JP2537108B2 - Copper foil for printed circuit and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed circuit copper foil and a method for producing the same, and more particularly to a printed circuit copper foil having an excellent heat-resistant discoloration coating on the copper foil surface and a method for producing the same. Is.

[0002]

2. Description of the Related Art Generally, as is well known, the surface of copper is gradually oxidized in the atmosphere and loses its original copper-colored luster with the passage of time to turn brown. Under a heating atmosphere, the oxidation is further promoted to form blackish brown copper oxide. Therefore, in a copper product, a copper surface that has lost its original copper color and is discolored means a significant decrease in its commercial value. In particular, in the case of printed circuit copper foil that is often used as a conductor material for printed wiring boards, the presence of a copper oxide layer on the surface not only impairs the quality of appearance, but is also required for printed circuit copper foil. It is a factor that deteriorates properties such as solder spreadability and adhesiveness with resist ink. Particularly, the heat discoloration resistance of the copper foil surface in a high temperature atmosphere is one of the important required characteristics of the copper foil for printed circuits.

Conventionally, various methods have been proposed as a method for imparting heat discoloration resistance, that is, an antioxidant power, to a copper foil surface. For example, JP-B-51-42575 proposes a method of forming a so-called chromate layer by immersing a copper foil in an aqueous solution containing hexavalent chromium ions and subjecting the foil surface to cathodic treatment. However, when a copper foil having a chromate layer is used to heat and pressurize a resin base material to produce a copper-clad laminate, the chromate layer is destroyed by the influence of heat and the copper foil surface is oxidized. , Turn brown. Therefore, it is difficult to expect a good thermochromic property from the formation of the chromate layer.

It is generally well known to form a zinc film on the surface of copper using a plating solution containing zinc ions. For example, in Japanese Examined Patent Publication No. 54-29187, a dense surface containing Zn and Cu is formed on the surface of copper by immersing copper in an alkaline aqueous solution containing zinc ions or by energizing copper in this alkaline aqueous solution as an anode. A method of forming a simple oxide layer has been proposed. The copper foil having a zinc coating thus obtained can retain heat discoloration much better than a copper foil coated with a chromate layer. However, even in the copper foil having this zinc coating, if the thickness of the zinc coating is relatively thin in an atmosphere exceeding 200 ° C., sufficient heat discoloration resistance cannot be obtained. On the other hand, if the thickness of the zinc coating is increased. However, due to mutual thermal diffusion of zinc and copper, a brass layer which is an alloy of the two forms a brass layer, and a yellow hue is strongly developed on the copper foil surface, so that a desirable appearance cannot be obtained.

JP-A-52-735 discloses that a smooth glossy surface of a copper foil is electroplated with zinc and then heat-treated under the condition that a brass layer is formed by mutual diffusion of zinc and copper. It has been proposed to form a brass layer on. Also in this method, as described above, the yellow tint of the brass layer is strongly developed on the copper foil surface, and there is a problem in appearance.

Further, Japanese Patent Publication No. 61-33906 discloses a method of forming a zinc coating on both surfaces of a copper foil and then forming a chromium oxide coating on each zinc coating. However, the copper foil obtained by this method is also 200
When exposed to a high temperature atmosphere exceeding ° C, the heat discoloration resistance was remarkably lowered and discolored, which was a practical problem.

Japanese Patent Publication No. 58-7077 discloses a method of forming a mixture coating layer made of zinc or zinc oxide and chromium oxide on at least one surface of a copper foil. When exposed to a high temperature atmosphere exceeding ℃, the degree of discoloration becomes significantly large, which is a practical problem.

Japanese Patent Publication No. 51-35711 proposes a method of forming an electrodeposited metal layer of a metal selected from the group consisting of zinc, indium and brass on one surface of a copper foil layer. However, the copper foil coated with the electrodeposited indium layer has a low heat discoloration resistance, and the indium layer itself has a grayish white color when the amount of deposited indium is increased. Similar to the above, the copper foil coated with the electrodeposited zinc layer or the electrodeposited brass layer has a problem that the heat discoloration resistance is low.

[0009]

The object of the present invention is 20
The copper foil surface is not discolored even if it is subjected to a high temperature heat history of more than 0 ° C and has excellent heat discoloration resistance, and the solder spreadability required for printed circuit copper foil, the adhesion with resist ink, etc. It is an object of the present invention to provide a copper foil for a printed circuit capable of maintaining good characteristics and a manufacturing method capable of continuously mass-producing the copper foil.

