Method for producing laminate, method for producing electronic component including the same, silver paste, and coated silver powder

Abstract

To provide a technique that allows suppression of diffusion of silver ions from silver powder into a substrate during a process for forming a silver film through heat treatment of silver powder containing a predetermined amount of phosphorus.SOLUTION: According to the technology disclosed herein, there is provided a method for producing a laminate comprising a substrate and a silver film on the substrate. The production method includes: applying, onto the substrate, silver powder containing 50 ppm or more and 500 ppm or less of phosphorus as an impurity, and an additive A which is a barium compound; and performing heat treatment on the substrate, and the silver powder and the additive A applied onto the substrate, to form a silver film on the substrate.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a laminate, a method for producing an electronic component including the method, a silver paste, and a coated silver powder. [Background technology]

[0002] Japanese Patent Application Laid-Open Publication No. 2005-268164 discloses a conductive coating composition for forming internal electrodes of ferrite multilayer chip inductors. This conductive coating composition is characterized by the addition of at least one salt or amide of a higher fatty acid. The publication also states that electrodes formed on a ferrite layer using this conductive coating composition have adequate adhesion to the ferrite layer before firing and are almost completely peeled off from the ferrite layer without difficulty upon firing. This not only virtually prevents fluctuations in self-inductance due to magnetostriction, but also prevents the occurrence of defective products such as cracks during firing.

[0003] Japanese Patent Publication No. 3414502 discloses a high-temperature sinterable precious metal powder. This high-temperature sinterable precious metal powder is characterized by being obtained by coating the surface of the precious metal powder with a compound of a metal other than the precious metal and an organic acid, followed by heat treatment in an inert atmosphere. The publication states that coating the surface of the precious metal powder with another metal compound reduces the exposed surface area of ​​the precious metal and inhibits reaction between the precious metal powder and oxygen in the atmosphere. This allows for the preparation of a thick-film conductor paste that prevents various structural defects when the high-temperature sinterable precious metal powder is dispersed in an organic vehicle.

[0004] Japanese Patent Publication No. 4126698 discloses a conductive paste containing silver-based conductive metal powder, which is applied to form a pattern on a green sheet primarily composed of glass and oxide ceramics. This conductive paste is characterized by the addition of one or more barium compounds selected from fatty acid barium salts in a ratio of 0.16 to 1 wt. % based on the barium metal relative to the conductive metal powder, and one or more calcium compounds selected from fatty acid calcium salts in a ratio of 0.10 to 0.20 wt. % based on the calcium metal relative to the conductive metal powder. The publication also states that this composition provides good conductivity, and when printed on a glass-ceramic green sheet and fired, it reduces warping and deformation in the resulting ceramic multilayer substrate, increasing product yield and eliminating wiring defects and breakages, thereby improving reliability.

[0005] The coated copper powder disclosed in Japanese Patent No. 6433351 comprises copper powder and a coating of the copper powder. The copper powder contains 140 to 630 ppm of phosphorus as an impurity. The coating contains an organometallic compound of at least one alkaline earth metal selected from magnesium, calcium, strontium, and barium. This coated copper powder is characterized in that the concentration of the alkaline earth metal is less than 1.8 times the concentration of phosphorus contained in the copper powder. The publication also describes that when a sintering process is performed to form a copper conductor film using the coated copper powder, the alkaline earth metal forms a compound with the impurities contained in the copper powder. This suppresses the reaction between copper and the impurities during the sintering process, resulting in a copper conductor film with high conductivity.

[0006] The conductive paste disclosed in JP 2019-36435 A contains a conductive powder, a binder resin, and an organic solvent. In this conductive paste, the organic solvent has a Fedors solubility parameter of 9.0 (cal / cm 3 ) 0.5 A first solvent having a Fedors solubility parameter of 10.0 (cal / cm 3 )0.5 The mixed solvent contains a second solvent having a Fedors solubility parameter of 9.0 (cal / cm 3 ) 0.5 More than 10.1(cal / cm 3 ) 0.5 The publication states that the first solvent is useful for suppressing the occurrence of sheet attack, but that when used alone it is likely to cause permeation of conductive powder. The publication also states that the second solvent is useful for suppressing the permeation of conductive powder, but that when used alone it is likely to cause sheet attack. According to the technology described in the publication, the advantages of the first solvent and the second solvent are optimally utilized, making it possible to favorably form an electrode in which both the occurrence of sheet attack and the permeation of conductive powder are suppressed. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-268164 [Patent Document 2] Patent No. 3414502 [Patent Document 3] Patent No. 4126698 [Patent Document 4] Patent No. 6433351 [Patent Document 5] Japanese Patent Application Publication No. 2019-36435 Summary of the Invention [Problem to be solved by the invention]

[0008] The present inventors have discovered that when silver powder contains phosphorus as an impurity, silver ions tend to diffuse from the silver film to the substrate when a silver paste containing such silver powder is fired to form a silver film, and that the higher the content of the impurity (here, phosphorus), the greater the tendency for silver ions to diffuse.

[0009] In view of these circumstances, the present inventors have a desire to suppress the diffusion of silver ions from the silver powder to the substrate in the process of forming a silver film (fired film) by heat-treating silver powder containing a predetermined amount of phosphorus. [Means for solving the problem]

[0010] The technology disclosed herein provides a method for producing a laminate including a substrate and a silver film on the substrate. This method includes applying silver powder containing 50 ppm to 500 ppm of phosphorus as an impurity and additive A, which is a barium compound, to the substrate, and then heat-treating the substrate, the silver powder, and additive A applied to the substrate to form a silver film on the substrate. This configuration can suppress the diffusion of silver ions from the silver powder to the substrate during the process of forming a silver film (fired film) by heat-treating silver powder containing a predetermined amount of phosphorus.

