Silver powder, method for manufacturing the same, metal paste for joining, and method for manufacturing joined body

Abstract

To provide silver powder capable of imparting excellent thermal conductivity to a metal joined layer formed by low-temperature sintering.SOLUTION: The present invention is silver powder in which a maximum exothermic peak in thermogravimetry differential thermal analysis appears at 175-210°C, a ratio of Ig-Loss to a BET specific surface area is less than 0.25, a volume-based median diameter D50 by laser diffraction method is 0.50-2.00 μm, and a ratio of the D50 to a BET diameter DBET is 3.50 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a silver powder and a method for producing the same, a bonding metal paste, and a method for producing a bonded body. [Background technology]

[0002] In recent years, it has been proposed to use a silver paste containing silver microparticles as a bonding material, and to bond the objects to be bonded by heating the bonding material between the objects to be bonded, thereby sintering the silver in the bonding material (for example, Patent Documents 1 and 2, etc.).

[0003] For example, when using the above-mentioned bonding material to fix an electronic component such as a Si chip on a metal substrate such as a copper substrate, first, a metal paste in which silver powder is dispersed in a solvent is applied to the metal substrate to form a coating film, and the resulting coating film is dried and sintered to form a metal bonding layer, and the electronic component can be bonded to the metal substrate via the resulting metal bonding layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-80147 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-8332 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the metal paste described above is used to form a metal bonding layer by sintering at a low temperature (for example, 300° C. or lower), there is room for improvement in the thermal conductivity of the resulting metal bonding layer.

[0006] Therefore, an object of the present invention is to provide a silver powder that can impart excellent thermal conductivity to a metal bonding layer formed by low-temperature sintering, and a method for producing the same. Another object of the present invention is to provide a metal bonding paste that can impart excellent thermal conductivity to a metal bonding layer formed by low-temperature sintering, and a method for manufacturing a bonded body using the same. [Means for solving the problem]

[0007] As a result of extensive research by the present inventors to solve the above-mentioned problems, the present inventors have completed the present invention described below.

[0008] That is, the gist and configuration of the present invention for solving the above-mentioned problems is as follows.

[0009] [1] The maximum exothermic peak in thermogravimetric differential thermal analysis occurs between 175°C and 210°C, The ratio of Ig-loss to BET specific surface area is less than 0.25, Volume-based cumulative 50% diameter D by laser diffraction method 50 is 0.50 μm or more and 2.00 μm or less, BET diameter D BET Regarding the above D 50 The silver powder has a ratio of 3.50 or less.

[0010] [2] The BET specific surface area is 0.90 m 2 / g or more 2.50m 2 / g or less.

[0011] [3] The silver powder according to [1] or [2], wherein the Ig-loss is 0.15% by mass or more and 0.55% by mass or less.

[0012] [4] A method for producing a silver powder according to any one of [1] to [3], a reduction step of adding a reducing agent to the silver-containing solution to precipitate first silver particles; a surface treatment agent addition step of adding a surface treatment agent to the mixed solution containing the first silver particles to obtain second silver particles; a separation step of separating the second silver particles from the mixed solution and drying them to obtain silver powder; A method for producing silver powder, comprising:

[0013] [5] A metal bonding paste containing the silver powder according to any one of [1] to [3].

[0014] [6] A coating film forming step of applying the bonding metal paste according to [5] to a first member to obtain a coating film; a dry film forming step of drying the coating film at a temperature of 80°C or higher and 150°C or lower to obtain a dry film; a sintering step of sintering the dried film at a temperature of 180°C or higher and 300°C or lower to form a metal bonding layer, and bonding a second member to the first member via the metal bonding layer; A method for producing a bonded body, comprising:

[0015] [7] The method for producing a bonded body according to [6], wherein in the dry film forming step, the second member is placed on the coating film and dried.

[0016] [8] The method for producing a joined body according to [6], wherein in the sintering step, the second member is placed on the dry film and sintered.

[0017] [9] The method for producing a bonded body according to any one of [6] to [8], wherein the sintering step is carried out in a nitrogen gas atmosphere. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a silver powder capable of imparting excellent thermal conductivity to a metal bonding layer formed by low-temperature sintering, and a method for producing the same. Furthermore, the present invention can provide a metal bonding paste that can impart excellent thermal conductivity to a metal bonding layer formed by low-temperature sintering, and a method for manufacturing a bonded body using the same. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 2 is a diagram showing TG curves of the silver powders according to Examples 1 to 5. [Figure 2] FIG. 2 is a diagram showing DTA curves of the silver powders according to Examples 1 to 5. [Figure 3]It is a diagram showing the TG curves of the silver powders according to Examples 6 to 9. [Figure 4] It is a diagram showing the DTA curves of the silver powders according to Examples 6 to 9. [Figure 5] It is a diagram showing the TG curves of the silver powders according to Comparative Examples 1 and 2. [Figure 6] It is a diagram showing the DTA curves of the silver powders according to Comparative Examples 1 and 2. [Figure 7] It is a schematic diagram explaining the evaluation method of the shear strength in Examples 5, 6, 8, 9, and Comparative Example 2.

Mode for Carrying Out the Invention

[0020] (Terms and Measurement Methods) First, prior to the description of the embodiments, terms and measurement methods etc. in this specification will be explained.

[0021] <Thermogravimetric Differential Thermal Analysis> 25 mg of silver powder was subjected to thermogravimetric differential thermal analysis (TG-DTA analysis) by a differential thermal - thermogravimetric simultaneous measurement device (TG-DTA device) (Thermo Plus EVO2 TG-8120 manufactured by Rigaku Corporation) by heating from room temperature (25°C) to 500°C at a heating rate of 10°C / min in the atmosphere.

[0022] <BET Specific Surface Area> The "BET specific surface area" was measured by the BET one - point method by nitrogen adsorption using a specific surface area device (Macsorb HM - model 1210 manufactured by MOUNTECH) that employs the BET method. In addition, for the measurement of the BET specific surface area, the sample weight was 3.0 g, a N2 / He (30 / 70) mixed gas was used, the gas flow rate was 25 mL / min, and the degassing conditions before measurement were 60°C for 10 minutes.

[0023] <BET Diameter D BET > BET Diameter D BET (Hereinafter, it may be simply referred to as "D BET "). (Unit: μm) is the BET specific surface area (unit: m 2 / g) and true density (unit: g / cm 3 ) and was calculated using the following formula: D BET =6 / (BET specific surface area x true density)

[0024] <True density measurement> Silver powder was filled into a 10 cc platinum crucible, and the mass of the filled silver powder was precisely measured. Then, using a dry automatic density meter (Micromeritics, Inc., device name: AccuPyc II 1340), the volume of the mass-measured silver powder was measured by the constant volume expansion method (the "gas pycnometer method" in the Japanese Pharmacopoeia), and the density was calculated. Note that the true density was measured by including the closed voids inside the silver particles that were not connected to the outside.

[0025] <Particle size distribution> The volume-based cumulative 10% particle diameter D10, cumulative 50% particle diameter D50, and cumulative 90% particle diameter D90 of the silver powder were measured using a laser diffraction / scattering particle size distribution analyzer (Microtrac MT-3300 EXII, manufactured by Microtrac-Bell Corporation). For the measurements, 0.1 g of sample (silver powder) was added to 40 mL of a 1% by mass polyvinylpyrrolidone (PVP) solution (solvent: isopropyl alcohol) and dispersed. An ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd., model US-150T; 19.5 kHz, tip diameter 18 mm) was used for dispersion. The dispersion time was 2 minutes. The dispersed sample was loaded into the above-mentioned analyzer, and the particle size distribution was determined using the attached analysis software. During the measurements, an SDC device was used as the circulator for the laser diffraction / scattering particle size distribution analyzer, and the "flow rate (%)" setting for the circulator was set to 60. In the following, the cumulative 10% particle diameter D on a volume basis measured by laser diffraction method is 10 , Cumulative 50% particle size D 50 , and cumulative 90% particle diameter D 90 , respectively, simply "D 10 "," "D 50 " and "D 90 "It is sometimes referred to as ".

