TWI390087B - Method for engineer anode copper balls for electroplating - Google Patents

Description

Method for manufacturing anode copper ball for electroplating

The present invention relates to a method for producing an anode copper ball for electroplating used as a copper raw material in electrolytic plating of copper.

Conventionally, in a method of performing copper plating on a printed wiring board such as a mobile phone or a computer, copper is used as an anode, and a printed wiring board is used as a cathode, and is immersed in a plating bath such as a dilute sulfuric acid solution, and electrolytic plating using electricity is widely used. In the electrolytic plating, copper as an anode is eluted into a dilute sulfuric acid solution, and copper plating is performed on the surface of the printed wiring board as a cathode.

In this case, a spherical copper material (anode copper ball for electroplating) is used, and a cage made of a corrosion-resistant material such as Ti is used in the plating bath, and an anode copper ball for plating is sequentially placed in the cage to constitute the electrolysis. The anode of the electroplated copper material. Since the copper material is dissolved in the solution, it is sequentially consumed, but in combination with the consumption amount, the anode copper ball for electroplating is loaded into the Ti cage, so that electrolytic plating can be continuously performed.

The anode copper ball for electroplating is formed by cold forging copper material. Here, in the cold forging step, the copper material is processed by the mechanical application of pressure, and there is a problem that the working oil or lubricating oil used for the mechanical part is attached to the surface of the obtained copper ball by forging. . The method of removing the amount of the oil adhering to the copper-based member is immersed in an aqueous solution of an alkaline degreaser having a pH of 12 or more as shown in Patent Document 1, and then subjected to pickling or immersion in acetone or ethanol shown in Patent Document 2. The method of washing in the liquid.

[Patent Document 1] Japanese Patent Laid-Open No. Hei 3-223482 (Patent Document 2) Japanese Laid-Open Patent Publication No. Hei 9-125275

However, in the oil amount removal method shown in Patent Document 1, since a highly alkaline degreaser aqueous solution having a pH of 12 or more is used, it is necessary to form a tank or a supply device for discharging the degreaser aqueous solution with a corrosion-resistant material, and to discharge it. The device has a problem that causes its manufacturing cost to become high. Further, since a strong alkaline degreasing agent is used, the use management requires a lot of labor and time, and it is necessary to treat the waste liquid of the degreasing agent aqueous solution, resulting in a significant increase in environmental load, which causes a problem that the waste liquid treatment cost is required.

In the oil amount removal method disclosed in Patent Document 1, the method of removing the oxide film layer formed on the surface of the copper-based member by immersing in the aqueous solution of the alkaline degreaser is pickled, and therefore it is necessary to use so-called sulfuric acid. Or an acidic agent such as hydrochloric acid. Therefore, as in the case of using the above-described strongly alkaline degreaser, it is necessary to form a groove, a supply device, and a discharge device with a material having corrosion resistance, which causes a problem of high manufacturing cost or labor and cost in management of use of an acidic drug. Problems such as environmental load such as waste liquid for treating acidic chemicals, disposal cost of waste liquid, and the like.

Moreover, in the oil amount removal method shown by the patent document 2, it is immersed in the copper-copper and ethanol liquid, and the liquid is stirred only by rocking a copper-type member, and the problem of the amount of oil which adhered strongly is not fully removed.

When the amount of oil remains on the surface of the anode copper ball for electroplating, the anode copper ball for electroplating is loaded into a plating bath such as a dilute sulfuric acid aqueous solution, thereby causing a problem that the amount of oil is mixed into the plating bath and is contaminated. Further, there is a problem that a sludge is generated due to the amount of the oil, and contamination is formed between the copper plating layers formed on the printed wiring board.

The present invention has been made in view of the above, and an object of the present invention is to provide an alkaline solution or an acidic solution which does not require an environmental load, and removes the amount of oil adhering to the surface of the copper ball in the forging step, thereby producing a high-quality plating. A method of manufacturing an anode copper ball.

In order to solve the above problems, the present invention provides a method for producing an anode copper ball for electroplating, which is used as a raw material for electrolytic plating of copper, and is characterized in that: a forging step of forming a copper material into a spherical shape by cold forging; a heating step of volatilizing the amount of oil adhering to the surface of the copper ball in the heating furnace by the forging step; and a barrel polishing step of polishing the copper ball after the heating step.

In the above method for producing an anode copper ball for electroplating, since the copper ball obtained by the forging step is heated in a heating furnace, the amount of oil adhering to the surface of the copper ball is volatilized and removed in the forging step, so that the oil can be surely removed. the amount. Further, since the barrel polishing is performed in a state where the amount of oil is removed, the surface of the anode copper ball for plating after the barrel polishing can be processed to be cleaner.

Moreover, the oxide film removal step of removing the oxide film formed on the surface of the copper ball by the heating step, and heating the copper ball to volatilize the amount of oil, the oxide film formed on the surface of the copper ball is oxidized. The membrane removal step is removed.

