JP2011210984A - Copper foil for printed wiring board and layered body which have superior heating discoloration resistance and etching property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper foil for a printed wiring board and a layered body which have superior heating discoloration resistance and etching properties.SOLUTION: The copper foil for the printed wiring board includes a copper foil base material and a coating layer which covers at least a part of a surface of the copper foil base material and includes at least one or more kinds among Au, Pt and Pd, the coating layer being composed of noble metal particles of one or more kinds among Au, Pt and Pd and a silane coupling agent covering the noble metal particles.

Description

  The present invention relates to a copper foil and a laminate for a printed wiring board excellent in heat discoloration resistance and etching properties, and particularly to a copper foil and a laminate for a flexible printed wiring board.

  Printed wiring boards have made great progress over the last half century and are now used in almost all electronic devices. In recent years, with the increasing needs for miniaturization and higher performance of electronic devices, higher density mounting of components and higher frequency of signals have progressed, and conductor patterns have become finer (fine pitch) and higher frequency than printed circuit boards. Response is required.

  A printed wiring board is made by bonding an insulating substrate to a copper foil, or depositing a Ni alloy or the like on the insulating substrate and then forming a copper layer by electroplating to form a copper foil substrate, and then etching the copper foil or the copper layer surface by etching. In general, it is manufactured through a process of forming a conductor pattern. Therefore, good etching properties are required for the copper foil or copper layer for printed wiring boards.

  If the copper foil is not subjected to surface treatment on the non-adhesive surface with the resin, the copper portion of the copper foil circuit after etching is etched away from the surface of the copper foil, that is, toward the resin layer. (Sagging). Normally, the angle on the side of the circuit is “sagging”, and when a particularly large “sagging” occurs, the copper circuit may short-circuit near the resin substrate, resulting in a defective product. Here, FIG. 4 shows an enlarged photograph of the circuit surface showing an example in which “sagging” occurs during copper circuit formation and the copper circuit is short-circuited in the vicinity of the resin substrate.

  Such “sag” needs to be reduced as much as possible, but in order to prevent such widening etching failure, the etching time is extended, the etching is increased, and this “sag” is reduced. It is possible to make it. However, in this case, if there is a portion that has already reached the predetermined width dimension, it will be further etched, so that the circuit width of the copper foil portion will be reduced accordingly, and the circuit design will be a uniform target. The line width (circuit width) cannot be obtained, and heat is generated particularly in that portion (thinned portion), and in some cases, there is a problem of disconnection. As the fine patterning of electronic circuits further progresses, the problem due to such etching failure still appears more strongly and still becomes a big problem in circuit formation.

  As a method for improving these, Patent Document 1 discloses a surface treatment in which a metal or alloy layer having an etching rate slower than that of copper is formed on a copper foil on the etching surface side. In this case, the metal or alloy includes Ni, Co, and alloys thereof. In circuit design, the etching solution penetrates from the resist coating side, that is, from the surface of the copper foil, so if there is a metal or alloy layer with a slow etching rate directly under the resist, the etching of the copper foil portion in the vicinity is suppressed. Since the etching of the copper foil portion of the metal film progresses, the “sag” is reduced, and a circuit with a more uniform width can be formed. This makes it possible to form a sharper circuit compared to the prior art, and a great progress has been made. It can be said that there was.

  Further, in Patent Document 2, a Cu thin film having a thickness of 1000 to 10,000 mm is formed, and an Ni thin film having an etching rate slower than that of copper having a thickness of 10 to 300 mm is formed on the Cu thin film.

JP 2002-176242 A JP 2000-269619 A

  In recent years, further miniaturization and higher density of circuits have progressed, and there is a demand for circuits having side surfaces that are more steeply inclined. However, the technique described in Patent Document 1 cannot cope with these.

  Moreover, it is necessary to remove the surface treatment layer described in Patent Document 1 by soft etching, and furthermore, the non-adhesive surface-treated copper foil with the resin is applied to the resin in the process of being processed into a copper foil substrate. Etc. are subjected to high temperature treatment. This causes oxidation of the surface treatment layer, and as a result, the etching property of the copper foil deteriorates.