[0026] <DBET Ratio of D to 50 (D 50 / D BET ) > The silver powder may be such that the individual particles are not completely separated and a plurality of particles are in an aggregated state. In the measurement of the particle size by the laser diffraction method, the particle size of the aggregated particles is measured for the aggregated particles. On the other hand, the BET single point method measures the specific surface area using the amount of gas adsorbed on the particles, and the BET diameter converted from this specific surface area indicates the particle size (particle diameter) of the particles assuming that the measured particles are true spheres. In the case of a state with less aggregation and close to monodispersion, the ratio (D 50 / D BET ) approaches 1.

[0027] <Loss on Ignition (Ig-loss)> Indicates the amount of mass change when heated from room temperature (about 25 °C) to 800 °C. Specifically, it serves as an index of the amount of compositions other than silver in the silver powder, and is an index indicating the amount of residual components in the silver powder, for example, residual components such as treatment agents and additives used in the manufacturing process of the silver powder. The "Loss on Ignition (Ig-loss)" is calculated from "Loss on Ignition (Ig-loss) value (mass %) = (w1 - w2) / w1 × 100", where the silver powder sample is precisely weighed (weighing value: w1), placed in a magnetic crucible, heated to 800 °C, and held at 800 °C for 30 minutes as a sufficient time to reach a constant weight, then cooled and weighed again (weighing value: w2).

[0028] <Ratio of Ig-loss to BET specific surface area (Ig-loss / BET specific surface area)> The ratio of Ig-loss to the BET specific surface area is the value obtained by dividing the value of Ig-loss in the silver powder in mass % by the value of the BET specific surface area of the silver powder in m 2 / g. In this specification, although the description of the units of "Ig-loss" / "BET specific surface area" is omitted, the unit is "mass %·g / m 2 ".

[0029] <Gum arabic> As used herein, "gum arabic" refers to an acidic polysaccharide obtained from the sap of a legume plant belonging to the genus Acacia, and whose constituent sugars are galactose, L-arabinose, L-rhamnose, and glucuronic acid.

[0030] (Silver powder) The silver powder of the present invention exhibits a maximum exothermic peak at 175°C or higher and 210°C or lower in the above-mentioned thermogravimetric differential thermal analysis, has an Ig-loss ratio to BET specific surface area of less than 0.25, and has a volume-based cumulative 50% diameter D 50 is 0.50 μm or more and 2.00 μm or less, and the BET diameter D BET D against 50 The ratio is 3.50 or less. The above-mentioned silver powder can impart excellent thermal conductivity to the metal bonding layer formed by low-temperature sintering. The reason for this is presumed to be as follows.

[0031] First, the cumulative 50% diameter D 50 is 0.50 μm or more and 2.00 μm or less, and the BET diameter D BET D against 50 A silver powder having a ratio of 3.50 or less can effectively suppress aggregation in a metal paste and is useful from the standpoint of safety and paste shelf life (dispersibility). On the other hand, a metal bonding layer formed using a metal paste containing such silver powder may have reduced thermal conductivity. By controlling the maximum exothermic peak in thermogravimetric differential thermal analysis to 175°C or higher, excessive solidification of a coating film formed from a metal paste containing the silver powder of the present invention can be prevented when the coating film is dried. By controlling the maximum exothermic peak in gravimetric differential thermal analysis to 210°C or lower, a metal bonding layer with low volume resistivity can be obtained even when the dried film is fired at low temperatures. By controlling the ratio of Ig-loss to BET specific surface area to less than 0.25, the amount of impurities can be reduced, thereby reducing the volume resistivity of the metal bonding layer. Therefore, it is presumed that excellent thermal conductivity can be imparted to a metal bonding layer formed by low-temperature sintering. According to the Wiedemann-Franz law, there is a correlation between volume resistivity and thermal conductivity, and the lower the volume resistivity, the higher the thermal conductivity tends to be. Therefore, the lower the volume resistivity of the metal bonding layer, the better the thermal conductivity of the metal bonding layer.

[0032] The maximum exothermic peak in the thermogravimetric differential thermal analysis of silver powder is not particularly limited as long as it occurs between 175°C and 210°C, and may be an exothermic peak accompanied by a weight loss, an exothermic peak accompanied by a weight increase, or an exothermic peak without weight change, but is preferably an exothermic peak accompanied by a weight loss.

[0033] The ratio of Ig-loss to BET specific surface area is not particularly limited as long as it is less than 0.25, but from the viewpoint of dispersibility of the silver powder in the metal paste, it is preferably 0.10 or more. Note that, since closed voids are not usually observed inside the silver powder of the present invention and the surface treatment agent is thought to adhere mainly to the surfaces of the silver particles, the ratio of Ig-loss to BET specific surface area can be thought of as a value that roughly indicates the amount of surface treatment agent per unit area of the silver powder.

[0034] The BET specific surface area of silver powder is 0.90m 2 / g or more, and 1.00m 2 / g or more is more preferable, and 1.10m 2 / g or more is even more preferable. 2 / g or less, and 2 It is more preferable that the saturation coefficient is 1 / g or less. BET specific surface area is 0.90m 2 If the SiO2 content is 1 / g or more, the contact area between particles in the metal bonding layer can be sufficiently secured, and the thermal conductivity of the metal bonding layer can be improved. On the other hand, the BET specific surface area is 2.50m 2 If the content is 0.15 wt. / g or less, the viscosity of the metal paste can be maintained at a good level.

[0035] The Ig-loss of the silver powder is preferably 0.15% by mass or more, more preferably 0.17% by mass or more, and is preferably 0.55% by mass or less, more preferably 0.50% by mass or less. If the Ig-loss is 0.15 mass % or more, aggregation of particles in the metal paste can be suppressed, and dispersibility can be improved. On the other hand, if the Ig-loss is 0.55 mass % or less, the reduction in thermal conductivity of the metal bonding layer due to excess impurities can be effectively suppressed.

[0036] Silver Powder D 50 is 0.50 μm or more, preferably more than 0.60 μm, and is 2.00 μm or less, preferably 1.90 μm or less, and more preferably 1.50 μm or less. D 50 If the particle size is 0.50 μm or more, an increase in the viscosity of the paste can be effectively suppressed. On the other hand, D 50 If the particle size is 2.00 μm or less, the dispersibility of the silver powder can be improved.

[0037] Silver Powder D 10 is preferably 0.10 μm or more, more preferably 0.20 μm or more, and is preferably 0.80 μm or less, more preferably 0.60 μm or less. D 10 If the particle size is 0.10 μm or more, an increase in the viscosity of the paste can be effectively suppressed. On the other hand, D 10 If the particle size is 0.80 μm or less, the dispersibility of the silver powder can be improved.

[0038] Silver Powder D 90 is preferably 0.90 μm or more, more preferably 1.00 μm or more, and is preferably 4.50 μm or less, more preferably 3.50 μm or less. D 90 If the particle size is 0.90 μm or more, an increase in the viscosity of the paste can be effectively suppressed. On the other hand, D 90If the particle size is 4-50 μm or less, the dispersibility of the silver powder can be improved.