[0011] The technology disclosed herein provides a method for manufacturing an electronic component. This manufacturing method includes the method for manufacturing the laminate described above. With this configuration, it is possible to provide an electronic component in which diffusion of silver ions into the substrate is suppressed.

[0012] The technology disclosed herein provides a silver paste. The silver paste contains silver powder containing 50 ppm to 500 ppm of phosphorus as an impurity, a resin binder, an organic solvent, and additive A. Additive A is a barium compound. This configuration can suppress the diffusion of silver ions from the silver powder into the substrate during the process of forming a silver film (fired film) by heat treating silver powder containing a predetermined amount of phosphorus.

[0013] The technology disclosed herein provides a coated silver powder. The coated silver powder includes silver powder containing 50 ppm to 500 ppm of phosphorus as an impurity and a coating containing a barium compound on the surface of the silver powder. This configuration makes it possible to suppress the diffusion of silver ions from the silver powder to the substrate during the process of forming a silver film (fired film) by heat treating the silver powder containing a predetermined amount of phosphorus. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic cross-sectional view of a multilayer chip inductor 1. As shown in FIG. [Figure 2] Figure 2 is an image of Example 21. [Figure 3] Figure 3 is an image of Example 24. DETAILED DESCRIPTION OF THE INVENTION

[0015] Preferred embodiments of the technology disclosed herein are described below. Matters necessary for implementing the technology disclosed herein, other than those specifically mentioned in this specification, can be understood based on the technical content taught by this specification and the general technical common sense of a person skilled in the art. The technology disclosed herein can be implemented based on the content disclosed in this specification and the general technical common sense of a person skilled in the art. In this specification and claims, the terms A to B (A and B are arbitrary numerical values) refer to values ​​greater than A and less than B, and also encompass values ​​greater than A and less than B.

[0016] For example, silver powder is sometimes used to form internal electrodes of electronic components. The process for manufacturing electronic components may include a step of subjecting the silver powder to heat treatment to sinter the silver powder. It has long been known that heat treatment tends to generate silver ions from the silver powder and diffuse them into the substrate. The diffusion of silver ions generated by heat treatment is undesirable because it may lead to short circuits between internal electrodes.

[0017] However, silver powder may contain unavoidable impurities due to its manufacturing process. In particular, the greater the content of phosphorus as an impurity, the greater the degree of silver ion generation associated with heat treatment, for example. The present inventors have conducted research into silver powder containing a predetermined amount of phosphorus as an impurity, with the aim of suppressing the diffusion of silver ions generated by heat treatment into the substrate.

[0018] The technology disclosed herein provides a method for producing a laminate including a substrate and a silver film on the substrate. This method includes applying silver powder containing 50 ppm to 500 ppm of phosphorus as an impurity and additive A, which is a barium compound, to the substrate; and heat-treating the substrate, the silver powder, and additive A applied to the substrate to form a silver film on the substrate.

[0019] First Embodiment This manufacturing method includes, for example, a preparing step, an applying step, and a firing step. The preparing step is, for example, a step of preparing silver powder and additive A. In this embodiment, a silver paste is prepared in the preparing step. The silver paste contains, for example, silver powder, a resin binder, an organic solvent, and additive A.

[0020] Silver powder is a component that imparts electrical conductivity to a fired film (hereinafter also referred to as "silver film") obtained by firing a silver paste. Silver powder contains, for example, 50 ppm to 500 ppm of phosphorus as an impurity. The inventors have found that when silver powder containing 50 ppm to 500 ppm of phosphorus as an impurity is subjected to heat treatment (here, firing treatment), silver ions are more likely to be generated and the generated silver ions are more likely to diffuse into the substrate. For this reason, the configuration of the silver paste disclosed herein is suitable for producing a silver film using silver powder containing 50 ppm to 500 ppm of phosphorus as an impurity. The content of phosphorus as an impurity in the silver powder may be, for example, 60 ppm or more, or 70 ppm or more. The content of phosphorus as an impurity in the silver powder may be, for example, 450 ppm or less, 400 ppm or less, 350 ppm or less, 300 ppm or less, 250 ppm or less, 200 ppm or less, 180 ppm or less, 160 ppm or less, or 150 ppm. In this specification, the "content of phosphorus as an impurity in the silver powder" refers to the content of phosphorus relative to the entire silver powder. The silver powder may contain a predetermined amount of phosphorus as an impurity, and may also contain impurities other than phosphorus (e.g., boron, calcium, chromium, copper, iron, sodium, nickel, phosphorus, silicon, zinc, etc.). Although not particularly limited, silver powder produced by an atomization method can be preferably used as the silver powder. The silver content in the silver powder and the impurity content in the silver powder can be measured, for example, by using ICP atomic emission spectroscopy.

[0021] The average particle diameter of the silver powder is not particularly limited and can be appropriately set depending on the application of the silver paste. For example, in applications involving the formation of internal electrodes of electronic components, the average particle diameter is, for example, 0.5 μm or more, preferably 1 μm or more, and more preferably 3 μm or more. By setting the average particle diameter within this range, for example, aggregation of the silver powder in the paste can be suppressed and the packing of the silver powder in the silver film can be improved. On the other hand, the average particle diameter is, for example, 20 μm or less, preferably 15 μm or less, more preferably 10 μm or less, and even more preferably 7.5 μm or less. By setting the average particle diameter within this range, for example, the sintering property between particles can be improved, thereby improving the low resistance of the silver film. The silver powder may, for example, contain two or more particle groups having different particle size distributions. Therefore, the silver powder may be, for example, a mixed powder in which two or more particle groups having different average particle diameters are mixed. In this specification, the term "average particle size" refers to the 50% cumulative particle size in the particle size distribution (number basis) of equivalent circle diameters based on electron microscope observation.

