WO2011121803A1

WO2011121803A1 - Copper foil for printed wiring board having excellent thermal discoloration resistance and etching properties, and laminate using same

Info

Publication number: WO2011121803A1
Application number: PCT/JP2010/059372
Authority: WO
Inventors: 秀樹古澤; 美里中願寺
Original assignee: Jx日鉱日石金属株式会社
Priority date: 2010-03-30
Filing date: 2010-06-02
Publication date: 2011-10-06
Also published as: TWI423743B; JPWO2011121803A1; JP5079883B2; TW201212742A

Abstract

Disclosed are: a copper foil for a printed wiring board, which exhibits good etching properties when a circuit pattern is formed and is suitable for the formation of a fine pitch pattern, while having good discoloration resistance; and a laminate using the copper foil for a printed wiring board. Specifically disclosed is a copper foil for a printed wiring board, which comprises a copper foil base and a coating layer that covers at least a part of the surface of the copper foil base. The coating layer contains at least one element selected from among Ni, Zn, Sn, V, Mn, Co and Ag, and at least one element selected from among Pt, Pd and Au.

Description

Copper foil for printed wiring board excellent in heat discoloration resistance and etching property, and laminate using the same

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

Printed wiring boards have made great progress over the last half century, and today they are 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 laminate, and then etching the conductor on the copper foil or copper layer surface. In general, it is manufactured through a process of forming a 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. 3 shows an enlarged photograph of the circuit surface showing an example in which “sagging” occurs when the copper circuit is formed 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 a slower etching rate than 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.

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, miniaturization and higher density of circuits have further progressed, and a circuit having a more steep side surface has been demanded. 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 a process of processing into a laminate, and the application of the resin, etc. High temperature treatment is applied. 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.

Therefore, an object of the present invention is to provide a copper foil for a printed wiring board that has good etching properties when forming a circuit pattern, is suitable for fine pitch, and has good discoloration resistance, and a laminate using the same. .

As a result of intensive studies, the inventors have provided a coating layer containing Ni or the like and any one or more of Pt, Pd, and Au on the non-bonded surface side with the resin of the copper foil. Found that a circuit having an inclination angle of 80 ° or more on the side surface of the circuit can be formed, and further, the discoloration resistance of the copper foil surface is improved.

The present invention completed on the basis of the above knowledge includes, in one aspect, a copper foil base material and a coating layer covering at least a part of the surface of the copper foil base material, the coating layer comprising Ni, Zn, Sn, V , Mn, Co, and Ag, and a printed circuit board copper foil containing at least one of Pt, Pd, and Au.

In one embodiment of the copper foil for printed wiring boards according to the present invention, the coating layer includes a first coating layer containing at least one of Ni, Zn, Sn, V, Mn, Co, and Ag, and Pt. , Pd, and Au, and a second coating layer containing at least one of them.

In another embodiment of the copper foil for printed wiring board according to the present invention, the first coating layer is made of any one of Ni, Co, Ag, and Zn having a coating amount of 1500 μg / dm ² or less. .

In yet another embodiment of a copper foil for printed wiring boards according to the present invention, the first coating layer, the coating amount is made of 1500 [mu] g / dm ² or less of Ni and 1100μg / dm ² or less of Zn Ni- Zn alloy, Ni-Sn alloy coating amount is composed of 1500 [mu] g / dm ² or less of Ni and 500 [mu] g / dm ² or less of Sn, the amount of the coating consists of 1500 [mu] g / dm ² or less of Ni and 500 [mu] g / dm ² or less of V Ni- V alloy, or Ni-Mn alloy coating amount is composed of 1500 [mu] g / dm ² or less of Ni and 500 [mu] g / dm ² or less of Mn, or the coating amount 1500 [mu] g / dm ² or less of Ni and 1100μg / dm ² or less of Zn A Ni—Cu—Zn alloy made of Ni or a Ni—Cu alloy made of Ni with a coating amount of 1500 μg / dm ² or less.

In yet another embodiment of a copper foil for printed wiring boards according to the present invention, the amount of deposition of Pt in the second coating layer 1050μg / dm ² or less, the adhesion amount of Pd is 600 [mu] g / dm ² or less, Au Is less than 1000 μg / dm ² .

In still another embodiment of the copper foil for printed wiring board according to the present invention, the adhesion amount of Pt in the second coating layer is 20 to 400 μg / dm ² , and the adhesion amount of Pd is 20 to 250 μg / dm ^2. The adhesion amount of Au is 20 to 400 μg / dm ² .

