JP2004162078A - Copper plating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a copper plating device which can perform electrolytic copper plating with good results by accurately controlling the copper ion concentration in a plating solution. <P>SOLUTION: The plating device is equipped with an insoluble anode, a cathode being an object to be plated, and a plating bath filled with an electrolytic solution containing, e.g., copper sulfate and free sulfuric acid. The device is constructed so that, in copper plating with the device, the copper concentration in the plating bath is detected with a colorimeter with a wavelength of measuring light set at 500 nm or higher, preferably 540 nm, and based on the detected concentration, a makeup material, e.g., copper oxide, is supplied. The copper concentration is detected without being affected by impurities, e.g., titanium and iron. By supplying copper on the basis of the detected concentration, the supply timing can be easily set. Thus, the copper ion concentration in the electrolytic solution can be accurately controlled, enabling copper plating with good results. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a copper plating apparatus for plating a material to be plated with copper.
[0002]
[Prior art]
As one of the methods of performing copper plating on a substrate to be plated, for example, a printed circuit board, an electrolytic plating method in which a copper plating material is supplied in sulfuric acid which is an electrolytic solution, and current is passed between an insoluble anode and a substrate to be a cathode. It has been known.
[0003]
In the electrolytic plating method, it is known that a plating apparatus shown in FIG. 8 is used (for example, Patent Document 1).
In the figure, reference numeral 10 denotes a plating bath, which is filled with an electrolytic solution obtained by dissolving a copper plating material made of, for example, copper oxide in sulfuric acid, and has an anode 12 connected to the positive electrode side of the DC power supply 11 and a DC power supply 11. A material to be plated which is the cathode 13 connected to the negative electrode side, for example, a metal plate to be plated is immersed. When a current is applied to each of the electrodes 12 and 13, oxygen is generated at the anode 12 by the electrode reaction shown in the reaction formula 1 while the electrode reaction shown in the reaction formula 2 is formed on the surface of the plate 13 which is the cathode 13. As a result, copper is deposited and copper plating is performed. The electrolytic solution having reduced copper ions is supplied via a pump P1 to a dissolving tank 14 provided with a stirring means 14a, where a predetermined amount of, for example, copper oxide powder is supplied from a hopper to supply copper. . At this time, the conducting current and the reaction efficiency occurring on the cathode surface, that is, the amount of copper ions in the electrolytic solution deposited on the cathode, have a good correspondence, and therefore, the copper ion concentration of the electrolytic solution is calculated from the integrated value of the supplied current. By grasping, copper oxide was supplied in an amount corresponding to that. Then, the electrolytic solution supplied with copper is returned to the plating bath 10 via the pump P2. Reference numeral 15 denotes a filter for removing insoluble residues in the electrolytic solution.
H ₂ O → (１ ／) O ₂ + 2H ⁺ + 2e (1)
Cu ²⁺ + 2e → Cu (2)
[0004]
[Patent Document 1]
JP-A-2002-68743 (page 4, FIG. 2)
[0005]
Recently, as shown in FIG. 9, a multilayer printed board 16 formed by pressing a plurality of printed boards 16a and 16b as a body to be plated has been used. In this case, first, copper plating is performed on each of the substrates 16a and 16b having an electroless copper plating film formed on the surface in advance, and for example, through holes 17a and 17b, which are circular through holes, are filled with plated copper. Then, the substrate 16b is pressed to obtain a multilayer printed circuit board. In this case, in order to densely fill the through holes 17a (17b) with plated copper, it is better to use an electrolytic solution having a copper concentration as high as possible. That is, if an electrolytic solution having a concentration of copper sulfate of, for example, 90 to 100 g / liter is used as in the related art, the copper concentration is too low, and the through holes 17a (17b) are not densely filled to form voids. As a result, a printed board having a large contact resistance between the boards 16a and 16b is obtained. For this reason, it has been studied to make the concentration of copper sulfate 180 to 190 g / liter, for example, and the free sulfuric acid concentration to 90 to 100 g / liter.
