JPS599639B2 - Oxidation treatment method for copper or copper alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oxidation treatment method for copper or copper alloy, and more specifically, for forming a dense copper oxide film with excellent electrical insulation and good adhesion on the surface of copper or copper alloy. The present invention relates to a method for anodizing copper or copper alloys.

It has been known to form a copper oxide film on the surface of copper or copper alloys by various methods.

For example, (a) a method of anodizing copper or a copper alloy in a high-temperature alkaline solution, such as a method of anodizing copper or a copper alloy in a sodium hydroxide electrolyte at 80° C. or higher, or (b) a method of anodizing a copper or a copper alloy with chlorine chloride. Methods of immersion in chemical chemicals, such as a method of oxidizing at a high temperature of about 100° C. by immersing it in an alkaline solution such as sodium hydroxide or potassium hydroxide in the presence of an oxidizing agent such as sodium hydroxide, have been proposed.

However, among these methods, (a) anodizing treatment in a high-temperature alkaline solution causes the oxidation reaction to take place at a high temperature, so it is necessary to make the reaction equipment corrosion-resistant, or the heating The equipment required is expensive, and the voltage needs to be controlled to maintain an effective current density.
There are many national problems, and in practice, so-called chemical conversion coatings, which can be oxidized by simply immersing them in a chemical chemical solution as described in (b) above, are more commonly used. The present inventors have already developed insulation properties on the surface of copper or copper alloy by immersing copper or copper alloy in an aqueous solution containing hydrogen peroxide and nitric acid or sulfuric acid.
Method for forming a copper oxide film that is sufficiently practical in terms of flexibility and adhesion (Japanese Patent Application No. 1982-129782, Japanese Patent Application No. 54-146179, Japanese Patent Application No. 55-121570)
has been proposed.

In contrast, the present inventors have proposed a simple immersion method according to the patent application previously proposed by the present inventors by anodizing copper or copper alloy in a mixed aqueous solution of hydrogen peroxide and sulfuric acid. It was discovered that an excellent copper oxide film could be obtained that could not be obtained by using the method alone, and furthermore, a copper oxide film with excellent properties that could not be obtained by the conventional anodizing treatment method in a high-temperature alkaline aqueous solution could be obtained. The heading completes the invention.

The feature of the oxidation treatment method of the present invention is that copper or copper alloy is heated in a mixed aqueous solution of hydrogen peroxide and sulfuric acid in order to form a copper oxide film with excellent electrical insulation and adhesion on the surface of copper or copper alloy. It is anodized.

The present invention will be explained in more detail below.

The copper or copper alloy used in the present invention is first subjected to pretreatment such as degreasing and descaling.

Next, the pretreated copper or copper alloy is immersed in a mixed aqueous solution of hydrogen peroxide and sulfuric acid to be oxidized. The chemical reaction of copper or copper alloy in this mixed aqueous solution is considered as follows. When the object to be treated is placed in the treatment solution, the hydrogen peroxide in the mixed aqueous solution immediately attacks the pretreated copper surface and an oxidation reaction takes place (primary acid 0).

Subsequently, the etching action with sulfuric acid proceeds, revealing a clean and active copper surface. These reactions can be called activation reactions and passivation prevention reactions that activate the copper surface and allow subsequent reactions to proceed smoothly. This reaction can be expressed as a reaction formula as follows. Subsequently, a secondary oxidation reaction occurs.

A chemical oxidation reaction using active oxygen generated from hydrogen peroxide on the copper surface activated as described above, and an electrochemical oxidation reaction of hydroxide ions due to the dissociation of water based on the properties of sulfuric acid using sulfuric acid as an electrolyte. occur in duplicate. In this case, as well as the above chemical oxidation reaction,
The copper compound produced by the electrochemical oxidation reaction also forms a film on the copper surface as stable copper oxide. This film is dense and has excellent electrical insulation properties. In other words, the reason why this film is dense and has excellent electrical insulation properties is that while copper oxide is formed to some extent in a porous form through the chemical oxidation reaction of hydrogen peroxide, the electrochemical reaction caused by the electrolysis of sulfuric acid Copper compounds, such as cupric hydroxide, are generated and filled in the pores of the copper oxide as a highly sticky substance, and are then converted to copper oxide, so both reactions occur. This is because copper oxide is thought to be produced in a dense and thick manner. In this case, it is thought that the chemical oxidation reaction caused by hydrogen peroxide exquisitely prevents the anodic dissolution of copper by sulfuric acid, and conversely serves to smoothly guide the anodic oxidation caused by the electrochemical oxidation reaction. It will be done. This reaction can be expressed as a reaction formula as follows. When we actually observed the oxide film after the anodic oxidation treatment as described above, it was observed that the oxide film was composed of a uniform component consisting of cupric oxide (CuO), and the chemical It can be seen that both electrochemical reactions have a superimposed effect on the formation of cupric oxide. Further, the elution of copper from the anode side was within several hundred centimeters per hour x 1 volt. Next, the solution composition and anodic oxidation conditions will be explained.