[0039] Silver Powder D BET is preferably 0.10 μm or more, more preferably 0.20 μm or more, and is preferably 0.70 μm or less, more preferably 0.55 μm or less. D BET If the particle size is 0.10 μm or more, an increase in the viscosity of the paste can be effectively suppressed. On the other hand, D BET If the particle size is 0.70 μm or less, the dispersibility of the silver powder can be improved.

[0040] Silver Powder D BET D against 50 The ratio is 3.50 or less, preferably 3.30 or less, and more preferably 3.00 or less. In addition, the D of silver powder BET D against 50 The ratio is usually 1.00 or greater.

[0041] In one embodiment, the silver powder of the present invention may contain a surface treatment agent. The surface treatment agent is not particularly limited as long as the silver powder satisfies the above-mentioned requirements, but examples thereof include gum arabic, polyacrylic acid and its salts, octanoic acid, lauric acid, and decanoic acid. That is, the silver powder of the present invention may contain, as a surface treatment agent, at least one selected from the group consisting of gum arabic, polyacrylic acid and its salts, octanoic acid, lauric acid, and decanoic acid.

[0042] (Silver powder manufacturing method) The silver powder of the present invention described above can be obtained by a method for producing silver powder, which includes a reduction step in which a reducing agent is added to a silver-containing solution to precipitate first silver particles, a surface treatment agent addition step in which a surface treatment agent is added to a mixed solution containing the first silver particles to obtain second silver particles, and a separation step in which the second silver particles are separated from the mixed solution and dried to obtain silver powder. The method for producing silver powder of the present invention may optionally include steps other than the reduction step, the surface treatment agent addition step, and the separation step described above.

[0043] <Reduction process> In the reduction step, a reducing agent is added to the silver-containing solution to precipitate first silver particles. The silver-containing solution is usually an aqueous solution or suspension containing a silver compound, including water as a solvent. The mixture after precipitating the primary silver particles (the mixture containing the primary silver particles) is usually a suspension (so-called slurry) or dispersion in which the primary silver particles are dispersed.

[0044] The silver compound contained in the silver-containing solution is not particularly limited and examples thereof include silver nitrate, silver oxide, etc. It is also preferable to use, as the silver compound, a silver ammine complex obtained by reacting silver nitrate or silver oxide with aqueous ammonia or an ammonium salt.

[0045] Examples of reducing agents to be added to the silver-containing solution include hydrazine, hydrazine compounds, formalin, etc. Among these, hydrazine is preferred.

[0046] In the reduction step, it is preferable to optionally add a pH adjuster to the silver-containing solution before adding the reducing agent. Adding a pH adjuster to the silver-containing solution makes it easy to adjust the particle size of the resulting silver powder. Common acids or bases may be used as pH adjusters, such as nitric acid and sodium hydroxide. The amount of pH adjuster added can be adjusted appropriately depending on the silver nitrate aqueous solution used. Examples of methods for adjusting the amount of pH adjuster include conducting a level test on the particle size of the silver powder depending on the amount of pH adjuster added and adjusting the amount added.

[0047] In the reduction step, it is preferable to optionally add an azole to the silver-containing solution before adding the reducing agent. By adding an azole to the silver-containing solution, the particle size of the resulting silver powder can be easily adjusted. Examples of azoles include imidazole, oxazole, thiazole, selenazole, pyrazole, isoxazole, isothiazole, 1H-1,2,3-triazole, 2H-1,2,3-triazole, 1H-1,2,4-triazole, 4H-1,2,4-triazole, 1,2,3-oxadiazole, 1,2,4-oxadiazole, 1,2,5-oxadiazole, 1,3,4-oxadiazole, and 1,2, Examples of the azoles include 3-thiadiazole, 1,2,4-thiadiazole, 1,2,5-thiadiazole, 1,3,4-thiadiazole, 1H-1,2,3,4-tetrazole, 1,2,3,4-oxatriazole, 1,2,3,4-thiatriazole, 2H-1,2,3,4-tetrazole, 1,2,3,5-oxatriazole, 1,2,3,5-thiatriazole, indazole, benzimidazole, and benzotriazole. Salts of these azoles can also be used. Examples of the salts include sodium salts and potassium salts. Of the above, sodium benzotriazole is preferred.

[0048] <Surface treatment agent addition process> In the surface treatment agent addition step, a surface treatment agent is added to the mixture containing the first silver particles obtained in the reduction step to obtain second silver particles.

[0049] As the surface treatment agent, the surface treatment agents explained in the above section "Silver powder" can be used.

[0050] The amount of the surface treatment agent added in the surface treatment agent addition step is usually 0.4% by mass or more and 2.0% by mass or less relative to the mass of silver contained in the mixed solution obtained in the reduction step.

[0051] The surface treatment agent may be added to the mixture after being diluted with a diluent. Examples of the diluent include water; alcohols such as methanol and ethanol; etc. Note that a mixed solution containing ethanol as the main component, such as so-called neoethanol, can also be used as the diluent for the surface treatment agent.

[0052] <Separation process> In the separation step, the second silver particles obtained in the surface treatment agent addition step are separated from the mixed liquid and dried to obtain silver powder. The silver powder obtained in the separation step can be the silver powder of the present invention. In addition, the separation step may optionally include a washing and recovery step in which the separated second silver particles are recovered and washed.

[0053] In the washing and recovery step, for example, the separated aggregates of second silver particles are formed into a cake, and the cake of aggregates of second silver particles is washed. Washing in the washing and recovery step may be performed using, for example, pure water. Dehydration in the washing and recovery step may be performed by, for example, decantation or a filter press. The end point of washing may be determined using the electrical conductivity of the washing water. Specifically, the end of washing may be determined when the electrical conductivity of the washing water becomes a predetermined value or less. The second silver particles after washing may be subjected to a drying step in an aggregated state such as a cake.

[0054] In the drying step, aggregates of the second silver particles, etc., which contain a solvent such as water and are in an aggregated state, are dried. The drying step may be performed by vacuum drying or using an airflow dryer. In the drying step, a high-pressure air flow may be blown onto the aggregates of the second silver particles, etc., or the cake or silver powder in the drying process may be placed in a mixer having a stirring rotor and stirred, thereby applying a dispersing force to the cake or silver powder in the drying process and promoting dispersion and drying.

[0055] In the drying step, the temperature of the silver powder is usually 100° C. or less. If the temperature of the silver powder is 100° C. or less, the second silver particles and the like in the silver powder can be effectively prevented from sintering with each other.

[0056] Since the dried silver powder may be in the form of clumps, a dry crushing treatment or classification operation may be carried out simultaneously with or after the drying step in order to improve the handleability of the silver powder. Here, improving the handleability of the silver powder means, for example, ensuring fluidity to the extent that it does not interfere with the supply operation into the apparatus, or loosening the silver powder to an appropriate extent so that processing in the apparatus proceeds efficiently.

[0057] The method for dry crushing is not particularly limited and can be appropriately selected depending on the purpose. However, it is preferable to use a crusher that rotates a stirring blade to crush the silver powder and fluidize it, and for example, a Henschel mixer, a sample mill, a blender, a coffee mill, or the like can be used.

[0058] (Metallic paste for joining) The metal bonding paste of the present invention contains the silver powder of the present invention described above. Because the metal bonding paste of the present invention contains the silver powder of the present invention, it can impart excellent thermal conductivity to a metal bonding layer formed by low-temperature sintering. The metal paste for bonding of the present invention usually contains a dispersion solvent, and may optionally contain additives.

