JP4324672B2 - Diamond electrode, method for controlling electroless nickel plating bath using the same, and measuring device - Google Patents

Description

  The present invention relates to a diamond electrode, a method for managing an electroless plating bath using the same, and a measuring apparatus, and more particularly, a diamond electrode suitable for nickel concentration management in a nickel electroless bath and an electroless plating bath using the same. It relates to management methods.

  The electroless plating method is widely applied in various fields as a method for forming a thin film on metal or various materials, and in particular, electroless nickel plating is one of the most studied and put into practical use. . In recent years, it is also used as a technique for forming conductor patterns, through holes, vias, and the like in the manufacture of semiconductor devices, and the demand for plating quality is increasing due to the need for improved reliability.

  In the case of electroless nickel plating, nickel-phosphorus (Ni-P) alloy plating can be obtained by using hypophosphite as the reducing agent, and nickel-boron (Ni-B) alloy plating can be obtained by using boron compounds. . Nickel-phosphorus alloy plating using hypophosphite as a reducing agent has excellent mechanical, electrical, and physical characteristics, and can uniformly coat plating films on products with complex shapes. Because of its characteristics, it is used in various fields. On the other hand, Ni-B alloy plating using a boron compound such as dimethylaminoboron (DMAB) as the reducing agent is difficult to even form an oxide film on the plating film. Although the rate is significantly lower than Ni-P alloy plating, on the other hand, the plating bath is unstable and difficult to manage, and the cost is high. It is currently used for special purposes.

  In such electroless nickel plating, the management of the nickel concentration in the plating bath is an extremely important item. When electroless nickel plating is performed, the nickel component is consumed and its concentration gradually decreases. To maintain the nickel concentration at the default value, it is necessary to replenish the nickel component as needed according to the amount consumed. There is. At this time, components other than the nickel component are generally replenished in proportion to the replenishment amount of the nickel component as an index.

  Conventionally, spectrophotometry has been mainly used as a method for analyzing the nickel concentration in such an electroless nickel plating bath. For example, the absorbance is measured by periodically sampling the plating solution from the plating bath, and the concentration is measured by comparing the obtained absorbance value with a previously prepared calibration curve (Ni-B concentration vs. absorbance). It was.

The electroless nickel plating solution contains various complexing agents, the nickel component exists as nickel complex ions, and the nickel complex strongly absorbs light in the green wavelength range, and absorbs light in this wavelength range. There is a good proportional relationship in nickel concentration. Quantitative analysis as described above has been performed using this feature. In order to perform measurement in a specific wavelength range, it is necessary to split light, but many of the apparatuses employ a method of selecting light with an interference filter. In addition, a method of obtaining a wavelength very close to monochromatic light using a monochromator using a diffraction grating or a prism is also known.
JP 2002-322598 A

  However, the method of measuring the nickel concentration using the above-described spectrophotometric method is mechanically complicated, relatively expensive, and has a problem that it takes a relatively long time for the measurement. It was desired.

  Patent Document 1 proposes a method for electrochemically measuring the concentration of a plating component in a plating solution. However, the electroless nickel plating solution contains metal salts, reducing agents, complexing agents, additives, and the like. Due to these effects, it is difficult to determine the nickel concentration, and an easy and reproducible measurement method is not available. It was requested. Also, in the electrochemical measurement method, the working electrode (sensor electrode) used for the measurement becomes an object to be plated and is exposed to an acid or alkali solution when repeating the measurement operation, so the corrosion resistance against acid or alkali is good. In addition, an electrode that can be measured stably for a long period of time with good reproducibility is also required.

  The present invention has been made to solve the above-described problems in the prior art, and is an electroless nickel plating bath capable of quantifying the nickel concentration in the nickel electroless plating bath by a cheaper and quicker technique. It is an object of the present invention to provide a working electrode and a measuring apparatus, and a working electrode which can be used for such a plating bath management and can be measured with stability and reproducibility for a long time.

An electrode according to the present invention for achieving the above object is an electrode used as a working electrode for electrochemical Ni concentration measurement of an electroless nickel plating bath, and a boron dose is 1 × 10 ¹⁹ to 2 ×. A boron-doped diamond electrode characterized by 10 ¹⁹ atoms / cm ³ .

  In the present invention, a boron-doped diamond electrode which is a revolving electrode is further shown.

