JPS5953348B2 - Automatic management method and device for main components of chemical copper plating solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for automatically controlling the concentration and pH of chemical components in a chemical copper plating solution.

Conventionally, controlling the concentration of the main components of chemical copper plating solutions has been a process of trial and error.

That is, the total surface area of the body to be plated to be plated is estimated, and the consumption amount of the main component is calculated from the plating speed and the plating time based on the factor 1 created by the manufacturer 4.
A method of replenishing a predetermined amount was adopted. In order to achieve more accurate concentration control, the only option was to collect the plating solution from the gaps and chemically analyze it to adjust the concentration. Previously, chemical copper plating was used to make composite materials by coating insulating materials such as inorganic, organic, and organic materials with metal, by taking advantage of the electrical conductivity of chemical copper plating. This was a case where it was used as a pretreatment to impart conductivity to an insulating material. Therefore, there is no need to place importance on the mechanical properties of the copper plating film. The plating solution was managed using a simple but low-accuracy method such as the above-mentioned management method, and the resulting copper plating was sufficient. However, recently, the use of forming conductors on insulating materials such as epoxy resins, phenolic resins, or ceramics by chemical copper plating has become more common.

In such cases, it is necessary to have not only electrical properties as a conductor but also mechanical properties as a metal to a certain extent. However, since the properties of the plating film are significantly affected by the concentration of the main component of the plating, the above-mentioned trial-and-error management method cannot ensure reproducibility and reliability. Therefore, in order to eliminate the drawbacks of the above methods, it is desired to develop a technology for continuous automatic analysis and concentration control. When concentration management is automated, changes in concentration must be input as changes in potential and current.

For this purpose, instrumental analyzers are used, which are generally expensive and complex. In addition, if compounds or ions other than the target component coexist, the accuracy may be reduced due to damage prevention. For example, the colorimetric method or spectrophotometric method used to control the copper ion concentration in chemical copper plating solutions requires expensive equipment because it involves an electrical circuit that converts the amount of light absorption into the magnitude of electric current. There is a problem in that the error is large because it is strongly influenced by the pH of the plating solution, the presence of compounds other than copper ions, the concentration of ions, the hydrogen gas bubbles present in the plating solution, etc. In addition to copper ions, the components whose concentrations must be controlled in a chemical copper plating solution include hydrogen ion concentration, that is, PH, chelating agent or complexing agent concentration, and reducing agent concentration.

However, there are problems in that it is difficult, or in some cases impossible, to automatically measure and manage these concentrations, and this is a bottleneck in automatically managing the plating solution. PH is measured using a glass electrode with a fast response speed and a silver chloride electrode, a sulfur electrode, etc. as a reference electrode, and measurement data can be obtained as a potential change through an amplifier circuit.

Therefore, it is possible to perform automatic concentration control by driving the control device based on this amount of potential change. However, the glass electrode used in the measurement has the disadvantage of causing large alkali and salt errors at pH values below 1 and above 9, and also impairs the restorability of the glass electrode in alkaline solutions.
Since the chemical copper plating solution is a highly alkaline solution with a pH of 11 to 14, it cannot avoid the drawbacks of glass electrodes mentioned above and cannot withstand continuous use. Due to the above drawbacks, it is inevitable that extremely large errors will occur. Other electrodes that can measure PH include antimony electrodes and quinhydrone electrodes, but they are not used as PH measuring electrodes for automatic control because of their slow response speed and difficulty in handling. Also,
Since chelating agents and complexing agents are not consumed in the chemical copper plating reaction, their concentrations have not been controlled in the past. Even if the concentration is to be controlled, it is generally difficult to analyze the concentration other than by chemical analysis based on the principle of chelate back titration. Next is the reducing agent concentration.
This is difficult to manage.

