Bonding paste and bonding material

Abstract

To provide a joining paste that exhibits high joint strength in the joined area and demonstrates reduced susceptibility to the deterioration of joint strength due to thermal cycling; a joining paste that, in addition to these characteristics, ensures excellent printability on the joined part, even when containing a high concentration of metal particles; and a joint body that is less prone to degradation due to thermal cycling.SOLUTION: A joining paste includes metal particles (A) with an average particle size of 100 nm-500 nm, a C20-80 compound (B) with two or more functional groups (b) selected from hydroxy groups, carboxy groups and amino groups, and a dispersion medium (C) with a boiling point of 200°C or higher. There is also provided a joint body where a first joint part and a second joint part are joined together using the joining paste.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a bonding paste and a bonded body. [Background technology]

[0002] Conventionally, solder has been used as a bonding material for bonding metal members together, between a metal member and a semiconductor element, between a metal member and a light-emitting diode (LED) element, etc. In recent years, in the technical field of next-generation power electronics, there has been a demand for devices such as SiC that can operate at high temperatures. As a bonding material for manufacturing such devices, alternative materials to solder are required from the viewpoint of high-temperature operation reliability, and for example, as shown in Patent Documents 1 to 3, bonding materials such as bonding pastes using sinterable metal particles have been proposed.

[0003] Patent Document 1 discloses a bonding material containing metal submicron particles with an average primary particle size of 0.5 to 3.0 μm and metal nanoparticles with an average primary particle size of 1 to 200 nm that are coated with an organic compound having 6 to 8 carbon atoms. However, there is a problem in that the bonding strength at the bonded portion is poor, and the bonding strength decreases with thermal cycling.

[0004] Patent Document 2 discloses a bonding material containing silver nanoparticles with an average primary particle size of 1 to 200 nm that are coated with an organic substance having 8 or less carbon atoms, and a flux component having at least two carboxyl groups. Patent Document 3 discloses a bonding material containing silver fine particles with average primary particle sizes of 17 nm, 85 nm, and 0.6 μm, and a crosslinked interparticle distance-maintaining agent that maintains the distance between the silver fine particles.

[0005] However, even with these bonding materials, there was a problem similar to that of the technology disclosed in Patent Document 1, in that the strength of the bonded portion was poor and the bond strength decreased with thermal cycling. Furthermore, when a bonding paste containing a high concentration of silver nanoparticles was created to achieve a dense and strong bond, it also had the drawback of significantly poor fluidity. As a result, during the process of printing the bonding paste on the bonded body, there were problems such as fading of the printed area and the formation of uncoated areas. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-80147 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-240406 [Patent Document 3] Japanese Patent Application Publication No. 2018-109232 Summary of the Invention [Problem to be solved by the invention]

[0007] The properties required for bonding pastes using metal particles include printability on the parts to be bonded, sufficient bonding strength, and minimal loss of bonding strength after reliability tests such as thermal cycling.

[0008] Therefore, the problem to be solved by the present invention is to provide a bonding paste that has high bonding strength at the bonded portion and suppresses a decrease in bonding strength due to thermal cycling. Furthermore, the problem to be solved by the present invention is to provide a bonding paste that, in addition to the above properties, has excellent printability on the bonded body even if it contains a high concentration of metal particles. Furthermore, the problem to be solved by the present invention is to provide a bonded body that does not deteriorate due to thermal cycling. [Means for solving the problem]

[0009] The present inventors have conducted extensive research to solve the above problems and have arrived at the present invention. A bonding paste according to one embodiment of the present invention is characterized by containing metal particles (A) having an average particle size of 100 nm to 500 nm, a compound (B) having 20 to 80 carbon atoms and having two or more functional groups (b) that are any one type selected from hydroxyl groups, carboxy groups, and amino groups, and a dispersion medium (C) having a boiling point of 200°C or higher.

[0010] The bonding paste according to one aspect of the present invention is characterized in that the number of functional groups is two or three.

[0011] The bonding paste according to one aspect of the present invention is characterized in that the compound (B) has a branched and / or cyclic structure.

[0012] The bonding paste according to one aspect of the present invention is characterized in that the compound (B) has an n-valent hydrocarbon group, where n is the number of the functional groups.

[0013] The bonding paste according to one aspect of the present invention is characterized in that the n-valent hydrocarbon group has 30 to 60 carbon atoms.

[0014] A joining paste according to one embodiment of the present invention is characterized in that the compound (B) contains one or more selected from the group consisting of dimer acid, trimer acid, dimer diol, trimer triol, dimer diamine, and trimer triamine.

[0015] The bonding paste according to one aspect of the present invention is characterized by containing 0.3 to 2.7 parts by mass of the compound (B) relative to 100 parts by mass of the metal particles (A).

[0016] The bonding paste according to one aspect of the present invention is characterized in that the metal particles (A) have an average particle size of 150 nm to 500 nm.