  As for the former, it is necessary to reduce the thickness of the surface treatment layer as much as possible in order to shorten the etching removal time as much as possible, and to remove it cleanly. In the latter case, in order to receive heat, The underlying copper layer is oxidized (discolored, so it is commonly called “yake”), due to poor resist coatability (uniformity, adhesion), excessive etching of interfacial oxide during etching, etc. There is a problem that defects such as etching property in pattern etching, short circuit, and controllability of the width of the circuit pattern occur, so that improvement is required or replacement with other materials is required.

  Then, this invention makes it a subject to provide the copper foil and laminated body for printed wiring boards excellent in the heat discoloration resistance and etching property.

  As a result of intensive studies, the present inventors have improved the adhesion to the non-adhesive surface side of the copper foil with the resin, usually the adhesive surface side to the resin, or adsorb the electroless plating nucleus on the insulator. When a noble metal particle is adsorbed on a copper foil at a predetermined concentration using a silane coupling agent mainly used for the purpose, a circuit is formed such that the inclination angle of the circuit side surface is 80 ° or more. I found out that I can do it. As a result, it has been found that a circuit that can sufficiently cope with the recent miniaturization and high density of the circuit can be formed, and further, the discoloration resistance of the copper foil surface is improved.

  The present invention completed based on the above knowledge, in one aspect, covers the copper foil base material and at least a part of the surface of the copper foil base material, and contains at least one of Au, Pt and Pd. The coating layer is composed of one or more kinds of noble metal particles of Au, Pt, and Pd and a silane coupling agent that covers the noble metal particles. From the depth direction analysis from the surface by XPS The atomic concentration (%) of Au, Pt, Pd in the depth direction (x: unit nm) obtained is a (x), the atomic concentration (%) of Cu is b (x), and the atomic concentration of Si ( %) Is c (x), the atomic concentration (%) of O is d (x), and the total atomic concentration (%) of other elements is e (x), in the interval [0, 1.0] 0.01 ≦ ∫a (x) dx / (∫a (x) dx + ∫b (x) dx + ∫c (x) dx + ∫d (x) dx + ∫e (x) dx) ≦ 0 .1, 0.4 ≦ ∫b (x) dx / (∫a (x) dx + ∫b (x) dx + ∫c (x) dx + ∫d (x) dx + ∫e (x) dx) ≦ 0.7, ∫c (x) dx / (∫a (x) dx + It is a copper foil for a printed wiring board satisfying ∫b (x) dx + ∫c (x) dx + ∫d (x) dx + ∫e (x) dx) ≦ 0.05.

  In another aspect, the present invention includes a copper foil base material, and a coating layer that covers at least a part of the surface of the copper foil base material and includes any one or more of Au, Pt, and Pd, The coating layer is composed of one or more kinds of noble metal particles of Au, Pt, and Pd and a silane coupling agent that covers the noble metal particles, and the depth direction obtained from the depth direction analysis from the surface by XPS ( The atomic concentration (%) of Au, Pt and Pd in x: unit nm) is a (x), the atomic concentration (%) of Cu is b (x), and the atomic concentration (%) of Si is c (x). Assuming that the atomic concentration (%) of O is d (x) and the total atomic concentration (%) of other elements is e (x), in the interval [0, 1.0], ∫a (x) dx / (∫a (x) dx + ∫b (x) dx + ∫c (x) dx + ∫d (x) dx + ∫e (x) dx) ≦ 0.1, ∫b (x) dx / ( ∫a (x) dx + ∫b (x) dx + ∫c (x) dx + ∫d (x) dx + ∫e (x) dx) ≦ 0. 0.05 ≦ ∫c (x) dx / (∫a (x) dx + ∫b (x) dx + ∫c (x) dx + ∫d (x) dx + ∫e (x) dx) ≦ 0 .15, which is a copper foil for printed wiring boards.

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

  In another aspect of the present invention, a step of preparing the copper foil of the present invention, a step of producing a laminate of a copper foil and a resin substrate using the coating layer of the copper foil as an etching surface, and a resist on the coating layer After forming a circuit pattern in step (b), an etching process using a ferric chloride aqueous solution or a cupric chloride aqueous solution to remove unnecessary portions of copper to form a copper circuit is performed. is there.

  In another aspect of the present invention, there is provided a laminate of the copper foil and the resin substrate according to the present invention.

  In still another aspect, the present invention is a laminate including a copper layer and a resin substrate, the laminate including the coating layer according to the present invention that covers at least a part of the surface of the copper layer.