In other words, formaldehyde is used as a reducing agent in chemical copper plating, and although it is relatively easy to chemically analyze formaldehyde, there is no way to measure its concentration in terms of potential or current. Such automatic control is impossible. Therefore, we have no choice but to adopt the following indirect method. The first method focuses on the hydrogen gas generated in proportion to the reaction amount of formaldehyde when formaldehyde is consumed by the chemical copper plating reaction, and detects the amount of this hydrogen gas. However, this method has the following drawbacks. Accurate measurements cannot be made because the generated hydrogen gas bubbles are not uniformly dispersed in the plating solution, and conversely, hydrogen gas cannot be quickly separated from the plating solution, making it impossible to perform accurate and fast-response measurements. That's what it means. In the second method, formaldehyde reacts with sodium sulfite to form an adduct, at which time hydroxide ions are generated in proportion to the amount of reaction, and the pH of the plating solution increases.
This method takes advantage of increasing the Using this property, the difference between the pH of the plating solution and the pH after the reaction with sodium sulfite can be determined as the amount of formaldehyde. However, since this method also requires PH measurement, it has the above-mentioned serious drawback and has no choice but to measure PH using a glass electrode with extremely large errors, and proper concentration control cannot be expected in the present invention. , A method for managing a chemical copper plating solution that solves the above-mentioned problems, for controlling the concentration of copper ions in the chemical copper plating solution, a chelating agent for copper ions, formaldehyde as a reducing agent, and the pH of the plating solution. The present invention aims to provide an apparatus for the same, which enables the automatic management of the chelating agent concentration, and also has a structure that is extremely inexpensive and easy to handle, while controlling the concentration of copper ions, formaldehyde, and the pH of the plating solution. The aim is to make it possible to automatically manage the information with good accuracy.

The present invention consists of: (a) separating a chemical copper plating solution having a pH of approximately 11 to 14 and containing copper ions, a chelating agent or complexing agent for copper ions, and a reducing agent for copper ions as essential components from a plating tank; , an acid solution was mixed with this fractionated solution to adjust the pH of the fractionated solution to 2 to 10, and water in the added acid solution. The pH of the chemical copper plating solution is adjusted using the signal generated by the difference between the elementary ion amount and the set hydrogen ion amount range; Alternatively, a solution containing a metal ion that forms a chelate or complex compound that is more stable than copper ions is added in a slightly excess amount of the metal ion to react with the total amount of the chelating agent or complexing agent in the pH-adjusted plating solution. The potential at this time and the potential of the PH adjustment solution before dissolving the metal ions are measured using an insoluble electrode and a saturated Amagi electrode, and the signal generated by the difference between the potential difference between the two and the set value range is determined. (c) Add sodium salt of sulfite to the same chemical copper plating solution as in (a) above, separated from the plating bath. is added slightly in excess of the amount that reacts with the total amount of reducing agent contained in the plating solution to create a state in which a few thousand sulfite ions are present, and then iodine is added, which is caused by the difference between the oxidation-reduction potential of iodine and the set value range. The chemical copper plating solution is managed by adjusting the reducing agent concentration of the chemical copper plating solution using a signal.

The present invention will be further explained below. The essential components of the chemical copper plating solution in the present invention are copper ions, a chelating agent or complexing agent for copper ions, and a reducing agent for copper ions.

Therefore, what should be automatically managed are the hydrogen ion concentration, that is, the pH of the plating solution, and the concentrations of copper ions, copper ion chelating agents or complexing agents, and reducing agents. First, a method for controlling the pH of the plating solution will be explained.

This is the method specified in (a) above of the present invention. Generally, glass electrodes are often used as electrodes for pH measurement. This is because the glass electrode satisfies the three elements required for an electrode for continuous PH detection: high sensitivity, fast response speed, and resilience. However, glass electrodes have the drawbacks mentioned above, such as PH
: P of highly alkaline chemical copper plating solution of about 11 to 14
H is difficult to directly and continuously detect and control. Therefore, in order to solve this problem, in the present invention, an acid solution is mixed with the separated highly alkaline plating solution, the pH of the mixed solution is adjusted to 2 to 10, and the pH is indirectly measured. However, simple neutralization methods are difficult to use here. This is because the chelating agent or complexing agent in the liquid reacts with the acid and consumes the acid solution, so if the concentration of the chelating agent etc. is not controlled, accurate pH cannot be obtained. In other words, the chelating agent is not consumed by the plating reaction, but it adheres to the plated object and is taken out of the plating tank, causing a decrease in concentration. Furthermore, as the plating reaction progresses, copper ions are released. The concentration of free chelating agent that is consumed and does not form chelates with copper ions increases. Chelating agents and complexing agents used in chemical copper plating, such as tartaric acid and its alkali metal salts, ethylenediaminetetraacetic acid and its alkali metal salts (hereinafter abbreviated as EDTA), ethylenediaminepentaacetic acid, etc.
It is a polybasic acid and reacts with hydrogen ions upon neutralization with the above acid solution. For example, EDTA as a chelating agent
When used, the reaction occurs as shown in the following equation. PH:8~12 L4-+H+=LH3-...
(1) PH: 4.5~8LH3-+H+=LHr...
... (2) PH: 0-4.5LHH! '+H+=LH
3- ・・・・・・(3) LH3-+H+
=LH4 (4), where L4- represents free EDTA.

