Method for measuring leveler concentration in copper plating solution

Abstract

To provide a method for measuring leveler concentration even when the concentration is low.SOLUTION: A measurement method includes a calibration curve creation step of measuring Ar in a calibration solution with a known leveler concentration and creating a calibration curve showing the relationship between the leveler concentration and Ar; a first measurement step of measuring Ar in a standard solution containing a leveler and a first measurement solution containing a liquid to be measured and determining a leveler concentration ρ1 of the first measurement solution from the calibration curve; a second measurement step of measuring Ar in a second measurement solution containing the standard solution and determining a leveler concentration ρ2 of the second measurement solution from the calibration curve; and a calculation step of determining a leveler concentration of the liquid to be measured based on the leveler concentration ρ1 of the first measurement solution and the leveler concentration ρ2 of the second measurement solution.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for measuring the leveler concentration of a copper plating solution. More specifically, the present invention relates to a method for measuring the leveler concentration of a copper plating solution used in electrolytic plating during the production of copper-clad laminates.

Background Art

[0002] Flexible printed wiring boards with wiring patterns formed on the surface of resin films are used in electronic devices such as liquid crystal panels, notebook computers, digital cameras, and mobile phones. Flexible printed wiring boards are manufactured from copper-clad laminates in which copper foils are laminated on resin films.

[0003] A metallizing method is known as a method for manufacturing copper-clad laminates. The manufacturing of copper-clad laminates by the metallizing method is performed, for example, in the following procedure. First, an undercoat metal layer and a copper thin film layer are formed on the surface of a resin film by a vacuum deposition method. Next, a copper plating film is formed on the copper thin film layer by an electrolytic plating method. By electrolytic plating, the conductor layer is thickened until it reaches a film thickness suitable for forming a wiring pattern. By the metallizing method, a copper-clad laminate of a type called a so-called two-layer substrate, in which a conductor layer is directly formed on a resin film, can be obtained.

[0004] Additives such as levelers, brighteners, and polymers are generally added to the copper plating solution used in electrolytic plating. A leveler is a component that suppresses protrusions and makes the copper plating film flat. A brightener is a component that refines the deposited crystals and smoothens the surface of the copper plating film. A polymer is a component that relaxes the current concentration at the edge of the base material and makes the thickness of the copper plating film uniform.

[0005] For maintaining and managing the quality of copper-clad laminates, it is important to control the concentrations of these additives contained in the copper plating solution. As a method for measuring the concentration of additives contained in a copper plating solution, the CVS (Cyclic Voltammetric Stripping) method is known (Patent Document 1).

Prior Art Documents

Patent Document

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, when the leveler concentration of the copper plating solution is low, it may not be measurable by the CVS method. For example, depending on the CVS analyzer, the lower limit of the leveler concentration analysis is set at 2.0 mL / L, and analysis in the low concentration range below that is impossible.

[0008] In view of the above circumstances, an object of the present invention is to provide a method for measuring the leveler concentration of a copper plating solution that can measure the leveler concentration even when the concentration is low.

Means for Solving the Problems

[0009] The method for measuring the leveler concentration of a copper plating solution according to the first aspect is a method for measuring the leveler concentration of a copper plating solution by the CVS method, comprising a calibration curve creation step of measuring Ar of a calibration solution with a known leveler concentration and creating a calibration curve showing the relationship between the leveler concentration and Ar, a first measurement step of measuring Ar of a first measurement solution containing a standard solution containing a leveler and a measurement target solution and obtaining the leveler concentration of the first measurement solution from the calibration curve, a second measurement step of measuring Ar of a second measurement solution containing the standard solution and obtaining the leveler concentration of the second measurement solution from the calibration curve, and a calculation step of obtaining the leveler concentration of the measurement target solution based on the leveler concentration of the first measurement solution and the leveler concentration of the second measurement solution. The method for measuring the leveler concentration of a copper plating solution according to the second aspect is characterized in that, in the first aspect, it further comprises an iron concentration adjustment step of adjusting the iron(III) concentration of the first measurement solution and the second measurement solution to the same concentration control value. The method for measuring the leveler concentration of the copper plating solution according to the third aspect is characterized in that, in the second aspect, in the iron concentration adjustment step, the difference in the iron(III) concentration between the first measurement solution and the second measurement solution is set to 0.05 g / L or less. The method for measuring the leveler concentration of the copper plating solution according to the fourth aspect is characterized in that, in the first aspect, in the first measurement step and the second measurement step, the temperatures of the first measurement solution and the second measurement solution are adjusted to the same temperature control value. The method for measuring the leveler concentration of the copper plating solution according to the fifth aspect is characterized in that, in the fourth aspect, the temperature difference between the first measurement solution and the second measurement solution is set to 0.2 °C or less.

