Bonding material composition, method for manufacturing a bonding material composition, bonding film, method for manufacturing a bonded body, and bonded body

Abstract

To provide a joining material composition which can improve shear strength, heat resistance, conductivity and heat dissipation property of a joining layer, a method for producing a joining material composition, a joining film, a method for manufacturing a joined body, and a joined body.SOLUTION: A joining material composition contains metal particles (P) containing first metal particles (P1) and second metal particles (P2), and a flux, where the first metal particles (P1) are composed of a core (C1) composed of Cu, and a Cu2O layer coating the core (C1), and the second metal particles (P2) is composed of a core (C2) composed of Cu, and Sn coating the core (C2) or a solder containing Sn.SELECTED DRAWING: None

Description

[[Technical Field]]

[0001] The present invention relates to a bonding material composition, a method for producing a bonding material composition, a bonding film, a method for producing a bonded body, and a bonded body, and particularly relates to a bonding material composition and a bonding film for connecting a semiconductor element to a substrate such as a circuit board or a ceramic substrate, as well as a method for producing a bonded body using the bonding material composition and the bonding film, and a bonded body. [[Background Art]]

[0002] A semiconductor device is generally manufactured through the steps of: forming a die attach material for bonding a semiconductor element on an element carrying portion of a lead frame or a circuit electrode portion of an insulating substrate; mounting the semiconductor element on the surface of the die attach material on the lead frame or the circuit electrode, and bonding the element carrying portion of the lead frame or the circuit electrode portion of the insulating substrate to the semiconductor element; performing a wire bonding step of electrically bonding the electrode portion of the semiconductor element to the terminal portion of the lead frame or the terminal portion of the insulating substrate; and performing a molding step of coating the thus-assembled semiconductor device with resin.

[0003] Here, a bonding material is used when bonding the element carrying portion of the lead frame or the circuit electrode portion of the insulating substrate to the semiconductor element. For example, as a bonding material for power semiconductors such as IGBTs and MOS-FETs, lead solder containing 85 mass% or more of lead having a high melting point and heat resistance has been widely used. However, in recent years, the harmfulness of lead has been regarded as a problem, and demands for lead-free bonding materials have been increasing.

[0004] Furthermore, compared with Si power semiconductors, SiC power semiconductors are characterized by low loss and enabling operation at high speed and high temperature, and are expected as next-generation power semiconductors. Such SiC power semiconductors can theoretically operate at 200°C or higher, but for the practical application of high-output and high-density systems such as inverters, improvement in heat resistance is also desired for peripheral materials including bonding materials.

[0005] Against this backdrop, various lead-free, high-melting-point bonding materials have been gaining attention in recent years. Such high-melting-point, lead-free bonding materials include Au-based alloys such as Au-Sn alloys and Au-Ge alloys (for example, Patent Document 1), which have attracted attention for their good electrical and thermal conductivity and chemical stability. However, because such Au-based alloy materials contain precious metals, their material costs are high, and expensive high-temperature vacuum reflow equipment is required to achieve better mounting reliability, so they have not yet been put into practical use.

[0006] Therefore, as a bonding method for semiconductor devices that operate at high temperatures, a bonding method called Transient Liquid Phase Sintering (TLP) has attracted attention, in which a bonding material containing Cu and Sn is interposed between the semiconductor device and the substrate, and heated at a temperature higher than the melting point of Sn, thereby forming an intermetallic compound (IMC) with a composition of Cu6Sn5 or Cu3Sn. Bonding methods and bonding films using this method have been disclosed (see, for example, Patent Documents 2 and 3).

[0007] Patent Document 2 discloses a bonding method in which a paste-like bonding agent containing Cu particles and Sn particles is interposed between the bonding surface of a semiconductor chip and the bonding surface of a substrate, heated at a temperature higher than the melting point of Sn to cause transition-phase sintering of Cu and Sn, the bonding agent to have a composition containing Cu6Sn5 and Cu3Sn, and further heated in a temperature range of 232°C to 415°C to change the Cu6Sn5 in the bonding agent to Cu3Sn, thereby increasing the ratio of Cu3Sn in the bonding agent and resulting in a single phase of Cu3Sn or an equilibrium structure of Cu3Sn phase and Cu particles.

[0008] Patent Document 3 discloses a bonded film comprising first metal particles and second metal particles capable of forming intermetallic compounds such as Cu-Sn, a resin, and at least one of phosphines and sulfides.

[0009] Furthermore, a bonding paste that does not utilize the transitional liquid-phase sintering method has been disclosed, which is a mixture of fine powder with an average particle size of 0.05 to 1 μm, composed of a core made of Cu and a coating layer made of Cu6Sn5 covering the core, and an organic solvent (see, for example, Patent Document 4). After interposing this bonding paste between the first and second members to be joined, the first and second members to be joined are heated at a temperature of 250 to 400°C for 5 to 120 minutes under a nitrogen gas atmosphere or a formic acid gas atmosphere with a pressure of at least 0.1 MPa so that they are in close contact with each other. This causes Cu particles to diffuse almost uniformly into the intermetallic compound of Cu6Sn5, resulting in a Cu3Sn structure with a solidification start temperature of 676°C, and enabling a bond with high initial bonding strength and bonding strength during the cold-heat cycle. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2006-032888 [Patent Document 2] Patent No. 6061248 [Patent Document 3] International Publication No. 2017 / 138255 [Patent Document 4] Patent No. 6753349 [Overview of the initiative] [Problems that the invention aims to solve]

[0011] However, the bonding method described in Patent Document 2 above has problems with low shear strength and heat dissipation because it is difficult to remove the oxides formed on the surface of the Cu particles, so when the bonding agent is heated, the molten liquid phase Sn does not easily wet the surface of the Cu particles, and unreacted Cu particles remain in the bonding layer. Furthermore, when the molten Sn solidifies, it becomes bulk, so the elongation of the bonding layer is small, which leads to a decrease in shear strength and low heat resistance at the high operating temperature of power semiconductors. In addition, heating must be done in two stages to change Cu6Sn5 to Cu3Sn and increase the ratio of Cu3Sn, which is time-consuming.

[0012] In the bonding method described in Patent Document 3 above, although oxides formed on the surface of Cu particles are removed because at least one of phosphines and sulfides is included, the liquid Sn phase is fluid and therefore localized, resulting in unreacted Cu particles remaining in the bonding layer, and thus insufficient shear strength and heat dissipation.

[0013] In the bonding film described in Patent Document 4 above, since the melting point of Cu6Sn5 coating the Cu core is high, the bonding layer is formed by sintering finely milled particles using the milling effect and pressure. Because the bonding layer is a sintered body, there are many voids. Therefore, there were problems such as low conductivity and heat dissipation, as well as low elongation and low heat resistance. In addition, because finely milled particles are used, it is possible to apply this to thin films, but it is expected that it will be difficult to form thick films.

[0014] Therefore, the present invention aims to provide a bonding material composition, a method for manufacturing the bonding material composition, a bonding film, a method for manufacturing a bonded body, and a bonded body that can improve the shear strength, heat resistance, conductivity, and heat dissipation of the bonding layer. [Means for solving the problem]

[0015] To solve the above problem, the bonding material composition according to the present invention comprises: metal particles (P) including first metal particles (P1) and second metal particles (P2); and a flux, wherein the first metal particles (P1) are composed of a core (C1) made of Cu and a Cu₂O layer coating the core (C1), and the second metal particles (P2) are composed of a core (C2) made of Cu and Sn or Sn-containing solder coating the core (C2).

[0016] In the bonding material composition, it is preferable that the first metal particles (P1) have an average particle diameter of 1 to 20 µm, and the second metal particles (P2) have an average particle diameter of 1 to 10 µm.

[0017] In the bonding material composition, it is preferable that a proportion of Sn in the Sn or the Sn-containing solder coating the core (C2) is 55 to 65% by mass relative to 100% by mass of the total amount of Cu of the core (C1) and Cu of the core (C2).

[0018] In the bonding material composition, when the diffraction intensity of the Cu (111) plane of the first metal particles (P1) measured by X-ray diffraction is defined as H1, and the diffraction intensity of the Cu₂O (111) plane is defined as H2, it is preferable that an oxidation degree H of the first metal particles (P1) represented by the following formula 1 is 0.05 to 0.3. H=H2 / (H1+H2) [Formula 1]

[0019] In the bonding material composition, it is preferable that the metal particles (P) further include third metal particles (P3), and the third metal particles (P3) are Sn particles or Sn-containing solder particles.