In still another embodiment of the copper foil for printed wiring board according to the present invention, the adhesion amount of Pt in the second coating layer is 50 to 300 μg / dm ² , and the adhesion amount of Pd is 30 to 180 μg / dm ^2. The adhesion amount of Au is 50 to 300 μg / dm ² .

In yet another embodiment of the copper foil for printed wiring board according to the present invention, the first coating layer is formed on the surface of the copper foil base material, and the second coating layer is formed on the first coating layer. Has been.

In yet another embodiment of the copper foil for printed wiring board according to the present invention, the second coating layer is formed on the surface of the copper foil base material, and the first coating layer is formed on the second coating layer. Has been.

In yet another embodiment of the copper foil for printed wiring board 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 a rolled copper foil or an electrolytic copper foil composed of the copper foil according to the present invention, and a lamination of the copper foil and the resin substrate using the coating layer of the copper foil as an etching surface Forming an electronic circuit including a step of forming a body and a step of etching the laminate using an aqueous ferric chloride solution or an aqueous cupric chloride solution to remove unnecessary portions of copper to form a copper circuit Is the method.

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

Further another aspect of the present invention is a laminate including a copper layer and a resin substrate, the laminate including a 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 copper foil is bonded to polyimide.

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

According to the present invention, it is possible to provide a copper foil for a printed wiring board, which has good etching properties when forming a circuit pattern, is suitable for fine pitch, and has good discoloration resistance, and a laminate using the same.

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. 22 is a photograph showing a circuit formed in Comparative Example 13. It is an enlarged photograph of the circuit surface which shows the example which produced "sag" at the time of copper circuit formation, and the copper circuit short-circuited in the resin substrate vicinity.

(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.

The thickness of the copper foil base material that can be used in the present invention is not particularly limited, and may be appropriately adjusted to a thickness suitable for a printed wiring board. For example, the thickness can be 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.

The copper foil base material used in the present invention is not particularly limited, but for example, a material not subjected to roughening treatment may be used. 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.

(1) Structure of coating layer The coating layer is formed in at least one part of the surface on the opposite side (circuit formation plan side) of the copper foil base material with the insulating substrate. The coating layer includes at least one of Ni, Zn, Sn, V, Mn, Co, and Ag, and at least one of Pt, Pd, and Au. The coating layer includes a first coating layer containing at least one of Ni, Zn, Sn, V, Mn, Co, and Ag, and a second coating containing at least one of Pt, Pd, and Au. You may form with the coating layer. In this case, the first coating layer may be composed of any one of Ni, Co, Ag, and Zn having a coating amount of 1500 μg / dm ² or less. Furthermore, the first coating layer, Ni-Zn alloy coating amount is composed of 1500 [mu] g / dm ² or less of Ni and 1100μg / dm ² or less of Zn, the amount of coating 1500 [mu] g / dm ² or less of Ni and 500 [mu] g / dm ² or less Ni-Sn alloy consisting of Sn, Ni-V alloy coating amount is composed of 1500 [mu] g / dm ² or less of Ni and 500 [mu] g / dm ² or less and V, or the amount of coating 1500 [mu] g / dm ² or less of Ni and 500 [mu] g / dm Ni-Mn alloy composed of ² or less of Mn, or Ni-Cu-Zn alloy coating amount is composed of 1500 [mu] g / dm ² or less Ni and 1100μg / dm ² or less of Zn, or the amount of coating 1500 [mu] g / dm ² or less It may be made of a Ni—Cu alloy made of Ni. Thus, it is preferable that the first coating layer is made of an alloy containing Ni, among Ni, Co, Ag, and Zn, because the initial etching property becomes better. If the adhesion amount of each metal is less than the above numerical range, the initial etching property and discoloration resistance are adversely affected, and if it exceeds the above numerical range, the sagging of the circuit increases and the linearity becomes poor.

In the second coating layer, the adhesion amount of Pt 1050μg / dm ² or less, the adhesion amount of Pd is 600 [mu] g / dm ² or less, preferably adhesion amount of Au is 1000 [mu] g / dm ² or less. This is because exceeding these values adversely affects the initial etching property. More preferably, the adhesion amount of Pt is 20 to 400 μg / dm ² , the adhesion amount of Pd is 20 to 250 μg / dm ² , and the adhesion amount of Au is 20 to 400 μg / dm ² . When the coating amount of Pt of the coating layer is 20 μg / dm ² or more, the coating amount of Pd of the coating layer is 20 μg / dm ² or more, and the coating amount of Au of the coating layer is 20 μg / dm ² or more, the respective effects are obtained. Better. More preferably, the adhesion amount of Pt is 50 to 300 μg / dm ² , the adhesion amount of Pd is 30 to 180 μg / dm ² , and the adhesion amount of Au is 50 to 300 μg / dm ² .