[0059] The dispersion solvent contained in the bonding metal paste is not particularly limited, and examples thereof include protic polar solvents such as water and alcohol; and aprotic polar solvents such as ketones (e.g., acetone) and cyclic ethers (e.g., tetrahydrofuran). Here, the dispersion solvent is preferably a solvent containing oxygen atoms. The solvent containing oxygen atoms is not particularly limited, but is preferably an alcohol (for example, a C1-18 alcohol, etc.), and more specifically, butanol, pentanol, hexanol, heptanol, octanol, isobornylcyclohexanol, terpineol, octanediol, decanol, nonanol, undecanol, etc. are more preferred. The alcohol may also include polyhydric alcohols such as diols and triols.

[0060] The metal paste for bonding of the present invention can optionally contain known additives within the range that does not affect the sinterability or bonding strength of the metal paste for bonding. Examples of optional additives include dispersants such as acid dispersants and phosphate ester dispersants, sintering accelerators, antioxidants, viscosity modifiers, binders such as organic binders (e.g., resin binders) and inorganic binders, pH adjusters, buffers, antifoaming agents, leveling agents, and volatilization inhibitors.

[0061] The metal bonding paste of the present invention can be produced by kneading the silver powder of the present invention, the dispersion solvent, and any additives by a known method. The kneading method is not particularly limited, and the metal bonding paste can be produced, for example, by preparing each component individually and kneading them in any order using ultrasonic dispersion, a disperser, a three-roll mill, a ball mill, a bead mill, a biaxial kneader, or a revolutionary mixer.

[0062] (Method of manufacturing a bonded body) The method for manufacturing a bonded body of the present invention includes a coating film forming step of applying the above-mentioned bonding metal paste of the present invention onto a first member to obtain a coating film, a drying film forming step of drying the coating film at a temperature of 80°C or higher and 150°C or lower to obtain a dry film, and a sintering step of sintering the dry film at a temperature of 180°C or higher and 300°C or lower to form a metal bonding layer, and bonding a second member to the first member via the metal bonding layer. In the method for producing a bonded body as described above, a metal bonding layer having excellent thermal conductivity is formed using the bonding metal paste of the present invention, and therefore the resulting bonded body has excellent performance.

[0063] A bonded body obtained by the method for manufacturing a bonded body of the present invention typically comprises a first member, a metal bonding layer formed using the bonding metal paste of the present invention, and a second member, with the first member and the second member bonded via the metal bonding layer. Examples of applications of the bonded body include power modules, power amplifiers for communications, power LEDs, and thermoelectric power generation modules.

[0064] The first member can be appropriately selected depending on the application of the bonded body, and a substrate can be used. Examples of the substrate include a metal substrate such as a copper substrate, an alloy substrate of copper and some other metal (for example, W (tungsten) or Mo (molybdenum)), a ceramic substrate in which a copper plate is sandwiched between SiN (silicon nitride) or AlN (aluminum nitride), a plastic substrate such as a PET (polyethylene terephthalate) substrate, and a printed wiring board. A laminated substrate in which these are laminated can also be used.

[0065] The portion of the first member to which the bonding metal paste is applied may be plated with a metal, and from the viewpoint of bonding compatibility with the silver component in the coating film, the metal plating is preferably silver plating or gold plating.

[0066] The second member can be selected appropriately depending on the application of the bonded body, and can be a substrate similar to the substrates listed for the first member. Alternatively, the second member can be a semiconductor element such as a Si chip, a SiC chip, a GaN chip, an LED element, or a thermoelectric power generation element.

[0067] The portion of the second member that is in contact with the metal bonding layer may be plated with a metal, and from the viewpoint of bonding compatibility with the silver component in the metal bonding layer, the metal plating is preferably silver plating or gold plating.

[0068] Hereinafter, the coating film forming step, the dry film forming step, and the sintering step included in the manufacturing method of the bonded body of the present invention will be described. However, the manufacturing method of the bonded body of the present invention is not limited to including only these steps, and may optionally include steps other than the coating film forming step, the dry film forming step, and the sintering step.

[0069] <Coating film formation process> In the coating film forming step, the bonding metal paste of the present invention is applied onto a first member to obtain a coating film.

[0070] The method for applying the bonding metal paste onto the first member is not particularly limited, and examples thereof include a metal mask, a dispenser, and a screen printing method.

[0071] The thickness of the coating film is usually 10 μm or more and 500 μm or less. The area of the coating film in contact with the first member is usually 1 mm 2 More than 5000mm 2 The following is the result.

[0072] <Dry film formation process> In the dry film forming step, the coating film obtained in the coating film forming step is dried at a temperature of 80° C. or higher and 150° C. or lower to obtain a dry film. By drying the coating film at a temperature of 80°C or higher and 150°C or lower, the dispersion solvent derived from the bonding metal paste contained in the coating film can be effectively volatilized while effectively preventing the silver powder from sintering. The drying temperature of the coating film is preferably 100°C or higher, more preferably 110°C or higher, and is preferably 140°C or lower, more preferably 130°C or lower.

[0073] The drying time of the coating film is preferably 5 minutes or more, more preferably 10 minutes or more, and is preferably 30 minutes or less, more preferably 20 minutes or less. If the drying time of the coating film is 5 minutes or more, the solvent can be dried effectively. On the other hand, if the drying time of the coating film is 30 minutes or less, productivity can be improved.

[0074] The drying step may be carried out in air or in an inert gas atmosphere, but is preferably carried out in an inert gas atmosphere from the viewpoint of preventing sintering of the particles. Examples of inert gases include nitrogen gas; rare gases such as argon gas; and the like, but nitrogen gas is preferred from the viewpoint of cost. That is, the drying step is preferably carried out in a nitrogen gas atmosphere from the viewpoint of preventing sintering of the particles and from the viewpoint of cost. In this specification, the term "inert gas atmosphere" refers to an atmosphere filled with an inert gas, and has an oxygen concentration of less than 300 ppm.

[0075] In one embodiment, in the dry film forming step, a second member may be placed on the coating film and dried. That is, before the coating film is dried, the second member may be placed on the coating film so as to be in contact with the coating film. In this way, the coating film and the second member can be effectively adhered to each other even under pressure-free conditions. In this specification, "under no pressure" means that drying is performed without applying any pressure to the coating film other than the weight of the first member or the second member. Drying the coating film under no pressure can reduce the manufacturing costs of the bonded body.

[0076] <Sintering process> In the sintering step, the dry film obtained in the dry film forming step is sintered at a temperature of 180°C or higher and 300°C or lower to form a metal bonding layer, and the second member is bonded to the first member via the metal bonding layer. If the dried film is sintered at a temperature of 180° C. or higher and 300° C. or lower, deterioration of the first member and the second member can be effectively suppressed. The sintering temperature of the dried film is preferably 200°C or higher, more preferably 220°C or higher, and is preferably 280°C or lower, more preferably 260°C or lower.

[0077] In the sintering step, the dried film may be sintered while being pressed, if necessary. The pressure (gauge pressure) when pressing is usually 1 MPa or more and 30 MPa or less.

[0078] Here, the difference between the sintering temperature of the dried film and the drying temperature of the coating film ("sintering temperature of the dried film" - "drying temperature of the coating film") is 30°C or higher, preferably 50°C or higher, more preferably 70°C or higher, and even more preferably 90°C or higher, and is 220°C or lower, preferably 200°C or lower, more preferably 180°C or lower, and even more preferably 160°C or lower.

