Base metal plating film

Abstract

To provide a base metal plating bath useful for manufacturing a base metal plating film with high glossiness and oxidation resistance.SOLUTION: A base metal plating bath contains base metal ions and hydrophilic nano-diamond particles. The concentration of hydrophilic nano-diamond particles is 0.001 to 1 g / L.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a base metal plating film, a base metal plating bath, a method for producing the base metal plating film, an electronic component provided with the base metal plating film, a brightener for the base metal plating film, and an antioxidant for the base metal plating film.

[0002] In this specification, "nanodiamond" may be abbreviated as "ND." [Background technology]

[0003] Among the connecting parts used in electrical and electronic equipment, such as low-current (signal system) switches and connectors, those that are used repeatedly under low contact loads require high connection reliability, and therefore, connecting parts in which the surface of conductive metal members is plated with metals such as precious metals are used as such connecting parts. In addition to conductivity, the plating film may also be required to have a moderate gloss.

[0004] Patent Document 1 discloses a method for preparing a plating bath, aiming to obtain a high-quality, highly reliable plating film composited with carbon-based particles. This method involves dispersing carbon-based particles such as carbon nanotubes in a non-aqueous solvent, then adding the non-aqueous solvent to an aqueous solution of a metal salt containing base metal ions such as copper ions and stirring the mixture to disperse the carbon-based particles in the aqueous solution of the base metal salt. It is said that the use of a plating bath prepared by this method can produce electronic components with reduced impurity contamination. However, this method does not impart high gloss to the plating film. Furthermore, base metals are susceptible to air oxidation.

[0005] One method for imparting gloss to a plating film is to add a brightener to the plating bath. This brightener has the effect of adsorbing to crystal nuclei and inhibiting crystal growth, thereby miniaturizing the crystals, thereby smoothing the surface of the deposited precious metal and making it glossy (see, for example, Patent Document 2).

[0006] Non-patent document 1 proposes adding nanodiamond particles to a plating bath to incorporate them into the plating film, but it describes that the nanodiamond particles are not sufficiently dispersed in the plating solution, and therefore the nanodiamond particles in the plating bath are aggregated to the order of μm.

[0007] Patent Document 3 describes a configuration in which hydrophilic polymers or diamond microparticles into which ionic functional groups have been introduced are added to a metal plating solution together with a surfactant, and describes a configuration in which a dispersion containing 1 g / L of diamond microparticles into which anionic functional groups have been introduced is added at a rate of 2 g / L in Example 1, and a dispersion containing 1 g / L of diamond microparticles into which PEG has been introduced is added at a rate of 0.1 g / L in Example 2, but these addition amounts are not expected to improve the gloss and oxidation resistance of the plating film.

[0008] Patent Document 4 describes a configuration in which diamond microparticles with an average particle size of 10 nm to 300 nm and having hydrophilic polymers or ionic functional groups introduced therein, fluororesin microparticles with an average particle size of 100 nm to 300 nm, and a surfactant are added to a metal plating solution, and Examples 1 and 2 describe an electroless composite plating solution containing 2.0 g / L of grafted diamond microparticles.However, with a plating solution containing such a high concentration of diamond microparticles, it is not possible to expect improvements in the gloss and oxidation resistance of the plating film. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] WO2011 / 048984 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-117424 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-149071 [Patent Document 4] Japanese Patent Application Laid-Open No. 2012-092416 [Non-patent literature]

[0010] [Non-Patent Document 1] Hiroshi Matsubara “Surface Technology” Vol.65, No.2, (2014), pp. 88-93 Summary of the Invention [Problem to be solved by the invention]

[0011] An object of the present invention is to provide a base metal plating film having high gloss and oxidation resistance, and a method for producing the same.

[0012] Another object of the present invention is to provide a base metal plating bath that is useful for producing a base metal plating film having high brightness and oxidation resistance.

[0013] Another object of the present invention is to provide an electronic component provided with a base metal plating film having high gloss, surface hardness, electrical conductivity and oxidation resistance.

[0014] Another object of the present invention is to provide a novel brightener that imparts high brightness to base metal plating films.

[0015] Another object of the present invention is to provide a novel antioxidant that imparts oxidation resistance to base metal plating films. [Means for solving the problem]

[0016] As a result of intensive research to solve the above problems, the inventors have discovered that when base metal plating is performed using a plating bath containing base metal ions and to which hydrophilic nanodiamond particles have been added, a base metal plating film with high gloss and excellent oxidation resistance can be obtained.

[0017] The present invention provides the following base metal plating film, base metal plating bath, method for producing the base metal plating film, electronic component provided with the base metal plating film, brightener for base metal plating film, and antioxidant for base metal plating film. [1] A base metal plating film comprising a base metal matrix and hydrophilic nanodiamond particles dispersed in the base metal matrix. [2] A base metal plating film described in [1], which has a glossiness at an incident angle of 60° that is 10 or more higher than that of the same base metal plating film as described above except that it does not contain the hydrophilic nanodiamond particles. [3] The base metal plating film according to [1] or [2], wherein the increase in base metal oxide content after storage of the base metal plating film immediately after production at 25°C and 50% humidity for 7 days in a room away from direct sunlight is less than 1%, preferably less than 0.5%, more preferably less than 0.3%, and most preferably less than 0.1%. [4] The base metal plating film according to any one of [1] to [3], which is surfactant-free. [5] The base metal plating film according to any one of [1] to [4], wherein the hydrophilic nanodiamond particles are nanodiamond particles of the following (i) or (ii): (i) Nanodiamond particles coated with hydrophilic polymer; (ii) Nanodiamond particles modified with hydrophilic polymers. [6] The plating film according to any one of [1] to [5], wherein the base metal is at least one selected from the group consisting of iron, nickel, zinc, copper, tin, aluminum, tungsten, molybdenum, tantalum, magnesium, cobalt, bismuth, cadmium, titanium, zirconium, antimony, manganese, beryllium, chromium, germanium, vanadium, gallium, hafnium, indium, niobium, permalloy, rhenium, and thallium. [7] A base metal plating film according to any one of [1] to [6], wherein the average particle diameter (D50) of the hydrophilic nanodiamond particles dispersed in the base metal matrix by SEM method is in the range of 4 to 95 nm. [8] The base metal plating film according to [5], wherein the hydrophilic polymer is selected from the group consisting of polyglycerin, polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, poly(meth)acrylic acid, polyacrylamide, polyethyleneimine, vinyl ether polymers, cellulose derivatives, water-soluble polyesters, water-soluble phenolic resins, and natural polymer polysaccharides. [9] The base metal plating film according to any one of [1] to [8], wherein the base metal is copper, the crystallite size (A) of the 111 plane is 100 nm or less, the crystallite size (B) of the 220 plane is 80 nm or less, and the crystallite size ratio (A / B) of the 111 plane to the 220 plane is 1.3 or more.

[10] The base metal plating film according to any one of [1] to [8], wherein the base metal is copper, and the peak intensity ratio of the 111 plane to the 220 plane (111 plane / 220 plane) in the X-ray diffraction pattern is 3.0 or less.

[11] The base metal plating film according to any one of [1] to [8], wherein the base metal is nickel, the crystallite size (A) of the 111 plane is 25 nm or less, the crystallite size (C) of the 200 plane is 23 nm or less, and the crystallite size ratio (A / C) of the 111 plane to the 200 plane is 1.1 or more.

[12] A base metal plating bath containing base metal ions and hydrophilic nanodiamond particles, the concentration of the hydrophilic nanodiamond particles being 0.001 to 1 g / L.

[13] The base metal plating bath according to

[12] , having a haze of 0 to 0.5.

[14] The base metal plating bath according to

[12] or

[13] , wherein the particle size (D10) of the hydrophilic nanodiamond particles in the base metal plating bath is 10 to 60 nm.

[15] The base metal plating bath according to

[12] or

[13] , wherein the particle size (D50) of the hydrophilic nanodiamond particles in the base metal plating bath is 10 to 70 nm.

[16] The base metal plating bath according to

[12] or

[13] , wherein the particle size (D90) of the hydrophilic nanodiamond particles in the base metal plating bath is 10 to 90 nm.

[17] A method for producing a plating film described in any one of [1] to

[11] , characterized in that the specimen is immersed in a base metal plating bath containing base metal ions and hydrophilic nanodiamond particles, the concentration of the nanodiamond particles being 0.001 to 1 g / L, and electroplating is performed.

[18] The method for producing a plating film according to

[17] , wherein the haze of the base metal plating bath is 0 to 0.5.

[19] An electronic component comprising the plating film according to any one of [1] to

[11] .

