JPH08283886A - Electrolytic copper foil for flexible wiring board - Google Patents

Abstract

PURPOSE: To produce copper foil which has excellent elongatability and flexing resistance at ordinary and elevated temps. and is recrystallizable at a low temp. by suppressing the carbon content in the copper foil produced by an electrolytic method to a specific value or below and heat treating the copper foil at a specific temp. CONSTITUTION: A Ti drum-shaped cathode 2 is arranged in a concentrical Pb anode 1 on the outer side. An electrolyte 3 contg. proper amts. of copper, sulfuric acid, chlorine ions and org. matter, such as hydrolyzed glue is put into an electrolytic cell in which the anode is formed. While the drum-shaped cathode 2 is kept rotated, current is supplied between the anode 1 and the cathode 2 to electrolytically deposit copper on the surface of the drum-shaped cathode 2. The copper is taken up as the copper foil 4. In such a case, the carbon content in the copper foil 4 is confined to <=18ppm by controlling the amt. of the glue as the org. matter in the electrolyte 3. The resulted copper foil 4 is heat treated at 100 to 300 deg.C in a gaseous nitrogen atmosphere. The copper foil which is recrystallizable at a low temp. of about 120 deg.C, has the excellent performance compared with the conventional rolled copper foil and has the broad width hardly producible from the rolled copper foil is thus stably and inexpensively produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic copper foil for flexible wiring boards (hereinafter abbreviated as FPC).

[0002]

2. Description of the Related Art The FPC is a pattern in which a copper foil is attached to an insulating film such as polyimide or polyester with an adhesive, and an etching treatment is applied. Recently, in addition to this, FPCs that do not use an adhesive have begun to be used. It is mainly used for internal wiring of cameras, AV equipments, personal computers, computer terminal equipments, OA equipments such as HDDs and FDDs, mobile phones and car electronics equipments.

There are roughly two types of copper foil for FPC. One is a rolled copper foil that is formed into a foil by subjecting a copper ingot produced by casting to a rolling process. The other is an electrolytic copper foil produced by electrolyzing a solution containing copper sulfate as a main component, depositing copper in a foil shape on a rotating cathode and continuously peeling it off.

Since copper foil for FPC is required to have flexibility, rolled copper foil has been used in many cases. Rolled copper foil is FP
When heated in the curing process of the adhesive at the time of C production, 120-
It is annealed at a relatively low temperature of 160 ° C and softens,
This is because it has the characteristics of increased flexibility and elongation. However, the rolled copper foil is expensive, and the width of the copper foil produced by rolling is usually about 60 cm, which is a disadvantage in that the efficiency of FPC production is poor.

On the other hand, the electrolytic copper foil is cheaper than the rolled copper foil, and it is possible to produce a copper foil having a width of 100 cm or more, but the electrolytic copper foil produced by the conventional production method is Even when heated to 200 ° C. or higher, it was not annealed or softened, and had poor flexibility, so it was used only for FPC in a limited number of applications.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrolytic copper foil for FPC which can solve the above problems of the conventional electrolytic copper foil.

[0007]

[Means for Solving the Problems] Conventionally, as an electrolytic solution used for producing an electrolytic copper foil, copper and sulfuric acid are main components, to which a trace amount of an organic substance such as gelatin or glue is added, and hydrochloric acid or chloride is added. Those containing a small amount of chlorine ions such as sodium are used.

The reason for adding a trace amount of an organic substance to the electrolytic solution is that the organic additive has the function of adjusting the surface roughness of the electrolytic copper foil, increasing the tensile strength, and the surface of the copper foil during electrolysis. This is because it has the function of suppressing the occurrence of bumps. On the other hand, chloride ion acts to enhance the function of the organic additive.

On the other hand, the addition of this organic additive acts to reduce the elongation and flex resistance of the copper foil at room temperature and high temperature, and prevents recrystallization when heated. This is because the organic additive in the electrolytic solution is incorporated into the electrolytic copper foil, although the amount is small.

