JP2016204706A - Electrolytic copper foil for printed wiring board and copper-clad laminate using electrolytic copper foil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic copper foil having high elongation and folding resistance after a heat treatment and less in abnormal projection in a rough surface side and capable of being used suitably for a flexible printed wiring board less in HAZE value when making a copper-clad laminate.SOLUTION: There is provided an electrolytic copper foil for printed wiring board having a glossy surface of an electrolytic copper foil manufactured by continuously deposing onto a drum rotation cathode surface as a contacting surface with an insulation resin substrate, where a specular glossiness with incident angle of 60° in a TD direction of the glossy surface is 220 or less and sum of specular glossiness with incident angle of 60° in the TD direction and a MD direction of the glossy surface is 350 or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrolytic copper foil used for a printed wiring board, and particularly to an electrolytic copper foil that can be suitably used for a flexible printed wiring board.

  In recent years, electronic devices have become smaller, lighter, and more advanced, and in order to respond to these, flexible printed wiring boards that can be placed in slight gaps in the electronic device and three-dimensionally placed are widely used. The density of electronic components on flexible printed wiring boards is also increasing.

One method for mounting electronic components on a flexible printed wiring board at a high density is a method using an anisotropic conductive film. This is a method of obtaining conduction in the vertical direction by sandwiching an anisotropic conductive film between a printed circuit board and a flexible printed wiring board, and press-bonding it by a method of heating and pressing.
In order to obtain continuity between the upper and lower sides, the printed circuit board and the printed wiring board need to be accurately aligned. Therefore, positioning marks are marked on each of the printed circuit board and the flexible printed wiring board. Align while recognizing with CCD camera.

Since the alignment using the CCD camera is performed by photographing from the back side of the circuit, the transparency of the exposed insulating resin base material (hereinafter referred to as “resin base material”) after the copper foil is etched away is low, If it is cloudy, the mark cannot be recognized and accurate positioning cannot be performed.
Therefore, it is said that the haze of the exposed resin substrate (hereinafter referred to as “HAZE” value) should be as low as possible, and it is said that the HAZE value of 80% or less is necessary for accurate alignment. Yes.

  The HAZE value is affected by the uneven shape of the resin substrate surface. If the uneven shape on the surface is large, the reflected light is scattered and the transparency is lowered, so the HAZE value becomes high.

  Since the uneven shape on the surface of the resin base is a replica of the adhesive surface of the copper foil with the resin base as it is, if the uneven shape of the adhesive surface of the copper foil is large, the uneven shape on the surface of the resin base that is a replica Becomes larger and the HAZE value becomes higher. Therefore, in order to lower the HAZE value, it is necessary to reduce the roughness of the copper foil bonding surface and reduce the uneven shape. In addition, since the specular gloss increases when the uneven shape is small, increasing the specular gloss also causes a decrease in the HAZE value.

  The electrolytic copper foil using the drum-shaped rotating cathode has a surface (hereinafter referred to as “glossy surface”) and an electrodeposition end surface (hereinafter referred to as “rough surface”) on the peripheral surface of the drum-shaped rotating cathode. Are different in shape.

Either the rough surface or the glossy surface can be used as an adhesive surface with the resin base material. However, when the rough surface is used, it is necessary to reduce the roughness in order to reduce the HAZE value.
Further, when using either a rough surface or a glossy surface, it is necessary to increase the specular glossiness.

  In an electrolytic copper foil manufactured using a drum-shaped rotating cathode, in order to reduce the roughness of the rough surface or increase the specular gloss, the electrolyte contains various water-soluble polymer substances, various surfactants, Often, additives such as organic sulfur compounds are appropriately selected and added.

  However, the use of various organic ionic compounds that are indispensable as additives for lowering the roughness and increasing the specular gloss and the nitrogen-containing compounds called levelers, the flexibility and folding resistance of the electrolytic copper foil Is known to fall. Therefore, when an additive is added to reduce the HAZE value, there is a possibility that flexibility and folding resistance for use in a flexible printed wiring board cannot be secured.

