KR20050097571A - Method for manufacturing black surface-treated copper foil for emi shield - Google Patents

Abstract

The present invention relates to a method for producing a blackening surface-treated copper foil for electromagnetic wave shielding and a copper foil having a uniform appearance with low reflectance, no uneven appearance and little residue.

The manufacturing method includes the steps of plating in a binary or higher electroplating bath containing Co or Co to form a blackening plating layer containing Co on the surface of the copper foil;

And oxidizing the surface of the blackening plating layer by placing the copper foil as an anode in a basic electrolytic bath and electrolyzing the same.

Since the surface-treated copper foil manufactured by the above method has a black appearance with low reflectance, there is an advantage that the luminance of the PDP display screen is not lowered.

In addition, since the surface-treated copper foil according to the present invention has a black appearance and a uniform appearance with almost no stains and residues on the appearance, the defective rate of the composite material for electromagnetic wave shields manufactured using the same is significantly lowered. In addition, there is an effect that the appearance of the PDP display screen manufactured using the composite material is excellent.

Description

Method for manufacturing black surface-treated copper foil for EMI shield

The present invention relates to a method for producing a blackened surface-treated copper foil for shielding electromagnetic waves and a surface-treated copper foil having a uniform reflectance with low reflectance, no uneven appearance and little residue.

Since the plasma display panel (PDP) radiates powerful electromagnetic waves harmful to the human body from the image display surface, it is necessary to provide electromagnetic shielding to prevent radiation of electromagnetic waves. As the electromagnetic shielding body, a composite material manufactured by laminating a copper circuit on an insulating transparent substrate such as PET is used. The composite material has an advantage of preventing electromagnetic radiation and excellent light transmittance. Specifically, the composite material is manufactured by laminating a copper foil having a predetermined surface roughness on the transparent substrate, and removing unnecessary copper foil by etching to form a desired copper circuit. The line width and pattern of the copper circuit are selected based on the required electromagnetic radiation capability and light transmittance.

However, when the copper circuit reflects external light, there is a problem of lowering the brightness of the display screen. Therefore, as an electromagnetic shielding copper foil, the copper foil which has surface treatment so that it is close to black and has a low reflectance is preferable.

However, the closer the surface of the surface-treated copper foil is to black, the more likely stains are likely to appear on the appearance, or the residue tends to be generated such as powders from the surface. The stain on the surface of the copper foil degrades the quality of the PDP, and the residue is etched and falls on the portion where the transparent substrate is to be exposed, thereby reducing the light transmittance.

For this reason, conventionally, research is mainly performed in the direction which surface-treats so that the surface of copper foil may be made into the chocolate color and dark metal color which are close to black, without making completely black. However, since the surface of the copper foil manufactured by the above method is not completely black, the reflectance improvement as an electromagnetic shielding copper foil had a limit.

An object of the present invention is to provide a blackening surface-treated copper foil for shielding electromagnetic waves having a black appearance and low reflectance, and a method of manufacturing the same.

Moreover, an object of this invention is to provide the blackening surface-treated copper foil for electromagnetic wave shield which has black external appearance, and has a uniform external appearance with few stains and residues, and its manufacturing method.

Further, another object of the present invention is to provide a blackening surface-treated copper foil for shielding electromagnetic waves excellent in peel strength and a method of manufacturing the same.

The manufacturing method of the blackening surface-treated copper foil for electromagnetic wave shield which concerns on this invention to achieve the said objective,

Performing plating in a binary or higher electroplating bath containing Co or Co to form a blackening plating layer containing Co on the surface of the copper foil;

And oxidizing the surface of the blackening plating layer by placing the copper foil as an anode in a basic electrolytic bath and electrolyzing the same.

Before forming the blackening plating layer, it is preferable to further include depositing a fine copper particle layer on the surface of the copper foil.

In addition, it is preferable to further include the step of forming an electrolytic chromate layer on the surface of the oxidized blackening plating layer.

On the other hand, it is preferable to further comprise the step of forming a plated coating layer composed of Zn or Zn alloy on the back surface of the blackened plating layer is formed.

It is preferable that pH of the said basic electrolytic bath is 10 or more.

Hereinafter, the present invention will be described in detail.

