JP2003298229A - Copper foil for printed wiring board and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide copper foil for printed wiring board that can be dissolved by an alkali etchant and, in addition, is excellent in chemical resistance and heat resistance, and to provide a method of manufacturing the foil. <P>SOLUTION: This copper foil has a cobalt and/or nickel layer containing germanium on at least its one surface, a chromate coating film layer on the cobalt and/or nickel layer, and a silane coupling agent layer on the coating film layer. In the method of manufacturing the copper foil, the chromate layer is formed on the cobalt and/or nickel layer containing germanium after the cobalt and/or nickel layer is formed by cathodically electrolyzing the copper foil in an electrolytic solution containing germanium and cobalt and/or nickel. In addition, the silane coupling agent layer is provided on the chromate coating film layer. <P>COPYRIGHT: (C)2004,JPO

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 printed wiring board and a method for producing the same, more specifically, a cobalt and / or nickel layer containing germanium is provided on at least one surface of the copper foil. By providing a chromate film layer on this layer and further providing a silane coupling agent layer on the chromate film layer, it becomes soluble in an alkaline etching solution, and high density wiring with excellent chemical resistance and heat resistance is obtained. The present invention relates to a suitable copper foil for printed wiring board.

Printed wiring boards are widely used in various electric devices such as personal computers and mobile phones that require high-density wiring, but the recent development speed in this field is much faster than other industrial fields. As a result, the quality required for printed wiring boards is also increasing.

[0003]

2. Description of the Related Art As a method for manufacturing a printed wiring board, there are an additive method and a subtractive method, but the former does not use a copper foil at the time of forming a circuit, whereas the latter prints a circuit after forming a copper-clad laminate, This is the most popular method of removing unwanted parts by etching. The required characteristics for the surface of the copper foil used in the printed wiring board to adhere to the base material are:
A wide variety of, but particularly important characteristics are the following three points. Sufficient peel strength from the base material. The peel strength should be sufficient even after a severe test (chemical treatment, long-term heat treatment). High reliability of the insulation characteristics due to the narrowing of the density of printed wiring boards. (Accuracy of etching)

Particularly in recent years, halogen-free base materials, glass polyimide base materials, high Tg base materials, etc. have been frequently used in addition to the glass epoxy base materials (FR-4) which are usually used frequently, and required characteristics for copper foil. Is becoming more and more severe.

As a general means for satisfying the above characteristics, first, there is a surface roughening treatment on an untreated copper foil obtained by cathodic electrolysis from a sulfuric acid and copper sulfate bath. Roughening treatment is cathodic electrolysis of at least one surface of untreated copper foil in sulfuric acid and an aqueous solution of copper sulfate at a limiting current density or higher to deposit copper protrusions, and further copper or copper alloy on the layer. The cover plating is applied. This roughening treatment increases the roughness of the copper foil surface, resulting in a higher mechanical anchoring effect,
The peeling strength increases dramatically. However, the problem solved by this roughening treatment is only the above-mentioned required properties of copper foil, and after the severe test (especially after the long-time heating test)
It is not possible to suppress the deterioration of the peeling strength.

Therefore, in order to prevent the reaction between the base resin and the copper foil on the surface-roughening treatment, a coating barrier of a dissimilar metal or a copper alloy is applied or various anticorrosion treatments are applied. For example, in Japanese Examined Patent Publication No. S51-35711, a copper foil surface is coated with a layer selected from the group consisting of zinc, indium, brass, etc., and in Japanese Examined Patent Publication No. S53-39376, two electrodeposited copper layers are provided. Further coating a layer of a metal having no chemical activity on the substrate to be adhered, such as zinc, brass, nickel, cobalt, chromium, cadmium, tin, and bronze.

Further, in Japanese Patent Publication No. 2-51272, spherical or dendritic zinc is deposited, and this layer is formed of copper, arsenic,
Coating with one or more of bismuth, brass, bronze, nickel, cobalt, or zinc, or an alloy thereof, and Japanese Patent Publication No. 6-54829 discloses a cobalt plating layer or cobalt and nickel on the surface of a copper foil after copper roughening treatment. It has been proposed to form a plating layer consisting of, and further apply a single coating of chromium oxide or a coating of chromium oxide and zinc and / or zinc oxide. However, these conventional coating barrier layers have the following problems.