  The management method of the electroless nickel plating bath according to the present invention for achieving the above object uses a working device comprising a boron-doped diamond electrode, and a measuring device comprising a counter electrode and a reference electrode connected to a potentiostat, These electrodes are immersed in a sample solution obtained by diluting a sample collected from an electroless nickel plating bath to a predetermined concentration. (1) In the sample solution, the electrode potential of the working electrode is changed to the Ni ion in the sample solution. (2) Next, in the sample solution, the electrode potential of the working electrode is set in the sample solution, and the deposited Ni surface becomes nickel oxyhydroxide (NiOOH). (3) Further, in the sample solution, the electrode potential of the working electrode is determined based on the differential pulse voltammetry method in the step (2). By scanning the potential to the predetermined potential using the electrode potential of the electrode for the start as a starting potential, the voltage-current curve is recorded, the peak current value is read, and this is compared with the calibration curve prepared in advance in the plating bath. The nickel concentration contained in is determined.

  In the management method of the electroless nickel plating bath of the present invention, after the potential of the working electrode is scanned to the predetermined potential, the electrode potential of the working electrode is maintained on the oxidation condition side for a predetermined time in a sulfuric acid aqueous solution having a predetermined concentration. It is desirable to clean the electrodes.

  In the electroless nickel plating bath management method of the present invention, before the working electrode is scanned to the predetermined potential, the electrode potential of the working electrode is set to the predetermined oxidation condition side in an aqueous solution of sodium hydroxide / ammonium nitrate at a specified concentration. It is desirable to hold the time and pre-treat the working electrode.

  The measuring device for electroless nickel plating bath management according to the present invention for achieving the above object, a container for containing a diluted solution of a sample collected from the electroless nickel plating bath, and disposed in the container, A measuring apparatus for electroless nickel plating bath management comprising at least a working electrode composed of a boron-doped diamond electrode, a counter electrode and a reference electrode, and a potentiostat to which each electrode is connected.

  According to the present invention, it is possible to calibrate nickel in an electroless nickel plating bath more inexpensively and rapidly by an electrochemical method using a boron-doped diamond electrode as a working electrode. The electroless nickel plating bath contains metal salts, reducing agents, complexing agents, various additives, etc., so it is expected that the determination of the amount of nickel by an electrochemical method is extremely difficult. In the present invention, the amount of nickel can be quantified with high accuracy by using the above-described three-stage method with less influence. Furthermore, as a working electrode, a boron-doped diamond electrode that is excellent in stability in acid and alkaline solutions can be a sensor electrode that is stable and reproducible in the long term in the determination of the amount of nickel in an electroless nickel plating bath. Therefore, stable management of the electroless nickel plating bath over a long period of time becomes possible.

  Hereinafter, the boron-doped diamond electrode of the present invention, the management method of an electroless nickel plating bath using the same, and the measurement device for management will be described in detail based on specific embodiments.

(Boron doped diamond electrode)
The present invention is an electrode used as a working electrode for electrochemical Ni concentration measurement of an electroless nickel plating bath, wherein the boron dose is 1 × 10 ¹⁹ to 2 × 10 ¹⁹ atoms / cm ^3. It is a boron-doped diamond electrode characterized.

  The boron-doped diamond electrode according to the present invention is not particularly limited, but can be produced by a microwave plasma CVD (Chemical Vapor Deposition) method. Specifically, a base material such as single crystal silicone having a predetermined shape is installed in a vacuum chamber, hydrogen gas, a carbon source such as acetone, and boron oxide dissolved in methanol are mixed with acetone and then hydrogen gas is bubbled. Then, each is introduced into a chamber and irradiated with microwaves to make these gases into plasma, and a boron-doped diamond thin film is formed on the substrate surface. The formation conditions are not particularly limited. For example, hydrogen gas flow rate: 300 SCCM (at 22 ° C.), bubbling hydrogen gas flow rate: 3.0 SCCM (at 22 ° C.), chamber temperature: 540 ° C., microwave irradiation Conditions: Conditions such as an internal pressure of 70 Torr and an output of 1400 W can be used.

  FIG. 1 (a) is an electron micrograph (magnification 3000 times) of the surface of an example of the boron-doped diamond electrode produced by the microwave plasma CVD method and its drawing, and FIG. 1 (b) is the same. It is the electron microscope photograph (magnification 7000 times) of the surface enlarged, and its drawing. As can be seen in FIG. 1 (b), there are diamond characteristic crystal grains grown in a triangular or quadrangular shape on the surface.

