the sintered body 2 may be 10 to 100 μm, 20 to 100 μm, or 20 to 90 μm.

[0081] (Bonding Adhesion Rate) Figure 2 is a schematic diagram of a cross-sectional image of the bonded body 10 as observed by a scanning electron microscope (SEM). In one embodiment, the bonding adhesion rate of the sintered body 2 to the metal layer 1b, which can be determined from the following formula (I) using the above cross-sectional image, is 65% or more. Bonding Adhesion Rate (unit: %) = 100 × [Total length L2 of the contact portion C between the sintered body 2 and the metal layer 1b in the cross-sectional image] / [Length L1 of the interface S between the metal layer 1b and the sintered body 2 in the cross-sectional image] ... (I)

[0082] In Figure 2, the interface S has contact portions C. Specifically, the sintered body 2 and the metal layer 1b are in contact at three locations, forming contact portions C1, C2, and C3 at each location. If the lengths of these contact portions are L2a, L2b, and L2c, respectively, the bonding adhesion rate (in %) of the joined body 10 can be calculated as follows: Bonding adhesion rate (in %) = 100 × (L2a + L2b + L2c) / L1

[0083] Cross-sectional images of the joint can be obtained, for example, by the following procedure. First, a sample for cross-sectional observation is prepared by embedding the joint in resin (e.g., epoxy resin). Next, the obtained sample for cross-sectional observation is cut in the lamination direction of the joint, and the resulting cross-section is polished. Then, the region including the interface between the metal layer and the sintered body in the polished cross-section is photographed using a SEM. For cutting the joint, for example, a small precision cutting machine (RefineTech Co., Ltd., product name: Refine Saw) can be used. For polishing the cross-section, for example, an automatic polishing machine (RefineTech Co., Ltd., product name: Refine Polisher) can be used. The SEM image acquisition conditions are, for example, detector: secondary electron detector (SED), acceleration voltage: 15.0 kV, magnification: 5000x, field of view: 25.4 μm × 18.0 μm. Also, when acquiring SEM images, the working distance (WD) is preferably as close to 10.0 as possible, but may be between 9.5 and 10.0.

[0084] The above cross-sectional images may be taken at multiple cross-sections and at multiple locations within a single cross-section. The bonding adhesion rate may be calculated from the obtained multiple cross-sectional images using the above formula (I), and the average value of these may be used as the bonding adhesion rate of the joined body. In this embodiment, the above cross-sectional images are acquired at least at two locations per cross-section in at least one cross-section, and the bonding adhesion rate is calculated from the obtained multiple cross-sectional images (at least two) using the above formula (I), and the average value of these is used as the bonding adhesion rate of the joined body.

[0085] A joint with a bonding adhesion rate of 65% or more exhibits excellent bonding strength between the metal layer and the second member. From the viewpoint of superior bonding strength, the bonding adhesion rate may be 68% or more or 70% or more. The upper limit of the bonding adhesion rate is not particularly limited and may be 100% or less, 90% or less, or 80% or less. Therefore, the bonding adhesion rate may be 65-100%, 68-90%, or 70-80%.

[0086] The bonding adhesion rate can be adjusted, for example, by the composition of the metal paste used to form the sintered body 2, the type of metal layer 1b, and the surface shape. For example, by using the bonding metal paste of the above embodiment as the metal paste, a bonded body having a bonding adhesion rate within the above range can be easily obtained.

[0087] The average length L2 of the contact portion C between the sintered body 2 and the metal layer 1b in the above cross-sectional image may be 500 nm or more, 600 nm or more, 700 nm or more, 800 nm or more, 900 nm or more, or 1000 nm or more, from the viewpoint of superior bonding strength. The average length L2 may be 5000 nm or less, 4000 nm or less, 3000 nm or less, 2500 nm or less, or 2000 nm or less, and may be 500 to 5000 nm, 600 to 5000 nm, 700 to 5000 nm, 800 to 5000 nm, 900 to 5000 nm, 1000 to 5000 nm, 1000 to 4000 nm, or 1000 to 3000 nm.

[0088] The jointed body 10 may have contact portions with a length L2 of 0.75 μm or more, from the viewpoint of superior joint strength. The ratio of the contact portions to the interface S (100 × [total length of contact portions with a length L2 of 0.75 μm or more] / [length L1 of interface S]) may be 50% or more, 60% or more, or 65% or more, and may be 100% or less, 90% or less, or 80% or less, and may be 50-100%, 60-90%, or 70-80%. When the above ratio is 50% or more, there is a tendency to obtain even better joint strength.