[20] A brightener for base metal plating films containing hydrophilic nanodiamond particles. [twenty one] Antioxidant for base metal plating films containing hydrophilic nanodiamond particles. [Effects of the Invention]

[0018] The base metal plating film of the present invention has a structure in which nanodiamond particles are highly dispersed in a base metal matrix, and the nanodiamond particles inhibit the growth of base metal crystals, resulting in finer crystal grains, resulting in a smooth surface and high gloss and excellent oxidation resistance. The base metal plating film of the present invention also has excellent heat resistance, surface hardness, and electrical conductivity. Therefore, the base metal plating film of the present invention is suitable for use in connecting parts for electronic devices, decorative items, etc.

[0019] In addition, the base metal plating film of the present invention has a smooth surface, which reduces the coefficient of friction and the contact resistance, making it suitable for use in connecting parts (or electrical contacts) such as low-current (signal system) switches and connectors used in electrical and electronic devices that are used repeatedly under low contact loads.

[0020] The plating bath of the present invention is useful for producing a base metal plating film having high brightness and excellent oxidation resistance.

[0021] According to the method for producing a base metal plating film of the present invention, a base metal plating film having high gloss and excellent oxidation resistance can be produced efficiently with simple operations.

[0022] The electronic component of the present invention has a base metal plating film with high gloss and excellent oxidation resistance.

[0023] The brightener of the present invention is useful for forming a base metal plating film having high brightness.

[0024] The antioxidant of the present invention is useful for forming a base metal plating film having excellent oxidation resistance. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is an enlarged schematic view showing an example of a hydrophilic ND particle according to the present invention. [Figure 2] 1 shows the results of X-ray diffraction of the plating film formed on the brass plate in Comparative Example 1. [Figure 3] 1 shows the results of X-ray diffraction of the plating film formed on the brass plate in Example 4. [Figure 4] 1 shows the X-ray diffraction results of the plating film formed on the brass plate in Comparative Example 2 immediately after production and 5 days later. [Figure 5] 1 shows an XRD pattern of the copper plating film measured in Test Example 7. [Figure 6] 1 shows SEM photographs of the plating film of Test Example 8. (a) Without ND, (b) With ND. [Figure 7] C1s (XPS) in the copper plating film obtained in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0026] [Hydrophilic ND particles] The ND particles used in the present invention are hydrophilic ND particles, and these particles are (i) ND particles coated with a hydrophilic polymer, and (ii) ND particles modified with hydrophilic polymers The preferred hydrophilic ND particles are the ND particles of (ii).

[0027] ND particles with hydrophilic functional groups (OH, COOH, NH) introduced therein are known (e.g., JP 2018-30741 A), and for example, ND produced by the detonation method can be preferably used. Detonation methods include air-cooled detonation and water-cooled detonation. In the present invention, the air-cooled detonation method is preferred because it can produce NDs with smaller primary particles than the water-cooled detonation method. By performing detonation in an air atmosphere or a nitrogen atmosphere, hydrophilic ND particles with multiple hydrophilic functional groups (OH, COOH, NH) formed on the surface can be obtained. Coating or modification with a hydrophilic polymer is performed via the hydrophilic functional groups.

[0028] Examples of hydrophilic polymers include polyglycerin (PG), polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, poly(meth)acrylic acid, polyacrylamide, polyethyleneimine, vinyl ether polymers, cellulose derivatives, water-soluble polyesters, and natural polymeric polysaccharides. Examples of vinyl ether polymers include homopolymers or copolymers of alkyl vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isopropyl ether, vinyl butyl ether, and vinyl isobutyl ether (e.g., polyvinyl methyl ether, polyvinyl ethyl ether, and vinyl ether-maleic anhydride copolymers). Examples of cellulose derivatives include methyl cellulose, ethyl cellulose, propyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, and carboxyethyl cellulose. Examples of water-soluble polyesters include polydimethylolpropionic acid esters. Examples of natural polymeric polysaccharides include alginic acid or its salts, pectin, starch, agar, gum arabic, dextrin, and carrageenan. Preferred hydrophilic polymers are polyglycerin, polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, and poly(meth)acrylic acid, with polyglycerin being particularly preferred.

[0029] ND particles modified with a surface modifying group containing a polyglycerin chain have a structure in which, for example, polyglycerin represented by the following formula (1) is bonded to the surface functional group of the ND particle: In the following formula, n represents the number of glycerin units constituting the polyglycerin chain and is an integer of 1 or more.

[0030] HO-(C3H6O2) n -H (1) The C3H6O2 in the parentheses of formula (1) has a structure represented by the following formula (2) and / or (3).

[0031] -CH2-CHOH-CH2O- (2) -CH(CHOH)CHO- (3) The polyglycerol chain includes polyglycerol chains of a linear structure, a branched structure, and a cyclic structure.

[0032] The amount of the hydrophilic polymer introduced by modification or coating is, for example, about 0.05 to 1.0 part by mass, preferably about 0.4 to 1.0 part by mass, more preferably 0.5 to 0.9 parts by mass, and particularly preferably 0.6 to 0.8 parts by mass per part by mass of the ND particle portion. If the amount of the hydrophilic polymer introduced is within the above range, aggregation of the ND particles can be prevented. The mass ratio of the hydrophilic polymer portion to the ND particle portion can be determined by measuring the change in mass during heat treatment using a differential thermogravimetry analyzer (TG-DTA) or by measuring the composition ratio by elemental analysis.

[0033] Coating of ND particles with hydrophilic polymers can be achieved by contacting nanodiamond particles with a hydrophilic polymer solution and then centrifuging the solution to separate the hydrophilic polymers not involved in the coating, thereby collecting the nanodiamond particles coated with the hydrophilic polymers.

[0034] The modification of ND particles with hydrophilic polymers can be carried out by using the ND particles, on whose surfaces hydrophilic functional groups (OH, COOH, NH, etc.) have been introduced, as raw materials, and then bonding the hydrophilic polymer group to the hydrophilic functional groups via a linker group such as an ester bond, an amide bond, an imide bond, an ether bond, a urethane bond, or a urea bond. The linker group can be formed by a method of forming an ester or amide bond using a condensing agent such as dicyclohexylcarbodiimide, a water-soluble carbodiimide, or carbonyldiimidazole; a method of forming a urethane or urea bond using a hydrophilic polymer having an isocyanate group (N=C=O); or, if the hydrophilic polymer has a COOH group, by converting the COOH group to an acid halide (particularly an acid chloride) or an acid anhydride and reacting it with ND particles having an OH or NH group to form an ester or amide bond.

[0035] ND particles with introduced hydrophilic functional groups (OH, COOH, NH2) that are used as raw materials for coating with or modifying with hydrophilic polymers are preferably fine particles with an average primary particle size of 10 nm or less, for example, 1 to 10 nm.

[0036] The hydrophilic ND particles of the present invention are preferably fine particles with an average primary particle size of 12 nm or less, for example, 1 to 12 nm, and preferably 3 to 12 nm.

[0037] The average particle size of the primary particles of ND particles having hydrophilic functional groups and ND particles coated or modified with hydrophilic polymers was measured by small-angle X-ray scattering (SAXS) using an X-ray diffraction device (trade name "Smart Lab", manufactured by Rigaku Corporation), and the particle size distribution analysis software (trade name "NANO-Solver", manufactured by Rigaku Corporation) was used to determine whether the primary nanodiamond particles were spherical and had a particle density of 3.51 g / cm. 3 This can be determined by estimating the primary particle size of nanodiamonds in the scattering angle range of 1° to 3°, assuming that the scattering angle is 1° to 3°.

[0038] The hydrophilic ND particles are preferably fine particles with an average primary particle size of 10 nm or less, for example, 1 to 10 nm.

[0039] By making the surface of ND particles hydrophilic, aggregation can be prevented, simultaneously improving gloss and oxidation resistance. On the other hand, ND particles such as those described in Non-Patent Document 1, which do not have hydrophilic functional groups or hydrophilic polymers, do not improve gloss and oxidation resistance even when incorporated into base metal plating films. As described in Test Example 2 herein, the average particle size of ND primary particles obtained by the detonation method is 10 nm or less, while the particle size of ND primary particles obtained by the impact compression method is significantly greater than 10 nm. Therefore, ND particles produced by the detonation method are preferred. In the present invention, there is no need to add surfactants to the base metal plating bath. If a plating bath contains surfactants, even a small amount may be incorporated into the base metal plating film, so it is preferable not to use surfactants. Furthermore, it is preferable that the base metal plating film be surfactant-free.

[0040] [Base metal plating film] The base metal plating film of the present invention is a base metal plating film containing a base metal matrix and hydrophilic ND particles dispersed in the base metal matrix. In a preferred embodiment of the present invention, the hydrophilic ND particles may be uniformly dispersed in the base metal matrix or may be densely dispersed near the surface of the base metal matrix.