When a copper foil having a layer mainly containing zinc such as zinc, brass, and zinc-nickel is applied to a printed circuit, the adhesive surface between the copper foil and the base material and its vicinity have very weak hydrochloric acid resistance. , In the manufacturing process of printed wiring boards, the corrosion resistance of the interface part is weak while being pickled and immersed in various active treatment liquids, so the peel strength deteriorates, especially the recent narrow conductor width. In the case of a circuit, there is a drawback that the conductor may be peeled or dropped due to thermal shock or mechanical shock. Further, cupric chloride etching has a drawback that undercutting occurs due to the weak adhesion surface between the copper foil and the base material.

Nickel and tin are excellent in chemical resistance and heat resistance,
Although it is soluble in commonly used ferric chloride and cupric chloride etching solutions, it is insoluble in alkaline etching solutions often used in pattern plating and the like,
It has a serious drawback that it causes an etching residue (stain) that impairs electrical insulation. When considering the narrowing of circuits in recent years, it is of course essential that fine patterns can be drawn with ferric chloride and cupric chloride, but alkali etching is also an essential condition due to the wide variety of resists.

Further, in the case of the cobalt single layer, the alkali etching property is good, but there is a problem in chemical resistance though it is not as much as zinc, and brass plating is the only practical method from the cyanide bath. There are problems such as having big problems in terms of environment and work.

Further, a cobalt plating layer or a plating layer composed of cobalt and nickel is formed on the surface of the copper foil after the copper roughening treatment, and further, a single coating of chromium oxide or chromium oxide and zinc and / or zinc oxide is formed. The treated copper foil has good hydrochloric acid resistance, but is weak in the cyanide bath used in the gold plating process and causes undercutting. Further, it is very difficult to satisfy both the cyan resistance and the alkali etching property at the same time, as it becomes insoluble in the alkali etching solution when the nickel content is increased to suppress the undercutting.

As described above, it has been difficult to simultaneously satisfy the non-reactivity with the base resin and the chemical resistance of the barrier layer proposed hitherto, and it is sufficiently satisfied with the rapid densification and diversification of printed wiring boards. Not done.

[0013]

DISCLOSURE OF THE INVENTION It is an object of the present invention to provide a copper foil for printed wiring boards which is soluble in an alkaline etching solution and has excellent chemical resistance and heat resistance, and a method for producing the same. To do.

[0014]

Therefore, as a result of examining various copper foil treatment methods in order to solve all the problems in the prior art, the inventor of the present application contains germanium on at least one surface of the copper foil. It was found that it is effective to have a cobalt and / or nickel layer, and to have a chromate film layer on the layer, and further to apply a silane coupling agent layer on the chromate film layer. The invention was completed.

That is, the present invention has a cobalt and / or nickel layer containing germanium on at least one surface of a copper foil, and a chromate film layer on the layer, and a silane film on the chromate film layer. A copper foil for a printed wiring board, which is characterized by forming a coupling agent layer, and an electrolytic solution containing germanium, cobalt and / or nickel is used to perform cathodic electrolysis of the copper foil in the electrolytic solution to form a cobalt containing germanium. And / or after forming a nickel layer, a chromate film layer is provided on the layer, and a silane coupling agent treatment is further performed to provide a silane coupling agent layer, which is a method for producing a copper foil for a printed wiring board. Is.

The germanium-containing cobalt and / or nickel layer of the present invention cannot be used as a barrier layer when a single or binary alloy layer lacking germanium is used.・ In the case of a single layer of cobalt, the peel strength after heat treatment for a long time does not deteriorate much, but
The chemical resistance is poor and undercutting occurs after immersion in a hydrochloric acid or cyanide bath. -In the case of a nickel single layer, hydrochloric acid resistance and cyanation resistance are good, but alkali etching resistance is poor and strong stains occur.・ In the case of a single layer of germanium, it cannot be precipitated alone from the aqueous solution. Germanium is an inductive precipitation type of the iron group, and in the present invention, it does not precipitate without cobalt and / or nickel. In the case of a cobalt-nickel layer, there is little deterioration in peel strength after heat treatment for a long time, and although hydrochloric acid resistance is good, both cyan resistance and alkali etching resistance cannot be satisfied at the same time.

