JP7626414B2 - Method for analyzing and controlling nanodiamond particle concentration in composite plating solution - Google Patents

Description

The present invention relates to a method for analyzing and managing the concentration of nanodiamond particles in a composite plating solution.

In this specification, nanodiamonds may be referred to as "ND."

A composite plating solution in which nanodiamond particles are mixed and dispersed in a normal plating solution is known (Patent Document 1). By using a composite plating solution containing nanodiamond particles, a plating film in which the nanodiamond particles are uniformly dispersed is formed, improving the design, mechanical properties, and functionality of the plating film.

In order to reproducibly form a plating film with the desired characteristics using such a composite plating solution, it is necessary to control the concentration of nanodiamond particles in the composite plating solution, add nanodiamond particles to the composite plating solution appropriately so that this concentration becomes the desired concentration, and maintain and control the nanodiamond particle concentration.

The concentration of nanodiamond particles in a composite plating solution can be estimated, for example, by quantifying the amount of nanodiamond particles in the plating film, but this method requires complicated operations.

JP 2018-83960 A

The object of the present invention is to quickly and accurately analyze the concentration of nanodiamond particles in a composite plating solution using a simple method, and to appropriately manage the composite plating solution.

The present invention provides the following method for analyzing and controlling the concentration of nanodiamond particles in a composite plating solution.
[1] A method for analyzing the concentration of nanodiamond particles in a composite plating solution, comprising the steps of measuring the absorbance of a composite plating solution containing nanodiamond particles and determining the concentration of the nanodiamond particles based on the measured absorbance, wherein the absorbance is measured at a wavelength selected from the range of 250 to 630 nm.
[2] A method for controlling the concentration of nanodiamond particles in a composite plating solution, comprising analyzing the concentration of nanodiamond particles in the composite plating solution using the method of [1], and adding nanodiamond particles to the composite plating solution as necessary so that the concentration becomes a predetermined concentration.

According to the present invention, the concentration of nanodiamond particles in a composite plating solution can be analyzed easily and quickly, and according to the method of managing the composite plating solution of the present invention that utilizes this analysis method, the analytical value of the concentration of nanodiamond particles can be reflected in the control of the addition of nanodiamond particles in real time, making it possible to easily obtain a composite plating film with the desired characteristics while maintaining and managing the plating process well.

Absorbance of copper plating solution (ND=0 ppm) without the addition of nanodiamond particles. Absorbance of copper plating solution (ND=50-1000ppm) to which nanodiamond particles have been added at a specified concentration. Absorbance of nanodiamond water dispersion (50 ppm, 500 ppm). Calibration curve for copper plating solution with various concentrations of nanodiamond particles (ND=300-360ppm) added. Absorbance of nickel plating solution without added nanodiamond particles (ND=0 ppm). Absorbance of nickel plating solution (ND=50-1000ppm) to which nanodiamond particles have been added at a specified concentration.

In this specification, the composite plating bath contains a base metal plating solution and nanodiamond particles (ND particles). The concentration of the 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 of the concentration of the ND particles is preferably 0.8 g/L, more preferably 0.6 g/L, and particularly preferably 0.5 g/L), and is preferably 0.01 to 0.5 g/L.

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, rhenium, and thallium, preferably at least one selected from the group consisting of copper, nickel, zinc, tin, chromium, and permalloy, more preferably at least one selected from the group consisting of copper, nickel, zinc, and tin, and particularly preferably copper and nickel.

The particle size (D50) of the ND particles in the composite plating solution 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 ND particles is, for example, 20 nm.

Base metal plating solutions are known, and a composite plating bath can be obtained by adding ND particles or a dispersion thereof to a known base metal plating solution. The dispersion of ND particles is preferably an aqueous solution. The composite plating bath may be either an electrolytic composite plating bath or an electroless composite plating bath. The composite plating bath contains a water-soluble base metal salt and ND particles as essential components, and may further contain other components selected from electrical conductivity salts, complexing agents, reducing agents (electroless plating baths), anode dissolution accelerators (in the case of composite electrolytic plating baths), phosphorus sources (in the case of electroless nickel-phosphorus alloy plating), pH buffers, surfactants, stabilizers, and additives for adjusting the appearance and physical properties of the film (brightening agents, smoothing agents, stress reducers, etc.). The water-soluble base metal salt exists as a base metal ion in the base metal plating bath. In addition, it may exist as an oxygen acid ion of the base metal or a base metal complex ion bound to a complexing agent. The concentration of the water-soluble base metal salt in the composite plating bath is, for example, 0.01 to 0.5 mol/L, preferably 0.05 to 0.2 mol/L, calculated as the base metal ion concentration supplied to the composite plating solution.