  In one embodiment of the laminate according to the present invention, the resin substrate is a polyimide substrate.

  In yet another aspect, the present invention is a printed wiring board made of the laminate according to the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the copper foil and laminated body for printed wiring boards excellent in heat discoloration resistance and etching property can be provided.

It is the outline | summary of the calculation method of the etching factor (EF) using the surface photograph of a part of circuit pattern, the schematic diagram of the cross section of the width direction of the circuit pattern in the said part, and this schematic diagram. 10 is a photograph showing a circuit formed according to Example 3. It is a depth profile by XPS of the copper foil of Example 4 (before heat treatment). It is an enlarged photograph of the circuit surface which shows the example which produced tailing at the time of copper circuit formation, and the copper circuit short-circuited near the resin substrate.

(Copper foil base material)
Although there is no restriction | limiting in particular in the form of the copper foil base material which can be used for this invention, Typically, it can use with the form of rolled copper foil or electrolytic copper foil. In general, the electrolytic copper foil is produced by electrolytic deposition of copper from a copper sulfate plating bath onto a drum of titanium or stainless steel, and the rolled copper foil is produced by repeating plastic working and heat treatment with a rolling roll. Rolled copper foil is often used for applications that require flexibility.
In addition to high-purity copper such as tough pitch copper and oxygen-free copper, which are usually used as conductor patterns for printed wiring boards, for example, Sn-containing copper, Ag-containing copper, Cr, Zr or Mg are added as the copper foil base material. It is also possible to use a copper alloy such as a copper alloy, a Corson copper alloy to which Ni, Si and the like are added. In addition, when the term “copper foil” is used alone in this specification, a copper alloy foil is also included.

  There is no restriction | limiting in particular also about the thickness of the copper foil base material which can be used for this invention, What is necessary is just to adjust to the thickness suitable for printed wiring boards suitably. For example, it can be set to about 5 to 100 μm. However, for the purpose of forming a fine pattern, it is 30 μm or less, preferably 20 μm or less, and typically about 5 to 20 μm.

  Although the copper foil base material used for this invention is not specifically limited, For example, you may use what does not perform a roughening process. Conventionally, the surface is generally roughened by special plating with irregularities on the order of μm, and the physical anchor effect provides adhesion to the resin. A smooth foil is considered to have good characteristics, and a roughened foil may work in a disadvantageous direction. Moreover, since the roughening process process is abbreviate | omitted if it does not perform a roughening process, there exists an effect of economical efficiency and productivity improvement.

(Configuration of coating layer)
A coating layer is formed on at least a part of the surface of the copper foil base opposite to the surface to be bonded to the insulating substrate (circuit formation planned surface side). The coating layer is composed of noble metal particles and a silane coupling agent that covers the noble metal particles. The noble metal is composed of at least one of Au, Pt and Pd. It is desirable for improving the etching property that these noble metals adhere to the outermost surface of the coating layer (in the range of 0 to 1.0 nm from the surface) at a predetermined concentration. Therefore, in the copper foil for printed wiring board according to the present invention, the atomic concentration (%) of Au, Pt, and Pd in the depth direction (x: unit nm) obtained from the depth direction analysis from the surface by XPS. a (x), Cu atomic concentration (%) as b (x), Si atomic concentration (%) as c (x), O atomic concentration (%) as d (x), etc. Assuming that the total atomic concentration (%) of the element is e (x), 0.01 ≦ ∫a (x) dx / (∫a (x) dx + ∫b (x) in the interval [0, 1.0] dx + ∫c (x) dx + ∫d (x) dx + ∫e (x) dx) ≦ 0.1, 0.4 ≦ ∫b (x) dx / (∫a (x) dx + ∫b ( x) dx + ∫c (x) dx + ∫d (x) dx + ∫e (x) dx) ≦ 0.7, ∫c (x) dx / (∫a (x) dx + ∫b (x) dx + ∫c (x) dx + ∫d (x) dx + ∫e (x) dx) ≦ 0.05 is satisfied. When the concentration of at least one of Au, Pt, and Pd, Cu, and Si is outside the above range, good etching properties cannot be obtained.