[0020] In the bonding material composition, it is preferable that a total proportion of Sn in the Sn or the Sn-containing solder coating the core (C2) and Sn in the Sn particles or the Sn-containing solder particles is 55 to 65% by mass relative to 100% by mass of the total amount of Cu of the core (C1) and Cu of the core (C2).

[0021] Further, in the bonding material composition, it is preferable that the flux has reducing properties, and the reaction product does not contain water.

[0022] Further, in the bonding material composition, it is preferable that the flux contains at least one of phosphines represented by the following general formula (1) and sulfides represented by the following general formula (2). Provided that in the following general formulas (1) and (2), each R independently represents an organic group, and R may be the same as or different from each other.

[0023]

Chemical Formula

[0024] Further, in the bonding material composition, it is preferable that the content ratio of the flux relative to the metal particles (P) is 0.05 to 0.5% by mass.

[0025] Further, in the bonding material composition, it is preferable that the content ratio of the metal particles (P) is 80 to 95% by mass relative to the total amount of the bonding material composition.

[0026] Further, when heated at 240° C. or higher, the bonding material composition forms a bonding layer that bonds a first member and a second member, and it is preferable that the bonding layer has a network structure in which Cu particles are bonded by a compound of Cu and Sn.

[0027] Further, it is preferable that the bonding material composition contains a thermosetting resin.

[0028] Further, in order to solve the above problems, a method for producing a bonding material composition according to the present invention is characterized by comprising a step of mixing and stirring the first metal particles (P1) and the second metal particles (P2).

[0029] Furthermore, in order to solve the above problems, the bonding film according to the present invention is a bonding film having a bonding material layer, wherein the bonding material layer is formed using any of the bonding material compositions described above.

[0030] Furthermore, the bonding film preferably has a bonding material layer thickness of 10 to 100 μm.

[0031] Furthermore, in order to solve the above problems, the present invention provides a method for manufacturing a bonded body, comprising joining a first member and a second member with a bonding layer using any of the bonding material compositions described above, wherein the bonding material composition is interposed between the first member and the second member and heated at 240°C or higher, thereby the flux removes the Cu2O layer of the first metal particles (P1), the Sn or solder containing Sn of the second metal particles (P2) melts and reacts with the Cu of the core (C1) and the Cu of the core (C2), forming a bonding layer having a network structure in which Cu particles are joined by a compound of Cu and Sn.

[0032] Furthermore, in order to solve the above problems, the present invention provides a method for manufacturing a bonded body in which a first member and a second member are joined by a bonding layer using any of the bonding films described above, wherein the bonding material layer is interposed between the first member and the second member and heated at 240°C or higher, the flux removes the Cu2O layer of the first metal particles (P1), the Sn or solder containing Sn of the second metal particles (P2) melts and reacts with the Cu of the core (C1) and the Cu of the core (C2), forming a bonding layer having a network structure in which Cu particles are joined by a compound of Cu and Sn.

[0033] Furthermore, in order to solve the above problems, the joint according to the present invention is a joint in which a first member and a second member are joined by a joining layer using any of the above-mentioned joining material compositions, wherein the joining layer is formed by heating the joining material composition at 240°C or higher.

[0034] Furthermore, in order to solve the above problems, the joint according to the present invention is a joint in which a first member and a second member are joined by a bonding layer using any of the bonding films described above, wherein the bonding layer is formed by heating the bonding material layer at 240°C or higher.

[0035] In the above-described bonded body, it is preferable that the bonding layer has a network structure in which Cu particles are bonded together by a compound of Cu and Sn.

[0036] The above-mentioned bonded body preferably has a bonding layer thickness of 10 to 300 μm. [Effects of the Invention]

[0037] According to the present invention, it is possible to provide a bonding material composition that can improve the shear strength, heat resistance, conductivity, and heat dissipation of the bonding layer, a method for manufacturing the bonding material composition, a bonding film, a method for manufacturing a bonded body, and a bonded body. [Modes for carrying out the invention]

[0038] The following describes the bonding material compositions according to embodiments of the present invention.

[0039] A bonding material composition according to one embodiment of the present invention comprises metal particles (P) including first metal particles (P1) and second metal particles (P2), and flux, wherein the first metal particles (P1) are composed of a core (C1) made of Cu and a Cu2O layer covering the core (C1), and the second metal particles (P2) are composed of a core (C2) made of Cu and Sn or solder containing Sn covering the core (C2).

[0040] The bonding material composition of the present invention can be used as a bonding paste for bonding semiconductor elements and substrates, etc. Furthermore, the bonding material composition of the present invention can be formed into a film to form the bonding material layer of a bonding film having a bonding material layer.

[0041] The following describes in detail each component of the bonding material composition of this embodiment.

[0042] (First metal particle (P1)) The first metal particle (P1) is composed of a core (C1) made of Cu and a Cu2O layer covering the core (C1). The Cu2O layer can be formed by heating the Cu particles in an oven or the like at 170 to 300°C for 30 minutes to 50 hours. The heating temperature and heating time can be adjusted as appropriate, as long as the Cu2O layer is formed within that range.

[0043] The degree of oxidation H of the first metal particle (P1) is preferably 0.05 to 0.3, and more preferably 0.05 to 0.2. The degree of oxidation H can be determined by the following formula 1, where H1 is the diffraction intensity of the Cu(111) plane and H2 is the diffraction intensity of the Cu2O(111) plane of the first metal particle (P1) as measured by X-ray diffraction. H=H2 / (H1+H2) [Formula 1]

[0044] X-ray diffraction using CuKα as the X-ray source shows that the (111) plane of copper(I) oxide (Cu2O) has a peak around 2θ=36°, while the (111) plane of copper(Cu) has a peak around 2θ=43°. Note that only copper(I) oxide (Cu2O) exists as copper oxide; copper(II) oxide (CuO) does not exist under these conditions. Thus, when the peak height of the Cu(111) plane located around 2θ=43° is denoted as H1 and the peak height of the Cu2O(111) plane located around 2θ=36° is denoted as H2, the degree of oxidation H can be determined from the X-ray diffraction peak intensity ratio (H2 / [H1+H2]).

[0045] If the degree of oxidation (H) is less than 0.05, the reaction between the Cu of the core (C1) of the first metal particle (P1) and the Sn or Sn-containing solder of the second metal particle (P2) will occur only partially, making it difficult to obtain a uniform structure throughout the entire bond layer. If the degree of oxidation (H) exceeds 0.3, the oxide film is too thick, and the removal of the oxide film by flux may not be sufficient. This may result in an insufficient reaction between the Cu of the core (C1) of the first metal particle (P1) and the Sn or Sn-containing solder of the second metal particle (P2), potentially leading to a decrease in the shear strength, heat resistance, and heat dissipation of the bond layer. Furthermore, if the degree of oxidation (H) exceeds 0.5, the removal of the oxide film by flux may not be sufficient, potentially leading to a decrease in the conductivity of the bond layer.

[0046] The degree of oxidation H can be adjusted by adjusting the heating temperature and heating time of the core (C1).

[0047] The average particle size of the first metal particles (P1) is preferably 1 to 20 μm, and more preferably 5 to 8 μm. If the average particle size of the first metal particles (P1) is less than 1 μm, aggregation is likely to occur, the catalytic effect may become too strong, and the dispersibility with the thermosetting resin may decrease. As a result, the shear strength, heat resistance, conductivity, and heat dissipation of the bonded layer may decrease. If the average particle size of the first metal particles (P1) is greater than 20 μm, when the bonding material composition is heated to 240°C or higher, it may become difficult to react uniformly with the Sn of the second metal particles (P2), resulting in a bonded layer with an ununiform structure and potentially low shear strength and heat dissipation of the bonded layer. Furthermore, the bonded layer may become too thick, potentially reducing reliability. In addition, if the average particle size of the first metal particles (P1) exceeds 25 μm, the wettability of the solder may worsen, potentially reducing conductivity.

[0048] Furthermore, when the bonding material composition is formed into a film to form the bonding material layer of a bonding film, the average particle size of the first metal particles (P1) is preferably 1 to 10 μm. If the average particle size of the first metal particles (P1) exceeds 10 μm, the thickness of the bonding material layer becomes too large, making it difficult to handle as a film and resulting in poor mass production.

