JP2002356789A - Copper alloy foil for laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide copper alloy foil for a laminate, in a double-layer printing circuit board in which a resin substrate is formed from varnish containing polyamic acid as the raw material, which has good wettability with the varnish, and can directly be adhered with polyimide without roughening plating treatment and has small roughness in the surface. SOLUTION: The copper alloy foil has a composition containing one or more kinds selected from, by mass, 0.01 to 2.0% Cr and 0.01 to 1.0% Zr, and, if required, further containing one or more kinds selected from Ag, Al, Be, Co, Fe, Mg, Ni, P, Pb, Si, Sn, Ti and Zn by 0.005 to 2.5% in total, and the balance Cu. In the copper alloy, surface roughness is <=2 μm by ten point average surface roughness (Rz), and the thickness of the rust prevention film is controlled to <=5 nm from the surface, so that its wettability with varnish is satisfactory, and 180 deg. peel strength with the film obtained by thermally hardening polyamic acid is >=8.0 N/cm without roughening plating treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper alloy foil used for a laminate for a printed wiring board.

[0002]

2. Description of the Related Art Printed wiring boards are often used in electronic circuits of electronic equipment. Printed wiring boards are roughly classified into hard laminated boards (rigid boards) and flexible laminated boards (flexible boards) depending on the type of resin used as a base material. The flexible substrate is characterized by having flexibility, and is used as a wiring material for a movable part, and also can be stored in a folded state in an electronic device, so that it is also used as a space-saving wiring material. I have. Further, since the substrate itself is thin, it is used as an interposer for a semiconductor package or as an IC tape carrier for a liquid crystal display. In the flexible substrate, polyimide is often used as a resin as a base material, and copper is generally used as a conductive material from the viewpoint of conductivity. The flexible substrate has a three-layer flexible substrate and a two-layer flexible substrate because of its structure. The three-layer flexible substrate has a structure in which a resin film such as polyimide and a copper foil serving as a conductive material are bonded with an adhesive such as an epoxy resin or an acrylic resin. On the other hand, the two-layer flexible substrate has a structure in which a resin such as polyimide and copper as a conductive material are directly bonded.

A printed wiring board is formed by etching a copper foil of a copper-clad laminate to form various wiring patterns, and connecting and mounting electronic components with solder. Because of repeated exposure to high temperatures, heat resistance is required. In recent years, the use of lead-free solder has been widespread due to its effect on the environment. However, since the melting point is higher than that of conventional lead solder, the requirements for heat resistance of flexible substrates have become more stringent. For this reason, the two-layer flexible board uses only heat-resistant polyimide resin as the organic material, so it is more heat-resistant than the three-layer flexible board using an adhesive such as epoxy resin or acrylic resin that has poor heat resistance. It is easy to improve the properties and its usage is increasing.

The main methods for producing a two-layer flexible substrate using a polyimide resin as a base material include a metallizing method, a laminating method, and a casting method. The metallizing method is a method in which a metal such as Cr is thinly deposited on a polyimide film by a sputtering method or the like, and copper, which is a conductive material of a printed wiring board, is formed to a required thickness by a sputtering method or a plating method. Yes, do not use copper foil. Is a method of directly laminating a copper foil as a conductive material of a printed wiring board on a polyimide film. In the casting method, a varnish containing polyamic acid, which is a precursor of a polyimide resin serving as a base material, is applied on a copper foil serving as a conductive material of a printed wiring board, and a polyimide film formed by heating and curing is applied to a resin substrate. How to

In recent years, as electronic devices have become smaller, lighter, and more sophisticated, demands for high-density mounting on printed wiring boards have increased, and finer pitches have been developed by reducing the wiring width and wiring interval of electronic circuits. In. If a copper foil with a large surface roughness or a copper foil with irregularities formed by roughening plating is used as the conductive material, when forming a circuit by etching, copper remains in the resin, etching residue may occur, or etching linearity may be reduced. The circuit width tends to be non-uniform due to a decrease. Therefore, it is preferable that the surface roughness of the copper foil be small in order to make the electronic circuit fine pitch. In electronic devices such as personal computers and mobile communications, the frequency of electric signals is high. When the frequency of electric signals is 1 GHz or more, the effect of the skin effect in which current flows only on the surface of a conductor becomes remarkable, and The influence that the transmission path changes due to the unevenness cannot be ignored. For this reason, attempts have been made to form a metal film on a smoothed polyimide film as in a metallizing method or to reduce the surface roughness of a copper foil used in a laminating method or a casting method.