Organic impurities usually gather at the grain boundaries of the electrolytic copper foil. When the number of these impurity atoms is large, the movement of grain boundaries is governed by the diffusion rate of impurities. Therefore, the energy of movement of the grain boundaries is larger in the case of a metal containing a large amount of impurities, as compared with the case of a pure metal. That is, the electrolytic copper foil containing a certain amount or more of organic matter has a higher recrystallization temperature than a pure copper foil.

As a result of further research focusing on this phenomenon, the inventors of the present invention have achieved a remarkable increase in elongation and bending resistance at room temperature and high temperature by suppressing the amount of organic substances contained in the electro-deposited copper foil below a certain amount. It has been found that the recrystallization temperature can be lowered to less than 200 ° C.

Furthermore, by heat-treating the copper foil obtained by the above method at 100 ° C. or higher, elongation and bending resistance at room temperature and high temperature are further excellent, and recrystallization at a low temperature of about 120 ° C. We have developed a copper foil with the same or better performance than the conventional rolled copper foil.

That is, the copper foil of the present invention is characterized in that the amount of carbon in the untreated copper foil is 18 ppm or less.

Usually, an electrolytic copper foil is produced by subjecting a copper foil produced by an electrolytic foil producing apparatus to a roughening treatment for improving adhesion and a rust-preventing treatment by a surface treatment apparatus. The copper foil means a cathode (made of SUS or Ti): 2 on a rotating drum called an electrolytic foil making apparatus shown in FIG. 1, and a concentric anode (made of Pb or DSA): 1 with respect to the cathode. An electrolytic solution: 3 was passed through the apparatus, an electric current was passed between both electrodes to deposit copper to a predetermined thickness and then stripped off, resulting in a copper foil: 4
Say.

After that, in order to impart the required performance to the copper clad laminate, an untreated copper foil: 4 is passed through a surface treatment device as shown in FIG. 2 to carry out an electrochemical or chemical surface treatment. Do it continuously. The one after this surface treatment is called surface treated copper foil: 8 and is used for a copper clad laminate.
It is the performance of untreated copper foil: 4 that determines the mechanical performance of electrolytic copper foil. In this case, as the content of the organic carbon in the untreated copper foil decreases, the elongation at room temperature and high temperature increases, the bending resistance is good, and the recrystallization occurs at a low temperature of less than 200 ° C. The organic carbon content is preferably 18 ppm or less, more preferably 15 ppm or less.

The amount of the organic additive incorporated into the electrolytic copper foil can be known by quantifying C and S in the copper foil. This is because it is natural that C is a main component because the organic additive is an organic substance, but in many cases, an organic substance containing S is usually used as the additive. However, S is not incorporated only from the organic additive, but is incorporated also from the electrolyte because sulfuric acid is used as the main component of the electrolyte. In fact, S is detected in the electro-deposited copper foil even when an organic additive containing no S is used. Therefore, C is most suitable for the quantitative determination of the organic additive incorporated in the electrolytic copper foil. In addition, although carbon of an inorganic substance is not taken in to the usual electrolytic copper foil, even if taken in, it does not affect the elongation at room temperature and high temperature, the bending resistance, and the lowering of the recrystallization temperature. .

Furthermore, the above-mentioned electrolytic copper foil is placed at 100 ° C. to 30 ° C.
When heat-treated at a temperature of 0 ° C., the elongation and bending resistance at room temperature and high temperature are more excellent than those of the above-mentioned electrolytic copper foil, and recrystallization can be performed at a low temperature of around 120 ° C. The conventional foil is 1
Even when heat-treated at a temperature of 00 ° C. or higher, it does not exhibit the mechanical performance of the foil of the present invention. If the heat treatment temperature is lower than 100 ° C., such an effect does not occur. On the other hand, if the heat treatment temperature is higher than 300 ° C., the foil is completely annealed and recrystallized at the time of this heat treatment. Further, at a temperature of 300 ° C. or higher, heat shrinkage causes stretching and wrinkling of the foil, which is not preferable.