That is, in a simple neutralization method, hydrogen ions in the acid solution react with free EDTA in the neutralized plating solution and are consumed, so if the free EDTA concentration is not controlled at a constant level, It cannot be controlled with the correct pH value: "In the present invention, this problem is solved by the copper ion concentration management method described below, that is, the method and configuration in which the copper ion and free EDTA concentrations are simultaneously managed. .

That is, in the present invention, EDTA and copper ions are accurately managed by the method described below.
PH can only be measured correctly if conditions such as accurate management are met. Therefore, under the conditions of the present invention,
The signal contrast H caused by the difference between the hydrogen ion amount in the added acid solution and the set hydrogen ion amount range can be accurately measured, and based on this, the correct Pm can be determined. In particular, this method utilizes the fact that the amount of change from the set pH of the plating solution is that the pH after neutralization with an acid solution appears as a large pH change. In other words, the amount of change in PH is extremely large near the neutralization equivalent point expressed by equation (2), so if a method using this is adopted, the sensitivity in PH detection will be increased, and the characteristics necessary for automatic control will be achieved. be satisfied. Therefore, a certain volume of plating solution is mixed with a certain concentration and a certain volume of acid solution,
It is configured so that the pH after neutralization is expressed by the equation (2) and becomes the 1-equivalent point. With this configuration, even if the PH value of the plating solution slightly changes from the target PH value, it will appear as a large PH change value in the neutralized acid, and will be reliably detected by the fast-responsive glass electrode. The automatic control device can be driven without oscillation. For example, E as a chelating agent
When using DTA, the equivalence point of formula (2) is PH: 7.3
PH detection sensitivity can be increased approximately 7 times, and the detected PH after neutralization is in the neutral range, allowing continuous measurement and detection without deterioration of the glass electrode. The properties necessary for automatic control can be provided without being interfered with by formic acid and sulfate ions that accumulate as the reaction progresses. When using EDTA, the above (2)
The pH of the formula is most preferably in the range of 4.5 to 8, but 2 to 8.
If it is between 10 and 10, almost satisfactory effects can be obtained.

Automatic control of plating solution PH management using the above-mentioned neutralization method is as follows. Using a microtube pump, the plating solution and the appropriate concentration of the plating solution are neutralized to pH:
Sample and mix with an acid solution whose concentration is set to 7.3. As mentioned above, even if the plating solution QpH drops slightly below the target value, the pH of the mixed solution is detected as a value of about 6 by the glass electrode, and the automatic control device is activated.
The highly alkaline solution is replenished into the plating solution until the pH of the mixed solution is detected as 7.3. All acid solutions such as hydrochloric acid, sulfuric acid, and perhydrochloric acid are effective. Next, copper ion (hereinafter abbreviated as CuII) and free chelating agent (or complexing agent)
We will discuss how to control the concentration.

This is the above (b) of the present invention. Here, a solution in which a metal ion that forms a chelate or complex compound that is equivalent to or more stable than CuII is dissolved.
A slightly excess amount of the chelating agent is added to react with the entire amount of the chelating agent in the pH-adjusted plating solution, and the metal ions are slightly dissolved. This will be explained as follows.
In a chemical copper plating solution, a chelating agent or a complexing agent having a concentration of about 1.5 to 5 times that of copper ions is used, and the copper ions are stabilized as a chelate compound.

When EDTA, ethylenediaminepentaacetic acid, etc. are used as a chelating agent, many metal ions including copper ions react with the chelating agent at a molar concentration ratio of 1:1. now,
If the concentration of copper ions in the chemical copper plating solution is set to C mol and the concentration of the chelating agent is set to n times NC mol, copper ions are completely chelated. Therefore, if a metal electrode, such as an insoluble electrode such as platinum or gold, is used, the potential between the monovalent copper ions (hereinafter abbreviated as CuI) contained in a trace amount of the plating solution as an impurity and the trace amount of free CuII can be reduced. As E(1)=0.
153-0.059210g {K (n-1) [CuI
〕｝ ・・・・・・(
5) is obtained.