[0017] The bonding paste according to one aspect of the present invention is characterized in that the dispersion medium (C) contains at least one selected from the group consisting of glycol ether-based and diol-based dispersion mediums.

[0018] The bonding paste according to one aspect of the present invention is characterized in that the boiling point of the dispersion medium (C) is 250° C. or higher.

[0019] The bonding paste according to one aspect of the present invention is characterized in that the mass ratio of the metal particles (A) to the mass of the bonding paste is 80 mass % to 95 mass %.

[0020] A bonded body according to one aspect of the present invention is characterized in that a first bonded portion and a second bonded portion are bonded together by the bonding paste. [Effects of the Invention]

[0021] The present invention provides a bonding paste that provides high bonding strength at the bonded portion and that does not decrease with thermal cycling. In addition to these effects, the present invention also provides a bonding paste that has excellent printability. Furthermore, the present invention provides a bonded body that does not deteriorate with thermal cycling, and can exhibit good thermal cycling properties even when a non-plated copper base material, which is difficult to develop bonding strength, is used as the bonded portion. DETAILED DESCRIPTION OF THE INVENTION

[0022] In this specification, "metal particles (A) having an average particle size of 100 nm to 500 nm" may be abbreviated as "metal particles (A)," "compound (B) having 20 to 80 carbon atoms and having two or more functional groups (b) that are any one type selected from hydroxyl groups, carboxy groups, and amino groups" may be abbreviated as "compound (B)," and "dispersion medium (C) having a boiling point of 200°C or higher" may be abbreviated as "dispersion medium (C)."

[0023] The bonding paste of the present invention is characterized by containing metal particles (A) having an average particle size within a predetermined range, a compound (B) having two or more specific functional groups and a carbon number within a predetermined range, and a dispersion medium (C) having a boiling point within a predetermined range. By combining the above, the formation of voids in the coating film is suppressed, resulting in a dense coating film, which can exhibit excellent bonding strength and bonding strength after thermal cycling. Specifically, in the sintering temperature range for particle sizes of about 100 nm to 500 nm, compound (B) exists in a sufficiently liquid state, and a sufficient amount of dispersion medium (C) remains, increasing the fluidity of the coating film and further improving its wettability to the substrate during the sintering stage, resulting in good adhesion.

[0024] <Metal particles (A)> Examples of metals in the metal particles (A) include gold, silver, copper, nickel, chromium, palladium, rhodium, ruthenium, indium, silicon, aluminum, tungsten, molybdenum, platinum, and alloys thereof. Also included are fine particles in which a core is coated with a material different from the core material, specifically, for example, silver-coated copper powder in which a copper core is coated on the surface with silver. Other examples include powders of metal oxides such as silver oxide, indium oxide, tin oxide, zinc oxide, ruthenium oxide, ITO (tin-doped indium oxide), AZO (aluminum-doped zinc oxide), and GZO (gallium-doped zinc oxide), as well as powders surface-coated with these metal oxides. The metals used may be one type or a combination of two or more types.

[0025] The metal particles (A) are preferably selected from copper or silver, since this allows for the production of a bonded body having particularly excellent strength. Furthermore, the metal particles (A) are more preferably silver, since this allows for a wide range of firing temperatures and various firing environments, such as atmospheric pressure, a nitrogen atmosphere, a vacuum, or a reducing atmosphere.

[0026] The metal particles (A) have a specific average particle size range, which allows them to melt or bond together (hereinafter referred to as sintering) at temperatures between 200°C and 350°C, where the joining paste is heated and sintered, and turn into a bulk metal. As a result, the objects to be joined are joined. Hereinafter, the area formed by the sintering of the metal particles (A) between the objects to be joined is referred to as the joining layer.

[0027] In the present invention, it is important to use metal particles (A) having a specific average particle size. As used herein, "average particle size" refers to the 50% cumulative particle size distribution particle size (d50) on a volume basis determined by the measurement method described in the Examples. The d50 of the metal particles (A) is 100 to 500 nm, preferably 150 nm or more, more preferably 180 nm or more, and even more preferably 200 nm or more. Furthermore, the d50 of the metal particles (A) is preferably 450 nm or less, more preferably 350 nm or less.

[0028] The surfaces of the metal particles (A) are preferably coated with an organic component (a). Coating with the organic component (a) is expected to improve the storage stability of the metal particle-containing composition and the bonding paste. Examples of the organic component (a) include fatty acids, aliphatic amines, and aliphatic alcohols. Saturated or unsaturated fatty acids are preferred, saturated or unsaturated fatty acids having 3 to 18 carbon atoms are more preferred, and saturated or unsaturated fatty acids having 6 to 18 carbon atoms are even more preferred. One or more types of organic components (a) may be included.

[0029] The metal particles (A) may be used alone or in combination. Furthermore, if necessary, metal particles other than the metal particles (A) may be used in combination. When metal particles other than the metal particles (A) are used in combination, it is preferable to use metal particles having an average particle size of more than 500 nm in combination.

