TWI422484B - Printed wiring board with copper foil - Google Patents

Description

Copper foil for printed wiring board

The present invention relates to a copper foil for a printed wiring board, and more particularly to a copper foil for a flexible printed wiring board.

Printed wiring boards have developed rapidly over the past half century and are used today in almost all electronic devices. In recent years, the demand for miniaturization and high performance of electronic devices has increased, and the high-density mounting of components and the high-frequency of signals have been increasing. The printed wiring boards are also required to be fine-grained (fine pitch). ) and high frequency correspondence.

The printed wiring board is usually manufactured by adhering an insulating substrate to a copper foil to form a copper clad laminate, and then forming a conductor pattern on the copper foil surface by etching. Therefore, the copper foil for printed wiring boards is required to have adhesion to an insulating substrate and etching property.

A technique for improving the adhesion to an insulating substrate is usually performed by a surface treatment called roughening treatment to form irregularities on the surface of the copper foil. For example, the method has the following methods: using a copper sulfate acid plating bath on the M surface (rough surface) of the electrolytic copper foil, and electrodepositing a plurality of dendritic or small spherical copper to form fine irregularities, and using a quenching effect Improve adhesion. After the roughening treatment, in order to further improve the subsequent characteristics, chromic acid treatment or treatment with a decane coupling agent or the like is usually performed.

Further, a method of forming a metal layer or an alloy layer of tin, chromium, copper, iron, cobalt, zinc, nickel or the like on the surface of a smooth copper foil which has not been subjected to the roughening treatment is also known.

Since many polyimide substrates are used for the copper foil, a method of coating the surface of the copper foil with chromium having a high bonding strength with polyimine is generally used.

Further, research and development have been made as follows: as a surface treatment for the surface of a smooth copper foil, a first metal layer for preventing diffusion of Cu atoms into the polyimide layer is formed, and the etching property is good on the first metal layer. As a second metal layer, a Cr layer having good adhesion to an insulating substrate is formed to a small extent, and good adhesion to the insulating substrate and good etching property are simultaneously obtained. This is because if the Cu atom or the Cu oxide diffuses toward the polyimine side, the polyimide layer in the vicinity of the interface becomes weak and becomes the starting point of the peeling.

The method of coating the surface of the copper foil with a chromium layer has a wet processing method, a dry processing method, and the like. Wherein the method of coating the chromium layer on the surface by wet treatment comprises: forming a Zn layer or a Zn alloy layer on the surface of the copper foil, and forming a chromate layer on the layer; and forming a surface on the copper foil A layer of Zn followed by no formation of a chromate layer on the layer. An example of the former is disclosed in Patent Document 1, and an example of the latter is disclosed in Patent Document 2. When a chromate layer is formed on the Zn layer or the Zn alloy layer, a substitution reaction occurs between Zn in the Zn layer or the Zn alloy layer and Cr ⁶⁺ in the solution, and a hydroxide of Cr is precipitated. In this method, Cr is precipitated in the form of a hydroxide. Therefore, the valence of the precipitated Cr is not zero, but is a trivalent excellent in adhesion to polyimine.

Further, a method using dry processing is disclosed in Patent Document 3. Patent Document 3 discloses that a Ni—Cr alloy layer is formed on the surface of a copper foil, and then an oxide layer having a specific thickness is formed on the surface of the alloy layer, thereby smoothing the surface of the copper foil and having a low leveling effect. The adhesion to the resin substrate can also be greatly improved. Further, a copper foil for a printed wiring board in which a Ni-Cr alloy layer of 1 to 100 nm is formed by vapor deposition on the surface, and a Cr oxide layer having a thickness of 0.5 to 6 nm is formed on the surface of the alloy layer, and the surface is formed. The average surface roughness Rz JIS is 2.0 μm or less.

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2005-344174

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2007-007937

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2007-207812

In the above various prior arts, the method of improving the adhesion by the roughening treatment is not preferable from the viewpoint of forming a fine pitch circuit. In other words, when the conductor spacing is narrowed by the fine pitch, the roughening treatment portion remains on the insulating substrate after the circuit is formed by etching, and the insulation is deteriorated. If the entire roughened surface is to be etched in order to prevent this, a long etching time is required and a specific wiring width cannot be maintained.

From the viewpoint of strength, the method of polyimine on the surface area of the smooth copper foil is inferior to the method of roughening the area of the polyimide layer. The reason for this is that the roughening treatment surface obtains the bonding strength due to the quenching effect. On the other hand, when the roughening treatment is not performed, the registration effect is not obtained, and since the Cu atoms are diffused in the polyimide. This causes the polyimine layer near the interface to become weak, making this part the starting point for the peeling.

Further, in the dry treatment, for example, a method of providing a Ni layer or a Ni-Cr alloy layer has a large space for improvement in the basic characteristics of the adhesion to the insulating substrate. The former is due to the absence of Cr ³⁺ which is excellent in adhesion to polyimine or the like, and the latter is due to coexistence with Ni in the film, so the existence ratio of Cr ³⁺ is low.

Further, in the method of providing the Cr layer by dry treatment, although a high bonding strength can be obtained at room temperature, when the laminated body is subjected to hot working, if the layer thickness is thin, it is derived from copper foil. The Cu atoms diffuse into the Cr layer and intrude into the polyimide layer to deteriorate the adhesion strength. On the other hand, if the Cr layer is thick enough to prevent the diffusion of Cu atoms, the surface treatment layer is inferior in etching property. This is a phenomenon in which Cr is left on the insulating substrate after etching treatment to form a circuit pattern, which is called "etching residue".

Further, the surface treatment layers described in Patent Documents 1 and 2 are formed by plating. At this time, the copper foil itself acts as an electrode for electrochemical reaction. The surface of the copper foil has irregularities such as oil pits, and there are inclusions of several hundred nm in the vicinity of the surface, so that the flow of electrons is hindered in this portion, and it is not easy to form a very thin surface treatment layer with a uniform thickness. It is difficult to achieve the adhesion to the polyimide and the etching property at the same time.

In addition, the inventors of the present invention have found that it is necessary to form a chromate layer on the Zn layer or the Zn alloy layer in order to adhere Cr to the surface of the copper foil, which is effective for adhesion to polyimine, but is described in Patent Document 1. In the case where a chromate layer is formed on the Ni-Zn alloy layer, the concentration of chromium oxide in the vicinity of the interface becomes low, and high bonding strength cannot be obtained. Further, as described in Patent Document 2, when a chromate layer is not formed on the Zn layer or the Zn alloy layer, since the substitution reaction between Zn and Cr ⁶⁺ cannot be utilized, the adhesion amount of Cr exists. limit.

Therefore, an object of the present invention is to provide a copper foil for a printed wiring board which is excellent in both adhesiveness and etching property with an insulating substrate and which is suitable for fine pitch.

It has been conventionally thought that if the coating layer is made thinner, the strength of the bonding is lowered. However, as a result of intensive research by the present inventors, when the Cr layer is uniformly provided with a very thin thickness of the nanometer level, the concentration of Cr oxide in the vicinity of the interface can be increased as compared with the wet plating. Excellent adhesion to an insulating substrate can be obtained. By making the thickness extremely thin, the amount of Cr having low etching property is reduced, and the coating layer is uniform, which is advantageous for etching property. Further, by providing a layer for preventing diffusion of Cu atoms directly under the Cr, it is possible to provide a copper foil laminated substrate which can withstand a severe use environment.

According to one aspect of the present invention, which is based on the above findings, a copper foil for a printed wiring board comprising a copper foil substrate and a coating layer covering at least a part of a surface of the copper foil substrate, the coating layer The intermediate layer and the Cr layer composed of a single metal or alloy laminated from the surface of the copper foil substrate, and Cr is present in an amount of 18 to 180 μg/dm ^{2 in} the coating layer, and the XPS will be used according to the use of XPS. The atomic concentration (%) of the metal chromium in the depth direction (x: unit nm) obtained from the depth direction analysis from the surface is f ₁ (x), and the atomic concentration (%) of the oxide chromium is set to f ₂ ( x), the atomic concentration (%) of the entire chromium is set to f(x)(f(x)=f ₁ (x)+f ₂ (x)), and the atomic concentration (%) of nickel is set to g(x) ), the atomic concentration (%) of copper is h (x), the atomic concentration (%) of oxygen is i (x), and the atomic concentration (%) of carbon is set to j (x), and other metals are used. The sum of the atomic concentrations is set to k(x), then within the interval [0,1.0], ∫h(x)dx/(∫f(x)dx+∫g(x)dx+∫h(x)dx+∫i (x) dx+∫j(x)dx+∫k(x)dx) is 10% or less, ∫f ₂ (x)dx/(∫f(x)dx+∫g(x)dx+∫h(x)dx+∫ i(x)dx+∫j(x)dx+∫k(x)dx) More than 20%, in the interval [1.0, 2.5], the satisfying _{0.1 ≦ ∫f 1 (x) dx} / ∫f 2 (x) dx ≦ 1.0.

In one embodiment of the copper foil for a printed wiring board of the present invention, Cr is present in an amount of 30 to 145 μg/dm ² .

In another embodiment of the copper foil for a printed wiring board of the present invention, Cr is present in an amount of 36 to 90 μg/dm ² .

In still another embodiment of the copper foil for a printed wiring board of the present invention, Cr is present in an amount of 36 to 75 μg/dm ² .

In still another embodiment of the copper foil for a printed wiring board of the present invention, the intermediate layer contains at least one of Ni, Mo, Ti, Zn, Co, V, Sn, Mn, and Cr.

In still another embodiment of the copper foil for a printed wiring board of the present invention, the coating layer is an intermediate layer composed of any one of Ni, Mo, Ti, Zn, and Co laminated on the surface of the copper foil substrate. In the intermediate layer, any of Ni, Mo, Ti, Zn, and Co is present in an amount of 15 to 1030 μg/dm ² .

In still another embodiment of the copper foil for a printed wiring board of the present invention, Ni is present in an amount of 15 to 440 μg/dm ² in the intermediate layer, and Mo is present in an amount of 25 to 1030 μg/dm ² , and Ti is 15 in the coating layer. ~ 140μg / dm ² amount of coating present, Zn to 15 ~ 750μg / dm ² amount of coating is present, or an amount of Co in the coating 25 ~ 1030μg / dm ² of the present.

In still another embodiment of the copper foil for a printed wiring board of the present invention, the coating layer is composed of at least two of Ni, Zn, V, Sn, Mn, Cr, and Cu which are sequentially laminated from the surface of the copper foil substrate. The intermediate layer and the Cr layer are composed of an alloy, and in the intermediate layer, any two of Ni, Zn, V, Sn, Mn, and Cr are present in an amount of 20 to 1700 μg/dm ² .

In still another embodiment of the copper foil for a printed wiring board of the present invention, the intermediate layer is made of a Ni alloy composed of Ni, Zn, V, Sn, Mn, and Cr.

A printed wiring board according to the present invention and then a copper foil with a further embodiment, the intermediate layer is Ni-Zn-based in a coating amount of 15 ~ 1000μg / dm Ni ² and of 5 ~ 750μg / dm Zn ² composed of an alloy of, by the A Ni-V alloy composed of Ni and V having a total coating amount of 20 to 600 μg/dm ² and a Ni-Sn alloy composed of Ni and Sn having a total coating amount of 18 to 450 μg/dm ² and having a coating amount of 15 to 450 μg. / dm Ni ² of and the Ni-Mn alloy 5 ~ 200μg / dm Mn ² constitutes of a coating amount of 20 ~ 440μg / Ni-Cr alloy dm Ni ^2's and 5 ~ 110μg / dm Cr ² constitutes constituted .

In still another embodiment of the copper foil for a printed wiring board of the present invention, the intermediate layer is made of a Cu alloy composed of any one or two of Cu, Zn, and Ni.

A printed wiring board according to the present invention and then a copper foil with a further embodiment, the intermediate coating layer system in an amount of Zn is 15 ~ 750μg / dm Cu-Zn alloy of ^2, Ni-coated in an amount of 15 ~ 440μg / dm Cu ² of -Ni alloy, or Ni coating in an amount of 15 ~ 1000μg / dm ² and Zn coating amount of 5 ~ 750μg / dm Cu-Ni -Zn alloy composed of ^2.

In still another embodiment of the copper foil for a printed wiring board of the present invention, when the cross section of the coating layer is observed by a transmission electron microscope, the maximum thickness is 0.5 to 12 nm, and the minimum thickness is 80% or more of the maximum thickness.

In still another embodiment of the copper foil for a printed wiring board of the present invention, when the heat treatment for hardening of the polyimine is performed, the depth direction (x: according to the depth direction analysis from the surface by XPS is used. The atomic concentration (%) of the metal chromium per unit nm is f ₁ (x), the atomic concentration (%) of the oxide chromium is f ₂ (x), and the atomic concentration (%) of the entire chromium is set to f. (x) (f(x)=f ₁ (x)+f ₂ (x)), the atomic concentration (%) of nickel is set to g(x), and the atomic concentration (%) of copper is set to h(x) In the case where the atomic concentration (%) of oxygen is i(x), the atomic concentration (%) of carbon is j(x), and the sum of the atomic concentrations of other metals is k(x), Within [0,1.0], ∫h(x)dx/(∫f(x)dx+∫g(x)dx+∫h(x)dx+∫i(x)dx+∫j(x)dx+∫k(x) Dx) is 10% or less, ∫f ₂ (x)dx/(∫f(x)dx+∫g(x)dx+∫h(x)dx+∫i(x)dx+∫j(x)dx+∫k(x ) dx) is 20% or more, and within the interval [1.0, 2.5], 0.1 ≦∫ f ₁ (x) dx / ∫ f ₂ (x) dx ≦ 1.0 is satisfied.

In still another embodiment of the copper foil for a printed wiring board according to the present invention, the copper foil for a printed wiring board is a copper foil for a printed wiring board which is subjected to a heat treatment for hardening the polyimide, and is based on the use of XPS. The atomic concentration (%) of the metal chromium in the depth direction (x: unit nm) obtained by the depth direction analysis of the surface is f ₁ (x), and the atomic concentration (%) of the oxide chromium is set to f ₂ (x) The atomic concentration (%) of the entire chromium is set to f(x)(f(x)=f ₁ (x)+f ₂ (x)), and the atomic concentration (%) of nickel is set to g(x). The atomic concentration (%) of copper is h(x), the atomic concentration (%) of oxygen is i(x), and the atomic concentration (%) of carbon is set to j(x), and atoms of other metals are used. The sum of the concentrations is set to k(x), then within the interval [0,1.0], ∫h(x)dx/(∫f(x)dx+∫g(x)dx+∫h(x)dx+∫i(x ) dx+∫j(x)dx+∫k(x)dx) is 10% or less, ∫f ₂ (x)dx/(∫f(x)dx+∫g(x)dx+∫h(x)dx+∫i( x)dx+∫j(x)dx+∫k(x)dx) is 20% or more, within the interval [1.0, 2.5], satisfying 0.1≦∫f ₁ (x)dx/∫f ₂ (x)dx≦1.0 .

In still another embodiment of the copper foil for a printed wiring board of the present invention, when the surface of the coating layer after the insulating substrate is peeled off from the coating layer is analyzed for the copper foil for a printed wiring board having the insulating substrate formed through the coating layer If the atomic concentration (%) of the metal chromium in the depth direction (x: unit nm) obtained by analyzing the depth direction from the surface by XPS is f ₁ (x), the atomic concentration of the oxide chromium (%) ) is f ₂ (x), and the atomic concentration (%) of the entire chromium is f(x) (f(x)=f ₁ (x)+f ₂ (x)), and the atomic concentration of nickel (%) ) is set to g(x), the atomic concentration (%) of copper is h(x), the atomic concentration (%) of oxygen is i(x), and the atomic concentration (%) of carbon is set to j ( x), the sum of the atomic concentrations of other metals is k(x), and the distance from the surface layer where the concentration of metallic chromium is the largest is F, which satisfies 0.1≦∫f in the interval [0, F] ₁ (x)dx/∫f ₂ (x)dx≦1.0, and ∫h(x)dx/(∫f(x)dx+∫g(x)dx+∫h(x)dx+∫i(x)dx+∫ j(x)dx+∫k(x)dx) is 10% or less.

In still another embodiment of the copper foil for a printed wiring board of the present invention, the copper foil substrate is a rolled copper foil.

In still another embodiment of the copper foil for a printed wiring board of the present invention, the printed wiring board is a flexible printed wiring board.

Another aspect of the present invention is a copper clad laminate provided with the copper foil of the present invention.

In one embodiment of the copper clad laminate of the present invention, the copper foil is followed by the polyimine.

Still another aspect of the present invention is a printed wiring board using the copper clad laminate of the present invention as a material.

According to the present invention, it is possible to obtain a copper foil for a printed wiring board which is excellent in both adhesiveness and etching property with an insulating substrate and which is suitable for fine pitch. Further, the present invention is also applicable to electromagnetic shielding, high-frequency shielding, and a technique of laminating a resin such as polyimide or polyamide to a metal strip for insulation.

(copper foil substrate)

The form of the copper foil substrate which can be used in the present invention is not particularly limited, and it can be typically used in the form of a rolled copper foil or an electrolytic copper foil. Usually, an electrolytic copper foil is produced by electrolytically depositing copper from a copper sulfate plating bath onto a titanium or stainless steel drum, and the rolled copper foil is repeatedly produced by plastic working and heat treatment using a calender roll. Rolled copper foil is often used for applications requiring flexibility.

As the material of the copper foil substrate, in addition to high-purity copper such as copper or oxygen-free copper which is usually used as a conductor pattern of a printed wiring board, for example, copper doped with Sn or copper doped with Ag may be used. A copper alloy such as Cr, Zr or Mg, or a copper alloy such as a Cason copper alloy such as Ni or Si. Further, in the present specification, when the term "copper foil" is used alone, a copper alloy foil is also included.

The thickness of the copper foil substrate which can be used in the present invention is also not particularly limited as long as it is appropriately adjusted to a thickness suitable for a printed wiring board. For example, it can be about 5 to 100 μm. In the case of forming a fine pattern, it is 30 μm or less, preferably 20 μm or less, and typically about 5 to 20 μm.

It is preferable that the copper foil substrate used in the present invention is not subjected to roughening treatment. In the past, it has been generally the case that the surface roughening treatment is performed by attaching a special plating to the surface to the micron-sized unevenness, and the physical property is applied to make it have adhesion to the resin. On the other hand, however, in terms of fine pitch and high-frequency electrical characteristics, a smooth foil is good, and a roughened foil develops in an unfavorable direction. Moreover, since the roughening process step is omitted, the effect of improving economy and productivity is also obtained. Therefore, the foil used in the present invention is a foil which is not particularly subjected to roughening treatment.

(covering layer)

A coating layer is formed on at least a portion of the surface of the copper foil substrate. The portion to be coated is not particularly limited, and is usually a portion to be placed next to the insulating substrate. By the presence of the coating layer, the adhesion to the insulating substrate is improved. The coating layer is composed of an intermediate layer and a Cr layer which are sequentially laminated from the surface of the copper foil substrate. The intermediate layer preferably contains at least one of Ni, Mo, Ti, Zn, Co, V, Sn, Mn, and Cr. The intermediate layer may also be composed of a single metal, and is preferably composed of, for example, Ni, Mo, Ti, Zn, and Co. The intermediate layer may be composed of an alloy, and is preferably made of, for example, an alloy of at least two of Ni, Zn, V, Sn, Mn, Cr, and Cu. Further, the intermediate layer may be composed of a Ni alloy composed of Ni and any of Zn, V, Sn, Mn, and Cr, or may be composed of Cu, a Cu alloy composed of either or both of Zn and Ni. . Generally, the adhesion between the copper foil and the insulating substrate tends to decrease if placed under a high temperature environment, and it is considered to be caused by the thermal diffusion of copper to the surface and reaction with the insulating substrate. In the present invention, by disposing the intermediate layer which can effectively prevent copper from diffusing on the copper foil substrate in advance, heat diffusion of copper can be prevented. Here, in the various intermediate layers provided to prevent copper diffusion, although the Cu alloy layer contains copper which is not intended to be diffused on the surface, since copper is alloyed, it does not diffuse to the surface, and has a good adhesion. Sex, and will not adversely affect the etchability.

Further, by providing a Cr layer which is more excellent in adhesion to the insulating substrate than the intermediate layer on the intermediate layer, the adhesion to the insulating substrate can be further improved. Since the intermediate layer is present, the thickness of the Cr layer can be made thin, so that the adverse effect on the etching property can be reduced. In addition, in the present invention, the adhesive property refers to the adhesiveness (heat resistance) after being placed at a high temperature and the adhesiveness (moisture resistance) after being placed under high humidity, in addition to the adhesiveness in the normal state.

In the copper foil for a printed wiring board of the present invention, the coating layer is extremely thin and uniform in thickness. The reason why the adhesion to the insulating substrate can be improved by such a configuration is not clear, but it is presumed that the Cr single-layer film which is excellent in adhesion to the resin on the intermediate layer is the outermost surface, so After the high-temperature heat treatment in the imidization (about 30 minutes to several hours at about 350 ° C), a single-layered film structure having high adhesion is also maintained. Further, it is considered that the etching property is improved by making the coating layer extremely thin and reducing the amount of Cr used by the two-layer structure of the intermediate layer and Cr.

Specifically, the intermediate layer of the present invention has the following constitution.

(1) Identification of the coating

In the present invention, at least a part of the surface of the copper foil material is coated in the order of the intermediate layer and the Cr layer. The coating layer is identified by a surface analysis device such as XPS or AES, and argon sputtering is performed from the surface layer to perform chemical analysis in the depth direction, and the intermediate layer and the Cr layer can be identified due to the presence of different detection peaks. Further, the order of the coating can be confirmed based on the position of each detection peak.

(2) Adhesion amount

On the other hand, since these intermediate layers and Cr layers are very thin, it is difficult to perform accurate thickness evaluation using XPS or AES. Therefore, in the present invention, the thicknesses of the intermediate layer and the Cr layer are evaluated by the weight of the coated metal per unit area. In the coating layer of the present invention, Cr is present in an amount of 18 to 180 μg/dm ² . If Cr less than 18μg / dm ^2, it can not obtain a sufficient peel strength, when Cr exceeds 180μg / dm ^2, the etching tends to have significantly decreased the. The coating amount of Cr is preferably 30 ~ 145μg / dm ^2, more preferably 36 ~ 90μg / dm ^2, and still more preferably 36 ~ 75μg / dm ^2.

Further, when the intermediate layer is composed of any one of Ni, Mo, Ti, Zn and Co, it is preferred that in the intermediate layer, any of Ni, Mo, Ti, Zn and Co is 15 to 1030 μg/dm ² The amount of coverage exists. At this time, if the coating amount is less than 15 μg/dm ² , sufficient peel strength cannot be obtained, and when it exceeds 1030 μg/dm ² , the etching property tends to be remarkably lowered.

Further, in this case, it is preferable that Ni is present in an amount of 15 to 440 μg/dm ² in the intermediate layer, Mo is present in a coating amount of 25 to 1030 μg/dm ² , and Ti is present in an amount of 15 to 140 μg/dm ² . , Zn to 15 ~ 750μg / dm ² amount of coating is present, or an amount of Co in the coating 25 ~ 1030μg / dm ² of the present.

Further, when the intermediate layer is composed of an alloy of at least two of Ni, Zn, V, Sn, Mn, Cr, and Cu, it is preferable that Ni, Zn, V, Sn, Mn, and Cr are in the intermediate layer. At least two of them are present in an amount of 20 to 1700 μg/dm ² . At this time, if the coating amount is less than 20 μg/dm ² , sufficient peel strength cannot be obtained, and when it exceeds 1700 μg/dm ² , the etching property tends to be remarkably lowered.

Further, when the intermediate layer is composed of a Ni alloy composed of Ni and any of Zn, V, Sn, Mn, and Cr, it is preferable that the intermediate layer is Ni and 5 having a coating amount of 15 to 1000 μg/dm ² ~ Ni-Zn alloy 750μg / dm Zn ² constitutes of the total coating amount of 20 ~ 600μg / dm Ni ^2's and Ni-V alloy V composed of, the total coating amount of 18 ~ 450μg / dm Ni ² of and Ni-Sn alloy of Sn, the coating amount of Ni-Mn alloy 15 ~ 450μg / dm Ni ^2's and 5 ~ 200μg / dm Mn ² constitutes of a coating amount of 20 ~ 440μg / dm ² of Ni and 5 It is composed of a Ni-Cr alloy composed of Cr of 110 μg/dm ² .

Further, when the intermediate layer consisting of Cu, Zn and Ni, when any one of the one or Cu alloy composed of two kinds of configuration, the intermediate layer is preferred that the coating amount of Zn is 15 ~ 750μg / dm ² of the Cu-Zn alloy , Ni coating amount of 15 ~ 440μg / dm Cu-Ni alloy of ² or Ni coating amount of 15 ~ 1000μg / dm ² and Zn coating amount of 5 ~ 750μg / dm Cu-Ni -Zn alloy composed of ^2.

(3) Observation using a transmission electron microscope (TEM)

When the cross section of the coating layer of the present invention is observed by a transmission electron microscope, it is a coating layer having a maximum thickness of 0.5 nm to 12 nm, preferably 1.0 to 2.5 nm, and a minimum thickness of 80% or more of the maximum thickness. It is more than 85%, and there are very few differences. The reason for this is that if the thickness of the coating layer is less than 0.5 nm, the deterioration of the peel strength is large in the heat resistance test and the moisture resistance test, and when the thickness exceeds 12 nm, the etching property is lowered. When the minimum thickness is 80% or more of the maximum value, the thickness of the coating layer is very stable, and hardly changes after the heat resistance test. When observed by TEM, it is difficult to find a clear boundary between the intermediate layer and the Cr layer in the coating layer, and it appears as a single layer (see Fig. 1). According to the findings of the present inventors, it is considered that the coating layer found in the TEM observation is a layer mainly composed of Cr, and the intermediate layer is also considered to exist on the side of the copper foil substrate. Therefore, in the present invention, the thickness of the coating layer at the time of TEM observation is defined as the thickness of the coating layer which appears to be a single layer. However, depending on the observation site, there is also a ambiguity in the boundary of the coating layer, and such a portion is excluded from the measurement portion of the thickness.

It is considered that the constitution according to the present invention has a stable thickness since it can suppress the diffusion of Cu. The copper foil of the present invention and the polyimide film are then subjected to a heat resistance test (after standing at a temperature of 150 ° C and a high temperature environment under an air atmosphere for 168 hours), and then the thickness of the coating layer hardly changes after the resin is peeled off. The maximum thickness is 0.5 to 12 nm, and the minimum thickness can also maintain 80% of the maximum thickness.

(4) Oxidation state of the surface of the coating layer

First, in terms of improving the adhesion strength, it is desirable that the internal copper does not diffuse to the outermost surface of the coating layer (from 0 to 1.0 nm from the surface). Therefore, in the copper foil for a printed wiring board of the present invention, it is preferable to set the atomic concentration (%) of the metal chromium in the depth direction (x: unit nm) obtained by the depth direction analysis from the surface by XPS. f ₁ (x), the atomic concentration (%) of the oxide chromium is set to f ₂ (x), and the atomic concentration (%) of the entire chromium is set to f(x)(f(x)=f ₁ (x) +f ₂ (x)), the atomic concentration (%) of nickel is set to g(x), the atomic concentration (%) of copper is h(x), and the atomic concentration (%) of oxygen is set to i ( x), if the atomic concentration (%) of carbon is set to j(x) and the sum of the atomic concentrations of other metals is k(x), then within the interval [0, 1.0], ∫h(x)dx/ (∫f(x)dx+∫g(x)dx+∫h(x)dx+∫i(x)dx+∫j(x)dx+∫k(x)dx) is 10% or less.

Further, it is preferable that the atomic concentration (%) of the metal chromium in the depth direction (x: unit nm) obtained by analyzing the depth direction from the surface by XPS is performed when the heat treatment for the hardening of the polyimine is performed. Let f ₁ (x), set the atomic concentration (%) of the oxide chromium to f ₂ (x), and set the atomic concentration (%) of the entire chromium to f(x)(f(x)=f ₁ ( x)+f ₂ (x)), the atomic concentration (%) of nickel is set to g(x), the atomic concentration (%) of copper is h(x), and the atomic concentration (%) of oxygen is set to x. i(x), where the atomic concentration (%) of carbon is set to j(x), and the sum of the atomic concentrations of other metals is k(x), then within the interval [0, 1.0], ∫h(x) Dx/(∫f(x)dx+∫g(x)dx+∫h(x)dx+∫i(x)dx+∫j(x)dx+∫k(x)dx) is 10% or less.

Further, when the surface of the coating layer from which the insulating substrate is peeled off from the coating layer is analyzed for the copper foil for a printed wiring board in which the insulating substrate is formed through the coating layer, the depth from the surface by the XPS is preferably used. The atomic concentration (%) of the metal chromium in the depth direction (x: unit nm) obtained by the direction analysis is f ₁ (x), and the atomic concentration (%) of the oxide chromium is set to f ₂ (x), and the entire chromium is obtained. The atomic concentration (%) is f(x)(f(x)=f ₁ (x)+f ₂ (x)), and the atomic concentration (%) of nickel is set to g(x), and the atom of copper is used. The concentration (%) is set to h(x), the atomic concentration (%) of oxygen is set to i(x), the atomic concentration (%) of carbon is set to j(x), and the sum of the atomic concentrations of other metals is set. For k(x), the distance from the surface layer with the largest concentration of metal chromium is set to F, then within the interval [0, F], ∫h(x)dx/(∫f(x)dx+∫g(x Dx+∫h(x)dx+∫i(x)dx+∫j(x)dx+∫k(x)dx) is 10% or less.

Further, on the outermost surface of the coating layer, chromium is present in both the metal chromium and the chromium oxide, thereby preventing the diffusion of copper inside, and from the viewpoint of ensuring the adhesion, although it is preferably metallic chromium, good etching property is obtained. In terms of, it is preferably chromium oxide. Therefore, in order to achieve both the etching property and the adhesion force, it is preferable to set the atomic concentration (%) of the metal chromium in the depth direction (x: unit nm) obtained by the depth direction analysis from the surface by XPS. f ₁ (x), the atomic concentration (%) of the oxide chromium is set to f ₂ (x), and the atomic concentration (%) of the entire chromium is set to f(x)(f(x)=f ₁ (x) +f ₂ (x)), the atomic concentration (%) of nickel is set to g(x), the atomic concentration (%) of copper is h(x), and the atomic concentration (%) of oxygen is set to i ( x), if the atomic concentration (%) of carbon is set to j(x) and the sum of the atomic concentrations of other metals is k(x), then within the interval [0, 1.0], ∫f ₂ (x)dx /(∫f(x)dx+∫g(x)dx+∫h(x)dx+∫i(x)dx+∫j(x)dx+∫k(x)dx) is 20% or more in the interval [1.0, 2.5 Within the range, 0.1≦∫f ₁ (x)dx/∫f ₂ (x)dx≦1.0 is satisfied.

Further, it is preferable that when the heat treatment for hardening of the polyimine is performed, the atomic concentration of the metal chromium in the depth direction (x: unit nm) obtained by analyzing the depth direction from the surface by XPS (%) ) is f ₁ (x), the atomic concentration (%) of the oxide chromium is f ₂ (x), and the atomic concentration (%) of the entire chromium is f(x) (f(x)=f ₁ (x)+f ₂ (x)), the atomic concentration (%) of nickel is set to g(x), the atomic concentration (%) of copper is h(x), and the atomic concentration (%) of oxygen is set. For i(x), the atomic concentration (%) of carbon is set to j(x), and the sum of the atomic concentrations of other metals is k(x), then within the interval [0, 1.0], ∫f ₂ ( x)dx/(∫f(x)dx+∫g(x)dx+∫h(x)dx+∫i(x)dx+∫j(x)dx+∫k(x)dx) is 20% or more in the interval [ Within 1.0, 2.5], 0.1≦∫f ₁ (x)dx/∫f ₂ (x)dx≦1.0 is satisfied.

Further, it is preferably a copper foil for a printed wiring board which is subjected to a heat treatment in which the polyimide is hardened, and a depth direction (x: unit nm) obtained by analysis in the depth direction from the surface by XPS is used. The atomic concentration (%) of the metal chromium is set to f ₁ (x), the atomic concentration (%) of the chromium oxide is f ₂ (x), and the atomic concentration (%) of the entire chromium is set to f(x) ( f(x)=f ₁ (x)+f ₂ (x)), the atomic concentration (%) of nickel is set to g(x), and the atomic concentration (%) of copper is h(x), and oxygen is used. The atomic concentration (%) is i(x), the atomic concentration (%) of carbon is set to j(x), and the sum of the atomic concentrations of other metals is k(x), and the interval is [0, 1.0). ], ∫f ₂ (x)dx/(∫f(x)dx+∫g(x)dx+∫h(x)dx+∫i(x)dx+∫j(x)dx+∫k(x)dx) is 20% or more, within the interval [1.0, 2.5], 0.1≦∫f ₁ (x)dx/∫f ₂ (x)dx≦1.0 is satisfied.

The chromium concentration and the oxygen concentration were respectively calculated from the peak intensities of the Cr2p orbitals and the O1s orbits obtained by analyzing the depth direction from the surface by XPS. Further, the distance in the depth direction (x: unit nm) is the distance calculated from the sputtering rate in terms of SiO ₂ . The chromium concentration is the sum of the oxide chromium concentration and the metal chromium concentration, and can be separated into an oxide chromium concentration and a metal chromium concentration for analysis.

(Preparation method of copper foil of the present invention)

The copper foil for a printed wiring board of the present invention can be formed by a sputtering method. That is, the thickness can be 0.25 to 5.0 nm (preferably 0.3 to 4.0 nm, more preferably 0.5 to 3.0 nm in the intermediate layer) and the thickness is 0.25 to 2.5 nm (preferably 0.4 to 2.0) by sputtering. The Cr layer of nm, more preferably 0.5 to 1.0 nm, is sequentially coated with at least a part of the surface of the copper foil substrate, thereby producing. If such an extremely thin film is laminated by plating, the thickness will be uneven, and the peel strength will be easily lowered after the heat resistance and moisture resistance test.

The thickness herein is not the thickness determined by XPS or TEM described above, but is the thickness derived from the film formation rate of sputtering. The film formation rate under certain sputtering conditions is 0.1 μm (100 nm) or more, which can be measured according to the relationship between the sputtering time and the sputtering thickness. When the film formation speed under the sputtering condition is measured, the sputtering time is set according to the desired thickness. Further, the sputtering can be carried out continuously or in batches, and the coating layer can be uniformly laminated with the thickness specified in the present invention. The sputtering method can be exemplified by a DC magnetron sputtering method.

(Manufacture of printed wiring board)

A printed wiring board (PWB) can be manufactured according to a usual method using the copper foil of the present invention. Hereinafter, a manufacturing example of a printed wiring board will be described.

First, a copper clad laminate is produced by laminating a copper foil and an insulating substrate. The insulating substrate in which the copper foil is laminated is not particularly limited as long as it has characteristics suitable for the printed wiring board. For example, when used for a rigid PWB, a paper substrate phenol resin, a paper substrate epoxy resin, or a synthetic fiber can be used. Cloth substrate epoxy resin, glass cloth-paper composite substrate epoxy resin, glass cloth-glass non-woven composite substrate epoxy resin and glass cloth substrate epoxy resin, etc., when used in FPC, polyester film or Polyimine film and the like.

In the case of the rigid PWB, the bonding method is prepared by impregnating a substrate such as a glass cloth with a resin and curing the resin to a semi-hardened state. This can be carried out by heating and pressurizing the prepreg and the surface of the copper foil having the coating layer.

In the case of a flexible printed wiring board (FPC), an epoxy-based or acrylic-based adhesive may be used to bond the polyimide film or the polyester film to the surface of the copper foil having the coating layer (3 layers). structure). Moreover, the method (two-layer structure) which does not use an adhesive agent is the coating layer which apply|coated on the copper foil by the poly-imine varnish (poly amide varnish) which is a precursor of a polyimine. a surface, and a heating method to iodize the casting method; or coating a thermoplastic polyimide on the polyimide film, superimposing the surface of the copper foil with the coating layer, and heating Pressure lamination method. In the casting method, it is also effective to apply a tackifying coating material such as a thermoplastic polyimide after precoating the polyimide varnish.

The effect of the copper foil of the present invention is remarkably exhibited when the FPC is produced by a casting method. In other words, when the copper foil and the resin are to be bonded together without using an adhesive, the adhesion between the copper foil and the resin is particularly required, and the copper foil of the present invention is excellent in adhesion to the resin, particularly polyimine, so that it can be said that It is suitable for the manufacture of copper-clad laminates using the casting method.

The copper clad laminate of the present invention can be used for various printed wiring boards (PWB), and is not particularly limited. For example, from the viewpoint of the number of layers of the conductor pattern, it can be applied to one-sided PWB, two-sided PWB, and multi-layer PWB (three layers). The above) is applicable to rigid PWB, flexible PWB (FPC), and rigid-flexible PWB from the viewpoint of the type of the insulating substrate material.

The step of manufacturing the printed wiring board from the copper-clad laminate may be carried out by a method known to a person skilled in the art. For example, the etching resist may be applied only to the copper foil surface of the copper-clad laminate as a necessary part of the conductor pattern, and the etching liquid may be used. The copper foil surface is sprayed, whereby the excess copper foil is removed to form a conductor pattern, and then the etching resist is removed and removed to expose the conductor pattern.

[Examples]

The embodiments of the present invention are shown below, but are not intended to limit the present invention in order to better understand the present invention.

(Example 1: Examples 1 to 44)

As the copper foil substrates of Examples 1 to 6 and 8 to 44, a rolled copper foil (C1100 manufactured by Nippon Mining Co., Ltd.) having a thickness of 18 μm was prepared. The surface roughness (Rz) of the rolled copper foil was 0.7 μm. Further, as the copper foil substrate of Example 7, an electrolytic copper foil having a thickness of 18 μm without roughening treatment was prepared. The surface roughness (Rz) of the electrolytic copper foil was 1.5 μm.

The various monomers (a to e) used for sputtering have a purity of 3N. Further, various alloys (f to 1) were produced in the following order. First, an element of the composition shown in Table 1 (alloy component [% by mass] of the sputtering target) is added to electrolytic copper or nickel, and the ingot is cast in a high-frequency melting furnace, and heat is applied at 600 to 900 ° C. Calendering. Further, after homogenization annealing at 500 to 850 ° C for 3 hours, the oxide layer of the surface layer was removed, and a target for sputtering was used.

On one side of the copper foil, reverse sputtering is used to remove a thin oxide film adhering to the surface of the copper foil substrate in advance, and the targets of the a-l and Cr single-layer are sputtered. The intermediate layer and the Cr layer are sequentially formed. The thickness of the coating layer is changed by adjusting the film formation time.

‧ Device: Batch Sputter (ULVAC, Model MNS-6000)

‧ Ultimate vacuum: 1.0×10 ^-5 Pa

‧ Sputtering pressure: 0.2Pa

‧ Reverse sputtering power: 100W

‧ Target:

Middle layer = a ~ l

Cr layer = Cr (purity 3N)

‧ Sputtering power: 50W

‧ Film formation rate: For each target, a film was formed at a fixed time of about 0.2 μm, and the thickness was measured by a three-dimensional measuring device to calculate the sputtering rate per unit time.

For the copper foil provided with the coating layer, the polyimide film was attached in the following order.

(1) For a copper foil of 7 cm × 7 cm, an applicator was used, and a UVarnish-A (polyimine varnish) manufactured by Ube Industries was applied in a dry body of 25 μm.

(2) The resin-attached copper foil obtained in (1) was dried at 130 ° C for 30 minutes under air using a dryer.

(3) The mixture was imidized at a temperature of 350 ° C for 30 minutes in a high-temperature heating furnace in which a nitrogen gas flow rate was set to 10 L/min.

Moreover, unlike the subsequent test of the above polyimide film, as the "heat resistance test", the polyimide film was not coated with the polyimide film, and the polyimide film was heated at a temperature of 350 ° C directly under a nitrogen atmosphere. 2 hours.

<Measurement of adhesion amount>

A film of a 50 mm × 50 mm copper foil surface was dissolved in a solution in which HNO ₃ (2% by weight) and HCl (5% by weight) were mixed, and an ICP emission spectroscopic analyzer (SFC-3100, manufactured by SII NanoTechnology Co., Ltd.) was used. The metal concentration in the solution was quantified, and the amount of metal per unit area (μg/dm ² ) was calculated. Further, in the present invention, the adhesion amount of Cu to other metals when the Cu alloy is used as a target, and the adhesion amount of Cr to other metals when the Cr alloy is used as a target are used under the same conditions on the Ti foil. Analytical value of the membrane.

<Measurement by XPS>

The operating conditions of the XPS when the depth analysis map of the coating layer is produced are shown below.

‧ Device: XPS measuring device (ULVAC-PHI, model 5600MC)

‧ Ultimate vacuum: 3.8×10 ^-7 Pa

‧ X-ray: Monochromatic AlKα or non-monochromatic MgKα, X-ray power is 300W, detection area is 800μm Φ , and the angle between the sample and the detector is 45°

‧ Ion beam: ion type is Ar ⁺ , accelerating voltage is 3kV, scanning area is 3mm × 3mm, sputtering rate is 2.0nm/min (SiO ₂ conversion)

‧ In the measurement results of XPS, the separation of oxide chromium and metal chromium was carried out using the analysis software Multi Pak V7.3.1 manufactured by ULVAC.

‧ The measurement system analyzes the film, which is a heat treatment (350 ° C × 120) which is more severe than the polyethylenimine hardening condition (350 ° C × 30 minutes) when the film is formed by sputtering. In this state, the film after the insulating substrate is peeled off.

<Measurement by TEM>

The measurement conditions of the TEM when the coating layer was observed by TEM are shown below. The thickness shown in the table below is the maximum and minimum values of the thickness between 50 nm for one field of view for the thickness of the entire coating layer captured in the observation field, and the maximum and minimum values of the arbitrarily selected three fields of view are obtained. The value is calculated as a percentage of the maximum and minimum values relative to the maximum value. In addition, in the table, the TEM observation result after "heat-resistance test" is based on the above procedure, and after the polyimide film is coated on the coating layer of the test piece, the test piece is placed in the following high-temperature environment, according to the 90° peeling method. (JIS C 6471 8.1), a TEM image after peeling off the polyimide film from the obtained test piece. In Fig. 1, an observation photograph of the film of Example 17 after film formation by TEM is exemplarily shown. The intermediate layer could not be confirmed according to Fig. 1. The reason is that this portion is a copper alloy layer and cannot be distinguished from the copper foil of the base material. The person confirmed in Fig. 1 is presumed to be a Cr layer. In the present invention, the thickness of the layer which is only defined by the boundary of the base material is measured.

‧ Device: TEM (Hitachi Manufacturing Co., model H9000NAR)

‧ Accelerating voltage: 300kV

‧ Magnification: 300,000 times

‧ Observation field of view: 60nm × 60nm

<Continuity evaluation>

The copper foil laminated with the polyimide in the above manner is placed in a high-temperature environment immediately after laminating (normal) in an air atmosphere at a temperature of 150 ° C for 168 hours (heat resistance), and at a temperature of 40 ° C and relative The peel strength was measured under the conditions of 96 hours (moisture resistance) in a high-humidity environment under an air atmosphere of 95% humidity. The peel strength was measured in accordance with a 90° peeling method (JIS C 6471 8.1).

<etchability evaluation>

A white tape was attached to the coating layer of the copper foil produced as described above, and immersed in an etching liquid (copper chloride dihydrate, ammonium chloride, ammonia water, liquid temperature: 50 ° C) for 7 minutes. Thereafter, the metal component of the etching residue adhering to the tape was quantified by an ICP emission spectroscopic analyzer, and evaluated based on the following criteria.

×: The etching residue is 140 μg/dm ² or more

△: etching residue is 70μg / dm ² or more, less than 140μg / dm ²

○: The etching residue is less than 70 μg/dm ²

(Example 2: Comparative Examples 1 to 28)

On the single side of the rolled copper foil substrate used in Example 1, the thickness of the film described later was changed by changing the sputtering time. For the copper foil provided with the coating layer, the polyimide film was bonded in the same order as in Example 1.

(Example 3: Comparative Example 29)

For the one surface of the rolled copper foil substrate used in Example 1, the Ni-Zn treatment, the chromic acid treatment, and the decane coupling agent treatment disclosed in JP-A-2005-344174 were carried out under the following conditions.

[Ni-Zn plating]

‧ Nickel sulfate 1.5g/l (in terms of Ni)

‧ zinc pyrophosphate 0.5g/l (converted in Zn)

‧ Potassium pyrophosphate 200g/l

‧ pH 9

‧ Bath temperature 40 ° C

‧ Current density 5A/dm ²

[chromic acid treatment]

‧ CrO ₃ 1g/l

‧ Bath temperature 35 ° C

‧ Current density 8A/dm ²

[矽 偶 coupling agent treatment]

‧ γ-aminopropyl triethoxy decane coated with 5g / l solution

(Example 4: Comparative Example 30)

On one side of the rolled copper foil substrate used in Example 1, the Ni plating treatment, the chromic acid treatment, and the decane coupling agent treatment disclosed in JP-A-2007-007937 were carried out under the following conditions.

[Ni plating treatment]

‧ NiSO ₄ /7H ₂ O 300g/l (based on Ni ²⁺ )

‧ H ₃ BO ₃ 40g/l

‧ Bath temperature 25 ° C

‧ Current density 1.0A/dm ²

[chromic acid treatment]

‧ CrO ₃ 1g/l

‧ Bath temperature 25 ° C

‧ Current density 2.0A/dm ²

[矽 偶 coupling agent treatment]

‧ 3-Aminopropyltriethoxydecane coated with 0.3% solution

The measurement results of Examples 1 to 4 are shown in Tables 2 to 7.

Each of Examples 1 to 3 and 6 to 44 had good peel strength and etching property. Further, in Examples 4 and 5, although the etching property was slightly inferior to that of the above examples, the peeling strength was good.

Further, Fig. 2 shows a depth analysis chart obtained by XPS of the copper foil of Example 17 (after heat treatment in which the polyimide varnish is cured). In the Cr layer, an oxide Cr layer is present on the surface layer, and a metal Cr layer is present directly under the layer. Since the concentrations of the oxide Cr and the metal Cr are the largest from the surface layer, it can be said that the two are separated into two layers. In the range of 1 nm from the surface layer, unlike the case of electroplating, the atomic concentration ratio of the oxide Cr exceeds 20%. In other embodiments, the atomic concentration ratio of oxide Cr is also more than 20% in the vicinity of the surface layer. Further, in any of the examples, it was not confirmed that Cu atoms diffused to the surface layer. It is presumed that the effect is to provide an intermediate layer for preventing diffusion of Cu atoms directly under the Cr layer.

In Comparative Example 1, the coating amount of Cr was less than 18 μg/dm ² , and the peel strength was poor.

In Comparative Example 2, the coating amount of Cr was more than 180 μg/dm ² , and the etching property was poor.

In Comparative Examples 3 to 28, the coating amount of Cr was in the range of 18 to 180 μg/dm ² , but various coating strengths and etching properties were caused by the coating amount of various elements used for the intermediate layer.

In each of Comparative Examples 29 and 30, heat resistance and wet peeling strength were poor. According to the depth analysis chart obtained by XPS of the copper foils of Comparative Examples 20 and 30 shown in Figs. 3 and 4, it is presumed that the reason is that the amount of trivalent Cr in the range of 0 to 1 nm from the surface layer is small.

Fig. 1 is a TEM photograph (cross section) of a copper foil (after film formation) of Example 1.

Fig. 2 is a depth analysis chart obtained by XPS of the copper foil of Example 17 (after heat treatment of the polyimine varnish hardening).

Fig. 3 is a depth analysis chart obtained by XPS of the copper foil of Comparative Example 29 (after plating).

Fig. 4 is a depth analysis chart obtained by XPS of the copper foil of Comparative Example 30 (after plating).

Claims (21)

