JP6923063B2 - Silver paste and its manufacturing method and joint manufacturing method - Google Patents

Description

The present invention relates to a silver paste for joining electronic parts, a method for producing the silver paste, and a method for producing a bonded body using the silver paste.

Conventionally, silver paste has been used to convert semiconductor elements such as high-power LED elements and power semiconductor elements, and electronic components such as semiconductor packages into copper or copper alloy members that are substrates such as DBC substrates (copper-clad substrates) and lead frames. A silver paste containing silver powder, a thermosetting resin, and a solvent is used for adhering and fixing (die bonding) to the surface.

As this type of silver paste, for example, a thermally conductive composition containing silver powder, silver fine particles, fatty acid silver, amine and silver resinate is disclosed (see, for example, Patent Document 1). In this thermally conductive composition, the silver powder has an average particle size of 0.3 μm to 100 μm, the silver fine particles have an average particle size of 50 to 150 nm, and the silver fine particles have an average particle size of 20 to 50 nm. Yes, and the ratio of the average particle size to the crystallite size is 1 to 7.5. This thermally conductive composition further contains an alcohol solvent such as methanol, ethylene glycol, and propylene glycol for adjusting the viscosity and the like. Patent Document 1 describes that a heat conductive composition having a high thermal conductivity can be obtained with the heat conductive composition configured as described above.

As another silver paste, it contains silver fine particles having an average particle size of 1 to 200 nm and an organic solvent containing a low swelling organic solvent having a blanket swelling rate of 2.0% or less, and contains a low swelling organic solvent. A conductive paste having a ratio of 3.0 to 30 wt% is disclosed (see, for example, Patent Document 2). In Patent Document 2, in this conductive paste, it is preferable that an organic component is attached to at least a part of the surface of the silver fine particles, and this organic component is an amine from the viewpoint of dispersibility and conductivity of the silver fine particles. And it is stated that it is preferable to contain a carboxylic acid. Further, in Patent Document 2, as the low swelling organic solvent having a blanket swelling rate of 2.0% or less, a solvent having a hydroxyl group as a functional group is preferable, for example, a polyhydric alcohol having a plurality of hydroxyl groups, and others. Examples of the polyhydric alcohol having a monohydric alcohol solvent and 2 to 3 hydroxyl groups include glycerin, 1,2,4-butanetriol, 1,2,6-hexanetriol, and ethylene. It is described that glycol, diethylene glycol, 1,2-butanediol, propylene glycol, 2-methylpentane-2,4-diol and the like can be mentioned. Patent Document 2 describes that this conductive paste can form a fine conductive pattern having sufficient conductivity and good adhesion to a substrate.

Japanese Patent No. 5872545 (Claim 1, paragraph [0006], paragraph [0051]) Japanese Patent No. 6329703 (claim 1, paragraph [0010], paragraph [0034], paragraph [0035], paragraph [0052], paragraph [0055], paragraph [0056])

_{An oxide film of CuO or CuO 2} is likely to be formed on the surface of a copper or copper alloy member such as a DBC substrate (copper-clad substrate) or a lead frame to which a silver paste layer is applied. Therefore, a metallized layer such as silver plating or nickel plating is formed on the surface of a copper or copper alloy member, a silver paste is applied on the metallized layer, and electronic parts such as a chip element are bonded. However, when the silver paste shown in Patent Documents 1 and 2 is bonded to an electronic component such as a chip element without forming a metallized layer, it is difficult to bond the electronic component to a copper or a copper alloy member with high strength. there were. Therefore, there has been a demand for a silver paste capable of directly forming a silver paste layer and joining electronic components with high strength without providing a metallized layer on the surface of a copper or copper alloy member.

An object of the present invention is a silver paste that directly forms a bonding layer on the surface of a copper or copper alloy member that does not have a metallized layer such as silver plating or nickel plating to bond electronic parts with high strength, a method for producing the same, and bonding. To provide a method of manufacturing the body.

A first aspect of the present invention is a silver paste containing silver powder, fatty acid silver, an aliphatic amine, a high dielectric constant alcohol having a dielectric constant of 30 or more, and a solvent having a dielectric constant of less than 30.

The second aspect of the present invention is an invention based on the first aspect, and the high dielectric constant alcohol is said to be in a proportion of 0.01% by mass to 5% by mass when the silver paste is 100% by mass. It is a silver paste contained in the silver paste.

The third aspect of the present invention is an invention based on the first or second aspect, and the silver powder contains 55% by volume or more and 95% by volume or less of the first silver particles having a particle size of 100 nm or more and less than 500 nm. The second silver particles having a particle size of 50 nm or more and less than 100 nm are contained in the range of 5% by volume or more and 40% by volume or less, and the third silver particles having a particle size of less than 50 nm are contained in the range of 5% by volume or less. It is a silver paste contained in.

A fourth aspect of the present invention is a step of mixing a silver fatty acid, an aliphatic amine and a solvent having a dielectric constant of less than 30 to obtain a mixture, and heating and stirring the mixture and then cooling it to obtain a mixed solution. A method for producing a silver paste, which comprises a step of kneading the mixed solution, silver powder, and a high dielectric constant alcohol having a dielectric constant of 30 or more to obtain a silver paste.

A fifth aspect of the present invention is a step of directly applying the silver paste of any of the first to third aspects to the surface of a copper or copper alloy member to form a silver paste layer, and on the silver paste layer. In the step of laminating electronic parts on the surface to prepare a laminate, and by heating the laminate, the silver powder in the silver paste layer is sintered to form a bonding layer, and the copper or copper alloy member and the copper alloy member are described. It is a method of manufacturing a bonded body including a step of producing a bonded body in which electronic parts are bonded via the bonding layer.

The silver paste of the first aspect of the present invention contains silver powder, fatty acid silver, an aliphatic amine, a high dielectric constant alcohol having a dielectric constant of 30 or more, and a solvent having a dielectric constant of less than 30. When this silver paste is applied directly to the surface of a copper or copper alloy member, when heated, a high dielectric constant alcohol having a dielectric constant of 30 or more reacts with an oxide film existing on the surface of the copper or copper alloy member, and the reduction thereof occurs. The action removes an oxide film such as CuO from the surface of the copper or copper alloy member. Further, a high dielectric constant alcohol having a dielectric constant of 30 or more easily approaches the silver ion of the complex formed by the reaction of the fatty acid silver contained in the silver paste and the aliphatic amine. When the silver paste layer formed by the silver paste is heated, the high dielectric constant alcohol causes the reduction reaction of the complex to occur more smoothly. When the silver in the complex is reduced, it becomes silver nanoparticles, which improve the sinterability of the silver powder. As a result, even if the copper or copper alloy member does not have the metallized layer, the electronic component can be bonded to the surface of the copper or copper alloy member with high strength. "Applying directly to the surface of a copper or copper alloy member" means applying a silver paste to the surface of a copper or copper alloy member in which a metallized layer such as silver, nickel, or gold is not formed on the surface of the copper or copper alloy member. Means to do.

