WO2024070341A1 - Procédé de production de nanofil métallique - Google Patents

Procédé de production de nanofil métallique Download PDF

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WO2024070341A1
WO2024070341A1 PCT/JP2023/030248 JP2023030248W WO2024070341A1 WO 2024070341 A1 WO2024070341 A1 WO 2024070341A1 JP 2023030248 W JP2023030248 W JP 2023030248W WO 2024070341 A1 WO2024070341 A1 WO 2024070341A1
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metal
acid
metal nanowires
crushing
isolated
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PCT/JP2023/030248
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English (en)
Japanese (ja)
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順二 川口
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富士フイルム株式会社
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D1/00—Electroforming
    • C25D1/04—Wires; Strips; Foils
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D1/00—Electroforming
    • C25D1/20—Separation of the formed objects from the electrodes with no destruction of said electrodes
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C25D11/18—After-treatment, e.g. pore-sealing
    • C25D11/20—Electrolytic after-treatment

Definitions

  • the present invention relates to a method for producing metal nanowires.
  • Patent Document 1 describes a method for obtaining metal nanowires by subjecting an aluminum base to an anodizing treatment, an aluminum base removal treatment, a perforation treatment, a metal filling treatment, and an anodized film removal treatment, in that order ([0025] [ Figure 1]).
  • the inventors have investigated the metal nanowires described in Patent Document 1 and have found that when used as a conductive bonding material (such as a material used to bond a semiconductor chip to a substrate), the bonding strength may not be sufficient.
  • the present invention aims to provide a method for manufacturing metal nanowires that can produce metal nanowires with high bonding strength when bonded.
  • the inventors discovered that by isolating the metal filled into the porous space from the anodized film and the valve metal substrate and then carrying out a crushing process, metal nanowires having high bonding strength when bonded can be obtained, and thus completed the present invention. That is, it has been found that the above object can be achieved by the following configuration.
  • a method for producing metal nanowires. [2] The method for producing metal nanowires according to [1], further comprising a drying step of drying the isolated metal between the isolating step and the crushing step. [3] The method for producing metal nanowires according to [1] or [2], further comprising a step of reducing or removing a surface oxide layer of the isolated metal between the isolation step and the crushing step.
  • [4] The method for producing metal nanowires according to any one of [1] to [3], further comprising a protective layer forming step of forming a protective layer containing a corrosion inhibitor on the isolated metal.
  • [5] The method for producing metal nanowires according to any one of [1] to [4], wherein the valve metal substrate contains aluminum.
  • the metal filling step includes a plating step.
  • the isolation step includes a dissolution step.
  • the present invention provides a method for producing metal nanowires that can produce metal nanowires with high bonding strength when bonded.
  • FIG. 1A is a schematic cross-sectional view of a valve metal substrate prior to an anodization step in a procedure showing an example of a method for producing metal nanowires of the present invention.
  • FIG. 1B is a schematic cross-sectional view of a structure after an anodization step in the procedure showing one example of a method for producing metal nanowires of the present invention.
  • FIG. 1C is a schematic cross-sectional view of a structure after a metal filling step in the procedure showing one example of a method for producing metal nanowires of the present invention.
  • FIG. 1D is a schematic cross-sectional view of the structure after the isolation step in the procedure showing one example of the method for producing metal nanowires of the present invention.
  • FIG. 1E is a schematic cross-sectional view of a structure (metal nanowires) after a crushing step in the procedure showing one example of a method for producing metal nanowires of the present invention.
  • the manufacturing method of metal nanowires of the present invention comprises an anodization process for forming an anodized film having pores on the surface of a valve metal substrate, a metal filling process for filling the pores with metal, an isolation process for isolating the filled metal from the anodized film and the valve metal substrate, and a crushing process for crushing the isolated metal (hereinafter also abbreviated as “isolated metal”) to obtain metal nanowires.
  • a crushing process is carried out after isolating the filled metal from the anodized film and the valve metal substrate (after the isolation process), thereby making it possible to obtain metal nanowires that have high bonding strength when bonded.
  • the reason why metal nanowires having high bonding strength when bonded could be obtained is not clear in detail, but is presumed to be as follows.
  • the surface of a valve metal substrate 1 is anodized to form an anodized film 3 having pores (micropores) 2 on the surface of the valve metal substrate 1.
  • the pores 2 are filled with a metal 4.
  • the isolation step the filled metal 4 is isolated from the anodized film 3 and the valve metal substrate 1.
  • the embodiment shown in Fig. 1D shows the state in which the isolated metal 5 obtained in the isolation step is collected (a part of the isolated metal is adhered).
  • metal nanowires 10 in which the isolated metal 5 is crushed can be obtained.
  • the valve metal substrate used in the manufacturing method of the present invention is not particularly limited as long as it is a substrate containing a valve metal.
  • the valve metal include aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth, antimony, etc.
  • aluminum is preferable because it has good dimensional stability and is relatively inexpensive. Therefore, in the manufacturing method of the present invention, it is preferable to use a base material containing aluminum (hereinafter, abbreviated as "aluminum base material”) as the valve metal base material.
  • the aluminum substrate is not particularly limited, and specific examples include pure aluminum plates; alloy plates containing aluminum as the main component and trace amounts of other elements; substrates in which high-purity aluminum is vapor-deposited onto low-purity aluminum (e.g., recycled materials); substrates in which the surfaces of silicon wafers, quartz, glass, etc. are coated with high-purity aluminum by methods such as vapor deposition and sputtering; and resin substrates laminated with aluminum.
