JP2002076552A - Copper foil for printed circuit board and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper foil for a printed circuit board reducing an environmental load due to chroming while maintaining rustproofness and an adhesive strength with an insulating resin and to provide a method for manufacturing the same. SOLUTION: The copper foil for the printed circuit board comprises a layer made of an aluminum oxide or a layer containing a metal zinc and the aluminum oxide on at least one side surface of the foil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a copper foil for a printed wiring board used for a printed wiring board and a method for producing the same.

[0002]

2. Description of the Related Art In general, copper foil used for printed wiring boards is subjected to a roughening treatment for improving the bonding strength between an untreated copper foil manufactured by an electrolytic method or a rolling method and an insulating resin;
It is manufactured by forming a surface treatment layer for the purpose of improving rust prevention and adhesion strength with an insulating resin.

[0003] A surface treatment layer, for example, a chromium coating (chromate layer) formed by using a chromate aqueous solution is effective in enhancing rust prevention. Hexavalent chromium contained in the chromium coating is, It is highly toxic, harmful to the environment and health care, and regulations are being tightened. Therefore, the development of a chromium substitute coating that has a small environmental load, is safe and has no harm to the body is desired.

Conventionally, as a rust preventive treatment other than chromium, a process using benzotriazole or the like (Japanese Patent Application Laid-Open No. 8-31690)
JP-A-9-41167), those based on silane compounds (JP-A-9-3077), and those based on other organic substances (JP-A-9-2990) have been proposed. In addition, as a treatment for improving the adhesiveness, the copper foil
One that forms a film of an oxide or hydroxide of i, Zr or Ti (Japanese Patent Application Laid-Open No. 6-41761) has been proposed. However, there is no example having the same rust prevention and adhesiveness as chromium.

It is generally well known that a zinc coating is formed on a copper surface using a plating bath containing zinc ions. For example, JP-A-51-1331 discloses that
Immerse copper in an alkaline aqueous solution containing zinc ions,
Alternatively, a method has been proposed in which a dense oxide layer containing Zn and Cu is formed on the copper surface by applying a current in the alkaline aqueous solution using copper as an anode.

However, in any of the surface treatment methods as in the above-mentioned prior art, there is a problem that the rust prevention is inferior to the chromium-treated copper foil in any case, and the chromium treatment is excluded from the copper foil for printed wiring boards. Not yet.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a copper foil for a printed wiring board and a method for producing the same, which maintain the rust resistance and the adhesive strength to an insulating resin and reduce the environmental load by chromium treatment. Is to provide.

[0008]

The inventor of the present invention has conducted intensive studies on the above-mentioned problems of the prior art, and as a result, as a chromium substitution treatment, a layer made of aluminum oxide or a layer made of metal zinc and aluminum oxide is formed on a copper foil surface. By providing a layer, it has been found that a copper foil for a printed wiring board having a large environmental load and excluding chromium treatment can be obtained while maintaining the rust resistance and the adhesive strength between the insulating resin, and the present invention based on this finding. It was completed. The present invention relates to a copper foil for a printed wiring board, comprising a layer made of aluminum oxide or a layer made of metal zinc and aluminum oxide on at least one surface of the copper foil. The present invention also provides a plating bath containing aluminum ions or a plating bath containing zinc ions and aluminum ions, wherein a copper foil is subjected to a cathode treatment in the plating bath, and a layer made of aluminum oxide is formed on at least one surface of the copper foil. Alternatively, the present invention relates to a method for producing a copper foil for a printed wiring board, comprising forming a layer composed of metallic zinc and aluminum oxide.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A feature of the present invention is that a layer made of aluminum oxide (hereinafter, referred to as an aluminum layer) or a layer made of metallic zinc and aluminum oxide (hereinafter, referred to as a zinc-aluminum layer) is formed on a copper foil for a printed wiring board. ), And this layer is firmly adhered to the copper foil surface of the substrate. Oxides and hydroxides of zinc and aluminum may be slightly mixed near the surface of the zinc-aluminum layer. Explaining the ratio of the metal amount of zinc and aluminum constituting the aluminum layer or the zinc-aluminum layer as the adhesion amount, the aluminum adhesion amount is 5 to 200 μg / dm ² , and the zinc adhesion amount is 10 to 5
It is preferably in the range of 00 μg / dm ² . If it exceeds the respective ranges, rust resistance may decrease, depending on the ratio of both. Particularly preferably, the adhesion amount of each of them is 10 to 100 μg / dm ² .

