Anode for electroplating and method for electroplating using anode

Abstract

Provided is an anode for electroplating which uses an aqueous solution as an electrolytic solution, and the anode which is low in potential when compared with a conventional anode, able to decrease an electrolytic voltage and an electric energy consumption rate and may also be used as an anode for electroplating various types of metals, and which is low in cost. Also provided is a method for electroplating which uses an aqueous solution as an electrolytic solution, in which the anode is low in potential and electrolytic voltage, thereby making it possible to decrease the electric energy consumption rate. The anode for electroplating of the present invention is an anode for electroplating which uses an aqueous solution as an electrolytic solution, in which a catalytic layer containing amorphous ruthenium oxide and amorphous tantalum oxide is formed on a conductive substrate.

Claims

1. A method for electroplating which comprises electroplating a desired metal present in an aqueous electrolytic solution onto a cathode with an anode comprising a conductive substrate and a catalytic layer formed on the conductive substrate, and the catalytic layer is composed of amorphous ruthenium oxide and amorphous tantalum oxide and does not contain IrO.sub.2.

2. The method for electroplating according to claim 1, wherein the desired metal is any one of copper, zinc, tin, nickel, cobalt, lead, chromium, indium, platinum, silver, iridium, ruthenium and palladium.

3. The method for electroplating according to claim 1, wherein a mole ratio of ruthenium to tantalum in the catalytic layer is 50:50.

4. The method for electroplating according to claim 3, wherein the desired metal is any one of copper, zinc, tin, nickel, cobalt, lead, chromium, indium, platinum, silver, iridium, ruthenium and palladium.

5. The method for electroplating according to claim 1, wherein the anode further comprises an intermediate layer formed between the catalytic layer and the conductive substrate.

6. The method for electroplating according to claim 5, wherein the intermediate layer contains crystalline iridium oxide and amorphous tantalum oxide.

7. The method for electroplating according to claim 6, wherein the desired metal is any one of copper, zinc, tin, nickel, cobalt, lead, chromium, indium, platinum, silver, iridium, ruthenium and palladium.

8. The method for electroplating according to claim 5, wherein the desired metal is any one of copper, zinc, tin, nickel, cobalt, lead, chromium, indium, platinum, silver, iridium, ruthenium and palladium.

9. The method for electroplating according to claim 1, wherein the catalytic layer consists of amorphous ruthenium oxide and amorphous tantalum oxide.

Description

DESCRIPTION OF EMBODIMENTS

(1) Hereinafter, the present invention will be described in more detail in accordance with the Examples and Comparative Examples. However, the present invention is not limited to the following Examples. The present invention is also applicable to electroplating of metals other than zinc, copper, nickel and platinum.

EXAMPLES

Electrogalvanizing

Example 1

(2) A commercially available titanium plate (5 cm in length, 1 cm in width, 1 mm in thickness) was immersed and etched in a 10% oxalic acid solution at 90 C. for 60 minutes and then washed and dried. Next, prepared was a coating solution which was obtained by adding ruthenium trichloride trihydrate (RuCl.sub.3.3H.sub.2O) and tantalum pentachloride (TaCl.sub.5) to a butanol (n-C.sub.4H.sub.9OH) solution containing 6 vol % concentrated hydrochloric acid so that the mole ratio of ruthenium to tantalum is 50:50 and the total of ruthenium and tantalum is 50 g/L in terms of metal. This coating solution was applied to the titanium plate dried as mentioned above, dried at 120 C. for 10 minutes, and then thermally decomposed for 20 minutes in an electric furnace that was held at 280 C. This series of application, drying, and thermal decomposition was repeated seven times in total in order to prepare an anode for electroplating of Example 1, the anode having a catalytic layer formed on the titanium plate that was a conductive substrate.

(3) An X-ray diffraction analysis of the structure of the anode for electroplating of Example 1 showed that a diffraction peak equivalent to RuO.sub.2 was not observed in an X-ray diffraction image and a diffraction peak equivalent to Ta.sub.2O.sub.5 was not observed. Further, XPS (X-ray photoelectron spectroscopy) was performed to make an analysis of chemical states of ruthenium, tantalum and oxygen, thereby it was found that the catalytic layer was a mixture of RuO.sub.2 and Ta.sub.2O.sub.5. That is, the anode for electroplating of Example 1 had a catalytic layer composed of amorphous ruthenium oxide and amorphous tantalum oxide formed on the titanium plate.