The silver paste according to the second aspect of the present invention contains a high dielectric constant alcohol in the silver paste in a proportion of 0.01% by mass to 5% by mass. High dielectric constant alcohols within this range have the effect of further producing silver nanoparticles from the silver complex in the silver paste layer when the silver paste layer is heated. On the other hand, the viscosity of the silver paste is not increased more than necessary, the handleability of the silver paste is not deteriorated, and the pot life (usable time) of the silver paste is not shortened.

In the silver paste according to the third aspect of the present invention, the silver powder contains the first silver particles having a particle size of 100 nm or more and less than 500 nm in the range of 55% by volume or more and 95% by volume or less, and the particle size is 50 nm or more and less than 100 nm. Since the second silver particles are contained in the range of 5% by volume or more and 40% by volume or less and the third silver particles having a particle size of less than 50 nm are contained in the range of 5% by volume or less, the silver powder has a relatively wide particle size. By having a distribution, the gaps between the first to third silver particles become small and dense at the time of sintering, so that a bonding layer having few voids can be produced.

In the method for producing a silver paste according to the fourth aspect of the present invention, a high dielectric constant alcohol having a dielectric constant of 30 or more is mixed with the silver powder together with the mixed solution after preparing the mixed solution. Does not worsen and does not shorten the pot life (usable time) of silver paste. In the mixed liquid, at least a part of silver fatty acid reacts with at least part of an aliphatic amine to form a complex. When the silver paste layer in which the silver paste is applied to the copper or copper alloy member is heated, the high dielectric constant alcohol reduces the silver in the complex to produce silver nanoparticles, which are the sintered silver powder. Improve sex.

In the method for producing a bonded body according to the fifth aspect of the present invention, first, a silver paste from any of the first to third aspects is directly applied to the surface of a copper or copper alloy member to form a silver paste layer. .. Next, electronic components are laminated on a copper or copper alloy member via a silver paste layer to prepare a laminate, and the laminate is heated. When the silver paste is heated, the oxide film such as CuO on the surface of the copper or copper alloy member is removed by the reducing action of the high dielectric constant alcohol contained in the silver paste. Further, by this heating, the silver of the complex formed by the reaction of the fatty acid silver and the aliphatic amine in the silver paste is reduced by the high dielectric constant alcohol to become silver nanoparticles. The silver nanoparticles promote the sintering of the silver powder to form a bonding layer, and the electronic component is bonded to the copper or copper alloy member with high strength via the bonding layer.

Next, a mode for carrying out the present invention will be described. The silver paste contains silver powder, fatty acid silver, an aliphatic amine, a high dielectric constant alcohol having a dielectric constant of 30 or more, and a solvent having a dielectric constant of less than 30. Hereinafter, each component will be described in detail.

[Silver powder]
The silver powder of the present embodiment is not particularly limited, and a commercially available silver powder can be used. Preferably, it contains first silver particles (first group of silver particles), second silver particles (second group of silver particles), and third silver particles (third group of silver particles) having different particle sizes. Is preferable. All of these first to third silver particles aggregate with each other as primary particles to form an agglomerate (silver powder). The particle size of the first silver particles is preferably 100 nm or more and less than 500 nm, and when the total amount of the first to third silver particles is 100% by volume, it is contained in the range of 55% by volume or more and 95% by volume or less. Is preferable. The particle size of the second silver particles is preferably 50 nm or more and less than 100 nm, and when the total amount of the first to third silver particles is 100% by volume, it is contained in the range of 5% by volume or more and 40% by volume or less. Is preferable. The particle size of the third silver particles is preferably less than 50 nm, and when the total amount of the first to third silver particles is 100% by volume, it is preferably contained in the range of 5% by volume or less. The "volume" here indicates the volume of the silver particles themselves. The content ratio of the first to third silver particles is limited to the above range because the particle size distribution is relatively wide, so that the gaps between the first to third silver particles are small and dense during sintering. This is because the agglomerates make it easier to form a bonding layer with few voids. The purity of silver in the first to third silver particles is preferably 90% by mass or more, and more preferably 99% by mass or more. This is because the higher the purity of the first to third silver particles, the easier it is to melt, so that the first to third silver particles can be sintered at a relatively low temperature. The elements other than silver in the first to third silver particles may include Au, Cu, Pd and the like.

The first silver particles having a particle size of 100 nm or more and less than 500 nm are preferably contained in the range of 70% by volume or more and 90% by volume or less, and the second silver particles having a particle size of 50 nm or more and less than 100 nm are 10% by volume or more and 30 volumes by volume. The content is preferably in the range of% or less, and the third silver particles having a particle size of less than 50 nm are preferably contained in the range of 1% by volume or less. When the particle size distribution of the first to third silver particles is within the above range, the effect of forming a dense silver powder agglomerate with a small gap between the first to third silver particles is high at the time of sintering. Therefore, it becomes easier to produce a bonding layer having few voids. The particle size of the first to third silver particles was obtained by measuring the projected area of the first to third silver particles in the silver powder using, for example, SEM (Scanning Electron Microscope). It can be obtained by calculating the equivalent circle diameter (the diameter of a circle having the same area as the projected area of the first to third silver particles) from the projected area and converting the calculated particle size into a volume-based particle size. .. An example of a specific measurement method will be described in Examples described later. The silver particles that do not correspond to the first silver particles, the second silver particles, and the third silver particles are preferably limited to 5% by volume or less, with the total amount of the silver powder being 100% by volume.

