JPH06120630A - Copper foil for printed wiring board - Google Patents

Abstract

PURPOSE:To have adhesion equal to the case where a conventional chromium layer is used as a middle layer by etching a copper layer and an Ni-Cr copper layer successively in one kind of etchant, using the Ni-Cr copper layer, where nickel is added to chromium, as the middle layer between a supporting substrate and the copper layer. CONSTITUTION:In a copper foil for a printed wiring board, an Ni-Cr copper layer, where Ni is 5-89 atomic %, is provided as a middle layer, between the supporting substrate 1 and the copper layers 3 and 4. In the constitution of the copper foil, the Ni-Cr-OX oxide made at the interface between the Ni-Cr copper layer 2 and the supporting substrate 1 is fine and high in adhesion similar to chromium oxide. Hereby, the interface between the Ni-Cr copper layer 2 and the copper layers 3 and 4 made thereon becomes strong coupling between metal and metal. Therefore, for the copper layers 3 and 4 under which the Ni-Cr copper layer 2 is made as the middle layer, the adhesive strength with the supporting substrate 1 becomes a high value of 1000g/cm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper foil for a printed wiring board, and more specifically, it can be easily etched for forming a wiring pattern and has excellent adhesion to a supporting substrate. And a copper foil for a printed wiring board.

[0002]

2. Description of the Related Art Conventionally, a tape automatic bonding (T) has been used as a supporting substrate for coating a copper foil for printed wiring.
For AB) and flexible printed wiring boards (FPC), heat resistant polymer films such as polyimide and polyamide are also required for soldering when wiring patterns and elements need to be soldered. Polymer films made of polyethylene terephthalate, polyethylene naphthalate, etc. are known in the case where the above is not required, and ceramics such as alumina (Al ₂ O ₃ ) and glass epoxy are known for rigid wiring. Then, a rolled copper foil or an electrolytic copper foil having a thickness of about 12 to 50 μm is attached to these supporting substrates with an adhesive to form a copper foil for a printed wiring board,
A wiring pattern was applied to the copper foil.

With the recent miniaturization of equipment, there is a demand for a copper foil which is thinner than the conventional laminated copper foil in order to cope with finer wiring patterns.

In order to meet this requirement, a copper foil formed on a supporting substrate by combining a sputtering method and a plating method, which can be thinned by replacing the conventional laminated copper foil, is now in the mainstream position. .

Further, the adhesion between a support substrate such as a polymer film and ceramics and a copper layer coated on the surface is due to the formation of a brittle layer such as copper oxide (CuO, Cu ₂ O) at the interface. It is very weak, and it is usually required to maintain the adhesion strength of 1000g / cm with the copper layer required for printed wiring boards.
A chromium layer was provided as an intermediate layer between the supporting substrate and the copper layer.

The chromium provided as the intermediate layer becomes an oxide, that is, chromium oxide to form a dense layer, and the interface between the chromium layer and the copper layer formed thereon is a metal-metal bond. Therefore, a brittle layer of copper oxide does not occur between the supporting substrate and the copper layer.

Therefore, by interposing a chromium layer as an intermediate layer between the supporting substrate and the copper layer, the chromium layer is as thin as 200Å, but the gap between them is 1000 g / cm 2.
It is possible to obtain a high adhesion strength.

An example of the configuration will be described with reference to FIG.
A chromium layer b having a thickness of about 200 Å is formed on a supporting substrate a of polyimide, alumina, or the like by a sputtering method in order to secure adhesion with a copper layer. Further, the supporting substrate a on which the chrome layer b is formed has a thickness of 200 as an initial electrode when electrolytically plating a thick copper layer to be a wiring pattern in a plating bath.
The underlying copper layer c having a thickness of about 0Å is formed by the sputtering method.
Further, a supporting substrate a on which a chrome layer b and a base copper layer c are formed
A plated copper layer d having a thickness of about 20 μm is formed on the base copper layer c by electrolytic plating in a plating bath.

Then, in order to form the copper layers c and d in a desired wiring pattern, application of a resist material on the copper layers c and d, exposure treatment, etching treatment in an etching solution, and cleaning treatment are performed. Then, the copper layers c and d are used as a wiring film for a printed wiring board.

Usually, a ferric chloride-based solution is used as the etching solution for the copper layers c and d, and a mixed solution of ferric chloride and hydrochloric acid is used as the etching solution for the chromium layer b because of the good corrosion resistance of chromium. ing. Then, when performing the etching treatment, first, the copper layers c and d are etched with a ferric chloride solution, and subsequently, the chromium layer b is etched with a mixed solution of ferric chloride and hydrochloric acid.

[0011]

The supporting substrate a having the above-mentioned structure
In order to form a wiring pattern on the copper layers c and d (copper foil) and the chromium layer b coated on the resist layer, resist material coating, pattern exposure, etching treatment, and cleaning treatment are performed. A wiring pattern can be easily formed with a ferric chloride-based etching solution.