Examples of reducing agents contained in the electroless composite plating solution include phosphonic acid or phosphonates (e.g., alkali metal phosphonates such as sodium phosphonate), phosphinic acid or phosphinates (e.g., alkali metal phosphinates such as sodium phosphinate), etc. When a phosphinate or phosphonate is used as the reducing agent, the concentration of the phosphinate or phosphonate in the electroless composite plating solution is, for example, 0.02 to 0.5 mol/L, and preferably 0.1 to 0.2 mol/L.

Examples of complexing agents contained in the electrolytic and electroless base metal plating baths include citric acid, lactic acid, malic acid, glycolic acid, and salts thereof. Citric acid includes alkali metal citrates such as 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.

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

In the present invention, the ND particles are controlled among the components of these composite plating solutions. Components other than ND particles can be controlled according to conventional methods.

In a preferred embodiment of the present invention, examples of plating solutions for plating base metals other than ND particles include base metal sulfate plating solutions consisting of ND particles, base metal sulfates, sulfuric acid, chloride ions, etc.; cyanide base metal plating solutions consisting of base metal cyanides, sodium cyanide, alkali carbonates, Rochelle salts, etc.; and pyrophosphate base metal plating solutions consisting of base metal pyrophosphates, potassium pyrophosphate, ammonia water, potassium nitrate, etc.

The surface of the ND particles may have hydrophilic functional groups such as OH, COOH, and _NH2 . In addition, ND particles to which hydrophilic groups have been introduced via these functional groups may be used. Examples of hydrophilic groups include glycerin, polyglycerin (PG), _C2-4 alkylene glycols such as ethylene glycol, propylene glycol, and butylene glycol, and poly( _C2-4 alkylene glycols) such as polyethylene glycol, polypropylene glycol, and polybutylene glycol. These hydrophilic ND particles are publicly known or can be produced by publicly known methods.

The ND particles may be mixed into the (composite) plating bath as a solid, or an ND particle dispersion may be mixed into the (composite) plating bath. The ND particle concentration in the ND particle dispersion is, for example, about 1 to 100 g/L.

As the ND particles, hydrophilic ND particles coated or modified with a hydrophilic polymer are preferred because of their excellent dispersibility, and hydrophilic ND particles having a water-soluble polymer containing a polyglycerin chain are particularly preferred.

The ND particle concentration in the composite plating solution of the present invention can be analyzed as follows.
(i) First, for a composite plating solution in which the concentration of ND particles is to be analyzed, multiple types of composite plating solutions with known ND particle concentrations are prepared by blending ND particles in various amounts within the range in which the ND particle concentration is to be controlled.
(ii) Next, the absorbance of each of the composite plating solutions prepared in (i) above is measured.
(iii) Based on the results of (ii) above, a calibration curve showing the relationship between the absorbance of the composite plating solution and the ND particle concentration is prepared, as shown in FIG.

The wavelength for measuring the absorbance of the composite plating solution is selected from the range of 250 to 630 nm, and within this range, a calibration curve can be created at any wavelength to analyze the ND particle concentration in the composite plating solution. The wavelength for creating the calibration curve is preferably a wavelength at which the absorbance change is large when the concentration of ND particles is increased, with the plating solution not containing ND as the reference. For example, in the case of the copper plating solution shown in Figures 1 to 3, the wavelengths are preferably 280 nm to 630 nm, more preferably 300 nm to 600 nm, and even more preferably 310 nm to 500 nm. In the case of the nickel plating solution shown in Figures 5 to 6, the wavelengths are preferably 300 nm to 370 nm and 430 nm to 580 nm, more preferably 305 nm to 360 nm and 440 nm to 560 nm, and even more preferably 310 nm to 350 nm and 440 nm to 550 nm. Even in the case of copper plating solution and nickel plating solution, if the components and concentrations contained in the plating solution change, the preferred wavelength for creating the calibration curve may change. In addition, when the type of base metal in the base metal plating solution is changed from copper and nickel to other base metals such as iron, zinc, tin, aluminum, tungsten, molybdenum, tantalum, magnesium, cobalt, bismuth, cadmium, titanium, zirconium, antimony, manganese, beryllium, chromium, germanium, vanadium, gallium, hafnium, indium, niobium, rhenium, and thallium, the preferred wavelength for creating the calibration curve may also change. The preferred wavelength for creating the calibration curve can be easily determined by referring to the results of the copper plating solution and the nickel plating solution. The calibration curve may be created using only one wavelength, or may be created using multiple wavelengths (preferably two or three wavelengths). As shown in FIG. 3, the absorbance of the aqueous dispersion of ND particles is also greatly affected by the concentration of ND particles, so it is preferable to determine the wavelength for creating the calibration curve taking this into consideration. Within the range of the ND particle concentration to be managed, the measurement wavelength of absorbance advantageous for determining the ND particle concentration is determined by the calibration curve. The concentration of ND particles in the composite plating solution can be analyzed by the absorbance measurement value using a previously prepared calibration curve. The analysis of the ND particle concentration can be performed to specify the concentration of ND particles, or it can be analyzed in a concentration zone so that it can be determined whether the ND particle concentration may deviate from the acceptable range and whether ND particles should be added to the composite plating solution, for example in the form of an aqueous dispersion.