(4) A commercially available electrogalvanizing solution (made by Marui Galvanizing Co., Ltd., zinc concentration of about 80 g/L, pH=1) was used as an electrolytic solution and a zinc plate (2 cm2 cm) was immersed in the electrolytic solution as a cathode. Furthermore, the above-described anode for electroplating was mounted in a polytetrafluoroethylene holder, and then, with the electrode area in contact with the electrolytic solution restricted to 1 cm.sup.2, was disposed in the same electrolytic solution so as to be opposed to the aforementioned cathode with a predetermined inter-electrode distance. Further, a saturated potassium chloride aqueous solution was placed into a vessel different from that of the electrolytic solution and a commercially available silver-silver chloride electrode was immersed in the saturated potassium chloride aqueous solution as a reference electrode. The saturated potassium chloride aqueous solution was connected to the electrolytic solution by using a salt bridge and a Luggin capillary to prepare a three-electrode type electrochemical measurement cell. An electrolytic current with the current density of either 10 mA/cm.sup.2 or 20 mA/cm.sup.2 based on an electrode area of the anode for electroplating was allowed to flow between the anode for electroplating and the cathode, while electrogalvanizing was performed on the cathode, thereby measuring a potential of the anode for electroplating with respect to the reference electrode. It is noted that the electrolytic solution was kept at a temperature of 40 C. by using a thermobath.

Comparative Example 1

(5) A commercially available titanium plate (5 cm in length, 1 cm in width, 1 mm in thickness) was immersed and etched in a 10% oxalic acid solution at 90 C. for 60 minutes and then washed and dried. Next, prepared was a coating solution which was obtained by adding hexachloroiridic acid hexahydrate (H.sub.2IrCl.sub.6.6H.sub.2O) and tantalum chloride (TaCl.sub.5) to a butanol (n-C.sub.4H.sub.9OH) solution containing 6 vol % concentrated hydrochloric acid so that a mole ratio of iridium to tantalum was 50:50 and a total of iridium and tantalum was 70 g/L in terms of metal. This coating solution was applied to the titanium plate dried as mentioned above, dried at 120 C. for 10 minutes, and then thermally decomposed for 20 minutes in an electric furnace that was held at 360 C. This series of application, drying and thermal decomposition was repeated five times in total in order to prepare an anode for electroplating of Comparative Example 1 in which a catalytic layer was formed on the titanium plate that was a conductive substrate.

(6) An X-ray diffraction analysis of the structure of the anode for electroplating of Comparative Example 1 showed that a diffraction peak equivalent to IrO.sub.2 was not observed in an X-ray diffraction image and a diffraction peak equivalent to Ta.sub.2O.sub.5 was not observed. Further, XPS (X-ray photoelectron spectroscopy) was performed to make an analysis of chemical states of iridium, tantalum and oxygen, thereby it was found that the catalytic layer was a mixture of IrO.sub.2 and Ta.sub.2O.sub.5. That is, the anode for electroplating of Comparative Example 1 had a catalytic layer composed of amorphous iridium oxide and amorphous tantalum oxide formed on the titanium plate.

(7) Under the same conditions as those of Example 1 except that the anode for electroplating of Comparative Example 1 was used in place of the anode for electroplating of Example 1, an electrolytic current with the current density of either 10 mA/cm.sup.2 or 20 mA/cm.sup.2 based on an electrode area of the anode for electroplating was allowed to flow between the anode for electroplating and the cathode, measurement was made for a potential of the anode for electroplating with respect to the reference electrode, while electrogalvanizing on the cathode was performed.

(8) The anode for electroplating of Example 1 or Comparative Example 1 was used to measure a potential of the anode on performing electrogalvanizing, the results of which are shown in Table 1.

(9) TABLE-US-00001 TABLE 1 Difference in anode potential Anode potential (Degree of improvement) Current Example 1 Comparative Comparative Example 1- density Example 1 Example 1 10 mA/cm.sup.2 1.39 V 1.43 V 0.04 V 20 mA/cm.sup.2 1.47 V 1.52 V 0.05 V

(10) As shown in Table 1, where electrogalvanizing was performed by using the anode for electroplating of Example 1 having a catalytic layer composed of amorphous ruthenium oxide and amorphous tantalum oxide formed therein, the electrolytic voltage was decreased by 0.04 V to 0.05 V, when compared with the case in which the anode for electroplating of Comparative Example 1 having a catalytic layer composed of amorphous iridium oxide and amorphous tantalum oxide formed therein was used. That is, the anode for electroplating (Example 1) having a catalytic layer composed of amorphous ruthenium oxide and amorphous tantalum oxide formed therein was further decreased in potential than the anode for electroplating (Comparative Example 1) having a catalytic layer composed of amorphous iridium oxide and amorphous tantalum oxide formed therein. Thereby, it was found that a decrease in electrolytic voltage for electrogalvanizing was realized.

Copper Electroplating

Example 2

(11) Under the same conditions as those of Example 1 except that the electrolytic solution of Example 1 was changed to a commercially available copper electroplating solution (made by Marui Galvanizing Co., Ltd., copper concentration of about 91 g/L, pH=6.6), measurement was made for a potential of the anode for electroplating with respect to the reference electrode, while copper electroplating was performed.

Comparative Example 2

(12) Under the same conditions as those of Comparative Example 1 except that the electrolytic solution of Comparative Example 1 was changed to a commercially available copper electroplating solution (made by Marui Galvanizing Co., Ltd., copper concentration of about 91 g/L, pH=6.6), measurement was made for a potential of the anode for electroplating with respect to the reference electrode, while copper electroplating was performed.

(13) The anode for electroplating of Example 2 or Comparative Example 2 was used to measure a potential of the anode on performing copper electroplating, the results of which are shown in Table 2.

(14) TABLE-US-00002 TABLE 2 Difference in anode potential Anode potential (Degree of improvement) Current Example 2 Comparative Comparative Example 2- density Example 2 Example 2 10 mA/cm.sup.2 1.21 V 1.31 V 0.10 V 20 mA/cm.sup.2 1.30 V 1.39 V 0.09 V

(15) As shown in Table 2, where copper electroplating was performed by using the anode for electroplating of Example 2 having a catalytic layer composed of amorphous ruthenium oxide and amorphous tantalum oxide formed therein, the electrolytic voltage thereof was decreased by 0.09 V to 0.10 V, when compared with the case in which the anode for electroplating of Comparative Example 2 having a catalytic layer composed of amorphous iridium oxide and amorphous tantalum oxide formed therein was used. That is, the anode for electroplating (Example 2) having a catalytic layer composed of amorphous ruthenium oxide and amorphous tantalum oxide formed therein was further decreased in potential than the anode for electroplating (Comparative Example 2) having a catalytic layer composed of amorphous iridium oxide and amorphous tantalum oxide formed therein. Thereby, it was found that a decrease in electrolytic voltage for copper electroplating was realized.

Nickel Electroplating

Example 3

(16) Under the same conditions as those of Example 1 except that the electrolytic solution of Example 1 was changed to a commercially available nickel electroplating solution (made by Marui Galvanizing Co., Ltd., nickel salt concentration of 18%, pH=7.7), measurement was made for a potential of the anode for electroplating with respect to the reference electrode, while nickel electroplating was performed.

Comparative Example 3

(17) Under the same conditions as those of Comparative Example 1 except that the electrolytic solution of Comparative Example 1 was changed to a commercially available nickel electroplating solution (made by Marui Galvanizing Co., Ltd., nickel salt concentration of 18%, pH=7.7), measurement was made for a potential of the anode for electroplating with respect to the reference electrode, while nickel electroplating was performed.

(18) The anode for electroplating of Example 3 or Comparative Example 3 was used to measure a potential of the anode on performing nickel electroplating, the results of which are shown in Table 3.

(19) TABLE-US-00003 TABLE 3 Difference in anode potential Anode potential (Degree of improvement) Current Example 3 Comparative Comparative Example 3- density Example 3 Example 3 10 mA/cm.sup.2 0.98 V 1.13 V 0.15 V 20 mA/cm.sup.2 1.07 V 1.22 V 0.15 V

(20) As shown in Table 3, where nickel electroplating was performed by using the anode for electroplating of Example 3 having a catalytic layer composed of amorphous ruthenium oxide and amorphous tantalum oxide formed therein, the electrolytic voltage was decreased by 0.15 V, when compared with the case in which the anode for electroplating of Comparative Example 3 having a catalytic layer composed of amorphous iridium oxide and amorphous tantalum oxide formed therein was used. That is, the anode for electroplating (Example 3) having a catalytic layer composed of amorphous ruthenium oxide and amorphous tantalum oxide formed therein was further decreased in potential than the anode for electroplating (Comparative Example 3) having a catalytic layer composed of amorphous iridium oxide and amorphous tantalum oxide formed therein. Thereby, it was found that a decrease in electrolytic voltage for nickel electroplating was realized.

Platinum Electroplating

Example 4

(21) Under the same conditions as those of Example 1 except that the electrolytic solution of Example 1 was changed to a commercially available platinum electroplating solution (made by Marui Galvanizing Co., Ltd., platinum compound concentration of about 2%, potassium hydroxide concentration of about 1.5%, pH=12.2), measurement was made for a potential of the anode for electroplating with respect to the reference electrode, while platinum electroplating was performed.

Comparative Example 4

(22) Under the same conditions as those of Comparative Example 1 except that the electrolytic solution of Comparative Example 1 was changed to a commercially available platinum electroplating solution (made by Marui Galvanizing Co., Ltd., platinum compound concentration of about 2%, potassium hydroxide concentration of about 1.5%, pH=12.2), measurement was made for a potential of the anode for electroplating with respect to the reference electrode, while platinum electroplating was performed.

(23) Where platinum electroplating was performed by using the anode for electroplating of Example 4, a potential of the anode was 0.95 V at the current density of 10 mA/cm.sup.2 and 1.24 V at the current density of 20 mA/cm.sup.2. It is noted that measurement was made for a potential of the anode for electroplating of Comparative Example 4 as well, however, the potential was not stabilized from immediately after the start of electrolysis, and, the potential acutely increased, thereby it was not possible to measure a stable potential of the anode. When the anode for electroplating was taken out from the electrolytic solution after measurement of the potential of the anode of Comparative Example 4, it was found that the catalytic layer on the titanium plate was changed in shape and the catalytic layer was deteriorated.

Tin Electroplating

Example 5

(24) Under the same conditions as those of Example 1 except that the electrolytic solution of Example 1 was changed to a commercially available tin electroplating solution (made by Marui Galvanizing Co., Ltd., pH=0.13) and the temperature was changed to 25 C., measurement was made for a potential of the anode for electroplating with respect to the reference electrode, while tin electroplating was performed.

Comparative Example 5

(25) Under the same conditions as those of Comparative Example 1 except that the electrolytic solution of Comparative Example 1 was changed to a commercially available tin electroplating solution (made by Marui Galvanizing Co., Ltd., pH=0.13) and the temperature was changed to 25 C., measurement was made for a potential of the anode for electroplating with respect to the reference electrode, while tin electroplating was performed.

(26) The anode for electroplating of Example 5 or Comparative Example 5 was used to measure a potential of the anode on performing tin electroplating, the results of which are shown in Table 4.

(27) TABLE-US-00004 TABLE 4 Difference in anode potential Anode potential (Degree of improvement) Current Example 5 Comparative Comparative Example 5- density Example 5 Example 5 10 mA/cm.sup.2 1.44 V 1.66 V 0.22 V

(28) As shown in Table 4, where tin electroplating was performed by using the anode for electroplating of Example 5 having a catalytic layer composed of amorphous ruthenium oxide and amorphous tantalum oxide formed therein, the electrolytic voltage was decreased by 0.22 V, when compared with the case in which the anode for electroplating of Comparative Example 5 having a catalytic layer composed of amorphous iridium oxide and amorphous tantalum oxide formed therein was used. That is, the anode for electroplating (Example 5) having a catalytic layer composed of amorphous ruthenium oxide and amorphous tantalum oxide formed therein was further decreased in potential than the anode for electroplating (Comparative Example 5) having a catalytic layer composed of amorphous iridium oxide and amorphous tantalum oxide formed therein. Thereby, it was found that a decrease in electrolytic voltage for tin electroplating was realized.

INDUSTRIAL APPLICABILITY

(29) The present invention is able to provide an anode for electroplating which is high in catalysis for a main reaction of the anode and low in potential, when compared with a lead electrode, a lead alloy electrode, a metal-coated electrode and a metal oxide-coated electrode in electroplating which uses an aqueous solution as an electrolytic solution, thereby making it possible to decrease an electrolytic voltage in electroplating and also to lower an electric energy consumption rate for a metal to be electroplated, and the anode which may be used as an anode for electroplating various types of metals and also able to decrease costs of a catalytic layer and those of the anode, when compared with a metal oxide-coated electrode used in electroplating, in particular, an electrode in which a conductive substrate is coated with a catalytic layer containing iridium oxide. The present invention is also able to provide a method for electroplating which uses an aqueous solution as an electrolytic solution, and the method for electroplating in which the anode is low in potential and electrolytic voltage, thereby making it possible to decrease an electric energy consumption rate in electroplating and also decrease initial cost and maintenance cost necessary for the anode and also decrease the entire cost necessary for electroplating.