[0030] <Compound (B)> Next, the compound (B) will be described. Generally, metal particles are powder, so if the compound (B) is not contained, as the dispersion medium evaporates from the bonding paste, it becomes difficult to form an interface with the bonded parts. However, by coexisting the compound (B) of the present invention, even after a part or all of the dispersion medium (C) has volatilized, the composition can behave as a liquid metal particle-containing composition, making it easier to form a good bonded interface that is integrated with the bonded parts.

[0031] Compound (B) has two or more functional groups selected from hydroxyl groups, carboxy groups, and amino groups (hereinafter, these functional groups will be referred to as "functional groups (b)") in the molecule, and has a structure containing 20 to 80 carbon atoms.

[0032] The number of carbon atoms in compound (B) includes the number of carbon atoms in functional group (b). Therefore, if functional group (b) in compound (B) is a carboxy group, the number of carbon atoms in compound (B) includes the number of carbon atoms in this carboxy group.

[0033] In compound (B), the skeleton (partial structure) excluding functional group (b) is an organic residue, but is preferably a hydrocarbon group or a group in which multiple hydrocarbon groups are linked by a linking group containing a heteroatom. Examples of such linking groups containing a heteroatom include an -O- group (ether group), a -C(=O)- group (carbonyl group), a -C(=O)-O- group (also called an ester group or oxycarbonyl group), and a -C(=O)-NH- group (also called an amide group or iminocarbonyl group). Compound (B) preferably does not have any functional groups other than functional group (b).

[0034] The state of the compound (B) is not particularly limited, but it is preferably liquid in the temperature range of 200° C. to 350° C., which is the temperature range in which the bonding paste of the present invention is fired. The compound (B) may be solid or liquid at room temperature (25° C.), but it is more preferably liquid at room temperature so that it can be uniformly dispersed in the bonding paste and act effectively.

[0035] If compound (B) has the property of being liquid in the above temperature range, it is expected that the wettability at the bonding interface with the bonded parts will increase, and the contact area will increase. As a result, it will be possible to produce a bonded body with a strong bonding interface. Furthermore, even if voids are formed in the bonding layer during sintering, it is thought that liquid compound (B) will flow into the defects such as voids, making it possible to obtain a bonding layer and bonded body with fewer defects.

[0036] The number of functional groups (b) in the compound (B) is preferably two or three.

[0037] The compound (B) may have a linear structure or a branched and / or cyclic structure, but preferably has a branched and / or cyclic structure, which is preferable in that the compound (B) has low crystallinity and is likely to become a liquid with good fluidity.

[0038] When the number of functional groups (b) in compound (B) is n, compound (B) preferably has an n-valent hydrocarbon group. In compound (B), the skeleton excluding functional groups (b) is more preferably composed only of n-valent hydrocarbon groups, in order to obtain a strong bonded body.

[0039] For the above reasons, it is preferable that compound (B) does not evaporate immediately when sintering begins, but it does not necessarily have to remain in the formed bonding layer when sintering is completed. When the carbon number of the n-valent hydrocarbon group is 30 to 60, the amount of compound (B) remaining in the bonding layer after sintering can be further reduced, making it easier to obtain a denser bonding layer, which is preferable. As a result, excellent initial bonding strength can be achieved, and further suppression of deterioration of bonding strength due to thermal cycling can be expected.

[0040] Specific examples of the compound (B) having a linear structure include eicosane diacid, heneicosane diacid, docosane diacid, tetracosane diacid, triacontanedioic acid, dotriacontanedioic acid, tetracontanedioic acid, pentacontanedioic acid, hexacontanedioic acid, and batyl alcohol, but are not limited to these.

[0041] Specific examples of the compound (B) having a branched and / or cyclic structure include, but are not limited to, dimer acid, trimer acid, tetramer acid, dimer diol, trimer triol, tetramer tetraol, dimer diamine, trimer triamine, tetramer tetramine, and phytantriol.

[0042] Among these specific examples, for the reasons described above, compound (B) is more preferably selected from dimer acid, trimer acid, dimer diol, trimer triol, dimer diamine, and trimer triamine, and even more preferably is a dimer acid or trimer acid.

[0043] Dimer acid, trimer acid, and tetramer acid can be produced by a polymerization reaction of unsaturated fatty acids. For example, they can be produced by the Diels-Alder reaction of oleic acid (18 carbon atoms) and linoleic acid (18 carbon atoms) or by a radical reaction. The dimer acid, trimer acid, and tetramer acid preferably have 36, 44, 54, and 72 carbon atoms, respectively. Furthermore, by appropriately changing the carbon number of the unsaturated fatty acid used as the raw material, it is possible to produce a compound (B) having a carbon number other than those mentioned above. In this specification, dimers, trimers, and tetramers of unsaturated fatty acids having 12 or more carbon atoms are referred to as dimer acid, trimer acid, and tetramer acid, respectively.