[0089] The jointed body 10 may have a contact portion with a length L2 of 1.05 μm or more, from the viewpoint of superior joint strength. The ratio of the contact portion to the interface S (100 × [total length of the contact portion with a length L2 of 1.05 μm or more] / [length L1 of the interface S]) may be greater than 0%, 3% or more, 5% or more, 10% or more, or 30% or more, and may be 100% or less, 90% or less, or 80% or less, and may be greater than 0% and 100% or less, 3 to 100%, 5 to 100%, 10 to 90%, or 30 to 80%. When the above ratio is 5% or more, there is a tendency to obtain even better joint strength.

[0090] <Method for Manufacturing a Joined Body> A method for manufacturing a joined body according to one embodiment comprises the steps of: preparing a laminate in which a first member having a metal layer, the joining metal paste of the above embodiment, and a second member are stacked in this order; and joining the metal layer and the second member via the sintered body of the joining metal paste by sintering the joining metal paste in the laminate. By this method, the joined body of the above embodiment can be obtained. In the following description, descriptions that overlap with the joined body of the above embodiment will be omitted.

[0091] The above-mentioned 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 having the metal layer described above on the bonding metal paste. In this case, a laminate can be prepared in which the bonding metal paste and the second member are laminated in this order on the side of the metal layer of the first member.

[0092] 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 the bonding metal 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, and electrodeposition coating. 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.

[0093] The joining metal paste provided on the second member may be dried as appropriate from the viewpoint of suppressing flow and void formation during sintering. The drying conditions can be the same as those for the drying method of the sintered body described above.

[0094] 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.

[0095] In the sintering process, the bonding metal paste is sintered by heat treatment of the laminate. The heating temperature can be, for example, 230 to 400°C. The heating atmosphere can be, for example, an oxygen-free atmosphere, which 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 can be 0.1 volume percent or less, 0.01 volume percent or less, or 0.001 volume percent or less. As a result, the metal layer and the second member are bonded via the sintered body of the bonding metal paste, and the bonded body of the above embodiment is obtained.

[0096] In this embodiment, by using the bonding metal paste of the above embodiment, a bonded body with excellent bonding strength can be obtained. Pressurization may be applied during sintering. For example, by heating the laminated body while applying a pressure of 10 to 30 MPa to the laminated body, a bonded body with even better bonding strength can be obtained.

[0097] The present disclosure will be described in more detail below with reference to examples. However, the present disclosure is not limited to these examples.

[0098] <Preparation of materials> The following materials were prepared: (Metal particles) - Copper particle A (first group of copper particles): Copper particles (spherical, BET specific surface area: 4.5 m²) ２ / g, BET diameter: 150 nm, volume average particle size (D50): 278 nm, D10: 159 nm, D90: 522 nm, surface treatment agent: lauric acid, amount of surface treatment agent applied: 2.8 mass%) ・Copper particles B (first group of copper particles): copper particles (spherical, BET specific surface area: 7.2 m² ２ / g, BET diameter: 100 nm, volume average particle size (D50): 256 nm, D10: 124 nm, D90: 632 nm, surface treatment agent: lauric acid, amount of surface treatment agent applied: 2.0 mass%) ・Copper particles C (second copper particle group): copper particles (flake-like, BET specific surface area: 0.73 m²) ２ ( / g, volume-average particle size: 5 μm) • Copper particle D (second group of copper particles): Copper particles (spherical, BET specific surface area: 0.53 m²) ２ ( / g, volume average particle size: 10 μm) • Copper particle E (third group of copper particles): Copper particles (spherical, BET specific surface area: 2.8 m²) ２ ( / g, BET diameter: 230 nm, volume-average particle size: 276 nm) (Dispersion medium) Dihydroterpineol (Reducing agent) Polyethylene glycol 200 (Other additives) Decanoic acid

[0099] <Preparation of bonding metal paste> (Example 1) 12.8 parts by mass of dihydroterpineol as a dispersion medium, 10.0 parts by mass of copper particles A and 53.8 parts by mass of copper particles E as metal particles, 4.5 parts by mass of polyethylene glycol 200 as a reducing agent, and 0.8 parts by mass of decanoic acid as other additives were mixed in a poly bottle to obtain a dispersion. 11.3 parts by mass of copper particles C were added to this dispersion and stirred with a spatula until no dry powder remained. The poly bottle was tightly sealed and stirred for 2 minutes to obtain bonding metal paste A of Example 1.

