JP2875186B2 - Processing method of copper foil for printed circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a copper foil for a printed circuit, and more particularly to a method for forming a cobalt plating layer on a surface of a copper foil after a roughening treatment by plating of copper-cobalt-nickel. By doing so, in a processing method for producing a copper foil for a printed circuit having a black surface tone while having alkali etching properties, and also having good heat-resistant peel strength and heat-resistant oxidation properties, the heat-resistant oxidation properties are further enhanced. The present invention relates to an improved method for treating a copper foil for a printed circuit. The copper foil of the present invention is, for example, a fine pattern printed circuit and an FPC (Flexible Printed Circuit) for a magnetic head.
Particularly suitable as.

[0002]

2. Description of the Related Art Copper and copper alloy foil (hereinafter referred to as copper foil)
Has greatly contributed to the development of the electrical and electronic related industries,
In particular, it is indispensable as a printed circuit material. In general, copper foil for printed circuits is laminated and bonded to a base material such as a synthetic resin board and a film under a high temperature and a high pressure with an adhesive or without using an adhesive to produce a copper-clad laminate. After a necessary circuit is printed through a resist coating and exposure process to form a circuit to be formed, an etching process for removing an unnecessary portion is performed. Finally, the required elements are soldered to form various printed circuit boards for electronic devices. The quality requirements for the copper foil for printed circuit boards differ between the surface (roughened surface) bonded to the resin substrate and the non-contact surface (glossy surface), and many methods have been proposed for each.

[0003] For example, requirements for a roughened surface include mainly that there is no oxidative discoloration during storage and that the peeling strength with a substrate is sufficient even after high-temperature heating, wet processing, soldering, chemical processing, or the like. And that there is no so-called lamination stain generated after lamination with the base material and etching.

[0004] Roughening plays a large role in determining the adhesion between the copper foil and the substrate. As the roughening treatment, copper roughening treatment for electrodepositing copper was initially adopted, but various techniques have been subsequently proposed, especially heat-resistant peel strength,
Copper-nickel roughening treatment has come to be established as one typical treatment method for the purpose of improving hydrochloric acid resistance and oxidation resistance. The present applicant has proposed copper-nickel roughening treatment in Japanese Patent Application Laid-Open No. 52-145768 and has achieved results. The copper-nickel-treated surface has a black color, and particularly in rolled foils for flexible substrates, the black color of the copper-nickel treatment has been recognized as a symbol as a commercial product.

However, the copper-nickel roughening treatment is
Although excellent in heat-resistant peeling strength, oxidation resistance and hydrochloric acid resistance, it is difficult to etch with an alkaline etchant that has recently become important as a fine pattern treatment.
When a fine pattern having a circuit width of 150 μm or less is formed, the processing layer is left unetched.

Therefore, as a process for fine patterns,
The applicant of the present application has previously conducted Cu-Co treatment (Japanese Patent Publication No. 63-21 / 1988)
No. 58 and Japanese Patent Application No. 1-112227) and Cu-Co
-Ni processing (Japanese Patent Application No. 1-112226) was developed.
These roughening treatments had good etching properties, alkali etching properties and hydrochloric acid resistance, but it was found again that the heat-resistant peel strength when using an acrylic adhesive was reduced, and oxidation resistance was also low. The color was not enough and the color did not reach black, but it was brown to dark brown.

[0007] With the recent trend toward fine patterning and diversification of printed circuits, the printed circuit boards have heat-resistant peel strength (especially when an acrylic adhesive is used) and hydrochloric acid resistance comparable to those of Cu-Ni treatment. A printed circuit having a circuit width of 150 μm or less can be etched with an alkaline etchant. Oxidation resistance (180 ° C.) as in the case of Cu-Ni treatment.
It has been further required to improve the oxidation resistance in an oven for 30 minutes, and to perform the same blackening treatment as in the case of Cu-Ni treatment. That is, as the circuit becomes thinner, the tendency of the circuit to be easily peeled off by the hydrochloric acid etching solution becomes stronger, and it is necessary to prevent such tendency. When the circuit becomes thin,
The high temperature during the processing such as soldering also makes the circuit easy to peel off, and its prevention is also necessary. Currently fine pattern progresses, for example in CuCl ₂ etching solution 150
It is no longer an essential requirement that a printed circuit having a circuit width of μm pitch or less can be etched, and alkali etching is becoming a necessary requirement as resists and the like are diversified.
The black surface is also important from the standpoint of copper foil fabrication and chip mounting in terms of enhancing alignment accuracy and heat absorption.