[0044] The dimer diol, trimer triol, and tetramer tetraol each have a structure in which the carboxy group of a dimer acid has been reduced to a hydroxyl group. The dimer diol, trimer triol, and tetramer tetraol each have a structure in which the carboxy group of a trimer acid has been reduced to a hydroxyl group. The dimer diol, trimer triol, and tetramer tetraol preferably have 36, 54, and 72 carbon atoms, respectively.

[0045] The dimer diamine, trimer triamine, and tetramer tetramine have a structure in which the carboxy group of a dimer acid has been functionally converted to an amino group. The dimer diamine, trimer triamine, and tetramer tetramine preferably have 36, 54, and 72 carbon atoms, respectively.

[0046] Compound (B) may be a mixture of compounds with different degrees of polymerization due to the manufacturing method, but it may be used as a mixture of different polymers, or a specific single compound may be used.

[0047] In the bonding paste of the present invention, the compound (B) is preferably contained in an amount of 0.1 to 3 parts by mass, more preferably 0.3 to 2.7 parts by mass, per 100 parts by mass of the metal particles (A). Within this range, a bonded body can be obtained that is particularly excellent in initial bonding strength and that is inhibited from decreasing in bonding strength due to thermal cycling.

[0048] <Dispersion medium (C)> The bonding paste of the present invention contains a dispersion medium (C) (excluding compound (B)) having a boiling point of 200°C or higher. It is important that the boiling point of the dispersion medium (C) is 200°C or higher, and it not only serves to disperse the metal particles (A) and compound (B) but also to impart fluidity to the coating film during the silver sintering process. When the paste contains a dispersion medium (C) having a boiling point of 200°C or higher, the dispersion medium in the coating film dries and decreases relatively slowly during the silver sintering process, allowing the coating film to be sintered while maintaining high fluidity. This improves adhesion to the bonded parts and enables the production of a stronger bonded body with fewer defects. The bonding paste of the present invention may contain a dispersion medium other than the dispersion medium (C) having a boiling point of 200°C or higher, provided that the effects of the present invention are not impaired. However, it is preferable that the proportion of the dispersion medium (C) having a boiling point of 200°C or higher be 70 mass% or higher. The number of carbon atoms in the dispersion medium (C) is preferably less than 20.

[0049] The boiling point of the dispersion medium (C) is preferably 240°C or higher, more preferably 250°C or higher. At 250°C or higher, the coating film can be sintered for a longer period of time while maintaining high fluidity. This is preferable because it forms a stronger bonded body with fewer defects and has excellent thermal cycling properties. In addition, the boiling point is preferably 350°C or lower in order to suppress residual dispersion medium. When the dispersion medium (C) having a temperature of 200°C or higher is a mixture, the boiling point of the dispersion medium (C) can be calculated from the boiling points of each component and their mass ratios.

[0050] Examples of the dispersion medium (C) include terpineol, dihydroterpineol, dihydroterpinyl acetate, Tersolve MTPH (manufactured by Nippon Terpene Co., Ltd.), Texanol (2,2,4-trimethylpentane-1,3-diol monoisobutyrate), isophorone, γ-butyl lactone, 1,3-butanediol, 1,4-butanediol, 2-ethyl-1,3 hexanediol, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, polyethylene glycol monobutyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, and hydrocarbon solvents having a boiling point of 200 ° C. or higher. These dispersion media (C) can be used alone or in combination.

[0051] Among these dispersion media (C), diol-based solvents such as 1,3-butanediol, 1,4-butanediol, and 2-ethyl-1,3-hexanediol; and glycol ether-based solvents such as diethylene glycol monohexyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, and polyethylene glycol monobutyl ether are preferably used. More preferably, glycol ethers having a boiling point of 250° C. or higher are used, such as diethylene glycol monohexyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, and polyethylene glycol monobutyl ether.

[0052] When sintering the joining paste, if the boiling point of the dispersion medium (C) is lower than the boiling point of the compound (B), the amount of the dispersion medium (C) can be reduced and the content of the metal particles (A) can be increased, which is preferable.

[0053] <Manufacturing of bonding paste> The bonding paste of the present invention, which uses a combination of metal particles (A) and compound (B), exhibits excellent fluidity even when the metal particles (A) are contained at a high concentration, i.e., when the content of dispersion medium (C) is low, and therefore has excellent printability on the bonded body, making it possible to obtain a stronger bonded body with fewer defects.

[0054] In the bonding paste, the mass ratio of the metal particles (A) to the sum of the masses of the metal particles (A), the compound (B), and the dispersion medium (C) is preferably 80% to 95% by mass, more preferably 85% to 94% by mass. Also, the mass ratio of the metal particles (A) to the mass of the bonding paste is preferably 80% to 95% by mass, more preferably 85% to 94% by mass. By including the metal particles (A) in the above range, it is possible to ensure good printability as a bonding paste, and also to suppress the residue of the dispersion medium (C) in the bonded body, thereby suppressing the generation of voids originating from the dispersion medium (C), and thereby to achieve good bonding strength.