However, K is the stability constant between CuII and the chelating agent,
[CuI] indicates the activity of CuI in the plating solution. Here, a metal ion solution that forms a chelate compound that is equivalent to or more stable than copper ions and has a certain concentration and a certain volume is mixed externally into a certain volume of plating solution having the above-mentioned concentration relationship. The mixing of metal ions from the outside causes
Concentration difference between Chido CuII and chelating agent (n-1)C
At slightly more than molar metal ion concentrations, chelated CUII dissociates from the chelating agent to form free CuII. Therefore, the potential at the insoluble electrode obtained at this time is E(2)=0.153+0.0
59210g {[CUII)/[CuI]}...
- (6).

However, [CuII) indicates the activity of free CuII.
In other words, when a certain volume of a metal ion solution that forms a chelate compound that is equivalent to or more stable than copper ions is externally mixed into a certain volume of plating solution, the concentration of the metal ion solution must be the appropriate concentration. It is configured to obtain the potential of E(2) in equation (6) when the liquid is soaked. When CuII is consumed by the plating reaction, the concentration of free chelating agent increases, and all external metal ions are chelated, resulting in a potential of E(1). Become. By detecting the potential changes of E(2) and E(1), information on the concentration of CuII and the concentration of free chelating agent can be obtained. That is, add a solution containing dissolved metal ions to a state in which the metal ions are slightly dissolved, measure the potential at this time and the potential of the PH adjustment solution before dissolving the metal ions, and calculate the difference between the potential difference between the two and the set value range. The chelating agent concentration and copper ion concentration of the chemical copper plating solution can be determined from the signals generated, and each concentration can be adjusted based on this information.

Since this method is only concerned with the reactivity between the metal ion CuII and the chelating agent, there is no effect of the PH of the hot plating solution, impurities, hydrogen gas, etc. contained in the plating solution, which are the drawbacks of the conventional method. is clear.

Furthermore, since the concentration change required for automatic control is obtained directly as a potential change, no conversion device into potential and current is required, and it is therefore obvious that the configuration is inexpensive. Therefore, with the configuration described below, a rational automatic management method can be achieved. First, by the above-mentioned neutralization method, P
A metal ion solution of a predetermined concentration sampled by a microtube pump at a constant flow rate is further mixed with the H-detected mixed liquid.

In this case, metal ions include metals with a chelate stability constant equal to or higher than that of copper ions, such as divalent copper ions, trivalent iron ions, trivalent thallium ions, divalent mercury ions, and trivalent indium ions. Ion is suitable. Desirably, it should be inexpensive and easy to handle;
Divalent copper ions and trivalent iron ions are preferable because they can detect potential changes with high sensitivity. Next, trivalent iron ions, divalent mercury ions (hereinafter referred to as FeIII, HgII), etc., which have stronger stability between CuII and the chelating agent, are added to the solution at a slightly excess concentration of the total chelating agent concentration, that is, NC moles. Mix from outside so that Therefore, all of the sampled CuII in the plating solution and excessive concentrations of FeIII and HgII are generated as free metal ions. Therefore, the electrode potential obtained with an insoluble electrode is F
For eIII E(3)=0.77+0.0610g{
[FeIII)/[FeII)] (7).

Here, [FeIII) and [FeIO indicate the activity of trivalent iron ions and divalent iron ions contained in trace amounts as impurities. Therefore, the concentration of the total chelating agent can be detected by the change in electrode potential E(2) to E(3). That is, when a metal ion solution that forms a chelate compound more strongly than a certain volume of CUII is mixed externally into a certain volume of plating liquid at a certain concentration and a certain volume, when the metal ion solution has an appropriate concentration, The potentials E(1) and E(2) described above are obtained. On the other hand, if the total chelating agent concentration decreases for some reason, free mixed metal ions are generated, resulting in potential E(3). With this information, the chelating agent concentration can be controlled. Next, a method for detecting the concentration of formaldehyde, which is a reducing agent in a chemical copper plating solution, will be described.