[0006]
[Problems to be solved by the invention]
However, when plating is performed using the above-mentioned high-concentration electrolytic solution, there is a problem that it is difficult to control the concentration of copper sulfate. In other words, if the concentration of copper sulfate is too high, copper sulfate precipitates in the electrolytic solution, and the deposited copper sulfate adheres to the surface of the plating material serving as the cathode, and the portion is dissolved when washed with water to cause defects. In some cases, the concentration of free sulfuric acid in the electrolytic solution decreases, and the current during plating becomes difficult to flow. Conversely, when the concentration of copper sulfate is low, dense copper plating cannot be performed as described above, and further, the concentration of free sulfuric acid increases and copper oxide becomes difficult to dissolve. For this reason, when a high-concentration electrolytic solution is used, severe concentration control is required. However, if the copper sulfate concentration is determined from the integrated current value as described above, for example, the upper part is open. There is a concern that a difference may occur between the actual copper sulfate concentration due to disturbance such as a change in the concentration of copper sulfate in the electrolytic solution due to evaporation of water from the plating bath 10 having the structure.
[0007]
The plating apparatus of the present invention has been made under such circumstances, and its purpose is to control the copper ion concentration of the electrolytic solution with high precision when performing electrolytic copper plating using an insoluble anode. It is an object of the present invention to provide a copper plating apparatus capable of performing good plating. It is another object of the present invention to provide a copper plating apparatus capable of controlling a copper ion concentration with high accuracy over a wide range of copper ion concentrations.
[0008]
The plating apparatus of the present invention is a plating apparatus comprising: an insoluble anode, an object to be plated serving as a cathode, and a plating bath filled with an electrolytic solution containing copper as a plating material.
A colorimeter having a wavelength of measurement light of 500 nm or more for detecting the concentration of copper in the plating bath,
A dissolving tank for dissolving copper in the electrolytic solution,
Circulating means for circulating the electrolyte between the plating bath and the dissolving tank,
Supply means for supplying copper to the melting tank, based on the detected value of the copper concentration detected by the colorimeter, so that the copper concentration in the plating bath becomes a preset value. It is characterized by having.
[0009]
According to the copper plating apparatus of the present invention, by detecting the concentration of copper contained in the electrolytic solution of the plating bath using a colorimeter with a measurement wavelength set to a predetermined value, for example, titanium, impurities such as iron By avoiding the influence, the copper concentration is detected with high accuracy, and the supply of copper is performed based on the detected value, whereby the timing of the supply can be easily set. Therefore, the concentration of copper ions in the electrolytic solution can be controlled with high accuracy, and as a result, favorable copper plating can be performed.
[0010]
The electrolytic solution in the plating bath contains, for example, copper sulfate and free sulfuric acid, and the concentration of the copper sulfate may be controlled to 160 g / liter to 195 g / liter, and the concentration of free sulfuric acid is 90 g. / Liter to 130 g / liter.
[0011]
The copper supplied to the melting tank may be, for example, copper oxide. The copper oxide may be heated, for example, by heating basic copper carbonate to 250 ° C. to 800 ° C. in an atmosphere that does not become a reducing atmosphere. It may be a readily soluble one obtained by decomposing and then washing with water.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment according to the plating apparatus of the present invention will be described with reference to FIG. In the drawing, reference numeral 20 denotes a plating bath filled with an electrolytic solution containing, for example, copper sulfate (CuSO ₄ .5H ₂ O) and free sulfuric acid (H ₂ SO ₄ ). The plating bath 20 has an insoluble anode such as a titanium (Ti) plate. An anode 21 coated with a platinum iridium-based noble metal and a material to be plated, which is a cathode 22, for example, a metal plate to be plated, which forms a printed circuit board, are provided soaked in the electrolytic solution. Further, a DC power supply E is connected to the anode 21 and the cathode 22, so that a predetermined DC current (plating current) is supplied to each of the electrodes 21 and 22 during plating.
[0013]
Further, a circulation pump 23 for circulating the electrolytic solution is connected to the plating bath 20 via a circulation path in order to suppress the concentration of the electrolytic solution in the plating bath 20 from varying. A concentration detector for detecting the concentration of copper ions in the circulated electrolyte in terms of, for example, copper sulfate, for example, a colorimeter 3 using an absorptiometric method is provided.