[0049] In this invention, the average particle size of each particle is determined by the median diameter (the particle size at which the cumulative frequency reaches 50%: D50). Specifically, it is determined by measuring a group of particles extracted and separated from the raw material powder or paste using a laser diffraction scattering particle size distribution analyzer.

[0050] (Second metal particle (P2)) The second metal particle (P2) consists of a core (C2) made of Cu and a coating of Sn or Sn-containing solder covering the core (C2). Here, "coating" means covering more than half of the surface area of ​​the core (C2). The second metal particle (P2) can be obtained by coating the core (C2) with Sn or Sn-containing solder using an electroless plating method. The Sn-containing solder is lead-free solder, and can be of the following types: tin (Sn)-nickel (Ni)-copper (Cu) system, tin (Sn)-silver (Ag)-copper (Cu) system, tin (Sn)-zinc (Zn)-bismuth (Bi) system, tin (Sn)-copper (Cu) system, tin (Sn)-silver (Ag)-indium (In)-bismuth (Bi) system, tin (Sn)-zinc (Zn)-aluminum (Al) system, etc.

[0051] The average particle size of the second metal particles (P2) is preferably 1 to 10 μm, more preferably 1 to 5 μm, and even more preferably 1.5 to 3 μm. Furthermore, in order to avoid the residue of Sn, which has low heat resistance, and to densely fill with the second metal particles (P2), it is also preferable that the average particle size of the second metal particles (P2) is smaller than the average particle size of the first metal particles (P1).

[0052] By setting the average particle size of the second metal particle (P2) to 1 μm or more, voids are more easily formed between the Cu3Sn formed by the wetting and spreading reaction of Sn on the surface of the Cu particles of the first metal particle (P1) and the Cu3Sn particles formed by the reaction of Sn with the Cu particles of the core (C2) of the second metal particle (P2) within the bonded layer formed by heating the bonding material composition to 240°C or higher. As a result, the elongation of the bonded layer increases, and the shear strength does not decrease even under the high operating temperature of the power semiconductor, improving heat resistance.

[0053] By setting the average particle size of the second metal particles (P2) to 10 μm or less, when the bonding material composition is heated to 240°C or higher, the second metal particles (P2) fill the spaces between the first metal particles (P1), allowing the reaction to proceed uniformly and resulting in a bonding layer with a uniform structure. This improves the shear strength and heat dissipation of the bonding layer.

[0054] If the average particle size of the second metal particles (P2) is less than 1 μm, the melting rate of the Sn or Sn-containing solder coating the core (C2) will be faster than the reduction rate of the Cu2O in the first metal particles (P1). Furthermore, the surface of the Sn or Sn-containing solder coating the core (C2) will be more prone to oxidation, potentially resulting in poor solder wettability. As a result, the shear strength, heat resistance, conductivity, and heat dissipation of the bonded layer may all decrease. If the average particle size of the second metal particles (P2) is greater than 10 μm, when the bonding material composition is heated to 240°C or higher, it will be difficult for it to react uniformly with the Cu in the first metal particles (P1), resulting in a bonded layer with an uneven structure and potentially low shear strength and heat dissipation of the bonded layer. Moreover, if the average particle size of the second metal particles (P2) exceeds 12 μm, the solder wettability may worsen, potentially leading to decreased conductivity.

[0055] The bonding material composition preferably contains 55 to 65% by mass of Sn or Sn-containing solder coating the core (C2) relative to 100% by mass of the total amount of Cu in the core (C1) and Cu in the core (C2). If the proportion of Sn is less than 55% by mass, when the bonding material composition is heated to 240°C or higher, the Sn will be used in the reaction with the Cu in the core (C2), making it difficult for the first metal particles (P1) to react with the Cu in the core (C1). As a result, a bonding layer with a uniform structure cannot be obtained, and the shear strength and heat dissipation of the bonding layer may be reduced. In addition, a sufficient compound of Cu and Sn may not be formed, which may reduce the heat resistance and conductivity of the bonding layer. If the proportion of Sn exceeds 65% by mass, much of the Cu in the core (C1) of the first metal particles (P1) becomes Cu3Sn, and the amount of Cu decreases, resulting in reduced heat dissipation. Furthermore, if the proportion of Sn exceeds 65% by mass, the molten Sn will solidify without reacting with Cu and become bulk, filling the gaps between the first metal particles (P1) and the second metal particles (P2). This can reduce the elongation of the bonding layer and potentially lower its heat resistance.

[0056] (Third metal particle (P3)) In a bonding material composition, if the proportion of Sn in the Sn or Sn-containing solder coating the core (C2) is less than 55% by mass relative to the total amount of Cu in core (C1) and Cu in core (C2) (100% by mass), the metal particles (P) may contain Sn particles or Sn-containing solder particles as third metal particles (P3), provided that the total proportion of Sn does not exceed 65% by mass. In other words, it is preferable that the bonding material composition has a proportion of 55 to 65% by mass of Sn in the Sn or Sn-containing solder coating the core (C2) and Sn particles or Sn-containing solder particles relative to the total amount of Cu in core (C1) and Cu in core (C2) (100% by mass). Solder particles containing tin are lead-free solders, and can be of the following types: tin (Sn)-nickel (Ni)-copper (Cu) system, tin (Sn)-silver (Ag)-copper (Cu) system, tin (Sn)-zinc (Zn)-bismuth (Bi) system, tin (Sn)-copper (Cu) system, tin (Sn)-silver (Ag)-indium (In)-bismuth (Bi) system, tin (Sn)-zinc (Zn)-aluminum (Al) system, etc.

[0057] (Flux) The bonding material composition contains flux. The flux is not particularly limited, and flux commonly used for soldering and the like can be used.

[0058] Examples of the fluxes mentioned above include zinc chloride, mixtures of zinc chloride and inorganic halides, mixtures of zinc chloride and inorganic acids, molten salts, phosphoric acid, derivatives of phosphoric acid, organic halides, hydrazine, amine compounds, organic acids, and rosin. Only one of these fluxes may be used, or two or more may be used in combination.

[0059] Examples of the above-mentioned molten salt include ammonium chloride. Examples of the above-mentioned organic acid include lactic acid, citric acid, stearic acid, glutamic acid, and glutaric acid. Examples of the above-mentioned rosin include activated rosin and inactivated rosin. The above-mentioned flux may be an organic acid having a carboxyl group, or it may be rosin.

[0060] Examples of organic acids having the carboxyl group mentioned above include glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanediic acid, dodecanediic acid, tridecanediic acid, tetradecanediic acid, pentadecanediic acid, octadecanediic acid, nonadecanedioic acid, and eicosanedioic acid. Among these, adipic acid, suberic acid, sebacic acid, and dodecanediic acid are preferred, with sebacic acid being a prime example.

[0061] The above-mentioned rosin is a rosin whose main component is abietic acid. Examples of such rosins include abietic acid and acrylic-modified rosin.

[0062] Examples of the above-mentioned amine compounds include cyclohexylamine, dicyclohexylamine, benzylamine, benzhydrylamine, imidazole, benzimidazole, phenylimidazole, carboxybenzimidazole, benzotriazole, and carboxybenzotriazole.

[0063] Furthermore, in the present invention, the flux also includes compounds that have the function of a flux that removes oxide films from metal surfaces, i.e., compounds that have reducing properties. Examples of such compounds include compounds that contain one or more phosphorus or sulfur atoms in their molecular structure. Examples of compounds that contain one or more phosphorus or sulfur atoms in their molecular structure include organophosphorus compounds and organosulfur compounds.

[0064] Compounds containing one or more phosphorus or sulfur atoms in their molecular structure can combine with oxygen atoms without producing water, thus removing oxygen atoms from metal oxides. Generally, products with high latent heat of vaporization, such as water, cause violent boiling upon heating, inducing void formation in the structure. Therefore, void formation can be prevented by using a flux that does not contain water in the reaction product.

[0065] Furthermore, compounds containing one or more phosphorus or sulfur atoms in their molecular structure are less prone to hygroscopicity and bleed-out, eliminating the need for flux cleaning after reflow, unlike common fluxes such as carboxylic acids.