This is the part corresponding to the above (c) of the present invention. Formaldehyde is a simple organic compound, but its reaction rate is generally slow. The slow reaction rate means that it takes a long time from sampling the plating solution to detecting the concentration, which can lead to errors in concentration control. Therefore, in the present invention, a sodium salt of sulfite that rapidly reacts with formaldehyde,
In other words, addition reactions such as acidic sodium sulfite and sodium sulfite are used. That is, a slightly excess sodium sulfite solution was added to a certain volume of the plating solution collected in the same manner as in the above pH measurement so as to react with the entire amount of reducing agent contained in the plating solution, so that a slight amount of sulfite ions were present. put it in a state where it does. In other words, a sodium sulfite solution with a concentration slightly in excess of the formaldehyde concentration to be controlled is added. This mixing causes all the formaldehyde to rapidly react with the sodium sulfite (acid or normal salt), leaving a certain excess concentration of sodium sulfite if the formaldehyde concentration is correct. This residual sodium sulfite is mixed and reacted with an iodine solution of a fixed concentration and volume.
When forroomaldehyde is consumed by the plating reaction, the concentration of remaining sodium sulfite becomes higher than the set value, and all of the mixed iodine is reduced by sulfite ions and becomes iodine ions. Therefore, the electrode potential obtained with the insoluble electrode is expressed by the above formula (5) and E(1). , if the formaldehyde concentration is higher than the concentration to be controlled, the residual sodium sulfite concentration will be a low value, and the mixed iodine will remain unreacted iodine. Therefore, the electrode potential obtained with an insoluble electrode is
As the oxidation potential between iodine and iodine ion, ・−
,゛E(4):0.54+0.0310g{[Ih]/
Obtain [1-]2}.

Here, [Ii] and [1-] represent iodine complexed with an iodine ion and the activity of the iodine ion. In this way, with the information changing from potential E(1) to E(4),
The concentration of formaldehyde can be detected indirectly. Next, the principle and apparatus will be specifically explained using examples.

〔Example〕

[1] Chemical copper plating solution CuSO4.5H20...13gEDTM-2
Na...40g HCH0...3g Additives...Small amount of water...Weighing solution with the total as 11: PH: 12.2 [11] Acid solution 0.115N hydrochloric acid [111. ) First titration solution FeCl3...9.01g HC1...5m1 Water...Amount to make the total 11 [I]
Second titration solution FeCl3...8.43g HC1...5m1 Water...Amount to make the total 11 [v]
Sulfite solution Na2SO3...18.909g
KH2P04...10g K2HP04...10g Water...Amount to make the total 11 [VI
) Iodine solution KI...40g 12...12.69g KH2P04...40g K2HP04...40g Water...Amount to make the total 11 By using the above chemical copper plating solution composition and plating solution PH with the above titration solution, the concentration can be automatically controlled for 100 continuous hours using the main component concentration automatic control device with the configuration shown in the figure. Ta.

The control accuracy in this case was high within ±5% for each component. The figures will be explained below. First, the plating liquid is sampled from the plating tank 1 at a flow rate of 50 ml per hour or less using the multiple tube pump 2.

After mixing the acidic solution from the acid solution tank 9 through the multiple tube pump 2, the pH after neutralization is measured with a PH detection cell. When the pH after neutralization is less than 7.3, the PH control device 16 operates the solenoid valve 23 (a pump may also be used, the same applies hereinafter).
is opened, and high concentration alkaline solution is supplied to the plating tank 1 from the alkaline solution supply tank 19. When the pH detection cell 4 detects a pH of 7.3 or higher after neutralization, the electromagnetic valve 23 closes and the supply of the highly concentrated alkaline solution to the plating tank 1 is stopped. The sampling liquid leaving the PH detection cell 4 is mixed with the FeIII solution from the first titration solution tank 10 through the multiple tube pump 2, and enters the copper detection cell 5, where a potential difference is created between the platinum electrode and the saturated sweetener electrode. is detected and the potential difference is smaller than 0.12, the copper ion control device 15
The electromagnetic valve 24 is opened, and the plating tank 1 is supplied with a high concentration copper sulfate solution from the copper ion supply tank 20. Copper detection cell 5
When a high potential of 0.12 V or more is detected, the electromagnetic valve 24 is closed and the supply of copper ions is stopped. The sampling liquid leaving the copper detection cell 5 is mixed with FeIII solution from the second titration solution tank 11 through the multiple tube pump 2, and enters the key agent detection cell 6, where a potential difference is created between the platinum electrode and the saturated sweetener electrode. is detected and is greater than 0.33 V, the electromagnetic valve 25 of the chelating agent control device 4 opens to supply a highly concentrated alkali metal salt 2Na solution to the plating tank 1 from the chelating agent replenishing tank 21. The sampling liquid that has exited the chelating agent detection cell 6 is discarded into a waste liquid tank 12. on the other hand,
The plating liquid sampled from the plating tank 1 through the multiple tube pump 2 is mixed with sulfurous acid and iodine solutions from the sulfite solution tank 8 and the iodine solution tank 7 through the multiple tube pump 2, and enters the formaldehyde detection cell 3.
A potential difference is detected between the platinum electrode and the saturated sweet water electrode, and 0
．． When the voltage is lower than 1V, the formaldehyde replenishment tank 17 opens the electromagnetic valve 22 to replenish the plating tank 1 with a concentrated formaldehyde solution from the formaldehyde replenishment tank 18.