  Moreover, you may obtain the copper foil for printed wiring boards by performing the heat processing (about 30 minutes-about several hours at about 350 degreeC) equivalent to polyimide hardening to the above-mentioned copper foil for printed wiring boards. In that case, the atomic concentration (%) of Au, Pt, Pd in the depth direction (x: unit nm) obtained from the depth direction analysis from the surface by XPS is defined as a (x), and the atomic concentration of Cu (% ) Is b (x), Si atomic concentration (%) is c (x), O atomic concentration (%) is d (x), and total atomic concentration (%) of other elements is e (x ) In the interval [0, 1.0], ∫a (x) dx / (∫a (x) dx + ∫b (x) dx + ∫c (x) dx + ∫d (x) dx + ∫e (x) dx) ≦ 0.1, ∫b (x) dx / (∫a (x) dx + ∫b (x) dx + ∫c (x) dx + ∫d (x) dx + ∫e (x) dx) ≦ 0.4, 0.05 ≦ ∫c (x) dx / (∫a (x) dx + ∫b (x) dx + ∫c (x) dx + ∫d (x) dx + ∫e (x) dx) ≦ 0.15 is satisfied. When the concentration of at least one of Au, Pt, and Pd, Cu, and Si is outside the above range, good etching properties cannot be obtained.

  In addition, on the adhesive surface side of the copper foil base material with the insulating substrate, for the purpose of improving the adhesiveness with the insulating substrate, for example, another coating layer composed of an intermediate layer and a surface layer laminated in order from the copper foil base material surface May be formed. In this case, the intermediate layer preferably contains at least one of Ni, Mo, Ti, Zn, Co, V, Sn, Mn, Nb, Ta, and Cr, for example. The intermediate layer may be composed of a single metal, for example, preferably composed of any one of Ni, Mo, Ti, Zn, Co, Nb, and Ta. The intermediate layer may be made of an alloy, for example, preferably made of an alloy of at least any two of Ni, Zn, V, Sn, Mn, Cr and Cu.

(Manufacturing method of copper foil)
The copper foil for printed wiring boards according to the present invention can be obtained by immersing the copper foil in a special solution containing a noble metal. That is, at least a part of the surface of the copper foil base material is coated with the coating layer by immersing the copper foil in a special solution containing a noble metal. Specifically, noble metal particles having an etching rate lower than that of copper are attached to the etched surface side of the copper foil by immersion in a silane coupling agent containing the noble metal. The coating layer is not limited to immersion of the copper foil in the carrier, but may be formed by, for example, electroplating or dry plating.

(Printed wiring board manufacturing method)
A printed wiring board (PWB) can be manufactured according to a conventional method using the copper foil according to the present invention. Below, the example of the manufacturing method of a printed wiring board is shown.

  First, a laminated body is manufactured by bonding a copper foil and an insulating substrate. The insulating substrate on which the copper foil is laminated is not particularly limited as long as it has characteristics applicable to a printed wiring board. For example, paper base phenolic resin, paper base epoxy resin, synthetic fiber for rigid PWB Use cloth base epoxy resin, glass cloth / paper composite base epoxy resin, glass cloth / glass non-woven composite base epoxy resin, glass cloth base epoxy resin, etc., use polyester film, polyimide film, etc. for FPC I can do things.

  In the case of the rigid PWB, a prepreg is prepared by impregnating a base material such as a glass cloth with a resin and curing the resin to a semi-cured state. It can be carried out by superposing a copper foil on the prepreg from the opposite surface of the coating layer and heating and pressing.

  In the case of a flexible printed wiring board (FPC), a polyimide film or a polyester film and a copper foil can be bonded using an epoxy or acrylic adhesive (three-layer structure). In addition, as a method without using an adhesive (two-layer structure), a polyimide varnish (polyamic acid varnish), which is a polyimide precursor, is applied to a copper foil and heated to form an imidization or on a polyimide film. There is a laminating method in which a thermoplastic polyimide is applied to the substrate, a copper foil is overlaid thereon, and heated and pressed. In the casting method, it is also effective to apply an anchor coating material such as thermoplastic polyimide in advance before applying the polyimide varnish.

  The laminate according to 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, the single-sided PWB, double-sided PWB, and multilayer PWB ( It is applicable to rigid PWB, flexible PWB (FPC), and rigid flex PWB from the viewpoint of the type of insulating substrate material. Further, the laminate according to the present invention is not limited to the above-described copper-clad laminate obtained by attaching a copper foil to a resin, and is a metalizing material in which a copper layer is formed on the resin by sputtering or plating. Also good.