[0079] The sintering time of the dried film is preferably 3 minutes or more, more preferably 5 minutes or more, and is preferably 60 minutes or less, more preferably 30 minutes or less. If the sintering time of the dried film is 3 minutes or more, the bonding strength can be improved. On the other hand, if the sintering time of the dried film is 60 minutes or less, productivity can be improved.

[0080] The sintering process may be carried out in air or in an inert gas atmosphere, but is preferably carried out in an inert gas atmosphere because oxidation of the metal can be effectively prevented when joining to the surface of a joining member that is easily oxidized, such as copper. Examples of inert gases include nitrogen gas and rare gases such as argon gas, but nitrogen gas is preferred from the viewpoint of cost. That is, the sintering process is preferably carried out in a nitrogen gas atmosphere from the viewpoint of preventing oxidation of the surface of the joining member.

[0081] In one embodiment, a second member may be placed on the dried film and sintered in the sintering step. That is, after the coating film is dried in the drying step, the second member may be placed on the dried film so as to be in contact with the dried film. This more effectively volatilizes the dispersion solvent derived from the bonding metal paste contained in the coating film, effectively suppresses the generation of voids in the metal bonding layer formed by sintering the dried film, and improves the thermal conductivity of the metal bonding layer. [Example]

[0082] The present invention will be described in more detail below using examples, but the present invention is not limited to the following examples in any way. The thermogravimetric differential thermal analysis, BET specific surface area, true density measurement, particle size distribution, and loss on ignition (Ig-loss) were measured or calculated by the methods described above.

[0083] Example 1 First, 3363.4 g of a silver nitrate aqueous solution containing 44.8 g of silver was stirred at 210 rpm, while 76.6 g of 28 mass% industrial ammonia water (manufactured by Junsei Chemical Co., Ltd.) was added to obtain a silver ammine complex aqueous solution. Next, while continuing stirring, 2.9 g of a 67.5 mass% nitric acid aqueous solution (manufactured by Asahi Kasei Corporation) was added as a pH adjuster to the obtained silver ammine complex aqueous solution, followed by 12.4 g of a 1.1 mass% aqueous solution of benzotriazole sodium (manufactured by Shipro Kasei Co., Ltd.) as an azole. The liquid temperature was adjusted to 35°C, and 5 minutes after the addition of the ammonia water, 93.8 g of a 7.0 mass% aqueous solution of hydrazine (manufactured by Mitsubishi Gas Chemical Company, Inc.) was added all at once to obtain a slurry containing first silver particles. Next, 10 seconds after the addition of the reducing agent, 4.5 g of a 10% by mass aqueous solution of gum arabic (MP Gokyo Food & Chemical Co., Ltd.) (gum arabic content: 0.45 g, 1.00% by mass relative to the silver) was added as a surface treatment agent to the resulting slurry containing the first silver particles, and the mixture was stirred for 180 seconds to obtain a slurry containing second silver particles. Note that a baffled reaction chamber and a two-stage turbine blade were used for the reaction. Thereafter, stirring was stopped to allow the second silver particles to settle, and the liquid in which the second silver particles had precipitated was filtered, washed with water until the electrical conductivity of the liquid after passing through the water was 0.5 mS / m or less, and then vacuum dried at 73° C. The dried silver powder obtained was milled using a sample mill (Kyoritsu Riko Co., Ltd., SK-M10) with 50 g of silver added, and crushed twice for 30 seconds using a dial scale of 100, to obtain the silver powder according to Example 1. Various measurements were carried out using the silver powder of Example 1. The results are shown in Table 1. In addition, FIG. 1 shows the TG curve of the silver powder of Example 1, and FIG. 2 shows the DTA curve of the silver powder of Example 1.

[0084] (Thermal conductivity of metal bonding layer) A metal bonding paste was prepared by mixing 27.9 g of the silver powder according to Example 1 and 2.1 g of octanol four times at 1400 rpm for 30 seconds using a planetary mixer (EME V-mini300). The resulting metal bonding paste was then printed onto an alumina substrate using a metal mask (10 mm long x 10 mm wide, 50 μm thick) to form a coating film. The resulting coating film was then dried at 120°C for 15 minutes in a nitrogen atmosphere using a small inert gas oven (JTEKT Thermo Systems KLO-30NH) to form a dry film. The temperature was then increased at 4°C / min to 250°C, after which the dry film was fired for 1 hour to form a metal bonding layer. The coating film was dried and sintered after purging with nitrogen at a flow rate of 40 L / min for 10 minutes to reduce the oxygen concentration to less than 300 ppm. For the metal bonding layer obtained above, the sheet resistance was measured using a resistivity meter (Loresta GX MCP-T700 manufactured by Nitto Seiko Analytech Co., Ltd.), the film thickness was measured using a surface roughness measuring instrument (Surfcocom 480B-12 manufactured by Tokyo Seimitsu Co., Ltd.), and the volume resistivity was calculated using the following formula. Volume resistance [μΩ cm] = sheet resistance [Ω / □] x film thickness [μm] x 10 -2 The smaller the volume resistance, the better the thermal conductivity of the metal bonding layer.

[0085] Example 2 First, 3,376 g of a silver nitrate aqueous solution containing 45.3 g of silver was stirred at 210 rpm, while 76.6 g of 28 mass% industrial ammonia water (manufactured by Junsei Chemical Co., Ltd.) was added to obtain a silver ammine complex aqueous solution. Next, while continuing stirring, 2.9 g of a 67.5 mass% nitric acid aqueous solution (manufactured by Asahi Kasei Corporation) was added as a pH adjuster to the obtained silver ammine complex aqueous solution, followed by 2.5 g of a 1.1 mass% aqueous solution of benzotriazole sodium (manufactured by Shipro Kasei Co., Ltd.) as an azole. The liquid temperature was adjusted to 35°C, and 5 minutes after the addition of the ammonia water, 93.8 g of a 7.0 mass% aqueous solution of hydrazine (manufactured by Mitsubishi Gas Chemical Company, Inc.) was added all at once to obtain a slurry containing first silver particles. Next, 10 seconds after the addition of the reducing agent, 2.7 g of a 10 mass% solution of octanoic acid (Wako Pure Chemical Industries, Ltd.) in neoethanol (Daishin Chemical Co., Ltd.) (octanoic acid content: 0.27 g, 0.6 mass% relative to silver) was added as a surface treatment agent to the resulting slurry containing the first silver particles, and the mixture was stirred for 180 seconds to obtain a slurry containing the second silver particles. Note that a baffled reaction chamber and a two-stage turbine blade were used for the reaction. Thereafter, stirring was stopped to allow the second silver particles to settle, and the liquid in which the second silver particles had precipitated was filtered and washed with water until the electrical conductivity of the liquid after passing through the water was 0.5 mS / m or less, and then vacuum dried at 73° C. The dried silver powder obtained was milled using a sample mill (Kyoritsu Riko Co., Ltd., SK-M10) with 50 g of silver added, and the milled powder was milled twice for 30 seconds using a dial scale of 100, to obtain the silver powder of Example 2. Various measurements were performed and the thermal conductivity of the metal bonding layer was evaluated using the silver powder of Example 2. The results are shown in Table 1. FIG. 1 shows the TG curve of the silver powder of Example 2, and FIG. 2 shows the DTA curve of the silver powder of Example 2.