[0006] Copper foil used as a conductive material of a printed wiring board is classified into an electrolytic copper foil and a rolled copper foil depending on the manufacturing method. Electrodeposited copper foil is produced by electrolytic deposition of copper on a titanium or stainless steel drum from a copper sulfate plating bath.Additional additives were added to the plating bath or the surface roughness was reduced by adjusting the electrolytic deposition conditions. Copper foils, so-called low profile foils, have come to be manufactured. Since the rolled copper foil is manufactured by plastic working with a roll, a smooth surface in which the surface form of the roll is transferred to the surface of the foil can be obtained. Note that a foil generally refers to a thin plate having a thickness of 100 μm or less.

A copper foil used for a printed wiring board has been subjected to a roughening plating process for forming copper particles on the surface of the copper foil by electroplating in order to improve the adhesion to a resin. This is to improve the adhesiveness by the so-called anchor effect, in which irregularities are formed on the surface of the copper foil and the copper foil is cut into the resin to obtain mechanical adhesive strength. It is desirable to bond a copper foil having a small surface roughness, which is not subjected to a plating treatment, to a resin film, and it is necessary to secure an adhesive strength without performing a roughening plating treatment. In addition, in a three-layer flexible substrate, an attempt has been made to apply a silane coupling agent or the like to the copper foil in order to improve the adhesive strength between the copper foil as a metal and the adhesive as an organic substance. However, the manufacturing temperature of the two-layer flexible substrate is 300 ° C to 4 ° C.
Since the temperature is 00 ° C., which is higher than 100 ° C. to 200 ° C. of the three-layer flexible substrate, thermal decomposition of the coupling agent easily occurs, and the adhesiveness is not improved.

[0008] Copper foil materials used as conductive materials include:
Pure copper or a copper alloy containing a small amount of additional elements is used. As the copper foil, which is a conductor, becomes thinner and the circuit width becomes narrower with the finer pitch of electronic circuits, it is required that the DC resistance loss is small and the conductivity is high with respect to the characteristics of the copper foil. ing. Copper is a material with excellent conductivity,
In the above field where conductivity is important, pure copper having a purity of 99.9% or more is generally used. However, since the strength of copper decreases when the purity is increased, the handleability deteriorates when the copper foil becomes thin. Therefore, the strength of the copper foil is preferably large.

In such a situation, the present inventors made a foil from a copper alloy to which a small amount of additional elements was added, based on pure copper having excellent conductivity as disclosed in Japanese Patent Application No. 2001-21986. It has been shown that it is possible to increase the strength of the copper foil and improve the adhesion with the polyimide film without impairing the conductivity. Although the foil obtained by rolling the copper alloy has a small surface roughness, a copper-clad laminate having good adhesion to a polyimide film by a laminating method can be produced by a non-roughening treatment, and excellent high-frequency characteristics were obtained. An attempt was made to produce a two-layer flexible substrate using a polyimide resin as a base material by a casting method using this copper alloy foil. Instead of bonding a polyimide film to the copper alloy foil, a varnish containing a polyamic acid, which is a polyimide precursor, was applied on the copper alloy foil, and then cured by heating to form a polyimide film. As a result, depending on the surface condition of the copper alloy foil, the wettability with the varnish containing polyamic acid may be poor, resulting in unevenness in the amount of the varnish attached, and it is difficult to make the thickness of the polyimide film uniform after heat curing. It has been found.

[0010]

When a two-layer printed wiring board based on a polyimide resin is manufactured by a casting method, the wettability between a copper alloy foil and a varnish containing polyamic acid is improved. It is possible to eliminate the unevenness of the adhesion amount, to make the thickness of the polyimide film after heat curing uniform, and to make the copper foil have a surface roughness of 2 μm or less at Rz of 180 μm without performing any special treatment such as roughening plating. 7. Peel strength.
An object of the present invention is to provide a copper alloy foil for a laminate, which can provide an adhesive strength of 0 N / cm or more.

