JPS6030759B2 - Method for controlling metal ion concentration in electrolytic bath - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bath concentration control method for automatically controlling the concentration of an electrolyte in an apparatus for continuous electrolytic deposition of metals to a predetermined value.

Electrolytic deposition is a method that uses electrical energy to deposit metal ions in an aqueous metal salt solution onto the surface of another substrate.
The electrolytic solution refers to a solution that carries out the electrolytic deposition reaction.

In such an electrolytic solution, electrolytic performance such as electrolytic deposit metal composition and deposition efficiency depends on the composition of the electrolytic solution, and is required from proper electrolytic solution composition management.

The electrolyte composition is determined by the amount of electrolyte deposited, the amount of electrolyte that adheres to the surface of the exposed object and is carried out to the next process (hereinafter referred to as drag-out amount), and the amount of electrolyte that adheres to the surface of the electrodeposited material and is carried over from the previous process. It varies depending on the amount of extraneous ions contained in the electrolyte, the amount eluted from the metal body to be deposited into the electrolytic solution (hereinafter referred to as eluted amount), etc.
However, if electrolytic deposition is also performed using an insoluble anode,
The amount of metal consumed by military analysis can be replenished by dissolving the metal in the electrolyte by another method, or by using a substance such as carbonate that allows the chemical species bound to the metal to easily leave the system. There must be.

On the other hand, metals consumed by drag-out need to be replenished with substances that make up the electrolyte, such as sulfate. Furthermore, when metals are generally electrolytically deposited, they are affected by extraneous ions (for example, Fe, which is commonly used as an electrodeposited object), and when electrolyzing the target metal with high current efficiency, it is necessary to It is necessary to maintain the ratio between the target metal ion concentration and the hybrid ion concentration above a certain value by decreasing the concentration by a method or by increasing the target electrolyzed metal ion concentration.

The present inventors focused on the fact that the target metal ion concentration and the detrital ion concentration could be used to directly measure the coloring caused by the target element using a three-wavelength colorimeter, and further calculated them using an arithmetic circuit in conjunction with the pH measurement value. We have developed a system that calculates the target metal ion concentration, determines the amount of mist prayer metal consumed and the amount consumed by drag-out, and replenishes the corresponding metal compound into the electrolytic bath.
Furthermore, how to determine the target metal ion concentration and the impurity ion concentration using a three-wavelength colorimeter will be explained. When measuring complementary metal ions using the absorbance method, the wavelengths of the respective metal ions overlap and interfere with each other, making it impossible to obtain appropriate absorbance.

For example, as shown in Figure 2, when the optimal wavelength of the target metal ion is lo and the absorption wavelength of the interfering metal ion is 1, 12, the lo value will be influenced by 1, 12 and will not reflect the true absorbance. Not shown. The influence of 1, 12 on lo differs depending on the combination of substances to be measured, and the degree of influence also differs depending on the concentration of each substance to be measured.

However, it is necessary to determine the measurement method by experimentally considering the degree of influence depending on the combination of the element to be measured and its concentration. Therefore, in this measurement, the target metal ion was one element and the interfering metal ions were two elements, and a three-wavelength colorimeter was used, which was equipped with a filter that passed each metal ion. The measurement method is based on the relationship between the target wavelength lo and the interference wavelengths 1 and 12.
Determine the true absorbance using the formula: true absorbance = [L±(1,112)]±(1,10Z), and determine the target metal ion amount from the relational expression of the absorbance with the amount of metal ions whose concentration is known in advance. be able to. By automatically controlling the composition of the electrolytic deposit in this way, it is possible to easily control the amount of metal metallization by adjusting the amount of current applied, and the quality of the surface metallization can be maintained at an extremely high level. It is. Hereinafter, an embodiment of the present invention will be described in accordance with the drawings, in which Ni is subjected to lightning deposition in the presence of dusty ions Fe20 and Fe30.