As described above, the single and binary alloy layers that do not contain germanium have their respective drawbacks. Alkali etching is performed by forming a binary or ternary alloy layer containing germanium-containing cobalt and / or nickel. A copper foil for printed wiring boards that is soluble in liquid and has chemical resistance and heat resistance.

Further, by providing a chromate film layer on the barrier layer of the present invention, various properties are improved, for example, oxidation resistance is improved, and peel strength is increased in order to improve adhesive strength with a substrate. The effect of improving brown transfer resistance (discoloration, coloring, and stains on the surface of an etching substrate that occurs in a printed circuit using a glass epoxy resin). The bath for forming the chromate film layer may be a known bath, for example, a bath containing hexavalent chromium such as chromic acid, sodium dichromate, potassium dichromate, etc. Given by.

The chromic acid solution may be alkaline or acidic. The above-mentioned two types of chromic acid solutions have advantages and disadvantages respectively and may be used properly according to the purpose of use, but when an alkaline chromic acid solution is used, the corrosion resistance of the chromate film layer is slightly inferior to that of the acidic chromic acid solution. Although there is a drawback that the adhesiveness with the bonding base material is slightly inferior, the above-mentioned problems do not occur even if a chromate film layer is formed on the barrier layer of the present invention with an alkaline chromic acid solution.

As the alkaline chromic acid solution, an alkaline zinc chromate solution containing zinc ions and hexavalent chromium ions as described in JP-B-58-15950 may be used. By using this chromic acid solution, It is possible to improve the oxidation resistance as compared with the chromate film layer formed from the chromium alone acid solution. Of course, even if an acidic chromic acid solution is used, similar results can be obtained.

Further, by applying a silane coupling agent layer on the chromate film layer, not only the peel strength in the normal state can be improved but also the deterioration of the peel strength after the severe test can be suppressed. The copper foil for printed circuits has improved versatility by improving oxidation resistance. There are various types of silane coupling agents such as epoxy groups, amino groups, mercapto groups, vinyl groups, methacryloxy groups, styryl groups, etc., but they have different characteristics and also have compatibility with the base material, so it is necessary to select and use them. There is. The silane coupling agent layer is formed as an aqueous solution by immersion treatment or spray treatment.

The barrier layer of the present invention can be used regardless of the type of electrolytic copper foil or rolled copper foil as long as it is a copper foil used as a normal copper foil for printed wiring boards. The layer needs to be treated to the extent that the copper foil properties are not impaired (adhesion strength to the substrate is not reduced), but the preferred treatment amount is 1 mg / m ^2.
To 500 mg / m ² , more preferably 3 mg / m
² to 300 mg / m ² . When the cobalt and / or nickel layer containing germanium is 1 mg / m ² or less, the barrier effect of the present invention cannot be sufficiently exhibited, while
When the amount is 500 mg / m ² or more, problems such as a decrease in copper purity, an increase in cost and uneconomical problems occur.

The cobalt and / or nickel layer containing germanium according to the present invention may include cobalt, nickel,
A preferable content of germanium is (wt% = weight%) In the case of a cobalt-germanium layer, 30 wt% ≦ cobalt ≦ 80 wt% 20 wt% ≦ germanium ≦ 70 wt%, and more preferably 35 wt% ≦ cobalt ≦ 75 wt% 25 wt% ≦ germanium ≦ 65 wt%.

In the case of nickel-germanium layer 30 wt% ≤ nickel ≤ 65 wt% 35 wt% ≤ germanium ≤ 70 wt% And more preferably 35 wt% ≤ nickel ≤ 60 wt% 40 wt% ≤ germanium ≤ 65 wt% Is.

In the case of a cobalt-nickel-germanium layer, 15 wt% ≤ cobalt ≤ 70 wt% 10 wt% ≤ nickel ≤ 40 wt% 5 wt% ≤ germanium ≤ 55 wt%, more preferably 20 wt% ≤ cobalt ≤ 65 wt% 13 wt% ≤ nickel ≤ 35wt% 7wt% <germanium <52wt%.