[0041] The base metal may be at least one selected from the group consisting of iron, nickel, zinc, copper, tin, aluminum, tungsten, molybdenum, tantalum, magnesium, cobalt, bismuth, cadmium, titanium, zirconium, antimony, manganese, beryllium, chromium, germanium, vanadium, gallium, hafnium, indium, niobium, rhenium, and thallium, preferably at least one selected from the group consisting of copper, nickel, zinc, tin, chromium, and permalloy, and more preferably at least one selected from the group consisting of copper, nickel, zinc, and tin.

[0042] A preferred embodiment of the base metal plating film of the present invention is a base metal plating film containing a base metal matrix and hydrophilic ND particles dispersed in the base metal matrix, characterized in that the gloss at an incident angle of 60° is 770 or more. Note that the gloss at 100% reflection is 1000.

[0043] The gloss of the base metal plating film of the present invention at an incident angle of 60° is 770 or more, preferably 780 or more, more preferably 800 or more, and even more preferably 850 or more, when the base metal is copper.

[0044] The gloss of the base metal plating film of the present invention at an incident angle of 60° is 560 or more when the base metal is nickel, 785 or more when the base metal is tin, 575 or more when the base metal is permalloy, and 410 or more when the base metal is zinc.

[0045] Furthermore, compared to a base metal plating film having the same composition as the present invention except that it does not contain hydrophilic ND particles, the gloss of the base metal plating film of the present invention at an incident angle of 60° is, for example, 10 or more (e.g., 10 to 200) higher, preferably 15 or more higher, more preferably 35 or more higher, particularly preferably 55 or more higher, and most preferably 85 or more higher.

[0046] The base metal plating film of the present invention preferably exhibits an increase in base metal oxide of less than 1%, more preferably less than 0.5%, even more preferably less than 0.3%, and most preferably less than 0.1% after storage for 7 days at room temperature (around 25°C, humidity around 50%) away from direct sunlight, compared to the base metal plating film immediately after production.

[0047] The surface roughness (Ra) of the base metal plating film of the present invention is, for example, 0.5 μm or less, preferably 0.4 μm or less, more preferably 0.3 μm or less, particularly preferably 0.15 μm or less, and most preferably 0.1 μm or less.

[0048] In the base metal plating film of the present invention, the particle diameter of the hydrophilic ND particles dispersed in the base metal matrix, as measured by SEM, is, for example, in the range of 4 to 95 nm, preferably 10 to 80 nm, particularly preferably 20 to 60 nm, and most preferably 30 to 50 nm.

[0049] In one preferred embodiment of the present invention, when the base metal is copper, the crystallite size (A) of the 111 plane is 100 nm or less, preferably 80 nm or less, more preferably 70 nm or less, even more preferably 60 nm or less, particularly preferably 50 nm or less, and most preferably 45 nm or less, and the crystallite size (B) of the 220 plane is 80 nm or less, preferably 60 nm or less, more preferably 50 nm or less, even more preferably 40 nm or less, particularly preferably 35 nm or less, and most preferably 30 nm or less. The crystallite size ratio (A / B) of the 111 plane to the 220 plane is preferably 1.3 or more, more preferably 1.3 to 1.6.

[0050] In one preferred embodiment of the present invention, when the base metal is nickel, the crystallite size (A) of the 111 plane is 25 nm or less, preferably 24 nm or less, more preferably 23 nm or less, and even more preferably 22 nm or less, and the crystallite size (C) of the 200 plane is 23 nm or less, preferably 20 nm or less, more preferably 18 nm or less, even more preferably 16 nm or less, and particularly preferably 14 nm or less. The crystallite size ratio (A / C) of the 111 plane to the 200 plane is preferably 1.1 or more, and more preferably 1.1 to 1.6.

[0051] In one preferred embodiment of the present invention, when the base metal is copper, the peak intensity ratio of the 111 plane to the 220 plane (111 plane / 220 plane) in the X-ray diffraction (XRD) pattern is preferably 3.0 or less, more preferably 1.4 to 3.0.

[0052] When the conductivity of annealed standard soft copper is taken as 100% IACS, the conductivity of the copper plating film of the present invention is preferably 80% IACS or higher, more preferably 85% IACS or higher, even more preferably 90% IACS or higher, particularly preferably 92% IACS or higher, and most preferably 94% IACS or higher. The conductivity is determined by calculating the volume resistivity from the surface resistivity value measured by a four-point terminal method and the thickness of the plating film measured by a micrometer, and converting this into electrical conductivity as IACS%. The volume resistivity can also be determined as the average value of values ​​measured at multiple points (for example, five points at the top, bottom, left, and right) on a plating film sample. Note that IACS (international annealed copper standard)% is used as the standard for electrical resistance when measuring the volume resistivity of annealed standard soft copper (volume resistivity: 1.7241×10 -2 The conductivity is defined as 100% IACS.

[0053] Furthermore, in the base metal plating film of the present invention, the content of hydrophilic ND particles is, for example, 0.5 to 25 area %, preferably 2 to 20 area %, and particularly preferably 5 to 15 area % of the area of ​​the base metal plating film. The content (area %) of hydrophilic ND particles can be measured by SEM observation of the cross section of the plating layer. In Comparative Example 2 and Figure 4 of the present specification, the base metal plating film containing non-hydrophilic ND particles did not show either an increase in gloss or an antioxidant effect, and the inventors have therefore clarified that the "hydrophilicity" of ND particles is important for these effects.

[0054] The hydrophilic ND particles used in the present invention preferably have multiple or many hydrophilic functional groups, or more preferably are coated or modified with at least one hydrophilic polymer, which prevents aggregation and allows for the production of plating films with high gloss and excellent oxidation resistance. Figure 1 is an enlarged schematic diagram showing an example of ND particles having surface modification groups in the present invention. 1 indicates an ND particle having a surface modification group, 2 indicates an ND particle (part), and 3 indicates the surface modification group.

[0055] [Method of manufacturing base metal plating film] The base metal plating film of the present invention can be produced by a known electroplating method (preferably, an electrolytic composite plating method) or electroless plating method. More specifically, by immersing a target substrate (e.g., a conductive substrate such as a brass substrate) in a plating bath containing base metal ions and hydrophilic ND particles to perform electroplating or electroless plating, the base metal ions are precipitated on the surface of the substrate together with the hydrophilic ND particles, and the hydrophilic ND particles are incorporated into the base metal coating. By continuing this process until a desired thickness is achieved, a base metal plating film (or a plating film composed of a base metal-hydrophilic ND particle composite material) having a structure in which the hydrophilic ND particles are dispersed in a base metal matrix can be produced.

[0056] The thickness of the base metal plating film can be set appropriately depending on the application, for example, approximately 0.1 to 1000 μm. When used to coat the surface of conductive metal components as connecting parts such as switches and connectors, the thickness of the base metal plating film is, for example, approximately 0.1 to 50 μm.

[0057] (base metal plating bath) The base metal plating bath of the present invention contains a plating solution and hydrophilic ND particles. The content of the hydrophilic ND particles in the base metal plating bath is, for example, in the range of 0.001 to 1.0 g / L (the lower limit is preferably 0.003 g / L, more preferably 0.006 g / L, even more preferably 0.01 g / L, and particularly preferably 0.03 g / L; the upper limit is preferably 0.8 g / L, even more preferably 0.6 g / L, and particularly preferably 0.5 g / L), and is preferably 0.01 to 0.5 g / L. If the content of the hydrophilic ND particles is within the above range, high gloss and oxidation resistance of the base metal plating film, as well as good adhesion to the substrate, can be obtained.

[0058] The base metal plating bath has excellent transparency because it contains hydrophilic ND particles in a highly dispersed (or colloidally dispersed) state, and the haze is preferably about 0 to 5, more preferably about 0 to 2, even more preferably about 0 to 1, particularly preferably about 0 to 0.5, and most preferably 0 to 0.4. The haze can be measured in accordance with JIS K7136.

[0059] The particle size (D10) of the hydrophilic ND particles in the base metal plating bath is, for example, 95 nm or less, preferably 60 nm or less, particularly preferably 50 nm or less, and most preferably 40 nm or less. The lower limit of the particle size (D10) of the hydrophilic ND particles is, for example, 10 nm.

[0060] The particle size (D50) of the hydrophilic ND particles in the base metal plating bath is, for example, 95 nm or less, preferably 70 nm or less, particularly preferably 60 nm or less, and most preferably 50 nm or less. The lower limit of the particle size (D50) of the hydrophilic ND particles is, for example, 20 nm.

[0061] The particle size (D90) of the hydrophilic ND particles in the base metal plating bath is, for example, 95 nm or less, preferably 90 nm or less, and particularly preferably 80 nm or less. The lower limit of the particle size (D90) of the hydrophilic ND particles is, for example, 50 nm. The particle size of the hydrophilic ND particles in the base metal plating bath can be measured by dynamic light scattering.