[0022] When the total silver powder contained in the silver paste is taken as 100% by mass, the content of silver powder containing 50 ppm to 500 ppm of phosphorus as an impurity is generally 40% by mass or more, for example, 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, and the closer to 100% by mass the better.

[0023] When the entire silver paste is taken as 100% by mass, the content of silver powder is, for example, 80% by mass or more, preferably 85% by mass or more, and more preferably 90% by mass or more. This can improve the density of the silver film, for example. When the entire silver paste is taken as 100% by mass, the content of silver powder is generally 99% by mass or less, for example, 98% by mass or less, preferably 97% by mass or less, more preferably 96% by mass or less, and even more preferably 95% by mass or less.

[0024] The resin binder is a component that, for example, when the silver paste is applied to a substrate, binds the particles constituting the silver powder to each other and also binds the silver powder to the substrate. The resin binder is preferably a component that burns out when the silver paste is fired. The type of resin binder is not particularly limited, and a resin binder that is used in conventional silver pastes of this type can be used, depending on, for example, the method of applying the silver paste to the substrate.

[0025] Examples of resin binders include celluloses such as methyl cellulose, ethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, and carboxymethyl cellulose; acrylic resins such as polymethyl methacrylate, polyethyl methacrylate, and polybutyl methacrylate; epoxy resins; phenolic resins; alkyd resins; polyvinyl alcohol; polyvinyl butyral; and rosins such as rosin and maleated rosin. As the resin binder, one of the above may be used alone, or two or more may be used in combination. When the entire silver paste is taken as 100% by mass, the content of the resin binder is generally 0.1% by mass to 3% by mass, and preferably 0.3% by mass to 1% by mass.

[0026] The organic solvent is a component that dissolves or disperses, for example, silver powder, resin binder, additive A, and other components. The type of organic solvent is not particularly limited and can be selected from among conventionally known organic solvents. For example, the organic solvent can be one of the organic solvents described below, or two or more of them can be used in appropriate combination. Examples include alcohol-based solvents having an -OH group, ether-based solvents having an ether bond (RO-R'), ester-based solvents having an ester bond (RC(=O)-O-R'), and hydrocarbon-based solvents composed of carbon atoms and hydrogen atoms.

[0027] Examples of alcohol-based solvents and ether-based solvents include terpineol, texanol, dihydroterpineol, benzyl alcohol, 3-methoxy-3-methyl-1-butanol, diethylene glycol, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol-n-butyl ether, dipropylene glycol methyl-n-propyl ether, dipropylene glycol methyl ether acetate, and dipropylene glycol methyl-n-butyl ether.

[0028] Examples of ester-based solvents include 3-methoxy-3-methyl-1-butanol acetate, 3-methoxybutyl acetate, 1,3-butylene glycol diacetate, 1,4-butanediol diacetate, 1,6-hexanediol diacetate, propylene glycol monomethyl ether acetate, isobornyl acetate, carbitol acetate, ethyl diglycol acetate, butyl cellosolve acetate, propylene glycol diacetate, diethylene glycol monobutyl ether acetate, terpineol acetate, dihydroterpineol acetate, etc. Examples of hydrocarbon-based solvents include aliphatic hydrocarbon solvents such as petroleum hydrocarbons, naphtha, dipentene, turpentine oil, and mineral spirits; aromatic hydrocarbon solvents such as benzene, toluene, and xylene; paraffin-based solvents such as normal paraffins and isoparaffins; and naphthenic solvents such as monocyclic naphthenes and bicyclic naphthenes. When the entire silver paste is taken as 100% by mass, the content of the organic solvent is generally 0.5% to 10% by mass, and preferably 2% to 7% by mass.When the entire silver paste is taken as 100% by mass, the content of the organic solvent is generally 0.5% to 10% by mass, and preferably 2% to 7% by mass.

[0029] Additive A is, for example, a component that reacts with phosphorus, an impurity in silver powder, to form a chemically stable compound (e.g., barium phosphate). Additive A is a barium compound. The barium compound as additive A may be a barium-containing inorganic compound or an organic barium compound. Examples of barium-containing inorganic compounds include barium oxide, barium carbonate, and barium titanate. Examples of organic barium compounds include barium formate, barium acetate, barium propionate, barium stearate, barium 2-ethylhexanate, barium 2-ethylhexoxide, barium acetate, barium isopropoxide, barium ethoxide, barium 2-methoxyethoxide, barium oxalate, barium octylphenolate, barium diacrylate, barium diundecanoate, barium distearate, barium ditetracosanoate, barium dineodecanoate, barium dinonanoate, barium dipalmitate, barium diphenolate, barium diheptadecanoate, barium dilactate, barium nonylphenolate, and barium bis(12-hydroxyoctadecanoate). barium bis(2,2-dimethyloctanoate), barium bis(2-ethylhexanoate), barium bis(2-methylbenzoate), barium bis(3-methylbenzoate), barium bis(4-tert-butylbenzoate), barium bis(4-octylphenolate), barium bis(4-nonylphenolate), barium bis(4-methylbenzoate), barium bis(tert-butylbenzoate), barium bis(isobutylmaleate), barium bis(cyclohexylphenolate), barium bis(dipentylphosphate), barium bis(dimethylhexanoate), barium bis(propane 2-olate), barium dibutoxide, barium dipropoxide, and the like.