[0086] (Comparative Example 1) First, 3364.5 g of a silver nitrate aqueous solution containing 44.8 g of silver was stirred at 210 rpm, while 76.6 g of 28 mass% industrial ammonia water (manufactured by Junsei Chemical Co., Ltd.) was added to obtain a silver ammine complex aqueous solution. Next, while continuing stirring, 2.9 g of a 67.5 mass% nitric acid aqueous solution (manufactured by Asahi Kasei Corporation) was added as a pH adjuster to the obtained silver ammine complex aqueous solution, followed by 12.4 g of a 1.1 mass% aqueous solution of benzotriazole sodium (manufactured by Shipro Kasei Co., Ltd.) as an azole. The liquid temperature was adjusted to 35°C, and 5 minutes after the addition of the ammonia water, 93.8 g of a 7.0 mass% aqueous solution of hydrazine (manufactured by Mitsubishi Gas Chemical Company, Inc.) was added all at once to obtain a slurry containing first silver particles. Next, 10 seconds after adding the reducing agent to the resulting slurry containing the first silver particles, 3.4 g of a 10 mass% solution of ricinoleic acid (manufactured by Ito Oil Mills) in neoethanol (manufactured by Taishin Chemical Co., Ltd.) was added as a surface treatment agent (ricinoleic acid content: 0.34 g, 0.76 mass% relative to silver) and stirred for 180 seconds to obtain a slurry containing second silver particles. Note that a baffled reaction chamber and a two-stage turbine blade were used for the reaction. Thereafter, stirring was stopped to allow the second silver particles to settle, and the liquid in which the second silver particles had precipitated was filtered, washed with water until the electrical conductivity of the liquid after passing through the water was 0.5 mS / m or less, and then vacuum dried at 73° C. The dried silver powder obtained was milled using a sample mill (Kyoritsu Riko Co., Ltd., SK-M10) with 50 g of silver added, and crushed twice for 30 seconds using a dial scale of 100, to obtain the silver powder according to Comparative Example 1. Various measurements were performed and the thermal conductivity of the metal bonding layer was evaluated using the silver powder of Comparative Example 1. The results are shown in Table 1. FIG. 5 shows the TG curve of the silver powder of Comparative Example 1, and FIG. 6 shows the DTA curve of the silver powder of Comparative Example 1.

[0087] [Table 1]

[0088] Example 3 First, 3277.3 g of a silver nitrate aqueous solution containing 45.3 g of silver was stirred at 196 rpm, while 137.9 g of 28 mass% industrial ammonia water (manufactured by Junsei Chemical Co., Ltd.) was added to obtain a silver ammine complex aqueous solution. Next, while continuing to stir, the liquid temperature of the obtained silver ammine complex aqueous solution was adjusted to 25°C, and 3 minutes after the addition of the ammonia water, 118.2 g of an 8.0 mass% aqueous hydrazine solution (manufactured by Mitsubishi Gas Chemical Company, Inc.) was added all at once to obtain a slurry containing first silver particles. Next, 3 seconds after adding the reducing agent to the resulting slurry containing the first silver particles, 21.1 g of a 2.1 mass% aqueous solution of sodium polyacrylate (Aron (registered trademark) A-210, manufactured by Toagosei Co., Ltd., weight average molecular weight: 2000) (sodium polyacrylate content: 0.45 g, 0.99 mass% relative to silver) was added as a surface treatment agent, and the mixture was stirred for 180 seconds to obtain a slurry containing second silver particles. Note that a baffled reaction chamber and a two-stage turbine blade were used for the reaction. Thereafter, stirring was stopped to allow the second silver particles to settle, and the liquid in which the second silver particles had precipitated was filtered, washed with water until the electrical conductivity of the liquid after passing through the water was 0.5 mS / m or less, and then vacuum dried at 73° C. The dried silver powder obtained was milled using a sample mill (Kyoritsu Riko Co., Ltd., SK-M10) with 50 g of silver added, and crushed twice for 30 seconds using a dial scale of 100, to obtain the silver powder according to Example 3. Various measurements were performed and the thermal conductivity of the metal bonding layer was evaluated using the silver powder of Example 3. The results are shown in Table 2. In addition, Fig. 1 shows the TG curve of the silver powder of Example 3, and Fig. 2 shows the DTA curve of the silver powder of Example 3.

[0089] Example 4 First, 3277.3 g of a silver nitrate aqueous solution containing 45.3 g of silver was stirred at 196 rpm, while 137.9 g of 28 mass% industrial ammonia water (manufactured by Junsei Chemical Co., Ltd.) was added to obtain a silver ammine complex aqueous solution. Next, while continuing to stir, the liquid temperature of the obtained silver ammine complex aqueous solution was adjusted to 25°C, and 3 minutes after the addition of the ammonia water, 118.2 g of an 8.0 mass% aqueous hydrazine solution (manufactured by Mitsubishi Gas Chemical Company, Inc.) was added all at once to obtain a slurry containing first silver particles. Next, 3 seconds after adding the reducing agent to the resulting slurry containing the first silver particles, 21.1 g of a 2.1 mass% aqueous solution of sodium polyacrylate (Aron (registered trademark) T-50, manufactured by Toagosei Co., Ltd., weight average molecular weight: 6000) (sodium polyacrylate content: 0.45 g, 0.99 mass% relative to silver) was added as a surface treatment agent, and the mixture was stirred for 180 seconds to obtain a slurry containing second silver particles. Note that a baffled reaction chamber and a two-stage turbine blade were used for the reaction. Thereafter, stirring was stopped to allow the second silver particles to settle, and the liquid in which the second silver particles had precipitated was filtered, washed with water until the electrical conductivity of the liquid after passing through the water was 0.5 mS / m or less, and then vacuum dried at 73° C. The dried silver powder obtained was milled using a sample mill (Kyoritsu Riko Co., Ltd., SK-M10) with 50 g of silver added, and crushed twice for 30 seconds using a dial scale of 100, to obtain the silver powder of Example 4. Various measurements were performed and the thermal conductivity of the metal bonding layer was evaluated using the silver powder of Example 4. The results are shown in Table 2. In addition, Fig. 1 shows the TG curve of the silver powder of Example 4, and Fig. 2 shows the DTA curve of the silver powder of Example 4.

[0090] Example 5 First, 3330.7 g of a silver nitrate aqueous solution containing 45.3 g of silver was stirred at 196 rpm, while 102.2 g of 28 mass% industrial ammonia water (manufactured by Junsei Chemical Co., Ltd.) was added to obtain a silver ammine complex aqueous solution. Next, while continuing to stir, the liquid temperature of the obtained silver ammine complex aqueous solution was adjusted to 25°C, and 3 minutes after the addition of the ammonia water, 118.2 g of 8.0 mass% aqueous hydrazine water (manufactured by Mitsubishi Gas Chemical Company, Inc.) was added all at once to obtain a slurry containing first silver particles. Next, 3 seconds after adding the reducing agent to the obtained slurry containing the first silver particles, 3.6 g of a 5.0 mass% solution of lauric acid (Wako Pure Chemical Industries, Ltd.) in neoethanol (Daishin Chemical Co., Ltd.) (lauric acid content: 0.18 g, 0.40 mass% relative to silver) was added as a surface treatment agent, and the mixture was stirred for 180 seconds to obtain a slurry containing second silver particles. Note that a baffled reaction chamber and a two-stage turbine blade were used for the reaction. Thereafter, the stirring was stopped to allow the second silver particles to settle, and the liquid in which the second silver particles had precipitated was filtered and washed with water until the electrical conductivity of the liquid after passing through the filter was 0.5 mS / m or less, and then vacuum dried at 73° C. The dried silver powder obtained was milled using a sample mill (Kyoritsu Riko Co., Ltd., SK-M10) with 50 g of silver added, and the milled powder was milled twice for 30 seconds using a dial scale of 100, to obtain the silver powder of Example 5. Various measurements were performed and the thermal conductivity of the metal bonding layer was evaluated using the silver powder of Example 5. The results are shown in Table 2. In addition, Fig. 1 shows the TG curve of the silver powder of Example 5, and Fig. 2 shows the DTA curve of the silver powder of Example 5.