[0062] The base metal plating bath can be prepared, for example, by adding a hydrophilic ND particle dispersion to a plating solution described below. The electroless base metal plating bath may contain a water-soluble base metal salt, hydrophilic ND particles, a phosphorus source (in the case of electroless nickel-phosphorus alloy plating), a reducing agent, a complexing agent, etc. The electroless base metal plating bath is preferably an electroless nickel-phosphorus alloy base metal plating bath.

[0063] The concentration of the water-soluble base metal salt in the electrolytic and electroless base metal plating baths is, for example, 0.01 to 0.5 mol / L, preferably 0.05 to 0.2 mol / L, in terms of the concentration of the base metal ions supplied to the base metal plating bath.

[0064] Examples of reducing agents and phosphorus sources contained in the electroless base metal plating bath include phosphinates such as sodium phosphinate. When a phosphinate is used, the concentration of the phosphinate in the base metal plating bath is, for example, 0.02 to 0.5 mol / L, and preferably 0.1 to 0.2 mol / L.

[0065] Examples of complexing agents contained in electrolytic and electroless base metal plating baths include citric acid, lactic acid, malic acid, glycolic acid, and salts thereof. Examples of citric acid include sodium citrate and potassium citrate. When citric acid and / or its salts are used, the concentration of citric acid and / or its salts in the electrolytic and electroless base metal plating baths is, for example, 0.02 to 1.0 mol / L, and preferably 0.1 to 0.5 mol / L.

[0066] In addition to the components described above, the electrolytic and electroless base metal plating baths may contain other components, such as pH buffers and stabilizers to inhibit the base metal plating bath from self-decomposing.

[0067] The pH of the base metal plating bath is 5 to 11, for example.

[0068] (plating solution) The plating solution of the present invention contains components essential for preparing a plating film, but does not contain the above-mentioned hydrophilic ND particles. The plating solution contains at least base metal ions.

[0069] The plating solution can be prepared by blending, for example, a water-soluble base metal salt, a conductivity salt, a complexing agent, and additives for adjusting the appearance and physical properties of the coating. The water-soluble base metal salt exists as a base metal ion in the base metal plating bath. Alternatively, the water-soluble base metal salt may exist as an oxyacid ion of the base metal or a base metal complex ion bound to a complexing agent.

[0070] Examples of plating solutions for base metal plating include base metal sulfate plating solutions containing base metal sulfates, sulfuric acid, chloride ions, etc.; base metal cyanide plating solutions containing base metal cyanides, sodium cyanide, alkali carbonates, Rochelle salt, etc.; and base metal pyrophosphate plating solutions containing base metal pyrophosphates, potassium pyrophosphate, ammonia water, potassium nitrate, etc.

[0071] (Hydrophilic ND particle dispersion and its preparation method) The hydrophilic ND particle dispersion liquid is obtained by dispersing hydrophilic ND particles in a dispersion medium (preferably water). The concentration of the hydrophilic ND particles in the hydrophilic ND particle dispersion liquid is, for example, about 1 to 100 g / L.

[0072] As the hydrophilic ND particles, hydrophilic ND particles in which the hydrophilic functional groups of the ND particles are coated or modified with a hydrophilic polymer are preferred in terms of excellent dispersibility, and hydrophilic ND particles having a water-soluble polymer containing a polyglycerin chain are particularly preferred.

[0073] The particle size (D50) of the hydrophilic ND particles in the hydrophilic ND particle dispersion is, for example, 95 nm or less, preferably 70 nm or less, particularly preferably 60 nm or less, and most preferably 50 nm or less. The lower limit of the particle size (D50) of the hydrophilic ND particles is, for example, 10 nm. The particle size of the hydrophilic ND particles in the hydrophilic ND particle dispersion can be measured by dynamic light scattering (DLS).

[0074] The hydrophilic ND particle dispersion liquid can be added to a base metal plating bath to impart gloss to the resulting base metal plating film, and can therefore be used, for example, as a brightener for base metal plating films.

[0075] (Method for preparing hydrophilic ND particle dispersion) An example of a method for producing a dispersion of hydrophilic ND particles modified with polyglycerin chains is described below. Hydrophilic ND particles other than polyglycerin can be easily produced by those skilled in the art with reference to the general production method described above and the method for producing a dispersion of hydrophilic ND particles modified with polyglycerin chains described below.

[0076] (generation process) First, an explosive with an electric detonator attached is placed inside a pressure-resistant container for detonation, and the container is sealed in a state where atmospheric gas and the explosive coexist. The container is made of, for example, iron, and has a volume of, for example, 0.5 to 40 m 3 As the explosive, a mixture of trinitrotoluene (TNT) and cyclotrimethylenetrinitramine, i.e., hexogen (RDX), can be used. The mass ratio of TNT to RDX (TNT / RDX) is, for example, in the range of 40 / 60 to 60 / 40.

[0077] In the production process, an electric detonator is then detonated to detonate the explosive inside the container. During detonation, the explosive undergoes partial incomplete combustion, liberating carbon, which is used as raw material to generate ND particles due to the action of the pressure and energy of the shock wave generated by the explosion. The generated ND particles aggregate very firmly between adjacent primary particles or crystallites, due to the action of van der Waals forces and the Coulomb interaction between crystal planes, forming an agglomerate.

[0078] In the production step, the container is then left to cool at room temperature for about 24 hours, lowering the temperature of the container and its interior. After this cooling, the ND particle crude product (including the aggregates of ND particles and soot produced as described above) adhering to the inner wall of the container is scraped off with a spatula, thereby obtaining the ND particle crude product.

[0079] (Acid treatment process) The acid treatment step is a step in which a strong acid is applied to the raw material ND particle crude product in, for example, an aqueous solvent to remove metal oxides. The ND particle crude product obtained by the detonation method is likely to contain metal oxides, such as Fe, Co, and Ni, which originate from the container used in the detonation method. For example, by applying a specific strong acid in an aqueous solvent, metal oxides can be dissolved and removed from the ND particle crude product. The strong acid used in this acid treatment is preferably a mineral acid, such as hydrochloric acid, hydrofluoric acid, sulfuric acid, nitric acid, or a mixture thereof. The concentration of the strong acid used in the acid treatment is, for example, 1 to 50 mass %. The acid treatment temperature is, for example, 70 to 150°C. The acid treatment time is, for example, 0.1 to 24 hours. The acid treatment can be performed under reduced pressure, normal pressure, or increased pressure. After such acid treatment, it is preferable to wash the solids (including ND aggregates) with water, for example, by decantation, until the pH of the precipitation liquid reaches, for example, 2 to 3. When the content of metal oxides in the ND particle crude product obtained by the detonation method is small, the acid treatment described above may be omitted.

[0080] (Oxidation treatment process) The oxidation treatment process is a process in which graphite is removed from the ND particle crude product using an oxidizing agent. The ND particle crude product obtained by the detonation method contains graphite, which is derived from the carbon liberated by the partial incomplete combustion of the explosive used and which did not form ND crystals. For example, after the above-mentioned acid treatment, graphite can be removed from the ND particle crude product by treating it with a specific oxidizing agent in an aqueous solvent.

[0081] Examples of oxidizing agents used in this oxidation treatment include chromic acid, chromic anhydride, dichromic acid, permanganic acid, perchloric acid, nitric acid, mixtures thereof, mixed acids of at least one acid selected from these with other acids (e.g., sulfuric acid), and salts thereof. In the present invention, the use of mixed acids (particularly mixed acids of sulfuric acid and nitric acid) is preferred because it is environmentally friendly and has an excellent effect of oxidizing and removing graphite.

[0082] The mixing ratio of sulfuric acid to nitric acid (former / latter; mass ratio) in the mixed acid is preferably, for example, 60 / 40 to 95 / 5, since this allows efficient oxidization and removal of graphite at temperatures of, for example, 130°C or higher (particularly preferably 150°C or higher; the upper limit is, for example, 200°C) even under pressures near atmospheric pressure (for example, 0.5 to 2 atm). The lower limit is preferably 65 / 35, particularly preferably 70 / 30. The upper limit is preferably 90 / 10, particularly preferably 85 / 15, and most preferably 80 / 20.

[0083] If the proportion of nitric acid in the mixed acid exceeds the above range, the content of sulfuric acid, which has a high boiling point, decreases, so that the reaction temperature becomes, for example, 120°C or lower under pressure near atmospheric pressure, and the graphite removal efficiency tends to decrease. On the other hand, if the proportion of nitric acid in the mixed acid is below the above range, the content of nitric acid, which greatly contributes to the oxidation of graphite, decreases, so that the graphite removal efficiency tends to decrease.