[0011]

DISCLOSURE OF THE INVENTION The present inventors have investigated the cause of uneven varnish adhesion when a varnish containing polyamic acid is applied to a copper alloy foil. As a result, wetting of the copper alloy foil and the varnish was observed. It was found that the corrosion resistance was poor, and the cause was a rust-preventive film for preventing discoloration of the copper alloy foil. Organic substances such as benzotriazole and imidazole are often used as discoloration inhibitors for pure copper and copper alloys, and by limiting the thickness of these anticorrosive films, wetting with varnishes containing polyamic acid is improved. Thus, the thickness of the polyimide film after heat curing was made uniform. In addition, it was found that the adhesiveness with polyimide when polyamic acid was used as a raw material was improved by a copper alloy to which a small amount of additional element was added, based on pure copper having excellent conductivity, and the surface roughness was 10 points. The average surface roughness (Rz) was 2 μm or less, and sufficient adhesive strength with a film obtained by thermosetting polyamic acid was obtained without performing roughening plating treatment. Specifically, as a result of repeated studies on the wettability of the rust-preventive film and the polyamic acid and the adhesiveness between the heat-cured polyimide and various other additive elements, the present invention shows that (1) the additive element Cr is 0.01 by weight
-20% by mass and 0.01-1.0% by mass of Zr, the balance consisting of copper and unavoidable impurities, and the surface roughness having a ten-point average surface roughness (Rz ) For 2 μm
Hereinafter, by setting the thickness of the rust preventive film to 5 nm or less from the surface, the tensile strength is 600 N / mm ² or more and the conductivity is 5 nm.
It has 0% IACS or more, has good wettability with varnish containing polyamic acid, and has 180 ° peel strength of 8.0 N / cm or more with a film obtained by thermosetting polyamic acid without performing roughening plating treatment. A copper alloy foil for a laminate, characterized in that: (2) The content of the additive element is 0.01% by weight of Cr.
, 2.0% by mass, and 0.01% to 1.0% by mass of Zr.
o, Fe, Mg, Ni, P, Pb, Si, Sn, Ti, Zn
2.5% by mass, the balance consisting of copper and unavoidable impurities, with a surface roughness of 2 μm or less in ten-point average surface roughness (Rz) and a thickness of the rust preventive film of 5 nm or less from the surface. , A tensile strength of 600 N / mm ² or more, and a conductivity of 50
% IACS or more, good wettability with varnish containing polyamic acid, and 180 ° peel strength with a film obtained by thermosetting polyamic acid without performing roughening plating treatment.
A copper alloy foil for a laminated board, which is 0 N / cm or more. Is provided.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The reasons for limiting the surface condition, alloy composition and the like in the present invention to the above will be described. (1) Rust preventive coating: To prevent discoloration of pure copper and copper alloys, it is widely practiced to use a nitrogen-containing organic substance such as benzotriazole or imidazole to form a chelate with copper on the surface to form a rust preventive coating. Have been done. On the other hand, these rust preventive coatings have water repellency and have an effect of impairing wettability with a liquid such as repelling a varnish containing polyamic acid.
For this reason, by limiting the thickness of the rust preventive coating to 5 nm or less from the surface, it becomes possible to make the coating thickness of the varnish uniform, and the thickness of the polyimide obtained by the imidization reaction by heating the polyamic acid. Variation can be reduced. In order to reduce the thickness of the rust preventive film, for example, there is a method of reducing the concentration of the rust preventive agent, and when benzotriazole is used as the rust preventive agent, the concentration is reduced to 500 pp.
m or less. The thickness of the antirust film from the surface can be quantified by measuring it by Auger electron spectroscopy. That is, analysis is performed in the depth direction by Auger electron spectroscopy, and the depth from the surface until the detection intensity of nitrogen, which is an element constituting the rust inhibitor, becomes the same as the background is measured in terms of SiO _2. It is required by