  The thickness of the boron-doped diamond thin film thus obtained is not particularly limited, but for example, about 10 to 20 μm is appropriate.

As described above, the boron-doped diamond electrode according to the present invention is given conductivity because the boron dose is 1 × 10 ¹⁹ to 2 × 10 ¹⁹ atoms / cm ^3. The resistivity ρ is 0.01 to 1.0 Ω · m, more preferably 0.01 to 0.1 Ω · m.

  The boron-doped diamond electrode thus obtained has a wide (1) potential window (potential range in which water in the aqueous solution does not decompose, that is, a range in which electrochemical measurement can be performed in this solution), and (2) charging current It is particularly preferable for measuring the nickel concentration in the electroless nickel plating bath because it is small and (3) very stable in acid and alkaline solutions.

(Measurement device for electroless nickel plating bath management)
Next, the configuration of the measuring apparatus used in the method for managing an electroless nickel plating bath according to the present invention will be described.
FIG. 2 is a diagram showing a configuration example of an electrochemical measurement apparatus used in the method for managing an electroless nickel plating bath according to the present invention. A measuring apparatus 1 according to the present invention includes a container for containing a diluted solution 5 of a sample collected from an electroless nickel plating bath, a working electrode 2 made of a boron-doped diamond electrode, and a counter electrode 4 disposed in the container. And at least a reference electrode 3 and a potentiostat 6 to which those electrodes are connected.

  In this electrochemical measuring apparatus, a so-called three-electrode system is used as the structure of the electrochemical cell. That is, as shown in FIG. 2, in the electrochemical measuring apparatus 1, the electrochemical cell has a potential difference between the working electrode 2 made of the boron-doped diamond electrode, which is a negative electrode and an object to be plated, and the working electrode 2. It consists of a reference electrode 3 for measurement and a counter electrode 4 that is a positive electrode. Each of these electrodes is immersed in the sample solution 5. These electrodes are electrically connected to a potentiostat 6 which is a known device for measuring a three-electrode system. In the configuration example shown in FIG. 2, the potentiostat 6 is connected to a calculation unit 7 configured by, for example, a personal computer that calculates the concentration from the measured data.

  Although it does not specifically limit as the reference electrode 3, For example, a saturated KCl calomel electrode (SCE electrode), a saturated KCl silver-silver chloride electrode, an Ag / AgCl electrode etc. can be used, Preferably it is a SCE electrode. .

  The counter electrode 4 is not particularly limited, but a stable electrode material (an electrode material that does not react with itself) such as a Pt electrode, an Au electrode, a carbon electrode, or the like can be used. A Pt electrode is preferable.

  The potentiostat 6 is used to control the potential of the working electrode 2 so that the potential of the reference electrode 3 does not change (so that no current flows through the reference electrode), and the potential of the working electrode 2 with respect to the reference electrode 3. Can be made to flow a current between the working electrode 2 and the counter electrode 4 so as to be a potential to be set. In addition, the potentiostat 6 is also a device for measuring a current value between the working electrode 2 and the counter electrode 4.

  The measured current value is used as data for determining the concentration of the plating component in the electroless nickel plating bath, as will be described in detail below. That is, the measured current value is analyzed by the calculation unit 6 connected to the potentiostat 1, and the nickel plating component concentration is calculated. Further, the deficiency of the plating component may be calculated by the calculation unit 6 and the data may be sent to a control unit (not shown) to automatically supply the plating component.

  In the configuration example shown in FIG. 2, the working electrode 2 made of a boron-doped diamond electrode is a rotating electrode, and is connected to an appropriate driving device 8 such as a motor. The driving device 8 further includes a rotation control device. 9 is electrically connected, and can be rotated at a constant speed at a predetermined rotational speed, for example, 100 to 5000 rpm, typically 3000 rpm. However, in the present invention, the working electrode 2 made of a boron-doped diamond electrode has a very good sensitivity as described above. Therefore, the working electrode 2 does not necessarily have such a rotating electrode form, but a stationary electrode form. Can be used in combination with a stirrer such as a magnetic stirrer.