[0030] The amount of additive A added is preferably approximately 0.01 to 5 parts by mass relative to 100 parts by mass of silver powder. The greater the amount of additive A added relative to the silver powder, the more likely it is that the diffusion of silver ions into the substrate can be suppressed. From this perspective, the amount of additive A added is preferably 0.03 parts by mass or more, more preferably 0.05 parts by mass or more, relative to 100 parts by mass of silver powder. On the other hand, the smaller the amount of additive A added relative to the silver powder, the lower the resistance of the silver film can be. From this perspective, the amount of additive A added is preferably 4 parts by mass or less, more preferably 3 parts by mass or less, even more preferably 2.5 parts by mass or less, and particularly preferably 1.5 parts by mass or less or 1 part by mass or less, relative to 100 parts by mass of silver powder. When additive A is an organic barium compound, the amount added in terms of barium oxide is preferably set within the above-mentioned range.

[0031] The amount of barium added per 100 parts by mass of silver powder is preferably approximately 0.005 to 3 parts by mass. The greater the amount of barium added per 100 parts by mass of silver powder, the more likely it is that the diffusion of silver ions into the substrate can be suppressed. From this perspective, the amount of barium added is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, and even more preferably 0.03 parts by mass or more, per 100 parts by mass of silver powder. On the other hand, the smaller the amount of barium added per 100 parts by mass of silver powder (for example, the smaller the amount of additive A added per 100 parts by mass of silver powder), the lower the resistance of the silver film can be. From this perspective, the amount of barium added is preferably 2.5 parts by mass or less, more preferably 2 parts by mass or less, and even more preferably 1.5 parts by mass or less or 1 part by mass or less, per 100 parts by mass of silver powder. When additive A is an organic barium compound, the amount added in terms of barium oxide is preferably set within the above-mentioned range.

[0032] The amount of barium added to 100 mol% of silver powder, M Ba is roughly 1×10 -4 mol%~3.0×10 -2 The amount of barium added to silver powder is M BaAs the amount of barium added, M Ba is 1.5 × 10 for 100 mol% silver powder. -4 mol% or more is preferable, and 2.0 × 10 -4 mol% or more is more preferable, and 2.5×10 -4 mol% or more is more preferable. On the other hand, the amount of barium added to the silver powder M Ba The smaller the amount of additive A added to the silver powder, the lower the resistance of the silver film. Ba is 2.5 × 10 for 100 mol% silver powder. -2 mol% or less is preferable, and 2.0 × 10 -2 mol% or less is more preferable, and 1.5 × 10 -2 mol% or less is more preferable, and 1.0 × 10 -2 mol% or less or 5.0 x 10 -3 It is more preferable that the amount is not more than mol %. When the additive A is an organic barium compound, the amount added in terms of barium oxide is preferably set within the above range.

[0033] The amount of barium added to 100 mol% of silver powder, M Ba (mol%) and the phosphorus content M when the total silver powder is taken as 100 mol%. P (mol%) (M Ba / M P ) is preferably about 0.1 to 50. From the viewpoint of better realizing the technology disclosed herein, the ratio (M Ba / M P ) is preferably 0.3 or more, more preferably 0.5 or more, and even more preferably 0.7 or more. Ba / M P ) is preferably 35 or less, more preferably 25 or less, and even more preferably 15 or less or 10 or less.

[0034] In addition to the above-described components, the silver paste may contain various additive components. Examples of additive components include conventionally known additive components used in this type of application. Examples of additive components include inorganic fillers, dispersants, surfactants, viscosity modifiers, antifoaming agents, plasticizers, antioxidants, and pigments. When the entire silver paste is taken as 100% by mass, the content of the additive components is generally 5% by mass or less, for example, 3% by mass or less, preferably 2% by mass or less, and more preferably 1% by mass or less.

[0035] The silver paste is prepared, for example, by mixing the above-described components. As a mixer for mixing, any conventional mixer used for this type of application can be used without any particular limitation.

[0036] The application step is, for example, a step of applying the silver powder and additive A prepared in the preparation step onto a substrate. In this embodiment, in the application step, the silver paste prepared in the preparation step is applied onto the substrate. As a means for applying the silver paste, any conventionally known method used for this type of application may be used. For example, various printing methods such as screen printing, gravure printing, offset printing, and inkjet printing; doctor blade methods; spray methods; etc. are preferably used.

[0037] The firing step is, for example, a step of subjecting the substrate and the silver powder and additive A applied thereto to a heat treatment (firing treatment) after the application step. In this embodiment, in the firing step, the substrate and the silver paste applied thereto are heat treated after the application step. The conditions for the heat treatment (firing treatment) are not particularly limited and can be set appropriately depending on the application of the laminate, etc. The heat treatment temperature can be set, for example, to a temperature at which the organic components in the silver paste burn out and the silver powder sinters. The heat treatment temperature can be set, for example, to 500°C to 1000°C (e.g., 600°C to 800°C). The heat treatment time can be set, for example, to 30 minutes to 10 hours. The heat treatment atmosphere can be, for example, air, or an inert atmosphere such as a nitrogen atmosphere or a rare gas atmosphere.