[0100] (Examples 2-5 and Comparative Examples 1-3) Except for changing the type and amount (parts by mass) of metal particles and the amount (parts by mass) of dispersion medium and additives as shown in Tables 1 and 2, bonding metal pastes B-H of Examples 2-5 and Comparative Examples 1-3 were obtained in the same manner as in Example 1.

[0101]

[0102]

[0103] <Preparation of Joints> (Examples 1a to 5a) Using the obtained joining metal pastes A to E, a joint was prepared under the following joining condition 1.

[0104] [Bonding Condition 1] A bonding metal paste was stencil printed onto an AMB substrate (manufactured by AIN Co., Ltd., size: 34 mm x 29 mm x thickness 1.9 mm) using a 100 μm thick stainless steel mask and squeegee with a 5.3 mm x 5.3 mm square opening. The resulting laminate was heated on a hot plate heated to 90°C for 30 minutes in an air atmosphere to dry the bonding metal paste and form a layer (precursor layer) consisting of the dried bonding metal paste.

[0105] A SiC chip (size: 3.15 mm × 4.3 mm × thickness: 200 μm) was prepared with titanium layer, nickel layer, and silver layer in that order from the chip side. The silver layer was formed by sputtering. The maximum height roughness Rz of the silver layer on the side opposite the nickel layer was 0.9 nm, and the average length RSm of the roughness curve elements on the side opposite the nickel layer was 200 to 500 nm. The SiC chip was placed on the precursor layer so that the silver layer was on the AMB substrate side. In this way, a precursor laminate consisting of the AMB substrate, the precursor layer, and the SiC chip was obtained.

[0106] The precursor laminate was pressurized at 20 MPa for 5 minutes using a stainless steel stage and stainless steel head heated to 260°C in a nitrogen atmosphere. This bonded the SiC chip and the silver layer on the AMB substrate via a sintered body, obtaining a bonded structure. During pressurization, a Teflon sheet (1 mm thick, "Teflon" is a registered trademark) was placed between the SiC chip (the side of the SiC chip opposite to the sintered body side) and the stainless steel head.

[0107] (Examples 1b to 5b) Using the obtained bonding metal pastes A to E, a bonded body was prepared under the following bonding conditions 2.

[0108] [Joining Condition 2] The joined body was fabricated in the same manner as in Joining Condition 1, except that the SiC chip was changed to a SiC chip in which a titanium layer / nickel-vanadium alloy layer / silver layer were provided in this order, the silver layer being formed by electroplating, the maximum height roughness Rz of the surface of the silver layer opposite the nickel-vanadium alloy layer being 40 nm, and the average length RSm of the roughness curve elements of the surface of the silver layer opposite the nickel-vanadium alloy layer being 200 to 500 nm.

[0109] (Examples 1c to 5c, Comparative Examples 1c to 3c) Using the obtained bonding metal pastes A to H, a bonded body was prepared under the following bonding conditions 3.

[0110] [Joining Condition 3] The joined body was fabricated in the same manner as in Joining Condition 1, except that the SiC chip was changed to a SiC chip in which a titanium layer / nickel-vanadium alloy layer / silver layer were provided in that order, the silver layer was formed by electroplating, the maximum height roughness Rz of the surface of the silver layer opposite the nickel-vanadium alloy layer was 5.0 nm, and the average length RSm of the roughness curve elements was 200 to 500 nm.

[0111] <Measurement of bonding adhesion rate> Samples for cross-sectional observation were prepared by embedding each bonded body, fabricated under each bonding condition, in epoxy resin. Next, the obtained cross-sectional observation samples were cut in the layering direction of the bonded body, and the resulting cross-sections were polished. Then, the region including the interface between the silver layer and the sintered body in the polished cross-section was photographed using a scanning electron microscope (SEM, SU5000, Hitachi High-Tech Corporation). A Refine Saw (Refine Tech Co., Ltd.) was used to cut the bonded body, and a Refine Polisher (Refine Tech Co., Ltd.) was used to polish the cross-sections. The SEM image acquisition conditions were, for example, acceleration voltage: 15.0 kV, magnification: 5000x, and field of view: 25.4 μm × 18.0 μm. From the obtained cross-sectional image, the length of the interface between the silver layer and the sintered body (L1) and the length of the contact portion between the sintered body and the metal layer (L2) were calculated. The bonding adhesion rate (in %) in the above cross-sectional image was then calculated using the following formula (I'): Bonding adhesion rate (in %) = 100 × (Σ[L2] / L1) ... (I')