  • the surface of the valve metal substrate that is anodized in the anodizing process described below preferably has a valve metal purity of 99.5% by mass or more, more preferably 99.9% by mass or more, and even more preferably 99.99% by mass or more.
  • the valve metal purity is within the above range, the arrangement of the through passages is sufficiently regular.
  • the surface of the valve metal base material that is to be anodized in the anodizing step described below is preferably previously subjected to a heat treatment, a degreasing treatment and a mirror finish treatment.
  • the heat treatment, degreasing treatment and mirror finish treatment can be the same as those described in paragraphs [0044] to [0054] of JP-A-2008-270158.
  • the anodizing step is a step of forming a porous anodized film on the surface of the valve metal base by subjecting the surface of the valve metal base to an anodizing treatment.
  • the anodizing treatment carried out in the anodizing step can be a conventionally known method, but it is preferable to use a self-ordering method or a constant voltage treatment because this makes it possible to isolate the filled metal with less variation in diameter in the isolation step described below.
  • the self-ordering method of the anodizing treatment and the constant voltage treatment can be the same as the treatments described in paragraphs [0056] to [0108] and in FIG. 3 of JP-A-2008-270158.
  • the anodizing treatment can be carried out, for example, by passing a current through a valve metal substrate as an anode in a solution having an acid concentration of 1 to 10% by mass.
  • the solution used in the anodizing treatment is preferably an acid solution, more preferably sulfuric acid, phosphoric acid, chromic acid, oxalic acid, sulfamic acid, benzenesulfonic acid, amidosulfonic acid, glycolic acid, tartaric acid, malic acid, citric acid, etc., and among these, sulfuric acid, phosphoric acid, and oxalic acid are further preferable, and oxalic acid is particularly preferable.
  • These acids can be used alone or in combination of two or more kinds.
  • the conditions for the anodizing treatment vary depending on the electrolyte used and cannot be determined in general, but generally, the electrolyte concentration is preferably 0.1 to 20% by mass, the solution temperature is -10 to 30°C, the current density is 0.01 to 20 A/ dm2 , the voltage is 3 to 300 V, and the electrolysis time is 0.5 to 30 hours, more preferably the electrolyte concentration is 0.5 to 15% by mass, the solution temperature is -5 to 25°C, the current density is 0.05 to 15 A/ dm2 , the voltage is 5 to 250 V, and the electrolysis time is 1 to 25 hours, and even more preferably the electrolyte concentration is 1 to 10% by mass, the solution temperature is 0 to 20°C, the current density is 0.1 to 10 A/ dm2 , the voltage is 10 to 200 V, and the electrolysis time is 2 to 20 hours.
  • the anodizing treatment time is preferably 0.5 minutes to 16 hours, more preferably 1 minute to 12 hours, and even more preferably 2 minutes to 8 hours.
  • the thickness of the anodized film formed by the anodization process is not particularly limited, but from the viewpoint of adjusting the length of the metal nanowires, it is preferably 0.3 to 300 ⁇ m, more preferably 0.5 to 120 ⁇ m, and even more preferably 0.5 to 100 ⁇ m.
  • the thickness of the anodic oxide film can be calculated as the average value of measurements taken at 10 points by cutting the anodic oxide film in the thickness direction with a focused ion beam (FIB), taking surface photographs (magnification: 50,000 times) of the cross section with a field emission scanning electron microscope (FE-SEM).
  • the density of the pores formed by the anodization process is not particularly limited, but is preferably 2 million pores/ mm2 or more, more preferably 10 million pores/ mm2 or more, even more preferably 50 million pores/mm2 or more, and particularly preferably 100 million pores/ mm2 or more.
  • the density of the pores can be measured and calculated by the method described in paragraphs [0168] and [0169] of JP-A-2008-270158.
  • the average opening diameter of the pores formed by the above-mentioned anodization process is not particularly limited, but from the viewpoint of adjusting the diameter of the metal nanowires, it is preferably 5 to 500 nm, more preferably 20 to 400 nm, even more preferably 40 to 200 nm, and particularly preferably 50 to 100 nm.
  • the average opening diameter of the pores can be calculated as the average value of measurements taken at 50 points on a surface photograph (magnification: 50,000 times) taken with an FE-SEM.
  • the metal filling step is a step of filling the inside of the pores with a metal after the anodization step.
  • the above metal is preferably a material having an electrical resistivity of 10 3 ⁇ cm or less, and specific examples thereof include gold (Au), silver (Ag), copper (Cu), aluminum (Al), titanium (Ti), nickel (Ni), cobalt (Co), etc.
  • Au gold
  • silver Au
  • Cu copper
  • Al aluminum
  • Ti titanium
  • Ni nickel
  • Co cobalt
  • Examples of the method for filling the interior of the pores with the metal include the methods described in paragraphs [0123] to [0126] and [FIG. 4] of JP-A-2008-270158.
  • the metal filling step includes a plating step, because this makes it difficult for the produced metal nanowires to contain hollow portions.
  • an electrolytic plating method as a method for filling the inside of the pores with the metal, and for example, an electrolytic plating method or an electroless plating method can be used.
  • an electrolytic plating method or an electroless plating method can be used.
  • the manufacturing method of the present invention when filling metal by electrolytic plating, it is necessary to provide a rest period during pulse electrolysis or constant potential electrolysis.
  • the rest period must be 10 seconds or more, and is preferably 30 to 60 seconds. It is also preferable to apply ultrasonic waves to promote stirring of the electrolyte.