Moreover, any of the first covering layer and the second covering layer may be formed first. That is, the first coating layer may be formed on the surface of the copper foil substrate, the second coating layer may be formed on the first coating layer, and the second coating layer is the surface of the copper foil substrate. The first coating layer may be formed on the second coating layer.

Furthermore, a chromium layer or a chromate layer and / or a silane treatment layer can be further formed on the coating layer in order to enhance the rust prevention effect.

(Manufacturing method of copper foil)
The copper foil for printed wiring boards according to the present invention can be formed by a sputtering method. That is, at least a part of the surface of the copper foil base material is formed by sputtering, at least one of Ni, Zn, Sn, V, Mn, Co, and Ag, and at least one of Pt, Pd, and Au. It can be coated with a coating layer composed of an alloy with a seed. Moreover, after forming the 1st coating layer which consists of Ni etc. in at least one part of the surface of a copper foil base material by sputtering method, any one of Pt, Pd, and Au whose etching rate is still lower than copper You may form the 2nd coating layer which consists of seed | species or more. Furthermore, after forming a second coating layer made of at least one of Pt, Pd, and Au having a lower etching rate than copper on at least a part of the surface of the copper foil base material by sputtering, A first coating layer made of Ni or the like may be formed. The first and second coating layers are not limited to the sputtering method, and may be formed by, for example, a wet plating method such as electroplating or electroless 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.

For the bonding method, in the case of rigid PWB, a prepreg in which a base material such as glass cloth is impregnated with a resin and the resin is cured to a semi-cured state is prepared. 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.

Since the copper foil laminate produced as described above has a coating layer containing Ni or the like on the copper foil surface, it is hardly discolored even by high-temperature heat treatment and has a good appearance.

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 second coating layer containing any one or more of Pt, Pd, and Au is in a position close to the resist portion on the copper foil, and the etching of the copper foil on the resist side Etching of the copper circuit pattern proceeds substantially vertically by etching of the copper away from the second coating layer at a rate faster than the rate at which the vicinity of the coating layer is etched. 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 laminate, the etching rate of the second 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.

(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 is not formed such that the two long side surfaces are perpendicular to the insulating substrate. Usually, the copper foil is formed so as to spread downward from the surface of the copper foil, that is, toward the resin layer (generation of sagging). 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 miniaturization of circuit patterns that are currently required (fine pitch). However, when the inclination angle θ is small, the sagging increases and the line increases. The 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 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 54, 56 to 64)
(Formation of coating layer on copper foil)
As the copper foil base materials of Examples 1 to 54 and 56 to 64, rolled copper foil (N1 Mineral C1100) having a thickness of 12 μm was prepared.

The thin oxide film adhering to the surface of the copper foil is removed by reverse sputtering, and after forming the first coating layer by sputtering each target such as Ni under the following apparatus and conditions, Pt, Pd, Au The second coating layer was formed by sputtering the target with the following apparatus and conditions. The thickness of the coating layer was changed by adjusting the film formation time. The simple substance of the various metals used for sputtering used the thing of purity 3N.
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.
Among the above examples, the following targets were used for Examples 13 to 15.
Target: Au-50 mass% Pd, Pt-50 mass% Pd, Au-50 mass% Pt
Among the above examples, the following targets were used for Examples 52 to 54.
・ Target: Au-50 mass% Ni, Pt-50 mass% Ni, Pd-50 mass% Ni
Among the above examples, the following targets were used for Examples 59 to 61.
Target: Ni-80 mass% Cu, and 3N purity Au, Pt or Pd
Among the above examples, the following targets were used for Examples 62 to 64.
Target: Ni-64 mass% Cu-18 mass% Zn, and 3N purity Au, Pt or Pd

The thin oxide film previously attached to the surface opposite to the coating layer was removed from the copper foil provided with the coating layer by reverse sputtering, and a Ni layer and a Cr layer were sequentially formed.
A polyimide film with an adhesive (manufactured by Nikkan Kogyo Co., Ltd., CISV1215) was laminated on the copper foil that had been subjected to the surface treatment by the above procedure by a hot press at a pressure of 7 kgf / cm ² and 160 ° C. for 40 minutes. Some copper foil was laminated | stacked with the polyimide film in the said procedure, after hold | maintaining at 350 degreeC for 2 hours by nitrogen atmosphere.