[0066] The organophosphorus compound is preferably at least one selected from phosphines and phosphites. Examples of phosphines that can be used include triphenylphosphine, tris(4-methylphenyl)phosphine, methyldiphenylphosphine, diethylphenylphosphine, cyclohexyldiphenylphosphine, 4-(diphenylphosphino)styrene, methylenebis(diphenylphosphine), ethylenebis(diphenylphosphine), trimethylenebis(diphenylphosphine), and tetramethylenebis(diphenylphosphine). In addition, as phosphites, for example, trimethyl phosphite, triethyl phosphite, triisopropyl phosphite, tributyl phosphite, trioctyl phosphite, tris(2-ethylhexyl) phosphite, triisodecyl phosphite, trioleyl phosphite, triphenyl phosphite, tri-p-tolyl phosphite, tris(2,4-di-tert-butylphenyl) phosphite, tristearyl phosphite, tris(nonylphenyl) phosphite, and trilauryl trithiophosphite can be used.

[0067] The organosulfur compound is preferably at least one selected from sulfides, disulfides, trisulfides, and sulfoxides. Examples of sulfides that can be used include bis(4-methacryloylthiophenyl)sulfide, bis(4-hydroxyphenyl)sulfide, bis(4-aminophenyl)sulfide, 2-methylthiophenothiazine, diallyl sulfide, ethyl 2-hydroxyethyl sulfide, diamyl sulfide, hexyl sulfide, dihexyl sulfide, n-octyl sulfide, phenyl sulfide, 4-(phenylthio)toluene, phenyl p-tolyl sulfide, 4-tert-butyldiphenyl sulfide, di-tert-butyl sulfide, diphenylene sulfide, furfuryl sulfide, and bis(2-mercaptoethyl)sulfide. Furthermore, as disulfides, for example, diethyl disulfide, dipropyl disulfide, dibutyl disulfide, amyl disulfide, heptyl disulfide, cyclohexyl disulfide, bis(4-hydroxyphenyl) disulfide, bis(3-hydroxyphenyl) disulfide, diphenyl disulfide, and benzyl disulfide can be used. As trisulfides, for example, dimethyl trisulfide and diisopropyl trisulfide can be used. As sulfoxides, dimethyl sulfoxide, dibutyl sulfoxide, di-n-octyl sulfoxide, methylphenyl sulfoxide, diphenyl sulfoxide, dibenzyl sulfoxide, and p-tolyl sulfoxide can be used.

[0068] In particular, the flux preferably contains at least one of the phosphines represented by the following general formula (1) and the sulfides represented by the following general formula (2). However, in the following general formulas (1) and (2), R independently represents an organic group, and R may be the same or different from each other.

[0069] [ka]

[0070] In the above general formulas (1) and (2), R is preferably independently selected from an alkyl group, an aryl group, an organic group having a functional group, an organic group having a heteroatom, and an organic group having an unsaturated bond, and at least one of R is preferably an aryl group.

[0071] The alkyl group described above may be linear, branched, or cyclic, and may have substituents. The alkyl group is preferably linear or branched. Furthermore, the alkyl group preferably has 3 or more carbon atoms, more preferably 4 to 18 carbon atoms, and even more preferably 6 to 15 carbon atoms. Specific examples of such alkyl groups include propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, stearyl, and isostearyl groups.

[0072] The above aryl group may have substituents, and preferably has 6 to 10 carbon atoms. Examples of such aryl groups include phenyl, tolyl, xyl, cumenyl, and 1-naphthyl groups.

[0073] The organic group having the above-mentioned functional group preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, and even more preferably 1 to 3 carbon atoms. Examples of functional groups that the above-mentioned organic group may have include chloro groups, bromo groups, and fluoro groups. Specifically, examples of organic groups having such functional groups include chloroethyl groups, fluoroethyl groups, chloropropyl groups, dichloropropyl groups, fluoropropyl groups, difluoropropyl groups, chlorophenyl groups, and fluorophenyl groups.

[0074] The organic group having the above heteroatom preferably has 3 or more carbon atoms, more preferably 4 to 18 carbon atoms, and even more preferably 6 to 15 carbon atoms. Examples of heteroatoms in the above organic group include nitrogen atoms, oxygen atoms, sulfur atoms, etc. Specific examples of such organic groups having heteroatoms include dimethylamino group, diethylamino group, diphenylamino group, methyl sulfoxide group, ethyl sulfoxide group, and phenyl sulfoxide group.

[0075] The organic group having the unsaturated bond described above preferably has 3 or more carbon atoms, more preferably 4 to 18 carbon atoms, and even more preferably 6 to 15 carbon atoms. Specific examples of such organic groups having an unsaturated bond include propenyl, propynyl, butenyl, butynyl, oleyl, phenyl, vinylphenyl, and alkylphenyl groups. Among these, having a vinylphenyl group is more preferable.

[0076] Furthermore, in the above general formulas (1) and (2), it is preferable that R independently has one or more selected from vinyl groups, acrylic groups, methacrylic groups, maleic acid ester groups, maleic acid amide groups, maleic acid imide groups, primary amino groups, secondary amino groups, thiol groups, hydrosilyl groups, hydroboron groups, phenolic hydroxyl groups, and epoxy groups as part of itself. In particular, it is more preferable that it has vinyl groups, acrylic groups, methacrylic groups, and secondary amino groups. Specifically, the phosphines preferably include p-styryldiphenylphosphine. Such compounds are preferred because they have a highly reactive vinyl group, resulting in low bleed-out.

[0077] Furthermore, the sulfides preferably include at least one of bis(hydroxyphenyl) sulfide, bis(acryloylthiophenyl) sulfide, 2-methylthiophenothiazine, bis(2-methacryloylthioethyl) sulfide, and bis(methacryloylthiophenyl) sulfide, and more preferably include at least one of bis(acryloylthiophenyl) sulfide and bis(methacryloylthiophenyl) sulfide. These compounds are suitable because they have low bleed-out due to the presence of highly reactive phenolic hydroxyl groups, acrylic groups, and methacrylic groups, and among these, compounds having acrylic groups or methacrylic groups are the most suitable.

[0078] Furthermore, phosphines and sulfides can be used individually, but they may also be used in combination.

[0079] Furthermore, such phosphines and sulfides can form copolymers with maleimide resin when the thermosetting resin described later contains maleimide resin, and therefore also act as thermosetting resin components. In addition, phosphines and sulfides are not highly hygroscopic, have sufficiently large molecular weights, and are polymerizable, so when used as flux components, they can effectively prevent bleed-out. Therefore, by using such phosphines and sulfides instead of easily hygroscopic alcohols and carboxylic acids, the risk of bleed-out can be reduced without undergoing flux washing, and sufficient reliability, especially reflow resistance after moisture absorption, can be ensured.

[0080] The bonding material composition preferably contains flux in a ratio of 0.05 to 0.5 mass% relative to the metal particles (P). If the flux content is less than 0.05 mass%, the Cu2O layer of the first metal particles (P1) cannot be sufficiently removed, resulting in reduced wettability of Sn and decreased reactivity between Sn and the Cu core (C1) of the first metal particles (P1). On the other hand, if the flux content exceeds 0.5 mass%, residual flux will remain, inhibiting the reaction between Sn and the Cu core (C1) of the first metal particles (P1), which is expected to reduce heat resistance, heat dissipation, and conductivity. Furthermore, depending on the type of flux, residual flux may absorb moisture or bleed out, adversely affecting the device, or it may excessively promote the diffusion reaction between Cu and Sn, leading to the growth of diffusion voids, which may reduce the strength and elongation of the bonding material and lower its reliability.

[0081] To achieve a flux content of 0.05 to 0.5 mass% relative to metal particles (P), it is advisable to either modify the surface of the first metal particles (P1) with flux or to add a small amount of flux to the bonding material composition.

[0082] To modify the surface of the first metal particles (P1) with flux, the first metal particles (P1) were immersed in a flux solution, and the flux was coordinated to the surface of the first metal particles (P1) using an ultrasonic device. Using this method, it is not necessary to add flux in excess compared to adding flux to the bonding material composition, and it is possible to minimize the inhibition of the reaction due to flux residue and the influence of flux components on the device, thereby improving reliability.

[0083] The flux content when modifying the surface of the first metal particles (P1) with flux can be adjusted by controlling the output of the ultrasonic device and the stirring time. Furthermore, the flux content when modifying the surface of the first metal particles (P1) with flux can be determined using FT-IR (Fourier transform infrared spectroscopy) measurements.