The silver powder preferably contains an organic substance composed of an organic reducing agent or a decomposition product thereof, and the organic substance is preferably decomposed or volatilized at a temperature of 150 ° C. Examples of organic reducing agents include ascorbic acid, formic acid, tartaric acid and the like. An organic substance composed of an organic reducing agent or a decomposition product thereof is stored in the state of secondary particles in which the first to third silver particles are aggregated (that is, silver powder before making a silver paste), and the first to third silver particles are stored. It suppresses the oxidation of the surface of the third silver particles, and makes it easier to suppress the mutual diffusion of the first to third silver particles, that is, the diffusion bonding during storage. The organic substance is easily decomposed or volatilized when a silver paste containing an aggregate of silver particles is printed on the surface to be bonded of the member to be bonded and heated, and the highly active surface of the first to third silver particles is formed. By exposing the above, there is an effect that the sintering reaction between the first to third silver particles is facilitated. The decomposition product or volatile substance of the organic substance has a reducing ability to reduce the oxide film on the surface to be bonded of the member to be bonded. If the organic matter contained in the silver powder remains in the bonding layer, it may be decomposed with the passage of time to generate voids in the bonding layer. Therefore, the content ratio of the organic substance is preferably 2% by mass or less when the total amount of the first to third silver particles is 100% by mass. However, in order to obtain the effect of the organic substance, the content ratio of the organic substance is preferably 0.05% by mass or more when the total amount of the first to third silver particles is 100% by mass. The content ratio of the organic substance is more preferably 0.1% by mass to 1.5% by mass when the total amount of the first to third silver particles is 100% by mass.

[Fatty acid silver]
Examples of the fatty acid silver of the present embodiment include silver acetate, silver oxalate, silver propionate, silver myristate, silver butyrate and the like.

[Alphatic amine]
Examples of the aliphatic amine of the present embodiment include primary amines, secondary amines, and tertiary amines. The number of carbon atoms of the aliphatic amine is preferably 8 to 12. If the number of carbon atoms is too small, the boiling point of the aliphatic amine tends to be low, which may reduce the printability of the silver paste. If the number of carbon atoms is too large, the sintering of silver particles in the silver paste may be hindered, and a bonded body having sufficient strength may not be obtained. Specific examples include ethylhexylamine, aminodecane, dodecylamine, nonylamine, hexylamine, octylamine and the like as primary amines, and dimethylamine, diethylamine, dioctylamine and the like as secondary amines. Tertiary amines include trimethylamine, triethylamine and the like.

In the silver paste, the molar ratio of the aliphatic amine to the fatty acid silver, that is, the molar amount of the aliphatic amine / the molar amount of the fatty acid silver is preferably in the range of 1.5 to 3. When the proportion of aliphatic amines is small, the proportion of solid fatty acid silver tends to be relatively high, so that it is difficult to disperse uniformly in the silver paste, and voids are likely to occur inside the bonding layer obtained by heating. There is a risk of becoming. If the proportion of the aliphatic amine is too large, the excessive amount of the aliphatic amine tends to cause the grain growth of the silver powder in the silver paste, and the paste viscosity tends to decrease, which may deteriorate the printability. The molar amount of the aliphatic amine / the molar amount of the silver fatty acid is more preferably in the range of 1.7 to 2.8, and even more preferably in the range of 2.0 to 2.5.

Since the silver paste contains silver fatty acid and an aliphatic amine, at least a part of the silver fatty acid and at least a part of the aliphatic amine react to form a complex. This complex is presumed to be a silver amine complex.

(High dielectric constant alcohol with a dielectric constant of 30 or more)
Examples of high dielectric constant alcohols having a dielectric constant of 30 or more (hereinafter, simply referred to as high dielectric constant alcohols) include diethylene glycol (dielectric constant: 34), propylene glycol (dielectric constant: 32), and 1,3-propanediol (dielectric constant). : 36), 1,2,4-butanetriol (dielectric constant: 38), polyethylene glycol (dielectric constant: 30 or more), glycerin (dielectric constant: 44) and the like. These high dielectric constant alcohols may be used alone or in admixture of two or more. The above-mentioned dielectric constant is a value measured at 22 ° C. using a liquid dielectric constant meter (a liquid dielectric constant meter Model-871 manufactured by Nippon Luft Co., Ltd.). The dielectric constant of high dielectric constant alcohol is, for example, 82 or less. The dielectric constant of the high dielectric constant alcohol may be 34 or more and 44 or less.

〔solvent〕
The solvent of this embodiment is a solvent having a dielectric constant of less than 30. As the solvent, for example, a monohydric alcohol, a dihydric alcohol, an acetate solvent, a hydrocarbon solvent and the like are used. These may be used alone or in combination of two or more.
Examples of the monohydric alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol and the like, as well as aliphatic saturated 1 Valuable alcohols, aliphatic unsaturated alcohols, alicyclic alcohols and aromatic alcohols can be mentioned.
The aliphatic saturated monohydric alcohol includes linear and branched alcohols such as natural alcohols and synthetic alcohols (eg, Cheegler alcohols or oxo alcohols), specifically 2-ethylbutanol, 2-methylpentanol, 4 -Methylpentanol, 1-hexanol, 2-ethylpentanol, 2-methylhexanol, 1-heptanol, 2-heptanol, 3-heptanol, 2-ethylhexanol, 1-octanol, 2-octanol, 1-nonanol, Examples thereof include decanol, undecanol, dodecanol and tridecanol.
Aliper unsaturated alcohols include, for example, alkenol and alkadienol, specifically 2-propylallyl alcohol, 2-methyl-4-pentenol, 1-hexenol, 2-ethyl-4-pentenol, Examples thereof include 2-methyl-5-hexenol, 1-heptenol, 2-ethyl-5-hexenol, 1-octenol, 1-nonenor, undecenol, dodecenol and geraniol.
The alicyclic alcohol includes, for example, cycloalkanol and cycloalkenol, and specific examples thereof include methylcyclohexanol and α-terpineol.
Examples of aromatic alcohols include phenethyl alcohol and salicyl alcohol.
Examples of the dihydric alcohol include triethylene glycol and 2-ethyl-1,3-hexanediol.
Examples of the acetate solvent include butyl carbitol acetate and the like, and examples of the hydrocarbon solvent include decane, dodecane, tetradecane, and a mixture thereof.

〔resin〕
The silver paste may further contain a resin. Examples of the resin include epoxy-based resins, silicone-based resins, acrylic-based resins, and mixtures thereof. Epoxy-based resins include bisphenol A-type epoxy resins, novolac-type epoxy resins, cyclic aliphatic epoxy resins, and mixtures thereof. Silicone-based resins include methyl silicone resins, epoxy-modified silicone resins, and polyester-modified silicones. There are resins and mixtures thereof, and acrylic resins include acrylate-based monomer resins and the like. These resins are cured by heating the silver paste, and the cured product is filled in the voids of the sintered body of the silver powder. By filling the voids of the sintered body of silver powder with the cured product of the thermosetting resin composition, the mechanical strength of the bonding layer is improved, and the decrease in bonding strength under a cold cycle load is suppressed. The content of the resin is preferably in the range of 0.1% by mass to 3% by mass when the total amount of the silver paste is 100% by mass. If the content of the resin is less than 0.1% by mass, the mechanical strength of the bonding layer may not be improved, and if it exceeds 3% by mass, sintering of silver powder is hindered and the mechanical strength of the bonding layer is lowered. There is a risk of A more preferable content of the resin is in the range of 0.2% by mass to 2.5% by mass, and a further preferable content is in the range of 0.3% by mass to 2.0% by mass.