A resist is applied to the surface of the coating layer formed on the copper foil of the laminate produced as described above, the pattern is exposed with a mask, and the resist pattern formed by development is immersed in an etching solution. At this time, the coating layer containing at least one of Pt, Pd, and Au is in a position near the resist portion on the copper foil, and the etching of the copper foil on the resist side is performed in the vicinity of the coating layer. Etching of the copper circuit pattern proceeds substantially vertically by etching of the copper away from the coating layer at a speed higher than the speed of the etching. Thus, unnecessary portions of copper can be removed, and then the etching resist can be peeled and removed to expose the circuit pattern.
With respect to the etching solution used for forming the circuit pattern on the copper foil substrate, the etching rate of the coating layer is sufficiently smaller than that of copper, so that the etching factor is improved. As the etching solution, an aqueous solution of cupric chloride, an aqueous solution of ferric chloride, or the like can be used, but an aqueous solution of ferric chloride is particularly effective. This is because the fine circuit takes time to etch, but the ferric chloride aqueous solution has a higher etching rate than the cupric chloride aqueous solution. In addition, a heat-resistant layer may be formed in advance on the surface of the copper foil base before forming the coating layer.
In addition, since the silane coupling agent contained in the coating layer has a rust-preventing effect, when the coating layer is formed of a silane coupling agent containing noble metal particles, a copper foil with excellent discoloration and a circuit with small tailing Is obtained.

(Circuit line pattern shape on the copper foil surface of the printed wiring board)
As described above, each line pattern of the circuit on the copper foil surface of the printed wiring board formed by etching from the coating layer side does not have two long side surfaces formed vertically on the insulating substrate. Usually, it is formed so as to spread from the surface of the copper foil downward, that is, toward the resin layer. Thus, the two long side surfaces each have an inclination angle θ with respect to the surface of the insulating substrate. It is important to reduce the pitch of the line pattern as much as possible for the finer circuit pattern (currently required), but if this inclination angle θ is small, the tailing will increase accordingly. The line pattern pitch becomes wider. In addition, the inclination angle θ is usually not completely constant within each line pattern and line pattern. If the variation in the inclination angle θ is large, the circuit quality may be adversely affected. Therefore, each line pattern of the circuit on the copper foil surface of the printed wiring board formed by etching from the coating layer side has an elongated angle θ of 65 to 90 ° with respect to the two long side surfaces with respect to the insulating substrate surface. And the standard deviation of tan θ in the same circuit is preferably 1.0 or less.

  EXAMPLES Examples of the present invention will be described below, but these are provided for better understanding of the present invention and are not intended to limit the present invention.

(Example 1: Examples 1 to 5)
(Formation of coating layer on copper foil)
As a copper foil base material of Examples 1 to 5, a rolled copper foil (C1100 made by Nikko Metal) having a thickness of 12 μm was prepared. The surface roughness (Rz) of the rolled copper foil was 0.5 μm.

First, a thin oxide film adhering to the surface of the copper foil was removed by reverse sputtering, and a Ni and Cr single layer target was sputtered to sequentially form a Ni layer and a Cr layer. The simple substance of the various metals used for sputtering used the thing of purity 3N. This surface was used as an adhesive surface with the insulating substrate.
-Equipment: Batch type sputtering equipment (ULVAC, Model MNS-6000)
・ Achieving vacuum: 1.0 × 10 ⁻⁵ Pa
・ Sputtering pressure: 0.2 Pa
・ Reverse sputtering power: 100W
・ Sputtering power: 50W
Film formation rate: About 0.2 μm of film was formed for each target for a fixed time, the thickness was measured with a three-dimensional measuring device, and the sputtering rate per unit time was calculated.

  Next, the surface-treated surface opposite to the adhesive surface of the surface-treated copper foil was covered with vinyl chloride, which was immersed in sulfuric acid (100 g / L) for 30 seconds to remove the surface oxide layer. Then, after immersing in the silane coupling agent CB-A (made by Nikko Metal) heated at 60 degreeC, the coating layer was formed by lightly washing with water. Here, the adhesion amount of Si and Pd was changed by changing the immersion time.