  In an electrolytic copper foil manufactured using a drum-shaped rotating cathode, if the glossy surface is used as the adhesive surface of the resin base material, the drum-shaped rotating cathode can be used without adding additives that affect flexibility and folding resistance. By polishing the surface, the roughness of the glossy surface can be lowered and the specular glossiness can be increased.

  However, the polishing streaks on the surface of the drum-shaped rotating cathode are the starting point for the generation of copper nuclei during electrolysis, so if the polishing streak is made fine enough, copper nuclei will not be generated and abnormal precipitation on the rough surface side will occur. (Hereinafter referred to as “abnormal protrusion”) frequently occurs.

  If there are many abnormal projections on the rough surface side, it will be scratched when winding the electrolytic copper foil, causing surface defects and various surface treatment processes that give roughening treatment, heat resistance, chemical resistance and rust prevention power However, there is a problem that the running performance of the machine is deteriorated.

  In addition, when the flexible printed wiring board is formed, there arises a problem that air bubbles are caught between the coverlay attached for protecting the surface of the flexible printed wiring board.

  Therefore, the adhesive surface with the resin base material has low roughness, high specular gloss, flexibility, folding resistance, few abnormal projections on the rough surface side, excellent appearance and work efficiency, copper In the case of a tension laminate, it is desired to develop an electrolytic copper foil that can be suitably used for a flexible printed wiring board having a low HAZE value of an exposed resin base material after etching.

JP 2008-118163 A

  Patent Document 1 discloses a flexible printed wiring board in which an adhesive surface with an insulating layer is a glossy surface, a specular glossiness at an incident angle of 60 ° of the glossy surface is 250 or more, and a light transmittance of the exposed insulating layer is high. The electrolytic copper foil used for is disclosed.

  However, the electrolytic copper foil disclosed in Patent Document 1 is deposited using a drum-like rotating cathode that is polished so as not to generate polishing streaks as much as possible in order to avoid a decrease in the specular gloss of the glossy surface. Therefore, there is a problem that copper nucleation is insufficient during electrolysis and a large number of abnormal protrusions are generated on the rough surface side.

  The present inventors made it a technical subject to solve the above-mentioned problems, and as a result of many trial and error trial manufactures and experiments, using a drum-shaped rotating cathode, the glossy surface of the drum width direction The specular gloss at an incident angle of 60 ° (hereinafter referred to as `` TD direction '') is 220 or less, and the TD direction of the glossy surface and the longitudinal direction along the drum circumferential surface (hereinafter referred to as `` MD direction '') If the electrolytic copper foil with a specular gloss at an incident angle of 60 ° is 350 or more, it is a glossy surface with a low roughness and a high specular gloss without the addition of additives. Accomplished the above technical problem by obtaining remarkable knowledge that electrolytic copper foil with very few protrusions and copper-clad laminate reduces the HAZE value of the exposed resin base material after etching removal It is a thing.

  The technical problem can be solved by the present invention as follows.

  The present invention is an electrolytic copper foil for a printed wiring board in which a glossy surface of an electrolytic copper foil produced by continuously depositing on the surface of a drum-shaped rotating cathode is an adhesive surface with an insulating resin substrate, For printed wiring boards whose specular gloss at an incident angle of 60 ° in the TD direction of the surface is 220 or less and the sum of the specular gloss at the incident angle of 60 ° in the TD direction and MD direction of the gloss surface is 350 or more Electrolytic copper foil (Claim 1).

Moreover, this invention is the electrolytic copper foil for printed wiring boards of Claim 1 whose surface roughness Rz _JIS94 of the said electrolytic copper foil glossy surface is 1.5 _micrometers or less (Claim 2).

  Moreover, this invention is the process copper foil which provided the 1 or 2 or more process layer in the electrolytic copper foil glossy surface for printed wiring boards of Claim 1 or 2. (Claim 3).

  Moreover, this invention is the copper clad laminated board which bonded the copper foil of any one of Claims 1 thru | or 3 to the insulating resin base material (Claim 4).

  Moreover, this invention is a copper clad laminated board of Claim 4 whose HAZE value is 80% or less (Claim 5).