(2) Cr, Zr: Cr and Zr are known to act as catalysts for accelerating polymerization when producing resins. Therefore, it is considered that by adding these to copper to form an alloy foil, the bonding between the metal and the polyimide resin was promoted, and the bonding at the interface was strengthened.
If the amounts of these additives are too small, they do not act sufficiently as a catalyst, so that the metal and the resin are not sufficiently bonded, and the effect of improving the adhesiveness is small. It is necessary to provide a printed wiring board with a 180 ° peel strength of 8.0 N / cm or more that does not hinder practical use. In order to obtain this characteristic, it was found that the amount of addition of at least one of Cr and Zr was 0.01% by mass or more in weight ratio.
On the other hand, when the addition amount is large, coarse crystals are generated due to segregation during casting. A metal material containing coarse crystallites is cracked during hot rolling, resulting in poor hot workability. In addition, as the copper foil, which is a conductor, becomes thinner and the circuit width becomes narrower with the finer pitch of electronic circuits, the DC resistance loss is smaller and the conductivity is higher for the characteristics of copper foil. It has been demanded. In addition, when the amount of addition increases, the conductivity may decrease. The upper limit of the added amount of Cr and Zr at which these problems do not occur is as follows.
0.4% by mass. Further, Zr is more preferably 1.0% by mass and 0.25% by mass. This is because plastic working is easy. Therefore, as the copper alloy foil for a laminate of a printed wiring board, the range of the appropriate addition amount of the alloy component is such that Cr is 0.01 to 2.0% by mass, more preferably 0.01 to 0.4% by weight. % By mass. Zr is
0.01 to 1.0% by mass, more preferably 0.01 to 1.0% by mass
0.25% by mass.

(3) Ag, Al, Be, Co, Fe, M
g, Ni, P, Pb, Si, Sn, Ti and Zn:
Ag, Al, Be, Co, Fe, Mg, Ni, P, P
b, Si, Sn, Ti and Zn are all mainly
It has the effect of increasing the strength of the copper alloy, and one or more additions are made as needed. Its content is 0.
If the amount is less than 005% by mass, desired effects cannot be obtained in the above-mentioned action, while if the total amount exceeds 2.5% by mass, conductivity, solderability and workability are remarkably deteriorated. Therefore, Ag, Al, Be, Co, Fe, Mg, Ni,
The range of the contents of P, Pb, Si, Sn, Ti and Zn was determined to be 0.005 to 2.5% by mass in total.

(4) Surface Roughness: If the surface roughness of the copper foil increases, the impedance increases due to the skin effect in which the electric signal has a frequency of 1 GHz or more and the current flows only on the surface of the conductor. Affect. Therefore, it is necessary to reduce the surface roughness in the application of conductive materials for high-frequency circuits, and as a result of examining the relationship between surface roughness and high-frequency characteristics, it was found that copper alloy foil for printed wiring board laminates has a high surface roughness. It was found that the surface roughness (Rz) should be 2 μm or less. Methods for reducing the surface roughness include techniques for optimizing the production conditions for rolled copper foil and electrolytic copper foil, and chemical polishing or electrolytic polishing of the surface of the copper foil. In general, rolled copper foil can easily reduce the surface roughness, reduce the surface roughness of the work roll of the rolling mill, and reduce the work roll profile transferred to the copper foil. .

The copper alloy foil of the present invention is not limited to the production method, and can be produced, for example, by a method such as an electrolytic copper foil by alloy plating or a rolled copper foil obtained by melting and rolling an alloy. The method by rolling will be described below as an example. A predetermined amount of alloying element is added to the molten pure copper and cast into a mold to form an ingot. In the present invention, Cr, Z
Since an active element such as r is added, it is desirable to perform the treatment in a vacuum or in an inert gas atmosphere to suppress the formation of oxides and the like. It is desirable to use electrolytic copper or oxygen-free copper having a low oxygen content as a raw material. After the ingot is thinned to a certain thickness by hot rolling, skinning is performed, then cold rolling and annealing are repeated, and finally cold rolling is performed to finish the foil. Since the rolling oil is attached to the material after rolling, the material is degreased with acetone, a petroleum-based solvent, or the like.

If an oxide layer is formed by annealing, a problem will occur in a subsequent step. Therefore, it is necessary to perform annealing in a vacuum or an inert gas atmosphere, or to remove the oxide layer after annealing.
For example, to remove an oxide layer by pickling, it is preferable to use sulfuric acid + hydrogen peroxide, nitric acid + hydrogen peroxide, or sulfuric acid + hydrogen peroxide + fluoride.

[0018]

Embodiments of the present invention will be described below. The copper alloy was prepared by melting oxygen-free copper as the main raw material in a high-purity graphite crucible in an Ar atmosphere using a high-frequency vacuum induction melting furnace, and using copper chromium mother alloy and copper zirconium mother alloy as auxiliary raw materials. , Aluminum, silver, copper beryllium master alloy, cobalt, iron, magnesium, manganese, nickel, copper phosphorus master alloy, lead, copper silicon mother alloy, tin, titanium, zinc Was cast in a mold. This method is 30mm thick and 50m wide
A copper alloy ingot having a length of 150 mm and a length of about 2 kg was obtained. This ingot was heated to 900 ° C., rolled to a thickness of 8 mm by hot rolling to remove oxide scale, and then subjected to cold rolling and various heat treatments to a thickness of 35 μm.
Thus, a rolled copper alloy foil of m was obtained.