Electromagnetic shielding copper foil which is the object of this invention is an electrolytic copper foil which can produce wide width, and thickness of copper foil is 1-35 micrometers, and 6-18 micrometers is preferable. Surface roughness (Rz: DIN) is 0.1-2.0 micrometers, and 0.5-1.5 micrometers are preferable. If the surface roughness is less than 0.1 μm, the adhesion with the transparent base material becomes insufficient, and the reliability of the electromagnetic wave shield decreases. If the surface roughness is larger than 2.0 μm, the surface of the transparent base material on which the copper foil is bonded after forming a circuit by etching is formed. It is not preferable that the unevenness becomes large, thereby increasing the blurring of the display screen.

The main feature of the present invention is that, by oxidizing the black surface-treated copper foil in a basic electrolytic bath, it is possible to obtain a blackened surface-treated copper foil having a uniform appearance in which the copper foil surface is black while no stains or residues are generated.

The blackening process of copper foil is performed by arrange | positioning copper foil to a cathode in the electroplating bath containing the metal which causes black, and depositing the said metal plating layer on the copper foil surface of the said cathode. Metals known to cause black include Cu, Cr, Al, and Co, but Cu may lead to complete black, but there is a problem of damaging the circuit pattern by penetrating into the copper foil circuit when forming the copper foil circuit pattern. Since the problem arises in the etching property at the time of copper foil circuit formation, it is difficult to apply to this invention. In addition, Al cannot be anodized as described later due to its metal properties. Therefore, in consideration of product damage prevention, manufacturing process problems, and anodizing efficiency, Co is the most suitable metal.

Blackening of the Co-coated, for example is made by carrying out plating at a current more than the limiting current density using the Ir electrode as an anode and to the cathode of a copper foil, Co blackening the coating layer formed on the copper foil surface, such as Co ₃ O _4, CoOOH, CoO It is in the form of an oxide.

The concentration of Co included in the electroplating bath may be selected from 1 to 80 g / l, but most efficiently, the concentration of blackening plating layer may be 10 to 30 g / l. The current density of the industrially economical plating bath is 0.1-60 A / dm ² , particularly preferably 5-25 A / dm ² . In addition, the plating time may be in the range of 1 to 20 seconds, but may be out of the range in consideration of the current density, the electrolyte concentration, and the like.

On the other hand, in order to improve the peeling strength of copper foil and to add other characteristics to copper foil, other metal components other than Co can also be included in an electrolytic bath. Ni and Fe are suitable as an element which improves peeling strength, without impairing the characteristic of copper foil. It is preferable from the viewpoint of plating efficiency that the metal component concentration in the electrolyte solution in which the metal component and Co are combined is in the range of 1 to 80 g / l.

The copper foil in which the blackening plating layer was formed is a state in which the plating particle layer precipitated in the shape of a nodule on the surface. By the way, although the surface roughness of the copper foil in which the plated particle layer is formed is generally within the range that can be used as the electromagnetic shielding copper foil, microscopically looking at the surface thereof, the size of the nodule particles deposited on the surface of the copper foil according to the surface conditions or plating conditions of the copper foil, The number is partially different. In addition, hydrogen is generated in the cathode by the precipitation reaction, and the plating thickness of the hydrogen-producing portion shows a slight difference from the thickness of the remaining portion.

For this reason, when the entire copper foil surface is viewed, the portion where the particle size and number of particles are relatively different or the hydrogen-generating sun is different from the surrounding portion appear as spots. In addition, in the case of very fine particles, they fall off the surface during the manufacturing process of the copper foil and become a residue, which degrades the copper foil quality.

In order to solve this problem, the present invention is to arrange a copper foil having a blackening plated layer as an anode in a basic electrolytic bath, to oxidize (corrode) the surface of the blackening plated layer to planarize to a certain extent, thereby reducing the occurrence of stains and residues as much as possible. have.

An advantage of anodizing the black plating layer is that the surface of the black plating layer is corroded evenly while the electrolyte flows in a uniform flow in the front, rear, left and right directions.