  Moreover, this invention is a printed wiring board formed using the copper clad laminated board of Claim 4 or 5. (Claim 6).

  According to the present invention, using a drum-shaped rotating cathode polished to a low roughness, the specular gloss at an incident angle of 60 ° in the TD direction on the glossy surface side of the electrolytic copper foil is 220 or less, and the TD direction and the MD direction Since the sum of the specular gloss at an incident angle of 60 ° is 350 or more, it is possible to suppress the occurrence of abnormal protrusions on the rough surface side, and to suppress scabs that occur during winding of the deposited copper foil, resulting in excellent appearance. In the case of a copper-clad laminate, the HAZE value is 80% or less.

  In addition, an electrolytic copper foil having a glossy surface with a low roughness and a high specular gloss can be obtained without using an additive that affects the flexibility and folding resistance of the electrolyte. It becomes an electrolytic copper foil which can maintain a folding ratio as high and can be used suitably for a flexible printed wiring board.

  In addition, since there are very few abnormal projections on the rough surface side, the machine is easy to run in various surface treatment processes, and it is difficult for air bubbles to enter when pasting with a protective sheet, etc. It becomes copper foil.

It is the figure which showed the abnormal protrusion 3 micrometers or more of the rough surface side of the Example and comparative example of this invention.

  The electrolytic copper foil in the present invention is produced by a method in which a drum-shaped rotating cathode is immersed in a sulfuric acid-copper sulfate aqueous solution, copper is deposited on the drum-shaped rotating cathode using an insoluble anode, and continuously peeled off and wound up. .

  The drum-shaped rotating cathode is not particularly limited, but a titanium drum-shaped rotating cathode can be suitably used.

  For polishing the drum-shaped rotating cathode, it is preferable to use a cylindrical polishing buff obtained by uniformly bonding and impregnating abrasive grains such as aluminum oxide and silicon carbide to a nylon nonwoven fabric.

  As the cylindrical polishing buff, No. 1200 and No. 1500 (manufactured by Kleitoshi Co., Ltd.) can be suitably used.

  Polishing is performed by rotating the cylindrical polishing buff while rotating the rotating cathode, so that the drum-shaped rotating cathode has a desired roughness.

  To achieve a specular gloss at an incident angle of 60 ° of 220 or less in the TD direction and a sum of 350 or more in the TD direction and the MD direction, the rotational speed of the rotating cathode is 60 to 200 mm / sec. The rotational speed is preferably 250 to 600 times / min., And the amplitude is preferably 20 to 25 mm.

In the present invention, since the roughness of the surface of the drum-shaped rotating cathode becomes the roughness of the adhesive surface of the electrolytic copper foil with the resin base material, the roughness Rz _JIS94 of the drum-shaped rotating cathode is preferably 1.5 μm or less. More preferably, it is 1.3 μm or less.
_This is because if the Rz _{JIS94 of the} electrolytic copper foil is larger than 1.5 μm, the HAZE value of the resin base material exposed by etching may exceed 80%.

As electrolysis conditions, a current density of 30 to 60 A / dm ² and a liquid temperature of 35 to 45 ° C. are suitable.

  The insoluble anode is not particularly limited, but a titanium plate coated with a platinum group element or an oxide element thereof can be suitably used.

  Any additive that does not lower the elongation and folding resistance of the electrolytic copper foil after heat treatment can be added to the electrolytic solution, and examples of the additive that can be added include chlorine and water-soluble polymers.

  The thickness of the electrolytic copper foil is preferably 9 μm to 18 μm. If it is thicker than 18 μm, it cannot be used for a flexible printed board.

  In the electrolytic copper foil in the present invention, various treatment layers can be provided as necessary within a range that does not affect the HAZE value when a copper clad laminate is produced.

  Examples of the present invention are shown below, but the present invention is not limited thereto.

<Example 1>
Using a cylindrical rotating buff of No. 1500 (made by Kretoishi Co., Ltd.) with titanium carbide abrasive grains using a titanium drum-like rotating cathode, the surface roughness Rz _{JIS94 of the} cathode is 1.5 μm or less. The polishing finish was as follows.
Thereafter, an electrolytic copper foil having a thickness of 12 μm was produced under the conditions shown in Table 1.