[0055] The bonding paste of the present invention may contain additives, such as a sintering accelerator, a binder resin, or a resin-type dispersant.

[0056] Examples of an apparatus for preparing a bonding paste from the metal particles (A), the compound (B), and the dispersion medium (C) include a disper, a three-roll mill, a bead mill, an ultrasonic disperser, and a planetary stirrer.

[0057] <zygote> The bonding paste of the present invention can be used to bond a first part to be bonded and a second part to be bonded to obtain a bonded body.

[0058] The method for applying the bonding paste to the members to be bonded is not particularly limited as long as it can be applied uniformly to the members. Examples include various printing methods such as screen printing, flexographic printing, offset printing, gravure printing, metal mask printing, and gravure offset printing, and a discharge method using a dispenser. Since the bonding paste of the present invention has excellent fluidity even when it contains metal particles at a high concentration, it is particularly preferable to use it in combination with metal mask printing.

[0059] When placing the second part to be joined on the first part to be joined coated with the bonding paste of the present invention, the second part to be joined can be placed under pressure. The pressure is appropriately set depending on the viscosity of the bonding paste and the drying state of the paste, but is preferably 0.1 to 40 MPa, more preferably 0.3 to 30 MPa.

[0060] The sintering conditions for bonding a laminate in which a second bonded portion is placed on a first bonded portion may be varied as appropriate, but examples include conditions such as atmospheric pressure, a nitrogen atmosphere, a vacuum, or a reducing atmosphere at 200 to 350°C. Examples of sintering devices include hot air ovens, sintering furnaces, electric furnaces, infrared ovens, reflow ovens, microwave ovens, hot plates, and optical sintering devices. These devices may be used singly or in combination as appropriate. Pressure may also be applied during sintering. The pressure is set as appropriate depending on the viscosity of the bonding paste and the drying state of the paste, but is preferably 0.1 to 40 MPa, and more preferably 0.3 to 30 MPa.

[0061] Before the baking step, a preliminary drying step can be carried out as appropriate to remove organic components from the bonding coating film. For example, a pre-drying step can be carried out using a device similar to the baking device at a temperature in the range of 60 to 220°C.

[0062] A preferred method for joining two parts to be joined is to apply the joining paste of the present invention to a first part to be joined, place a second part to be joined on it, and then heat it up to about 300°C at a heating rate of about 2 to 10°C / min to sinter it. After the temperature rise is complete, it is preferable to maintain the temperature higher than the temperature at the end of the temperature rise for about 10 minutes to 2 hours.

[0063] The type of the part to be joined is not particularly limited, and examples thereof include metal materials, semiconductor materials, plastic materials, ceramic materials, etc. Also included are electronic elements.

[0064] Examples of metals include copper, gold, and aluminum. Examples of semiconductor materials include silicon, germanium, gallium arsenide, gallium phosphide, cadmium sulfide, silicon nitride, graphite, yttrium oxide, magnesium oxide, silicon carbide, and gallium nitride. Examples of the plastic material include polyimide, polyethylene, polypropylene, polyethylene terephthalate, polycarbonate, and polyethylene naphthalate. Examples of ceramic materials include glass and silicon.

[0065] Examples of electronic elements include semiconductor elements, LED elements, and power device elements.

[0066] The first and second joined parts may be made of different materials, not necessarily the same material. The surfaces of the joined parts may be subjected to a corona treatment, a plating treatment, or the like to increase the joining strength of the joined parts.

[0067] There is no limitation on the thickness of the bonding layer formed when bonding parts to be bonded with the bonding paste of the present invention, but it is preferably 3 μm to 500 μm, more preferably 10 μm to 200 μm, and even more preferably 20 μm to 100 μm. [Example]

[0068] The present invention will be described in detail below using examples and comparative examples, but the technical scope of the present invention is not limited thereto. In the examples, unless otherwise specified, "parts" and "%" represent "parts by mass" and "% by mass", respectively, and numerical values ​​in tables represent "parts" unless otherwise specified.

[0069] <Production of Metal Particles (A)> (Production example 1) Metal particles A1 Under a nitrogen atmosphere, 200 parts of toluene and 22.3 parts of silver hexanoate were mixed with stirring at 25°C to obtain a 0.5M solution, followed by the addition of 1.6 parts of diethylaminoethanol as a dispersant and 0.28 parts of oleic acid. Subsequently, 73.1 parts of a 20% aqueous solution of succinic acid dihydrazide (SUDH) as a reducing agent were added dropwise, causing the solution color to change from pale yellow to dark brown. To further promote the reaction, the temperature was raised to 40°C. After allowing to stand and separating, the aqueous phase was removed to remove excess reducing agent and impurities. The toluene layer was then repeatedly washed and separated with distilled water, followed by the addition of toluene, centrifugation, and removal of the supernatant. This process was repeated twice. The precipitate was dried to obtain metal particles A1, in which silver particles were coated with hexanoic acid and oleic acid. The particle size of metal particles A1 was determined using the method described below, and the d50 was found to be 210 nm.