<Measurement of adhesion amount>
The amount of each metal adhering to the first coating layer was determined by dissolving a 50 mm × 50 mm copper foil surface coating in a mixed solution of HNO ₃ (2 wt%) and HCl (5 wt%). The concentration was quantified with an ICP emission spectroscopic analyzer (SFC-3100, manufactured by SII Nanotechnology Co., Ltd.), and the amount of metal per unit area (μg / dm ² ) was calculated.
The adhesion amount of Au, Pd, and Pt in the second coating layer was measured by atomic absorption spectrometry by dissolving the surface-treated copper foil sample with aqua regia, diluting the solution.

(Circuit shape by etching)
The etched surface of the copper foil was degreased with acetone and immersed in sulfuric acid (100 g / L) for 30 seconds to remove the surface contamination and the oxide layer. Next, a liquid resist (manufactured by Tokyo Ohka Kogyo Co., Ltd., OFPR-800LB) was dropped onto the etching surface using a spin coater and dried. The resist thickness after drying was adjusted to 1 μm. Thereafter, 10 circuits were printed by an exposure process, 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 ℃
・ 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 at different times, and it was confirmed by an optical microscope that no copper remained between the circuits.
After the etching, the resist was peeled off by being immersed in an aqueous NaOH solution (100 g / L) at 45 ° C. 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.

<Discoloration resistance test method>
The resistance to discoloration is measured using a thermostat at 300 ° C. for 10 minutes, and then using a color difference meter, L ^* (brightness), a ^* (red-green axis chromaticity), b ^* (yellow -The chromaticity of the blue axis) was measured and evaluated based on (JIS Z 8729) by ΔE ^* ab shown in Formula (1).
ΔE ^* ab = [(ΔL ^* ) ² + (Δa ^* ) ² + (Δb ^* ) ² ] ^1/2

(Example 2: Example 55)
A rolled copper foil having a thickness of 12 μm is prepared, a thin oxide film adhering to the surface of the copper foil is removed by reverse sputtering, a Pd target is sputtered to form a first coating layer, and then a Ni target is sputtered. As a result, a second coating layer was formed. Then, the polyimide film was adhere | attached in the same procedure. 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 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 4: Comparative Examples 2 to 43)
A rolled copper foil having a thickness of 12 μm was prepared, and the adhesive surface side with the resin was surface-treated in the same procedure as in Example 1, and then a polyimide film was adhered. Next, a first coating layer made of Ni or the like and a second coating layer made of Pt, Pd, or Au are formed on the copper foil surface by sputtering, and a circuit is formed by etching. did.
The measurement results of Examples 1 to 4 are shown in Tables 1 to 8. In Tables 3, 4, 7, and 8, the standard of the color difference on the surface of the copper foil in each numerical range of the heat discoloration resistance ΔE ^* ab is shown below.
ΔE ^* ab = 0-0.5 Very slightly different (trace)
ΔE ^* ab = 0.5 to 1.5 slightly different (slight)
ΔE ^* ab = 1.5-3.0 Notably different
ΔE ^* ab = 3.0 to 6.0 significantly different (appreciable)
ΔE ^* ab = 6.0 to 12.0 very different (much)
ΔE ^* ab = 12.0 or more (very much)

<Evaluation>
(Examples 1 to 64)
In Examples 1 to 15, although a slight discoloration was observed, it was possible to form a circuit having a cross section close to a rectangular shape with a large etching factor and no variation with both 50 μm and 30 μm pitch resist patterns. . In Examples 16 to 64, almost no discoloration was observed, and a resist pattern with both 50 μm pitch and 30 μm pitch was able to form a circuit having a cross section close to a rectangular shape with a large etching factor and no variation. .