[0084] The amount of the oxidizing agent (particularly the mixed acid) used is, for example, 10 to 50 parts by mass, preferably 15 to 40 parts by mass, and particularly preferably 20 to 40 parts by mass, relative to 1 part by mass of the ND particle crude product. The amount of sulfuric acid used in the mixed acid is, for example, 5 to 48 parts by mass, preferably 10 to 35 parts by mass, and particularly preferably 15 to 30 parts by mass, relative to 1 part by mass of the ND particle crude product, and the amount of nitric acid used in the mixed acid is, for example, 2 to 20 parts by mass, preferably 4 to 10 parts by mass, and particularly preferably 5 to 8 parts by mass, relative to 1 part by mass of the ND particle crude product.

[0085] When the mixed acid is used as the oxidizing agent, a catalyst may be used together with the mixed acid. The use of a catalyst can further improve the efficiency of graphite removal. Examples of the catalyst include copper (II) carbonate. The amount of catalyst used is, for example, about 0.01 to 10 parts by mass per 100 parts by mass of the ND particle crude product.

[0086] The oxidation treatment temperature is, for example, 100 to 200° C. The oxidation treatment time is, for example, 1 to 24 hours. The oxidation treatment can be carried out under reduced pressure, normal pressure, or increased pressure.

[0087] (drying process) This method preferably then includes a drying step, in which, for example, the liquid is evaporated from the solution containing hydrophilic ND particles having hydrophilic functional groups obtained through the above steps using a spray dryer or evaporator, and the resulting residual solid is then dried by heating in a drying oven. The heating temperature is, for example, 40 to 150°C. ND powder is obtained through this drying step.

[0088] (Oxygen oxidation process) In the oxygen oxidation process, the ND powder is heated in a gas atmosphere furnace under a gas atmosphere of a predetermined composition containing oxygen. Specifically, the ND powder is placed in the gas atmosphere furnace, an oxygen-containing gas is supplied to or passed through the furnace, and the temperature inside the furnace is raised to a temperature condition set as the heating temperature, whereby the oxygen oxidation process is carried out.

[0089] The temperature condition for the oxygen oxidation treatment is, for example, 250 to 500°C. To obtain hydrophilic ND particles with a negative zeta potential, the temperature condition for this oxygen oxidation treatment is preferably a relatively high temperature, for example, 400 to 450°C. The oxygen-containing gas is a mixed gas containing an inert gas in addition to oxygen. Examples of inert gases include nitrogen, argon, carbon dioxide, and helium. The oxygen concentration of the mixed gas is, for example, 1 to 35% by volume.

[0090] (Hydrogenation process) Furthermore, if hydrophilic ND particles with a positive zeta potential are desired, a hydrogenation process is performed after the above-described oxygen oxidation process. In the hydrogenation process, the ND powder that has undergone the oxygen oxidation process is heated in a gas atmosphere furnace under a hydrogen-containing gas atmosphere of a predetermined composition. Specifically, a hydrogen-containing gas is supplied to or passed through the gas atmosphere furnace in which the ND powder is disposed, and the temperature inside the furnace is raised to a temperature condition set as the heating temperature, thereby performing the hydrogenation process. The temperature condition for this hydrogenation process is, for example, 400 to 800°C. The hydrogen-containing gas used in this embodiment is a mixed gas containing an inert gas in addition to hydrogen. Examples of inert gases include nitrogen, argon, carbon dioxide, and helium. The hydrogen concentration of the mixed gas is, for example, 1 to 50% by volume.

[0091] (Crushing process) Even after purification through the above series of processes, hydrophilic ND particles often remain in the form of aggregates (secondary particles) in which primary particles aggregate due to very strong interactions between them. Therefore, a crushing process is preferably performed to separate the primary particles from the aggregates. Specifically, ND powder that has undergone the oxygen oxidation process or the subsequent hydrogenation process is first suspended in pure water to prepare a slurry containing ND particles with hydrophilic functional groups (OH, COOH, NH, etc.). In preparing the slurry, centrifugation may be performed to remove relatively large aggregates from the hydrophilic ND particle suspension, or the ND particle suspension with hydrophilic functional groups may be subjected to ultrasonic treatment. The slurry is then subjected to a wet crushing process. The crushing process can be performed using, for example, a high-shear mixer, high-shear mixer, homomixer, ball mill, bead mill, high-pressure homogenizer, ultrasonic homogenizer, or colloid mill. The crushing process may also be performed using a combination of these. From the standpoint of efficiency, a bead mill is preferred.

[0092] By undergoing this disintegration step, an aqueous ND particle dispersion containing ND primary particles having hydrophilic functional groups can be obtained. The dispersion obtained through the disintegration step may be subjected to classification to remove coarse particles. For example, coarse particles can be removed from the dispersion by classification using a classification device and centrifugal separation.

[0093] (drying process) This method preferably then includes a drying step, in which, for example, the liquid is evaporated from the aqueous dispersion of ND particles having hydrophilic functional groups obtained through the above steps using a spray dryer or evaporator, and the resulting residual solid is then dried by heating in a drying oven. The heating temperature is, for example, 40 to 150°C. Through this drying step, ND particles having hydrophilic functional groups are obtained as a powder.

[0094] (modification process) Hydrophilic ND particles modified with polyglycerin chains can be obtained, for example, by directly ring-opening polymerizing glycidol with ND particles having hydrophilic functional groups obtained through the above process. ND particles have carboxyl groups and hydroxyl groups on their surfaces that are generated during the manufacturing process, and by reacting these functional groups with glycidol, the ND surface can be modified with a hydrophilic polymer.

[0095] The reaction (ring-opening polymerization) between ND particles having hydrophilic functional groups and glycidol can be carried out, for example, by adding glycidol and a catalyst to ND particles having hydrophilic functional groups in an inert gas atmosphere and heating to 50 to 100°C. The catalyst can be an acidic catalyst or a basic catalyst. Examples of the acidic catalyst include trifluoroboron etherate, acetic acid, and phosphoric acid, while examples of the basic catalyst include triethylamine, pyridine, dimethylaminopyridine, and triphenylphosphine.

[0096] The amount of glycidol used in the ring-opening polymerization is, for example, 20 parts by mass or more, and preferably 20 to 150 parts by mass, relative to 1 part by mass of ND particles having a hydrophilic functional group. If the amount of glycidol used is below the above range, sufficient dispersibility tends to be difficult to obtain.

[0097] After the reaction is complete, the resulting reaction product is preferably purified by, for example, filtration, centrifugation, extraction, water washing, neutralization, or a combination of these. This results in a hydrophilic ND particle dispersion (preferably, a hydrophilic ND particle aqueous dispersion) according to the present invention. While glycidol is used to produce ND particles modified with polyglycerin, ND particles modified with a hydrophilic polymer other than polyglycerin, or ND particles modified with a hydrophilic polymer, can be easily produced by those skilled in the art by referring to the above description and known techniques.

[0098] [Electronic Components] The electronic component of the present invention is characterized by comprising the above-mentioned base metal plating film. The electronic component of the present invention may have other plating films in addition to the above-mentioned base metal plating film, for example, one or more layers of undercoat plating film. The electronic component of the present invention includes, for example, connecting parts (e.g., connectors) for electronic devices such as personal digital assistants (PDAs) and mobile phones.

[0099] [Brightener] The brightener for base metal plating films of the present invention is characterized by containing the above-mentioned hydrophilic ND particles.

[0100] The glossing agent may contain other components in addition to the hydrophilic ND particles, but the proportion of the content of the hydrophilic ND particles in the total amount of the glossing agent is, for example, 50% by mass or more, preferably 60% by mass or more, particularly preferably 70% by mass or more, most preferably 80% by mass or more, and particularly preferably 90% by mass or more.

[0101] [Antioxidants] The antioxidant for base metal plating films of the present invention is characterized by containing the above-mentioned hydrophilic ND particles.

[0102] The antioxidant may contain other components in addition to the hydrophilic ND particles, but the proportion of the content of the hydrophilic ND particles in the total amount of the antioxidant is, for example, 50% by mass or more, preferably 60% by mass or more, particularly preferably 70% by mass or more, most preferably 80% by mass or more, and particularly preferably 90% by mass or more. [Example]

[0103] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The ND particle concentration, particle size, and zeta potential were measured by the following methods.

[0104] <ND particle concentration> The ND particle concentration of the ND particle aqueous dispersion was calculated based on the weighed value of 3 to 5 g of the dispersion and the value of the dried material (powder) remaining after evaporating the water content from the weighed dispersion by heating, which was weighed using a precision balance.

[0105] <Particle size> The particle sizes (median diameter, D10, D50, and D90) of the ND particles contained in the ND particle aqueous dispersion and the base metal plating bath were measured by dynamic light scattering (non-contact backscattering method) using an apparatus manufactured by Malvern (trade name "Zetasizer Nano ZS").