[0084] (thermosetting resin) When the bonding material composition is formed into a film and used as the bonding material layer of a bonding film, it contains a thermosetting resin. However, when used as a bonding paste, it is preferable that it does not contain a thermosetting resin. The inclusion of a thermosetting resin in the bonding material composition improves film-forming properties and handling when it is formed into a film and used as the bonding material layer of a bonding film. It also improves adhesion to semiconductor elements and lead frames during bonding. Furthermore, in the bonding layer formed by heating the bonding material composition, it plays a role in relieving the stress generated between the semiconductor elements and lead frames due to thermal cycling. For this reason, it is particularly preferable to include a thermosetting resin when the viscosity of the flux is low.

[0085] The thermosetting resin preferably contains a maleimide resin (hereinafter sometimes referred to as "maleimide resin") containing a maleimide compound with two or more imide groups in one molecule, or an epoxy resin having a molecular skeleton derived from a glycidyl ether of an aliphatic diol, particularly from the viewpoint of heat resistance and film-forming properties when metal particles (P) are mixed in, and more preferably contains a maleimide resin. In particular, thermosetting resins containing any of the above resins have excellent stress relaxation properties, which improves the heat resistance of the bonded layer formed by heating the bonding material composition.

[0086] Maleimide resins can be obtained, for example, by condensing maleic acid or its anhydride with a diamine or polyamine. Maleimide resins containing a skeleton derived from an aliphatic amine with 10 or more carbon atoms are preferred from the viewpoint of stress relaxation, and those with 30 or more carbon atoms and a skeleton like the one shown in structural formula (3) below are more preferred. Furthermore, maleimide compounds are preferably those with a number-average molecular weight of 3000 or more.

[0087] [ka]

[0088] The maleimide resin may have its molecular weight and glass transition temperature (Tg) adjusted by including a skeleton derived from an acid component other than maleic acid, such as benzenetetracarboxylic acid or its anhydride, or hydroxyphthalate bisether or its anhydride. Furthermore, phenol novolac resins and radical generators are preferred as curing agents for the maleimide resin.

[0089] Furthermore, suitable maleimide resins include, for example, bismaleimide resins shown in the following structural formulas (4) to (6).

[0090] [ka]

[0091] However, in equation (5) above, n is an integer from 1 to 10. Also, in equations (4) to (6) above, the "X" part is represented by "C" in the following structural formula (7). 36 H 72 This is the framework of ''. In equation (7) below, "*" represents the bonding site with N.

[0092] [ka]

[0093] Furthermore, epoxy resins having a molecular skeleton derived from aliphatic diol glycidyl ethers include, for example, ethylene glycol-modified epoxy resins, propylene glycol-modified epoxy resins, and butanediol-modified epoxy resins. These epoxy resins are preferred from the viewpoint of flexibility. Moreover, it is even more preferable to use such epoxy resins in mixture with bisphenol A type epoxy resins, bisphenol F type epoxy resins, or phenoxy resins, which are epoxy resins with a large molecular weight, from the viewpoint of achieving both adhesive strength and flexibility.

[0094] Furthermore, as curing agents for epoxy resins as described above, acid anhydrides, phenol novolac resins, amines, imidazole compounds, and dicyandiamides can be selected. Among these, phenol novolac resins and imidazole compounds are preferred.

[0095] The thermosetting resin preferably further contains a phenol novolac resin. For example, by using the above-mentioned maleimide resin or epoxy resin in combination with a phenol novolac resin, the phenol novolac resin acts as a curing agent, further improving the adhesion of the thermosetting resin.

[0096] The thermosetting resin content in the bonding material composition according to this embodiment is preferably 4 to 30% by mass, and more preferably 6 to 20% by mass. A thermosetting resin content of 4% by mass or more improves adhesion to semiconductor elements, lead frames, etc., during bonding. Furthermore, the bonded layer formed by heating the bonding material composition exhibits excellent stress relaxation properties between the semiconductor elements and lead frames, etc., due to thermal cycling. If the thermosetting resin content exceeds 30% by mass, heat dissipation may decrease.

[0097] When forming a bonding layer of a bonding film with a bonding material composition, the content of the thermosetting resin in the bonding material composition is preferably 6 to 9% by mass, from the viewpoint of balancing film-forming properties, handling properties, and heat dissipation properties.

[0098] The thermosetting resin may consist of only one type of resin, or it may be a mixture of two or more types of resins. Furthermore, it may contain other resins as needed.

[0099] The bonding material composition preferably contains 80 to 95% by mass of metal particles (P) relative to the total amount of the bonding material composition. If the content of metal particles (P) is less than 80% by mass, the heat dissipation will decrease. If the content of metal particles (P) exceeds 95% by mass, the content of flux and thermosetting resin will decrease, which will reduce the wettability of Sn, the reactivity of Cu and Sn of the first metal particles (P1), the adhesion to semiconductor elements and lead frames during bonding, and the stress relaxation after bonding.

[0100] The bonding material composition according to this embodiment may contain various additives in addition to the above-mentioned components, as long as they do not deviate from the objective of the present invention. Such additives can be appropriately selected as needed, but examples include dispersants, radical polymerization initiators, leveling agents, plasticizers, and the like.

[0101] Next, a method for manufacturing the bonding material composition will be described. The method for manufacturing the bonding material composition is not particularly limited. It can be obtained by mixing the components constituting the bonding material composition described above and then performing further processing such as stirring and dispersion. It is preferable that the flux be modified in advance on the surface of the first metal particles (P1) using the method described above. The apparatus for these mixing, stirring, and dispersion processes is not particularly limited, and can be a three-roll mill, planetary mixer, orbital stirring device, woofer, twin-shaft kneader, thin-layer shear disperser, etc.

[0102] Next, the bonding film according to the present invention will be described. The bonding film has at least a bonding material layer for bonding a semiconductor element and a lead frame, and this bonding material layer is formed using the bonding material composition described above. From the viewpoint of improving film formation properties, the bonding material composition may further contain a solvent.

[0103] The method for forming the bonding layer involves first forming the bonding material composition into a film. The method for forming the bonding material composition into a film is not particularly limited and conventional methods can be used, such as inkjet printing, screen printing, jet printing, dispensers, jet dispensers, comma coaters, slit coaters, die coaters, gravure coaters, slit coats, letterpress printing, intaglio printing, gravure printing, stencil printing, bar coating, applicators, spray coaters, electrodeposition coating, etc.

[0104] The bonding layer is obtained by drying the solvent of a bonding composition formed into a film. Drying methods include drying at room temperature, heating, or reduced pressure drying. For heating or reduced pressure drying, a hot plate, hot air dryer, hot air heating furnace, nitrogen dryer, infrared dryer, infrared heating furnace, far-infrared heating furnace, microwave heating device, laser heating device, electromagnetic heating device, heater heating device, steam heating furnace, hot plate press device, etc. The drying temperature and time are preferably adjusted appropriately according to the type and amount of dispersion medium used; for example, drying at 50 to 180°C for 1 to 120 minutes is preferred.

[0105] The bonding layer may be formed in a film-like manner on the molding substrate and then peeled off. The molding substrate is not particularly limited, but for example, polyethylene terephthalate, polytetrafluoroethylene, polyimide, PEEK, aluminum, glass, alumina, silicon nitride, and stainless steel can be used. Alternatively, a heat-resistant substrate or cloth coated or impregnated with the above materials may be used as the molding substrate.

[0106] The bonding film may have a release film laminated to the surface of the bonding layer to protect the surface of the bonding layer until it is used.

[0107] The bonding layer is preferably 10 to 100 μm thick.

[0108] Next, the above-mentioned bonding material composition and bonding material layer, that is, the method for manufacturing the bonded body, will be described.

[0109] Examples of junctions include semiconductor devices and electronic components. Specific examples of semiconductor devices include power modules, oscillators, amplifiers, and LED modules equipped with diodes, rectifiers, thyristors, MOS (Metal Oxide Semiconductor) gate drivers, power switches, power MOSFETs (Metal Oxide Semiconductor Field-Effect Transistors), IGBTs (Insulated Gate Bipolar Transistors), Schottky diodes, and fast recovery diodes.

[0110] First, the bonding material composition or bonding material layer described above is interposed between the first member and the second member. That is, the portion of the first member that is to be joined with the second member and the portion of the second member that is to be joined with the first member are brought into contact, thereby bonding the first member and the second member via the bonding material composition or bonding material layer. Here, the first member is not particularly limited, but is a support member such as a lead frame, a pre-wired tape carrier, a rigid wiring board, a flexible wiring board, a pre-wired glass substrate, a pre-wired silicon wafer, or a redistribution layer used in a wafer-level CSP (Wafer Level Chip Size Package). The second member is not particularly limited, but can be an active element such as a transistor, diode, light-emitting diode, or thyristor, or a passive element such as a capacitor, resistor, resistor array, coil, or switch. However, the bonding material composition according to the present invention is suitably used for semiconductor elements that operate at high temperatures, particularly power semiconductors.