Further, the step of immersing the copper ball in the reducing solution by the oxide film removing step has a drying step of drying the copper ball immersed in the reducing solution, and the reducing solution is surely removed for heating. The oxide film formed in the furnace is subjected to barrel polishing after the copper balls immersed in the reducing solution are dried in the drying step.

Further, by setting the surrounding environment in the furnace of the heating furnace to the atmosphere of the reducing gas, the copper ball is prevented from being strongly formed on the surface thereof when the copper ball is heated in the heating furnace.

In the above method for producing an anode copper ball for electroplating, since it is not necessary to use an alkaline degreaser, the equipment cost and the management cost can be reduced, and the environmental load can be greatly reduced. Further, since the amount of oil can be surely removed by volatilizing the amount of oil, there is no possibility that the amount of oil is mixed into the plating bath, and an anode copper ball for electroplating which is stably plated can be provided.

Further, when heating is performed in a heating furnace, an oxide film is formed on the surface of the copper ball. However, since the oxide film can be removed by the oxide film removing step after the heating step, the film can be supplied without the oxide film. The copper ball, while the surface of the copper ball is processed into a shiny clean surface.

Further, since the oxide film can be removed by immersing the copper ball in the reducing solution, it is not necessary to use an acidic chemical solution, and the equipment cost and the management cost can be reduced, and the environmental load can be greatly reduced. Further, since the copper balls which have been immersed in the reducing solution are dried and supplied to the drum for polishing, it is possible to prevent the copper balls from being reoxidized and to process the surface of the copper balls into a glossy clean surface.

Further, by setting the atmosphere in the furnace of the heating furnace to a reducing gas atmosphere, the oxide film is not strongly formed on the surface of the copper ball. Therefore, in the oxide film removing step after the heating step, the oxide film is easily removed. The oxide film can be surely removed, and the copper ball without the oxide film is supplied while the roller is being polished, so that the surface of the copper ball can be processed into a shiny clean surface.

As described above, according to the present invention, it is possible to manufacture a high-quality anode copper ball for electroplating without using an alkaline solution causing a large environmental load and an acidic solution to remove the amount of oil adhering to the surface of the copper ball in the forging step. method.

Hereinafter, embodiments of the present invention will be described. Fig. 1 is a view showing the steps of a method for producing an anode copper ball for electroplating of the present invention. Further, the diameter of the anode copper ball for plating produced in the present embodiment was 55 mm.

First, a copper wire material that becomes a copper ball material is supplied. In the present embodiment, a copper wire having a diameter of 39 mm is used. The copper wire was cut at an appropriate length and loaded into a mold set in a cold forging machine. The inside of the model formed a spherical shape with a diameter of 55 mm. The copper wire inserted into the mold was forged to form a copper ball having a diameter of 55 mm. In this forging process, the lubricating oil or the working oil of the forging machine is present in the forging chamber, and the amount of oil adheres to the surface of the copper ball.

The copper ball to which the oil amount is attached is charged into the heating furnace. The heating furnace is a gas burner combustion furnace, which uses natural gas as a fuel, and a mixture ratio of air and fuel as a rich fuel to be burned, and the inside of the combustion furnace is set as a reducing surrounding environment. Here, the temperature in the heating furnace may be set to a temperature at which the amount of oil is volatilized, that is, 400 ° C or higher. When the temperature is too high, a load is applied to the furnace body of the combustion furnace, and an oxide film formed on the surface of the copper ball is thickened. Therefore, it is preferable to set it as 800 ° C or less. The copper ball is heated in a heating furnace, and the amount of oil adhered to the surface thereof is volatilized, so that the amount of oil can be surely removed. Here, although the inside of the heating furnace is a reducing surrounding environment, it is mixed into the atmosphere from the inlet or the discharge port of the copper ball, and a thin oxide film is formed on the surface of the copper ball.

Then, a copper ball which forms a thin oxide film in a heating furnace is immersed in a storage tank in which a reducing solution is stored. Specifically, an aqueous solution of isopropyl alcohol or an aqueous solution of ethylene glycol or the like can be used as the reducing solution. The oxide film formed on the surface of the copper ball can be removed by immersing in the reducing solution. Therefore, the surface of the copper ball is in a state in which no oil amount or oxide film exists.

Then, the copper ball from which the oil amount and the oxide film have been removed is supplied to the drying step. In the drying step, the copper ball is sprayed with air to dry the surface of the copper ball. The copper balls dried in this way are supplied to the barrel polishing device. The plurality of copper balls loaded into the barrel polishing device are vigorously stirred, causing the copper balls to collide with each other to grind the surface of the copper balls. Here, the copper ball can be dried while removing the amount of oil on the surface of the copper ball and the oxide film. Therefore, the surface of the copper ball after the barrel polishing is copper-colored, and can be processed into a glossy clean surface.

The anode copper ball for electroplating produced by the above method is supplied to a cage made of Ti disposed in an electroplating bath in which a dilute sulfuric acid solution is stored as an anode, and the printed wiring board is immersed in a plating bath to be electrified as a cathode. In the dilute sulfuric acid solution, copper plating was formed on the surface of the printed wiring board.