However, since chromium is excellent in corrosion resistance, a pattern cannot be formed with the same etching solution as the copper layer, and since it is performed with a mixed solution of ferric chloride and hydrochloric acid, one type of chromium is used. Since the etching treatment of the copper foil and the chrome layer cannot be performed continuously with the etching solution, and therefore the etching treatment has two steps, and the etching treatment to the chrome layer must be performed in a short time, the etching treatment becomes complicated. Not only that, since the entire etching process takes a long time, over-etching progresses on the sidewalls of the copper layers c and d that have already been etched during the etching process on the chromium layer b, causing a defect in the wiring pattern. There is a problem that leads to disconnection.

In addition, since it is essential to interpose a chromium layer as an intermediate layer in order to secure the adhesion between the supporting substrate and the copper layer, it has been a cause of lowering the product yield and increasing the cost.

The present invention solves such a problem and can form a wiring pattern with one kind of etching solution,
An object of the present invention is to provide a copper foil for a printed wiring board, which has an adhesion strength equivalent to that when a chromium layer is interposed as an intermediate layer.

[0015]

DISCLOSURE OF THE INVENTION As a result of intensive studies to achieve the above object, the present invention has revealed that a Ni--Cr alloy layer in which nickel is added to chromium instead of a chromium layer as an intermediate layer between a supporting substrate and a copper layer. It was found that the copper layer and the Ni-Cr alloy layer can be continuously etched with one type of etching solution by using, and the adhesiveness is equivalent to that when a conventional chromium layer is used as an intermediate layer. did.

The copper foil for a printed wiring board of the present invention is made on the basis of the above findings, and in the copper foil for a printed wiring board, Ni is 5 at% as an intermediate layer between the support substrate and the copper layer. It is characterized in that a Ni-Cr alloy layer of -80 at% is provided.

[0017]

Function: Ni-C is provided as an intermediate layer between the support substrate and the copper layer.
Since the r-alloy layer is present, the adhesion strength between the supporting substrate and the copper layer is 1000 g / cm, and the copper layer and the Ni-Cr alloy layer can be etched in one etching process to form the wiring pattern. Easy to form.

[0018]

The copper foil for printed wiring boards of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows one embodiment of a copper foil for a printed wiring board of the present invention, in which 1 is polyimide,
A supporting substrate made of a polymer material such as polyamide, polyethylene terephthalate, or polyethylene naphthalate, or a ceramic material such as alumina or glass epoxy is shown.

The support substrate 1 has, for example, Ni on the surface of 70
Ni-Cr with a thickness of 200Å formed by DC magnetron sputtering with a target material of at% Ni-Cr alloy
The alloy layer 2 is formed. In addition, the Ni-Cr alloy layer 2
A target material is, for example, 99.99% oxygen-free copper, and a thickness of 200 is formed by the DC magnetron sputtering method.
A 0Å copper layer 3 is formed. Furthermore, 2 on the copper layer 3
Thickness plated by electrolytic plating method in 0 wt% copper sulfate solution 2
A copper layer 4 of 0 μm is formed.

As for the Ni-Cr alloy layer 2 and the copper layer 3, a Ni-Cr cathode and a copper cathode are installed in one vacuum film forming chamber, and the support substrate 1 is placed in the vacuum film forming chamber by DC magnetron sputtering. A film was continuously formed while passing the film.

These structures are the same except that the chromium layer, which is the intermediate layer of the conventional copper foil for printed wiring boards, is replaced with a Ni--Cr alloy layer.

In the copper foil structure of the present invention, Ni—Cr—O formed at the interface between the Ni—Cr alloy layer 2 and the supporting substrate 1 is used.
The oxide of x is dense and has high adhesion like chromium oxide (Cr ₂ O ₃ , CrO ₂ ).
Then, the interfaces with the copper layers 3 and 4 formed thereon form strong metal-metal bonds. Therefore, Ni-Cr as the intermediate layer
The copper layers 3 and 4 on which the alloy layer 2 is formed have a high adhesion strength with the supporting substrate 1 of 1000 g / cm.

Although the plating method is used to form the copper layer 4 in the above-described embodiment, when the copper layer 3 is formed by the sputtering method, the copper layer 4 is formed by the sputtering method after the formation of the copper layer 3. Good. Further, although the sputtering method is used to form the copper layer 3 on the Ni—Cr alloy layer 2 in the above-mentioned embodiment, the copper layer 3 and the copper layer 4 may be continuously formed by the vapor deposition method or the CVD method. Good. Further, formation of the Ni—Cr alloy layer 2, the copper layer 3 and the copper layer 4 formed on the support substrate 1 is performed by a sputtering method, a vapor deposition method,
Any one of the CVD methods or a combination of these methods may be used.

Next, specific experimental examples of the present invention will be described.

Experimental Example In this experimental example, the Ni—Cr alloy layer 2, the copper layer 3, and the copper layer 4 were formed on the support substrate 1 as follows.

