JPS586800B2 - Insatsu Kairo Youdou Hakuo Hiyou Menshiyo Risuru Hohou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a treated surface produced when surface treatment of copper foil to give properties suitable for printed circuit use involves electrolytic treatment using an acid bath. The purpose is to equalize the

The term copper foil here encompasses foils made of copper and copper-based alloys.

Printed circuit boards utilizing copper foil have become widely used in the electronics industry.

When using copper foil for printed circuit applications, the copper foil is first adhered to a synthetic resin substrate, the necessary circuits are printed, and unnecessary parts are removed by etching.

Therefore, copper foil used in printed circuit applications has adhesive,
Good properties such as heat resistance, electrical properties, and appearance are required.

With the recent amazing progress in electronic industry technology, the quality requirements for copper foil for printed circuits are becoming increasingly strict.

In many cases, the surface treatment for copper foil printed circuits is
The method is to perform cathodic treatment using an acidic bath using copper foil as a cathode to form a treated surface with excellent adhesion, or to roughen the surface by performing anodization using copper foil as an anode prior to cathodic treatment. A method is used in which the above-mentioned cathode treatment is performed after the oxidation process is completed.

The uniformity of the surface produced in these electrolytic treatments varies greatly depending on the condition of the copper foil surface before the electrolytic treatment.

Generally, copper foil for printed circuits is made based on copper foil produced by rolling or electrolysis.

Especially when the copper foil is a rolled foil, unevenness tends to occur during preliminary treatments such as pickling and degreasing before electrolytic treatment, resulting in uneven surface wettability, making it impossible to obtain a uniform surface after electrolytic treatment. .

Furthermore, even in the case of electrolytic copper foil, if it is once dried and rolled up before electrolytic treatment, a uniform treated surface cannot be obtained due to the difference in the degree of oxidation.

For this reason, in the case of cathodic treatment to improve adhesion, some areas may have poor adhesion, powdery surfaces, uneven coloring, etc.
Further, even in anodization for the purpose of surface roughening, a uniformly roughened surface cannot be obtained.

Various methods have been proposed as countermeasures against these problems.

However, there are still no products that are suitable for industrial use.

The object of the present invention is to provide a surface treatment method which eliminates the above-mentioned drawbacks and which produces a copper foil having an electrolytically treated surface which is uniform in appearance and adhesion after electrolytic treatment, including anodic treatment.

In the present invention, the copper foil to be treated is directly brought into contact with an alkaline aqueous solution containing an oxidizing agent to form a pale brown to black oxide film on its surface, and after being washed with water, it is electrolytically treated in an acidic bath either as is or after drying. This method is characterized by:

In the present invention, the oxide film produced in the pretreatment stage is dissolved in the electrolytic bath, and at the same time, ions are electrodeposited or metals are eluted, and the resulting treated surface has excellent uniformity.

In particular, in the case of cathodic treatment for the purpose of improving adhesion, such as so-called tan plating, which is performed at a high current density around or above the critical current density, the resulting treated surface has a uniform appearance and adhesion, and is free of powder drop-off. Become something.

Oxidizing agents used in the method of the invention include persulfates, permanganates, peroxides, and the like.

As the alkali source, strongly alkaline sources such as caustic soda, caustic potash, and soda carbonate are suitable.

The respective concentrations cannot be unambiguously determined as they depend on the contact time, bath mixture, etc., but may be appropriately selected so that an oxide film is formed over the entire surface of the copper foil within an appropriate time.

It goes without saying that the concentrations of the oxidizing agent and the alkali source vary depending on the specific combination of the oxidizing agent and the alkali source.

For example, when using potassium persulfate as the oxidizing agent and caustic soda as the alkaline agent, the optimum concentration is 10% potassium persulfate.
g/l~20g/l and caustic soda5 g/l~1
0 g/l, and the optimum treatment conditions are bath temperature 40-6
0°C and treatment time 30-100 seconds.

Examples are shown below for further understanding of the present invention.

Example 1 A rolled copper foil with a thickness of 35 μm was immersed for 60 seconds in a 45° C. aqueous solution containing 20 g/l of potassium persulfate and 10 g/l of caustic soda.