Advantages of the Invention

[0010] According to the first aspect, since a standard solution is added to the liquid to be measured and Ar is measured with the leveler concentration increased, the leveler concentration of the liquid to be measured can be measured even when the leveler concentration of the liquid to be measured is below the analysis lower limit value. According to the second aspect, by making the iron(III) concentrations of the first measurement solution and the second measurement solution coincide, the influence of the potential of iron is reduced, the leveler concentration can be accurately measured, and the variation in the measured values can be reduced. According to the third aspect, the variation in the measured leveler concentration can be suppressed to ±0.03 mL / L or less. According to the fourth aspect, by making the temperatures of the first measurement solution and the second measurement solution coincide, the influence of temperature is reduced, and the variation in the measured leveler concentration can be reduced. According to the fifth aspect, the variation in the measured leveler concentration can be suppressed to ±0.02 mL / L or less.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0012] Next, embodiments of the present invention will be described with reference to the drawings. (Copper-clad laminate) The measurement method according to an embodiment of the present invention is not particularly limited, but is applicable to, for example, measuring the leveler concentration of a copper plating solution used in electrolytic plating during the manufacture of a copper-clad laminate. Therefore, first, the copper-clad laminate will be described.

[0013] As shown in FIG. 1, the copper-clad laminate 1 includes a base material 10 and a copper plating film 20 formed on the surface of the base material 10. In the example shown in FIG. 1, the copper plating film 20 is formed only on one side of the base material 10. However, the copper plating film 20 may be formed on both sides of the base material 10.

[0014] The base material 10 is obtained by forming a metal thin film layer 12 on the surface of an insulating base film 11. As the base film 11, a resin film such as a polyimide film or a liquid crystal polymer (LCP) film can be used.

[0015] The metal thin film layer 12 is formed by a vacuum film formation method such as a sputtering method. The metal thin film layer 12 includes an underlayer metal layer 13 and a copper thin film layer 14. The underlayer metal layer 13 and the copper thin film layer 14 are laminated in this order on the surface of the base film 11. Generally, the underlayer metal layer 13 is made of nickel, chromium, or a nickel-chromium alloy. The copper plating film 20 is formed on the surface of the metal thin film layer 12 (copper thin film layer 14) by electrolytic plating.

[0016] Although not particularly limited, the thickness of the base film 11 is generally 10 to 100 μm. The thickness of the underlayer metal layer 13 is generally 5 to 50 nm, and the thickness of the copper thin film layer 14 is generally 50 to 400 nm. The thickness of the copper plating film 20 is generally 0.1 to 18 μm. Note that the metal thin film layer 12 and the copper plating film 20 together are referred to as a "conductor layer".

[0017] The copper plating film 20 can be formed, for example, by an electrolytic plating apparatus of the roll-to-roll method. This type of electrolytic plating apparatus is an apparatus that performs electrolytic plating on the long-strip-shaped base material 10 while transporting it by roll-to-roll. The electrolytic plating apparatus has a supply apparatus that pays out the base material 10 wound in a roll shape, and a winding apparatus that winds up the base material 10 (copper-clad laminate 1) after plating in a roll shape.

[0018] In the transport path of the base material 10, a pretreatment tank, a plating tank, and a post-treatment tank are arranged. While the base material 10 is being transported in the plating tank, a copper plating film 20 is formed on its surface by electrolytic plating. Thereby, a long-strip-shaped copper-clad laminate 1 is obtained.

[0019] The copper plating film 20 can also be formed by a single-sheet electrolytic plating apparatus. The single-sheet-shaped base material 10 is immersed in the copper plating solution in the plating tank to perform electrolytic plating, and a copper plating film 20 is formed on the surface of the base material 10.

[0020] In any method, a copper plating solution is stored in the plating tank. The copper plating solution contains a water-soluble copper salt. It is not particularly limited as long as it is a water-soluble copper salt generally used in the copper plating solution. For example, copper sulfate is used. The copper plating solution may contain sulfuric acid. By adjusting the addition amount of sulfuric acid, the pH and sulfate ion concentration of the copper plating solution can be adjusted. The copper plating solution generally contains additives added to the plating solution. Examples of the additives include a leveler, a brightener, a polymer, and a chlorine component.