The anodic oxidation bath is for basic electrolysis consisting of a basic solution such as NaOH, KOH, etc., and the preferred current density at the time of anodic oxidation can be selected from 1 to 30 A / dm 2 and the time from 1 to 20 seconds. The current density and time may vary depending on the type, composition and temperature of the electrolyte. Anodization is performed by, for example, using stainless steel as a cathode and arranging blackened surface-treated copper foil on the anode.

An important point in the anodic oxidation treatment is the pH adjustment of the basic electrolytic bath. In order to effectively remove stains and residues, the pH of the electrolytic bath should be at least 10, and according to the results of the applicant's experiment, the most preferable result was shown at pH 13.

On the other hand, the fine copper particle layer can be deposited and deposited on the surface of the copper foil before the blackening is performed in order to reduce the reflectance and improve the adhesion with the transparent substrate. Precipitated copper particles act as anchors to increase the peel strength when laminating copper foil on a transparent substrate, and improve adhesion, and diffuse reflection of external light to reduce reflectance.

Formation of a fine copper particle layer can be performed using the roughening process used for the copper foil for printed wiring boards. The roughening treatment is usually carried out in a copper sulfate plating bath, and the copper particle adhesion amount at the time of roughening is preferably in the range of 0.1 to 10 g / m 2. This is because if the above range is lowered (roughness lowering), the reflectance is lowered but the peeling strength (adhesiveness) is lowered.

The surface roughness should be maintained within 0.1 to 2.0 μm in Rz (DIN standard) throughout the three processes of forming the fine copper particle layer, forming the blackened plating layer, and anodizing. The reason is as described above. When surface treatment is performed within the range of the above blackening plating conditions and anodization conditions, the surface roughness can be maintained within the above range.

On the other hand, the copper foil of this invention can be subjected to rust prevention treatment such as electrolytic chromate treatment. In addition, when a plating film made of Zn or Zn alloy is formed on the surface of the non-blackened plating surface, heat discoloration can be prevented in the heating step for producing the electromagnetic wave shield.

Hereinafter, the present invention will be described in detail through examples. However, the following examples are only for illustrating the present invention, and it will be apparent to those skilled in the art that the scope of the present invention is not limited to the following examples according to the gist of the present invention.

Example

Example 1:

An electrolytic copper foil having a surface roughness (Rz) of 2 μm or less and a thickness of 10 μm was immersed in 100 g / l sulfuric acid for 5 seconds, washed with pure water after pickling, and then subjected to blackening and anodizing under the following conditions. Was done.

Blackening plating treatment conditions; Co metal ion concentration of electrolytic bath 18 g / l (Co is added to the plating bath in the form of cobalt sulfate), buffer (H ₃ BO ₃ ) concentration 30 g / l, pH 3.5, electrolyte temperature 30 ℃, current density 20 A / dm ² , plating time 4 seconds.

Anodizing conditions; PH of NaOH anodic oxidation bath: 13, anodic oxidation bath temperature: 70 ℃, current density: 15 A / dm ² , oxidation time: 4 seconds.

Example 2:

The fine copper particle layer was formed with the copper adhesion amount as 1.5 g / m <2>, and blackening plating process and anodizing process were performed on the conditions similar to Example 1.

Example 3:

After the surface of the copper foil was pretreated under the same conditions as in Example 1, blackening plating treatment and anodizing treatment were performed under the following conditions.

Blackening plating treatment conditions; Co metal ion concentration 10 g / l, Ni metal ion concentration 8 g / l, (Ni is added to the plating bath in the form of nickel sulfate), buffer (H ₃ BO ₃ ) concentration 30 g / l, pH 3.5, electrolyte Temperature 30 ℃, current density 20 A / dm ² , plating time 4 seconds.

Anodizing conditions; PH 13 of the NaOH anodic oxidation bath, anodic oxidation bath temperature 70 ℃, current density 15 A / dm ² , oxidation time 4 seconds.

Example 4:

After the fine copper particle layer was formed under the same conditions as in Example 2, blackening plating treatment and anodizing treatment were performed under the same conditions as in Example 3.

Example 5:

After the surface of the copper foil was pretreated under the same conditions as in Example 1, blackening plating treatment and anodizing treatment were performed under the following conditions.