[0070] (Production example 2) Metal particles A2 Metal particles A2 were obtained in the same manner as in Production Example 1, except that the amount of diethylaminoethanol was 2.4 parts and the amount of oleic acid was 0.42 parts. The d50 was 120 nm. (Production example 3) Metal particles A3 Metal particles A3 were obtained in the same manner as in Production Example 1, except that the amount of diethylaminoethanol was 2.0 parts and the amount of oleic acid was 0.34 parts. The d50 was 155 nm. (Production example 4) Metal particles A4 Metal particles A4 were obtained in the same manner as in Production Example 1, except that the amount of diethylaminoethanol was 1.8 parts and the amount of oleic acid was 0.31 parts. The d50 was 185 nm. (Production example 5) Metal particles A5 Metal particles A5 were obtained in the same manner as in Production Example 1, except that the amount of diethylaminoethanol was 1.2 parts and the amount of oleic acid was 0.18 parts. The d50 was 290 nm. (Production example 6) Metal particles A6 Metal particles A6 were obtained in the same manner as in Production Example 1, except that the amount of diethylaminoethanol was 1.0 part and the amount of oleic acid was 0.14 part. The d50 was 390 nm.

[0071] (Production example 7) Metal particles A7 Metal particles A7 were obtained in the same manner as in Production Example 1, except that the amount of diethylaminoethanol was 1.4 parts and the amount of oleic acid was 0.09 parts. The d50 was 600 nm. (Production example 8) Metal particles A8 Metal particles A8 were obtained in the same manner as in Production Example 1, except that the amount of diethylaminoethanol was 0.6 parts and the amount of oleic acid was 0.070 parts. The d50 was 1100 nm. (Production example 9) Metal particles A9 Metal particles A9 were obtained in the same manner as in Production Example 1, except that the amount of diethylaminoethanol was 2.3 parts and the amount of oleic acid was 2.8 parts. The d50 was 20 nm. (Production example 10) Metal particles A10 Metal particles A10 were obtained in the same manner as in Production Example 1, except that the amount of diethylaminoethanol was 2.1 parts and the amount of oleic acid was 0.71 parts. The d50 was 85 nm.

[0072] [Particle size measurement] Isopropyl alcohol was added to each metal particle (A) and dispersed using an ultrasonic disperser to obtain a 0.5% by mass dispersion. The particle size of the metal particles (A) in the dispersion was measured using a Nanotrac UPA-EX150 (manufactured by Nikkiso Co., Ltd.) to determine the average particle size (d50). Of the metal particles produced by the above method, metal particles A1 to A6 correspond to metal particles (A), and metal particles A7 to A10 correspond to metal particles that are not metal particles (A).

[0073] <Production of Compound (B)> (Production Example 11) Trimertriol (Compound B5) Trimer triol was synthesized as follows, with reference to the method described in JP-A-10-67835. Under a nitrogen atmosphere, 1000 g of an unsaturated fatty acid ester mixture containing 75% methyl oleate, 15% methyl linoleate, and 9% methyl stearate was reacted with 70 g of activated clay in an autoclave at 230°C for 5 hours. The catalyst was filtered off from the reaction solution, and the mixture was distilled under reduced pressure to obtain 115 g of trimer acid trimethyl ester. In a flask equipped with a dropping funnel, a condenser, a thermometer and a stirrer, 6.4 g of lithium aluminum hydride and 240 ml of diethyl ether were carefully mixed under a nitrogen atmosphere to prepare a dispersion of lithium aluminum hydride. Under a nitrogen atmosphere, a solution prepared by diluting 50 g of trimer acid trimethyl ester with 70 ml of diethyl ether was added dropwise to the above dispersion over 120 minutes while stirring. The temperature was maintained below approximately 30°C. After the addition, the mixture was stirred for approximately 40 minutes. Then, 13 g of ion-exchanged water was carefully added dropwise while cooling to inactivate the excess reducing agent. The reaction mixture was carefully transferred to a flask containing 70 g of ice water, and 50 g of 10% aqueous sulfuric acid solution was added. After allowing to stand for a while, an appropriate amount of diethyl ether was added to the flask to extract the product. The ether layer was repeatedly washed with water until neutral, and the diethyl ether was distilled off to obtain 31 g of a 54-carbon trimer triol consisting of three hydroxyl groups and a trivalent hydrocarbon group with branched and cyclic structures. The resulting trimer triol was a viscous liquid at 25°C.

[0074] [Compound (B)] The following materials were used as compounds (B) other than the above compound B5. However, compounds B9 and B10 are not compounds (B) of the present application. The carbon number, material name, and properties at 25°C are written in parentheses.