In FIG. 1, an electrolytic solution 1 is circulated between an electrolytic cell 2 and a circulation tank 3 via pumps 4 and 4', and is controlled at a constant temperature by a temperature controller 5. The electrolytic solution 1 is sampled from the circulation tank 3 via the sampling pump 6, and the pretreatment device 7 processes the impediments such as dust and suspended matter contained in the sample to obtain a clean sample. The pretreated electrolyte is supplied to a continuous three-wavelength colorimeter 8. The continuous three-wavelength color meter 8 is an analyzer that measures the concentration of nickel, which is the target metal ion, and three metal ions, Fe20 ion concentration and Fe30 ion concentration, which interfere with the measurement of the nickel concentration. When measuring nickel ions using the spectrophotometric method, if the most sensitive maximum absorption wavelength is selected, the Fe20 ion wavelength and the Fe30 ion wavelength inevitably overlap with the nickel ion wavelength, resulting in interfering elements in the measurement of nickel ions. becomes. Moreover, as shown in FIG. 3 as a result of the experiment, the Fe20 ions have a positive error with respect to the Ni20 ions, and the Fe30 ions have a negative error and interfere with the Ni20 ions.

Therefore, in order to remove this interference and accurately analyze the amount of nickel ions, the light from the light source 21 as shown in FIG. Ni20 filter (A), Fe20 filter (B), and Fe30 filter (
C) allows separation into wavelengths suitable for each ion, and guides the light having the wavelength that has passed through the rotary filter 23 to the continuous flow cell 24, where the absorbed light is sent to the detector 2.
5 and sent to the calculation unit 9 in FIG. 1 as respective metal ion amount concentration signals. If the target metal ion concentration is lower than the set value, the controller 11 sends Ni20 ions from the Ni20 ion replenishment tank B via the pump 12. NiS04・
Supply as mother LO. The electrolytic solution 1 treated with the pretreatment device 7 is supplied to a continuous pH meter 14, the pH value is measured, and the p
The H concentration signal is calculated by the calculation section 9 and displayed on the display section 1. If the pH value is lower than the predetermined pH value, the H concentration signal is calculated by the calculation section 9, and if the pH value is lower than the predetermined value, the H concentration signal is sent from the pH supply tank 13' via the pump 12' according to the signal from the control section 11.
Replenish iC03. In FIG. 1, 15 is a steel plate, 16 is an electrode, and 17 is an energizing roll. In addition, all the Fe ions accumulated in the electrolytic solution 1 as foreign ions also electrolytically deposit Fe ions at the same time during nickel electrolytic analysis, reducing the nickel electrolytic deposition efficiency. This relationship is shown in FIG. Therefore, the ratio of nickel ion concentration to total iron ion concentration must be kept within a certain range (N
It is necessary to control the ratio of i/Fe to 2 or more.

As detailed above, according to the present invention, the amount of haze deposited, the amount of drag-out, and the amount of contaminant ions, which are factors that cause fluctuations in the concentration of the electrolyte, can be quickly measured and automatically controlled, thereby further improving the concentration management of the electrolyte. This is possible in a stable manner.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the present invention, and FIG. 2 shows the relationship between the target wavelength and interference wavelength when measured by the absorbance method. Figure 3 shows that the interference effect differs depending on the type of interfering ion, Figure 4 is a block diagram of a continuous three-wavelength colorimeter, and Figure 5 shows the rotation of Figure 4. 3 is a detailed diagram of the expression filter 23. FIG. FIG. 6 shows the relationship between the current efficiency of Ni and Ni/Fe. 1... Electrolyte, 2... Electrolytic tank, 3... Circulation tank, 4, 4', 6
, 12, 12'...Pump, 5...Temperature controller, 7...Pretreatment device, 8...3 wavelength colorimeter, 9
...Arithmetic section, 10-display section, 11-control section, 12...N
i Replenishment tank, 13... pH replenishment tank, 14...
pH meter, 15... Steel plate, 16... Electrode, 17...
Energizing roll, 21... light source, 22-slit, 23-
...Rotary filter, 24...Flow cell, 25...Detector. Figure 4 Figure 5 Burial figure

Claims (1)

[Claims] 1 In the metal electrolytic deposition equipment, a part of the treatment bath in the metal electrolytic deposition tank is guided to a continuous three-wavelength colorimeter through a pretreatment device of the colorimeter, and is passed through a filter A for the target wavelength and a filter B for interfering elements. The signals from C and C and the signal from the continuous pH meter are input into an arithmetic circuit, and the ratio of the target metal concentration to the interfering element concentration is calculated to obtain the target metal concentration setting value, and the amount of electrolytically deposited metal and dragout metal is calculated. A method for controlling the concentration of metal ions in an electrolytic bath, which comprises calculating and controlling the amount of the metal compound to be replenished in accordance with the consumption of each metal.