[0021] The content of each component of the copper plating solution can be arbitrarily selected. However, it is preferable that the copper plating solution contains 15 to 70 g / L of copper and 20 to 250 g / L of sulfuric acid. By doing so, the copper plating film 20 can be formed at a sufficient speed. It is preferable that the copper plating solution contains 0.01 to 5.0 mL / L of a leveling agent. By doing so, protrusions can be suppressed and a flat copper plating film 20 can be formed. It is preferable that the copper plating solution contains 0.1 to 5.0 mL / L of a brightener. By doing so, the deposited crystals can be refined and the surface of the copper plating film 20 can be smoothed. It is preferable that the copper plating solution contains 0.5 to 10.0 mL / L of a polymer. By doing so, the current concentration at the end of the base material 10 can be alleviated and a copper plating film 20 with a uniform thickness can be formed. It is preferable that the copper plating solution contains 20 to 80 mg / L of a chlorine component. By doing so, abnormal deposition can be suppressed.

[0022] For maintaining and managing the quality of the copper-clad laminate 1, it is important to control the concentration of the additives contained in the copper plating solution. The concentration of the additives in the copper plating solution can be known from the amount of additives added immediately after the bath is built. However, since the additives are gradually consumed as electrolytic plating is carried out, the concentration of the additives during operation can only be grasped as an estimated value. Therefore, in actual operation, each additive is quantitatively replenished according to the integrated current amount in electrolytic plating. However, the additives may also be consumed by factors other than electrolysis. If only an amount of additives corresponding to the consumption estimated from the integrated current amount is replenished, the concentration of the additives in the copper plating solution often becomes lower than the target concentration. Therefore, every predetermined period (for example, every day), the copper plating solution is sampled from the plating bath to measure the concentration of the additives. Based on this measured value, the necessary amount of additives is replenished to correct the additive concentration to the target concentration.

[0023] (CVS method) The CVS method is known as a method for measuring the concentration of the additives contained in the copper plating solution. For measuring the additive concentration by the CVS method, the CVS analyzer AA illustrated in FIG. 2 is used.

[0024] The CVS analysis device AA has a measurement cell 30. A liquid to be measured is stored in the measurement cell 30. Three electrodes 31, 32, and 33 are immersed in the liquid in the measurement cell 30. The electrode 31 is a working electrode, the electrode 32 is a reference electrode, and the electrode 33 is a counter electrode. The three electrodes 31, 32, and 33 are attached to an electrode holder 34. The electrode holder 34 is connected to a potentiostat 35, and the potentiostat 35 is connected to a control device 36. The potentiostat 35 supplies a current to the electrodes 31 and 32 so that the potential between the electrodes 31 and 32 becomes a set value according to the instruction of the control device 36, and measures the current flowing between the electrodes 31 and 33.

[0025] A rotor 37 is disposed in the measurement cell 30. The rotor 37 is rotated by a stirrer 38 disposed below the measurement cell 30 to stir the liquid in the measurement cell 30.

[0026] In the CVS method, while rotating the working electrode 31 at a constant speed, the potential of the working electrode 31 is swept with reference to the reference electrode 32, and plating and stripping are repeated on the working electrode 31. The current flowing between the working electrode 31 and the counter electrode 33 at this time is measured to obtain a voltammogram. The area of the stripping peak is obtained from the voltammogram. The area of the stripping peak is referred to as Ar (Area Rotating). Since Ar depends on the additive concentration, the additive concentration can be obtained by measuring Ar.

[0027] (First Embodiment) The measurement method according to the first embodiment of the present invention is a method for measuring the leveler concentration of a copper plating solution by the CVS method. The measurement method of this embodiment has four steps: (1) a calibration curve creation step, (2) a first measurement step, (3) a second measurement step, and (4) a calculation step. Hereinafter, they will be described in order.

[0028] (1) Calibration Curve Creation Step In the calibration curve creation process, first, a calibration solution is prepared. The calibration solution is obtained by mixing a base solution, a brightener, and a polymer. The base solution is a copper plating solution that does not contain additives. For example, when the main component of the copper plating solution to be measured is copper sulfate, an aqueous copper sulfate solution is used as the base solution. The brightener and the polymer are added to the base solution in amounts that result in a saturated concentration in order to eliminate the influence on the Ar measurement value.