Means for producing the copper foil for a printed wiring board of the present invention by forming an aluminum layer or a zinc-aluminum layer on the surface of the copper foil is to subject the copper foil to a cathodic electrolytic treatment by a known electroplating method. It is practically desirable to implement the method in terms of mass productivity and economy. The production method of the present invention uses this electroplating method, using a plating bath containing aluminum ions or a plating bath containing aluminum ions and zinc ions, performing a cathodic treatment on the copper foil in the plating bath, An aluminum layer or a zinc-aluminum layer is formed on at least one side of the copper foil.

[0011] The copper foil used in the method of the present invention comprises:
Typical examples are an electrolytic copper foil and a rolled copper foil, but are not particularly limited. The thickness of the copper foil is not particularly limited as long as it is a thickness used as a copper foil for a printed wiring board. In the present invention, in order to increase the adhesive strength of the surface to be bonded to the resin substrate after lamination, it is preferable to use a copper foil whose surface has been subjected to electrochemical and physical roughening treatment in advance.

Next, the plating bath used in the method of the present invention will be described. Metal ions contained in the plating bath are aluminum ions or aluminum ions and zinc ions. As an example of an aluminum ion supply source, Al ₂ (SO ₄ ) ₃ .14 to 18H ₂ O, Al
(OH) ₃ , AlCl ₃ , Al (NO ₃ ) _{3 and the} like are preferable. As a source of zinc ions, ZnSO ₄ (Z
nSO ₄ · 7H ₂ O, _{etc.), ZnCl 2, Zn (CH} 3 C
OO) _{2 and the} like are preferable.

At least one of the aluminum ion sources
A plating bath is made by dissolving at least one of the species, or a source of aluminum ions, and a source of zinc ions in water. In setting the content of both metal ions in the plating bath, the content is determined in consideration of the plating metal adhesion amount, current density, energizing time, and the like, and each is usually selected from the range of 0.1 to 50 g / l. can do. For example, Al ₂ (SO
_{4) 3} · _14~18H with ₂ O, when using ZnSO ₄ · 7H ₂ O to zinc ion source, 0.1 respectively
It is particularly preferred to use it in the range of 10 g / l.

Although the pH of the plating bath can be adjusted to a wide range from acidic to alkaline and used, it is usually preferable to use acidic. When alkaline, it is desirable to add a complexing agent such as sulfamic acid to prevent precipitation of metal ions. For the purpose of imparting conductivity to the plating bath, salts such as sodium sulfate and ammonium chloride may be added. The solution temperature of the plating bath may be normal temperature, or may be heated to, for example, about 80 ° C. before use.

A copper foil is immersed in the plating bath, and the copper foil is
As an aluminum layer on the copper foil surface
Alternatively, a zinc-aluminum layer is formed. Current density and
For the energizing time, refer to the above metal ion amount,
Since it is related to other conditions such as quantity and its ratio, it is generally specified
Although not possible, current density is usually 0.01 to 10 A / d
m ², Preferably 0.05 to 5 A / dm², Energizing time 1
To 60 seconds, preferably 1 to 30 seconds.
Is desirable. If necessary, roughen at least one side.
The treated copper foil is subjected to a water washing step,
Plating bath containing aluminum ions or aluminum ions
One or both sides of copper foil in a plating bath containing zinc and zinc ions.
Provide an insoluble anode disposed opposite to the surface, under the above electrolysis conditions
Cathode treatment on one side, preferably roughened side, or both sides of copper foil
By applying, aluminum layer or zinc-aluminum
Layer is formed, and the copper foil for a printed wiring board of the present invention is manufactured.
Is done. Coupling is further added on the layer to improve the adhesive strength.
May be applied.