[0106] Zeta potential The zeta potential of the ND particles contained in the ND particle aqueous dispersion was measured by laser Doppler electrophoresis using a Malvern device (trade name "Zetasizer Nano ZS") The ND particle aqueous dispersion used for the measurement was diluted with ultrapure water to an ND particle concentration of 0.2 mass % and then subjected to ultrasonic irradiation using an ultrasonic cleaner, and the zeta potential measurement temperature was 25°C.

[0107] Preparation Example 1 An aqueous dispersion of hydrophilic ND particles was prepared through the following steps.

[0108] (generation process) First, the formed explosives with electric detonators attached were placed in a pressure-resistant container (made of iron, volume: 15 m 3 ) and the container was sealed. 0.50 kg of a mixture of TNT and RDX (TNT / RDX (mass ratio) = 50 / 50) was used as the explosive. Next, an electric detonator was detonated to detonate the explosive inside the container. Next, the container was left at room temperature for 24 hours to lower the temperature of the container and its interior. After this cooling, the ND particle crude product (including the aggregates of ND particles and soot generated by the above detonation method) adhering to the inner wall of the container was collected to obtain the ND particle crude product.

[0109] (Acid treatment process) Next, the crude ND particle product obtained in the above step was subjected to an acid treatment. Specifically, 200 g of the crude ND particle product was added with 6 L of 10 mass % hydrochloric acid to obtain a slurry, which was then subjected to a heat treatment (heating temperature: 85 to 100°C) under reflux at normal pressure for 1 hour. Next, after cooling, the solid content (including ND aggregates and soot) was washed with water by decantation. The solid content was repeatedly washed with water by decantation until the pH of the precipitate solution reached 2 from the low pH side.

[0110] (Oxidation treatment process) Next, a mixed acid treatment was carried out. Specifically, 6 L of a 98 mass % aqueous sulfuric acid solution and 1 L of a 69 mass % aqueous nitric acid solution were added to the precipitate liquid (containing ND aggregates) obtained through decantation after the acid treatment to form a slurry, and this slurry was then subjected to a heat treatment (heating temperature: 140 to 160°C) for 48 hours under normal pressure and reflux conditions. Next, after cooling, the solid content (containing ND aggregates) was washed with water by decantation. The supernatant liquid was colored at the beginning of the washing, but the solid content was repeatedly washed with water by decantation until the supernatant liquid became visually transparent.

[0111] (drying process) Next, 1000 mL of the liquid containing ND particles having hydrophilic functional groups obtained through the above-mentioned water washing treatment was spray-dried using a spray dryer (trade name "Spray Dryer B-290", manufactured by Nippon Buchi Co., Ltd.), thereby obtaining 50 g of ND powder.

[0112] (Oxygen oxidation process) Next, 4.5 g of the ND powder obtained as described above was placed in the core tube of a gas atmosphere furnace (trade name "Gas Atmosphere Tube Furnace KTF045N1", manufactured by Koyo Thermo System Co., Ltd.). Nitrogen gas was continuously passed through the core tube at a flow rate of 1 L / min for 30 minutes. Then, the flowing gas was switched from nitrogen to a mixed gas of oxygen and nitrogen, and the mixed gas was continuously passed through the core tube at a flow rate of 1 L / min. The oxygen concentration in the mixed gas was 4% by volume. After switching to the mixed gas, the temperature inside the furnace was raised to 400°C, which was the set heating temperature. Regarding the heating rate, it was set to 10°C / min from 380°C, which was 20°C lower than the set heating temperature, to 380°C, and then 1°C / min from 380°C to 400°C. Then, while maintaining the temperature condition inside the furnace at 400°C, an oxygen oxidation treatment was performed on the ND powder inside the furnace. The treatment time was 3 hours.

[0113] After the oxygen oxidation treatment, the evaluation of oxygen-containing functional groups such as carboxyl groups in the ND particles was performed by the following FT-IR analysis. From the spectrum obtained in this analysis, an absorption near 1780 cm -1 attributed to the C=O stretching vibration was detected as the main peak. From this, it was confirmed that the ND powder mainly contained ND particles (ND-COOH) having a plurality of carboxyl groups as surface functional groups.

[0114] <FT-IR Analysis Conditions> Fourier transform infrared spectroscopy (FT-IR) was performed using an FT-IR device (trade name "Spectrum400 type FT-IR", manufactured by PerkinElmer Japan Co., Ltd.). In this measurement, the infrared absorption spectrum was measured while heating the sample to 150°C under a vacuum atmosphere. For heating under a vacuum atmosphere, a Model-HC900 type Heat Chamber and a TC-100WA type Thermo Controller manufactured by S.T. Japan Co., Ltd. were used in combination.

[0115] (Crushing Process) First, 0.3 g of the ND powder that had undergone the oxygen oxidation process and 29.7 mL of pure water were mixed in a 50 mL sample bottle to obtain approximately 30 mL of slurry. Next, the pH of the slurry was adjusted by adding 1 N aqueous sodium hydroxide solution, and then ultrasonicated for 2 hours using an ultrasonicator (product name "Ultrasonic Cleaner AS-3" manufactured by AS ONE Corporation). Subsequently, bead milling was performed using a bead milling machine (product name "Parallel Four-Cylinder Sand Grinder LSG-4U-2L" manufactured by Aimex Co., Ltd.). Specifically, 30 mL of the ultrasonically irradiated slurry and 30 μm diameter zirconia beads were sealed in a 100 mL milling vessel (manufactured by Aimex Co., Ltd.), and the machine was operated to perform bead milling. In this bead milling, the amount of zirconia beads added was approximately 33% of the volume of the milling vessel, the milling vessel rotation speed was 2570 rpm, and the milling time was 2 hours.

[0116] Next, the slurry that had been subjected to the disintegration step was centrifuged using a centrifugal separator (classification operation). The centrifugal force in this centrifugation step was 20,000×g, and the centrifugation time was 10 minutes.

[0117] Next, 25 mL of the supernatant of the ND particle-containing solution that had been subjected to the centrifugal separation treatment was collected to obtain an ND particle aqueous dispersion (ND-COOH). The ND particle concentration in the ND particle aqueous dispersion was 11.8 g / L. Furthermore, when measured using pH test paper (product name "Three-Band pH Test Paper", manufactured by AS ONE Corporation), the pH was 9.33. The particle size D50 was 3.97 nm, the particle size D90 was 7.20 nm, and the zeta potential was -42 mV.

[0118] (modification process) The ND particle aqueous dispersion obtained above was dried using an evaporator to obtain a black dry powder. The obtained dry powder (100 mg) was added to 12 mL of glycidol in a glass reactor and dissolved by sonication for 2 hours at room temperature using an ultrasonic cleaner (trade name "BRANSON 2510" manufactured by Marshall Scientific). This was then reacted at 140 °C for 20 hours with stirring under a nitrogen atmosphere. After cooling, 120 mL of methanol was added, sonication was performed, and the mixture was centrifuged at 50,400 G for 2 hours to obtain a precipitate. Another 120 mL of methanol was added to this precipitate, and the washing and centrifugation process was repeated five times. Finally, the precipitate was dialyzed against pure water using a dialysis membrane (Spectra / Pro dialysis membrane, MWCO: 12-14 kDa). The residual methanol was replaced with water and freeze-dried to obtain a gray powder of hydrophilic ND particles modified with polyglycerin (PG-ND particles).

[0119] The ratio of ND particles to surface modifying groups was measured by TG-DTA thermal analysis, and the ratio was ND particles:surface modifying groups=1:0.7.

[0120] The PG-ND gray powder and water were added, and the concentration was adjusted to 10 g / L based on the mass of the ND particles to obtain a PG-ND particle aqueous dispersion.

[0121] Example 1 The aqueous dispersion of PG-ND particles obtained in Preparation Example 1 was added to a copper plating solution (product name "Electrolytic Plating Solution", manufactured by Kiyokawa Plating Industry Co., Ltd.) to obtain plating bath (1) (PG-ND particle concentration in plating bath: 1 g / L, CuSO 5H O concentration: 5 mass %).

[0122] The particle sizes of the PG-ND particles in the plating bath (1) were measured, and the particle sizes (D10), (D50), and (D90) were 30 nm, 44 nm, and 76 nm, respectively.

[0123] The plating bath (1) was transparent and had no turbidity whatsoever.

[0124] A brass plate (length 20 mm x width 20 mm x thickness 1 mm) [manufactured by Kiyokawa Plating Industry Co., Ltd.] as a member to be plated was degreased and washed.

[0125] This brass plate was plated in a plating bath (1) at pH 0.1, a liquid temperature of 28°C, and a current density of 2 A / dm 2 The mixture was plated for 20 minutes under stirring under the above conditions, forming a plating film (copper plating film) made of a copper-ND particle composite material on the brass plate (cathode: brass plate, anode: copper plate). The brass plate with the obtained copper plating film had a uniformly and highly dispersed ND particle and a smooth surface.