[Manufacturing method of silver paste]
A method for producing the silver paste thus constructed will be described. First, a fatty acid silver, an aliphatic amine and a solvent having a dielectric constant of less than 30 are prepared, and a mixture of fatty acid silver, an aliphatic amine and a solvent having a dielectric constant of less than 30 is prepared. When the total amount of this mixture is 100% by mass, 80% by mass of the solvent having a fatty acid silver of 0.1% by mass to 40% by mass, an aliphatic amine of 0.1% by mass to 60% by mass, and a dielectric constant of less than 30 It is preferable to mix in a proportion of mass% or less. The mixing ratio of the fatty acid silver, the aliphatic amine and the solvent having a dielectric constant of less than 30 is limited to the above range because precipitation and the like are unlikely to occur in the mixed solution. A more preferable mixing ratio is 20% by mass to 30% by mass of silver fatty acid and 20% by mass of aliphatic amine when the total amount of silver fatty acid, aliphatic amine and solvent having a dielectric constant of less than 30 is 100% by mass. 40% by mass to 40% by mass and 40% by mass to 60% by mass of a solvent having a dielectric constant of less than 30.

Next, it is preferable to heat the mixture to 30 ° C. to 100 ° C. and stir for 5 minutes to 10 hours to prepare a mixture. After preparation, the mixture is cooled to room temperature (25 ° C.). As a result, a mixed solution of fatty acid silver, an aliphatic amine and a solvent having a dielectric constant of less than 30 (hereinafter, simply referred to as a mixed solution) is prepared. The heating temperature and heating time of the mixture are within the above ranges in order to facilitate uniform mixing of the fatty acid silver, the aliphatic amine, and the solvent having a dielectric constant of less than 30. The heating temperature of the mixture is preferably 40 ° C. or higher and 80 ° C. or lower. The heating time of the mixture is preferably 10 minutes or more and 5 hours or less.

Next, the mixed solution, the silver powder, and the high dielectric constant alcohol are mixed, stirred with a planetary planetary stirrer or the like, and further kneaded with a three-roll mill or the like to obtain a silver paste. When the silver paste is 100% by mass, the content of the silver powder is preferably in the range of 50% by mass to 95% by mass, and the content of the high dielectric constant alcohol is 0.01% by mass to 5%. It is preferably in the range of mass%. The rest is the mixed solution. It is more preferable that the content of the silver powder is in the range of 80% by mass to 90% by mass and the content of the high dielectric constant alcohol is in the range of 0.05% by mass to 3% by mass. In the silver paste, if the content of the silver powder is small, the viscosity of the silver paste may decrease and coating defects such as sagging may easily occur, and if it is too high, the viscosity may increase and the handleability may deteriorate. .. Mixing high dielectric constant alcohols with silver powder and mixed solutions is because mixing high dielectric constant alcohols with fatty acid silver, aliphatic amines and other solvents increases the viscosity of the mixture and mixes the silver powder. This is because it becomes difficult, the handleability of the prepared silver paste of the silver paste is deteriorated, and the pot life (usable time) is shortened. By mixing the high dielectric constant alcohol, when the silver paste layer is heated as described above, the effect of producing silver nanoparticles from the silver complex in the silver paste layer is obtained. For the above reasons, the content of the high dielectric constant alcohol is preferably in the above range. The silver paste may contain the resin. In this case, the cold cycle characteristics are improved. The resin may be added when mixing the mixed solution, the silver powder and the high dielectric constant alcohol. After mixing the mixed solution and the high dielectric constant alcohol, silver powder may be added and mixed to obtain a silver paste.

In this mixed solution, the molar ratio of the aliphatic amine to the silver fatty acid, that is, the molar amount of the aliphatic amine / the molar amount of the silver fatty acid is preferably in the range of 1.5 to 3, 1.7 to 2. It is more preferably within the range of 8.8. When a silver paste is prepared using such a mixed solution, the molar ratio of the aliphatic amine to the fatty acid silver in the mixed solution becomes the molar ratio of the aliphatic amine to the fatty acid silver in the silver paste.

[Manufacturing method of bonded body]
A method for producing a bonded body using the silver paste will be described.
In the manufacturing method of this embodiment, a copper or copper alloy member and an electronic component are prepared. No metallized layer is formed on the surface of this copper or copper alloy member. Examples of electronic components include semiconductor chips, high-power LED elements, semiconductor elements such as power semiconductor elements, semiconductor packages, and the like. Examples of the copper or copper alloy member include a DBC substrate (copper-clad substrate) and a lead frame made of a copper alloy. However, the copper or copper alloy member is not limited to the DBC substrate and the lead frame. Next, the silver paste is directly applied to the surface of the copper or copper alloy member by, for example, a metal mask method or the like to form a silver paste layer having a desired planar shape. When the silver paste is heated, the oxide film such as CuO on the surface of the copper or copper alloy member is removed by the reducing action of the high dielectric constant alcohol contained in the silver paste. Next, electronic components are laminated on a copper or copper alloy member via a silver paste layer to prepare a laminated body. Then, this laminate is heated. For example, the laminate is heated and held at a temperature of 120 ° C. to 280 ° C. (heating temperature) for 10 minutes to 240 minutes (heating time). The atmosphere at this time is preferably a nitrogen atmosphere having an oxygen concentration of 500 ppm (volume basis) or less, and more preferably a nitrogen atmosphere having an oxygen concentration of 100 ppm (volume basis) or less. This is because the surface of the copper or copper alloy member is not oxidized. Upon heating, the complex silver formed by the reaction of fatty acid silver and aliphatic amines is reduced by high dielectric constant alcohol to form silver nanoparticles. The silver powder (first silver particles, second silver particles, and third silver particles) in the silver paste layer is sintered together with the silver nanoparticles to form a bonding layer, and the electronic component is formed on the copper or copper alloy member. A bonded body directly bonded via a bonding layer is produced. The reason why the heating temperature and heating time of the laminate are limited to the above ranges is that if less than 10 minutes, sintering may be difficult to proceed, and even if it exceeds 240 minutes, the bonding characteristics do not change and the cost increases. Based on the reason. At the time of heating, it is not necessary to pressurize the laminated body in the laminating direction. It is based on the reason that the pressurization process is omitted to reduce the cost.