[0038] The above describes one embodiment of the method for manufacturing a laminate disclosed herein. In this embodiment, the applying step includes applying a silver paste containing silver powder, a resin binder, an organic solvent, and additive A to the substrate. As described above, the silver powder used here contains a predetermined amount of phosphorus as an impurity. Therefore, silver ions are generated by heat treatment (firing treatment) and easily diffuse into the substrate, for example. In contrast, by adding additive A, a barium compound, to the silver paste, a chemically stable compound (e.g., barium phosphate) is formed. Therefore, the diffusion of silver ions generated by heat treatment into the substrate is suitably suppressed. In addition, because a silver paste is used in the applying step, a simpler process of mixing the respective raw materials can be adopted in the preparing step. Therefore, the configuration of the first embodiment can also achieve the effect of improving the productivity of silver films.

[0039] The method for manufacturing a laminate disclosed herein is not limited to the above-described embodiment. For example, this manufacturing method may include any other steps in addition to the steps described above. This manufacturing method may also include, for example, a drying step, a pressing step, etc., as necessary. The drying step is, for example, a step of volatilizing the organic solvent in the silver paste, and may be performed between the application step and the firing step. The drying conditions are not particularly limited and can be set appropriately depending on the type and amount of the organic solvent used. The pressing step is, for example, a step of pressing the silver powder applied to the substrate, and may be performed between the application step and the firing step. The pressing conditions are not particularly limited and can be set appropriately depending on the application of the laminate, the desired thickness of the silver film, etc.

[0040] Second Embodiment In the first embodiment, silver paste is applied in the applying step. However, in the manufacturing method disclosed herein, it is sufficient that silver powder and additive A are applied in the applying step, and what is applied is not limited to silver paste.

[0041] In the second embodiment, a coated silver powder is prepared in a preparation step. Here, the coated silver powder includes silver powder containing 50 ppm to 500 ppm of phosphorus as an impurity, and a coating portion containing additive A on the surface of the silver powder. The procedure for preparing the coated silver powder is not particularly limited, and for example, a method of mixing silver powder and additive A can be adopted. Here, first, silver powder, additive A, and an organic solvent are prepared. As the silver powder, the silver powder described in the first embodiment may be used. As additive A, the additive A described in the first embodiment may be used, but among them, an organic barium compound is preferably used. As the organic solvent, the additive A described in the first embodiment may be used, but among them, an alcohol such as ethanol is preferably used.

[0042] Next, the silver powder, additive A, and organic solvent are mixed. For example, a first mixture of additive A and organic solvent may be prepared first, and then silver powder may be added to the first mixture and further mixed to prepare a second mixture. When mixing after adding the silver powder, it is preferable to apply ultrasonic energy to the material. The conditions for applying ultrasonic energy are not particularly limited and can be set appropriately. Next, the obtained second mixture can be dried, heat-treated, pulverized, classified, etc. as necessary to obtain coated silver powder.

[0043] In this embodiment, the coated silver powder is applied onto a substrate in the application step, and the coated silver powder applied onto the substrate is then subjected to a heat treatment (firing treatment) to produce a laminate.

[0044] As described above, in this embodiment, the manufacturing method includes applying a coated silver powder comprising silver powder and a coating containing additive A on the surface of the silver powder to the substrate. That is, in this embodiment, a coated silver powder in which silver powder and additive A are integrated is used. Therefore, the diffusion of silver ions into the substrate can be more efficiently suppressed.

[0045] It should be noted that the second embodiment is similar to the first embodiment in matters other than those described here, and therefore the description here will be omitted.

[0046] The technology disclosed herein provides a method for manufacturing an electronic component. The method for manufacturing an electronic component may include manufacturing a laminate using the above-described method for manufacturing a laminate. Although not particularly limited, the above-described method for manufacturing a laminate is preferably used to form electrodes of electronic components such as inductance components and capacitor components. The above-described method for manufacturing a laminate has the effect of suppressing the diffusion of silver ions into the substrate. Therefore, by including such a method for manufacturing a laminate, it is possible to provide an electronic component in which the diffusion of silver ions into the substrate is suppressed. In the electronic component, for example, the risk of internal short circuits is better reduced.

[0047] The following describes a multilayer chip inductor, an example of an electronic component. Figure 1 is a schematic cross-sectional view of a multilayer chip inductor 1. Note that the dimensional relationships (length, width, thickness, etc.) in Figure 1 do not necessarily reflect the actual dimensional relationships. The symbols X and Z in the drawing represent the left-right and up-down directions, respectively. However, these are directions merely used for convenience of explanation.

[0048] 1 is not particularly limited to a specific size, but may be, for example, a 1608 shape (1.6 mm × 0.8 mm), a 2520 shape (2.5 mm × 2.0 mm), etc. The multilayer chip inductor 1 includes a main body 10 and external electrodes 20.

[0049] The multilayer chip inductor 1 includes a main body 10 and external electrodes 20 provided on both side surfaces of the main body 10 in the left-right direction X. In the main body 10, for example, a plurality of magnetic layers 12 are stacked in the up-down direction Z and integrated with each other. Examples of materials that can be used to form the magnetic layers 12 include metal materials such as ferrite magnetic materials such as Ni-Cu-Zn ferrite, Fe-Cr-Si alloys, Fe-Al-Si alloys, and Fe-Si-M soft magnetic alloys (wherein M is at least one of chromium, aluminum, and titanium).

[0050] Coil conductors are provided between the magnetic layers 12 as internal electrode layers 14. In this embodiment, the coil conductors are silver pastes as disclosed herein or sintered films of coated silver powder as disclosed herein. Two coil conductors adjacent to each other in the vertical direction Z, sandwiching a magnetic layer 12 therebetween, are electrically connected through via holes provided in the magnetic layers 12. As a result, the internal electrode layers 14 are configured in a three-dimensional coil shape (spiral shape). Both ends of the coil conductors are connected to external electrodes 20, respectively.