When the content of each element in the above three kinds of barrier layers is within the above range, the copper foil for printed wiring board has very good characteristics, but when it is out of this range, the following drawbacks occur. Occur.

When the content of each element in the cobalt-germanium layer is outside the above content, the chemical resistance becomes poor, and undercutting occurs after immersion in a hydrochloric acid or cyanide bath. When the content of each element in the nickel-germanium layer is out of the above content, alkali etching properties and chemical resistance are deteriorated. When the content of each element in the cobalt-nickel-germanium layer is out of the above content, alkali etching properties and chemical resistance are deteriorated.

The barrier layer may be formed on the surface of the copper foil by various methods such as known electroplating method, vacuum deposition method, sputtering method and the like, which is considered to be most suitable for the industrial line. Is an aqueous solution electroplating method. The manufacturing method is germanium and cobalt and / or
Alternatively, it is obtained by subjecting a copper foil to cathodic electrolysis in an electrolytic solution containing nickel. Examples of plating electrolytes include various tartaric acid, oxycarboxylic acid baths such as citric acid, pyrophosphoric acid baths, acetic acid baths, cyanide baths, etc., but cost, bath management, pollution resistance,
A citric acid bath or the like is suitable in consideration of workability, etc., but is not particularly limited thereto.

The following sources can be used as the supply sources of cobalt, nickel and germanium. However, it is not limited to this.

Sources of cobalt ions include cobalt sulfate, ammonium cobalt sulfate, cobalt citrate,
Cobalt acetate etc. can be used. Nickel sulfate, nickel ammonium sulfate,
Nickel chloride, nickel acetate, etc. can be used. It is recommended to use germanium dioxide as a source of germanium ions. Since this germanium dioxide is difficult to dissolve in a low temperature to normal temperature bath, it is desirable to dissolve it in a bath at 40 ° C. or higher.

Further, sodium sulfate may be added to the bath of the present invention to impart conductivity. The bath temperature is not particularly specified, but in view of economy and work, it is preferably from room temperature to about 50 ° C. The current density can be used in a wide range from 0.1 to 10 A / dm ² , but when considering the actual process as well,
1 to 5 A / dm ² position is preferable. The pH is preferably about 4 to 10, and within this pH range, the simultaneous precipitation of the three elements, barrier properties, and workability are all good, but this is not limited to the above conditions either. Further, it is preferable to use an insoluble anode such as platinum as the anode.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION Examples and comparative examples of the present invention are shown below.

[0033]

EXAMPLES (Examples 1 to 18) 35 μm electrolytic copper foil roughened by a known method was prepared in advance, the temperature of the bath of the present invention was kept constant at 30 ° C., and the bath composition and pH (Table 1) The surface of the copper foil was subjected to cathodic electrolysis using platinum as an anode under sulfuric acid and sodium hydroxide) and electrolytic conditions, and a cobalt-germanium layer (Examples 1 to 6) and a nickel-germanium layer (Examples 7 to 12) were used. ), A cobalt-nickel-germanium layer (Examples 13 to 18) was formed, followed by washing with water, and then a chromate film layer was formed on the layer. The composition of the chromic acid solution having the chromate film layer formed thereon and the electrolysis conditions are shown below. Sodium dichromate 5g / L Bath temperature 30 ℃ pH (adjusted with sodium hydroxide) 13.0 Current density 2A / dm ² Electrolysis time 5 seconds Anode platinum

After the chromate film layer was formed in the above alkaline chromic acid bath, it was washed with water and then a silane coupling agent layer was formed. The silane coupling agent species, the bath composition and the forming method for forming the silane coupling agent layer are shown below. γ-Aminopropyltriethoxysilane 1.5 mL / L Bath temperature 30 ° C. Immersion time 15 seconds After forming a silane coupling agent layer in the above silane coupling agent bath, it was dried. Next, this copper foil was laminated and molded on an FR-4 grade epoxy resin-impregnated glass substrate, and each characteristic test of the copper-clad laminate was performed. The results are shown in Table 2.