  • the electrolysis voltage is usually 20 V or less, and preferably 10 V or less, but it is preferable to measure the deposition potential of the target metal in the electrolyte solution to be used in advance and perform constant-potential electrolysis at a potential within +1 V of that potential.
  • a device that can also be used with cyclic voltammetry, and a potentiostat device manufactured by Solartron, BAS, Hokuto Denko, IVIUM, etc. can be used.
  • the plating solution a conventionally known plating solution can be used. Specifically, when copper is precipitated, an aqueous solution of copper sulfate is generally used, and the concentration of the copper sulfate is preferably 1 to 300 g/L, and more preferably 100 to 200 g/L. Precipitation can be promoted by adding hydrochloric acid to the electrolyte. In this case, the concentration of hydrochloric acid is preferably 10 to 20 g/L. When gold is to be deposited, it is preferable to use a sulfuric acid solution of gold tetrachloride and to perform plating by AC electrolysis.
  • the electrolytic plating method a treatment method in which AC electrolytic plating and DC electrolytic plating are combined in this order.
  • a voltage is applied modulated into a sine wave at a predetermined frequency.
  • the waveform of the voltage modulation is not limited to a sine wave, and may be, for example, a square wave, a triangular wave, a sawtooth wave, or an inverse sawtooth wave.
  • the DC electrolytic plating method can appropriately use the treatment methods in the electrolytic plating method described above.
  • the metal filling step is a process that is performed on the region from the bottom of the hole to halfway through the opening, out of the entire region from the bottom of the hole to the opening.
  • the isolation step is a step of isolating the filled metal from the anodized film and the valve metal substrate after the metal filling step.
  • the method of isolating the filled metal from the anodized film and the valve metal base material is not particularly limited, and for example, the method of removing (for example, dissolving, peeling, etc.) the anodized film and the valve metal base material and isolating the filled metal can be preferably mentioned.
  • the embodiment after the above-mentioned isolation process also includes, for example, the embodiment in which the filled metal is dispersed in an isolated state in the treatment liquid used in the dissolution process (dissolution treatment) described later.
  • the method for removing the anodic oxide film and the valve metal substrate is not particularly limited, and may be, for example, by polishing.
  • the isolation process includes a dissolution process, that is, that at least a portion of the anodic oxide film and the valve metal substrate is removed by a dissolution process.
  • the isolation process includes a one-step removal process of removing the anodic oxide film and the valve metal substrate, and it is more preferable that the removal of the anodic oxide film is a process in which the anodic oxide film is removed by a dissolution treatment.
  • the isolation step may include a two-step removal step of removing the valve metal base material and then removing the anodic oxide film, and in this case, it is more preferable that both of the two removal steps are performed by dissolution treatment.
  • the removal of the valve metal substrate is preferably carried out by a dissolution treatment using a treatment liquid which does not easily dissolve the anodized film but easily dissolves the valve metal.
  • the dissolution rate of such a treatment solution for valve metal is preferably 1 ⁇ m/min or more, more preferably 3 ⁇ m/min or more, and even more preferably 5 ⁇ m/min or more.
  • the dissolution rate of anodized film is preferably 0.1 nm/min or less, more preferably 0.05 nm/min or less, and even more preferably 0.01 nm/min or less.
  • the treatment liquid preferably contains at least one metal compound having a lower ionization tendency than the valve metal, and has a pH of 4 or less or 8 or more, more preferably a pH of 3 or less or 9 or more, and even more preferably a pH of 2 or less or 10 or more.
  • Such a treatment liquid is preferably based on an acid or alkaline aqueous solution and contains, for example, compounds of manganese, zinc, chromium, iron, cadmium, cobalt, nickel, tin, lead, antimony, bismuth, copper, mercury, silver, palladium, platinum, and gold (e.g., chloroplatinic acid), their fluorides, or their chlorides.
  • an acid aqueous solution base is preferred, and a chloride blend is preferred.
  • a treatment solution in which mercury chloride is blended into an aqueous hydrochloric acid solution (hydrochloric acid/mercury chloride) and a treatment solution in which copper chloride is blended into an aqueous hydrochloric acid solution (hydrochloric acid/copper chloride) are preferred from the viewpoint of treatment latitude.
  • the composition of such a treatment liquid is not particularly limited, and for example, a bromine/methanol mixture, a bromine/ethanol mixture, aqua regia, etc. can be used.
  • the acid or alkali concentration of such a treatment solution is preferably from 0.01 to 10 mol/L, and more preferably from 0.05 to 5 mol/L.
  • the processing temperature when using such a processing solution is preferably from -10°C to 80°C, and more preferably from 0°C to 60°C.
  • the valve metal substrate is removed by contacting the valve metal substrate after the metal filling step with the treatment liquid described above.
  • the contact method is not particularly limited, and examples include the immersion method and the spray method. Of these, the immersion method is preferred.
  • the contact time is preferably 10 seconds to 5 hours, and more preferably 1 minute to 3 hours.
  • the anodic oxide film can be removed using a solvent that does not dissolve the metal filled in the pores but selectively dissolves the anodic oxide film, and either an aqueous alkaline solution or an aqueous acid solution can be used.
  • an alkaline aqueous solution When an alkaline aqueous solution is used, it is preferable to use an aqueous solution of at least one alkali selected from the group consisting of sodium hydroxide, potassium hydroxide, and lithium hydroxide, and it is more preferable to use an aqueous solution of potassium hydroxide.
  • the concentration of the alkaline aqueous solution is preferably 1 to 30 mass %.
  • the temperature of the alkaline aqueous solution is preferably 10 to 60°C, more preferably 20 to 60°C, and even more preferably 30 to 60°C.