[0014]
The details of the colorimeter 3 will be described in detail with reference to FIG. 2. In the figure, reference numeral 30 denotes an absorption cell part which is a sample passage part partially constituted by a light transmitting member, A supply path 31 for supplying the sample liquid from the circulation pump 23 to the absorption cell unit 30 and a discharge path 32 for discharging the sample are connected to each other. In addition, an optical sensor is provided which includes a light source 33 serving as a light emitting unit opposed to each other with the light transmitting member of the absorption cell unit 30 interposed therebetween, and a light receiving unit 34 for converting received light into an electric quantity. Further, between the absorption cell section 30 and the light receiving section 34, impurities in the electrolytic solution, for example, titanium (Ti) eluted from the anode 21 slightly when energized, or iron (Fe) eluted from a liquid contact part of a pump or a pipe. ) Is provided with an optical filter 35 that allows light having a predetermined wavelength, for example, 500 nm to 600 nm, for example, 540 nm, of the light emitted from the light source 33 to pass therethrough. In addition, 36 is an amplifying unit, and 37 is an output unit.
[0015]
Returning to FIG. 1, reference numeral 40 in the figure denotes a dissolving tank serving as a copper dissolving means for dissolving, for example, copper oxide (CuO), which is a replenishing material for copper ions, in the electrolytic solution overflowing from the plating bath 20. An opening / closing mechanism 41a such as a damper for supplying a predetermined amount of copper oxide powder, for example, is provided above the melting tank 40, and a hopper 41 for storing the copper oxide powder is provided. Further, the inside of the dissolving tank 40 is partitioned by a partition member 42, for example, divided into three tanks 43a, 43b, and 43c. If these liquid storage sections 43a to 43c are referred to as a first liquid storage section 43a, a second liquid storage section 43b, and a third liquid storage section 43c in order from the upstream side, the first liquid storage section 43a to which the copper oxide is supplied. The liquid storage section 43a is provided with a stirring means 44 for promoting the dissolution of copper oxide and making the copper concentration in the tank uniform. Further, a supply pump 48 for supplying an electrolytic solution replenished with copper to the plating bath 20 is connected to a bottom side of the third liquid storage section 43c via a supply path. Further, a liquid flow regulating plate 47 is provided so that the copper oxide supplied to the first liquid storage section 43a does not directly go to a supply pump 48 disposed in a subsequent stage without being dissolved. Note that F in the figure is a filter for removing insoluble residues in the electrolytic solution.
[0016]
Further, in the figure, reference numeral 5 denotes a control unit, which controls the rotation mechanism 41a of the hopper 41 when the detected value of the copper concentration detected by, for example, the colorimeter 3 falls below a predetermined setting value L for the start of feeding. Is opened and the supply operation of copper is started. On the other hand, when the detected value of the copper concentration exceeds a predetermined setting value H for stopping the supply, the rotating mechanism 41a is closed to stop the supply operation of copper. It has a function of controlling the supply operation based on the detected value of the copper concentration detected by the colorimeter 3.
[0017]
Here, commercially available copper oxide may be used, but it is preferable to use a copper oxide having excellent solubility in sulfuric acid and easy solubility. To briefly explain an example of a method for producing this easily soluble copper oxide, first, basic copper carbonate as a raw material is supplied to a heating furnace, for example, a rotary kiln, and the basic copper carbonate is directly burned, for example. In order to prevent the heating atmosphere from becoming a reducing atmosphere by heating at a temperature of, for example, heating to a temperature of 250 ° C. or higher and 800 ° C. or lower to promote thermal decomposition to generate copper oxide. Subsequently, the copper oxide is washed with, for example, pure water or ultrapure water, and then the moisture is removed by a centrifugal separator, followed by drying with a dryer to obtain copper oxide as a powder. The copper oxide thus obtained has excellent easy dissolving properties for free sulfuric acid, and therefore, the copper oxide supplied from the hopper 41 is rapidly dissolved in sulfuric acid. Therefore, the time from the introduction of the copper oxide until the copper concentration (detected value of the colorimeter 3) of the electrolytic solution held by the plating apparatus stops decreasing, and the undissolved remaining in the dissolving tank 40 is further reduced. The copper oxide melts with a time lag to prevent the copper concentration from increasing even though the copper input was stopped, so that the timing to input the copper oxide is simpler and easier to control. This is a good idea.
[0018]
Next, a step of performing a plating process using the above-described plating apparatus will be described. First, copper oxide is dissolved in the dissolving tank 40 so that the concentration of copper sulfate becomes, for example, 160 to 195 g / l and the concentration of free sulfuric acid becomes, for example, 90 to 130 g / l, and a predetermined addition for flattening the plating surface is further performed. The electrolytic solution prepared by supplying the agent from a supply source (not shown) is supplied to the plating bath 20 by the circulation pump 48 to form a bath. Then, the electrolyte solution overflowing from the plating bath 20 is returned to the first solution storage section 43a, so that the electrolyte solution is circulated in the plating apparatus system.