[0075] Compound B1: Pripol 1009 (manufactured by Croda Japan Co., Ltd.; hydrogenated dimer acid having 36 carbon atoms. Consists of two carboxyl groups and a divalent hydrocarbon group having a branched and cyclic structure. Liquid) Compound B2: Pripol 1004 (manufactured by Croda Japan Co., Ltd.; hydrogenated dimer acid having 44 carbon atoms. Consists of two carboxyl groups and a divalent hydrocarbon group having a branched and cyclic structure. Liquid) Compound B3: Pripol 1040 (manufactured by Croda Japan Co., Ltd.; a trimer acid having 54 carbon atoms, consisting of three carboxyl groups and a trivalent hydrocarbon group having a branched and cyclic structure; liquid) Compound B4: Pripol 2033 (manufactured by Croda Japan Co., Ltd., a dimer diol having 36 carbon atoms. It consists of two hydroxyl groups and a divalent hydrocarbon group having a branched and cyclic structure. Liquid) Compound B5: trimer triol (carbon number: 54, liquid) obtained in Production Example 11 Compound B6: Priamine 1071 [manufactured by Croda Japan Co., Ltd., a mixture of a C36 dimer diamine (composed of two amino groups and a divalent hydrocarbon group having a branched and cyclic structure, liquid) and a C54 trimer triamine (composed of three amino groups and a trivalent hydrocarbon group having a branched and cyclic structure, liquid)] Compound B7: Priamine 1075 (manufactured by Croda Japan Co., Ltd., a dimer diamine having 36 carbon atoms, consisting of two amino groups and a divalent hydrocarbon group having a branched and cyclic structure, liquid) Compound B8: Docosanedioic acid (a straight-chain dibasic acid with 22 carbon atoms, solid) Compound B9: Oleic acid (a monovalent straight-chain fatty acid with 18 carbon atoms, liquid) Compound B10: Malonic acid (a divalent straight-chain fatty acid with three carbon atoms. Solid)

[0076] <Dispersion medium (C)> The following materials were used as dispersion media (C). Supplementary information and boiling points are given in parentheses. However, dispersion media C5 and C6 do not fall under the category of dispersion media (C) of the present application. Dispersion medium C1: Triethylene glycol monobutyl ether (glycol ether type, boiling point 278°C) Dispersion medium C2: Triethylene glycol monomethyl ether (glycol ether type, boiling point 248°C) Dispersion medium C3: 2-ethyl-1,3-hexanediol (diol, boiling point 244°C) Dispersion medium C4: 1-decanol (boiling point 233°C) Dispersion medium C5: Diethylene glycol monomethyl ether (glycol ether type, boiling point 193°C) Dispersion medium C6: 1-octanol (boiling point 194°C)

[0077] <Manufacturing of bonding paste> [Example 1] Metal particles A1 (90 parts), triethylene glycol monobutyl ether (10 parts), and compound B1 (1 part) were mixed using a planetary stirrer to prepare a bonding paste.

[0078] [Examples 2 to 37], [Comparative Examples 1 to 9] Bonding pastes were obtained in the same manner as in Example 1, except that the types and amounts of materials were changed according to the compositions shown in Tables 1 to 3.

[0079] <Evaluation of bonding paste> Bonded body 1 was produced by the method described below using the bonding pastes obtained in Examples 1 to 36 and Comparative Examples 1 to 9. Bonded body 2 was produced by the method described below using the bonding paste obtained in Example 37 (equivalent to Example 20). The resulting bonded bodies 1 and 2 (hereinafter simply referred to as bonded bodies) were evaluated as follows. The results are shown in Tables 1 to 3. In the tables, unless otherwise specified, the numerical values ​​represent parts, and blank spaces indicate that no compound was added.

[0080] [Preparation of zygote 1] The joining paste obtained in Examples 1 to 36 and Comparative Examples 1 to 9 was printed once on one side of the joining part 1 described below under the printing conditions described below, and then the plated surface of the joining part 2 (chip) described below was placed facing the joining paste surface and heated under the sintering conditions described below to obtain each joined body. [Joined part 1] Copper substrate (oxygen-free copper (C1020)): 20mm x 20mm x 1mm [Joined part 2] Gold-plated SiC chip: 5mm x 5mm x 0.3mm [Printing conditions (metal mask printing)] Metal mask: 4mm square opening, 50μm thick (manufactured by Seria Corporation) Metal squeegee: 40mm x 250mm, thickness 1mm (manufactured by Seria Corporation) [Sintering conditions] The unsintered bonded body was placed in a firing furnace, and the temperature was raised from 25°C to 300°C at a rate of 2°C / min in a nitrogen atmosphere. After reaching 300°C, the temperature was maintained at 300°C for 2 hours.