  • an aqueous acid solution it is preferable to use an aqueous solution of an inorganic acid such as chromic acid, sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid, oxalic acid, or a mixture thereof, and it is more preferable to use an aqueous solution of chromic acid.
  • the concentration of the aqueous acid solution is preferably 1 to 30 mass %.
  • the temperature of the aqueous acid solution is preferably 15 to 80°C, more preferably 20 to 60°C, and even more preferably 30 to 50°C.
  • the anodic oxide film is removed by contacting the above-mentioned alkaline aqueous solution and acid aqueous solution after the metal filling step (preferably after the valve metal substrate is removed).
  • the contacting method is not particularly limited, and examples include immersion and spraying. Of these, the immersion method is preferred.
  • the immersion time in the alkaline aqueous solution and acid aqueous solution is preferably 1 to 120 minutes, more preferably 2 to 90 minutes, even more preferably 3 to 60 minutes, and particularly preferably 3 to 30 minutes. Of these, 3 to 20 minutes is preferred, and 3 to 10 minutes is more preferred.
  • the crushing step is a step of crushing the isolated metal after the isolation step.
  • the method for crushing the isolated metal is not particularly limited, but a suitable example is a method in which the isolated metal is crushed by applying an impact to the isolated metal in a liquid.
  • the liquid (solvent) used for disintegration is not particularly limited as long as it does not alter or dissolve the isolated metal, and examples thereof include water, ethanol, methanol, acetone, methyl ethyl ketone, butanol, ethyl acetate, butyl acetate, tetrahydrofuran, toluene, dimethylformamide, cyclohexane, cyclohexanone, etc. Among these, water is preferred from the viewpoint of safety.
  • the crushing step is preferably carried out in water or in an aqueous solution having an alkali or acid concentration of less than 1 mass %, from the viewpoint of producing metal nanowires having higher bonding strength when bonded.
  • the crushing treatment include a crushing treatment using cavitation and a crushing treatment using ceramic balls, and devices such as an ultrasonic cleaner, an ultrasonic homogenizer, a jet mill, a wet type micronizer, etc.
  • a crushing treatment using cavitation or a crushing treatment using ceramic balls is preferred, and a crushing treatment using cavitation is more preferred.
  • the concentration of the isolated metal in the liquid during pressure disintegration in the liquid is preferably 0.1 to 50 mass % because this makes the treatment uniform and improves productivity. Furthermore, the concentration of the isolated metal in the liquid when the pressure is released in the liquid is more preferably 0.5 to 30 mass%, and even more preferably 1 to 10 mass%, because this allows for the production of metal nanowires having higher bonding strength upon bonding.
  • the manufacturing method of the present invention preferably further includes a drying step for drying the isolated metal between the isolation step and the crushing step, since this makes apparent the effect of the present invention, that is, the ability to obtain metal nanowires having high bonding strength when bonded.
  • the method for drying the isolated metal is not particularly limited, but after removing the anodized film and the valve metal substrate, the isolated metal can be recovered and dried by performing a separation operation such as filtration using a filter or centrifugation.
  • the manufacturing method of the present invention further includes a step of forming a protective layer containing a corrosion inhibitor on the isolated metal after the isolation step (or after the drying step if the drying step is included).
  • the corrosion inhibitor is not particularly limited, and any known corrosion inhibitor can be used.
  • the corrosion inhibitor include compounds containing at least one of a nitrogen atom, an oxygen atom, and a sulfur atom.
  • the corrosion inhibitor is preferably a heterocyclic compound containing at least one of a nitrogen atom and an oxygen atom, more preferably a compound containing a five-membered ring structure containing one or more nitrogen atoms, and particularly preferably at least one compound selected from the group consisting of a compound containing a triazole structure, a compound containing a benzimidazole structure, and a compound containing a thiadiazole structure.
  • the five-membered ring structure containing one or more nitrogen atoms may be a monocyclic structure or a partial structure constituting a condensed ring.
  • the corrosion inhibitor is preferably a compound containing at least one of a polar group-containing acid and a polar group-containing base, because this makes it easier for the corrosion inhibitor to be adsorbed onto the surface of the isolated metal.
  • the polar group contained in the polar group-containing acid and the polar group-containing base include a carboxylic acid group (carboxy group), a sulfonic acid group (sulfo group), a phosphonic acid group, a phosphoric acid group, a primary to quaternary ammonium base, a carboxylate group, a sulfonate group, a phosphonate group, and a phosphate group.
  • the corrosion inhibitor is preferably a compound containing a carboxy group, because it bonds with metal ions to form complex ions, which makes it easier to protect the surface of the isolated metal.
  • corrosion inhibitors include imidazole, benzimidazole, 1,2,4-triazole, benzotriazole (BTA), tolyltriazole (TTA), butylbenzyltriazole, alkyldithiothiadiazole, alkylthiol, 2-aminopyrimidine, 5,6-dimethylbenzimidazole, 2-amino-5-mercapto-1,3,4-thiadiazole, 2,5-dimercapto-1,3,4-thiadiazole (DMTDA), 2-mercaptopyrimidine, 2-mercaptobenzoxazole, 2-mercaptobenzothiazole (MBT), 2-mercaptobenzimidazole, etc.