[0126] Example 2 A plating bath (2) (PG-ND particle concentration in the plating bath: 0.5 g / L) was obtained in the same manner as in Example 1, except that the amount of the PG-ND particle aqueous dispersion obtained in Preparation Example 1 was changed. A brass plate having a copper plating film was obtained in the same manner as in Example 1, except that the obtained plating bath (2) was used.

[0127] Example 3 A plating bath (3) (PG-ND particle concentration in the plating bath: 0.2 g / L) was obtained in the same manner as in Example 1, except that the amount of the PG-ND particle aqueous dispersion obtained in Preparation Example 1 was changed. A brass plate having a copper plating film was obtained in the same manner as in Example 1, except that the obtained plating bath (3) was used.

[0128] Example 4 A plating bath (4) (PG-ND particle concentration in the plating bath: 0.1 g / L) was obtained in the same manner as in Example 1, except that the amount of the PG-ND particle aqueous dispersion obtained in Preparation Example 1 was changed. A brass plate having a copper plating film was obtained in the same manner as in Example 1, except that the obtained plating bath (4) was used.

[0129] Example 5 A plating bath (5) (PG-ND particle concentration in the plating bath: 0.05 g / L) was obtained in the same manner as in Example 1, except that the amount of the PG-ND particle aqueous dispersion obtained in Preparation Example 1 was changed. A brass plate having a copper plating film was obtained in the same manner as in Example 1, except that the obtained plating bath (5) was used.

[0130] Example 6 A plating bath (6) (PG-ND particle concentration in the plating bath: 0.01 g / L) was obtained in the same manner as in Example 1, except that the amount of the PG-ND particle aqueous dispersion obtained in Preparation Example 1 was changed. A brass plate having a copper plating film was obtained in the same manner as in Example 1, except that the obtained plating bath (6) was used.

[0131] Example 7 A plating bath (7) (PG-ND particle concentration in the plating bath: 0.001 g / L) was obtained in the same manner as in Example 1, except that the amount of the PG-ND particle aqueous dispersion obtained in Preparation Example 1 was changed. A brass plate having a copper plating film was obtained in the same manner as in Example 1, except that the obtained plating bath (7) was used.

[0132] Comparative Example 1 A brass plate having a copper plating film was obtained in the same manner as in Example 1, except that a copper plating solution (trade name "Electrolytic Plating Solution", manufactured by Kiyokawa Plating Industry Co., Ltd.) plating bath (6) (not including an ND particle dispersion) was used instead of plating bath (1). The plating film formed on the brass plate had an uneven surface and lacked smoothness.

[0133] <Gloss measurement> The glossiness of the plating films obtained in Examples 1 to 7 and Comparative Example 1 was measured using a gloss meter "High Gloss Gloss Checker IG-410" (manufactured by Horiba, Ltd.) under the following conditions: glossiness m0 (specular reflectance 100%).

[0134] Light source: LED (wavelength: 890nm) Incident angle: 60° (for 100% reflection, gloss is 1000 (no unit)) The results are summarized in Table 1 below.

[0135] From Table 1 below, it can be seen that the addition of ND particles increases the glossiness of the copper plating film surface.

[0136] [Table 1]

[0137] 2 (Comparative Example 1) and 3 (Example 4) show the X-ray diffraction results immediately after production and 7 days after production of the plating films formed on the brass plates in Example 4 and Comparative Example 1. The copper plating film of Comparative Example 1 showed copper oxide (CuO) peaks after 1 week and was colored reddish-brown, but the copper plating film of Example 4 did not show any copper oxide (CuO) peaks even after 1 week, and no difference was observed with the naked eye between immediately after production and 7 days after production.

[0138] These results demonstrate that hydrophilic ND particles can suppress the oxidation of base metal plating films.

[0139] Comparative Example 2 Non-hydrophilic PG-unmodified ND was added to a copper plating bath (Kiyokawa Plating Co., Ltd.) at 200 ppm. The concentration of ND (Daicel Co., Ltd., before PG modification) added was the same as in the case with PG. Plating was performed under the same conditions as in Example 1 using PG-modified ND while stirring. The same samples were used to confirm the gloss and antioxidant effect. The gloss of the resulting plating films (Comparative Example 2, Examples 3 and 4) was measured immediately after production, and the results are shown in Table 2. The gloss of the copper plating using PG-unmodified ND was comparable to that without ND, and a clear difference was observed compared to the gloss when PG-modified ND was added. Furthermore, XRD measurements were performed on the copper plating film of Comparative Example 2 immediately after plating and five days later. The results are shown in Figure 4. Copper oxide was observed five days after plating film production, and the antioxidant effect observed with PG-ND particles was not observed.

[0140] [Table 2]

[0141] [Test Example 1] Copper plating baths were prepared in the same manner as in Example 1, except that the concentrations of PG-ND particles in the copper plating bath were changed to 0 ppm, 200 ppm (0.02%), 400 ppm (0.04%), 600 ppm (0.06%), and 1000 ppm (0.1%), and the haze was measured. The results are shown in Table 3.

[0142] [Table 3]

[0143] [Test Example 2] In Preparation Example 1, the PG-unmodified ND particles obtained by the detonation method were subjected to crystal structure analysis using an X-ray diffraction apparatus (product name "Smart Lab", manufactured by Rigaku Corporation). As a result, a strong diffraction peak was observed at the diffraction peak position of diamond, i.e., the diffraction peak position from the (111) plane of the diamond crystal, confirming that the PG-unmodified ND particles were diamond.

[0144] Next, the PG-unmodified ND particles and PG-ND particles obtained in Preparation Example 1, as well as the ND particles (PG-unmodified and PG-modified) obtained by the shock compression method, were subjected to small-angle X-ray scattering measurement (SAXS method) using an X-ray diffractometer (trade name "Smart Lab", manufactured by Rigaku Corporation), and the primary particle diameter of the nanodiamonds was estimated in the scattering angle range of 1° to 3° using particle size distribution analysis software (trade name "NANO-Solver", manufactured by Rigaku Corporation). In this estimation, the primary particle diameter of the nanodiamonds was estimated for a spherical nanodiamond particle with a particle density of 3.51 g / cm. 3 It was assumed that the ND particles obtained by the shock compression method were SCM Nanodia, a product of Sumiishi Materials Co., Ltd., and the PG-modified ND particles obtained by the shock compression method were the above ND particles modified with PG in the same manner as in Preparation Example 1. The results of measuring the particle size using the SAXS method are shown in Table 4.

[0145] [Table 4]

[0146] [Test Example 3] The plating films obtained in Example 1 (copper plating solution containing 200 ppm of PG-ND), Comparative Example 1 (plating solution containing no ND), and Comparative Example 2 (plating solution containing PG-unmodified ND) were measured for the diffraction peak of the 111 plane of copper oxide immediately after plating, 5 days after plating, and 7 days after plating by grazing incidence X-ray diffraction as follows.

[0147] (1) Small angle incidence X-ray diffraction method Grazing incidence X-ray diffraction (GIXD) was used to analyze the surface structure of the copper-plated surface. This method utilizes the phenomenon that total reflection occurs when X-rays are incident very close to the flat surface of a material, and measures reflection, refraction, and diffraction by slightly changing the angle around the angle at which total reflection occurs. In this study, measurements were taken using a SmartLab (manufactured by Rigaku Corporation) with an incident angle of approximately 0.7° and a measurement angle of 30° to 100°.

[0148] (2) Storage conditions for plating film The brass plates having copper plating films obtained in Example 1 and Comparative Examples 1 and 2 were stored for 5 days or 1 week in a room away from direct sunlight (room temperature of about 25°C, humidity of about 50%).

[0149] (3) Measurement results The results are shown in Table 5.

[0150] [Table 5]

[0151] After 7 days, the peak intensity of the copper oxide 111 plane relative to the peak intensity of the copper 111 plane was 2.5% in the case without ND (Comparative Example 1), whereas the copper oxide peak was 0.1% in the case of the PG-modified ND (Example 3).