(Management method of electroless nickel plating bath)
In the present invention, the nickel concentration in the electroless nickel plating bath is measured using the electrochemical measuring apparatus as described above as described in detail below.

First, prior to actually measuring the nickel concentration in the electroless nickel plating bath, as a pretreatment, the working electrode is subjected to a predetermined concentration of sodium hydroxide / ammonium nitrate aqueous solution for a predetermined time on the oxidation condition side in a prescribed concentration of sodium hydroxide / ammonium nitrate aqueous solution. It is desirable that the holding process be performed. By performing such pretreatment, the working electrode can be kept in a constant state under the condition that nickel is not plated. The concentration of the aqueous solution of sodium hydroxide / ammonium nitrate as a medium to be used is not particularly limited, but an aqueous solution having a molar concentration of about 0.05 to 0.2M, for example, 0.1M NaOH / 0.1M An NH ₄ NO ₃ aqueous solution can be suitably used. Further, the electrode potential of the working electrode may be about 1.5 to 2.4 V, for example, +1.5 V on the basis of the reference electrode (SCE), and held at this potential for 30 to 70 minutes, for example, 30 minutes.

In the present invention, the nickel concentration in the electroless nickel plating bath is measured based on a differential pulse voltammetry method. First, a sample collected from an electroless nickel plating bath is diluted to a predetermined concentration, for example, 1000 to 2000 times, typically 1000 times, for measurement, and a sodium hydroxide / ammonium nitrate aqueous solution, for example, 0.1 M NaOH / An appropriate amount of 0.1M NH ₄ NO ₃ aqueous solution is added to prepare a sample for measurement. For example, in the case of a rotating electrode, 0.3 ml of a diluted plating bath is collected, and a total of 10 ml of electrolysis solution to which sodium hydroxide / ammonium nitrate aqueous solution is added is used as a measurement sample. In the case of a stationary electrode, 0.2 ml of the diluted plating solution is collected, and a total of 10 ml of electrolysis solution to which sodium hydroxide / ammonium nitrate aqueous solution is added is used as a measurement sample.

The sample solution thus prepared is placed in a measurement cell as shown in FIG. 2, and after each electrode is immersed in this cell, first, (1) the electrode potential of the working electrode is measured in the sample solution. The conditions are maintained for a predetermined time at the reducing side conditions where Ni ions in the solution are deposited as Ni on the electrode. As a reduction side condition, a negative potential of about −1.0 to −2.0 V, for example, −2.0 V is set on the basis of the reference electrode (SCE), and this potential is held for 60 to 120 seconds, for example, 60 seconds. Under this condition, the surface of the working electrode is plated with nickel (Ni (II) _solution → Ni 2 _{/ electrode °} ).

Next, (2) in the sample solution, the electrode potential of the working electrode is changed to the oxidation side condition in which the surface of Ni deposited on the working electrode in step (1) becomes nickel oxyhydroxide (NiOOH), that is, Ni ²⁺ is Ni ³⁺ It is kept for a predetermined time at the oxidation side condition to be oxidized. As the oxidation side condition, a positive potential of about +1.0 to +1.5 V, for example, +1.0 V, based on the reference electrode (SCE) is set, for example, +1.0 V, and held at this potential for 60 to 120 seconds, for example, 60 seconds (Ni 2 _{/ electrode} → NiOOH). _{/ Electrode °} ). Thus, by using nickel oxyhydroxide, measurement sensitivity, especially measurement selectivity can be enhanced.

Then, (3) in the sample solution, based on the differential pulse voltammetry method, the electrode potential of the working electrode is scanned to a predetermined potential using the electrode potential of the working electrode in the step (2) as a starting potential, and an elution signal ( NiOOH _{/ electrode} → Ni (OH) _{2 / electrode °} ), that is, a voltage-current curve is recorded and a peak current value is read. Here, the differential pulse voltammetry (DPV) is a method in which a constant pulse voltage is superimposed on a DC voltage that increases or decreases at a constant speed every constant period, as is well known. As a result, a high-resolution peak can be obtained. The potential scanning condition is not particularly limited. For example, from the start potential of the working electrode +1.0 V in the stage (2) to the end potential of +0.2 to −0.2 V, typically Is performed under the conditions of up to 0 V, a sweep speed of 50 mV / second, a pulse voltage of 50 mV, and a pulse interval of 20 ms.

  In this way, the peak current value is read, and this is compared with a calibration curve prepared in advance to determine the nickel concentration contained in the plating bath. The calibration curve is a sample obtained by adding a known amount of nickel to the same medium as used for the measurement so that the concentration becomes several steps, and reading the respective peak current values by operating according to the procedure described above. It is obtained by plotting the value obtained by subtracting the blank peak current value from the peak current value for each nickel concentration.

Furthermore, in the management method of the electroless nickel plating bath of the present invention, the working electrode used for the potential measurement is maintained in the sulfuric acid aqueous solution of the specified concentration at the oxidizing condition side for a predetermined time. Thus, it is desirable to clean the working electrode. The reason for performing such a washing operation is that it has been found that long-term stable and reproducible measurement can be performed as shown in Examples described later. The concentration of the sulfuric acid aqueous solution used for the washing operation is not particularly limited, but an aqueous solution having a molar concentration of about 0.05 to 0.5 M, for example, a 0.1 MH ₂ SO ₄ aqueous solution is preferably used. be able to. Further, as the oxidation side condition, a positive potential of about +1.0 to 2.4 V, for example, +1.0 V, based on the reference electrode (SCE) standard, for example, +1.0 V, and a process of holding this potential for 60 to 120 seconds, for example, 60 seconds is exemplified can do.

  Hereinafter, the present invention will be described more specifically with reference to examples.

(Example 1: Production of boron-doped diamond electrode)
Boron doped diamond electrodes were prepared by microwave plasma CVD. A rotating disk-shaped single crystal silicone substrate is placed in the vacuum chamber of a microwave plasma CVD apparatus (trade name: ASTeX2115, manufactured by Seki Technotron Co., Ltd.), where hydrogen gas, a carbon source such as acetone, and methanol are used. The dissolved boron oxide is mixed with acetone and introduced into the chamber by bubbling hydrogen gas, for example, hydrogen gas flow rate: 300 SCCM (at 22 ° C.), bubbling hydrogen gas flow rate: 3.0 SCCM (at 22 ° C.), chamber Reaction was caused at an internal temperature of 540 ° C., microwave irradiation conditions: an internal pressure of 70 Torr, and an output of 1400 W, and a boron-doped diamond thin film having a thickness of 20 μm was formed on the substrate surface. FIG. 1 (a) is an electron micrograph (magnification 3000 times) of the surface of an example of the boron-doped diamond electrode produced by the microwave plasma CVD method and its drawing, and FIG. 1 (b) is the same. It is the electron microscope photograph (magnification 7000 times) of the surface enlarged, and its drawing.

The obtained boron-doped diamond rotating electrode has a boron dose of 1 × 10 ¹⁹ to 2 × 10 ¹⁹ atoms / cm ³ , and, for example, measured by a four-terminal method has a resistivity of 0.5 Ω · m. Indicated.

  Moreover, the process was performed on the same conditions using the rectangular single crystal silicone which is not a rotating disk shape as a base material, and the stationary electrode was also produced.

(Example 2: Preparation of calibration curve)
Using the boron-doped diamond electrode produced in Example 1 as a working electrode, an electrochemical measurement apparatus as shown in FIG. 2 was constructed.

Working electrode pretreatment; prior to measurement, the boron-doped diamond electrode was held in a 0.1 M NaOH / 0.1 M NH ₄ NO ₃ aqueous solution at a potential of +1.5 V on the basis of the reference electrode (SCE) for 30 minutes. Pre-treatment was performed.

Measurement: (1) A boron-doped diamond electrode was held at −2.0 V for 60 seconds on a reference electrode (SCE) basis in 0.1 M NaOH / 0.1 M NH ₄ NO ₃ aqueous solution containing various known concentrations of Ni. . Next, (2) the electrode potential of the working electrode was set to +1.0 V on the basis of the reference electrode (SCE) in a solution containing the known concentration of Ni and held at this potential for 60 seconds. After that, (3) In the solution containing Ni of the above known concentration, the electrode potential of the working electrode is changed from +1.0 V to 0 V on the basis of the reference electrode (SCE), the sweep speed is 50 mV / sec, the pulse voltage is 50 mV, and the pulse interval is 20 ms. Potential scanning was performed, a voltage-current curve was recorded, a peak current value was read, and a calibration curve was created based on the Ni known concentration of the solution.