The copper alloy foil having a thickness of 35 μm obtained by the above method was immersed in acetone to remove the oil content because the rolling oil adhered thereto. This was immersed in an aqueous solution containing 10% by weight of sulfuric acid and 1% by weight of hydrogen peroxide to remove the oxidized layer and the rust preventive film on the surface. For the purpose of investigating the effect of the thickness of the rust-preventive film, it was immersed in an aqueous solution in which the concentration of benzotriazole was adjusted and immediately dried. In addition, no special surface treatment for improving adhesiveness such as rough plating treatment or silane coupling treatment is performed. The copper alloy foil thus produced was fixed on a coating board, and a varnish containing polyamic acid and N-methylpyrrolidone as a solvent was applied with an applicator. After evaporating the solvent in a vacuum dryer, the temperature is finally maintained at 350 ° C. for 10 minutes to heat and cure the polyamic acid to form a polyimide film, a copper-clad laminate comprising two layers of polyimide and a copper alloy. I got Here, the thickness of the polyimide film was about 50 μm.

The “hot rollability”, “surface roughness”, “conductivity”, “tensile strength”,
The "thickness of the rust-preventive film" and the "adhesion strength" with the polyimide film were evaluated by the following methods. (1) Hot rollability: Hot rollability was evaluated by penetrating a hot-rolled material, visually observing the external appearance, and checking for cracks in the material. (2) Surface roughness: The surface roughness was measured in a direction perpendicular to the rolling direction using a stylus type surface roughness meter. Measurement conditions are JI
Based on the method described in SB0601, the ten-point average surface roughness (Rz) was evaluated. (3) Conductivity: The conductivity was determined by measuring the electric resistance at 20 ° C. by a DC four-terminal method using a double bridge. As a measurement sample, a copper foil processed into a foil having a thickness of 35 μm was cut into a width of 12.7 mm. This was measured for electrical resistance with a length of 50 mm between measurements to determine the electrical conductivity. (4) Tensile strength: Tensile strength was measured by a tensile test at room temperature. The measurement sample is a copper foil processed to a thickness of 35 μm, a width of 12.7 mm using a precision cutter,
It was cut into strips having a length of 150 mm. This was measured at a distance between scores of 50 mm and a pulling speed of 50 mm / min. (5) Thickness of rust preventive film: As described above, the depth direction analysis of Auger electron spectroscopy is performed, and from the surface until the detection intensity of nitrogen which is an element constituting the rust preventive agent becomes the same as the background. Was measured in terms of SiO ₂ . (6) Adhesive strength: Adhesive strength is 180 ° peel strength by JI
The measurement was performed according to the method described in SC 5016. Since the strength varies depending on the components of the copper alloy foil, the copper alloy foil was fixed to the tensile tester side using a double-sided tape, and the polyimide was peeled off by bending it in the 180 ° direction.
With a peeling width of 5.0 mm, a pulling speed of 50 mm
/ Min.

Table 1 shows the composition of the copper alloy foil and Table 2 shows the results of evaluating the properties of the copper alloy foil. Oxygen content is 10
ppm or less. In addition, the part shown by "-" in the table indicates that the measurement was not performed. These are Zn
Alternatively, the copper alloy foil containing Pb has a large amount of volatilization of alloy components during the oxygen analysis, and the oxygen content could not be measured accurately. In each case, it is estimated that the oxygen content is 10 ppm or less. The hot workability is indicated by ○ when no cracks occurred after hot rolling, and by x when cracks occurred.
The subsequent test was not carried out for the case where cracks occurred.
In addition, the applicability of the varnish was observed when the varnish containing polyamic acid was applied on the copper foil, and the state of the varnish was observed. . No. of the embodiment. 1 to No. 14 is an embodiment of the copper alloy foil of the present invention. As shown in Table 1, the copper alloy foil of the present invention has a conductivity of 50% IACS or more, a tensile strength of 600 N / mm ² or more, and a 180 ° peel strength of 8.0 N when polyimide is bonded. / Cm or more. It can be seen that it has excellent conductivity and handling properties, and has high adhesive strength. In addition, no crack occurred during hot rolling.