The heat treatment for further improving the elongation and bending resistance at room temperature and high temperature requires a longer time as the heating temperature is lower, and a shorter time as the heating temperature is higher. For example, it takes about 24 hours at 120 ° C. and about 10 seconds at 260 ° C. Therefore, when the heating temperature is low, a so-called batch heating method in which the coil-shaped copper foil is held in a furnace for heat treatment is suitable. When the heating temperature is high, a continuous heating method in which a copper foil is run in a heating furnace and heated is suitable.

[0019]

【Example】

Example 1 An electrolytic solution: 3 was passed through a device in which a rotating drum cathode (made of Ti): 2 and a concentric anode (made of DSA): 1 were arranged with respect to the cathode, and an electric current was passed between both electrodes. Copper foil: 4 was produced. The electrolytic solution contains 90 g / l of copper, 100 g / l of sulfuric acid, 20 ppm of chlorine ions, and 68 ppm of hydrolyzed glue. The liquid temperature was 55 ° C. and the current density was 55 A / dm ² . After that, a roughening treatment for improving adhesion and a rustproofing treatment were carried out by a usual method through a surface treatment device to obtain a 35 μ copper foil. The amount of carbon in the untreated copper foil of this example is shown in Table 1 together with those of Examples 2 to 4 and Comparative Example 1.
It was shown to.

In order to keep the amount of organic substances taken into the untreated copper foil below a certain amount, it is necessary to keep the concentration of the organic additive in the liquid below a certain amount as well as the type and molecular weight of the additive used. is there. Increase the carbon content in copper foil to 18
In order to reduce the concentration to ppm or less, in the case of hydrolyzed glue, the solution temperature and the current density for producing ordinary electrolytic copper foil are 0-2.
It is necessary to be in the range of about 50 ppm.

Example 2 The copper foil produced under the conditions of Example 1 was placed in a 6 m heating furnace in which the conditions inside the furnace were controlled at a temperature of 260 ° C. in a N ₂ atmosphere.
Heat treatment by running at m / min (residence time in furnace: 30 seconds)
did.

Example 3 The copper foil produced under the conditions of Example 1 was subjected to 120 N ₂ atmosphere.
It was kept in a batch furnace controlled at a temperature of ° C for 24 hours.

Example 4 Hydrolyzed Hydroxyethyl Cellulose (HEC) 81 ppm in place of hydrolyzed glue and HE before hydrolysis
The same treatment as in Example 1 was carried out except that C: 2 ppm was used to obtain a 35 μ copper foil.

Comparative Example 1 An electrolytic solution containing 90 g / l of copper, 100 g / l of sulfuric acid, 20 ppm of chlorine ions and 3002 ppm of hydrolyzed glue was further added with 2 ppm of glue before hydrolysis. Electrolysis was performed under the conditions of a liquid temperature of 55 ° C. and a current density of 55 a / dm ² to produce a copper foil. After that, a roughening treatment and an anticorrosion treatment for improving adhesion are performed by a usual method,
A μ copper foil was obtained.

Comparative Example 2 A commercially available rolled copper foil (tough pitch copper, azuroll foil) was prepared.

[0026]

[Table 1]

Test Results Performance measurement results of copper foils produced by simulating the FPC adhesive application and curing processes for the copper foils of Examples 1 to 3 and Comparative Examples 1 and 2 (all examples except Example 4). Was heat-treated at 120 to 180 ° C. for 1 hour) is shown in Table 2.

[0028]

[Table 2]

Regarding the electrolytic copper foil obtained in Example 1 of the present invention, a cross section of the metal structure after treatment at 180 ° C. for 1 hour is shown in FIG. 3, and the electrolytic copper foils obtained in Examples 2 and 3 are Fig. 4 shows a cross section of the metallographic structure after treatment at 120 ° C for 1 hour.
(Example 2) and FIG. 5 (Example 3), respectively.

The copper foils of Examples 1 to 3 according to the present invention are shown in Table 1.
As shown in, the amount of carbon in the untreated copper foil is 6.8 ppm.
Is.

The copper foil of Example 1 is 160 to 180 ° C. × 1H
Recrystallization occurs at r, and in terms of mechanical performance, the copper foil after heat treatment under the above temperature conditions has a large elongation at room temperature and a high MIT folding endurance value. Further, the elongation at high temperature is large, and it can be seen that the crystal structure of FIG. 3 is completely recrystallized at 180 ° C. × 1 Hr.