Blackening plating treatment conditions; Co metal ion concentration 10 g / l, Fe metal ion concentration 5 g / l (Fe is added to the plating bath in the form of iron sulfate), buffer (H ₃ BO ₃ ) concentration 30 g / l, pH 3.5, electrolyte Temperature 30 ℃, current density 20 A / dm ² , plating time 4 seconds.

Anodizing conditions; PH of NaOH anodic oxidation bath, anodic oxidation bath temperature 70 ℃, current density 15 A / dm ² , oxidation time 4 seconds.

Example 6:

After the fine copper particle layer was formed under the same conditions as in Example 2, blackening plating treatment and anodizing treatment were performed under the same conditions as in Example 5.

Comparative example

After pretreatment of the surface of the electrolytic copper foil under the same conditions as in the above example, blackening treatment plating was performed under the following conditions.

Co metal ion concentration 20 g / l, pH 3.5, electrolyte temperature 30 deg. C, current density 20 A / dm ² , plating time 4 seconds.

The following table shows the results of measuring the occurrence of staining of the surface-treated copper foil according to the Examples and Comparative Examples, the occurrence of residue (separation) by rubbing, and the peel strength.

[table]

Color stain Rubble Peel Strength (kg _f / ㎝) Comparative example black △ ○ 0.68 1 to implementation black ▲ ● 0.30 Example 2 black ▲ ● 0.60 Example 3 black ▲ ● 0.39 Example 4 black ▲ ● 0.62 Example 5 black ▲ ● 0.36 Example 6 black ▲ ● 0.58

Degree of dirt: △ little presence, ▲ no

Residue (separation due to rubbing) degree: ○ Trace amount, ● None

As shown in the table, in the comparative example which only performed the blackening plating process, the stain and the residue generate | occur | produce on the surface. However, it can be seen that the embodiment of the present invention subjected to the anodizing treatment after the blackening plating treatment does not generate stains and residues.

In addition, Examples 2, 4, and 6, in which the fine copper particle layer was formed before the blackening plating process, showed that the peeling strength was increased as compared with Examples 1, 3, and 5 in the corresponding conditions in which the fine copper particle layer was not formed. have. In addition, it can be seen that Example 3 and Example 5, in which Ni and Fe are additionally included in the blackened plating layer, have a higher peeling strength than Example 1, in which the above components are not included.

When the electromagnetic shielding body is manufactured from a composite material prepared by laminating the surface-treated copper foil of the present invention having the uniform appearance as described above on an insulating transparent substrate such as PET, a plasma display panel having excellent display screen resolution can be manufactured. As a result, the failure rate can be significantly lowered.

As described above, the surface-treated copper foil manufactured by the manufacturing method of the present invention has a black appearance with low reflectance, and thus has the advantage of not lowering the luminance of the PDP display screen.

In addition, since the surface-treated copper foil according to the present invention has a black appearance and has a uniform appearance with little stains and residues, the defective rate of the composite material for electromagnetic wave shields manufactured using the same is significantly lowered. There is an effect that the appearance of the PDP display screen manufactured using the composite material becomes excellent.

Claims (7)

Plating in a binary or higher electroplating bath containing Co or Co to form a blackening plating layer containing Co on the surface of the copper foil; Oxidizing the surface of the blackening plating layer by disposing the copper foil as an anode in a basic electrolytic bath, and electrolyzing the manufacturing method of the blackening surface-treated copper foil for electromagnetic shielding. The method of claim 1, Before forming the blackening plating layer, a method of manufacturing a blackening surface-treated copper foil for electromagnetic shielding, further comprising the step of depositing a fine copper particle layer on the surface of the copper foil. The method of claim 1, And forming an electrolytic chromate layer on the surface of the oxidized blackening plating layer. The method of claim 1, A method of manufacturing a blackening surface treated copper foil for electromagnetic wave shielding, further comprising the step of forming a plated coating layer composed of Zn or Zn alloy on the back surface of the blackened plating layer. The method of claim 1, PH of the said basic electrolytic bath is 10 or more, The manufacturing method of the blackening surface-treated copper foil for electromagnetic shielding characterized by the above-mentioned. The blackening surface-treated copper foil for electromagnetic wave shields manufactured by the method of Claims 1-5. A composite material for electromagnetic shielding, wherein the blackening surface-treated copper foil of claim 6 is laminated on an insulating transparent substrate.