In the above method for producing an anode copper ball for electroplating, by heating the surface of the copper ball to a volatilization temperature of the amount of oil in a heating furnace, the amount of oil can be surely removed, and a high-quality plating anode without contaminating the plating bath can be produced. Copper ball. Further, since the alkaline degreasing agent is not used for the removal of the amount of oil, the environmental load can be greatly reduced, and the equipment cost, the management cost of the degreaser, the processing cost of the waste liquid, and the like can be reduced, and the manufacturing cost can be lowered.

Further, an oxide film is formed on the surface of the copper ball by heating in a heating furnace, but the combustion burner of the heating furnace enriches the fuel to make the inside of the heating furnace a reducing environment, thereby suppressing the formation of an oxide film on the surface of the copper ball. The thickness of the oxide film is made thin. Thereby, the removal of the oxide film generated on the surface of the copper ball can be easily performed.

The oxide film formed on the surface of the copper ball can be easily removed by immersing in a reducing solution such as an aqueous solution of isopropyl alcohol. In the removal of the oxide film, since the acidic agent such as sulfuric acid or hydrochloric acid is not used, the environmental load can be greatly reduced, and the anode for plating can be greatly reduced because the equipment cost, the management cost of the acidic drug, the disposal cost of the waste liquid, and the like are not required. The manufacturing cost of copper balls.

By using the anode copper ball for electroplating obtained by the above-described production method, the amount of oil is not mixed in the plating bath in the printed wiring board as the cathode, and the plating bath is clean to form a very clean plating layer, and sludge or the like is not formed. It can be mixed into the plating bath, etc., and can be plated stably.

Further, in the present embodiment, after the forging step, the amount of oil removed in the heating furnace is described, but it may be pickled or the like before being placed in the heating furnace. At this time, when the amount of oil strongly adhered to the surface of the copper ball is removed by pickling, or when a large amount of oil or the like is adhered, it is heated by the heating furnace, so that the amount of oil can be surely removed. In other words, according to the condition of the oil adhering to the copper ball, pretreatment such as pickling is performed before the heating furnace is installed, and the amount of oil can be surely removed.

Further, although a combustion furnace using a gas burner is used as the heating furnace, the heating method is not limited, and may be an electric furnace. In the case of an electric furnace or the like, since the inside of the furnace is a reducing environment, it is preferable to introduce a gas containing a reducing gas such as carbon monoxide or hydrogen into the furnace from the outside.

Further, although it is explained that a drying step is additionally provided after immersing in the reducing solution, for example, by allowing the temperature of the copper ball itself to be higher than the volatilization temperature of the reducing solution, it can be dried by natural drying.

Example

Hereinafter, the amount of oil remaining on the surface of the anode copper ball for plating produced in the present embodiment is analyzed.

Here, the manufactured anode copper ball for electroplating has a diameter of 55 mm, the gas burner of the heating furnace has an air/fuel ratio of 0.95/1.00 and is burned in a state of rich fuel, and the temperature of the heating furnace is set to about 700 ° C. The copper balls were held in a heating furnace for about 5 minutes.

The copper ball taken out from the heating furnace was immersed in an aqueous solution of 2% isopropanol mixed as a reducing solution for about 30 seconds, dried by a blower, and charged into a roller sander for barrel polishing.

In order to quantify the amount of residual oil on the surface of the anode copper ball for electroplating obtained by this method, the anode copper ball for electroplating is immersed in a specific solution, and analyzed by a Fourier transform infrared spectrophotometer (FTIR) to be incorporated into the solution. The amount of oil. As a result, the amount of oil remaining on the surface of the anode copper ball for plating having a diameter of 55 mm was confirmed to be 0.1 mg/piece or less. Therefore, by using the method for producing an anode copper ball for electroplating of the present invention, it has been confirmed that the amount of oil adhering to the surface of the anode copper ball for plating can be greatly reduced.

Fig. 1 is a flow chart showing a method of producing an anode copper ball for electroplating of the present invention.

Claims (4)

A method for producing an anode copper ball for electroplating, which is used as a raw material for electrolytic plating of copper, characterized by comprising: a forging step of forming a copper material into a spherical shape by cold forging; and a heating step in the heating step by the forging step a heating step of volatilizing the amount of oil adhering to the surface of the copper ball; and a barrel polishing step of polishing the copper ball after the heating step; and a surrounding environment of the furnace of the heating furnace is a reducing gas atmosphere. The method for producing an anode copper ball for electroplating according to the first aspect of the invention, further comprising: an oxide film removing step for removing an oxide film formed on a surface of the copper ball by the heating step. The method for producing an anode copper ball for electroplating according to the second aspect of the invention, wherein the oxide film removing step is a step of immersing the copper ball in a reducing solution, and the method of immersing in the reducing solution Drying step of copper ball drying. The method for producing an anode copper ball for electroplating according to any one of claims 1 to 3, wherein the heating furnace is an electric furnace, and a reducing gas is introduced into the furnace from the outside to make the furnace atmosphere a reducing gas atmosphere. .