In the case of the copper foils of Examples 2 and 3, the elongation at room temperature and high temperature was already large in the normal state, and the temperature was 120 to 180 ° C. × 1H.
Although there is no change in the mechanical performance of r after heat treatment compared with the normal state, it can be seen from the crystal structure point that it is completely recrystallized at 120 ° C. as shown in FIGS. 4 and 5.

As shown in Table 1, in the copper foil of Example 4, the amount of carbon in the untreated copper foil is 14.0 ppm. In terms of mechanical performance, the elongation at room temperature and high temperature is large, and the value of MIT folding endurance is also large. However, in this case 120-1
Although recrystallization proceeds by heat treatment at 80 ° C. × 1 Hr, it does not completely recrystallize like the copper foils of Examples 1 to 3.

On the other hand, the conventional electrolytic copper foil of Comparative Example 1 contains 23.0 ppm of carbon in the untreated copper foil, as shown in Table 1, at 120 to 180 ° C. × 1 Hr. Recrystallization does not occur even when heated, as shown in Table 2, both the elongation at room temperature and the temperature are small, and the MIT folding endurance is also small.
It can be seen from the crystal structure of FIG. 6 that recrystallization did not occur at 180 ° C. × 1 Hr.

In the case of the rolled copper foil shown in Comparative Example 2, recrystallization occurs at about 140 ° C. as shown in FIGS. 7 and 8, and the elongation at room temperature increases as shown in Table 2. .
However, the absolute values of room temperature elongation, high temperature elongation, and MIT folding endurance are inferior to those of the electrolytic copper foil of the present invention.

[0036]

INDUSTRIAL APPLICABILITY The electrolytic copper foil according to the present invention is recrystallized at a low temperature of less than 200 ° C. as compared with the conventional electrolytic copper foil, and is excellent in bending resistance and elongation at room temperature and high temperature. Has performance equivalent to or better than foil. Further, it is cheaper than the rolled copper foil and a wide foil can be manufactured, so that the productivity is also improved.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a configuration of an electrolytic foil-making apparatus.

FIG. 2 is a diagram schematically showing a configuration of a surface treatment device.

FIG. 3 is a photograph showing a metallographic structure of an electrolytic copper foil (normal state and heat treatment: after 180 ° C. × 1 Hr) manufactured according to Example 1.

FIG. 4 is a photograph showing a metallographic structure of an electrolytic copper foil (normal state and heat treatment: after 120 ° C. × 1 Hr) manufactured according to Example 2.

FIG. 5 is a photograph showing a metallographic structure of an electrolytic copper foil (normal state and heat treatment: after 120 ° C. × 1 Hr) manufactured according to Example 3.

FIG. 6 is a photograph showing a metallographic structure of an electrolytic copper foil (normal state and heat treatment: after 180 ° C. × 1 Hr) manufactured according to Comparative Example 1.

FIG. 7: Rolled copper foil of Comparative Example 2 (normal state and heat treatment: 12
It is a photograph showing a metallographic structure at 0 ° C x 1 hr).

FIG. 8: Rolled copper foil of Comparative Example 2 (heat treatment: 140 ° C., 1
It is a photograph showing a metallographic structure at 80 ° C x 1 hour after each).

[Explanation of symbols]

 1 Anode of electrolytic foil making apparatus 2 Cathode of electrolytic foil making apparatus 3 Electrolyte of electrolytic foil making apparatus 4 Untreated copper foil 5 Electrolyte of surface treatment equipment 6 Electrolyte of surface treatment equipment 7 Anode of surface treatment equipment 8 Surface treatment Copper foil

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsutomu Saito 2 601 Ojizawa, Imaichi City, Tochigi Prefecture Furukawa Sir Kitfoil Co., Ltd. Imaichi Plant

Claims (2)

[Claims] 1. An electrolytic copper foil for a flexible wiring board, wherein the amount of carbon in the untreated copper foil is 18 ppm or less. 2. The electrolytic copper foil according to claim 1, which is heat-treated at a temperature of 100 ° C. to 300 ° C.