[0112] By performing the above operation on one cross-section, cross-sectional images were obtained at two locations per cross-section. The bonding adhesion rate was calculated from the obtained cross-sectional images (two in total) using the above formula (I'), and the average value of these was taken as the bonding adhesion rate of the bonded body. The results are shown in Tables 3 to 5. For reference, cross-sectional images of Example 3c and Comparative Example 2c are shown in Figures 3 and 4. In Figures 3 and 4, the white areas at the interface between the metal layer and the sintered body are the areas where the metal layer and the sintered body are bonded, and the black areas are the void areas.

[0113] <Measurement of Contact Length> Using the cross-sectional images obtained in <Measurement of Bonding Adhesion Rate> above, the length of each contact portion between the sintered body and the metal layer of each fabricated bond was determined. The percentage (in %) of the interface occupied by contact portions with lengths of 0 μm or more but less than 0.25 μm, 0.25 μm or more but less than 0.50 μm, 0.50 μm or more but less than 0.75 μm, 0.75 μm or more but less than 1.05 μm, and 1.05 μm or more was then calculated. The results are shown in Tables 3 to 5.

[0114] <Measurement of Die Shear Strength> For bonded bodies prepared under each bonding condition, a universal bond tester (4000 series, Nordson-DAGE) equipped with a 1 kN load cell was used to measure the die shear strength (MPa) by pressing the SiC chip horizontally at a measurement speed of 500 μm / s and a measurement height of 50 μm. Eleven bonded bodies were prepared from each bonding metal paste, and the die shear strength of these eleven bonded bodies was measured. The average value of the measured values ​​for these eleven bonded bodies was taken as the die shear strength (unit: MPa). The results are shown in Tables 3 to 5.

[0115]

[0116]

[0117]

[0118] 1...First member, 1a, 11a, 12a...Base, 1b, 11b, 12b...Metal layer, 2, 21, 22...Sintered body, 3...Second member, S...Interface, C, C1, C2, C3...Contact portion, L1...Length of interface, L2, L2a, L2b, L2c...Length of contact portion, 10...Jointed body.

Claims

1. A joint comprising a first member having a metal layer, a second member, and a sintered body of a bonding metal paste for joining the metal layer and the second member, wherein the bonding adhesion rate of the sintered body to the metal layer, determined from the following formula (I) using a cross-sectional image of the joint observed with a scanning electron microscope, is 65% or more. Bonding adhesion rate (unit: %) = 100 × [total length of the contact portion between the sintered body and the metal layer in the cross-sectional image] / [length of the interface between the metal layer and the sintered body in the cross-sectional image] ... (I) 2. The bonded body according to claim 1, wherein the maximum height roughness Rz and the average length RSm of the roughness curve elements of the surface forming the interface in the metal layer are 1 to 40 nm and 100 to 600 nm, respectively.

3. The jointed body according to claim 1 or 2, having a contact portion in which the length of the contact portion between the sintered body and the metal layer in the cross-sectional image is 1.05 μm or more.

4. A bonding metal paste containing metal particles and a dispersion medium, wherein the metal particles have a BET specific surface area of ​​3.5 to 7.5 m². ２ A bonding metal paste containing 5% by mass or more of copper particles at a concentration of / g.

5. The bonding metal paste according to claim 4, wherein the 10% cumulative particle size, 50% cumulative particle size, and 90% cumulative particle size in the volume-based cumulative particle size distribution of the copper particle group are 100-250 nm, 250-450 nm, and 400-750 nm, respectively.

6. The metal particles have a BET specific surface area of ​​0.1 to 1.5 m². ２ The bonding metal paste according to claim 4, further comprising a second group of copper particles in the form of / g.

7. The bonding metal paste according to claim 4, further containing a reducing agent.

8. A method for manufacturing a bonded body, comprising the steps of: preparing a laminate in which a first member having a metal layer, a bonding metal paste according to any one of claims 4 to 7, and a second member are laminated in this order; and joining the metal layer and the second member via a sintered body of the bonding metal paste by sintering the bonding metal paste in the laminate.

Images