The sampling liquid that has exited the formaldehyde detection cell is then discarded into a waste liquid tank 13. As mentioned above, this device has a simple configuration, and the feature of this device is that it can detect the concentration of each component by potentiometric titration. The key is to maintain constant output, sampling rate using multiple tube pumps, and titration rate. The present principles and apparatus can also be applied to the concentration control of the main components of gold, silver, and nickel chemical plating solutions, which require metal ions, chelating agents, reducing agents, and solution pH control. In addition,
Regarding this apparatus, in order to perform the reaction smoothly and stably, independent sampling and multiple tube pumps may be used for each component. Furthermore, a constant temperature device may be attached to keep the temperature of the detection cell constant. As described above, the method of controlling the concentration of the main component of a chemical copper plating solution of the present invention is cheaper and more accurate than the conventional technology, and is a control method that does not affect the composition of other components than the main component. I was able to provide it.

[Brief explanation of drawings]

The figure shows a configuration diagram of an automatic management device for the main components of a chemical copper plating solution. 1... Plating tank, 2... Multiple tube pump, 3...
... formaldehyde detection cell, 4... PH detection cell, 5... copper detection cell, 6... chelating agent detection cell,
7... Iodine solution tank, 8... Sulfurous acid solution tank, 9...
・Acid solution tank, 10, 11...Titration solution tank, 12, 13
... waste liquid tank, 14 ... chelating agent control device, 15.
...Copper ion control device, 16...PH control device, 17
... Formaldehyde control device, 18... Formaldehyde supply tank, 19... Alkaline solution supply tank, 20
...Copper ion supply tank, 21...Chelating agent supply tank,
22-25... Solenoid valve.

Claims (1)

[Scope of Claims] 1 (a) A chemical copper plating solution having a pH of about 11 to 14 and containing copper ions, a chelating agent or complexing agent for copper ions, and a reducing agent for copper ions as essential components is prepared from a plating tank. A signal is generated by the difference between the amount of hydrogen ions in the added acid solution and the set hydrogen ion amount range. (b) A metal ion that forms a chelate or a complex compound that is equivalent to or more stable than copper ions is dissolved in the chemical plating solution taken from the plating bath. The solution is added in a slightly excess amount to react with the entire amount of the chelating agent or complexing agent in the pH-adjusted plating solution, so that the metal ions are slightly dissolved. The potential of the adjustment solution is measured using an insoluble electrode and a saturated aqueous electrode, and the signal generated by the difference between the potential difference between the two and the set position width is used to determine the chelating agent or complexing agent concentration and copper ion concentration in the chemical copper plating solution. (c) Add sodium sulfite to the same chemical copper plating solution as in (a) above taken from the plating tank in an amount slightly in excess of the amount required to react with the total amount of reducing agent contained in the plating solution. In addition, sulfite ions are slightly present, and then iodine is added, and the reducing agent concentration in the chemical copper plating solution is adjusted by the signal generated by the difference between the iodine oxidation ring potential and the set value range. How to manage chemical copper plating solution. 2. A plating tank that stores a chemical copper plating solution containing as essential components copper ions, a chelating agent or complexing agent for copper ions, and formaldehyde, which is a reducing agent for copper ions, and a solution tank that stores an acid solution for pH adjustment. , a solution tank for storing a titration solution in which metal ions are dissolved, a solution tank for storing a solution of sodium sulfite salt for formaldehyde adjustment, and an iodine solution for measuring residual sulfite, and a multiplex system for pumping up the solutions in these solution tanks. Mixing the plating solution and the titration solution with a detection cell consisting of a tube pump, an insoluble electrode and a saturated reference electrode for detecting the concentration and pH in each solution pumped by the multiple tube pump. and a transportation route for transporting the same, and a supply tank for formaldehyde, pH adjustment alkaline solution, copper ion, chelating agent, or complexing agent for replenishing the plating tank according to the detected value of the detection cell. and a control device that controls the opening and closing of these supply tanks.