[0010]

The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, in a film containing both indium and zinc, the antioxidative power of the copper foil surface is synergistic. The present invention has been completed and the present invention has been completed. That is, the present invention provides a copper foil for a printed circuit, which has an indium-zinc layer on at least one surface of the copper foil. The printed circuit copper foil of the present invention can be easily manufactured by the manufacturing method of the present invention described below.

The indium-zinc layer in the copper foil for a printed circuit of the present invention is an alloy thin film mainly composed of metals of indium and zinc, and firmly adheres to the copper foil surface of the base.
A small amount of indium and zinc oxides and hydroxides may be mixed near the surface layer of the indium-zinc layer. This indium-zinc layer itself is a colorless and transparent dense film and does not impair the copper color of the base material. Further, even under a high-temperature heating atmosphere, it does not discolor, and it is possible to exert an extremely excellent function of preventing oxidation while maintaining the copper color of the copper foil surface.

The deposition amount converted as the metal amount of indium and zinc constituting the indium-zinc layer and the ratio thereof will be described. The deposition amounts of indium and zinc are both in the range of ^{20 to} 150 μg / dm ^2. It is preferable. When the content is less than 20 μg / dm ^2, the heat discoloration resistance may decrease due to the thin film thickness.
When it exceeds 150 μg / dm ² , the indium-zinc layer may have a dull gray-white color tone depending on the ratio of both. Particularly preferably, the adhered amount of each is 40 to 130 μg / dm ² .

The ratio of the amount of indium to zinc in the indium-zinc layer is preferably 25 to 75% by weight based on the total amount of indium and zinc. Outside this range, the synergistic effect of heat discoloration at high temperature, which is caused by both, may be attenuated. It is particularly preferably in the range of 35 to 70% by weight. Regarding the thickness of the indium-zinc layer, when converted using the specific gravity of zinc of 7.12, it is usually about 0.000.
It is 5 to 0.004 μm.

Means for producing a copper foil for a printed circuit according to the present invention by forming an indium-zinc layer on a copper foil surface includes:
Known electroplating methods, chemical plating methods, vacuum deposition methods, sputtering methods, metallikon methods and the like can be used. Among them, it is practically desirable to carry out the cathode electrolysis treatment by the electroplating method in terms of mass productivity and economical efficiency. The production method of the present invention uses this electroplating method. A plating bath containing indium ions and zinc ions is used, a copper foil is subjected to cathodic treatment in the plating bath, and at least one surface of the copper foil is made of indium. It is characterized by forming a zinc layer.

The copper foil used in the method of the present invention is
Typical examples are electrolytic copper foils and rolled copper foils, but they are not particularly limited. The thickness of the copper foil is not particularly limited as long as it has a thickness used as a copper foil for printed circuits. In the present invention, it is preferable to use a copper foil having at least one surface roughened in order to increase the peeling strength of the surface to be adhered to the resin base material after lamination.

Next, the message used in the method of the present invention.
Regarding the bath, the metal iodide contained in the plating bath
The ions are indium ions and zinc ions. indium
As an example of the ion source, In₂(SO_Four)₃, I
nCl₃, In (SO₃NH₂) 3, In (BF_Four)₃ Or
These hydrates and the like are suitable. With zinc ion source
Then ZnSO_Four, ZnCl₂, Zn (CH₃COO)₂
 Alternatively, these hydrates and the like are suitable. Also, the present invention
Other metal ions within the range that does not hinder the achievement of the purpose of
May be included in small amounts.

A plating bath is prepared by dissolving at least one indium ion source and at least one zinc ion source in water. When setting the content of both metal ions in the plating bath, it is determined in consideration of the amount of plating metal deposited, the current density, the energization time, etc., but usually in the range of 0.1 to 50 g / l, respectively. You can choose. Preferably, each is 0.5 to 10 g / l
Is. For example, In ₂ (S
O ₄ ) ₃ and ZnSO ₄ · 7H _{2 as the} zinc ion source
When O is used, it is particularly preferably used in the range of 0.1 to 10 g / l.