[0111] Next, the bonding material composition or bonding material layer is heated at 240°C or higher under an inert atmosphere such as nitrogen to form a bonding layer that joins the first member and the second member. The upper limit of the heating temperature is not particularly limited, but is, for example, 300°C or lower. The heating time is preferably 60 to 120 minutes, more preferably 30 to 90 minutes, and even more preferably 5 to 60 minutes.

[0112] For the heat treatment, a hot plate, hot air dryer, hot air heating furnace, nitrogen dryer, infrared dryer, infrared heating furnace, far-infrared heating furnace, microwave heating device, laser heating device, electromagnetic heating device, heater heating device, steam heating furnace, etc. may be used. Furthermore, for the heat and pressure treatment, a hot plate press device or the like may be used, or the above-mentioned heat treatment may be performed while applying pressure.

[0113] When the bonding material composition or bonding material layer is heated, the flux first begins to remove the Cu2O layer covering the Cu of the core (C1) of the first metal particle (P1). When the melting point of Sn is reached, the Sn or Sn-containing solder covering the Cu of the core (C2) of the second metal particle (P2) melts and spreads to wet the surface of the Cu of the core (C2) and the surface of the Cu of the core (C1) of the first metal particle (P1). Then, the Sn reacts with the Cu of the core (C2) to form Cu6Sn5, an intermediate compound of Cu-Sn. Also, Sn and Cu react on the surface of the core (C1) to form Cu6Sn5, an intermediate compound of Cu-Sn. Furthermore, by continuing heating, Cu is supplied to the Cu6Sn5, so Cu3Sn is formed and the bonding layer is formed. The bonding layer preferably has a thickness of 10 to 300 μm.

[0114] In this manner, a joint is manufactured in which the first member and the second member are joined by a bonding layer.

[0115] Here, the Cu of the core (C1) is coated with a Cu2O layer, and as the flux removes the Cu2O layer during heating, the Sn melts, causing the Cu and Sn of the core (C2) to react first. As a result, Cu3Sn is reliably formed inside the second metal particles (P2), and most of the second metal particles (P2) become Cu3Sn particles, although some particles may retain Cu inside.

[0116] Furthermore, the Cu of the core (C1) is coated with a Cu2O layer, and when heated, the flux removes the Cu2O layer while the Sn melts. As a result, the molten Sn spreads uniformly around the first metal particle (P1), and once the Cu2O layer is removed, the Sn reacts with the Cu of the core (C1), forming a uniform Cu3Sn on the surface of the core (C1). Preferably, the first metal particle (P1) has a larger average particle size than the second metal particle (P2). Also, since the reaction between Sn and the Cu of the core (C1) starts later than the reaction inside the second metal particle (P2), Cu remains inside the core (C1).

[0117] As a result, the bonded layer formed by heating the bonding material composition or bonding material layer has a network structure in which Cu particles are bonded together by a compound of Cu and Sn. Therefore, the resulting bonded layer has extremely high shear strength, heat resistance, conductivity, and heat dissipation. [Examples]

[0118] Next, examples of the present invention will be described, but the present invention is not limited to these examples.

[0119] <Raw materials> [First metal particle (P1)] (P1)A: Cu particles (MA series, manufactured by Mitsui Mining & Smelting Co., Ltd.) were heated in an oven at 200°C for 1 hour to obtain metal particles coated with a Cu2O layer. The average particle size (D50) was 5 μm and the degree of oxidation H was 0.05. The degree of oxidation H was determined by measuring the diffraction intensity H1 of the Cu(111) plane and the diffraction intensity H2 of the Cu2O(111) plane using an X-ray diffractometer (X'PertPRO (product name), manufactured by Malvern Panalytical Co., Ltd.), and using the formula H = H2 / (H1 + H2). The average particle size (D50) of the metal particles was measured using a laser diffractometer (SALD-3100 (product name), manufactured by Shimadzu Corporation).

[0120] (P1)B: Cu particles (MA series, manufactured by Mitsui Mining & Smelting Co., Ltd.) were heated in an oven at 180°C for 3 hours to obtain metal particles coated with a Cu2O layer. The average particle size (D50) was 5 μm and the degree of oxidation H was 0.3. The degree of oxidation H and average particle size (D50) were measured in the same manner as in (P1)A.

[0121] (P1)C: Cu particles (MA series, manufactured by Mitsui Mining & Smelting Co., Ltd.) were heated in an oven at 300°C for 40 minutes to obtain metal particles in which the Cu particles were coated with a Cu2O layer. The average particle size (D50) was 5 μm and the degree of oxidation H was 0.5. The degree of oxidation H and average particle size (D50) were measured in the same manner as in (P1)A.

[0122] (P1)D: Cu particles (MA series, manufactured by Mitsui Mining & Smelting Co., Ltd.) were used. The average particle size (D50) was 5 μm, and the degree of oxidation H was 0. The average particle size (D50) was measured in the same manner as in (P1)A.

[0123] (P1)E: Cu particles (MA series, manufactured by Mitsui Mining & Smelting Co., Ltd.) were heated in an oven at 200°C for 1 hour to obtain metal particles coated with a Cu2O layer. The average particle size (D50) was 10 μm and the degree of oxidation H was 0.05. The degree of oxidation H and average particle size (D50) were measured in the same manner as in (P1)A.

[0124] (P1)F: Cu particles (1030Y series, manufactured by Mitsui Mining & Smelting Co., Ltd.) were heated in an oven at 180°C for 4 hours to obtain metal particles in which the Cu particles were coated with a Cu2O layer. The average particle size (D50) was 0.5 μm and the degree of oxidation H was 0.1. The degree of oxidation H and average particle size (D50) were measured in the same manner as in (P1)A.

[0125] (P1)G: Cu particles (MA series, manufactured by Mitsui Mining & Smelting Co., Ltd.) were heated in an oven at 200°C for 40 hours to obtain metal particles in which the Cu particles were coated with a Cu2O layer. The average particle size (D50) was 50 μm and the degree of oxidation H was 0.05. The degree of oxidation H and average particle size (D50) were measured in the same manner as in (P1)A.

[0126] (P1)H: Ag particles (SP series, manufactured by Mitsui Mining & Smelting Co., Ltd.) were used. The average particle size (D50) was 5 μm, and the degree of oxidation H was 0. The average particle size (D50) was measured in the same manner as (P1)A.

[0127] (P1)I: Cu particles (MA series, manufactured by Mitsui Mining & Smelting Co., Ltd.) were heated in an oven at 200°C for 30 hours to obtain metal particles coated with a Cu2O layer. The average particle size (D50) was 25 μm and the degree of oxidation H was 0.05. The degree of oxidation H and average particle size (D50) were measured in the same manner as in (P1)A.

[0128] (P1)J: Cu particles (MA series, manufactured by Mitsui Mining & Smelting Co., Ltd.) were heated in an oven at 170°C for 4 hours to obtain metal particles in which the Cu particles were coated with a Cu2O layer. The average particle size (D50) was 5 μm and the degree of oxidation H was 0.31. The degree of oxidation H and average particle size (D50) were measured in the same manner as in (P1)A.

[0129] (P1)K: Cu particles (1030Y series, manufactured by Mitsui Mining & Smelting Co., Ltd.) were heated in an oven at 170°C for 3 hours to obtain metal particles in which the Cu particles were coated with a Cu2O layer. The average particle size (D50) was 0.5 μm and the degree of oxidation H was 0.07. The degree of oxidation H and average particle size (D50) were measured in the same manner as in (P1)A.

[0130] [Second metal particle (P2)] (P2)A: Cu particles coated with Sn (1050Y series, manufactured by Mitsui Mining & Smelting Co., Ltd.) were used. The average particle size (D50) was 2 μm. The average particle size (D50) was measured in the same manner as in (P1)A.

[0131] (P2)B: Cu particles coated with Sn (1050Y series, manufactured by Mitsui Mining & Smelting Co., Ltd.) were used. The average particle size (D50) was 5 μm. The average particle size (D50) was measured in the same manner as in (P1)A.