  • corrosion inhibitors include aliphatic carboxylic acids such as acetic acid, propionic acid, palmitic acid, stearic acid, lauric acid, arachidic acid, terephthalic acid, and oleic acid; carboxylic acids such as glycolic acid, lactic acid, oxalic acid, malic acid, tartaric acid, and citric acid; aminopolycarboxylic acids such as ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), iminodiacetic acid (IDA), ethylenediaminediacetic acid (EDDA), and ethylene glycol diethyl ether diaminetetraacetic acid (GEDA); uric acid; and gallic acid.
  • carboxylic acids such as glycolic acid, lactic acid, oxalic acid, malic acid, tartaric acid, and citric acid
  • aminopolycarboxylic acids such as ethylenediaminetetraacetic acid (EDTA), n
  • the corrosion inhibitors may be used alone or in appropriate combination of two or more kinds.
  • the corrosion inhibitor preferably contains a compound containing a nitrogen atom (nitrogen-containing compound), more preferably is a nitrogen-containing compound, and further preferably is a heterocyclic compound containing at least one of a nitrogen atom and a sulfur atom.
  • the method for forming such a protective layer containing a corrosion inhibitor is not particularly limited, and examples include a method in which the isolated metal recovered in the drying process is added to an aqueous solution containing a corrosion inhibitor and stirred; a method in which the corrosion inhibitor is added to a washing solvent that washes the isolated metal recovered in the drying process; etc.
  • the manufacturing method of the present invention further includes a step of reducing or removing the surface oxide layer of the isolated metal between the isolation step and the crushing step (or before the drying step, if the drying step is included).
  • the reduction or removal step may be, for example, a step of carrying out an immersion treatment using an aqueous alkaline solution or an aqueous acid solution as described above in the removal treatment of the anodic oxide film.
  • compositions The metal nanowires produced by the production method of the present invention are preferably used as a composition containing the metal nanowires, and more preferably used as a composition in a paste state.
  • composition of the present invention the composition containing the metal nanowires produced by the production method of the present invention will be formally abbreviated as the "composition of the present invention.”
  • the content (concentration) of the metal nanowires in the composition of the present invention is not particularly limited, but it is preferably 30 to 99 mass %, and more preferably 50 to 90 mass %, relative to the total mass of the composition of the present invention, because this maintains good dispersion stability over time and also provides good uniformity when diluted.
  • the optional solvent contained in the composition of the present invention is mainly an organic solvent.
  • an organic solvent that is miscible with water water can be used in combination with the organic solvent in a proportion of 20% by volume or less.
  • an alcohol-based compound having a boiling point of 50° C. to 250° C., more preferably 55° C. to 200° C. is suitably used.
  • the alcohol-based compound is not particularly limited and can be appropriately selected depending on the purpose. Specific examples thereof include polyethylene glycol, polypropylene glycol, alkylene glycol, glycerol, etc.
  • those having a small number of carbon atoms such as ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and 2,3-butanediol, which have low viscosity at room temperature, are preferred, but those having a large number of carbon atoms, such as pentanediol, hexanediol, octanediol, and polyethylene glycol, can also be used. Of these, the most preferred solvent is diethylene glycol.
  • surfactant It is preferable to use a surfactant in the composition of the present invention because this provides better dispersion stability.
  • the surfactant include nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, and fluorine-based surfactants. These surfactants may be used alone or in combination of two or more.
  • the nonionic surfactant is not particularly limited, and any of the conventionally known surfactants can be used.
  • polyoxyethylene alkyl ethers polyoxyethylene alkylphenyl ethers, polyoxyethylene polystyrylphenyl ethers, polyoxyethylene polyoxypropylene alkyl ethers, glycerin fatty acid partial esters, sorbitan fatty acid partial esters, pentaerythritol fatty acid partial esters, propylene glycol mono fatty acid esters, sucrose fatty acid partial esters, polyoxyethylene sorbitan fatty acid partial esters, polyoxyethylene sorbitol fatty acid partial esters, polyethylene glycol fatty acid esters, polyglycerin fatty acid partial esters, polyoxyethylated castor oils, polyoxyethylene glycerin fatty acid partial esters, fatty acid diethanolamides, N,N-bis-2-hydroxyalkylamines, polyoxyethylene alkylamines, triethanolamine fatty acid
  • the anionic surfactant is not particularly limited, and any of the conventionally known surfactants can be used.
  • fatty acid salts, abietic acid salts, hydroxyalkanesulfonates, alkanesulfonates, dialkylsulfosuccinate salts linear alkylbenzenesulfonates, branched alkylbenzenesulfonates, alkylnaphthalenesulfonates, alkylphenoxypolyoxyethylenepropylsulfonates, polyoxyethylenealkylsulfophenylether salts, N-methyl-N-oleyltaurine sodium salt, N-alkylsulfosuccinic acid monoamide disodium salt, petroleum sulfonates, sulfated beef tallow oil, sulfate ester salts of fatty acid alkyl esters, alkane sulfonates, dialkylsulfosuccinate salts, alkylsulfon
  • alkyl sulfate salts examples include polyoxyethylene alkyl ether sulfate salts, fatty acid monoglyceride sulfate salts, polyoxyethylene alkyl phenyl ether sulfate salts, polyoxyethylene styryl phenyl ether sulfate salts, alkyl phosphate salts, polyoxyethylene alkyl ether phosphate salts, polyoxyethylene alkyl phenyl ether phosphate salts, partially saponified products of styrene/maleic anhydride copolymers, partially saponified products of olefin/maleic anhydride copolymers, and naphthalenesulfonate-formaldehyde condensates.
  • the cationic surfactant is not particularly limited, and any conventionally known surfactant can be used. Examples include alkylamine salts, quaternary ammonium salts, polyoxyethylene alkylamine salts, and polyethylene polyamine derivatives.