Next, examples of the present invention will be described in detail together with comparative examples. First, mixed solutions 1 to 15 and mixed solutions 20 to 22, which are silver paste precursors containing no silver powder, will be described, and then Examples 1 to 21 and Comparative Examples 1 to 10 using these mixed solutions will be described. do.

[Production example of silver paste precursor (mixed solution)]
<Mixed solution 1>
First, silver acetate (fatty acid silver), aminodecane (aliphatic amine) and butyl carbitol acetate (solvent) are prepared, and when the total amount of fatty acid silver, aliphatic amine and solvent is 100% by mass, silver acetate (fatty acid) Weighed 22% by mass of silver), 41.3% by mass of aminodecane (aliphatic amine), and 36.7% by mass of butyl carbitol acetate (solvent), and placed them in a glass container together with a stirrer of Stirrer. .. Then, the container was placed on a hot plate heated to 50 ° C., and the mixture was prepared by stirring for 1 hour while rotating the stirrer of the stirrer at 300 rpm. Then, the container in which the mixed solution was stored was removed from the hot plate to lower the temperature of the mixed solution to room temperature. As a result, a mixed solution 1 which is a fatty acid silver / aliphatic amine mixed solution (hereinafter, simply referred to as a mixed solution) which is a silver paste precursor was prepared.

<Mixed solution 2 to 15 and mixed solution 20 to 22>
As the mixed solutions 2 to 15 and the mixed solutions 20 to 22, the types shown in Table 1 are used as the fatty acid silver, the aliphatic amine and the solvent, and the fatty acid silver, the aliphatic amine and the solvent are as shown in Table 1. Each was mixed in proportion. Although the mixed solution 20 is not a mixed solution because it does not contain silver fatty acid and the mixed solution 21 does not contain an aliphatic amine, the mixed solutions 20 and 21 are also referred to as mixed solutions in the present specification for convenience. In the column of the type of fatty acid silver in Tables 1 and 2, "A1" is silver acetate, "A2" is silver oxalate, and "A3" is silver myristate. In the column of aliphatic amine types in Tables 1 and 2, "B1" indicates aminodecane, "B2" indicates hexylamine, "B3" is octylamine, and "B4" is dodecylamine. , "B5" is a dioctylamine. In the column of solvent types in Tables 1 and 2, "C1" is butyl carbitol acetate (dielectric constant: 7), "C2" is terpineol (dielectric constant: 4), and "C3" is 2. -Ethyl 1,3-hexanediol (dielectric constant: 19), "C4" is 1-octanol (dielectric constant: 11), and "C5" is 1,2,4-butanetriol (dielectric constant: 38). ).

<Comparative test 1 and evaluation>
After heating the mixed solutions 1 to 15 and the mixed solutions 20 to 22 separately at 130 ° C. for 10 minutes, 1 g of each mixed solution is dropped onto a silicon wafer and dried under reduced pressure at a temperature of 25 ° C. , A wafer in which a dried product adhered to the surface was produced. Then, the surface of this wafer was observed by SEM (scanning electron microscope), 1000 particles adhering to the surface were counted, and extracted using image processing software (Image-J (National Institute of Public Health: Development)). The projected area of the particles (primary particles) was measured, and the equivalent circle diameter was calculated from the obtained projected area, which was used as the primary particle diameter. The equivalent circle diameter was not measured for particles with invisible contours. The obtained primary particle size was converted into a volume-based particle size, and the average value of the volume-based particle size was taken as the average particle size of the dried product. The product in which silver powder was produced from the dried product was determined to be "possible", and the product in which silver powder was not produced from the dried product or the silver powder could not be measured was determined to be "impossible". Table 2 shows the average particle size of the dried product and the determination results. Table 2 also shows the types of silver fatty acids, the types of aliphatic amines, and the types of solvents.

As is clear from Table 2, since the mixed solution 20 does not contain the fatty acid silver, that is, it does not contain silver which is expected to contribute to the densification of the bonding layer, silver powder is generated during SEM (scanning electron microscope) observation. Was not seen, and the judgment result was impossible.

Since the mixed solution 21 does not contain an aliphatic amine, a uniform mixed solution cannot be obtained, and the dried product on the silicon wafer becomes a lump. Therefore, the silver powder can be measured by SEM (scanning electron microscope) observation. The judgment result was not possible. It is considered that this is because the mixed solution 21 does not contain an aliphatic amine, so that the decomposition of the fatty acid silver did not proceed sufficiently and the silver powder was not produced.

Since 1,2,4-butanetriol (dielectric constant: 38) having a dielectric constant of 30 or more was used as the solvent for the mixed solution 22, silver powder was excessively precipitated at the time of heating and stirring the mixed solution 22, and the pressure was further reduced. Since it became a huge agglomerate by drying, the particle size of the silver powder could not be measured during SEM (scanning electron microscope) observation, and the determination result was impossible.

On the other hand, since the mixed solution of the mixed solutions 1 to 15 contains fatty acid silver, an aliphatic amine, and a solvent having a dielectric constant of less than 30, silver powder having an average particle size of 50 nm to 100 nm when observed by SEM (scanning electron microscope). Was observed, and the judgment result was acceptable. It is presumed that this is because the mixed solutions 1 to 15 contain silver fatty acid and an aliphatic amine, so that the organic matter is rapidly decomposed by heating and silver nanoparticles having a highly active surface exposed are easily formed. NS.

[Production example of silver paste]
First, a method for preparing silver powder used as a raw material for the silver paste prepared in Examples 1 to 21 and Comparative Examples 1 to 10 will be described. These 10 types of silver powder are shown in "No. 1 to No. 10" in Table 3 below. Table 3 also shows the organic matter content in the 10 types of silver powder.

The No. 1 silver powder (mixture / aggregate of first to third silver particles) shown in Table 3 was prepared as follows. First, silver fine particles (raw material powder A) in which D10, D50 and D90 are 20 nm, 50 nm and 100 nm, respectively, and silver fine particles (raw material powder B) in which D10, D50 and D90 are 150 nm, 300 nm and 500 nm, respectively, were prepared. .. The method for preparing the silver fine particles (raw material powder A) and the silver fine particles (raw material powder B) will be described later. D10, D50 and D90 of each silver fine particle were obtained from the particle size distribution curve of the silver fine particle. The particle size distribution curve of the silver fine particles was measured by the dynamic light scattering method described later. For the No. 1 silver powder, the raw material powder A and the raw material powder B were mixed at a mass ratio of 1: 3 to obtain a silver fine particle mixture.

Next, this silver fine particle mixture, sodium ascorbate (organic reducing agent), and water were mixed at a mass ratio of 10: 1: 89 to prepare a silver fine particle slurry. The silver fine particle slurry was heated at a temperature of 90 ° C. for 3 hours to reduce the silver fine particles. Next, the silver fine particle slurry was allowed to cool to room temperature, and then the solid matter was separated and recovered using a centrifuge. The recovered solid (mercury-containing fine particle agglomerates) was washed with water several times and dried to obtain No. 1 silver powder (mixture / agglomerates of first to third silver particles) shown in Table 3.

The No. 2 silver powder is the same as the No. 1 silver powder described above, except that the mixing ratio of the silver fine particles (raw material powder A) and the silver fine particles (raw material powder B) is 1: 1 by mass ratio. Obtained in the same manner as the preparation method.

The No. 3 silver powder is the same as the No. 1 silver powder described above, except that the mixing ratio of the silver fine particles (raw material powder A) and the silver fine particles (raw material powder B) is 1: 5 by mass ratio. Obtained in the same manner as the preparation method.

No. 4 silver powder was obtained by the following method. A 900 g silver nitrate aqueous solution kept at 50 ° C. and a 600 g sodium citrate aqueous solution kept at 50 ° C. were simultaneously added dropwise to 1200 g of ion-exchanged water held at 50 ° C. over 5 minutes to prepare a silver citrate slurry. Prepared. The ion-exchanged water was continuously stirred while the silver nitrate aqueous solution and the sodium citrate aqueous solution were simultaneously added dropwise to the ion-exchanged water. The concentration of silver nitrate in the silver nitrate aqueous solution was 66% by mass, and the concentration of citric acid in the sodium citrate aqueous solution was 56% by mass. Then, 300 g of an aqueous sodium formate solution kept at 50 ° C. was added dropwise to the silver citrate slurry held at 50 ° C. over 30 minutes to obtain a mixed slurry. The concentration of formic acid in this sodium formate aqueous solution was 58% by mass. Next, the mixed slurry was subjected to a predetermined heat treatment. Specifically, the mixed slurry was raised to a maximum temperature of 60 ° C. at a heating rate of 10 ° C./hour, held at 60 ° C. (maximum temperature) for 30 minutes, and then lowered to 20 ° C. over 60 minutes. .. As a result, a silver powder slurry was obtained. The silver powder slurry was placed in a centrifuge and rotated at a rotation speed of 1000 rpm for 10 minutes. As a result, the liquid layer in the silver powder slurry was removed to obtain a dehydrated and desalted silver powder slurry. The dehydrated and desalted silver powder slurry was dried by a freeze-drying method for 30 hours to obtain No. 4 silver powder having a volume-based particle size distribution shown in Table 3.

The No. 5 silver powder is the same as the No. 1 silver powder described above, except that the mixing ratio of the silver fine particles (raw material powder A) and the silver fine particles (raw material powder B) is 2: 1 by mass ratio. Obtained in the same manner as the preparation method.

The No. 6 silver powder is the same as the No. 1 silver powder described above, except that the mixing ratio of the silver fine particles (raw material powder A) and the silver fine particles (raw material powder B) is 1: 6 by mass ratio. Obtained in the same manner as the preparation method.

The No. 7 silver powder is the same as the No. 1 silver powder described above, except that the mixing ratio of the silver fine particles (raw material powder A) and the silver fine particles (raw material powder B) is 2: 9 by mass ratio. Obtained in the same manner as the preparation method.

The silver powder of No. 8 was No. 1 described above except that only the silver fine particles (raw material powder A) were used without mixing the silver fine particles (raw material powder A) and the silver fine particles (raw material powder B). It was obtained in the same manner as in the preparation method of the silver powder of.

The No. 9 silver powder is the same as the No. 1 silver powder described above, except that the mixing ratio of the silver fine particles (raw material powder A) and the silver fine particles (raw material powder B) is 4: 3 in mass ratio. Obtained in the same manner as the preparation method.

The No. 10 silver powder is the same as the No. 1 silver powder described above, except that the mixing ratio of the silver fine particles (raw material powder A) and the silver fine particles (raw material powder B) is 1: 9 by mass ratio. Obtained in the same manner as the preparation method.

The silver powder (raw material powder A) is suspended by mixing silver nitrate, citric acid, and potassium hydroxide in distilled water so as to have an equimolar ratio (1: 1: 1) with respect to silver ions in silver nitrate. A liquid was prepared. Hydrazine acetate is added to this suspension in a molar ratio of 2 to 1 silver ion. The suspension to which hydrazine acetate was added was reacted at a liquid temperature of 40 ° C., and was washed, recovered and dried from the obtained reaction liquid slurry.

For the silver fine particles (raw material powder B), a silver nitrate aqueous solution, ammonia water, and distilled water were mixed to prepare a silver ammine aqueous solution having a silver concentration of 22 g / L, and a reducing solution was added to the silver ammine aqueous solution to generate silver. It was obtained by washing, recovering, and drying the particle slurry. The reducing solution is a mixed solution of an aqueous solution of hydroquinone and an aqueous solution of sodium hydroxide, and is a solution prepared so that the redox potential is -380 mV based on Ag / AgCl.

<Measurement method of particle size distribution of silver particles>
Using SEM, 500 images of aggregates (secondary particles) in which the first to third silver particles are aggregated are acquired, and the particle size of the silver particles (primary particles) contained in each silver particle aggregate is determined. It was measured. At this time, the device magnification of the SEM was set to 100,000 times. From the SEM image of 500 silver particle aggregates, silver particles in which the entire outline of the silver particles (primary particles) can be visually recognized were extracted. Next, the projected area of the extracted silver particles was measured using image processing software (Image-J), and the equivalent circle diameter was calculated from the obtained projected area, which was used as the particle size of the silver particles. The diameter equivalent to the circle was not measured for silver particles whose contours could not be visually recognized. The particle size of the obtained silver particles was converted into a volume-based particle size, and the particle size distribution of the volume-based particle size was obtained. The results are shown in Table 3.

<Measuring method of organic matter content>
The content of organic matter in the silver powders No. 1 to No. 10 was calculated by the following method. The silver powder before mixing with the mixed solution was weighed and heated in the air at a temperature of 150 ° C. for 30 minutes. After heating, the mixture was allowed to cool to room temperature, and the mass of the silver powder was measured. The content of organic matter was calculated from the following formula (1). As a result, the content of organic matter in the No. 1 silver powder was 0.2% by mass.
Organic matter content (mass%) = {(AB) / A} × 100 …… (1)
However, A in the formula (1) is the mass of the silver powder before heating, and B is the mass of the silver powder after heating. The results obtained are shown in Table 3.