<Examples 2 and 3>
The drum-shaped rotating cathode made of titanium was polished and finished so that the surface roughness Rz _{JIS94 of the} cathode became 1.5 μm or less using a cylindrical polishing buff No. 1200 using silicon carbide as abrasive grains.
Thereafter, an electrolytic copper foil having a thickness of 12 μm was produced under the conditions shown in Table 1.

<Comparative Example 1>
The drum-shaped rotating cathode made of titanium was polished and finished so that the surface roughness Rz _{JIS94 of the} cathode was 1.5 μm or less using a No. 2000 cylindrical polishing buff using silicon carbide as abrasive grains.
Thereafter, an electrolytic copper foil having a thickness of 12 μm was produced under the conditions shown in Table 1.

<Comparative example 2>
The titanium drum-shaped rotating cathode is buffed using a No. 1200 cylindrical polishing buff with silicon carbide as abrasive grains, and further polished using a No. 2000 sheet-like polishing pad, and the surface of the cathode The _surface was polished so that the roughness Rz _JIS94 was 1.5 μm or less.
Thereafter, an electrolytic copper foil having a thickness of 12 μm was produced under the conditions shown in Table 1.

<Comparative Example 3>
The drum-shaped rotating cathode made of titanium was polished and finished so that the surface roughness Rz _{JIS94 of the} cathode was 1.5 μm or less using a number 1000 cylindrical polishing buff using silicon carbide as abrasive grains.
Thereafter, an electrolytic copper foil having a thickness of 12 μm was produced under the conditions shown in Table 1.

<Comparative example 4>
The titanium drum-shaped rotating cathode was polished and finished using a No. 1500 cylindrical polishing buff with silicon carbide as abrasive grains so that the surface roughness Rz _{JIS94 of the} cathode was larger than 1.5 μm.
Thereafter, an electrolytic copper foil having a thickness of 12 μm was produced under the conditions shown in Table 1.

<Comparative Example 5>
Using the titanium drum-shaped rotating cathode used in Comparative Example 4, copper sulfate pentahydrate 280 g / L, sulfuric acid 80 g / L electrolyte, polyethylene glycol (molecular weight 20,000) 20 mg / L, polyethyleneimine derivative (trade name) : Epomin <registered trademark> PP-061: Weight average molecular weight 1200: Nippon Shokubai Co., Ltd.) 20.0 mg / L, sodium 3-mercapto-1-propanesulfonate 6.0 μmol / L, chloride ion 20 mg / L, Electrolysis was performed at a current density of 40 A / dm ² and a liquid temperature of 40 ° C. to produce an electrolytic copper foil having a thickness of 12 μm.

  Each manufactured electrolytic copper foil was measured by the following method.

[Roughness]
Based on JISB0601, the surface roughness Rz _JIS94 of the glossy surface of each electrolytic copper foil obtained in Examples 1 to 3 and Comparative Examples 1 to 4 and the rough surface of the electrolytic copper foil obtained in Comparative Example 5 is surf coder SE1700α ( Measured using Kosaka Laboratory).

[Specular gloss]
Based on JISZ8741, the glossiness of the glossy surface of each electrolytic copper foil obtained in Examples 1 to 3 and Comparative Examples 1 to 4 and the rough surface of the electrolytic copper foil obtained in Comparative Example 5 was measured using a gloss meter GM-268 ( Specular Glossiness (Gs (60 °)) at an incident angle of 60 ° was measured in two directions of TD direction and MD direction.

[Elongation after heat treatment]
After holding each electrolytic copper foil obtained in Examples 1 to 3 and Comparative Examples 1 to 5 at 200 degrees for 10 minutes, the elongation at 25 ° C. was measured based on IPC-TM-650. Measured by a company Intesco).

[Number of folds]
A test piece having a width of 1/2 inch and a length of 2 cm was cut out from each of the electrolytic copper foils obtained in Examples 1 to 3 and Comparative Examples 1 to 5 and held at 200 ° C. for 10 minutes. Fold it in half so that it is perpendicular to the length direction, place a load of 2 kg on the folded part and hold it for 10 seconds, open the folded test piece, place the load on it and stretch it flat, then fold it again and test The number of times until the piece completely broke was measured.