[0051] The multilayer chip inductor 1 can be manufactured, for example, by the following procedure. First, a magnetic paste containing a metal material for the magnetic layer 12, a binder, and an organic solvent is prepared, and then this is applied to a carrier sheet to form a green sheet. Next, the green sheet is rolled and dried. The green sheet is then cut to a desired size to obtain multiple magnetic layer-forming sheets. Next, via holes are formed at predetermined positions on the magnetic layer-forming sheets using a punch or the like. Next, a silver paste disclosed herein is printed in a predetermined coil pattern at predetermined positions on multiple magnetic layer-forming sheets and dried. Next, these are stacked and pressure-bonded to form a laminate of unfired green sheets. This is fired to integrally fire the green sheets, forming the main body 10 including the magnetic layer 12 and the internal electrode layer 14. Next, an appropriate external electrode-forming paste is applied to both ends of the main body 10 and fired to form the external electrodes 20. In this manner, the multilayer chip inductor 1 can be manufactured.

[0052] As described above, the technology disclosed herein provides a method for producing a laminate including a substrate and a silver film on the substrate. This method includes applying silver powder containing 50 ppm to 500 ppm of phosphorus as an impurity and additive A, which is a barium compound, to the substrate, and subjecting the substrate and the silver powder and additive A applied to the substrate to a heat treatment to form a silver film on the substrate.

[0053] The silver powder used in the manufacturing method disclosed herein contains 50 ppm to 500 ppm of phosphorus as an impurity. When silver powder contains phosphorus, which has high electronegativity, for example, electrons in the electron cloud of silver are attracted to the phosphorus, causing a bias in the electron distribution and making it easier for silver ions to be generated. In addition, when heat is applied to the silver powder, the impurities tend to migrate to the surface of the silver powder. When silver powder is subjected to a heat treatment (calcination treatment), the impurities migrate to the surface of the silver powder, making it easier for silver ions to diffuse from the surface of the silver powder into the substrate. For this reason, it can be said that phosphorus-containing silver powder is a silver powder that is inherently more susceptible to the diffusion of silver ions into the substrate due to calcination.

[0054] In contrast, in this manufacturing method, additive A, which is a barium compound, is used together with silver powder. When barium compounds react with phosphorus, they form, for example, chemically stable barium phosphate. Therefore, when silver powder and additive A are applied together to a substrate, the impurity phosphorus reacts with additive A during heat treatment to form chemically stable barium phosphate. In this way, because additive A can form a chemically stable compound with phosphorus, in the process of forming a silver film (fired film) by heat treating silver powder containing a predetermined amount of phosphorus, the bias in the electron distribution of silver is suppressed, and the diffusion of silver ions from the silver powder to the substrate can be suppressed.

[0055] Test examples relating to the technology disclosed herein will be described below, but it is not intended that the technology disclosed herein be limited to the following test examples.

[0056] <Test 1> --Example 11-- In Test 1, silver powder A with an average particle size of 5 μm and a phosphorus concentration of 146 ppm was prepared. Ethyl cellulose was prepared as the resin binder. Diethylene glycol monobutyl ether acetate was prepared as the organic solvent. Barium titanate was prepared as the additive. The phosphorus concentration of silver powder A was measured using an ICP spectrometer (PS3520VDDII manufactured by Hitachi High-Tech Corporation).

[0057] The prepared silver powder A, resin binder, organic solvent, and additive were mixed using a mixer to prepare a silver paste. Here, when the total of silver powder A, resin binder, and organic solvent was 100% by mass, the content of silver powder A was 95% by mass, the content of resin binder was 0.5% by mass, and the content of organic solvent was 4.5% by mass. The amount of additive was 1 part by mass per 100 parts by mass of silver paste. Next, the silver paste was dried and pulverized to obtain paste powder. Next, using a uniaxial molding machine (hydraulic press PHK5-S manufactured by Towa Seiki Co., Ltd.), the paste powder was filled into a mold and pressed along the axial direction at a pressure of 78 MPa to obtain cylindrical pellets of paste powder with a diameter of 8 mm. Next, the pellets were placed on a glass substrate ("S7213" manufactured by Matsunami Glass Industry Co., Ltd.) and heat-treated in a belt furnace in an air atmosphere at 700°C for 0.5 hours.

[0058] After the heat treatment, a ring-shaped discolored area was formed on the glass substrate surrounding the periphery of the pellet. This discolored area was due to silver ions that had diffused from the pellet to the glass substrate. The diameter of the area including the pellet and the discolored area (hereinafter also referred to as the "diffusion diameter") was measured. Then, the following formula (A): Diffusion rate (%) = {(diffusion diameter - pellet diameter) / pellet diameter} x 100 (A) The diffusion rate (%) of silver ions from the pellet was calculated based on the above data. The results are shown in the corresponding columns in Table 1.

[0059] -Example 12 to Example 15- The additives used were the compounds shown in Table 1. Other than that, pellets for each example were prepared and the diffusion coefficient was calculated using the same materials and procedures as in Example 11. Note that for Example 12, the entry "-" in the "Additives" column in Table 1 indicates that no additives were added.

[0060] -Example 16~Example 18- Silver powder B having an average particle size of 5 μm and a phosphorus concentration of 70 ppm was used as the silver powder. Copper powder was used as the additive in the amount shown in the "Amount added (parts by mass)" column of Table 1. Other than that, pellets for each example were prepared using the same materials and procedures as in Example 11, and the diffusivity was calculated. The results are shown in the corresponding column in Table 1. Note that for Example 16, the "-" in the "Additive" column of Table 1 indicates that no additive was added.