In the method for managing the ND particle concentration of the composite plating solution of the present invention, the composite plating solution is sampled from the plating tank, and the concentration of ND particles in the composite plating solution is analyzed by the method described above. If it is determined based on the analysis results that the ND particle concentration will remain within the allowable range until the next sampling, no ND particles are added, and if it is determined based on the analysis results that the ND particle concentration may be outside the allowable range at the time of the next sampling, ND particles are added to the composite plating solution in the plating tank as necessary, for example in the form of an aqueous dispersion, so that plating is performed with the ND particle concentration within the allowable range.

Regarding the ND concentration management method of the present invention, for example, the concentration of ND particles may be automatically managed by a system equipped with a sampling means for sampling the plating solution from the composite plating solution using a pump or the like, an analysis means for measuring the absorbance of the sampled sample, a control means for receiving a signal from the analysis means and deciding whether or not to add ND particles to the composite plating solution and the amount to be added, and an ND particle addition means for controlling the addition of ND particles by the control means. Alternatively, a manager may manually sample the composite plating solution and measure the absorbance at appropriate times while observing the plating status, and based on the results, determine whether or not ND particles need to be added to the composite plating solution, and if so, the amount to be added.

The present invention will now be described in more detail with reference to examples.
Example 1
Composite plating solutions with various ND concentrations were prepared by adding an aqueous dispersion of ND particles (PG-ND particle aqueous dispersion (manufactured by Daicel Corporation)) that had been hydrophilized by modification with polyglycerin (PG) to a copper plating solution (product name "Electrolytic Plating Solution" manufactured by Kiyokawa Plating Co., Ltd.) so that the PG-ND concentrations in the copper plating solution were 0, 50, 100, 200, 300, 400, 500, and 1000 ppm.

The absorbance of the obtained composite copper plating solution was measured at wavelengths of 300 nm, 310 nm, 320 nm, 330 nm, 340 nm, 350 nm, 355 nm, and 360 nm using a spectrophotometer (U-3900H Spectrophotometer, Hitachi High-Tech Fielding Corporation), and a calibration curve was created (Figure 4). Figure 1 shows the absorbance measurement results of the copper plating solution to which no PG-ND was added, and Figure 2 shows the absorbance measurement results of the copper plating solutions to which PG-ND was added at 50 ppm, 100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, and 1000 ppm. Figure 3 shows the absorbance of the PG-ND aqueous dispersion when the PG-ND concentration was 50 ppm and 500 ppm.

The results in Figure 4 show that the concentration of ND particles can be determined by absorbance, and that the concentration of ND particles in the composite plating solution can be appropriately controlled.

Example 2
Composite plating solutions with various ND concentrations were prepared by adding an aqueous dispersion of ND particles (PG-ND particle aqueous dispersion (manufactured by Daicel Corporation)) that had been hydrophilized by modification with polyethylene glycol (PG) to a nickel plating solution (product name "Electrolytic Nickel Plating Solution" manufactured by Kiyokawa Plating Co., Ltd.) so that the PG-ND concentrations in the copper plating solution were 0, 50, 100, 200, 300, 400, 500, and 1000 ppm.

The absorbance of the resulting composite copper plating solution was measured using a spectrophotometer. Figure 5 shows the absorbance of the copper plating solution to which no PG-ND was added, and Figure 6 shows the absorbance of the copper plating solution to which PG-ND was added at 50 ppm, 100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, and 1000 ppm.

The results in Figures 5 and 6 show that the concentration of ND particles can be determined by absorbance, and that the concentration of ND particles in the copper plating solution can be appropriately controlled.

Claims (2)

The method includes a step of measuring the absorbance of a composite plating solution containing nanodiamond particles and a base metal , and determining the concentration of the nanodiamond particles based on the measured absorbance;
the base metal is copper or nickel;
When the base metal is copper, the wavelength for measuring absorbance is selected from the range of 310 nm to 500 nm;
When the base metal is nickel, the wavelength for measuring absorbance is selected from the ranges of 300 nm to 370 nm and 430 nm to 580 nm . A method for managing the concentration of nanodiamond particles in a composite plating solution, which comprises analyzing the concentration of nanodiamond particles in the composite plating solution using the method of claim 1, and adding nanodiamond particles to the composite plating solution as necessary so that the concentration becomes a predetermined concentration.