[0022]

[Table 1]

[0023]

[Table 2]

On the other hand, in Comparative Example No. 1 shown in Table 1, Reference numeral 15 denotes a rolled copper foil to which the alloy component of the present invention has not been added. An ingot obtained by melting and casting oxygen-free copper in an Ar atmosphere was processed into a foil and bonded to polyimide. Since the material is pure copper, the conductivity is high, but the 180 ° peel strength is 7.5N.
/ Cm, a sufficient adhesive strength has not been obtained, and peeling may occur when the printed wiring board is used.

No. of Comparative Example 16 and No. 17
Was processed into a foil in the same manner as in the example, except that only one of each of Cr and Zr was added. Since the concentration of Cr and Zr was less than 0.01% by weight, the effect of improving the strength was not sufficient, and the tensile strength was as small as less than 600 N / mm ² .

No. of Comparative Example 18 added Cr,
Since its concentration exceeds 2.0% by mass in weight ratio, coarse crystals of Cr are formed during casting, cracks are generated during hot rolling, and hot workability is poor. N of Comparative Example
o. In No. 19, only Zr was added, but since the concentration exceeded 1.0% by mass, cracks similarly occurred during hot rolling. For this reason, No. 18 and No. 1
No. 9 could not carry out subsequent tests.

No. of Comparative Example 20 added Ti,
Since its concentration exceeds 2.5% by mass in terms of weight ratio, the conductivity is low and it is not suitable as a conductive material for printed wiring boards.

No. of Comparative Example 21 and No. 21. 22
Is No. of the embodiment. Using the alloy foil of No. 7, a treatment of immersion in an aqueous solution in which the concentration of benzotriazole was adjusted was performed. As a result, when the rust-preventive film becomes thick, the wettability with the varnish containing polyamic acid deteriorates, cissing of the varnish is recognized, and a uniform polyimide film cannot be obtained.
The 80 ° peel strength could not be measured.

[0029]

When the copper alloy foil of the present invention is used for a printed wiring board laminate having a polyimide as a base material and a varnish containing polyamic acid as a raw material, excellent adhesion to a resin is obtained even if the surface roughness is small. It has high conductivity and high conductivity. This is suitable for use as a conductive material for electronic circuits that require fine wiring.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22C 9/06 C22C 9/06 9/08 9/08 9/10 9/10 H05K 1/09 H05K 1 / 09 A 3/00 3/00 R 3/38 3/38 B F term (reference) 4E351 AA01 AA02 AA14 AA15 AA17 BB30 CC19 CC31 DD04 DD17 DD54 DD55 GG01 GG02 4K053 PA06 QA06 RA13 RA15 SA06 5E343 AA02 AA16 AA36 BB24 BB38 BB38 BB67 GG02

Claims (2)

[Claims] 1. The additive element contains, by weight, at least one of the following components: 0.01 to 2.0% by mass of Cr and 0.01 to 1.0% by mass of Zr; Consists of copper and unavoidable impurities, and has a surface roughness of 10-point average surface roughness (Rz)
2 μm or less, and the thickness of the rust preventive film is 5 nm or less from the surface, so that it has a tensile strength of 600 N / mm ² or more, a conductivity of 50% IACS or more, and wettability with a varnish containing polyamic acid. And a 180 ° peel strength of 8.0 N / cm or more with a film obtained by thermosetting polyamic acid without performing roughening plating treatment, is 8.0 N / cm or more. 2. The composition according to claim 1, wherein the additive element contains at least one of the following components by weight: 0.01 to 2.0% by mass of Cr and 0.01 to 1.0% by mass of Zr. , Al, B
e, Co, Fe, Mg, Ni, P, Pb, Si, Sn,
One or more of each component of Ti and Zn is 0.00
5 to 2.5% by mass, the balance consisting of copper and unavoidable impurities, and having a surface roughness of 2 μm as a ten-point average surface roughness (Rz).
m or less, and the thickness of the rust preventive film is 5 nm or less from the surface, so that the wettability with a varnish containing a polyamic acid having a tensile strength of at least 600 N / mm ² and a conductivity of at least 50% IACS is obtained. A copper alloy foil for a laminate, characterized by having a 180 ° peel strength of at least 8.0 N / cm with a film obtained by thermosetting polyamic acid without performing roughening plating.