[0035]

[Comparative Example] (Comparative Example 1) The same 35 μm electrolytic copper foil as in Example was prepared, and as shown in Table 1, cobalt sulfate heptahydrate 30 g / L trisodium citrate dihydrate 30 g / L. The pH (adjusted with sodium hydroxide) was adjusted to 5.9, and the above 35 μm electrolytic copper foil was heated to a bath temperature of 30 in this bath.
° C., a current density of 2A / dm ^2, except that 3 seconds cathodic electrolysis electrolysis time performs the same processing steps as in Example 1 to 18, molding the copper-clad laminate in the same manner, was subjected to the property tests in the same way . The results are shown in Table 2.

(Comparative Example 2) A 35 μm electrolytic copper foil similar to that of the embodiment was prepared, and a cathode electrolysis was carried out under the same bath composition and bath conditions as in Comparative Example 1 with a current density of 1 A / dm ² and an electrolysis time of 5 seconds. 1
The same treatment steps as those of Nos. 18 to 18 were performed, a copper clad laminate was formed by the same method, and each characteristic test was performed by the same method. The results are shown in Table 2.

(Comparative Example 3) A 35 μm electrolytic copper foil similar to that of the Example was prepared, and as shown in Table 1, nickel sulfate hexahydrate 30 g / L trisodium citrate dihydrate 30 g / L pH. (Adjust with sulfuric acid) 4.5 and in this bath, the bath temperature of the above 35 μm electrolytic copper foil is 30
° C., a current density of 1.5A / dm ^2, except that the electrolytic time 2 seconds and cathodic electrolysis is carried out the same processing steps as in Example 1 to 18, molding the copper-clad laminate in the same way, the characteristics tested in the same way went. The results are shown in Table 2.

(Comparative Example 4) A 35 μm electrolytic copper foil similar to that of the Example was prepared, and as shown in Table 1, nickel sulfate hexahydrate 50 g / L trisodium citrate dihydrate 30 g / L pH. (Adjusted with sodium hydroxide) It was set to 5.5, and the above 35 μm electrolytic copper foil was heated to a bath temperature of 30 in this bath.
° C., a current density of 1A / dm ^2, except that 5 seconds cathodic electrolysis electrolysis time performs the same processing steps as in Example 1 to 18, molding the copper-clad laminate in the same manner, was subjected to the property tests in the same way . The results are shown in Table 2.

(Comparative Example 5) A 35 μm electrolytic copper foil similar to that of the Example was prepared, and as shown in Table 1, cobalt sulfate heptahydrate 5 g / L nickel sulfate hexahydrate 30 g / L citrate trihydrate. Sodium dihydrate 30 g / L pH (adjusted with sulfuric acid) 4.5 and in this bath, the bath temperature of the above 35 μm electrolytic copper foil was 30
° C., a current density of 1.5A / dm ^2, except that the electrolytic time 2 seconds and cathodic electrolysis is carried out the same processing steps as in Example 1 to 18, molding the copper-clad laminate in the same way, the characteristics tested in the same way went. The results are shown in Table 2.

(Comparative Example 6) A 35 μm electrolytic copper foil similar to that of the Example was prepared, and as shown in Table 1, cobalt sulfate heptahydrate 50 g / L nickel sulfate hexahydrate 50 g / L citrate trihydrate. Sodium dihydrate 30 g / L pH (adjusted with sulfuric acid) 5.0 and the bath temperature of the above 35 μm electrolytic copper foil was 30 in this bath.
° C., a current density of 1A / dm ^2, except that 5 seconds cathodic electrolysis electrolysis time performs the same processing steps as in Example 1 to 18, molding the copper-clad laminate in the same manner, was subjected to the property tests in the same way . The results are shown in Table 2.

(Comparative Example 7) A 35 μm electrolytic copper foil similar to that of the Example was prepared, and a cathode density was 4 A for ² seconds at a current density of 2 A / dm ^{2 under} the same bath composition and bath conditions as in Comparative Example 6. 1
The same treatment steps as those of Nos. 18 to 18 were performed, a copper clad laminate was formed by the same method, and each characteristic test was performed by the same method. The results are shown in Table 2.