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

A copper foil is dipped in this plating bath and an electric current is applied with the copper foil as a cathode to form an indium-zinc layer on the copper foil surface. The current density and energization time cannot be specified in a lump because they relate to other conditions such as the amount of metal ions, the amount of plated metal and the ratio thereof, but usually the current density is 0.1 to 10 A / dm ² , preferably Is 0.2-2
A / dm ² , energization time 1 to 60 seconds, preferably 1 to 30
It is desirable to appropriately select from the range of seconds.

If necessary, a copper foil having at least one surface roughened is subjected to a water washing step, and is placed opposite to one or both surfaces of the copper foil in the plating bath containing indium ions and zinc ions prepared as described above. The indium-zinc layer is formed by providing an insoluble anode and subjecting one side, preferably the glossy side, or both sides of the copper foil under the above-mentioned electrolysis conditions to form an indium-zinc layer, thereby producing the copper foil for a printed circuit of the present invention.

In carrying out the production method of the present invention, for example, a copper foil wound into a coil having a predetermined thickness and width is provided as necessary with a degreasing tank, a pickling tank, a water washing tank, Roughening treatment copper plating tank, followed by a water washing tank, then a plating tank for forming an indium-zinc layer, a water washing tank and a copper foil processing apparatus consisting of a configuration in which a drying device and the like are connected, run at a constant speed, continuously It is preferable to manufacture by winding.

The copper foil for a printed circuit of the present invention thus obtained is formed into a printed circuit copper-clad laminate by thermocompression bonding to a resin substrate such as a phenol resin, an epoxy resin, or a polyimide resin, and is subjected to a predetermined processing operation. After that, it is used as a printed circuit board.

[0023]

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 In ₂ (SO ₄ ) ₃ 0.5 g / l and ZnSO ₄ .7H ₂
Dissolve 2.0 g / l of O in water, pH 3.0, liquid temperature 3
A plating bath prepared at 0 ° C was prepared. Using this plating bath, electrolytic copper foil (thickness: 35μ
m) is immersed, and the current density is 0.5 A / d on the shiny side of the copper foil.
Cathode treatment was carried out at m ² for 2 seconds for energization to form an indium-zinc layer. Immediately after the cathode treatment, the copper foil was taken out of the plating solution, washed with water, and then dried in a dryer maintained at a temperature of 100 ° C. The color tone of the copper foil surface on which the indium-zinc layer was formed had a copper color similar to that before the electrolytic treatment. In addition, the plating metal deposition amount of the indium-zinc layer is
When analyzed with a C analyzer, the amount of indium metal is 75
μg / dm ^2, the zinc metal content was 55 [mu] g / dm ^2.

Next, in order to perform the following characteristic test, the obtained copper foil with an indium-zinc layer was laminated on a FR-4 grade epoxy resin-impregnated glass cloth substrate with the rough surface in contact with the substrate surface, Heat and pressure treatment under conditions of temperature 168 ° C., pressure 80 kg / cm ² , 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. The results of the following characteristic tests are summarized in Table 1 and Table 2
It was shown to.

(1) Heat discoloration resistance The degree of discoloration of the copper foil surface of the test piece immediately after lamination and 180 ° C.
1 hour, 200 ° C 1 hour, 250 ° C 1 hour, 300 ° C 1
The degree of discoloration of the copper foil surface when heat-treated in a constant temperature bath maintained under each condition for 0 minutes was visually observed.
・ ・ ・ Slightly discolored, × ... Remarkably discolored. (2) Solder Spreadability Test Using a solder of 60Sn (symbol H60B) specified in JIS Z 3282, JIS Z 3197, 4-
According to the spread test method specified in 11, the solder spread ratio was measured for each test piece after lamination. Spread rate (%) = {(D−H) / D} × 100 (H; height of spread solder (mm) D; diameter of solder used in the test as a sphere (m
m) and a value calculated from D = 1.24V ^1/3 , where V = solder mass / specific gravity) The spread ratio obtained by the above formula is: ・ ・ ・ Spread ratio 90 to 95% △ ・-Spread rate 85-89% x ... Spread rate was evaluated as 84% or less. (3) Resist ink adhesion test After the test piece was washed with trichlene, UV ink (UR-450B, Tamura Corporation) was formed on the indium-zinc layer.
To form a circuit-shaped UV ink coating film by screen printing (screen used: nylon, mesh 200 to 300 mesh), and the UV ink coating film is formed by a UV device (model HMW-713, manufactured by Oak Manufacturing Co., Ltd.). After curing by irradiation, it is immersed in a 10% HCl aqueous solution at a temperature of 50 ° C. for 5 minutes, washed with water, and then air-dried, and the hardness of the cured coating film on the test piece is measured by JI.
It measured based on the pencil method prescribed | regulated by SC3002. ○ ・ ・ ・ Pencil hardness 2H or more △ ・ ・ ・ Pencil hardness F to H × ・ ・ ・ Pencil hardness B or less