  • amphoteric surfactant is not particularly limited, and any conventionally known surfactant can be used. Examples include carboxybetaines, aminocarboxylic acids, sulfobetaines, aminosulfuric acid esters, and imitazolines.
  • polyoxyethylene can be read as “polyoxyalkylene” such as polyoxymethylene, polyoxypropylene, polyoxybutylene, etc., and these surfactants can also be used in the present invention.
  • preferred surfactants include fluorine-based surfactants containing a perfluoroalkyl group in the molecule.
  • fluorine-based surfactants include anionic types such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and perfluoroalkyl phosphates; amphoteric types such as perfluoroalkyl betaines; cationic types such as perfluoroalkyl trimethyl ammonium salts; and nonionic types such as perfluoroalkyl amine oxides, perfluoroalkyl ethylene oxide adducts, oligomers containing a perfluoroalkyl group and a hydrophilic group, oligomers containing a perfluoroalkyl group and a lipophilic group, oligomers containing a perfluoroalkyl group, a hydrophilic group, and a lipophilic group, and urethanes containing a
  • the HLB value is a value that indicates the degree of affinity of a surfactant for water and oil (organic compounds insoluble in water).
  • the HLB value ranges from 0 to 20, with the closer to 0 the higher the lipophilicity and the closer to 20 the higher the hydrophilicity.
  • these surfactants may be used alone or in combination of two or more.
  • the content of these surfactants is preferably 0.001 to 10 mass %, and more preferably 0.01 to 5 mass %, based on the total mass of the metal nanowires.
  • the composition of the present invention can use a water-soluble dispersant such as a water-soluble organic molecule having a hydroxyl group, a carboxyl group, a sulfone group, a phosphate group, an amino group, an SH group, or the like at its terminal, for example, succinic acid, polyvinyl alcohol (PVA), or polyvinylpyrrole (PVP).
  • a water-soluble dispersant such as a water-soluble organic molecule having a hydroxyl group, a carboxyl group, a sulfone group, a phosphate group, an amino group, an SH group, or the like at its terminal, for example, succinic acid, polyvinyl alcohol (PVA), or polyvinylpyrrole (PVP).
  • composition of the present invention may further contain conductive particles other than the metal nanowires.
  • the conductive particles preferably contain a metal, and more preferably contain at least one metal selected from the group consisting of gold, silver, copper, aluminum, nickel, zinc and cobalt.
  • the conductive particles may also contain one or more conductive components other than metals.
  • the shape of the conductive particles is not particularly limited, and they may be either solid or hollow.
  • the average major axis of the minimum enclosing ellipsoid of the conductive particle is preferably 0.01 ⁇ m or more and 50 ⁇ m or less.
  • the average major axis of the smallest enclosing ellipsoid of the conductive particle is preferably 1 to 10 times the average minor axis.
  • the minimum enclosing ellipsoid refers to the ellipsoid that has the smallest volume among the ellipsoids that contain the conductive particles therein, and includes an ellipsoid whose major axis and minor axis are the same (i.e., a sphere).
  • the average major axis of the minimum enclosing ellipsoid can be obtained by observing the cross section of the layer formed using the dispersion in the thickness direction with a microscope (e.g., electron microscope), measuring the major axis of 100 arbitrary fine particles, and calculating and averaging them.
  • the average minor axis of the minimum enclosing ellipsoid can be obtained by observing the cross section of the layer formed using the dispersion in the thickness direction with a microscope (e.g., electron microscope), measuring the minor axis of 100 arbitrary fine particles, and calculating and averaging them.
  • the median diameter (D50) described later refers to the median diameter of the conductive particles when the volume of the conductive particles is approximated to that of a sphere, and can be determined by a laser diffraction/scattering method or a dynamic light scattering method.
  • the content of the conductive particles is not particularly limited, but is preferably 5 to 70 parts by mass, and more preferably 10 to 45 parts by mass, per 100 parts by mass of the metal nanowires.
  • the composition of the present invention can be suitably used as a conductive ink for forming a circuit pattern on a wiring substrate.
  • the content (concentration) of the metal nanowires in the composition of the present invention is preferably 10 to 30 mass %, and more preferably 15 to 20 mass %, relative to the total mass of the composition of the present invention, because circuit patterns can be printed using an inkjet system.
  • composition of the present invention described above can be suitably used to form a conductive bonding material.
  • conductive bonding material in the present invention is a concept that includes not only a film formed on the entire surface of a desired substrate, but also the above-mentioned circuit pattern and the like.
  • the substrate on which the conductive film is formed and the method for forming the conductive film are not particularly limited, and for example, the substrate and the method for forming the conductive film described in JP-A-2010-84173 can be used.
  • the conductive bonding material of the present invention can be suitably used as a conductive bonding material for use in, for example, semiconductor bonding members, touch panels, electrode bonding materials for displays, electromagnetic wave shields, sintering materials, electrode materials for thin-layer ceramic capacitors, and various other devices.
  • Example 1 ⁇ Preparation of Aluminum Substrate> A molten metal was prepared using an aluminum alloy containing 0.06 mass% Si, 0.30 mass% Fe, 0.005 mass% Cu, 0.001 mass% Mn, 0.001 mass% Mg, 0.001 mass% Zn, 0.001 mass% Ti, and the remainder being Al and unavoidable impurities. The molten metal was treated and filtered, and an ingot having a thickness of 500 mm and a width of 1,200 mm was produced by a DC (Direct Chill) casting method. Next, the surface was scraped off by an average thickness of 10 mm using a facing machine, and then the plate was soaked at 550°C for about 5 hours.