[0019]
Here, a sample of the electrolytic solution in the plating bath 20 is supplied to the colorimeter 3 by the circulation pump 23, and the detection of the copper concentration is started by the colorimeter 3. In the colorimeter 3, the light emitted from the light source 33 is partially absorbed by the sample flowing through the absorption cell 30, and the light that has passed through the optical filter 35 among the light that has not been absorbed is passed through the optical filter 35. The light receiving unit 34 receives light having a wavelength of, for example, 540 nm, and converts the light into an electric quantity. After being amplified by the amplifying unit 36, it is output to the control unit 5 via the output unit 37. The control unit 5 calculates the concentration of copper sulfate corresponding to the quantity of electricity, which is a signal from the output unit 37, based on, for example, a function created in advance (for example, corresponding to the calibration curve shown in FIG. 3). Gives the concentration of copper sulfate. FIG. 3A is a calibration curve showing the relationship between the concentration of copper sulfate and the absorbance, and FIG. 3B is a calibration curve showing the relationship between the concentration of copper sulfate and the converted output. Both were created by conducting tests in advance.
[0020]
Subsequently, the copper concentration is detected by the colorimeter 3 as described above, and the copper concentration is filled in the plating bath 20 and the dissolution bath 40 in order to reduce the concentration distribution of the electrolytic solution in the plating apparatus system. In order to reduce the difference in the concentration of the electrolyte, a DC current is supplied from the DC power supply E to each of the electrodes 21 and 22 in a state where the circulation of the electrolyte by the circulation pump 48 is continuously performed, and the plating process is started. . At this time, oxygen is generated at the anode 21 according to the reaction formulas 1 and 2 described in “Prior Art”, while copper ions in the electrolytic solution precipitate on the surface of the material to be plated, which is the cathode 22, so that the coating is performed. Copper plating is performed on the plating material.
[0021]
The following description focuses on the copper concentration in the electrolytic solution at the time of plating, but it can be easily understood by referring to FIG. 4 showing an example of how the concentration changes with time. First, as described above, the concentration of copper sulfate in the electrolytic solution decreases, while the concentration of free sulfuric acid in the electrolytic solution increases, because the copper ions in the electrolytic solution precipitate on the surface of the material to be plated. At this time, for example, the detection value of the colorimeter 3 is continuously sampled, and it is determined whether or not the detection value is within the set value. Then, when the concentration of copper sulfate detected by the colorimeter 3 at time t1 falls below a predetermined setting value L for the start of charging, the opening / closing mechanism 41a opens and a predetermined amount of copper oxide is charged into the melting tank 41, Then, copper ions are supplied by dissolving the copper oxide. When the detection value of the colorimeter 3 is sampled and copper oxide is introduced in this way, the concentration of copper sulfate in the electrolytic solution increases, and the concentration of copper sulfate detected by the colorimeter 3 at time t2 is determined in advance. When the value exceeds the determined value H for stopping the closing, the opening / closing mechanism 41a is closed, and the closing operation is stopped until the value falls below the set value L (time t3). Here, the set value L is set to be larger than 160 g / liter, and the set value H is set to be smaller than 195 g / liter. By setting a margin with respect to the target concentration, the copper concentration does not deviate from the target concentration. I have.
[0022]
According to the above-described embodiment, the concentration of copper sulfate contained in the electrolytic solution in the plating bath 20 is detected using the colorimeter 3, and copper oxide is replenished based on the detected value. Replenishment timing can be easily set. For this reason, the copper concentration can be maintained in a predetermined high concentration region in a narrow range, so that the through holes 17 of the multilayer printed circuit board 16 shown in FIG. Occurrence can be suppressed. As a result, good copper plating can be performed. The colorimeter 3 can be obtained at a lower price than measuring devices such as an atomic absorption spectrometer and an ion chromatograph, and is advantageous in that cost can be reduced.