In practicing the production method of the present invention, for example, a copper foil wound in a coil shape having a predetermined thickness and width is provided with a degreasing tank, an acid washing tank, a water washing tank provided as necessary. A copper plating tank for surface roughening treatment, a washing tank, and then a plating tank for forming an aluminum layer or a zinc-aluminum layer, a washing tank, and a copper foil processing apparatus having a configuration in which a drying device and the like are connected. Preferably, it is manufactured by winding it.

The thus-obtained copper foil for a printed wiring board of the present invention is formed into a copper-clad laminate by heating and pressure bonding to a resin substrate of a phenol resin, an epoxy resin, or a polyimide resin. Later, it is used as a printed wiring board.

[0018]

The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples. Example 1 6.3 g of aluminum sulfate 14-18 hydrate was dissolved in water to make 1 liter, and a plating bath was prepared at a pH of 3.5 and a bath temperature of 30 ° C. Using this plating bath, an electrolytic copper foil (thickness: 18 μm) whose one surface has been roughened in advance is immersed, and a current density of 0.15 A / dm ² and an energizing time of 1 are applied to the roughened surface of the copper foil.
Cathode treatment was performed at 0 seconds to form an aluminum layer. Immediately after the cathode treatment, the copper foil was taken out of the plating solution, washed with water, and dried in a drier maintained at a temperature of 100 ° C.
Further, when the plating metal adhesion amount of the aluminum layer was analyzed by an ICP analyzer, the aluminum adhesion amount was 23 μg.
/ Dm ² .

Next, in order to carry out the following property tests, the obtained copper foil with an aluminum layer was laminated on an FR-4 grade epoxy resin impregnated glass cloth substrate with the roughened surface in contact with the substrate surface, and the temperature was lowered. Heating and pressurizing under conditions of 168 ° C., pressure 2.94 MPa, time 60 minutes, length 250 mm, width 250 m
A required amount of a copper-clad laminate having a thickness of 1.6 mm and a thickness of 1.6 mm was prepared and used as a test piece. Table 1 shows the results of the following characteristic tests.

I Peel strength test (peel width
(1 mm, in accordance with JIS-C-6481) Peel strength (unit: kN / m) after lamination was measured. II Rust resistance test The temperature was changed at a temperature of 20 to 60 ° C. in a 12-hour cycle, and the degree of discoloration of the copper foil surface was observed for two days in a thermo-hygrostat at 85% humidity. X: Evaluated as markedly discolored.

Example 2 An aqueous solution containing 1 g / l of γ-glycidoxypropyltrimethoxysilane at a temperature of 25 ° C. was sprayed on an aluminum layer of the copper foil prepared in Example 1 at a temperature of 25 ° C. for 10 seconds for 5 seconds.
/ ^M was ² coating process. Immediately after the treatment, the film was guided into a hot air dryer set to a temperature of 100 ° C. and dried for 5 minutes to form an organic film layer (250 nm thick) on the side of the copper foil to be bonded (the outermost surface). Table 1 shows the evaluation results of the produced copper foils.

Example 3 5 g of aluminum sulfate 14-18 hydrate and 1 g of zinc sulfate heptahydrate were dissolved in water to make 1 liter.
8. A plating bath having a bath temperature of 30 ° C. was prepared. Using this plating bath, a copper foil whose one surface was roughened in advance was immersed in the same manner as in Example 1, and a cathodic treatment was performed on the roughened surface side of the copper foil at a current density of 0.3 A / dm ² and a conduction time of 3 seconds. And a zinc-aluminum layer. Immediately after the cathode treatment, the copper foil was taken out of the plating solution, washed with water, and dried in a drier maintained at a temperature of 100 ° C. The zinc-aluminum layer was analyzed for the amount of the deposited metal by an ICP analyzer. The amount of the deposited aluminum was 5 μg / dm ² , and the amount of the deposited zinc was 23.8 μm.
g / dm ² . Table 1 shows the evaluation results of the produced copper foils.