  • DC Direct Chill
  • the plate When the temperature was lowered to 400°C, the plate was rolled into a 2.7 mm thick plate using a hot rolling machine. Further, the sheet was heat-treated at 500° C. using a continuous annealing machine, and then cold-rolled to a thickness of 1.0 mm to obtain an aluminum substrate of JIS (Japanese Industrial Standards) 1050 material. The aluminum substrate was formed into a wafer having a diameter of 200 mm (8 inches) and then subjected to the following treatments.
  • JIS Japanese Industrial Standards
  • Electrolytic polishing treatment The above-mentioned aluminum substrate was subjected to electrolytic polishing treatment using an electrolytic polishing solution having the following composition under conditions of a voltage of 25 V, a solution temperature of 65° C., and a solution flow rate of 3.0 m/min.
  • the cathode was a carbon electrode
  • the power source was GP0110-30R (manufactured by Takasago Manufacturing Co., Ltd.)
  • the flow rate of the electrolyte was measured using a vortex flow monitor FLM22-10PCW (manufactured by AS ONE Corporation).
  • (Electrolytic polishing solution composition) 85% by weight phosphoric acid (reagent manufactured by Wako Pure Chemical Industries, Ltd.) 660 mL ⁇ 160mL of pure water ⁇ 150mL sulfuric acid ⁇ 30mL ethylene glycol
  • the aluminum substrate after the electrolytic polishing treatment was subjected to anodizing treatment by a self-ordering method according to the procedure described in JP-A-2007-204802.
  • the aluminum substrate after electrolytic polishing was subjected to a pre-anodizing treatment for 5 hours in an electrolytic solution of 0.50 mol/L oxalic acid under conditions of a voltage of 40 V, a solution temperature of 16° C., and a solution flow rate of 3.0 m/min.
  • the aluminum substrate after the pre-anodizing treatment was subjected to a coating removal treatment by immersing it in a mixed aqueous solution of 0.2 mol/L chromic anhydride and 0.6 mol/L phosphoric acid (liquid temperature: 50° C.) for 12 hours. Thereafter, re-anodization was performed for 5 hours in an electrolyte of 0.50 mol/L oxalic acid under conditions of a voltage of 40 V, a liquid temperature of 16° C., and a liquid flow rate of 3.0 m/min, to obtain an anodized film with a thickness of 40 ⁇ m.
  • the cathode was a stainless steel electrode, and the power source was GP0110-30R (manufactured by Takasago Manufacturing Co., Ltd.).
  • the cooling device was NeoCool BD36 (manufactured by Yamato Scientific Co., Ltd.), and the stirring and heating device was Pair Stirrer PS-100 (manufactured by EYELA Tokyo Rikakikai Co., Ltd.).
  • the flow rate of the electrolyte was measured using a vortex flow monitor FLM22-10PCW (manufactured by AS ONE Corporation).
  • the surface of the anodized film after the pores were filled with metal was observed with an FE-SEM to determine whether 1,000 pores were sealed with metal.
  • the sealing rate (number of sealed pores/1,000) was calculated to be 96%.
  • the anodized film was cut in the thickness direction using an FIB, and the cross section was photographed with an FE-SEM (magnification 50,000x) to check the inside of the holes. It was found that the filling height from the bottom of the sealed holes was 35 ⁇ m.
  • ⁇ Isolation step> The filled metal was isolated from the anodized film and the aluminum base material by immersing the aluminum base material in an aqueous potassium hydroxide solution (concentration: 5 mol/L) at 60° C. for 300 seconds, to obtain an isolated metal. Specifically, the anodized film was dissolved by immersing the aluminum base material in an aqueous potassium hydroxide solution (concentration: 5 mol/L) at 60° C. for 300 seconds, and the filled metal was isolated by peeling off the aluminum base material at the same time as the anodized film was dissolved (after 300 seconds had elapsed).
  • Example 1 ⁇ Cleaning/Protective Layer Forming Step/Reduction or Removal Step> Next, the isolated metal recovered on the membrane was washed for 1 minute using the washing solvent shown below. In Example 1, since a corrosion inhibitor was added to the washing solvent, a protective layer was formed at the same time as washing. In Example 1, since citric acid was used as the corrosion inhibitor, the surface oxide layer of the isolated metal was also removed at the same time as the protective layer was formed. The isolated metals on the membrane were then collected. (Washing Solvent) An aqueous solution containing 1% by weight of citric acid
  • Example 2 The steps from “preparation of aluminum substrate” to “cleaning/protective layer formation step/reduction or removal step” in Example 1 were repeated twice, and twice the amount of isolated metal as in Example 1 was recovered. Thereafter, metal nanowires were produced in the same manner as in Example 1, except that the concentration of the isolated metal during the crushing treatment was changed to 40 mass %.
  • Example 3 Metal nanowires were produced in the same manner as in Example 1, except that the concentration of the isolated metal during the crushing treatment was changed to 0.5 mass %.
  • Example 4 Metal nanowires were produced in the same manner as in Example 1, except that the washing solvent in the washing/protective layer forming step/reduction or removal step was changed to water. That is, in Example 4, no protective layer was formed.
  • Example 5 Metal nanowires were produced in the same manner as in Example 1, except that the cleaning solvent in the cleaning/protective layer formation step/reduction or removal step was changed to an aqueous solution containing 1 mass % each of citric acid and benzotriazole.