[0061] [Table 1]

[0062] For Examples 11 to 18, the compounds (additives) added to the pastes of each example can form a coating on the surface of the silver powder. From the results shown in Table 1 for Examples 11 to 18, it was found that the use of the coated silver powder of Example 11, which includes silver powder and a coating containing a barium compound (here, barium titanate) on the surface of the silver powder, can suppress the diffusion of silver ions into the substrate (here, a glass substrate) due to firing.

[0063] <Test 2> -Example 21 to Example 24- A mixed powder of silver powder A and silver powder C was prepared as the silver powder. Silver powder C had an average particle size of 1.5 μm and a phosphorus concentration of 0 ppm. The mixing ratio (mass ratio) of silver powder A to silver powder C in the mixed powder (silver powder A:silver powder C) was 70:30. Ethyl cellulose was prepared as the resin binder. Diethylene glycol monobutyl ether acetate was prepared as the organic solvent. Barium carbonate was used as the additive in the amount listed in the "Addition amount (parts by mass)" column of Table 2. Pellets for each example were prepared using the same materials and procedures as in Example 11, and the diffusion coefficient was calculated. The results are shown in the corresponding column in Table 2. Note that for Example 21, a "-" in the "Additive" column of Table 2 indicates that no additive was added. For reference, Figure 2 shows an image of Example 21. Figure 3 shows an image of Example 24.

[0064] [Table 2]

[0065] Regarding Examples 21 to 24, the results shown in Table 2 indicate that by using the coated silver powders of Examples 22 to 24, which include silver powder and a coating portion containing a barium compound (here, barium carbonate) on the surface of the silver powder, the diffusion of silver ions into the substrate (here, a glass substrate) due to firing can be suppressed.

[0066] <Test 3> -Example 31A to Example 31E- Barium 2-methoxyethoxide was prepared as an additive. This additive was used so that the amount of barium oxide added was the amount listed in the "Amount Added (Parts by Mass)" column in Table 3. Other than that, pellets for each example were prepared using the same materials and procedures as in Example 11, and the diffusion coefficient was calculated. The results are shown in the corresponding columns in Table 3.

[0067] -Example 32A~Example 32C- Magnesium 2-methoxyethoxide was prepared as an additive. This additive was used so that the amount of magnesium oxide added was the amount shown in the "Amount Added (Parts by Mass)" column in Table 3. Other than that, pellets for each example were prepared using the same materials and procedures as in Example 11, and the diffusion coefficient was calculated. The results are shown in the corresponding columns in Table 3.

[0068] -Example 33A~Example 33C- Calcium 2-methoxyethoxide was prepared as an additive. This additive was used so that the amount of calcium oxide added was the amount listed in the "Amount Added (Parts by Mass)" column in Table 3. Other than that, pellets for each example were prepared using the same materials and procedures as in Example 11, and the diffusion coefficient was calculated. The results are shown in the corresponding columns in Table 3.

[0069] -Example 34A to Example 34C- Strontium 2-methoxyethoxide was prepared as an additive. This additive was used so that the amount of strontium oxide added was the amount shown in the "Amount added (parts by mass)" column in Table 3. Other than that, pellets for each example were prepared using the same materials and procedures as in Example 11, and the diffusion coefficient was calculated. The results are shown in the corresponding columns in Table 3.

[0070] -Example 35A~Example 35C- A mixed powder of silver powder B and silver powder C was prepared as the silver powder. The mixing ratio (mass ratio) of silver powder B to silver powder C in the mixed powder (silver powder B:silver powder C) was 70:30. Barium 2-methoxyethoxide was used as an additive, with the amount of barium oxide added being the amount listed in the "Amount Added (Parts by Mass)" column in Table 3. Other than that, pellets for each example were prepared using the same materials and procedures as in Example 11, and the diffusivity was calculated. The results are shown in the corresponding column in Table 3. Note that for Example 35C, the "-" in the "Additive" column in Table 3 indicates that no additive was added.

[0071] [Table 3]

[0072] From the results shown in Table 3 for Examples 31A to 31E, Examples 32A to 32C, Examples 33A to 33C, Examples 34A to 34C, and Examples 35A to 35C, it was found that by using the coated silver powders of Examples 31A to 31E, Example 35A, and Example 35B, which include silver powder and a coating portion containing a barium compound (here, a compound derived from an organic barium compound) on the surface of the silver powder, the diffusion of silver ions into the substrate (here, a glass substrate) due to firing can be suppressed.

[0073] <Test 4> -Examples 41 to 43- Barium 2-methoxyethoxide, silver powder A, and alcohol (ethanol) as an organic solvent were placed in a mixer and stirred and mixed for 10 minutes while applying ultrasonic energy. The amount of barium 2-methoxyethoxide was such that the amount of barium oxide added corresponded to the amount listed in the "Amount Added (Parts by Mass)" column in Table 4. The amount of silver powder A was 10 g. The amount of alcohol (ethanol) was 1.5 g. The mixture was then dried at 70°C to volatilize the organic solvent. The dried powder was crushed in a mortar to obtain coated silver powders for each example. Using a uniaxial molding machine, the obtained silver powder (0.4 g) was packed into a mold and pressed axially at 78 MPa to obtain cylindrical pellets with a diameter of 8 mm. The pellets were then subjected to the same heat treatment as in Example 11. The diffusivity of each example was determined using the same method as in Example 11. The results are shown in the corresponding columns in Table 4.