  FIG. 3 is a recorded voltage-current curve, and FIG. 4 shows the calibration curve obtained. 3 and 4, (a) shows data when a rotating electrode is used as the boron-doped diamond electrode, and (b) shows that the solution was stirred as a stationary electrode. The case data is shown. As shown in FIG. 4, in any case, a linear calibration curve was obtained.

Cleaning of the working electrode; after the measurement of each sample solution, the boron-doped diamond electrode was held in a 0.1 MH ₂ SO ₄ aqueous solution at +1.0 V on the basis of the reference electrode (SCE) for 60 seconds, and the cleaning treatment was performed. It was given.

(Example 3: Sample measurement)
Using the boron-doped diamond electrode produced in Example 1 as a working electrode, an electrochemical measurement apparatus as shown in FIG. 2 was constructed.

Working electrode pre-treatment; prior to measurement, the boron-doped diamond electrode is held in a 0.1 M NaOH / 0.1 M NH ₄ NO ₃ aqueous solution at a potential of +1.5 V for 30 minutes on a reference electrode (SCE) basis. The pretreatment was performed.

Sample solution: A sample was taken from a Ni-B electroless bath containing 0.1 M NiSO ₄ and subjected to nickel plating. The sample was diluted 1000 times with pure water, and 0.1 M NaOH / 0.1 M NH. _{4 A} sample solution was appropriately added to the NO ₃ aqueous solution.

  Measurement: (1) In a sample solution, a boron-doped diamond electrode was held at −2.0 V for 60 seconds based on a reference electrode (SCE). Next, (2) in the sample solution, the electrode potential of the working electrode was set to +1.0 V on the basis of the reference electrode (SCE), and this potential was maintained for 60 seconds. Thereafter, (3) in the sample solution, the potential of the working electrode is scanned from the reference electrode (SCE) standard from +1.0 V to 0 V at a sweep rate of 50 mV / sec, a pulse voltage of 50 mV, and a pulse interval of 20 ms. A current curve was recorded and the peak current value was read.

  With respect to the sample solution, the obtained voltage-current curve is shown by a thick line in FIGS. 3 (a) and 3 (b). From the calibration curve shown in FIG. 4 (a), the Ni concentration of the sample solution in the case of using the rotating electrode as the boron-doped diamond electrode was determined to be 0.10 μM, and from the calibration curve shown in FIG. 4 (b), When the boron-doped diamond electrode was used as a stationary electrode and the solution was stirred, the Ni concentration of the sample solution was determined to be 0.098 μM. The result of measuring the Ni concentration of the sample solution by ICP (High Frequency Inductively Coupled Plasma Spectroscopy) was 0.099 μM.

Cleaning of the working electrode; after the measurement of each sample solution, the boron-doped diamond electrode was held in a 0.1 MH ₂ SO ₄ aqueous solution at +1.0 V on the basis of the reference electrode (SCE) for 60 seconds, and the cleaning treatment was performed. It was given.

(Example 4: Influence of impurities)
In order to investigate the influence of impurities in the sample, a sample solution to which an excessive amount of Pb was added was prepared, and the Ni concentration was measured. Each sample solution contains 5.18 μM Ni ²⁺ , but further contains Pb at a molar ratio with Ni ions (Pb ²⁺ : Ni ²⁺ ) of 1: 1, 4: 1, and 8: 1. A 0.1M NaOH / 0.1M NH ₄ NO ₃ aqueous solution was prepared as a sample, the Ni concentration was measured in the same procedure as shown in Example 3, and a voltage-current curve of a comparative control solution containing no Pb was obtained. Contrast.

  The obtained results are shown in FIG. As shown in FIG. 5, even if excessive impurities are included, the Ni concentration measurement characteristics do not change so much and the measurement method according to the present invention is not easily affected by impurities in the nickel bath. It has been shown.

(Example 5: Stability of electrode by cleaning treatment)
In order to investigate the stability of the electrode by the cleaning treatment, (1) a novel boron-doped diamond electrode, (2) after measurement of another sample solution, 0.1 M H ₂ SO ₄ aqueous solution was used as a reference electrode (SCE) standard. At +1.0 V for 60 seconds, subjected to a sulfuric acid cleaning treatment, and (1) after measurement of another sample solution, 0.1 M NaOH / 0.1 M NH after measurement of another sample solution. ₄ Prepare a boron-doped diamond electrode that was maintained at +1.0 V for 60 seconds in an aqueous NO ₃ solution and subjected to an alkali cleaning treatment, in the same procedure as shown in Example 3. The Ni concentration measurement of 0.1M NaOH / 0.1M NH ₄ NO ₃ aqueous solution containing Ni having a known concentration of 5.18 μM was performed by the DPV method, and the obtained voltage-current curves were compared with each electrode. .