[0029] Next, a certain amount of a leveling agent is added to the calibration solution. As a result, a calibration solution with a known leveling agent concentration is obtained. The Ar of this calibration solution is measured by the CVS method. By repeating the addition of the leveling agent to the calibration solution and the measurement of Ar a predetermined number of times, the Ar of each of a plurality of calibration solutions with different leveling agent concentrations is obtained. From this result, a calibration curve showing the relationship between the leveling agent concentration and Ar is created. An example of the calibration curve is shown in Figure 3.

[0030] (2) First measurement process In the first measurement process, first, a first measurement solution is prepared. The first measurement solution is obtained by mixing a base solution, a brightener, a polymer, a standard solution, and a solution to be measured. The brightener and the polymer are added to the base solution in amounts that result in a saturated concentration. The standard solution is a copper plating solution containing a leveling agent at a predetermined concentration. The leveling agent concentration of the standard solution is set such that the leveling agent concentration of the first measurement solution exceeds the analysis lower limit value of the CVS analyzer AA. The solution to be measured is a copper plating solution for which the leveling agent concentration is to be measured. For example, the solution to be measured is a copper plating solution sampled from the plating bath of an electrolytic plating apparatus.

[0031] Next, the Ar of the first measurement solution is measured by the CVS method. Here, let the Ar measurement value of the first measurement solution be A1. As shown in Figure 3, the leveling agent concentration ρ1 corresponding to A1 is specified from the calibration curve, and ρ1 is taken as the leveling agent concentration of the first measurement solution.

[0032] The first measurement solution contains a standard solution including a leveling agent in addition to the liquid to be measured. That is, the standard solution is added to the liquid to be measured, and Ar is measured with the leveling agent concentration increased. Therefore, even when the leveling agent concentration of the liquid to be measured itself is below the analysis lower limit value of the CVS analyzer AA, the leveling agent concentration of the first measurement solution is above the analysis lower limit value, so that the leveling agent concentration of the first measurement solution can be accurately measured.

[0033] (3) Second measurement step In the second measurement step, first, a second measurement solution is prepared. The second measurement solution is obtained by mixing a base solution, a brightener, a polymer, and a standard solution. The amounts of the brightener and the polymer that reach the saturation concentration are added to the base solution. The standard solution has the same composition as that used in the first measurement step.

[0034] Next, Ar of the second measurement solution is measured by the CVS method. Here, let the Ar measurement value of the second measurement solution be A2. As shown in FIG. 3, the leveling agent concentration ρ2 corresponding to A2 is specified from the calibration curve, and ρ2 is taken as the leveling agent concentration of the second measurement solution.

[0035] (4) Calculation step In the calculation step, based on the leveling agent concentration ρ1 of the first measurement solution and the leveling agent concentration ρ2 of the second measurement solution, the leveling agent concentration ρ of the liquid to be measured is obtained. Basically, by subtracting the leveling agent concentration ρ2 of the second measurement solution from the leveling agent concentration ρ1 of the first measurement solution, the leveling agent concentration ρ of the liquid to be measured can be obtained. However, since it is a concentration calculation, "subtracting" as used here means calculating considering factors such as volume. That is, in the calculation of the leveling agent concentration ρ of the liquid to be measured, the volumes of the first measurement solution, the standard solution contained in the first measurement solution, the liquid to be measured contained in the first measurement solution, the second measurement solution, and the standard solution contained in the second measurement solution are each considered. Also, the first measurement solution and the second measurement solution are diluted by the amount containing the base solution, the brightener, and the polymer. The leveling agent concentration ρ of the liquid to be measured is calculated considering this dilution rate.

[0036] As described above, in the first measurement step, the leveler concentration is increased with a standard solution, and by subtracting the increase determined in the second measurement step, the leveler concentration ρ of the liquid to be measured is indirectly determined. By doing so, even when the leveler concentration of the liquid to be measured is below the analysis lower limit value, the leveler concentration of the liquid to be measured can be measured.

[0037] (Second Embodiment) Next, a measurement method according to the second embodiment of the present invention will be described. The measurement method of this embodiment is a method in which an iron concentration adjustment step is added to the first embodiment.