  • Example 6 Metal nanowires were produced in the same manner as in Example 1, except that in the isolation step, the aluminum substrate was dissolved and removed by immersing the aluminum substrate in a 0.5 mass % Cu-12% HCl aqueous solution at 10°C for 1 hour before immersing the aluminum substrate in the potassium hydroxide aqueous solution.
  • Example 7 Metal nanowires were produced in the same manner as in Example 1, except that the liquid used in the crushing step was changed from water to a 1 mass % aqueous citric acid solution.
  • Example 8 Metal nanowires were produced in the same manner as in Example 1, except that the type of metal used in the metal filling step was changed to Ni.
  • Example 9 Metal nanowires were produced in the same manner as in Example 1, except that electroless Au plating was performed after the crushing step.
  • Example 10 Metal nanowires were produced in the same manner as in Example 1, except that the cleaning solvent in the cleaning/protective layer formation step/reduction or removal step was changed to an aqueous solution containing 1 mass % each of citric acid and 2-mercaptobenzothiazole.
  • Example 11 Metal nanowires were produced in the same manner as in Example 1, except that the metal filling height in the metal filling step was set to 15 ⁇ m.
  • Example 12 Metal nanowires were produced in the same manner as in Example 1, except that the surface oxide layer of the metal nanowires was reduced or removed by immersing them in a 10% by mass aqueous solution of sulfuric acid at 35°C for 15 seconds prior to the cleaning/protective layer formation process/reduction or removal process.
  • the prepared composition was applied to a Cu plate (10 mm ⁇ 10 mm ⁇ 0.5 mm) with a squeegee using a metal mask (opening: 1 ⁇ 1 mm ⁇ 0.2 mm), and a Cu plate (5 mm ⁇ 5 mm ⁇ 0.5 mm) was placed on the applied composition. Thereafter, using a bonding device (WP-100, manufactured by PMT), the atmosphere inside the device was replaced with reducing gas (N2: 85%, formic acid: 15%), and then the pieces were bonded by heating and compression at 250°C, 1 minute, and 5 MPa.
  • WP-100 manufactured by PMT
  • Example 1 shows that when the crushing step is not carried out, the bonding strength of the produced metal nanowires (isolated metal) is low (Comparative Example 1). In contrast, it was found that when the crushing step was not carried out, the bonding strength of the produced metal nanowires was high (Examples 1 to 12). In particular, a comparison of Examples 1 to 3 reveals that when the concentration of the isolated metal during the crushing treatment is 0.5 to 30 mass %, metal nanowires having higher bonding strength when bonded can be produced. Furthermore, a comparison between Example 1 and Example 7 revealed that disintegration in an aqueous solution with an alkali or acid concentration of less than 1 mass % made it possible to produce metal nanowires with higher bonding strength when bonded.
  • Valve metal substrate Porous (micropore) 3 Anodic oxide film 4 Metal 5 Isolated metal 10 Metal nanowire

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Abstract

La présente invention concerne un procédé de production d'un nanofil métallique doté d'une force d'assemblage élevée au moment de l'assemblage. Le procédé de production de nanofil métallique selon l'invention comprend : une étape d'anodisation pour former un film d'anodisation comportant des pores sur une surface d'un substrat métallique de valve ; une étape de remplissage métallique pour déverser un métal dans les pores ; une étape d'isolation pour isoler le métal utilisé pour le remplissage du film d'anodisation et du substrat métallique de valve ; et une étape de broyage pour broyer le métal isolé afin d'obtenir un nanofil métallique.
PCT/JP2023/030248 2022-09-30 2023-08-23 Procédé de production de nanofil métallique WO2024070341A1 (fr)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20050274833A1 (en) * 2002-01-03 2005-12-15 Tapesh Yadav Shape engineering of nanoparticles
CN101886283A (zh) * 2010-06-24 2010-11-17 浙江大学 一种磁性编码纳米线的制备方法及其用途
WO2012147964A1 (fr) * 2011-04-28 2012-11-01 富士フイルム株式会社 Liquide de dispersion contenant des nanofils métalliques, et film conducteur
US20190085478A1 (en) * 2015-11-30 2019-03-21 The Regents Of The University Of California Low-density interconnected ionic material foams and methods of manufacture
JP2020046506A (ja) * 2018-09-18 2020-03-26 住友金属鉱山株式会社 金属ナノロッド含有樹脂、近赤外線遮蔽レンズ、近赤外線遮蔽眼鏡、保護具、近赤外線遮蔽窓材、近赤外線遮蔽器具、近赤外線遮蔽フィルム、近赤外線遮蔽ガラス、及び金属ナノロッド集合体の製造方法

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20050274833A1 (en) * 2002-01-03 2005-12-15 Tapesh Yadav Shape engineering of nanoparticles
CN101886283A (zh) * 2010-06-24 2010-11-17 浙江大学 一种磁性编码纳米线的制备方法及其用途
WO2012147964A1 (fr) * 2011-04-28 2012-11-01 富士フイルム株式会社 Liquide de dispersion contenant des nanofils métalliques, et film conducteur
US20190085478A1 (en) * 2015-11-30 2019-03-21 The Regents Of The University Of California Low-density interconnected ionic material foams and methods of manufacture
JP2020046506A (ja) * 2018-09-18 2020-03-26 住友金属鉱山株式会社 金属ナノロッド含有樹脂、近赤外線遮蔽レンズ、近赤外線遮蔽眼鏡、保護具、近赤外線遮蔽窓材、近赤外線遮蔽器具、近赤外線遮蔽フィルム、近赤外線遮蔽ガラス、及び金属ナノロッド集合体の製造方法

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