Next, Examples 1 to 26 and Comparative Examples 1 to 10 for preparing a silver paste will be described.

<Example 1>
In order to make the silver paste 100% by mass, the mixed solution 1 (24.00% by mass), the No. 1 silver powder (75.00% by mass), and 1,2,4-butanetriol as a high dielectric constant alcohol After mixing with (D1) (1.00% by mass), the mixture was stirred with a planetary planetary stirrer and further kneaded with a three-roll mill. This gave a silver paste. This silver paste was designated as Example 1.

<Examples 2 to 21 and Comparative Examples 1 to 10>
The 31 types of silver pastes of Examples 2 to 21 and Comparative Examples 1 to 10 are prepared by preparing their mixed solutions using the fatty acid silver, aliphatic amines and solvents shown in Tables 1 and 2, and silver. The powder, the mixed solution and the high dielectric constant alcohol were blended in the ratios shown in Tables 4 and 5, respectively. A silver paste was prepared in the same manner as in Example 1 except for the blending of the silver powder, the mixed solution and the high dielectric constant alcohol shown in Tables 4 and 5. However, Comparative Examples 2 and 4 did not become a paste for the reason described later. In Examples 5, 6, 11, 12, 18 and 19, two kinds of high dielectric constant alcohols were used.
The mixed solution used in Examples 1 to 21 and Comparative Examples 1 to 10 is either "mixed solution 1 to 15" or "mixed solution 20 to 22" in the column of the type of mixed solution in Tables 4 and 5. Shown in. In Examples 1 to 21 and Comparative Examples 1 to 10, any one of 10 types (No. 1 to No. 10) of silver powder having different particle size distributions shown in Table 3 is blended. The silver powder used in Examples 1 to 21 and Comparative Examples 1 to 10 is shown by any of "No. 1 to No. 10" in the column of the type of silver powder in Tables 4 and 5. In the column of types of high dielectric constant alcohols in Tables 4 and 5, "D1" is 1,2,4-butanetriol (dielectric constant: 38) and "D2" is 1,3-propanediol (dielectric). Rate: 36), "D3" is glycerin (dielectric constant: 44), "D4" is diethylene glycol (dielectric constant: 34), and "D5" is 2-methoxyethanol (dielectric constant: 18). be.

<Comparative test 2 and evaluation>
(1) Bonds were prepared using the silver pastes of Examples 1 to 21 and Comparative Examples 1, 3, 5 to 10, respectively. Specifically, first, a 10 mm square Si wafer (thickness: 200 μm) having a gold-plated surface imitating an electronic component was prepared. A 20 mm square oxygen-free copper plate (thickness: 1 mm) was prepared as a copper or copper alloy member. No metallized layer is formed on the surface of this copper plate. Next, the silver paste was applied to the surface of the oxygen-free copper plate by the metal mask method to form a silver paste layer. Next, a Si wafer was placed on the silver paste layer to prepare a laminate. This laminate was heated by holding it at a temperature of 250 ° C. for 60 minutes in a nitrogen atmosphere having an oxygen concentration of 100 ppm (volume basis), and a Si wafer was bonded to an oxygen-free copper plate via a bonding layer. These joints were used as the joints of Examples 1 to 21 and Comparative Examples 1, 3, 5 and 10. The laminated body was not pressurized in the laminated direction. The joint strength of these joints was measured as follows.

(Measurement method of joint strength of joint body)
The joint strength of 29 types of joints of Examples 1 to 21 and Comparative Examples 1, 3, 5 to 10 was measured using a shear strength evaluation tester. Specifically, the joint strength is measured by fixing the oxygen-free copper plate of the joint horizontally and using a share tool at a position 50 μm above the surface (upper surface) of the joint layer to horizontally move the Si wafer of the joint from the side. This was done by measuring the strength of the Si wafer when it was broken. The moving speed of the share tool was 0.1 mm / sec. The strength test was performed three times under one condition, and the arithmetic mean value thereof was used as the measured value of the joint strength.

(2) A silver fired film was prepared using 29 kinds of silver pastes of Examples 1 to 21 and Comparative Examples 1, 3, 5 to 10, respectively. Specifically, first, 29 kinds of silver pastes were each applied on a transparent glass plate with a metal mask plate (hole size: length 10 mm × width 10 mm, thickness: 50 μm) to form silver paste layers. Next, the silver paste layer formed on the transparent glass substrate was held at a temperature of 250 ° C. (heating temperature) for 60 minutes (heating time) in a nitrogen atmosphere having an oxygen concentration of 100 ppm (volume basis) to form a silver fired film. Made. These silver fired films were used as the silver fired films of Examples 1 to 21 and Comparative Examples 1, 3, 5 to 10. The thermal diffusivity of these fired silver films was measured as follows.

(Measurement method of thermal diffusivity of silver fired film)
The thermal diffusivity of 29 types of silver fired films of Examples 1 to 21 and Comparative Examples 1, 3, 5 to 10 was measured by a laser flash method. Specifically, first, the temperature change T (t) on the back surface of the silver fired film when the surface of the silver fired film was uniformly irradiated with a pulse laser and instantaneously heated was measured. Next, since the temperature change T (t) on the back surface of the silver fired film is expressed by a one-dimensional heat conduction equation, the temperature change T (t) on the back surface of the silver fired film is taken on the vertical axis and the elapsed time t is horizontal. By taking the axis, a (T (t) -t) curve was obtained, _{and the time t 0.5} required to reach half the _{maximum temperature rise temperature T MAX was} calculated from this curve. Then, the thermal diffusivity α of the silver fired film was obtained by the following equation (2).
α = 1.370 x L ² / (π ² x t _0.5 ) …… (2)
L in the formula (2) is the thickness of the silver fired film. The results of the thermal diffusivity of these silver fired films are shown in Tables 4 and 5.

As is clear from Table 5, in Comparative Example 1, the conjugate and silver were used using a silver paste containing 20 (15.00% by mass) of a mixed solution to which no fatty acid silver was added, while containing no high dielectric constant alcohol. Since the calcined film was prepared, in addition to not containing the high dielectric constant alcohol, the mixed solution 20 did not contain the fatty acid silver, so that the bonding strength of the bonded body was as small as 10 MPa, and the thermal diffusivity of the silver calcined film was 39 W. It was as small as / mK.