[0038] In the iron concentration adjustment step, the iron(III) concentrations of the first measurement solution and the second measurement solution are adjusted to the same concentration control value. Briefly speaking, a process of making the iron(III) concentrations of the first measurement solution and the second measurement solution coincide is performed. However, in operation, inevitably, there will be some difference in the iron(III) concentration between the first measurement solution and the second measurement solution, but such a difference is allowed.

[0039] The adjustment of the iron(III) concentration can be performed by adding iron(III) sulfate. The copper plating solution in the plating bath of the electrolytic plating apparatus is controlled so that the iron(III) concentration becomes a predetermined value (for example, 1.50 to 1.55 g / L). When this copper plating solution is used as the liquid to be measured, the iron(III) concentration of the standard solution used for preparing the first measurement solution and the second measurement solution may be adjusted according to the iron(III) concentration of the copper plating solution. By doing so, the iron(III) concentrations of the first measurement solution and the second measurement solution coincide.

[0040] If the iron(III) concentration differs between the first measurement solution and the second measurement solution, the measured value of the leveler concentration deviates from the true value, and the variation in the measured value becomes large. The reason for this is presumably that since the CVS method is a potentiometric analysis, the potential of iron affects the measurement by the CVS method. In addition, the influence of the potential of iron becomes large particularly when the leveler concentration is low.

[0041] By making the iron(III) concentrations of the first measurement solution and the second measurement solution coincide, the influence of the potential of iron is reduced. As a result, the leveler concentration can be accurately measured, and the variation in the measured values can be reduced. It is preferable that the difference in the iron(III) concentrations of the first measurement solution and the second measurement solution be 0.05 g / L or less. In this way, the variation in the measured leveler concentration can be suppressed to ±0.03 mL / L or less.

[0042] (Third Embodiment) Next, the measurement method according to the third embodiment of the present invention will be described. The measurement method of the present embodiment is a method of adjusting the temperatures of the first measurement solution and the second measurement solution in the first embodiment or the second embodiment.

[0043] That is, in the first measurement step and the second measurement step, the temperatures of the first measurement solution and the second measurement solution are adjusted to the same temperature control value. In short, a process of making the temperatures of the first measurement solution and the second measurement solution coincide is performed. However, operationally, inevitably, there is a slight difference in temperature between the first measurement solution and the second measurement solution, but such a difference is tolerated.

[0044] The temperature adjustment can be realized by various methods. For example, the temperatures of the first measurement solution and the second measurement solution after preparation are adjusted with a thermostat. Also, during the measurement by the CVS method, the temperatures of the first measurement solution and the second measurement solution in the measurement cell 30 of the CVS analyzer AA are adjusted with a heater or a chiller.

[0045] Particularly when the leveler concentration is low, the measurement value by the CVS method is affected by the temperature of the measurement solution. By making the temperatures of the first measurement solution and the second measurement solution coincide, the influence of the temperature can be reduced, and the variation in the measured leveler concentration can be reduced. It is preferable that the temperature difference between the first measurement solution and the second measurement solution be 0.2 °C or less. In this way, the variation in the measured leveler concentration can be suppressed to ±0.02 mL / L or less.

Example

[0046] (Iron(III) Concentration Test) A copper plating solution with a brightener concentration of 0.30 mL / L was prepared as the liquid to be measured. The copper plating solution contains iron. The brightener concentration of the liquid to be measured was measured by the same procedure as in the first embodiment. Note that the iron(III) concentrations of the first measurement liquid and the second measurement liquid were not adjusted. Table 1 shows the results obtained from performing the measurement three times. The difference in the iron(III) concentrations of the first measurement liquid and the second measurement liquid was 0.17 g / L. The measured value of the brightener concentration (average value of three measurements) was 0.34 mL / L, and the difference from the actual brightener concentration was 0.04 mL / L. Also, the standard deviation of the measured values of the brightener concentration was 0.05 mL / L.

[0047] Next, by the same procedure as in the second embodiment, the iron(III) concentrations of the first measurement liquid and the second measurement liquid were adjusted to the same concentration control value, and the brightener concentration of the liquid to be measured was measured. Table 1 shows the results obtained from performing the measurement three times. As a result of adjusting the iron(III) concentration, the difference in the iron(III) concentrations of the first measurement liquid and the second measurement liquid was 0.05 g / L. The measured value of the brightener concentration (average value of three measurements) was 0.29 mL / L, and the difference from the actual brightener concentration was 0.01 mL / L. Also, the standard deviation of the measured values of the brightener concentration was 0.03 mL / L.