A polyimide film was bonded to the copper foil on which the coating layer was formed, on the surface opposite to the coating layer by the following procedure.
(1) Using an applicator on a copper foil of 7 cm × 7 cm, Ube Industries-made U varnish-A (polyimide varnish) was applied to a dry body to a thickness of 25 μm.
(2) The resin-coated copper foil obtained in (1) is dried at 130 ° C. for 30 minutes in an air dryer.
(3) Imidization at 350 ° C. for 60 minutes in a high-temperature heating furnace with a nitrogen flow rate set to 10 L / min.

<Measurement by XPS>
The operating conditions of XPS when creating the depth profile of the coating layer are shown below.
・ Device: XPS measuring device (ULVAC-PHI, Model 5600MC)
・ Achieved vacuum: 1.5 × 10 ⁻⁷ Pa
X-ray: Monochromatic AlKα, X-ray output 210 W, detection area 800 μmφ, angle 45 ° between sample and detector
Ion beam: ion species Ar ⁺ , acceleration voltage 3 kV, sweep area 3 mm × 3 mm, sputtering rate 2.0 nm / min (SiO ₂ conversion)
・ Measurement is a heat treatment (350 ° C. × 30 minutes) more severe than the polyimide curing condition (350 ° C. × 30 minutes) after being immersed in the coating film before heat treatment (coating before heat treatment) and the silane coupling agent. The film (the film after heat treatment) in a state of being subjected to (° C. × 120 minutes) was analyzed.

(Circuit shape by etching)
Ten circuits were printed by a photosensitive resist coating and exposure process on the surface on which the coating layer of copper foil was formed, and an etching process for removing unnecessary portions of the copper foil was performed under the following conditions.

<Etching conditions>
-Ferric chloride aqueous solution: (37 wt%, Baume degree: 40 °)
・ Liquid temperature: 50 ° C
・ Spray pressure: 0.25 MPa
(50 μm pitch circuit formation)
・ Resist L / S = 33μm / 17μm
-Finished circuit bottom (bottom) width: 25 μm
Etching time: 10 to 130 seconds (30 μm pitch circuit formation)
・ Resist L / S = 25μm / 5μm
-Finished circuit bottom (bottom) width: 15 μm
-Etching time: 30 to 70 seconds-Confirmation of etching end point: Etching was carried out at several levels by changing the time, and it was confirmed by an optical microscope that no copper remained between the circuits.
After the etching, the resist was peeled off by dipping in a 45 ° C. aqueous NaOH solution (100 g / L) for 1 minute.

<Etching factor measurement conditions>
The etching factor is the distance of the length of sagging from the intersection of the vertical line from the upper surface of the copper foil and the resin substrate, assuming that the circuit is etched vertically when sagging at the end (when sagging occurs) Is a ratio of a to the thickness b of the copper foil: b / a, and the larger the value, the larger the inclination angle, and the etching residue does not remain and the sagging is small. It means to become. FIG. 1 shows a surface photograph of a part of a circuit pattern, a schematic diagram of a cross section in the width direction of the circuit pattern at the part, and an outline of a method for calculating an etching factor using the schematic diagram. This a was measured by SEM observation from above the circuit, and the etching factor (EF = b / a) was calculated. By using this etching factor, it is possible to easily determine whether the etching property is good or bad. Furthermore, the inclination angle θ was calculated by calculating the arc tangent using a and the thickness b of the copper foil measured in the above procedure. The measurement range was a circuit length of 600 μm, and an etching factor of 12 points, its standard deviation, and an average value of the inclination angle θ were adopted as a result.

(Example 2: Comparative Example 1: Blank material)
A rolled copper foil having a thickness of 12 μm was prepared, and a polyimide film was bonded in the same procedure as in Example 1. Next, 10 circuits were printed on the opposite surface by a photosensitive resist coating and exposure process, and an etching process for removing unnecessary portions of the copper foil was performed under the conditions of Example 1.

(Example 3: Comparative Example 2)
A rolled copper foil having a thickness of 12 μm was prepared, immersed in CB-A for 2 minutes in the same procedure as in Example 1, and then a polyimide film was adhered thereto. Next, a circuit was formed by etching as in Example 1.
Each measurement result of Examples 1-3 is shown in Tables 1-4.