[0132] (P2)C: Cu particles coated with SnNiCu (developed product, manufactured by Kyokuto Trading Co., Ltd.) were used. The average particle size (D50) was 2 μm. The average particle size (D50) was measured in the same manner as in (P1)A.

[0133] (P2)D: Cu particles coated with SnNiCu (developed product, manufactured by Kyokuto Trading Co., Ltd.) were used. The average particle size (D50) was 5 μm. The average particle size (D50) was measured in the same manner as in (P1)A.

[0134] (P2)E: Cu particles coated with Sn (1050Y series, manufactured by Mitsui Mining & Smelting Co., Ltd.) were used. The average particle size (D50) was 0.5 μm. The average particle size (D50) was measured in the same manner as in (P1)A.

[0135] (P2)F: Cu particles coated with Sn (1050Y series, manufactured by Mitsui Mining & Smelting Co., Ltd.) were used. The average particle size (D50) was 20 μm. The average particle size (D50) was measured in the same manner as in (P1)A.

[0136] (P2)G: Cu particles coated with In (development product, manufactured by Kyokuto Trading Co., Ltd.) were used. The average particle size (D50) was 2 μm. The average particle size (D50) was measured in the same manner as in (P1)A.

[0137] (P2)H:Sn particles (STC series, manufactured by Mitsui Mining & Smelting Co., Ltd.) were used. The average particle size (D50) was 2 μm. The average particle size (D50) was measured in the same manner as in (P1)A.

[0138] (P2)I: Cu particles coated with Sn (1050Y series, manufactured by Mitsui Mining & Smelting Co., Ltd.) were used. The average particle size (D50) was 12 μm. The average particle size (D50) was measured in the same manner as in (P1)A.

[0139] [Third metallic particle (P3)] (P3)A: Sn particles (ST series, manufactured by Mitsui Mining & Smelting Co., Ltd.) were used. The average particle size (D50) was 5 μm. The average particle size (D50) was measured in the same manner as in (P1)A.

[0140] (P3)B: SnNiCu particles (STC series, manufactured by Mitsui Mining & Smelting Co., Ltd.) were used. The average particle size (D50) was 5 μm. The average particle size (D50) was measured in the same manner as in (P1)A.

[0141] [Thermosetting resin] Thermosetting resin A: Bismaleimide resin (BMI-3000 (trade name), manufactured by DESIGNER MOLECULES INC, number average molecular weight 3000) and polymerization initiator (Nofmer BC (trade name), 2,3-dimethyl-2,3-diphenylbutane, manufactured by Nippon Oil & Fats Co., Ltd.) were mixed in a mass ratio of 100:5 to obtain maleimide resin.

[0142] [Flux] Flux A: Organic sulfides (MPSMA®, bis(4-methacryloylthiophenyl) sulfide, manufactured by Sumitomo Seika Co., Ltd.) Flux B: Phosphine-based (DPPST, p-styryldiphenylphosphine, manufactured by Hokko Sangyo Co., Ltd.)

[0143] <Preparation of bonding material composition (bonding paste)> (Example 1) First, (P1)A was immersed in a solution of flux A, and stirred for 120 minutes at an output of 50W and 3000rpm using an ultrasonic device (NS-56 (product name), manufactured by Microtech Nichion Co., Ltd.) to coordinate the flux to the surface of the first metal particle (P1). The flux content was determined using FT-IR (Fourier transform infrared spectroscopy) measurement. Next, (P1)A and (P2)A modified with the above flux, and cyclopentanone (manufactured by Kanto Chemical Co., Ltd.) as a solvent were mixed and stirred in the proportions shown in Table 1 to obtain the bonding material composition according to Example 1, i.e., bonding paste.

[0144] (Examples 2-4, 10-20, Comparative Examples 1-5) In the same manner as in Example 1, bonding compositions, i.e., bonding pastes, were obtained for Examples 2-4, 10-20, and Comparative Examples 1-5, using the raw materials and mixing ratios shown in Table 1. For Comparative Example 5, the surface of the first metal particles was not modified with flux, and all raw materials were kneaded together.

[0145] (Example 5) First, (P1)A was immersed in a solution of flux B, and the mixture was stirred for 120 minutes at an output of 50W and 3000rpm using an ultrasonic device (NS-56 (product name), manufactured by Microtech Nichion Co., Ltd.) to coordinate the flux to the surface of the first metal particles (P1). Thereafter, in the same manner as in Example 1, the bonding material composition according to Example 5, i.e., bonding paste, was obtained using the raw materials and mixing ratios shown in Table 1.

[0146] (Example 6) In the same manner as in Example 5, a bonding material composition, i.e., bonding paste, according to Example 6 was obtained using the raw materials and mixing ratios shown in Table 1.

[0147] <Preparation of bonding layer> (Example 7) First, (P1)A was immersed in a solution of flux A, and stirred for 120 minutes at an output of 50W and 3000rpm using an ultrasonic device (NS-56 (product name), manufactured by Microtech Nichion Co., Ltd.) to coordinate the flux to the surface of the first metal particle (P1). The flux content was determined using FT-IR (Fourier transform infrared spectroscopy) measurement. Next, (P1)A, (P2)A modified with the above flux, thermosetting resin A, and cyclopentanone (manufactured by Kanto Chemical Co., Ltd.) as a solvent were mixed and stirred in the proportions shown in Table 1, and the mixture was coated onto a Teflon® sheet to a dry film thickness of 100 μm, dried at 100°C for 5 minutes, and peeled off from the Teflon® sheet to obtain the bonding material layer according to Example 7.

[0148] (Examples 8 and 9) In the same manner as in Example 7, bonding layers according to Examples 8 and 9 were obtained using the raw materials and mixing ratios shown in Table 1.

[0149] <Rating> The bonding material compositions (bonding paste) and bonding material layers obtained in the examples and comparative examples described above were subjected to the following characteristic evaluations. The results are shown in Table 1.

[0150] (Examples 1-6, 10-20, Comparative Examples 1-5) [Market share strength] 50 mg of the bonding material composition (bonding paste) according to the above examples and comparative examples was applied to a Cu lead frame. A chip was prepared by dicing an Au-plated Si wafer into a 3 mm square. The chip was placed on the applied bonding material composition (bonding paste) so that the Au plating was in contact with the bonding material composition (bonding paste), and the chip was gently pressed with tweezers to ensure close contact with the bonding material composition (bonding paste) to obtain a laminate. This laminate was fired in a nitrogen atmosphere at 280°C for 15 minutes to obtain a sample for measurement.

[0151] For the obtained measurement samples, a die shear tester (Nordson Advanced Technologies Co., Ltd., Universal Bond Tester Series 4000) was used. The bond tester's scratching tool was impacted against the side of the chip of the measurement sample at 100 μm / s, and the stress at which the chip / lead frame bond broke was measured as the shear strength at 260°C. Samples with a shear strength of 10.0 MPa or higher were evaluated as good products ("○"), those with a shear strength of 3.0 MPa or higher but less than 10.0 MPa were evaluated as acceptable products ("△"), and those with a shear strength of less than 3.0 MPa were evaluated as defective products ("×").

[0152] [Heat resistance] Next, the sample obtained in the same manner as the sample used for measurement above was subjected to a thermal shock test (TCT). One cycle consisted of holding the sample at -65°C for 10 minutes, followed by holding it at 175°C for 10 minutes. This process was repeated 500 times. The shear strength of the sample after this treatment was measured using the same method as the shear strength before TCT. A higher shear strength after TCT indicates better heat resistance. Samples with a shear strength of 7.0 MPa or higher were evaluated as good products ("○"), those between 2.0 MPa and 7.0 MPa were evaluated as acceptable products ("△"), and those below 2.0 MPa were evaluated as defective products ("×").