[0023]
Further, according to the above-described embodiment, in order to avoid the absorption band of impurities such as titanium and iron, which are considered to surely occur in the electrolytic solution when performing copper plating as described above, By setting the wavelength of the measurement light of the colorimeter 3 to 500 nm or more, preferably 540 nm, the influence of the impurities is small as is clear from the results of the examples described later. Therefore, the concentration of copper sulfate can be detected with high accuracy, and as a result, the concentration of copper in the electrolytic solution can be controlled with high accuracy. Therefore, good copper plating can be performed. Further, although not an impurity, the absorption band of the additive added to the electrolytic solution is at 500 nm or less, so that the influence of the additive can be avoided. The upper limit of the wavelength is not particularly defined, but is preferably 600 nm or less from the reason of the absorption wavelength of copper sulfate.
[0024]
In the copper plating apparatus of the present invention, the replenishing material is not limited to copper oxide, but may be a copper compound such as copper powder, cuprous oxide, or copper carbonate. Even with such a configuration, the same effects as those described above can be obtained.
[0025]
Further, in the copper plating apparatus of the present invention, the influence of impurities is avoided by the above-described method, and a good correlation between the copper sulfate concentration and the absorbance (the calibration curve shown in FIG. 3) is grasped. The present invention can also be applied to an electrolytic solution having a copper concentration lower than 160 g / liter, for example, a concentration of 90 to 100 g / liter as described in "Prior Art". Further, the present invention can be applied to a dilute electrolyte of 30 g / liter. Therefore, highly accurate concentration control can be performed for a wide range of copper ion concentrations.
[0026]
【Example】
Next, examples performed to confirm the effects of the present invention will be described.
[0027]
(Example 1)
This embodiment is an embodiment in which copper plating is performed using the above-described plating apparatus. The plating bath composition and plating conditions are shown below.
Initial concentration of copper sulphate (CuSO ₄ .5H ₂ O); 190 g / l Initial concentration of free sulfur (H ₂ SO ₄ ); 90 g / l current density; 3 A / dm ²
Anode 21; Insoluble anodic plating bath temperature; 25 ° C
The capacity of the plating bath 20; the size of the object to be plated, 20 liters; 200 mm × 200 mm (electrolytic area 4 dm ² )
Using such a plating apparatus, a copper plating process was performed for an energization time of 49 hours or more. The control value of the copper sulfate concentration was 180 to 195 g / liter, the set value L was set to 185 g / liter, and the set value H was set to 190 g / liter. FIG. 5 shows the results of the change over time in the concentration of copper sulfate in the plating bath.
[0028]
(Example 2)
This example is an example performed to confirm the measurement accuracy of the colorimeter 3. The composition of the electrolytic solution was such that the concentration of copper sulfate was 50 g / l, the concentration of free sulfur was 200 g / l, and titanium was 20 ppm. Subsequently, the temperature of the electrolyte solution sample was adjusted to 25 ° C., and the absorbance (ABS) was measured using the colorimeter 3 in the range of the measurement wavelength of 300 to 600 nm. FIG. 6 shows a graph of the result.
[0029]
(Comparative Example 1)
This example is a comparative example in which the same test as in Example 2 was performed except that titanium was not added. FIG. 6 shows a graph obtained by measuring the absorbance for each wavelength and graphing the same as in Example 2.
[0030]
(Example 3)
In this example, iron was added in an amount of 50 ppm and 100 ppm, respectively, in place of titanium. Further, the concentration of copper sulfate (CuSO ₄ .5H ₂ O) was 180 g / l, and the concentration of free sulfuric acid (H ₂ SO ₄ ) was 90 g / l. This is an example in which a test similar to that of Example 2 was performed except that the test was performed. FIG. 7 shows absorbance measured for each wavelength and graphed.
[0031]
(Comparative Example 2)
This example is a comparative example in which the same test as in Example 3 was performed except that iron was not added. FIG. 7 shows a graph obtained by measuring the absorbance for each wavelength and graphing the same as in Example 3.
[0032]
(Results and consideration of Example 1)
As is clear from the results of FIG. 5, when copper plating is started, the concentration of copper sulfate decreases with time. When the concentration of copper sulfate falls below the set value L, the operation of feeding copper oxide is started, and the concentration of copper sulfate rises before falling below 180 g / liter. Thereafter, the supply of copper oxide is continued to increase the sulfuric acid concentration. When the concentration exceeds the set value H, the supply of copper oxide is stopped and the concentration of copper sulfate decreases before the concentration exceeds 195 g / liter. That is, it was confirmed that the copper ions in the plating bath can be controlled by performing such operations repeatedly even when continuous electrolytic plating is performed. In addition, it was confirmed that the copper plating obtained in this way was flat and had almost no voids.