[0091] (Bonding strength of metal bonding layer) <Preparation of metal bonding layer for evaluation> A 10mm x 10mm x 1mm silver-plated copper plate was washed with ethanol and purified water, and a 5mm x 5mm x 0.3mm Si chip with a gold back electrode was prepared. A 50µm thick metal mask was then placed on the silver-plated copper plate, and the bonding metal paste prepared in the evaluation of the thermal conductivity of the metal bonding layer was printed on the silver-plated copper plate to form a 5.5mm x 5.5mm coating. The coating was then dried at 120°C for 15 minutes using a hot-air dryer (Espec LC-114). The Si chip was then placed on the dried coating and placed in a pressure bonding machine (Dowa Electronics). The Si chip was then sintered at 200°C for 3 minutes under a pressure of 10MPa to form a metallic bonding layer. This metallic bonding layer sintered the silver in the bonding metal paste, and the Si chip was then bonded to the silver-plated copper plate.

[0092] <Shear strength evaluation> The bond strength of the test pieces obtained above was measured using a bond tester SERIES4000Plus (manufactured by Nordson Dage) as shown in FIG. Specifically, the test piece consisted of a copper substrate 3, a metal bonding layer 2 formed thereon, and a Si element 1 formed thereon and bonded to the copper substrate 3 via the metal bonding layer 2. A force was applied horizontally to the copper substrate 3 from the side of the Si element 1 using a shear tool 4 set at 5 mm / min, and the force at which the Si element 1 broke was divided by the area of the bottom surface of the Si element 1 to determine the shear strength of the test piece, which was taken as the bonding strength of the metal bonding layer 2. The above test was performed so that the bottom end of the shear tool 4 was in contact with a position 50 μm above the copper substrate 3. The results are shown in Table 2.

[0093] Example 6 First, 3294.9 g of an aqueous silver nitrate solution containing 45.4 g of silver was stirred at 196 rpm, while 137.9 g of 28 mass% industrial ammonia water (manufactured by Junsei Chemical Co., Ltd.) was added to obtain an aqueous silver ammine complex solution. Next, while continuing to stir, the liquid temperature of the obtained aqueous silver ammine complex solution was adjusted to 25°C, and 3 minutes after the addition of the aqueous ammonia, 118.2 g of an 8.0 mass% aqueous hydrazine solution (manufactured by Mitsubishi Gas Chemical Company, Inc.) was added all at once to obtain a slurry containing first silver particles. Next, 3 seconds after adding the reducing agent to the resulting slurry containing the first silver particles, 3.6 g of a 5.0 mass% solution of decanoic acid (Wako Pure Chemical Industries, Ltd.) in neoethanol (Daishin Chemical Co., Ltd.) (decanoic acid content: 0.18 g, 0.40 mass% relative to silver) was added as a surface treatment agent, and the mixture was stirred for 180 seconds to obtain a slurry containing second silver particles. Note that a baffled reaction chamber and a two-stage turbine blade were used for the reaction. Thereafter, stirring was stopped to allow the second silver particles to settle, and the liquid in which the second silver particles had precipitated was filtered and washed with water until the electrical conductivity of the liquid after passing through the filter was 0.5 mS / m or less, and then vacuum dried at 73° C. The dried silver powder obtained was milled using a sample mill (Kyoritsu Riko Co., Ltd., SK-M10) with 50 g of silver added, and the milled powder was milled twice for 30 seconds using a dial scale of 100, to obtain the silver powder of Example 6. Various measurements were performed using the silver powder of Example 6, and the thermal conductivity of the metal bonding layer and the bonding strength of the metal bonding layer were evaluated. The results are shown in Table 2. In addition, Fig. 3 shows the TG curve of the silver powder of Example 6, and Fig. 4 shows the DTA curve of the silver powder of Example 6.

[0094] Example 7 First, 3294.3 g of a silver nitrate aqueous solution containing 45.3 g of silver was stirred at 196 rpm, while 137.9 g of 28 mass% industrial ammonia water (manufactured by Junsei Chemical Co., Ltd.) was added to obtain a silver ammine complex aqueous solution. Next, while continuing stirring, the liquid temperature of the obtained silver ammine complex aqueous solution was adjusted to 25°C, and 3 minutes after the addition of the ammonia water, 118.2 g of 8.0 mass% aqueous hydrazine (manufactured by Mitsubishi Gas Chemical Company, Inc.) was added all at once to obtain a slurry containing first silver particles. Next, 3 seconds after the addition of the reducing agent, 2.1 g of an aqueous solution of 21.4 mass% ammonium polyacrylate (Aron (registered trademark) A-30SL, weight average molecular weight: 6000, manufactured by Toagosei Co., Ltd.) (ammonium polyacrylate content: 0.45 g, 0.99 mass% relative to silver) was added as a surface treatment agent to the obtained slurry containing the first silver particles, and the mixture was stirred for 180 seconds to obtain a slurry containing the second silver particles. Note that a baffled reaction chamber and a two-stage turbine blade were used for the reaction. Thereafter, stirring was stopped to allow the second silver particles to settle, and the liquid in which the second silver particles had precipitated was filtered and washed with water until the electrical conductivity of the liquid after passing through the filter was 0.5 mS / m or less, and then vacuum dried at 73° C. The dried silver powder obtained was milled using a sample mill (Kyoritsu Riko Co., Ltd., SK-M10) with 50 g of silver added, and the milled powder was milled twice for 30 seconds using a dial scale of 100, to obtain the silver powder of Example 7. Various measurements were performed and the thermal conductivity of the metal bonding layer was evaluated using the silver powder of Example 7. The results are shown in Table 2. In addition, Fig. 3 shows the TG curve of the silver powder of Example 7, and Fig. 4 shows the DTA curve of the silver powder of Example 7.

[0095] Example 8 First, 3293 g of a silver nitrate aqueous solution containing 45.3 g of silver was stirred at 196 rpm, while 137.9 g of 28 mass% industrial ammonia water (manufactured by Junsei Chemical Co., Ltd.) was added to obtain a silver ammine complex aqueous solution. Next, while continuing to stir, the liquid temperature of the obtained silver ammine complex aqueous solution was adjusted to 25°C, and 3 minutes after the addition of the ammonia water, 118.2 g of an 8.0 mass% aqueous hydrazine solution (manufactured by Mitsubishi Gas Chemical Company, Inc.) was added all at once to obtain a slurry containing first silver particles. Next, 3 seconds after adding the reducing agent to the resulting slurry containing the first silver particles, 4.5 g of a 10% by mass aqueous solution of gum arabic (MP Gokyo Food & Chemical Co., Ltd.) (gum arabic content: 0.45 g, 0.99% by mass relative to the silver) was added as a surface treatment agent, and the mixture was stirred for 180 seconds to obtain a slurry containing second silver particles. Note that a baffled reaction chamber and a two-stage turbine blade were used for the reaction. Thereafter, stirring was stopped to allow the second silver particles to settle, and the liquid in which the second silver particles had precipitated was filtered and washed with water until the electrical conductivity of the liquid after passing through the water was 0.5 mS / m or less, and then vacuum dried at 73° C. The dried silver powder obtained was milled using a sample mill (Kyoritsu Riko Co., Ltd., SK-M10) with 50 g of silver added, and the milled powder was milled twice for 30 seconds using a dial scale of 100, to obtain the silver powder of Example 8. Various measurements were performed using the silver powder of Example 8, and the thermal conductivity of the metal bonding layer and the bonding strength of the metal bonding layer were evaluated. The results are shown in Table 2. In addition, Fig. 3 shows the TG curve of the silver powder of Example 8, and Fig. 4 shows the DTA curve of the silver powder of Example 8.