First, a supporting substrate 1 made of polyimide having a thickness of 50 μm is placed in a vacuum film forming chamber equipped with a continuous winding type sputtering device having two Ni--Cr cathodes and Cu cathodes, and then the vacuum film forming is carried out. The inside of the chamber was set to a vacuum degree of 1 × 10 ⁻⁵ Torr or less through a vacuum pump or the like, and subsequently, argon gas was introduced so that the inside of the film forming chamber became 5 × 10 ⁻³ Torr.
Then, various Ni—Cr alloy layers 2 having different Ni contents as shown in FIG. 2 and having a thickness of 200 Å are formed on the supporting substrate 1 by the DC magnetron sputtering method. 2000Å thick copper layer 3 on Cr alloy layer 2
Was continuously formed, the supporting substrate 1 was taken out from the vacuum film forming chamber.

The Ni content of the Ni—Cr alloy layer 2 formed on the supporting substrate 1 is adjusted by using a target having a different composition of Ni—Cr alloy (the amount of Ni doped into Cr). Further, the copper layer 3 formed on the Ni—Cr alloy layer 2 targeted 99.99% oxygen-free copper.

Subsequently, the supporting substrate 1 is dipped in a 20 wt% copper sulfate solution, and a thickness of 20 μm is formed on the copper layer 3 by electrolytic plating.
After forming the plated copper layer 4 of m, the supporting substrate 1 is taken out from the electrolytic plating bath and washed to prepare a copper foil for each substrate having a Ni-Cr alloy layer having a different Ni content as an intermediate layer. did.

In order to form a wiring pattern on the copper layers 3 and 4 of each of the prepared copper foils for substrates, a resist material is applied and exposed in a conventional manner to form a resist pattern having a line space of 20 μm, and then chloride. A predetermined wiring pattern was formed on the copper layers 3 and 4 by performing an etching treatment by dipping ferric iron in an etching solution of 40 g / liter at a temperature of 50 ° C. and a cleaning treatment.

Then, the adhesion strength (g / cm) between the supporting substrate 1 and the copper layers 3 and 4 of the copper foil for each substrate was measured by a 180 ° reversal peeling method (based on JPCA-FC01-4.4),
The measurement result is shown in FIG.

Further, the cross-sectional shape of each copper foil for a substrate on which a wiring pattern is formed is observed with a scanning electron microscope (SEM),
The pattern is shown in FIG. In FIG. 3, the Ni content in the Ni—Cr alloy layer is 0 at%, 4 at%, 5 at%, and 80 at%.
Only the case of at% is shown.

As is clear from FIG. 2, it was confirmed that when Ni in the Ni—Cr alloy layer was in the range of 1 at% to 80 at%, the same adhesion strength as that obtained only with the chromium layer containing no Ni was obtained. Was done. Also, as is clear from FIG.
When Ni in the i-Cr alloy layer is 4 at%, or in the case of a chromium layer containing no Ni, the chromium layer as the intermediate layer or the Ni-Cr alloy layer having 4 at% Ni should be etched during the etching treatment. Although it remains as a residue as it is, it is confirmed that the Ni-Cr alloy layer containing 5 at% Ni and 80 at% Ni is removed together with the copper layer formed on the Ni-Cr alloy layer at the time of etching, and the wiring pattern can be reliably formed. Was done.

As described above, the copper foil having the Ni—Cr alloy layer containing 5 to 80 at% Ni as the intermediate layer of the present invention is
It has a high adhesion strength of 1000 g / cm, and it is possible to reliably form a wiring pattern with one type of etching solution.
It can greatly contribute to simplification of process, increase of product yield, and cost reduction.

[0034]

According to the copper foil for a printed wiring board of the present invention, Ni is contained between the supporting substrate and the copper layer in an amount of 5 at% to 80 at%.
Since the intermediate layer of the at% Ni-Cr alloy layer is provided, the adhesion strength between the supporting substrate and the copper layer is as high as 1000 g / cm, and the line space 2 can be formed with one type of etching solution.
Since a fine pattern of about 0 μm can be formed, when forming a wiring pattern on a copper foil for a printed wiring board, there are effects such as simplification of the process, an increase in product yield, and a cost reduction.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of one embodiment of a copper foil of the present invention,

FIG. 2 is a characteristic diagram showing the relationship between the adhesion strength between a support substrate and a copper layer and changes in the amount of Ni in a Ni—Cr alloy layer in an experimental example of the present invention,

FIG. 3 shows N after etching treatment in the experimental example of the present invention.
Schematic diagram showing the relationship between the amount of Ni in the i-Cr alloy layer and the etching state of the copper layer and the intermediate layer on the support substrate,

FIG. 4 is a cross-sectional view of a conventional copper foil.

[Explanation of symbols]

1 supporting substrate, 2 intermediate layer, 3, 4 copper layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hisami Nakamura 523 Yokota, Yamatake-cho, Yamatake-gun, Chiba Japan Vacuum Technology Co., Ltd. Chiba Institute for Super Materials (72) Inventor Hiroaki Kawamura 523 Yokota, Yamatake-cho, Sanmu-gun, Chiba Japan Vacuum Technology Co., Ltd. Chiba Institute for Materials Research

Claims (1)

[Claims] 1. A copper foil for a printed wiring board, wherein Ni is 5 at% to 80 as an intermediate layer between the support substrate and the copper layer.
A copper foil for a printed wiring board, which is provided with an at% Ni-Cr alloy layer.