[0081] [Preparation of junction 2] In the same manner as in the bonded body 1, the bonding paste obtained in Example 37 was printed once on one surface of the bonded part 1, and then the bonded part was placed in a hot air oven and dried for 10 minutes at 170°C. Next, the plated surface of the bonded part 2 (chip) was placed facing the dried bonding paste surface, and while applying a pressure of 20 MPa from above the bonded part 2, the temperature was raised from room temperature to 300°C at a rate of 20°C / min. After reaching 300°C, the temperature was maintained for 10 minutes to obtain a bonded body.

[0082] [Evaluation criteria (printability)] ○: Printing was possible on the bonded part 1. ×: Printing on the part to be joined 1 was not possible.

[0083] <Bonding strength (initial, after thermal cycle test)> The bond strength (die shear strength) of the resulting bonded bodies was measured using the following measuring device and test conditions. Note that an asterisk (*) in Table 3 indicates that this evaluation was not performed because printing was not possible.

[0084] Measurement equipment: Universal bond tester (Daisi Japan Co., Ltd., 4000 series) [Test conditions] Measurement height: 100μm Measurement speed: 500μm / s Specifically, the bonded body was fixed at the location of the bonded part 1, and the bond was pushed from the interface between the bonded part 1 and the bonding layer toward the bonded part 2 at a height of 100 μm at a speed of 500 μm / s, and the bond strength at which the bond was broken was determined. The bond strength immediately after the bonded body was produced (initial bond strength) and after the cycle test described below (bond strength after 500 cycles) were measured and evaluated based on the following evaluation criteria. The higher the adhesive strength value, the better, and a value of 15 MPa or more is within the practical range. The higher the evaluation criterion value, the better, and an evaluation criterion value of 2 or less indicates poor performance.

[0085] [Evaluation criteria] 5:30MPa or more 4: 20MPa or more and less than 30MPa 3: 15 MPa or more and less than 20 MPa 2: 5 MPa or more but less than 15 MPa 1: Less than 5 MPa

[0086] <Cold-heat cycle test> The bonded body was stored for 500 cycles, with one cycle consisting of holding it at -40°C for 30 minutes, then at 25°C for 15 minutes, and then at 150°C for 30 minutes.The bonded body was then evaluated using the same procedures and criteria as the above-mentioned bond strength evaluation method.

[0087] When the bonding paste of the comparative example was used, the bonding strength was significantly low, and when the broken sample after the die shear test was observed, the breakage was at the interface between the copper substrate and the bonding layer. On the other hand, when the bonding paste of the example was used, the bonding strength was very high. When the bonding paste of the example was used, the printing suitability was excellent, and further, even when a copper substrate that had not been plated and is prone to deterioration due to thermal cycling was used as the bonding part, the bonding strength was very high, and it was confirmed that the decrease in bonding strength was suppressed even after the thermal cycling test.

[0088] [Table 1]

[0089] Table 2

[0090] Table 3

Claims

1. A bonding paste comprising: metal particles (A) having an average particle size of 100 nm to 500 nm; a compound (B) having 20 to 80 carbon atoms and having two or more functional groups (b) that are any one type selected from a hydroxyl group, a carboxyl group, and an amino group; and a dispersion medium (C) having a boiling point of 200°C or higher, the metal particles (A) contain silver, A joining paste characterized in that the compound (B) contains one or more selected from the group consisting of dimer acid, trimer acid, dimer diol, trimer triol, dimer diamine, trimer triamine, and docosanedioic acid.

2. 2. The bonding paste according to claim 1, wherein the number of functional groups is two or three.

3. 2. The joining paste according to claim 1, wherein the compound (B) has a branched and / or cyclic structure.

4. 2. The bonding paste according to claim 1, wherein the compound (B) has an n-valent hydrocarbon group, where n is the number of the functional groups.

5. 5. The bonding paste according to claim 4, wherein the n-valent hydrocarbon group has 30 to 60 carbon atoms.

6. 2. The joining paste according to claim 1, wherein the compound (B) comprises at least one selected from the group consisting of dimer acid, trimer acid, dimer diol, trimer triol, dimer diamine, and trimer triamine.

7. 2. The bonding paste according to claim 1, wherein the compound (B) is contained in an amount of 0.3 to 2.7 parts by mass per 100 parts by mass of the metal particles (A).

8. The bonding paste according to claim 1, wherein the metal particles (A) have an average particle size of 150 nm to 500 nm.

9. 2. The joining paste according to claim 1, wherein the dispersion medium (C) contains at least one selected from the group consisting of glycol ethers and diols.

10. The bonding paste according to claim 1, wherein the dispersion medium (C) has a boiling point of 250°C or higher.

11. The bonding paste according to claim 1, wherein the mass ratio of the metal particles (A) to the mass of the bonding paste is 80 mass% to 95 mass%.

12. A method for manufacturing a joined body, comprising the steps of applying the joining paste according to any one of claims 1 to 11 to a first joined part, placing a second joined part thereon, and joining the first joined part and the second joined part by sintering.

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