Immediately after washing with water, it is described in Japanese Patent Publication No. 40-15327.

A copper foil for printed circuits was obtained by cathodic treatment using an acidic copper electroplating bath containing copper ions at a current higher than the critical current density.

There was no color unevenness on the copper foil surface, and there was no powder falling off.

In addition, in the powder drop test, commercially available cellophane tape was pressed and then peeled off, and then judged based on the amount of particles that adhered to the cellophane tape.

Example 2 Hydrogen peroxide was added to a rolled copper foil with a thickness of 35 μm as an oxidizing agent at 20 μm.
g/l and 10 g/l of caustic soda as an alkali agent.
A copper foil for printed circuits was obtained by carrying out the same treatment as in Example 1 except that an aqueous solution containing the following was used.

There was no color unevenness on the copper foil surface, and no powder was observed to fall off.

Example 3 An electrolytic copper foil having a thickness of 35 μm was subjected to the same treatment as in Example 1 to obtain a copper foil for printed circuits.

There was no color unevenness or powder falling on the copper foil surface, and a satisfactory appearance was exhibited.

Comparative Test For the purpose of confirming the effect of the method of the present invention, electrolytic copper foil and rolled copper foil with a thickness of 35 μm were used for printed circuits directly by the method described in Japanese Patent Publication No. 15327/1972 without any pretreatment according to the present invention. Copper foil was produced.

In the case of electrolytic copper foil, some color unevenness and powder falling were observed.

In addition, in the case of rolled copper foil, color unevenness and powder falling more than electrolytic copper foil were observed.

From this, it was confirmed that the copper foil produced according to the method of the present invention is far superior to the copper foil produced using the conventional method in terms of color unevenness and powder falling.

Performance Comparison Test of Copper Laminated Film It is also important to evaluate the characteristics when the copper foil produced by the method of the present invention is actually adhered to a substrate and etched.

Therefore, a substrate film made of a polyimide film (trade name Capton) coated with an epoxy adhesive was layered on the copper foils obtained in Examples 1 to 3 and the copper foil produced in the comparative test, and then heat-pressed. A steel-clad film for printed circuits was produced.

Peel strength (beer strength) of these five types of copper-clad films
The presence or absence of residue after etching was also investigated.

In the peel test, the maximum and minimum peel strengths over 10 cm were determined by the method specified in JISC-6481 (180° direction).

The results obtained are summarized in Table 1 below.

Copper-plated film production W← Copper foil used after etching Residue Example 1
No 1.55 1.47 u 2 1.50 1.40 No tt 3 1.75 1.70 No comparison test electrolytic foil 1.60 1.30
Some comparison test rolled foil 1.05
0.75 Yes From this table, it can be seen that the copper-clad film using the copper foil made by the method of the present invention exhibits an extremely high level of peel strength and, if present, has no etching effect that would adversely affect the electrical properties of the copper-clad film. It is clear that no residual residue is observed.

Example 4 A rolled copper foil having a thickness of 35 microns was treated according to the method of the invention.

Pretreatment was carried out according to the method of the present invention as shown in Example 1 before electrolytic treatment.

After that, H2SO4 200g/l and CuSO4.5
An anode current density of 4 using an electrolytic bath containing 40 g/l of H2O
Anodizing (
anodic etching).

In addition, for comparison purposes, rolled copper foils of the same thickness were subjected to only the above-mentioned anodic treatment without any preliminary treatment.

The results of comparing the gloss and color unevenness of the copper foil surfaces obtained in both cases are shown in Table 2 below.

Table 2 Treatment according to the present invention Copper foil subjected only to anodization Copper foil color unevenness No Yes (many spot-like unevenness) Gloss Uniform dullness over the entire surface Some parts are glossy with metallic luster
There are many irregularities

Claims (1)

[Claims] 1 A surface treatment method carried out prior to the electrolytic treatment process to impart properties to copper foil as copper foil for printed circuits, in which the surface of the copper foil is treated with persulfate, permanganate, and peroxide. A method for surface treating the copper foil for printed circuits, characterized in that the copper foil for printed circuits is brought into contact with an alkaline aqueous solution containing an oxidizing agent selected from the group consisting of: