TW201325336A - Copper foil for printed circuit - Google Patents

Abstract

Provided is a roughened copper foil that has a black surface and good etching properties. This copper foil for a printed circuit has a non-black roughened layer and a nickel-tungsten alloy plating layer formed in this order on at least one of the surfaces of the copper foil, and the amount of nickel in the nickel-tungsten alloy plating layer is 2,000 [mu]g/dm2 or more.

Description

Copper foil for printed circuit

The present invention relates to a copper foil for a printed circuit, and is related to, for example, a copper foil for a printed circuit suitable for a fine pattern printed circuit and a FPC (Flexible Printed Circuit) for a magnetic head.

Copper and copper alloy foils (hereinafter referred to as copper foils) contribute greatly to the development of electrical and electronic related industries, and in particular, they are indispensable as printed circuit materials. In general, a copper foil for a printed circuit is laminated on an insulating substrate such as a synthetic resin sheet or a film via an adhesive or a high temperature and high pressure without using an adhesive, thereby producing a copper clad laminate, and then forming a desired copper sheet. After the necessary circuit is printed by the resist coating and exposure steps, an etching process for removing excess portions is performed.

Finally, the required components are soldered to form various printed circuit boards for electronic devices.

In the copper clad laminate, one of the important properties of the insulating substrate and the conductive material is one of the important characteristics, and in order to improve the adhesion to the insulating substrate, a surface treatment called roughening is performed on the surface of the copper foil to form irregularities. For example, there is a method in which, on the M surface (rough surface) of the electrolytic copper foil, a copper sulfate acid plating bath is used to electrodeposit a plurality of copper into a dendritic or small spherical shape to form fine irregularities, and is improved by the grasping effect. Follow-up.

In addition, as a technique for the roughening treatment of the electrodeposited copper particles, there is known a technique in which, for example, Japanese Patent Laid-Open No. Hei 4-96395 (Patent Document 1) and Japanese Patent Laid-Open No. Hei 10-18075 (Patent Document 2) are known. It is described that the surface of the copper foil is subjected to a roughening treatment using a copper-cobalt-nickel alloy.

[Patent Document 1] Japanese Patent Laid-Open No. Hei 4-96395

[Patent Document 2] Japanese Patent Laid-Open No. 10-18075

Another important characteristic required for the copper foil for printed circuits is black. First, black has the advantage of high alignment accuracy and high heat absorption rate. In the process of manufacturing a printed circuit board, an IC, a resistor, a capacitor, and the like are mounted by an automatic step. At this time, the circuit is read by the sensor and chip mounted. At this time, the alignment of the roughened surface may be performed by a film such as Kapton. Moreover, the positioning at the time of forming the through hole is also the same. Further, the closer the processing surface is to black, the better the absorption of light, and thus the accuracy of positioning becomes high.

Second, when manufacturing a printed circuit board, in many cases, the copper foil and the insulating substrate are heated while being solidified. In this case, when heating is performed by using a long wave such as far infrared ray or infrared ray, the heating efficiency of the black color of the treated surface is better.

In this respect, in the conventional roughening treatment using electrodeposited copper particles, it is not suitable because the surface becomes red. Further, according to the roughening treatment by the copper-cobalt-nickel alloy described in Patent Document 1 or Patent Document 2, although a black surface can be obtained, it is formed of copper-cobalt-plated on the surface of the copper foil. The shape of the roughened particles composed of the nickel alloy is dendritic, and thus there is a problem that it is peeled off from the upper portion or the root portion of the branch, and is generally called a falling powder phenomenon. The powder falling phenomenon is difficult to solve, despite the copper-cobalt-nickel alloy The gold roughening treatment layer is excellent in adhesion to the resin layer and excellent in heat resistance. However, the particles are liable to fall off due to external force, and peeling due to "friction" during the treatment is caused by the peeling powder. The contamination caused by the roller and the etching residue due to the peeling powder.

Further, from the viewpoint of forming a fine pattern, it is also required that there is no etching residue after etching.

Accordingly, an object of the present invention is to provide a roughened copper foil having a black surface and excellent etchability, and it is preferable to provide a roughened copper foil having improved problems in powder falling. Further, a further object of the present invention is to provide a copper clad laminate having such a roughened copper foil.

In one aspect of the invention, a copper foil for a printed circuit is formed with a non-black roughening treatment layer and a nickel-tungsten alloy plating layer on at least one surface of the copper foil, the nickel-tungsten alloy plating nickel The amount is 2000 μg/dm ² or more.

In one embodiment of the copper foil for a printed circuit of the present invention, the nickel-tungsten alloy plating layer has a nickel content of 2000 to 5000 μg/dm ² .

In another embodiment of the copper foil for printed circuit of the present invention, the heat-resistant layer is formed on the nickel-tungsten alloy plating layer.

In still another embodiment of the copper foil for a printed circuit of the present invention, a rustproof layer is formed on the nickel-tungsten alloy plating layer or the heat-resistant layer formed on the nickel-tungsten alloy plating layer.

In still another embodiment of the copper foil for a printed circuit of the present invention, the roughening layer is formed on a primary particle layer of copper, and a secondary particle layer of a copper-cobalt-nickel alloy is formed on the primary particle layer. Founder.

In still another embodiment of the copper foil for a printed circuit of the present invention, the average particle diameter of the primary particle layer of copper is 0.25 to 0.45 μm, and the average particle diameter of the secondary particle layer composed of a copper-cobalt-nickel alloy It is 0.05~0.25μm.

In still another embodiment of the copper foil for a printed circuit of the present invention, the primary particle layer and the secondary particle layer are a plating layer.

In another aspect, the present invention provides a copper clad laminate comprising the copper foil for a printed circuit of the present invention.

In still another aspect, the present invention is a printed circuit board using the copper clad laminate of the present invention as a material.

According to the present invention, it is possible to provide a roughened copper foil having a black surface and excellent etching properties, and it is preferable to provide a roughened copper foil having an improved problem of powder falling.

In one embodiment of the copper foil for a printed circuit of the present invention, a roughened layer and a nickel-tungsten alloy plating layer are formed on at least one surface of the copper foil in this order. For example, a black surface can be obtained by forming a nickel-tungsten alloy plating layer on the non-black roughening treatment layer.

<Coarsening layer>

The copper foil used in the present invention may be any one of an electrolytic copper foil or a rolled copper foil. Usually, the rough surface of the copper foil and the insulating substrate such as a resin is used to enhance the peeling strength of the copper foil after lamination, and the surface of the copper foil after degreasing is subjected to a "tumor" shape. The roughening treatment of the deposit. The M surface of the electrolytic copper foil has irregularities at the time of production, and the convex portion of the electrolytic copper foil is reinforced by the roughening treatment to further increase the unevenness.

In the rolled copper foil and the electrolytic copper foil, the contents of the treatment are sometimes slightly different. In the present invention, such pretreatment and final treatment are also included, and a well-known process relating to roughening of copper foil is included as needed, and is referred to as "roughening treatment".

As a method of roughening treatment, for example, a method of forming an electrodeposited copper particle layer on the surface of a copper foil can be mentioned. Further, as a preferred method for improving the peel strength, there is a method of forming a copper-cobalt-nickel alloy plating layer on the surface of a copper foil. Among them, if it is a separate copper-cobalt-nickel alloy plating layer, the problem of remaining powder is left. Therefore, the inventors have found that a method of forming an electrodeposited copper particle layer as a primary particle layer and forming a secondary particle layer of a copper-cobalt-nickel alloy thereon is preferable. According to the preferred method, there is no peeling due to "friction" in the treatment, contamination of the roll due to the peeling powder, and etching residue due to the peeling powder, that is, a kind of suppression can be called falling A copper foil for a printed circuit which has a phenomenon of powder and uneven handling, and which can improve peeling strength and can improve heat resistance.

The roughened layer obtained by forming the electrodeposited copper particle layer as a primary particle layer and forming a secondary particle layer of a copper-cobalt-nickel alloy thereon is described in detail.

When the copper-cobalt-nickel alloy plating layer is formed only on the copper foil, since it is dendritic, the problem of falling powder is generated as described above.

A micrograph of the surface of a copper foil on which a copper-cobalt-nickel alloy plating layer is formed on a copper foil is shown in Fig. 3. As shown in Fig. 3, fine particles grown into dendrites can be seen. In general, the fine particles grown in the dendritic shape shown in Fig. 3 are produced at a high current density.

When the treatment has been carried out at such a high current density, since the nucleation of the particles in the initial electrodeposition is suppressed, a new particle nucleus is formed at the tip end of the particle, and therefore, the particle gradually grows into an elongated dendritic shape.

The case where the powder is dropped in the case where the copper-cobalt-nickel alloy plating layer shown in Fig. 3 is formed is shown in the conceptual explanatory diagram of Fig. 1. The reason for this falling powder is that dendritic fine particles are generated on the copper foil as described above, but the dendritic particles are liable to be partially broken by the external force and fall off from the root portion. The fine dendritic particles cause peeling due to "friction" during the treatment, contamination of the roll due to the peeling powder, and generation of etching residue due to the peeling powder.

On the other hand, in the case where the electrodeposited copper particle layer is used as a primary particle layer and a roughened layer of a copper-cobalt-nickel alloy secondary particle layer is formed thereon, as shown in FIG. 2, A secondary particle layer having a particle diameter smaller than that of the primary particle layer having a large particle diameter is formed. Therefore, both the peel strength and the powder fall prevention can be ensured. A photomicrograph of this case is disclosed in FIG. From the viewpoint of preventing powder falling, it is desirable that the average particle diameter of the primary particle layer is larger than the average particle diameter of the secondary particle layer. Further, according to the examples shown below, the optimum conditions for preventing the falling powder are such that the average particle diameter of the primary particle layer is 0.25 to 0.45 μm, and the average of the secondary particle layers composed of the copper-cobalt-nickel alloy is obtained. The particle size is 0.05 to 0.25 μm, typically 0.1 to 0.25 μm.

The primary particle layer and the secondary particle layer are formed by a plating layer. The secondary particles are characterized by one or a plurality of dendritic particles grown on the primary particles.

As described above, the average particle diameter of the secondary particle layer is set to be as small as 0.05 to 0.25 μm, but the particle diameter may be referred to as the height of the particles. That is, it can be said that suppressing the height of the secondary particles and suppressing the peeling of the particles (falling powder) is one of the features of the invention of the present application.

The bonding strength between the copper foil for a printed circuit and the insulating substrate having the roughened layer formed of the primary particle layer and the secondary particle layer formed on the surface can be 0.80 kg/cm or more, and the subsequent strength can reach 0.90 kg. /cm or more.

(plating conditions of primary particles of copper)

An example of plating conditions of primary particles of copper is as follows.

Further, the plating conditions are only a preferred example, and the primary particles of copper are formed on the copper foil and the average particle diameter acts to prevent falling powder. Therefore, as long as the average particle diameter is within the range of the present invention, plating conditions other than those shown below may be employed. The invention of the present application includes such conditions.

Liquid composition: copper 10~20g/L, sulfuric acid 50~100g/L

Liquid temperature: 25~50°C

Current density: 1~58A/dm ²

Coulomb amount: 4~81As/dm ²

(plating conditions of secondary particles)

Further, similarly to the above, the plating conditions are only a preferred example, and the secondary particles are formed on the primary particles, and the average particle diameter acts to prevent the falling powder. Therefore, as long as the average particle diameter is within the range of the present invention, plating conditions other than those shown below may be employed. The invention of the present application includes such conditions.

Liquid composition: copper 10~20g/L, nickel 5~15g/L, cobalt 5~15g/L

pH: 2~3

Liquid temperature: 30~50°C

Current density: 24~50A/dm ²

Coulomb amount: 34~48As/dm ²

When the Ni adhesion amount is less than 50 μg/dm ² , the heat resistance is deteriorated. On the other hand, when the Ni adhesion amount exceeds 500 μg/dm ² , the etching property is lowered. That is, etching residue is generated, and although it is not impossible to perform etching, it becomes difficult to form a fine pattern. A preferred Co adhesion amount is 500 to 2000 μg/dm ² , and a preferred nickel adhesion amount is 50 to 300 μg/dm ² .

From the above, it can be said that preferably copper - cobalt - nickel-alloy-based deposition amount of 10 ~ 30mg / dm ² of copper -100 ~ 3000μg / dm ² of cobalt -50 ~ 500μg / dm ² of nickel. The adhesion amount of the ternary alloy layer is only an ideal condition, and does not negate the range exceeding the amount.

<black layer>

A nickel-tungsten alloy plating layer is formed on the roughened layer to contribute to blackening of the surface of the copper foil. For example, the roughening layer composed of the primary particle layer and the secondary particle layer is gray, and the primary particle layer is made of copper, and the secondary particle layer is made of a copper-cobalt-nickel alloy. However, black is obtained by forming a nickel-tungsten alloy layer on the surface of the roughened layer. The reason why the binary alloy of nickel and tungsten is formed is that the blackening effect can be obtained by nickel, and the etching property can be ensured by tungsten. Respect of the nickel - tungsten alloy coating, blackening on the viewpoint, preferably nickel, deposition amount of 2000μg / dm ² or more, more preferably 3000μg / dm ² or more. In the nickel-tungsten alloy plating layer, the upper limit of the adhesion amount of nickel is not particularly required from the viewpoint of blackening, but if the amount of adhesion is too large, the economic efficiency is also lowered. For example, it may be 15,000 μg/dm ² or less, or 10000 μg/dm. ² or less, or 8000 μg/dm ² or less, or 7000 μg/dm ² or less. Further, nickel - nickel plating layer of the excess of tungsten alloy deposition amount, the peeling strength begins to decrease, and therefore is preferably ² or less 5500μg / dm, more preferably 5000μg / dm ² or less. Tungsten can coexist in the alloy plating.

(plating conditions for forming a blackening layer)

Representative plating bath compositions and plating conditions are as follows.

Liquid composition: nickel 10~40g/L, tungsten 10~30mg/L

pH: 3~4

Liquid temperature: 35~45°C

Current density: 2~3A/dm ²

Coulomb amount: 15~25As/dm ²

<heat-resistant layer>

A heat-resistant layer, particularly a heat-resistant layer of a zinc-nickel alloy plating layer, may also be formed on the above nickel-tungsten alloy plating layer. The processing performed in the manufacturing steps of the printed circuit further becomes high temperature, and heat is generated during use of the machine after it becomes a product. For example, in a so-called two-layer material in which a copper foil is bonded to a resin by thermocompression bonding, heat of 300 ° C or more is applied at the time of bonding. That is, in such a case, it is also necessary to prevent a decrease in the bonding force between the copper foil and the resin substrate, and the galvanization-nickel alloy is effective.

Preferably, the total amount of the zinc-nickel alloy plating layer is 150 to 500 μg/dm ² , and the ratio of nickel is 16 to 40% by mass. Thereby, it is possible to provide an effect of providing a heat-resistant rust-preventing layer and suppressing an etchant used in soft etching (for example, H ₂ SO ₄ : 10 wt %, H ₂ O ₂ : 2 wt% of an etching aqueous solution). It penetrates and prevents the joint strength of the circuit from being weakened by corrosion. If the total amount of the zinc-nickel alloy plating layer is less than 150 μg/dm ² , the heat resistance is lowered and it becomes difficult to function as a heat-resistant layer. If the total amount of the zinc-nickel alloy plating layer exceeds 500 μg/dm ² , it is resistant. The tendency of hydrochloric acid to deteriorate. In addition, when the lower limit of the nickel ratio in the alloy layer is less than 16% by mass, the amount of penetration during soft etching exceeds 9 μm, which is not preferable. Regarding the upper limit of the nickel ratio of 40% by mass, the technical limit value of the zinc-nickel alloy plating layer can be formed.

(Formation conditions for forming a heat-resistant layer)

Representative plating bath compositions and plating conditions are as follows.

Liquid composition: nickel 2~30g/L, zinc 2~30g/L

pH: 3~4

Liquid temperature: 30~50°C

Current density: 1~2A/dm ²

Coulomb amount: 1~2As/dm ²

<rustproof layer>

Further, a rustproof layer, particularly a rust preventive layer of a chromate layer, may be formed on the nickel-tungsten alloy plating layer or on the heat-resistant layer formed on the nickel-tungsten alloy plating layer. In the present invention, the preferred rust-preventing treatment is a chromium oxide treatment alone or a mixture of chromium oxide and zinc/zinc oxide. The coating treatment of a mixture of chromium oxide and zinc/zinc oxide is carried out by coating a zinc consisting of zinc or zinc oxide with chromium oxide by electroplating using a plating bath containing zinc or zinc oxide and chromate. -Chromium-based mixture Anti-rust layer.

As the plating bath, at least one of a dichromate such as K ₂ Cr ₂ O ₇ or Na ₂ Cr ₂ O ₇ or CrO ₃ or the like, for example, ZnO or ZnSO _{4 is} typically used. A mixed aqueous solution of at least one of a water-soluble zinc salt such as 7H ₂ O and an alkali metal hydroxide. Representative plating bath compositions and electrolysis conditions are as follows. The conditions for impregnating the chromate treatment are shown below, but may also be an electrolytic chromate treatment.

(Formation conditions for forming a rustproof layer)

Liquid composition: potassium dichromate 1~10g/L, zinc 0~5g/L

pH: 3~4

Liquid temperature: 50~60°C

Current density: 0~2A/dm ² (for impregnation chromate treatment)

Coulomb amount: 0~2As/dm ² (for impregnation chromate treatment)

<Hydrane treatment>

Finally, if necessary, for the purpose of improving the adhesion between the copper foil and the resin substrate, the decane treatment of the decane coupling agent may be applied to at least the roughened surface of the rustproof layer. The decane coupling agent to be used for the decane treatment may, for example, be an olefin decane, an epoxy decane, an acrylic decane, an amine decane or a decyl decane, and may be appropriately selected and used.

The coating method may be any one of spraying by spraying of a decane coupling agent solution, coating by a coater, dipping, casting, or the like. For example, Japanese Patent Publication No. Sho 60-15654 discloses a chromate treatment on a rough surface side of a copper foil and then a decane coupling agent treatment to improve the adhesion between the copper foil and the resin substrate. For details, please refer to this document. after that, If necessary, annealing treatment may be performed for the purpose of improving the ductility of the copper foil.

The copper foil obtained in this manner has excellent heat-resistant peel strength, oxidation resistance, and hydrochloric acid resistance. Further, a printed circuit having a circuit width of 150 μm or less can be etched by a CuCl ₂ etching solution, and alkaline etching can also be performed. Further, it is possible to suppress penetration into the edge portion of the circuit during soft etching.

In the soft etching liquid, an aqueous solution of H ₂ SO ₄ : 10 wt%, H ₂ O ₂ : 2 wt% can be used. The processing time and temperature can be adjusted arbitrarily.

As the alkaline etching solution, for example, a solution such as NH ₄ OH: 6 mol/liter, NH ₄ Cl: 5 mol/liter, CuCl ₂ : 2 mol/liter (temperature: 50 ° C) is known.

[Examples]

Hereinafter, description will be made based on examples and comparative examples. Furthermore, this embodiment is merely an example, and the present invention is not limited to this example. That is, other aspects or modifications included in the present invention are included. Further, as the original foil of the following examples, a standard rolled copper foil TPC was used.

(Example 1)

In the condition range shown below, a primary particle layer (Cu) and a secondary particle layer (copper-cobalt-nickel alloy) were formed on the rolled copper foil. As a result, a primary particle diameter of 0.40 μm and a secondary particle diameter of 0.15 μm were obtained. The average particle diameters of the primary particle layer and the secondary particle layer were measured by an SEM image and by a dicing method. The average particle diameter of the primary particle layer is measured before the formation of the secondary particle layer.

The bath composition and plating conditions used are as follows.

[Bath composition and plating conditions] (A) Formation of primary particle layer (Cu plating)

Liquid composition: copper 15g / L, sulfuric acid 75g / L

Liquid temperature: 35 ° C

Current density: 2~58A/dm ²

Coulomb amount: 8~81As/dm ²

(B) Formation of secondary particle layer (Cu-Co-Ni alloy plating)

Liquid composition: copper 15g / L, nickel 8g / L, cobalt 8g / L

pH: 2

Liquid temperature: 40 ° C

Current density: 24~31A/dm ²

Coulomb amount: 34~44As/dm ²

Next, a nickel-tungsten alloy plating layer was further formed on the secondary particle layer (after the roughening treatment) under the following conditions.

(Formation conditions for forming a nickel-tungsten alloy plating layer)

Liquid composition: nickel 25g / L, tungsten 20mg / L

pH: 3.6

Liquid temperature: 40 ° C

Furthermore, the current density and coulomb amount are shown in Table 1.

The results are shown in Table 1. In the case where the amount of nickel in the nickel-tungsten alloy plating layer was 2000 μg/dm ² or more, black was obtained, and the etching property was also good.

Further, in the case where a nickel plating layer is formed on the secondary particle layer under the above conditions as a liquid composition containing no tungsten, the number (No. A) is black, but compared with the case of forming a nickel-tungsten alloy plating layer, the result is Poor etchability.

‧ Use color samples to determine if it is black.

‧ Peel strength was measured by FR-4 substrate 10 mm circuit test piece.

‧ The adhesion amount of Ni in the nickel-tungsten alloy plating layer is measured by ICP for the plating layer solution.

‧ The evaluation of the falling powder was carried out by the tape transfer method, and the case where the transfer of the roughened particles was not present in the tape was marked as ◎, and the case where the slightly roughened particles were partially transferred was recorded as ○, The case where the transfer of the roughened particles was observed as a whole (although slight but throughout the entire surface) was recorded as ×.

‧ Etchability is evaluated by the presence or absence of residue dissolved in an alkaline etching solution.

(Example 2)

Next, a primary particle layer (Cu) and a secondary particle layer (copper-cobalt-nickel alloy) were formed under the same conditions as in Example 1. Further, as shown in Table 2, the current density and the coulomb amount were changed to form a nickel-tungsten alloy plating layer.

The results are shown in Table 2. A decrease in peel strength was observed in the case where the Ni adhesion amount of the nickel-tungsten alloy plating layer exceeded 5000 μg/dm ² .

(Example 3)

Forming primary particles in the rolled copper foil within the conditions shown below Layer (Cu), secondary particle layer (copper-cobalt-nickel alloy). The bath composition and plating conditions used are as follows, and the primary particle current conditions and the secondary particle current conditions are shown in Table 3. Among them, No. 14 (Cu layer) and No. 15 (copper-cobalt-nickel alloy plating layer) are reference examples of the previous roughening treatment.

[Bath composition and plating conditions] (A) Formation of primary particle layer (Cu plating)

Liquid composition: copper 15g / L, sulfuric acid 75g / L

Liquid temperature: 35 ° C

(B) Formation of secondary particle layer (Cu-Co-Ni alloy plating)

Liquid composition: copper 15g / L, nickel 8g / L, cobalt 8g / L

pH: 2

Liquid temperature: 40 ° C

A nickel-tungsten alloy plating layer on the above secondary particle layer (after roughening treatment) was formed under the following conditions.

(Formation conditions for forming a nickel-tungsten alloy plating layer)

Liquid composition: nickel 25g / L, tungsten 20mg / L

pH: 3.6

Liquid temperature: 40 ° C

Current density: 2A/dm ²

Coulomb amount: 20As/dm ²

Further, in No. 14, 15, and 16, a nickel-tungsten alloy plating layer was not formed, but a Co-Ni alloy plating layer was formed.

The results are shown in Table 3, and a black surface was obtained by forming a nickel-tungsten alloy plating layer. On the other hand, the No. 16 sheet having a Co-Ni alloy plating layer The face is gray. Further, in No. 17, 18, and 19 in which the secondary particle layer is too large, there is a powder falling phenomenon, which is not preferable.

As described above, when a secondary particle layer (roughening treatment) composed of a copper-plated cobalt-nickel alloy is formed, it is possible to prevent the roughened particles formed into dendrites from peeling off from the surface of the copper foil, which is generally called falling. Excellent effect of the powder phenomenon.

Fig. 1 is a conceptual explanatory view showing a state of falling powder in a case where a roughening treatment by a copper-cobalt-nickel alloy is performed on a conventional copper foil.

2 is a conceptual explanatory view of a roughened layer formed by forming a primary particle layer of copper on a copper foil and forming a secondary particle layer made of a copper-cobalt-nickel alloy on the primary particle layer.

Fig. 3 is a photomicrograph of the surface in the case where a roughening treatment by a copper-cobalt-nickel alloy is performed on a copper foil.

Fig. 4 is a photomicrograph of a layer of a copper foil-treated surface on which a primary particle layer is formed in advance on a copper foil, and a secondary particle layer composed of a copper-cobalt-nickel alloy is formed on the primary particle layer.

Claims (10)

A copper foil for a printed circuit in which a non-black roughening treatment layer and a nickel-tungsten alloy plating layer are formed on at least one surface of the copper foil, and the nickel-tungsten alloy plating layer has a nickel content of 2000 μg/dm ² or more. The copper foil for a printed circuit according to the first aspect of the invention, wherein the nickel-tungsten alloy plating layer has a nickel content of 2000 to 5000 μg/dm ² . A copper foil for a printed circuit according to claim 1 or 2, wherein a heat-resistant layer is formed on the nickel-tungsten alloy plating layer. A copper foil for a printed circuit according to claim 1 or 2, wherein a rustproof layer is formed on the nickel-tungsten alloy plating layer or on the heat-resistant layer formed on the nickel-tungsten alloy plating layer. The copper foil for a printed circuit according to claim 1 or 2, wherein the roughening layer is formed on a primary particle layer of copper, and a secondary particle of a copper-cobalt-nickel alloy is formed on the primary particle layer. Layered. The copper foil for a printed circuit according to claim 5, wherein the primary particle layer of the copper has an average particle diameter of 0.25 to 0.45 μm, and the average particle diameter of the secondary particle layer composed of the copper-cobalt-nickel alloy is 0.05~0.25μm. The copper foil for printed circuit of claim 5, wherein the primary particle layer and the secondary particle layer are electroplated layers. The copper foil for printed circuit of claim 6, wherein the primary particle layer and the secondary particle layer are electroplated layers. A copper-clad laminate comprising the copper foil for a printed circuit according to any one of claims 1 to 8. A printed circuit board which is covered by the ninth application patent The copper laminate is made of material.