The concentration of hydrogen peroxide in the mixed aqueous solution is 5 to 50v01q6
is preferred. If it is less than 5v01q6, the primary oxidation reaction shown by the above reaction formula (1) for activation is difficult to occur,
Since the subsequent secondary oxidation capacity shown in reaction equation (3) is also small, no oxide film is formed by chemical oxidation reaction, and electrolysis based on the action of sulfuric acid as an electrolyte occurs preferentially, resulting in copper Elution increases, making it difficult to form an oxide film.

On the other hand, if it exceeds 50v01(f), the hydrogen peroxide itself will undergo rapid natural decomposition and will be wasted, making it impractical, and the efficiency of electrolysis of sulfuric acid will also decrease. Next, the concentration of sulfuric acid is preferably 0.5 to 6.0%.

If it is less than 0.5v01q6, the attack of hydrogen ions on the copper surface is insufficient, and the etching action for activation shown in the above reaction formula (2) and the reaction formula (4) as one of the secondary oxidation reactions occur. ) is no longer capable of anodic oxidation by electrolysis, which is electrochemical oxidation, and a sufficient copper oxide film cannot be produced.

On the other hand, if it exceeds 6v01%, the etching reaction will always take priority and the effect of anodic oxidation will no longer exist, and conversely, anodic dissolution will become more intense. Incidentally, the cathode during anodization may be made of stainless steel, aluminum plate, or lead plate.

Next, regarding the electrolytic voltage during anodic oxidation, it is preferable to process at a constant voltage, usually several volts, preferably 5 to 7 volts (however, hydrogen peroxide concentration is 35v01%, sulfuric acid concentration is 1 to 1%).
3V01q1) seems to be optimal.

Moreover, the bath temperature is preferably 5 to 40°C. If it is below 5℃, chemical oxidation reaction will not occur and effective film formation will not occur.On the other hand, if it exceeds 40℃, natural decomposition of hydrogen peroxide will become significant and the efficiency of film formation will deteriorate. .

In addition, in proceeding with the series of reactions of the present invention, the activation reactions shown in the above-mentioned reaction formulas (1) and (2), and the reaction formulas (3), (4), and (5) For example, as shown in FIG. 1, the electrolytic cell 1 is separated by a liquid-permeable diaphragm 2 (e.g., polyethylene, vinyl chloride, etc.) to separate the first reaction chamber 3 and the second reaction chamber 3 so that the oxide film forming reaction shown in FIG. A wire rod 5 made of copper or copper alloy, which is transferred from the first reaction chamber 3 to the second reaction chamber 4, is energized by a roll electrode 6 to serve as an anode, and a plate is placed in the second reaction chamber 4. An anodic oxidation treatment apparatus may be used in which a shaped electrode 7 is provided and used as a cathode.

By feeding the wire 5 and the like into the first reaction chamber 3 and taking it out from the second reaction chamber 4, first, in the first reaction chamber 3, a primary oxidation reaction mainly using hydrogen peroxide and an etching action using sulfuric acid occur, and the diaphragm 2, in the second reaction chamber 4,
Secondary oxidation is performed between the copper or copper alloy material that is the anode and the cathode. By classifying in this way, it becomes possible to more optimally set the reaction conditions for each reaction.
For example, regarding the concentration of hydrogen peroxide and sulfuric acid, the first reaction chamber 3
In the second reaction chamber 4, the temperature may be kept relatively low, and in the second reaction chamber 4, it may be kept relatively high. As described above, the copper oxide film of copper or copper alloy that has been oxidized according to the present invention is dense and exhibits excellent electrical insulation and adhesion. They can be used as electrical insulating materials, including those with complex shapes.