[0042]

[Table 1]

[0043]

[Table 2]

* 2 Peel strength was measured with a width of 1 mm.
Other conditions are in accordance with JIS-C-6418. * 3 Degradation rate of peel strength after dipping in hydrochloric acid is 6N-H
The deterioration rate after immersion in a Cl aqueous solution at 25 ° C. for 20 minutes was obtained. * 4 Undercutting is 2N in 6N-HCl aqueous solution.
The erosion width after immersion at 5 ° C for 20 minutes was read with a metallurgical microscope. * 5 The deterioration rate of the peeling strength after immersion in a cyanide bath was determined by the deterioration rate after immersion in a 10% -KCN aqueous solution at 70 ° C for 30 minutes. * 6 For undercutting, the erosion width after immersion in a 10% -KCN aqueous solution at 70 ° C for 30 minutes was read with a metallurgical microscope. * 7 Peeling strength after long-term heat treatment is 180 ° C-
The peel strength after heat treatment for 48 hours was measured.

* 8 Alkaline etching Etching method Evaluation ◯: Stain is not recognized at all Δ: Stain is slightly recognized x: Stain of strong intensity

In Table 1, a cobalt and / or nickel layer containing germanium and a chromate film layer formed on the layer and then a silane coupling agent layer formed on the chromate layer were compared with Examples 1 to 18. Composition of plating bath of Examples 1 to 7, pH, electrolysis conditions, deposition amount of cobalt and / or nickel layer containing germanium (mg / m ² ) and content of each element in the layer (wt% = wt%) , And also
Table 2 shows the results of evaluation of various characteristics of the above Examples and Comparative Examples.

Examples 1 to 18 in which a cobalt and / or nickel layer containing germanium and a chromate film layer on the layer and then a silane coupling agent layer on the chromate layer were applied were used. It is also soluble in alkaline etching solutions with metal selectivity,
Furthermore, no occurrence of undercutting was observed after immersion in hydrochloric acid or cyanide bath, the deterioration rate of peeling strength was suppressed to a low level, and the peeling strength after long-term heat treatment was also sufficient, which is excellent. It can be seen that it is a copper foil for printed circuits with versatility.

On the other hand, the individual layers containing no germanium and the binary alloy layers of Comparative Examples 1 to 7 will be described. In the case of a cobalt single layer (Comparative Examples 1 and 2), peeling strength after long-term heat treatment is high. However, undercutting occurs after immersion in a hydrochloric acid or cyanide bath. In the case of a nickel single layer (Comparative Examples 3 and 4), hydrochloric acid resistance and cyan resistance are good, but alkali etching resistance is poor,
This produces a strong stain. In the case of cobalt-nickel layer (Comparative Examples 5, 6, 7), there is little deterioration in peel strength after heat treatment for a long time, and hydrochloric acid resistance is good, but both cyan resistance and alkali etching resistance are high. Cannot be satisfied at the same time. As described above, each has its drawbacks, and there is a problem in using it as a copper foil for a printed wiring board.

[0049]

As described above, the copper foil of the present invention, which is obtained by forming a chromate film layer on the germanium-containing cobalt and / or nickel layer and then forming a silane coupling agent layer on the chromate layer, is a base material. Peeling strength with is sufficient. The above peeling strength is a severe test (chemical treatment, heat treatment)
After that is enough. High reliability of insulation characteristics due to the narrowing of the density of printed circuits. All of the above characteristics are sufficiently satisfied, and the performance can be sufficiently exhibited in a printed wiring board that is significantly narrowed, especially in a high-density printed wiring board.

As described above, the copper foil for a printed wiring board of the present invention, which is soluble in an alkaline etching solution and is suitable for chemical resistance and heat resistance, is suitable not only for general printed wiring boards but also for high density printed wiring boards. It is one.

Claims (2)

[Claims] 1. A copper foil having a cobalt and / or nickel layer containing germanium on at least one surface thereof,
Further, a copper foil for a printed wiring board, characterized in that after forming a chromate film layer on the layer, a silane coupling agent layer is further formed. 2. A copper foil is subjected to cathodic electrolysis in an electrolytic solution containing germanium and cobalt and / or nickel to form a cobalt and / or nickel layer containing germanium, and then the copper foil is removed. It is characterized in that it is immersed in an aqueous solution containing hexavalent chromium or is subjected to cathodic electrolysis, a chromate film layer is provided on the layer, and a silane coupling agent aqueous solution is applied on the chromate film layer to provide a silane coupling agent layer. And a method for producing a copper foil for a printed wiring board.