(Comparative Examples 1-43)
Comparative Example 1 was a blank material with an untreated copper foil surface, and the sagging of the circuit increased with a resist pattern having a pitch of 50 μm and a pitch of 30 μm.
In Comparative Examples 2 to 6, since the adhesion amount of Ni, Zn, Sn, V or Mn in the first coating layer was insufficient, discoloration resistance was poor. Moreover, the 2nd coating layer was not formed and etching property was unsatisfactory.
In Comparative Examples 7 to 10, the adhesion amount of Ni or the like in the first coating layer was excessive, the initial etching property was inferior (30 μm pitch), and the sagging of the circuit increased (50 μm pitch).
In Comparative Examples 11 to 13, since the adhesion amount of Pt, Pd, and Au was excessive, the initial etching property was inferior (30 μm pitch), and the sagging of the circuit increased (50 μm pitch).
In Comparative Examples 14 to 43, the adhesion amount of Ni or the like in the first coating layer was excessive, the initial etching property was inferior (30 μm pitch), and the sagging of the circuit was increased (50 μm pitch).
FIG. 2 shows a photograph of the circuit formed in Comparative Example 13.

Claims

A copper foil base material, and a coating layer covering at least a part of the surface of the copper foil base material,
The said coating layer is a copper foil for printed wiring boards containing at least any 1 type of Ni, Zn, Sn, V, Mn, Co, and Ag and at least any 1 type of Pt, Pd, and Au.
The coating layer includes a first coating layer containing at least one of Ni, Zn, Sn, V, Mn, Co, and Ag, and a second coating containing at least one of Pt, Pd, and Au. The copper foil for printed wiring boards of Claim 1 formed with the coating layer of this.
The copper foil for printed wiring boards according to claim 2, wherein the first coating layer is made of any one of Ni, Co, Ag, and Zn having a coating amount of 1500 µg / dm 2 or less.
Said first coating layer, the coating amount of Ni-Zn alloy consisting of 1500 [mu] g / dm 2 or less of Ni and 1100μg / dm 2 or less of Zn, the coating amount of 1500 [mu] g / dm 2 or less of Ni and 500 [mu] g / dm 2 or less of Ni-Sn alloy comprising Sn, Ni-V alloy coating amount is composed of 1500 [mu] g / dm 2 or less of Ni and 500 [mu] g / dm 2 or less and V, or the amount of coating 1500 [mu] g / dm 2 or less of Ni and 500 [mu] g / dm 2 Ni-Mn alloy consisting of Mn, or Ni-Cu-Zn alloy coating amount is composed of 1500 [mu] g / dm 2 or less of Ni and 1100μg / dm 2 or less of Zn, or the amount of coating 1500 [mu] g / dm 2 or less of The copper foil for printed wiring boards according to claim 2, comprising a Ni-Cu alloy made of Ni.
The adhesion amount of Pt in the second coating layer 1050μg / dm 2 or less, the adhesion amount of Pd is 600 [mu] g / dm 2 or less, in any one of claims 2-4 adhering amount of Au is 1000 [mu] g / dm 2 or less The copper foil for printed wiring boards as described.
6. The adhesion amount of Pt in the second coating layer is 20 to 400 μg / dm 2 , the adhesion amount of Pd is 20 to 250 μg / dm 2 , and the adhesion amount of Au is 20 to 400 μg / dm 2 . Copper foil for printed wiring boards.
The adhesion amount of Pt in the second coating layer is 50 to 300 μg / dm 2 , the adhesion amount of Pd is 30 to 180 μg / dm 2 , and the adhesion amount of Au is 50 to 300 μg / dm 2 . Copper foil for printed wiring boards.
The printed wiring board according to any one of claims 2 to 7, wherein the first coating layer is formed on a surface of the copper foil base material, and the second coating layer is formed on the first coating layer. Copper foil.
The printed wiring board according to any one of claims 2 to 7, wherein the second coating layer is formed on a surface of the copper foil base material, and the first coating layer is formed on the second coating layer. Copper foil.
10. The printed wiring board copper foil according to claim 1, wherein the printed wiring board is a flexible printed wiring board.
Preparing a rolled copper foil or an electrolytic copper foil composed of the copper foil according to any one of claims 1 to 10,
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;
Etching the laminate with an aqueous ferric chloride solution or an aqueous cupric chloride solution to remove unnecessary portions of copper to form a copper circuit;
A method of forming an electronic circuit comprising:
A laminate of the copper foil according to any one of claims 1 to 10 and a resin substrate.
A laminate of a copper layer and a resin substrate,
A laminate comprising the coating layer according to any one of claims 1 to 10, which covers at least a part of the surface of the copper layer.
The laminate according to claim 12 or 13, wherein the resin substrate is a polyimide substrate.
A printed wiring board made of the laminate according to any one of claims 12 to 14.