[HAZE value]
Each electrolytic copper foil obtained in Examples 1 to 3 and Comparative Examples 1 to 5 was used as a cathode, a copper plate as an anode, and copper sulfate pentahydrate 40 g / L and ethylenediaminetetraacetic acid tetrasodium 100 g / L electrolyte solution were adjusted to pH. After the preparation to 5.5, a roughening treatment was performed under electrolytic conditions of a liquid temperature of 35 ° C., a current density of 2 A / dm ² , and 25 seconds.
The roughening treatment was performed on the glossy surface side in Examples 1 to 3 and Comparative Examples 1 to 4, and on the rough surface side in Comparative Example 5.

After the roughening treatment, it was washed with water for 5 seconds. Next, an electrolytic solution of sodium dichromate dihydrate 10 g / L was prepared at pH 4.5 using the electrolytic copper foil as a cathode and platinum as an anode, and the solution temperature was 32 ° C. and the current density was 0.5 A / dm ² for 2 seconds. Electrolyzed and chromated. The chromate treatment is applied to prevent oxidation of the electrolytic copper foil.
There are no effects on the HAZE value by various surface treatments.

  The electrolytic copper foil subjected to the chromate treatment was washed with water for 5 seconds and then naturally dried to obtain a surface-treated copper foil. HAZE METER NDH7000 (Nippon Denshoku) was formed by molding a double-sided copper-clad laminate using the obtained surface-treated copper foil and polyimide PIXEO BP (registered trademark) (manufactured by Kaneka Corporation) and etching the electrolytic copper foil on both sides. HAZE value was measured based on JIS K 7136

  Table 2 shows the measurement results.

[Number of protrusions on the rough side]
The height of the electrolytic copper foil rough surface was measured with a color 3D laser microscope VK-9700 (manufactured by Keyence Corporation). The height image obtained in the range of 211.692 μm × 282.348 μm was binarized, the threshold value was set from 3.0 μm to 0.5 μm, and the number of protrusions of each size was counted. The number of samples is 3.
Table 3 shows the number of protrusions in each example. FIG. 1 shows a binarized diagram of Example 1 and Comparative Example 1.

  From Table 2 and Table 3, the electrolytic copper foil in the present invention is an electrolytic copper foil having high elongation after heat treatment, high folding resistance, flexibility, and very few abnormal projections on the rough surface side. When the copper-clad laminate was used, it was confirmed that the HAZE value of the exposed resin base material after etching was 80% or less.

The electrolytic copper foil in the present invention is an electrolytic copper foil having a high elongation rate and folding resistance after heat treatment and being flexible, and having very few abnormal projections on the rough surface side. Is an electrolytic copper foil that can be suitably used for flexible printed wiring boards because the HAZE value of the exposed resin substrate after etching is low.
Therefore, the present invention has high industrial applicability.

Claims (6)

An electrolytic copper foil for a printed wiring board having a glossy surface of an electrolytic copper foil produced by continuously depositing on a drum-like rotating cathode surface as an adhesive surface with an insulating resin substrate, the TD direction of the glossy surface The electrolytic copper foil for a printed wiring board in which the specular gloss at an incident angle of 60 ° is 220 or less and the sum of the specular gloss at the incident angle of 60 ° in the TD direction and MD direction of the gloss surface is 350 or more. 2. The electrolytic copper foil for printed wiring boards according to claim 1, wherein the electrolytic copper foil glossy surface has a surface roughness Rz _JIS94 of 1.5 μm or less. The process copper foil which provided the 1 or 2 or more process layer in the electrolytic copper foil glossy surface for printed wiring boards of Claim 1 or 2. The copper clad laminated board which bonded the copper foil in any one of Claim 1 thru | or 3 to the insulating resin base material. The copper clad laminate according to claim 4, wherein the HAZE value is 80% or less. A printed wiring board formed using the copper clad laminate according to claim 4.