[0152] Example 8 and Comparative Example 3 Using the following tin (Sn) plating solution, brass plates were plated with Sn in the same manner as in Example 1 (PG-ND particle concentration in the Sn plating bath: 0.2 g / L (Example 8) or 0 g / L (Comparative Example 3)), to obtain brass plates with Sn-plated films. The gloss and surface roughness (Ra) of the obtained brass plates with Sn-plated films were measured, and the results are shown in Table 6. Sn plating Liquid composition: stannous sulfate 30g / L, sulfuric acid 130g / L Plating temperature: 10℃ Current density: 2A / dm 2 Plating time: 10 minutes

[0153] Example 9 and Comparative Example 4 Using the following nickel (Ni) plating solution and plating conditions, Ni plating of brass plates was carried out in the same manner as in Example 1 (PG-ND particle concentration in the Ni plating bath: 0.2 g / L (Example 9) or 0 g / L (Comparative Example 4)), to obtain brass plates with Ni plating films. The gloss and surface roughness (Ra) of the obtained brass plates with Ni plating films were measured, and the results are shown in Table 6. Nickel plating Solution composition: Nickel sulfate 250g / L, nickel chloride 40g / L, boric acid 30g / L Plating temperature: 50℃ Current density: 2A / dm 2 Plating time: 25 minutes

[0154] Example 10 and Comparative Example 5 Using the following zinc (Zn) plating solution and plating conditions, Zn plating of brass sheets was carried out in the same manner as in Example 1 (PG-ND particle concentration in the Zn plating bath: 0.2 g / L (Example 10) or 0 g / L (Comparative Example 5)), to obtain brass sheets with a Zn plating film. The gloss and surface roughness (Ra) of the obtained brass sheets with a Zn plating film were measured, and the results are shown in Table 6. Zinc plating Solution composition: zinc oxide 10g / L, sodium hydroxide 100g / L Plating temperature: Room temperature Current density: 2A / dm 2 Plating time: 18 minutes

[0155] [Example 11 and Comparative Example 6] Using the following permalloy (Ni-Fe alloy) plating solution and plating conditions, permalloy plating of brass plates was carried out in the same manner as in Example 1 and Comparative Example 1 (PG-ND particle concentration in permalloy plating bath: 0.2 g / L (Example 11) or 0 g / L (Comparative Example 6)), to obtain brass plates with permalloy plating films. The gloss and surface roughness (Ra) of the obtained brass plates with permalloy plating films were measured, and the results are shown in Table 6. Permalloy plating Solution composition: Nickel sulfate 250g / L, nickel chloride 40g / L, boric acid 30g / L, ferrous sulfate 24g / L, malonic acid 5g / L, Plating temperature: 50℃ Current density: 2A / dm 2 Plating time: 25 minutes

[0156] <Surface roughness (Ra) measurement> The surface roughness (Ra) of the plating films obtained in Examples 8 to 11 and Comparative Examples 3 to 6 was measured using a high-precision shape measurement system KS-1100 (manufactured by KEYENCE Corporation).

[0157] [Table 6]

[0158] It has been revealed that adding PG-ND particles to various plating solutions can improve the gloss, surface smoothness, and indentation hardness (surface hardness) of the plating film. Low surface roughness (Ra) is thought to be related to improved gloss.

[0159] Test Example 4 The indentation hardness (surface hardness) of the plating films obtained in Examples 3, 9, and 11, and Comparative Examples 1, 4, and 6 was measured using a microindentation hardness tester (product name "ENT-2100", manufactured by Elionix Co., Ltd.) under the following conditions. Indenter: Berkovich indenter Loading conditions: (i) Starting load 0mN → Load 20mN, 10s (ii) Starting load 20mN → Load 20mN, 10s (iii) Starting load 20mN → Ending load 0mN, 10s microhardness tester The results are shown in Table 7.

[0160] [Table 7]

[0161] Example 12 A plating bath (12) (PG-ND particle concentration in the plating bath: 0.02 g / L) was obtained in the same manner as in Example 1, except that the amount of the PG-ND particle aqueous dispersion obtained in Preparation Example 1 was changed. Using the obtained plating bath (12), a stainless steel plate having a copper plating film was obtained in the same manner as in Example 1, except that the brass plate was replaced with a stainless steel plate.

[0162] Comparative Example 7 A stainless steel plate having a copper plating film was obtained in the same manner as in Comparative Example 1, except that the plating bath (6) of Comparative Example 1 was used and the brass plate was replaced with a stainless steel plate.

[0163] Test Example 5 The copper plating films were peeled off from the stainless steel plates obtained in Example 12 (using a copper plating solution containing 20 ppm of PG-ND) and Comparative Example 7 (using a plating solution containing no ND), and the plating films were placed on glass plates to measure the thicknesses of the plating films with a micrometer, and the electrical conductivity was measured under the following conditions. Conductivity measuring device: Loresta GX, manufactured by Mitsubishi Chemical Analytech Sample size: 1cm 2 Measurement points: top, bottom, left, right, and center (5 points) Measurement method: The plating film is peeled off from the stainless steel plate and measured on a separately prepared glass plate.

[0164] Specifically, the thickness of the plating film measured with a micrometer was input into the Loresta GX, and the volume resistivity was measured (four-point terminal method). The volume resistivity was measured using annealed standard soft copper (volume resistivity: 1.7241 x 10 -2 The conductivity was converted to electrical conductivity, with the conductivity in μΩm being 100% IACS. The results are shown in Table 8.

[0165] [Table 8]

[0166] It was revealed that the conductivity of copper plating produced from a plating bath containing the hydrophilic nanodiamonds of the present invention (PG-ND) was improved compared to copper plating without the addition of the nanodiamonds. The base metal plating film of the present invention to which hydrophilic nanodiamond (PG-ND) has been added has the unexpected effect of preventing an increase in crystallite size, maintaining hardness, and improving electrical conductivity.

[0167] Test Example 6 The crystallite sizes of the 111 and 220 planes were measured for the copper plating films obtained in Example 3 (copper plating solution containing 200 ppm of PG-ND) and Comparative Example 1 (copper plating solution containing no ND). The crystallite sizes were measured by X-ray diffraction (XRD) using CuKα radiation as the X-ray source, and calculated using the Scherrer equation from the half-width and diffraction angle of the diffraction peak. The measurement equipment used was a Rigaku SmartLab, and the optical system used was the focusing method. The results are shown in Table 9. The XRD patterns of the copper plating films are shown in Figure 5, and the peak intensity ratios of the 111 and 220 planes are shown in Table 10.

[0168] [Table 9]

[0169] [Table 10]

[0170] It was revealed that the copper plating film containing PG-ND obtained in Example 3 had small crystallite sizes in both the 111 and 220 planes and was excellent in indentation hardness (surface hardness).

[0171] Test Example 7 For the plating films obtained in Example 9 (nickel plating solution containing 200 ppm of PG-ND) and Comparative Example 4 (nickel plating solution containing no ND), the crystallite sizes of the 111 and 200 planes of the nickel plating were measured three months after plating. The crystallite size was measured by X-ray diffraction (XRD) using CuKα radiation as the X-ray source, and calculated using the Scherrer equation from the half-width and diffraction angle of the diffraction peak. The measuring device used was a Rigaku SmartLab, and the optical system used was the focusing method. The results are shown in Table 11.

[0172] [Table 11]

[0173] It was revealed that the nickel plating film containing PG-ND obtained in Example 9 had small crystallite sizes in both the 111 and 200 planes and was excellent in indentation hardness (surface hardness).

[0174] Test Example 8 For the plating films obtained in Example 9 (nickel plating solution containing 200 ppm of PG-ND) and Comparative Example 4 (nickel plating solution containing no ND), cross sections were prepared using a focused ion beam processing device and observed using backscattered electron images. Device name: FIB-SEM device (FEI Versa3D DualBeam). Figure 6(a) shows the plating film of Comparative Example 1 that does not contain ND particles, and it can be seen that the surface roughness (Ra) is large. Figure 6(b) shows the plating film of Example 1 that contains ND particles, and the small black dots indicated by arrows are ND particles.

[0175] Test Example 9 For the plating film obtained in Example 1 (copper plating solution containing 200 ppm of PG-ND), the carbon content (C1s) in the Cu plating film was measured by X-ray photoelectron spectroscopy (XPS) using an ULVAC-PHI (PHI5800 ESCA system). The results are shown in Figure 7. Carbon was detected in the Cu film. [Explanation of symbols]

[0176] 1. ND particles with surface-modified groups 2 ND particles (partial) 3 Surface modification group

Claims

1. A base metal plating bath comprising base metal ions and hydrophilic nanodiamond particles, the concentration of the hydrophilic nanodiamond particles being 0.01 to 0.5 g / L.

2. 2. The base metal plating bath according to claim 1, wherein the haze is from 0 to 0.

5.

3. 3. The base metal plating bath according to claim 1, wherein the particle size (D10) of the hydrophilic nanodiamond particles in the base metal plating bath is 10 to 60 nm.

4. 3. The base metal plating bath according to claim 1, wherein the particle size (D50) of the hydrophilic nanodiamond particles in the base metal plating bath is 10 to 70 nm.

5. 3. The base metal plating bath according to claim 1, wherein the particle size (D90) of the hydrophilic nanodiamond particles in the base metal plating bath is 10 to 90 nm.

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