[0074] --Example 44-- No additives were used. Other than that, pellets of this example were prepared using the same materials and procedures as in Examples 41 to 43, and the diffusion coefficients were calculated. Note that a "-" in the "Additives" column of Table 4 indicates that no additives were added. The results are shown in the corresponding column of Table 4.

[0075] [Table 4]

[0076] Regarding Examples 41 to 43, Test 4 showed that mixing silver powder A and barium (methoxyethoxyethoxide) under the above-mentioned conditions resulted in the barium (methoxyethoxyethoxide) adhering to the surface of silver powder A. The results shown in Table 4 demonstrate that the use of the coated silver powders of Examples 41 to 43, which include silver powder and a coating containing a barium compound (here, a compound derived from an organic barium compound) on the surface of the silver powder, can suppress the diffusion of silver ions into the substrate (here, a glass substrate) due to firing.

[0077] The technology disclosed herein may include the following items. Section 1: A method for producing a laminate comprising a substrate and a silver film on the substrate, the method comprising: Applying silver powder containing 50 ppm or more and 500 ppm or less of phosphorus as an impurity and additive A which is a barium compound onto a substrate; heat-treating the substrate and the silver powder and additive A applied to the substrate to form a silver film on the substrate; The manufacturing method includes the steps of: Section 2: Item 2. The manufacturing method according to Item 1, wherein the applying step includes applying a silver paste containing the silver powder, a resin binder, an organic solvent, and the additive A onto the substrate. Section 3: Item 3. The manufacturing method according to item 2, wherein the additive A includes at least one of an organic barium compound, barium oxide, barium titanate, and barium carbonate. Section 4: Item 2. The manufacturing method according to Item 1, wherein the applying step includes applying a coated silver powder comprising the silver powder and a coating portion containing the additive A on the surface of the silver powder to the substrate. Section 5: Item 5. The method according to item 4, wherein the additive A is an organic barium compound. Item 6: Item 6. The manufacturing method according to any one of Items 1 to 5, wherein in the applying, 0.03 parts by mass or more and 3 parts by mass or less of the additive A is used with respect to 100 parts by mass of the silver powder. Section 7: A method for producing an electronic component, comprising producing the laminate using the production method described in items 1 to 6. Section 8: A silver paste comprising: The silver powder contains 50 ppm or more and 500 ppm or less of phosphorus as an impurity, a resin binder, an organic solvent, and an additive A, wherein the additive A is a barium compound. Section 9: Item 9. The silver paste according to item 8, wherein the additive A includes at least one of an organic barium compound, barium oxide, barium titanate, and barium carbonate. Section 10: Item 10. The silver paste according to Item 8 or 9, comprising 0.03 parts by mass or more and 3 parts by mass or less of Additive A per 100 parts by mass of the silver powder. Section 11: Item 11. The silver paste according to any one of items 8 to 10, which is used in the production of electronic components. Section 12: A coated silver powder comprising: Silver powder containing 50 ppm or more and 500 ppm or less of phosphorus as an impurity; A coating portion containing a barium compound on the surface of the silver powder; The coated silver powder comprises: Section 13: Item 13. The coated silver powder according to Item 12, wherein the barium compound is an organic barium compound. Section 14: Item 14. The coated silver powder according to item 12 or 13, which is used for producing electronic components. [Explanation of symbols]

[0078] 1 Multilayer chip inductor 10 Main Unit 12 Magnetic layer 14 Internal electrode layer 20 External electrodes

Claims

1. A method for producing a laminate comprising a substrate and a silver film on the substrate, the method comprising: Applying silver powder containing 50 ppm to 500 ppm of phosphorus as an impurity and additive A which is a barium compound onto a substrate; heat-treating the substrate and the silver powder and additive A applied to the substrate to form a silver film on the substrate; The manufacturing method includes the steps of:

2. 2. The manufacturing method according to claim 1, wherein the applying step comprises applying a silver paste containing the silver powder, a resin binder, an organic solvent, and the additive A onto the substrate.

3. The manufacturing method according to claim 2 , wherein the additive A includes at least one of an organic barium compound, barium oxide, barium titanate, and barium carbonate.

4. The manufacturing method according to claim 1, wherein the applying step includes applying a coated silver powder comprising the silver powder and a coating portion containing the additive A on a surface of the silver powder onto the substrate.

5. The method according to claim 4 , wherein the additive A is an organic barium compound.

6. The manufacturing method according to claim 1, wherein in the applying, 0.03 parts by mass or more and 3 parts by mass or less of the additive A is used with respect to 100 parts by mass of the silver powder.

7. A method for manufacturing an electronic component, comprising manufacturing the laminate using the manufacturing method according to any one of claims 1 to 6.

8. A silver paste comprising: The silver powder contains 50 ppm or more and 500 ppm or less of phosphorus as an impurity, a resin binder, an organic solvent, and an additive A, wherein the additive A is a barium compound.

9. 9. The silver paste of claim 8, wherein Additive A includes at least one of an organic barium compound, barium oxide, barium titanate, and barium carbonate.

10. 10. The silver paste according to claim 8, comprising 0.03 parts by mass or more and 3 parts by mass or less of the additive A relative to 100 parts by mass of the silver powder.

11. The silver paste according to claim 8 or 9, which is used in the production of electronic components.

12. A coated silver powder comprising: Silver powder containing 50 ppm to 500 ppm of phosphorus as an impurity; A coating portion containing a barium compound on the surface of the silver powder; The coated silver powder comprises:

13. 13. The coated silver powder according to claim 12, wherein the barium compound is an organic barium compound.

14. The coated silver powder according to claim 12 or 13, which is used in the production of electronic components.

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