[0153] [Conductive] 100 mg of the bonding material composition according to the examples and comparative examples was applied to a glass substrate and fired at 280°C for 15 minutes to obtain a sample for measurement. The resistance value of this sample was measured using the four-probe method in accordance with JIS-K7194-1994, and the volume resistivity was calculated. A Rolester GX manufactured by Mitsubishi Chemical Analytech Co., Ltd. was used to measure the resistance value. Note that the reciprocal of volume resistivity is conductivity, and a smaller volume resistivity indicates better conductivity. In this example, the volume resistivity is 1.0 × 10⁻⁶ -5 Items with a diameter of less than Ω·cm are considered good quality and marked with "○", 1.0 × 10 -5 Ω cm or more 5.0×10 -5 Items with a diameter of Ω·cm or less are considered acceptable and are marked with "△", 5.0×10-5 Products exceeding Ω·cm were marked as defective and evaluated with an "×". [Heat dissipation] Thermal conductivity is determined by expressing the volume resistivity as IACS conductivity. The volume resistivity of annealed standard copper is 1.724 × 10⁻⁶. -6 The volume resistivity was expressed as a ratio, with Ω·cm set to 100 IACS%, and the thermal conductivity was calculated relative to copper by dividing this ratio by the thermal conductivity of copper (360 W) at 100 IACS%. A higher thermal conductivity indicates better heat dissipation. In this example, products with a thermal conductivity of 70 W / m·K or higher were evaluated as excellent ("◎"), those with a thermal conductivity of 40 W / m·K or higher but less than 70 W / m·K were evaluated as good ("○"), those with a thermal conductivity of 17 W / m·K or higher but less than 40 W / m·K were evaluated as acceptable ("△"), and those with a thermal conductivity of less than 17 W / m·K were evaluated as defective ("×").

[0154] (Examples 7-9) [Market share strength] The bonding material layers according to Examples 7 to 9 above were placed on a Cu lead frame. Chips were prepared by dicing a gold-plated Si wafer into 3 mm squares, and these chips were placed on the bonding material layer so that the gold plating was in contact with the bonding material layer to obtain a laminate. This laminate was fired in a nitrogen atmosphere at 280°C for 15 minutes to obtain a sample for measurement.

[0155] The obtained measurement samples were used to measure and evaluate their shear strength using the same method as described above.

[0156] [Heat resistance] Next, the shear strength after TCT was measured in the same manner as the measurement sample described above for the measurement sample obtained in the same way as the shear strength after TCT described above, and the heat resistance was evaluated in the same manner.

[0157] [Conductive] The bonding material layers according to Examples 7 to 9 were fired at 280°C for 15 minutes to obtain measurement samples. The volume resistivity of these measurement samples was calculated using the same method as described above, and the conductivity was evaluated using the same method.

[0158] [Heat dissipation] For this measurement sample, the thermal conductivity was calculated using the same method as described above, and the heat dissipation performance was evaluated using the same method.

[0159] [Table 1]

[0160] The bonding material compositions (bonding pastes) and bonding material layers in Examples 1 to 20 use metal particles in which Cu particles are coated with a Cu2O layer and metal particles in which Cu particles are coated with Sn or SnNiCu. Because diffusion is suppressed until the Cu2O layer is reduced, the reaction proceeds slowly and a uniform reaction is achieved overall, resulting in good results in shear strength, heat resistance, conductivity, and heat dissipation.

[0161] In the bonding material composition of Comparative Example 1, Cu particles not coated with a Cu2O layer were used as the first metal particles (P1). As a result, the reaction with molten Sn was good, and the diffusion reaction with the Cu particle surface was not uniformly formed. While a large amount of Cu3Sn was formed in the regions where the reaction had progressed sufficiently, there were also areas where the reaction was insufficient or unreacted. Consequently, a network structure with Cu particles as a core could not be obtained, resulting in inferior heat resistance, conductivity, and heat dissipation.

[0162] In the bonding material composition of Comparative Example 2, since Ag particles with a good oxidation state were used as the first metal particles (P1), the reaction with Sn resulted in a structure in which the Ag3Sn and Cu3Sn regions were separated, resulting in inferior heat resistance and heat dissipation.

[0163] In the bonding material composition of Comparative Example 3, indium-plated Cu particles were used as the second metal particles (P2). Although indium melts at low temperatures, its diffusion reactivity with Cu is poor. As a result, only a partial CuIn compound was formed, leading to inferior heat resistance, conductivity, and heat dissipation.

[0164] In the bonding material composition of Comparative Example 4, pure Sn particles were used as the second metal particles (P2). As a result, the balance between the melting of Sn and the reduction of Cu2O was not maintained, and the molten Sn reacted with Au on the back surface of the Si chip, resulting in insufficient reaction with the Cu particles and inferior heat resistance.

[0165] In Comparative Example 5, the bonding material composition did not use flux, so the reduction of Cu2O did not proceed, and Sn could not react with the Cu core, resulting in the formation of a Cu3Sn structure. Consequently, it was inferior in all aspects: shear strength, heat resistance, conductivity, and heat dissipation.

Claims

1. The material comprises metal particles (P) including first metal particles (P1) and second metal particles (P2), and a flux. The first metal particle (P1) consists of a core (C1) made of Cu and a Cu coating over the core (C1). ２ It is composed of an O layer, The second metal particle (P2) is composed of a core (C2) made of Cu and Sn or solder containing Sn that coats the core (C2). The proportion of Sn in the Sn coating the core (C2) or the Sn-containing solder is 55 to 65% by mass, relative to the total amount of Cu in the core (C1) and the Cu in the core (C2) being 100% by mass. A bonding material composition characterized in that, when the diffraction intensity of the Cu(111) plane of the first metal particle (P1) measured by X-ray diffraction is H1 and the diffraction intensity of the Cu₂O(111) plane is H2, the degree of oxidation H of the first metal particle (P1), represented by the following formula 1, is 0.05 to 0.

3. H=H2 / (H1+H2) [Formula 1]

2. The first metal particle (P1) has an average particle size of 1 to 20 μm. The bonding material composition according to claim 1, characterized in that the second metal particles (P2) have an average particle size of 1 to 10 μm.

3. The metal particles (P) further comprise a third metal particle (P3), The bonding material composition according to claim 1 or 2, characterized in that the third metal particle (P3) is Sn particle or solder particle containing Sn.

4. The bonding material composition according to claim 3, characterized in that the proportion of Sn in the Sn or Sn-containing solder coating the core (C2) and Sn in the Sn particles is 55 to 65% by mass, relative to 100% by mass of the total amount of Cu in the core (C1) and Cu in the core (C2).

5. The bonding material composition according to any one of claims 1 to 4, characterized in that the flux is reducing and the reaction product does not contain water.

6. The bonding material composition according to any one of claims 1 to 5, characterized in that the flux comprises at least one of phosphines represented by the following general formula (1) and sulfides represented by the following general formula (2). However, in the following general formulas (1) and (2), R independently represents an organic group, and R may be the same or different from each other.

7. The bonding material composition according to any one of claims 1 to 6, characterized in that the content ratio of the flux with respect to the metal particles (P) is 0.05 to 0.5% by mass.

8. The bonding material composition according to any one of claims 1 to 7, characterized in that the content ratio of metal particles (P) is 80 to 95% by mass with respect to the total amount of the bonding material composition.

9. A bonding layer is formed that joins the first member and the second member by heating at 240°C or higher. The bonding material composition according to any one of claims 1 to 8, characterized in that the bonding layer has a network structure in which Cu particles are bonded together by a compound of Cu and Sn.

10. The bonding material composition according to any one of claims 1 to 9, characterized in that it contains a thermosetting resin.

11. A method for producing a bonding material composition according to any one of claims 1 to 10, characterized in that it includes a step of mixing and stirring the first metal particles (P1) and the second metal particles (P2).

12. A bonding film having a bonding material layer, A bonded film characterized in that the bonding layer is formed using the bonding composition described in any one of claims 1 to 10.

13. The bonding film according to claim 12, characterized in that the bonding material layer has a thickness of 10 to 100 μm.

14. A method for manufacturing a bonded body, comprising joining a first member and a second member with a bonding layer using the bonding material composition described in any one of Claims 1 to 10, A method for manufacturing a bonded body, characterized in that the bonding material composition is interposed between the first member and the second member and heated at 240°C or higher, the flux removes the Cu2O layer of the first metal particles (P1), the Sn or solder containing Sn of the second metal particles (P2) melts and reacts with the Cu of the core (C1) and the Cu of the core (C2), forming a bonding layer having a network structure in which Cu particles are bonded by a compound of Cu and Sn.

15. A method for manufacturing a bonded body, wherein a first member and a second member are joined by a bonding layer using the bonding film described in Claim 12 or Claim 13, A method for manufacturing a bonded body, characterized in that the bonding material layer is interposed between the first member and the second member and heated at 240°C or higher, the flux removes the Cu2O layer of the first metal particles (P1), the Sn or solder containing Sn of the second metal particles (P2) melts and reacts with the Cu of the core (C1) and the Cu of the core (C2), forming a bonding layer having a network structure in which Cu particles are bonded by a compound of Cu and Sn.

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