In Comparative Example 2, an attempt was made to prepare a bonded body and a silver-fired film using a silver paste containing a mixed solution 21 (15.00% by mass) to which an aliphatic amine was not added, but not containing a high dielectric constant alcohol. However, because the mixed solution did not contain an aliphatic amine, it did not become a silver paste, so that a conjugate and a silver-fired film could not be prepared.

In Comparative Example 3, the conjugate and silver were used with a mixed solution 20 (14.00% by mass) to which no fatty acid silver was added and a silver paste containing 1,2,4-butantriol (1.00% by mass). Since the calcined film was prepared, since the mixed solution 20 does not contain silver fatty acid, even if 1,2,4-butanetriol (D1) (high dielectric constant alcohol) having a dielectric constant of 38 is used, the bonded body is bonded. The strength was as small as 9 MPa, and the thermal diffusivity of the silver-fired film was as small as 38 W / mK.

In Comparative Example 4, a mixed solution 21 (14.00% by mass) to which no aliphatic amine was added and 1,2,4-butanetriol (D1) (1.00% by mass) as a high dielectric constant alcohol were contained. An attempt was made to prepare a bonded body and a silver-fired film using a silver paste, but the mixed solution 21 did not become a silver paste due to the fact that the mixed solution 21 did not contain an aliphatic amine, so that the bonded body and the silver-fired film could be prepared. There wasn't.

In Comparative Example 5, a bonded body and a silver-fired film were prepared using a silver paste containing a mixed solution 1 (15.00% by mass) containing silver fatty acid and an aliphatic amine, while not containing a high dielectric constant alcohol. Therefore, since it does not contain high dielectric constant alcohol, the bonding strength of the bonded body was as small as 10 MPa, and the thermal diffusion rate of the silver fired film was as small as 58 W / mK.

In Comparative Example 6, the mixed solution 1 (15.00% by mass) to which the fatty acid silver and the aliphatic amine were added and the No. 8 silver powder (85.00% by mass) were contained, but the high dielectric constant alcohol was not contained. Since the bonded body and the silver-fired film were prepared using the silver paste, the bonding strength of the bonded body was as small as 5 MPa and the thermal diffusivity of the silver-fired film was as small as 40 W / mK because the dielectric alcohol was not contained.

In Comparative Example 7, the mixed solution 1 (15.00% by mass) to which the fatty acid silver and the aliphatic amine were added and the silver powder of No. 9 (85.00% by mass) were contained, but the high dielectric constant alcohol was not contained. Since the bonded body and the silver-fired film were prepared using the silver paste, the bonding strength of the bonded body was as small as 5 MPa and the thermal diffusivity of the silver-fired film was as small as 45 W / mK because the dielectric alcohol was not contained.

In Comparative Example 8, the mixed solution 1 (15.00% by mass) to which the fatty acid silver and the aliphatic amine were added and the No. 10 silver powder (85.00% by mass) were contained, but the high dielectric constant alcohol was not contained. Since the bonded body and the silver-fired film were prepared using the silver paste, the bonding strength of the bonded body was as small as 6 MPa and the thermal diffusivity of the silver-fired film was as small as 70 W / mK because the dielectric alcohol was not contained.

In Comparative Example 9, a bonded body and a silver-fired film were prepared using a silver paste containing 1 (15.00% by mass) of a mixed solution containing silver fatty acid and an aliphatic amine, while not containing a high dielectric constant alcohol. Since it does not contain dielectric alcohol, the bonding strength of the bonded body was as small as 25 MPa, and the thermal diffusivity of the silver-fired film was as small as 75 W / mK.

In Comparative Example 10, a silver paste containing 2-methoxyethanol (D5) (3.00% by mass) and a mixed solution 1 (12.00% by mass) to which silver fatty acid and an aliphatic amine were added were used to prepare the conjugate and the mixture. Since a silver-fired film was prepared, 2-methoxyethanol had a low dielectric constant of 18, so the bonding strength of the bonded body was as small as 27 MPa, and the thermal diffusivity of the silver-fired film was as small as 77 W / mK.

In contrast to Comparative Examples 1, 3, 5 and 10, in Examples 1 to 21, mixed solutions 1 to 15 containing silver fatty acid, an aliphatic amine and a solvent (however, the dielectric constant is less than 30). And a high dielectric constant alcohol having a dielectric constant of 30 or more were kneaded and prepared, and a bonded body and a silver fired film were prepared using a silver paste. Therefore, in Examples 1 to 21, the bonding strength of the bonded body was as large as 35 MPa to 54 MPa, and the thermal diffusivity of the silver fired film was as large as 100 W / mK to 158 W / mK.

The silver paste of the present invention joins semiconductor elements such as high-power LED elements and power semiconductor elements, and electronic components such as semiconductor packages to copper or copper alloy members which are substrates such as DBC substrates (copper-clad substrates) and lead frames. It can be used as a bonding layer or the like.

Claims (5)

A silver paste containing silver powder, fatty acid silver, an aliphatic amine, a high dielectric constant alcohol having a dielectric constant of 30 or more, and a solvent having a dielectric constant of less than 30. The silver paste according to claim 1, wherein the high dielectric constant alcohol is contained in the silver paste at a ratio of 0.01% by mass to 5% by mass when the silver paste is 100% by mass. The silver powder contains first silver particles having a particle size of 100 nm or more and less than 500 nm in a range of 55% by volume or more and 95% by volume or less, and 5% by volume or more of second silver particles having a particle size of 50 nm or more and less than 100 nm. The silver paste according to claim 1 or 2, which contains a third silver particle having a particle size of less than 50 nm in a range of 40% by volume or less and a particle size of less than 50 nm in a range of 5% by volume or less. A step of mixing fatty acid silver, an aliphatic amine, and a solvent having a dielectric constant of less than 30 to obtain a mixture, and
A step of heating the mixture, stirring it, and then cooling it to obtain a mixed solution.
A method for producing a silver paste, which comprises a step of kneading the mixed solution, silver powder, and a high dielectric constant alcohol having a dielectric constant of 30 or more to obtain a silver paste. A step of directly applying the silver paste according to any one of claims 1 to 3 to the surface of a copper or copper alloy member to form a silver paste layer.
A step of laminating electronic components on the silver paste layer to prepare a laminate, and
By heating the laminate, the silver powder in the silver paste layer is sintered to form a bonding layer, and the copper or copper alloy member and the electronic component are bonded via the bonding layer. A method for manufacturing a bonded body, which includes a step of manufacturing.