[0033]
(Results and consideration of Example 2 and Comparative Example 1)
As is clear from the results in FIG. 6, the absorbance in a certain wavelength region is different between the case where the electrolyte solution as a sample contains titanium and the case where it does not contain titanium. That is, when titanium is contained, it is clear that there is an absorption band of titanium in a range of 340 to 500 nm with a peak at about 410 nm. Therefore, it was confirmed that the influence of titanium can be avoided by setting the wavelength of the measurement light to 500 nm or more, preferably 540 nm or more.
[0034]
(Results and Considerations of Example 3 and Comparative Example 2)
As is clear from the results of FIG. 7, the absorbance differs between the case where iron is contained in the electrolytic solution and the case where iron is not contained, as in the case where titanium is contained, and the wavelength is smaller than 420 nm. It can be seen that iron is affected in the range. Further, it can be seen that the higher the iron concentration, the greater the influence. Therefore, it was confirmed that the influence of iron can be avoided by setting the wavelength of the measurement light to 420 nm or more, and the influence of titanium can be avoided at the same time by setting it to 500 nm or more.
[0035]
【The invention's effect】
As described above, according to the copper plating apparatus of the present invention, replenishment is performed by detecting the concentration of copper contained in the electrolytic solution of the plating bath using a colorimeter and replenishing copper based on the detected value. Since it is possible to easily set the timing for performing this, it is possible to control the copper ion concentration of the electrolytic solution with high accuracy. Further, by setting the measurement light of the colorimeter to a predetermined wavelength, it is possible to avoid the influence of impurities such as titanium and iron, so that good copper plating can be performed. Further, since the copper ion concentration can be controlled with high accuracy over a wide range of copper ion concentrations, copper plating suitable for various uses can be favorably performed using a common apparatus. As a result, good copper plating can be performed.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing an embodiment of a copper plating apparatus according to the present invention.
FIG. 2 is a perspective view schematically showing a colorimeter used for the copper plating apparatus according to the present invention.
FIG. 3 is an explanatory diagram showing a calibration curve of a colorimeter used in the copper plating apparatus according to the present invention.
FIG. 4 is an explanatory diagram showing a change in the concentration of copper sulfate when plating is performed using the copper plating apparatus according to the present invention.
FIG. 5 is a characteristic diagram showing a result of an example performed to confirm an effect of the present invention.
FIG. 6 is a characteristic diagram showing a result of an example performed to confirm an effect of the present invention.
FIG. 7 is a characteristic diagram showing a result of an example performed to confirm an effect of the present invention.
FIG. 8 is an explanatory view showing a conventional copper plating apparatus.
FIG. 9 is an explanatory view showing a multilayer printed circuit board to which copper plating is applied.
[Explanation of symbols]
Reference Signs List 20 plating bath 21 anode 22 cathode 3 colorimeter 30 absorption cell 33 light source 34 light receiving unit 35 optical filter 40 melting tank 41 hopper 5 control unit

Claims (5)

In a plating apparatus including an insoluble anode, a body to be plated forming a cathode, and a plating bath filled with an electrolytic solution containing copper as a plating material,
A colorimeter having a wavelength of measurement light of 500 nm or more for detecting the concentration of copper in the plating bath,
A dissolution tank for dissolving copper in the electrolytic solution,
Circulating means for circulating the electrolyte between the plating bath and the dissolving tank,
Supply means for supplying copper to the dissolving tank so that the copper concentration in the plating bath becomes a preset value based on the detected value of the copper concentration detected by the colorimeter. A copper plating apparatus comprising: The copper plating apparatus according to claim 1, wherein the electrolytic solution in the plating bath contains copper sulfate and free sulfuric acid, and the concentration of the copper sulfate is controlled to 160 g / liter to 195 g / liter. The copper plating apparatus according to claim 2, wherein the concentration of the free sulfuric acid is 90 g / L to 130 g / L. 4. The copper plating apparatus according to claim 1, wherein the copper supplied to the melting tank is copper oxide. The copper oxide is easily soluble, obtained by thermally decomposing basic copper carbonate by heating to 250 ° C. to 800 ° C. in an atmosphere that does not become a reducing atmosphere, and then washing with water. The copper plating apparatus according to claim 4, wherein

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