  The result is shown in FIG. As shown in FIG. 6, the electrode subjected to the sulfuric acid cleaning treatment (2) (“Aft. 1D” in the figure) has almost the same characteristics as the new electrode (1) (“Original” in the figure). It was shown that repeated measurements can be performed with good reproducibility by subjecting the boron-doped diamond electrode to a sulfuric acid cleaning treatment. Note that the electrode subjected to the alkali cleaning treatment of (3) (“Clean in blank” in the figure) showed a measured value different from that of the new electrode at a high positive potential.

(A) is the electron micrograph (3000 times magnification) of the surface of an example of the boron dope diamond electrode produced by the microwave plasma CVD method in an Example, and its drawing, (b) is expansion of the same surface more It is the electron micrograph (magnification 7000 times) which was done, and its drawing. It is a schematic diagram which shows the structural example of the electrochemical measuring apparatus used in the management method of the electroless nickel plating bath which concerns on this invention. It is a chart which shows the voltage-current curve obtained as a result of having measured the sample solution containing Ni of various density | concentration in the Example by the DPV method using the boron dope diamond electrode which concerns on this invention, (a) is by a rotating electrode. The measured value (b) is the measured value by the stationary electrode. It is a chart which shows the calibration curve of Ni density | concentration and peak current value which were obtained in the Example, (a) is related with a rotating electrode, (b) is related with a stationary electrode. FIG. 2 is a chart showing voltage-current curves obtained as a result of measuring sample solutions obtained in Examples including various concentrations of Pb as impurities together with Ni by the DPV method using a boron-doped diamond electrode according to the present invention. is there. It is a chart which shows the voltage-current curve measured by the DPV method obtained in the example when investigating the influence of the washing process of a boron dope diamond electrode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrochemical measuring device 2 Working electrode 3 Reference electrode 4 Counter electrode 5 Sample solution 6 Potentiostat 7 Arithmetic device 8 Drive device 9 Rotation control device

Claims (5)

A sample solution obtained by diluting a sample collected from an electroless nickel plating bath to a predetermined concentration using a measuring device in which a working electrode comprising a boron-doped diamond electrode, a counter electrode and a reference electrode are connected to a potentiostat Immerse these electrodes in
First, (1) in the sample solution, the electrode potential of the working electrode is maintained for a predetermined time under the condition of the reduction side where Ni ions in the sample solution are deposited as Ni on the working electrode. (2) Next, in the sample solution The electrode potential of the working electrode is maintained for a predetermined time on the oxidation side condition in which the deposited Ni surface becomes nickel oxyhydroxide (NiOOH). (3) Further, the electrode potential of the working electrode is differentiated by differential pulse voltammetry in the sample solution. Based on the method, the electrode potential of the working electrode in the step (2) was scanned to the predetermined potential, and the voltage-current curve was recorded and the peak current value was read and prepared in advance. A method for managing an electroless nickel plating bath, wherein the concentration of nickel contained in the plating bath is determined in comparison with a calibration curve. Wherein the working electrode after the potential scanning to the predetermined potential, and held for a predetermined time to oxidative conditions side electrode potential in an aqueous sulfuric acid solution of specific concentration of the working electrode, to claim 1, characterized in that to clean the working electrode The management method of the electroless nickel plating bath of description. Wherein (1) prior to step, claim holds predetermined time oxidation conditions side sodium hydroxide / aqueous ammonium nitrate solution in a defined electrode potential concentration of the working electrode, and performing preprocessing of the working electrode 1 Or the management method of the electroless nickel plating bath of 2 . The boron-doped diamond electrode has a boron dose of 1 × 10 ¹⁹ ~ 2 × 10 ¹⁹  atoms / cm ^Three The method for managing an electroless nickel plating bath according to any one of claims 1 to 3, wherein: The method for managing an electroless nickel plating bath according to any one of claims 1 to 4, wherein the boron-doped diamond electrode is a rotating electrode.

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