Especially in the case of wire rods, 120 to 120 per μm of copper oxide film thickness
It exhibits a dielectric breakdown voltage of 150 volts, and if coated with a suitable resin such as acrylic resin, it can be used as it is as a magnet wire. In addition, since the copper oxide film has corrosion resistance, the copper or copper alloy treated according to the present invention can be used in various applications where corrosion resistance is required, such as in corrosive atmospheres handling chemicals and oxidation at temperatures of 300 to 400°C. It can be used as a magnet wire used in high temperature atmospheres.
In addition, the processing method of the present invention can also be used for the development of electronic materials. <Example> After thoroughly degreasing a 20φ copper wire with Triclean, 35v01
(f) Hydrogen peroxide (industrial use, manufactured by Nippon Peroxide Co., Ltd.)
Add sulfuric acid to 0.5, L2, 3.4, 5, 6, 7, 8.10
Make an aqueous solution with v01% added, L2.3.4, at room temperature.
5.6.7, 8.9, lO. l2. l4. A constant voltage of 16 volts was applied, and anodization was performed for 0.5, 1.2, and 3.4.5 minutes, respectively.

After this treatment, the electrical breakdown voltage of one layer (approximately 0.3 to 1.2 μm) of the oxide film was measured on the sample after washing and drying. The results shown in Figure 4 were obtained. Note that a stainless steel plate was used as the cathode. In addition, in the case of dielectric breakdown voltage due to changes in sulfuric acid concentration shown in Figure 1, please refer to 35v0101) Copper oxide film formed when immersed for 10 minutes in a mixed aqueous solution of hydrogen peroxide and sulfuric acid at various concentrations. Also added the dielectric breakdown voltage value. In each figure, the measured values of the dielectric breakdown voltage were set to n=3, the upper and lower limits thereof are shown by vertical arrows, and the average value is shown by a black circle or a white circle.

According to each of the above figures, first of all, as shown in Fig. 2, the dielectric breakdown voltage of the copper oxide film of the present invention is considerably higher than that of the one simply immersed, and when the sulfuric acid concentration is set to the optimum value,
It can be seen that the voltage reaches ~150 volts.

Further, from FIG. 3, it can be seen that the voltage between electrodes is about 4 to 7 volts, and a high dielectric breakdown voltage can be obtained. Moreover, it can be seen from FIG. 4 that the most preferable anodic oxidation time is about 0.5 to 2 minutes. In addition, an aqueous solution was prepared by adding sulfuric acid to 35 (fl) hydrogen peroxide solution at 0.0.5, 3, 6, 10v0.11 (I), and a 2.0φ copper wire was immersed in this solution, and the voltage between electrodes was were set to 1, 5, and 8.12V, and the electrolysis time was set to 0.
5. Regarding the samples anodized for 1, 2, and 5 minutes, the surface condition of the wire rod after self-diameter winding was wiped with powder and observed from the occurrence of cracks, etc. The results are shown in the following table.

According to this table, it can be seen that there are appropriate bath compositions and anodizing conditions in terms of not only electrical properties but also appearance and adhesion. As explained above, the oxidation treatment method for copper or copper alloy of the present invention is to oxidize copper or copper alloy to 5 to 50v01 of hydrogen peroxide.
Because it is anodized in a mixed aqueous solution containing q11 trigrams and sulfuric acid 0.5 to 6.0v01(f), it has a dense and adhesive coating with much higher dielectric breakdown voltage than copper oxide coatings made by conventional methods. can produce an excellent oxide film.

Moreover, since the oxidation treatment can be performed in a very short time and at a treatment temperature near room temperature, the manufacturing cost is also low. Furthermore, the fact that the treatment temperature can be low has the advantage that corrosion of the reactor can be reduced. Further, by performing constant voltage processing, there are also advantages such as ease of voltage control operation.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the outline of a useful processing apparatus applying the method of the present invention, and Figs. 2 to 4 show the dielectric breakdown voltage, sulfuric acid concentration, anode FIG. 2 is a graph diagram showing the relationship between oxidizing electrode voltage and anodic oxidation time.

Claims (1)

[Claims] 1. Copper or copper alloy which is characterized by anodizing copper or copper alloy in a mixed aqueous solution containing 5 to 50 vol% hydrogen peroxide and 0.5 to 6.0 vol% sulfuric acid to form a copper oxide film. Oxidation treatment method.