Examples 2 to 6 The same operation as in Example 1 was carried out except that the same copper foil as that used in Example 1 was used and the plating bath having the composition concentration shown in Table 1 and the electrolysis conditions were used. A copper foil having a zinc layer was manufactured. These copper foils were analyzed for the amount of deposited metal and various characteristic tests were carried out in the same manner as in Example 1, and the results are collectively shown in Tables 1 and 2.

Comparative Examples 1 to 5 The same operation as in Example 1 was performed except that the same copper foil as that used in Example 1 was used and the plating bath having the compositional concentration shown in Table 1 and the electrolysis conditions were used. Formed copper foil (Comparative Examples 1 and 2), and a zinc layer formed copper foil (Comparative Examples 3 and 4)
A copper foil (Comparative Example 5) having a zinc-chromium layer formed thereon was manufactured. These copper foils were analyzed for the amount of deposited metal and various characteristic tests were carried out in the same manner as in Example 1, and the results are collectively shown in Tables 1 and 2.

Examples 1 to 6 are copper foils on which the indium-zinc layer of the present invention is formed. The color tone of the copper foil surface after cathodic treatment is controlled by keeping the plating metal amounts of indium and zinc within a suitable range. It exhibits the same copper color as before treatment, and also shows excellent heat discoloration resistance with respect to each temperature condition without discoloration as shown. Especially 300
It has been found that it does not discolor even with a high thermal history of ℃, and exhibits excellent heat discoloration resistance even in an extremely high temperature atmosphere. Also, good results are shown for solder spreadability and resist ink adhesion. On the other hand, Comparative Example 1
And Comparative Example 2 is a copper foil having an indium layer formed,
The effect of heat discoloration resistance is not obtained. Comparative Example 2 is an example in which an indium layer having a larger amount of deposited indium than Comparative Example 1 was formed, but the copper foil surface after the plating treatment was grayish white,
When this was heated, it turned black. Comparative Examples 3 and 4 are copper foils having a zinc layer formed thereon. In Comparative Example 3, the heat discoloration resistance started to decrease from around 200 ° C., and the color changed to brown. Further, Comparative Example 4 is a case where a zinc layer having a larger zinc deposition amount than that of Comparative Example 3 is formed, and exhibits a brass color when heated, and any practical problems cannot be avoided. Comparative Example 5 is a copper foil on which a chromium-zinc layer is formed.
The degree of discoloration tended to increase from around 00 ° C.

Therefore, the above-mentioned indium of the present invention
It was found that the copper foil having the zinc layer was excellent in the results of each characteristic test. This is because, due to the synergistic effect of both indium and zinc, a completely different property from the case where a layer of indium alone or a layer of zinc alone is formed is expressed, and it is particularly advantageous for heat discoloration resistance. Conceivable. Chromate layer (C
When an r amount of 5 to 80 μg / dm ² ) is formed by immersion treatment or electrolytic treatment, the effect of suppressing the occurrence of rust and discoloration after humidification (40 ° C., 90% for 3 days) can be obtained.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

As is apparent from the above description, the copper foil for a printed circuit according to the present invention has an extremely beautiful appearance and has no heat discoloration even if exposed to a high temperature atmosphere. In addition, it has excellent bondability with solder, which is indispensable for copper foil for printed circuits, and adhesion with resist ink. Further, since the method of the present invention does not use a harmful hexavalent chromium compound in the manufacturing process, there is no possibility of causing a problem of contamination of working environment. In addition, there is no problem in terms of manufacturing control, and its industrial value is extremely large.

Claims (2)

(57) [Claims] 1. A copper foil for a printed circuit, which has an indium-zinc layer on at least one surface of the copper foil. 2. A copper foil for a printed circuit, which comprises using a plating bath containing indium ions and zinc ions and subjecting the copper foil to cathodic treatment in the plating bath to form an indium-zinc layer on at least one surface of the copper foil. Method.