[0048]

Table 1

[0049] From the above results, it was confirmed that by using the method of the present invention, the brightener concentration can be measured even at a low concentration of about 0.3 mL / L. Also, it was confirmed that when the iron(III) concentration is adjusted, the brightener concentration at a low concentration can be measured more accurately. Moreover, when the iron(III) concentration is adjusted, the variation in the measured values of the brightener concentration becomes smaller. Specifically, it was confirmed that when the difference in the iron(III) concentrations of the first measurement liquid and the second measurement liquid is 0.05 g / L or less, the variation in the measured values of the brightener concentration becomes ±0.03 mL / L or less.

[0050] (Temperature test) A calibration solution was prepared. Using a heater, the temperature of the calibration solution was adjusted to 24.0 ± 0.1 °C. The addition of a leveling agent to the calibration solution and the measurement of Ar by the CVS method were repeated multiple times to create a calibration curve showing the relationship between the leveling agent concentration and Ar.

[0051] A copper plating solution with a leveling agent concentration of 0.20 mL / L was prepared as the liquid to be measured. Using a heater, the temperature of the liquid to be measured was adjusted to 24.0 ± 0.1 °C. The Ar of the liquid to be measured was measured by the CVS method, and the leveling agent concentration was specified from the calibration curve. Here, the results obtained from performing the measurement three times are shown in Table 2. The measured value of the leveling agent concentration (average value of the three measurements) was 0.20 mL / L, which was consistent with the actual leveling agent concentration. Also, the standard deviation of the measured value of the leveling agent concentration was 0.02 mL / L.

[0052] Next, using a heater, the temperature of the liquid to be measured was adjusted to 24.5 ± 0.1 °C. The Ar of the liquid to be measured was measured by the CVS method, and the leveling agent concentration was specified from the calibration curve. The results obtained from performing the measurement three times are shown in Table 2. The measured value of the leveling agent concentration (average value of the three measurements) was 0.30 mL / L, and the difference from the actual leveling agent concentration was 0.10 mL / L. Also, the standard deviation of the measured value of the leveling agent concentration was 0.02 mL / L.

[0053]

Table 2

[0054] From the above results, it was confirmed that the measured value of the leveling agent concentration is affected by the temperature of the liquid to be measured. Therefore, it can be said that the smaller the temperature difference between the first measurement liquid and the second measurement liquid, the more accurately the leveling agent concentration can be measured and the smaller the variation in the measured values can be made.

Explanation of Symbols

[0055] AA CVS analyzer 30 Measurement cell 31 Working electrode 32 Reference electrode 33 Counter electrode 34 Electrode holder 35 Potentiostat 36 Control device 37 Rotor 38 Stirrer

Claims

1. A method for measuring the leveler concentration of a copper plating solution by the CVS method, comprising: a calibration curve creation step of measuring Ar of a calibration solution with a known leveler concentration and creating a calibration curve showing the relationship between the leveler concentration and Ar; a first measurement step of measuring Ar of a first measurement solution containing a standard solution containing a leveler and a solution to be measured, and obtaining the leveler concentration of the first measurement solution from the calibration curve; a second measurement step of measuring Ar of a second measurement solution containing the standard solution and obtaining the leveler concentration of the second measurement solution from the calibration curve; and a calculation step of obtaining the leveler concentration of the solution to be measured based on the leveler concentration of the first measurement solution and the leveler concentration of the second measurement solution. A method for measuring the leveler concentration of a copper plating solution, characterized by the above.

2. A method for measuring the leveler concentration of a copper plating solution according to claim 1, further comprising an iron concentration adjustment step of adjusting the iron(III) concentrations of the first measurement solution and the second measurement solution to the same concentration control value. A method for measuring the leveler concentration of a copper plating solution according to claim 1, characterized by the above.

3. In the iron concentration adjustment step, the difference in the iron(III) concentrations of the first measurement solution and the second measurement solution is set to 0.05 g / L or less. A method for measuring the leveler concentration of a copper plating solution according to claim 2, characterized by the above.

4. In the first measurement step and the second measurement step, the temperatures of the first measurement solution and the second measurement solution are adjusted to the same temperature control value. A method for measuring the leveler concentration of a copper plating solution according to claim 1, characterized by the above.

5. The temperature difference between the first measurement solution and the second measurement solution is set to 0.2 °C or less. A method for measuring the leveler concentration of a copper plating solution according to claim 4, characterized by the above.

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