[0096] Example 9 First, 3294.8 g of an aqueous silver nitrate solution containing 45.3 g of silver was stirred at 196 rpm, while 137.9 g of 28 mass% industrial ammonia water (manufactured by Junsei Chemical Co., Ltd.) was added to obtain an aqueous silver ammine complex solution. Next, while continuing to stir, the liquid temperature of the obtained aqueous silver ammine complex solution was adjusted to 25°C, and 3 minutes after the addition of the aqueous ammonia, 118.2 g of an 8.0 mass% aqueous hydrazine solution (manufactured by Mitsubishi Gas Chemical Company, Inc.) was added all at once to obtain a slurry containing first silver particles. Next, 8 seconds after adding the reducing agent to the resulting slurry containing the first silver particles, 3.6 g of a 5.0 mass% solution of octanoic acid (Wako Pure Chemical Industries, Ltd.) in neoethanol (Daishin Chemical Co., Ltd.) (octanoic acid content: 0.18 g, 0.40 mass% relative to silver) was added as a surface treatment agent and stirred for 180 seconds to obtain a slurry containing second silver particles. Note that a baffled reaction chamber and a two-stage turbine blade were used for the reaction. Thereafter, stirring was stopped to allow the second silver particles to settle, and the liquid in which the second silver particles had precipitated was filtered and washed with water until the electrical conductivity of the liquid after passing through the filter was 0.5 mS / m or less, and then vacuum dried at 73° C. The dried silver powder obtained was milled using a sample mill (Kyoritsu Riko Co., Ltd., SK-M10) with 50 g of silver added, and the milled powder was milled twice for 30 seconds using a dial scale of 100, to obtain the silver powder of Example 9. Various measurements were performed using the silver powder of Example 9, and the thermal conductivity of the metal bonding layer and the bonding strength of the metal bonding layer were evaluated. The results are shown in Table 2. In addition, Fig. 3 shows the TG curve of the silver powder of Example 9, and Fig. 4 shows the DTA curve of the silver powder of Example 9.

[0097] (Comparative Example 2) First, 3351.5 g of a silver nitrate aqueous solution containing 45.2 g of silver was stirred at 200 rpm while 137.7 g of 28 mass% industrial ammonia water (manufactured by Junsei Chemical Co., Ltd.) was added to obtain a silver ammine complex aqueous solution. Next, while continuing stirring, 42.0 g of a 20 mass% aqueous sodium hydroxide solution (manufactured by Tosoh Corporation) was added as a pH adjuster to the obtained silver ammine complex aqueous solution, the liquid temperature of the obtained silver ammine complex aqueous solution was adjusted to 25°C, and 2 minutes after the addition of the ammonia water, 127.7 g of a 7.0 mass% aqueous hydrazine solution (manufactured by Mitsubishi Gas Chemical Company, Inc.) was added all at once to obtain a slurry containing first silver particles. Next, 5 seconds after adding the reducing agent, 2.3 g of a 5.0 mass% solution of ricinoleic acid (manufactured by Ito Oil Mills) in neoethanol (manufactured by Taishin Chemical Co., Ltd.) was added as a surface treatment agent (ricinoleic acid content: 0.23 g, 0.51 mass% relative to silver) and stirred for 180 seconds to obtain a slurry containing second silver particles. Note that a baffled reaction chamber and a two-stage turbine blade were used for the reaction. Thereafter, stirring was stopped to allow the second silver particles to settle, and the liquid in which the second silver particles had precipitated was filtered, washed with water until the electrical conductivity of the liquid after passing through the water was 0.5 mS / m or less, and then vacuum dried at 73° C. The dried silver powder obtained was milled using a sample mill (Kyoritsu Riko Co., Ltd., SK-M10) with 50 g of silver added, and crushed twice for 30 seconds using a dial scale of 100, to obtain the silver powder according to Comparative Example 2. Various measurements were performed using the silver powder of Comparative Example 2, and the thermal conductivity of the metal bonding layer and the bonding strength of the metal bonding layer were evaluated. The results are shown in Table 2. In addition, Fig. 5 shows the TG curve of the silver powder of Comparative Example 2, and Fig. 6 shows the DTA curve of the silver powder of Comparative Example 2.

[0098] [Table 2]

[0099] As is clear from Tables 1 and 2, the maximum exothermic peak in thermogravimetric differential thermal analysis appears at 175°C or higher and 210°C or lower, the ratio of Ig-loss to BET specific surface area is less than 0.25, and the volume-based cumulative 50% diameter D 50 is 0.50 μm or more and 2.00 μm or less, and the BET diameter D BET D against 50 It can be seen that silver powders having a ratio of 3.50 or less can impart excellent thermal conductivity to metal bonding layers formed by low-temperature sintering. Furthermore, as is clear from Table 2, it can be seen that the above silver powders can impart excellent bonding strength to metal bonding layers. [Industrial Applicability]

[0100] According to the present invention, it is possible to provide a silver powder capable of imparting excellent thermal conductivity to a metal bonding layer formed by low-temperature sintering, and a method for producing the same. Furthermore, the present invention can provide a metal bonding paste that can impart excellent thermal conductivity to a metal bonding layer formed by low-temperature sintering, and a method for manufacturing a bonded body using the same. [Explanation of symbols]

[0101] 1. Si element 2 Metal bonding layer 3 Copper substrate 4 Shear Tools

Claims

1. The maximum exothermic peak in thermogravimetric differential thermal analysis occurs at 175°C or higher and 210°C or lower, The ratio of Ig-loss to BET specific surface area is less than 0.25; Volume-based cumulative 50% diameter D by laser diffraction method ５０ is 0.50 μm or more and 2.00 μm or less, BET diameter D ＢＥＴ The above D ５０ The silver powder has a ratio of 3.50 or less.

2. The BET specific surface area is 0.90 m ２ / g or more 2.50m ２ The silver powder according to claim 1, wherein the silver content is 1 / g or less.

3. The silver powder according to claim 1, wherein the Ig-loss is 0.15% by mass or more and 0.55% by mass or less.

4. The method for producing the silver powder according to any one of claims 1 to 3, a reduction step of adding a reducing agent to the silver-containing solution to precipitate first silver particles; a surface treatment agent addition step of adding a surface treatment agent to the mixed solution containing the first silver particles to obtain second silver particles; a separation step of separating the second silver particles from the mixed solution and drying them to obtain silver powder; A method for producing silver powder, comprising:

5. A metal bonding paste comprising the silver powder according to any one of claims 1 to 3.

6. a coating film forming step of applying the bonding metal paste according to claim 5 onto a first member to obtain a coating film; a dry film forming step of drying the coating film at a temperature of 80°C or higher and 150°C or lower to obtain a dry film; a sintering step of sintering the dried film at a temperature of 180° C. or higher and 300° C. or lower to form a metal bonding layer, and bonding a second member to the first member via the metal bonding layer; A method for producing a bonded body, comprising:

7. The method for manufacturing a bonded body according to claim 6 , wherein in the dry film forming step, the second member is placed on the coating film and dried.

8. The method for manufacturing a joined body according to claim 6 , wherein in the sintering step, the second member is placed on the dry film and sintered.

9. The method for producing a bonded body according to claim 6, wherein the sintering step is carried out in a nitrogen gas atmosphere.

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