Comparative Example 1 An electrolytic copper foil (thickness: 18 μm) which had been roughened on one side in advance and which had not been subjected to a surface treatment used in Example 1 was used.
A characteristic test was performed in the same manner as described above. Table 2 shows the evaluation results of the copper foil.

Comparative Example 2 3.5 g of sodium bichromate dihydrate was dissolved in water to make 1 liter, and a plating bath having a pH of 4.7 and a bath temperature of 30 ° C. was prepared. Using this plating bath, a copper foil whose one surface was roughened in advance was immersed in the same manner as in Example 1, and a cathode treatment was performed on the roughened surface side of the copper foil at a current density of 0.5 A / dm ² and a conduction time of 5 seconds. A chromate layer was formed. Immediately after the cathodic treatment, the copper foil was taken out of the plating solution and washed with water.
In a drying oven held at room temperature. Further, when the amount of plating metal deposited on the chromate layer was analyzed by an ICP analyzer, the amount of chromium deposited was 40 μg / dm ² . Table 2 shows the evaluation results of the produced copper foils.

Comparative Example 3 An aqueous solution containing 1 g / l of γ-glycidoxypropyltrimethoxysilane at a temperature of 25 ° C. at a temperature of 25 ° C. was sprayed on the chromate layer of the copper foil prepared in Comparative Example 5 for 10 seconds at a rate of 5 seconds.
m was ² coating process. Immediately after the treatment, the film was guided into a hot air dryer set to a temperature of 100 ° C. and dried for 5 minutes to form an organic film layer (250 nm thick) on the side of the copper foil to be bonded (the outermost surface). Table 2 shows the evaluation results of the produced copper foils.

Comparative Example 4 30 g of zinc sulfate heptahydrate and 100 g of sodium hydroxide
Was dissolved in water to 1 liter to prepare a plating bath.
Using this plating bath, a copper foil whose one surface was roughened in advance was immersed in the same manner as in Example 1, and a current density of 20 A /
Anodizing was performed at dm ² for 5 seconds to form a zinc layer. Immediately after the anodization, the copper foil was taken out of the plating solution, washed with water, and dried in a drier maintained at a temperature of 100 ° C. Table 2 shows the evaluation results of the produced copper foils.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

By producing a printed wiring board using the copper foil obtained by the method of the present invention, it is possible to generate a chromium-containing waste liquid in the production process of the printed wiring board without impairing the characteristics of the printed wiring board, and Provided is a printed wiring board which can eliminate chromium elution from waste including printed wiring boards such as electric products.

Continued on the front page F term (reference) 4E351 BB01 BB24 BB30 BB38 CC06 DD04 DD08 DD31 DD56 GG01 GG13 4K024 AA05 AB01 AB12 BA09 BB11 BC02 DA07 DB03 GA04 GA12 GA16 5E343 BB16 BB22 BB24 BB59 BB67 CC78 EE52 GG02GG

Claims (2)

[Claims] 1. A copper foil for a printed wiring board, comprising a layer made of aluminum oxide or a layer made of metal zinc and aluminum oxide on at least one surface of the copper foil. 2. Using a plating bath containing aluminum ions or a plating bath containing zinc ions and aluminum ions, subjecting the copper foil to a cathode treatment in the plating bath, and forming a layer made of aluminum oxide on at least one surface of the copper foil. Alternatively, a method for producing a copper foil for a printed wiring board, comprising forming a layer composed of zinc metal and aluminum oxide.