(Examples 1-5)
In each of Examples 1 to 5, the etching factor was large and there was no variation, and a circuit having a cross section close to a rectangular shape could be formed. When the immersion time was 20 minutes or more, the Si and Pd concentrations were saturated.
FIG. 2 shows a photograph of the circuit formed according to Example 3. In FIG. 3, the depth profile by XPS of the copper foil (before heat processing) of Example 4 is shown.
Further, in this example, a Pd-containing silane coupling agent was used as a special solution containing a noble metal into which the copper foil was immersed. Obviously, it has a similar effect.

(Comparative Examples 1-2)
Comparative Example 1 was a blank material in which the copper foil surface was untreated, and a circuit with a rectangular cross section could not be formed.
In Comparative Example 2, since the immersion time was not sufficient, the Pd concentration was not sufficient, and a circuit having a rectangular cross section could not be formed like the blank material.

Claims (8)

A copper foil base material, and a coating layer that covers at least a part of the surface of the copper foil base material and includes at least one of Au, Pt, and Pd,
The coating layer is composed of one or more kinds of noble metal particles of Au, Pt, and Pd, and a silane coupling agent that covers the noble metal particles.
The atomic concentration (%) of Au, Pt, and Pd in the depth direction (x: unit nm) obtained from the depth direction analysis by XPS is defined as a (x), and the atomic concentration (%) of Cu is defined as b. (x), Si atomic concentration (%) is c (x), O atomic concentration (%) is d (x), and total atomic concentration (%) of other elements is e (x). In the interval [0, 1.0], 0.01 ≦ ∫a (x) dx / (∫a (x) dx + xb (x) dx + ∫c (x) dx + ∫d (x) dx + ∫e (x) dx) ≦ 0.1, 0.4 ≦ ∫b (x) dx / (∫a (x) dx + ∫b (x) dx + ∫c (x) dx + ∫d (x ) dx + ∫e (x) dx) ≦ 0.7, ∫c (x) dx / (∫a (x) dx + ∫b (x) dx + ∫c (x) dx + ∫d (x) dx + Copper foil for printed wiring board satisfying ∫e (x) dx) ≦ 0.05. A copper foil base material, and a coating layer that covers at least a part of the surface of the copper foil base material and includes at least one of Au, Pt, and Pd,
The coating layer is composed of one or more kinds of noble metal particles of Au, Pt, and Pd, and a silane coupling agent that covers the noble metal particles.
The atomic concentration (%) of Au, Pt, and Pd in the depth direction (x: unit nm) obtained from the depth direction analysis by XPS is defined as a (x), and the atomic concentration (%) of Cu is defined as b. (x), Si atomic concentration (%) is c (x), O atomic concentration (%) is d (x), and total atomic concentration (%) of other elements is e (x). In the interval [0, 1.0], ∫a (x) dx / (∫a (x) dx + ∫b (x) dx + ∫c (x) dx + ∫d (x) dx + ∫e ( x) dx) ≦ 0.1, ∫b (x) dx / (∫a (x) dx + ∫b (x) dx + ∫c (x) dx + ∫d (x) dx + ∫e (x) dx) ≦ 0.4, 0.05 ≦ ∫c (x) dx / (∫a (x) dx + ∫b (x) dx + ∫c (x) dx + ∫d (x) dx + ∫e ( x) dx) Copper foil for printed wiring board satisfying ≦ 0.15.   The copper foil for printed wiring boards according to claim 1 or 2, wherein the printed wiring board is a flexible printed wiring board. Preparing the copper foil according to any one of claims 1 to 3,
A step of producing a laminate of the copper foil and the resin substrate using the coating layer of the copper foil as an etching surface;
Forming a circuit pattern with a resist on the coating layer, and then etching using a ferric chloride aqueous solution or a cupric chloride aqueous solution to remove unnecessary portions of copper to form a copper circuit;
A method of forming an electronic circuit comprising:   The laminated body of the copper foil and resin substrate in any one of Claims 1-3. A laminate of a copper layer and a resin substrate,
The laminated body provided with the coating layer in any one of Claims 1-3 which coat | covers at least one part of the surface of the said copper layer.   The laminate according to claim 5 or 6, wherein the resin substrate is a polyimide substrate.   The printed wiring board which used the laminated body in any one of Claims 5-7 as a material.