A copper foil for a printed wiring board comprising a copper foil base material and a coating layer covering at least a part of a surface of the copper foil base material, wherein the coating layer is a metal monomer or a layer formed by sequentially laminating from a surface of the copper foil base material The intermediate layer and the Cr layer of the alloy are formed, and Cr is present in the coating layer in an amount of 18 to 180 μg/dm ² , and the depth direction (x: unit nm) obtained by analyzing the depth direction from the surface by XPS is used. The atomic concentration (%) of the metal chromium is set to f ₁ (x), the atomic concentration (%) of the oxide chromium is set to f ₂ (x), and the atomic concentration (%) of the entire chromium is set to f(x). (f(x)=f ₁ (x)+f ₂ (x)), the atomic concentration (%) of nickel is set to g(x), and the atomic concentration (%) of copper is h(x), The atomic concentration (%) of oxygen is i(x), the atomic concentration (%) of carbon is j(x), and the sum of atomic concentrations of other metals is k(x), and the interval is [0, Within 1.0], ∫h(x)dx/(∫f(x)dx+∫g(x)dx+∫h(x)dx+∫i(x)dx+∫j(x)dx+∫k(x)dx) is 10% or less, ∫f ₂ (x)dx/(∫f(x)dx+∫g(x)dx+∫h(x)dx+∫i(x)dx+∫j(x)dx+∫k(x)dx) More than 20%, within the interval [1.0, 2.5], satisfy 0.1≦∫f ₁ (x)dx/∫f ₂ (x)dx≦1.0. The copper foil for a printed wiring board according to the first aspect of the invention, wherein Cr is present in an amount of 30 to 145 μg/dm ² . A copper foil for a printed wiring board according to the second aspect of the invention, wherein Cr is present in an amount of 36 to 90 μg/dm ² . A copper foil for a printed wiring board according to the third aspect of the invention, wherein Cr is present in an amount of 36 to 75 μg/dm ² . The copper foil for a printed wiring board according to the first aspect of the invention, wherein the intermediate layer contains at least one of Ni, Mo, Ti, Zn, Co, V, Sn, Mn, and Cr. The copper foil for a printed wiring board according to the fifth aspect of the invention, wherein the coating layer is an intermediate layer composed of any one of Ni, Mo, Ti, Zn, and Co, and Cr, which are sequentially laminated from the surface of the copper foil substrate. In the intermediate layer, any of Ni, Mo, Ti, Zn, and Co is present in an amount of 15 to 1030 μg/dm ² . The copper foil for a printed wiring board according to the sixth aspect of the invention, wherein Ni is present in an amount of 15 to 440 μg/dm ² in the intermediate layer, and Mo is present in an amount of 25 to 1030 μg/dm ² , and Ti is 15 ~ 140μg / dm ² amount of coating present, Zn to 15 ~ 750μg / dm ² amount of coating is present, or an amount of Co in the coating 25 ~ 1030μg / dm ² of the present. The copper foil for a printed wiring board according to the fifth aspect of the invention, wherein the coating layer is composed of at least two of Ni, Zn, V, Sn, Mn, Cr and Cu which are sequentially laminated from the surface of the copper foil substrate. The intermediate layer and the Cr layer are composed of an alloy, and in the intermediate layer, any two of Ni, Zn, V, Sn, Mn, and Cr are present in an amount of 20 to 1700 μg/dm ² . The copper foil for a printed wiring board according to the eighth aspect of the invention, wherein the intermediate layer is made of a Ni alloy composed of Ni, Zn, V, Sn, Mn, and Cr. The patentable scope of application of the printed wiring board 9 of the copper foil, wherein the intermediate layer is based in a coating amount of 15 ~ 1000μg / dm Ni ² and of 5 ~ 750μg / dm Zn ² of the Ni-Zn alloy, a A Ni-V alloy composed of Ni and V having a total coating amount of 20 to 600 μg/dm ² and a Ni-Sn alloy composed of Ni and Sn having a total coating amount of 18 to 450 μg/dm ² and having a coating amount of 15 to 450 μg. / dm Ni ² of and the Ni-Mn alloy 5 ~ 200μg / dm Mn ² constitutes of a coating amount of 20 ~ 440μg / Ni-Cr alloy dm Ni ^2's and 5 ~ 110μg / dm Cr ² constitutes constituted . The copper foil for a printed wiring board according to the eighth aspect of the invention, wherein the intermediate layer is made of a Cu alloy composed of any one or two of Cu, Zn and Ni. The scope of the patent as item of printed wiring board 11 is a copper foil, wherein the intermediate coating layer system in an amount of Zn is 15 ~ 750μg / dm Cu-Zn alloy of ^2, Ni-coated in an amount of 15 ~ 440μg / dm Cu ² of -Ni alloy, or Ni coating in an amount of 15 ~ 1000μg / dm ² and Zn coating amount of 5 ~ 750μg / dm Cu-Ni -Zn alloy composed of ^2. The copper foil for a printed wiring board according to the first aspect of the invention, wherein when the cross section of the coating layer is observed by a transmission electron microscope, the maximum thickness is 0.5 to 12 nm, and the minimum thickness is 80% or more of the maximum thickness. The copper foil for a printed wiring board according to the first aspect of the invention, wherein, when the heat treatment for the hardening of the polyimine is performed, the depth direction (x: according to the depth direction analysis from the surface by the XPS is used. The atomic concentration (%) of the metal chromium per unit nm is f ₁ (x), the atomic concentration (%) of the oxide chromium is f ₂ (x), and the atomic concentration (%) of the entire chromium is set to f. (x) (f(x)=f ₁ (x)+f ₂ (x)), the atomic concentration (%) of nickel is set to g(x), and the atomic concentration (%) of copper is set to h(x) In the case where the atomic concentration (%) of oxygen is i(x), the atomic concentration (%) of carbon is j(x), and the sum of the atomic concentrations of other metals is k(x), Within [0,1.0], ∫h(x)dx/(∫f(x)dx+∫g(x)dx+∫h(x)dx+∫i(x)dx+∫j(x)dx+∫k(x) Dx) is 10% or less, ∫f ₂ (x)dx/(∫f(x)dx+∫g(x)dx+∫h(x)dx+∫i(x)dx+∫j(x)dx+∫k(x ) dx) is 20% or more, and within the interval [1.0, 2.5], 0.1 ≦∫ f ₁ (x) dx / ∫ f ₂ (x) dx ≦ 1.0 is satisfied. The copper foil for a printed wiring board according to the first aspect of the invention is a copper foil for a printed wiring board which is subjected to a heat treatment for hardening the polyimide, and is obtained by analyzing the depth direction from the surface by using XPS. The atomic concentration (%) of the metal chromium in the depth direction (x: unit nm) is f ₁ (x), and the atomic concentration (%) of the oxide chromium is set to f ₂ (x), and the atomic concentration of the entire chromium ( %) is f(x)(f(x)=f ₁ (x)+f ₂ (x)), the atomic concentration (%) of nickel is set to g(x), and the atomic concentration of copper (%) Let h(x), set the atomic concentration (%) of oxygen to i(x), set the atomic concentration (%) of carbon to j(x), and set the sum of the atomic concentrations of other metals to k(x). ), in the interval [0,1.0], ∫h(x)dx/(∫f(x)dx+∫g(x)dx+∫h(x)dx+∫i(x)dx+∫j(x)dx+ ∫k(x)dx) is 10% or less, ∫f ₂ (x)dx/(∫f(x)dx+∫g(x)dx+∫h(x)dx+∫i(x)dx+∫j(x) Dx+∫k(x)dx) is 20% or more, and satisfies 0.1≦∫f ₁ (x)dx/∫f ₂ (x)dx≦1.0 in the interval [1.0, 2.5]. The copper foil for a printed wiring board according to the first aspect of the invention, wherein the surface of the coating layer after the insulating substrate is peeled off from the coating layer is analyzed for the copper foil for a printed wiring board having the insulating substrate formed through the coating layer If the atomic concentration (%) of the metal chromium in the depth direction (x: unit nm) obtained by analyzing the depth direction from the surface by XPS is f ₁ (x), the atomic concentration of the oxide chromium (%) ) is f ₂ (x), and the atomic concentration (%) of the entire chromium is f(x) (f(x)=f ₁ (x)+f ₂ (x)), and the atomic concentration of nickel (%) ) is set to g(x), the atomic concentration (%) of copper is h(x), the atomic concentration (%) of oxygen is i(x), and the atomic concentration (%) of carbon is set to j ( x), the sum of the atomic concentrations of other metals is k(x), and the distance from the surface layer where the concentration of metallic chromium is the largest is F, which satisfies 0.1≦∫f in the interval [0, F] ₁ (x)dx/∫f ₂ (x)dx≦1.0, and ∫h(x)dx/(∫f(x)dx+∫g(x)dx+∫h(x)dx+∫i(x)dx+∫ j(x)dx+∫k(x)dx) is 10% or less. A copper foil for a printed wiring board according to the first aspect of the invention, wherein the copper foil substrate is a rolled copper foil. A copper foil for a printed wiring board according to the first aspect of the invention, wherein the printed wiring board is a flexible printed wiring board. A copper clad laminate having a copper foil of the first application of the patent scope. A copper clad laminate according to claim 19, which has a copper foil followed by a polyimine structure. A printed wiring board which uses a copper clad laminate of claim 19 or 20 as a material.