In response to such a demand, the present applicant has formed a copper plating layer or a plating layer composed of cobalt and nickel by forming a cobalt plating layer or a plating layer composed of cobalt and nickel on a surface of a copper foil after roughening treatment by plating composed of copper-cobalt-nickel. As well as having many of the general characteristics described above as a printed circuit copper foil, in particular, having the above-mentioned various characteristics comparable to Cu-Ni treatment, and furthermore, the heat-resistant peel strength when using an acrylic adhesive And a copper foil treatment method which is excellent in oxidation resistance and has a black surface color tone has been successfully developed (Japanese Patent Publication No. 6-54831). Preferably, after the formation of the cobalt plating layer or the plating layer composed of cobalt and nickel, a protection treatment represented by a single coating treatment of chromium oxide or a mixed coating treatment of chromium oxide and zinc and / or zinc oxide is preferred. Rust treatment is performed.

[0009]

Thereafter, as the development of electronic equipment has progressed, the miniaturization and high integration of semiconductor devices have further progressed, and the processing performed in the manufacturing process of these printed circuits has become even higher and products The heat generated during the use of the device after the occurrence of the above has caused a decrease in the bonding strength between the copper foil and the resin base material, which has become a problem. The object of the present invention is to
Treatment of copper foil for printed circuit forming a copper plating layer or a plating layer composed of cobalt and nickel after roughening treatment by copper-cobalt-nickel plating on the surface of copper foil established in Japanese Patent Publication No. 6-54831. It is an object of the present invention to further improve the heat-peelability.

[0010]

As a result of the research by the present inventors, a surface of a copper foil is roughened by plating of copper-cobalt-nickel, a cobalt plating layer is formed, and a zinc layer is further formed thereon. It has been clarified that the heat-peelable property can be further improved by making use of the above-mentioned structure while keeping the advantages of the conventional method. Based on this finding, the present invention provides a method for treating a copper foil for a printed circuit, which comprises forming a cobalt plating layer on a surface of the copper foil after roughening treatment by plating comprising copper-cobalt-nickel, and further forming a zinc layer. An object of the present invention is to provide a method for treating a copper foil for a printed circuit, which is characterized by being formed.
Preferably, after the formation of the cobalt plating layer or the plating layer composed of cobalt and nickel, prevention of chromium oxide alone or a mixture of chromium oxide and zinc and / or zinc oxide is performed. Rust treatment is performed.

Specifically, in the method for treating a copper foil for a printed circuit, the amount of adhesion on the surface of the copper foil is 15 to 40 mg / dm ^2.
Copper—100 to 3000 μg / dm ² , preferably 200
0-3000 μg / dm ² cobalt-100-1000
μg / dm ² , preferably 200 to 400 μg / dm ²
After roughening treatment by alloy plating of copper-cobalt-nickel such as nickel, 200-3000 μg /
dm ² , preferably 500 to 3000 μg / dm ² , to form a cobalt plating layer with an adhesion amount of 10 to 80 μg.
/ Dm ² , preferably 20 to 60 μg / dm ² , more preferably 30 to 50 μg / dm ² .

[0012]

The copper foil used in the present invention may be either an electrolytic copper foil or a rolled copper foil. Usually, the surface of the copper foil that adheres to the resin substrate, that is, the roughened surface, has a bumpy shape on the surface of the degreased copper foil for the purpose of improving the peel strength of the copper foil after lamination. A roughening process for performing the wearing is performed. Although the electrolytic copper foil has irregularities at the time of manufacture, the convexities of the electrolytic copper foil are enhanced by roughening treatment to further increase the irregularities. In the present invention, this roughening treatment is performed by copper-cobalt-nickel alloy plating. Normal copper plating or the like may be performed as a pre-treatment before roughening, and normal copper plating or the like may be performed as a finishing treatment after the roughening to prevent the electrodeposits from falling off. The content of the treatment may be somewhat different between the rolled copper foil and the electrolytic copper foil. In the present invention, known treatments related to copper foil roughening, including such a pretreatment and a finishing treatment, are included as necessary, and are generally referred to as a roughening treatment.

According to the present invention, the copper-cobalt-nickel alloy plating as a roughening treatment has an adhesion amount of 15 to 40 mg / dm ² copper-100 to 3000 μm by electrolytic plating.
g / dm ² cobalt—implemented to form a ternary alloy layer such as 100-1000 μg / dm ² nickel. If the amount of Co adhesion is less than 100 μg / dm ² , the heat resistance deteriorates and the etching property deteriorates. If the Co deposition amount exceeds 3000 μg / dm ² , it is not preferable when the influence of magnetism must be taken into consideration, and etching stains may occur, and deterioration in acid resistance and chemical resistance may be considered. If the amount of Ni attached is less than 100 μg / dm ² , the heat resistance becomes poor. On the other hand, the Ni adhesion amount is 1000 μg / d
Beyond m ^2, it becomes large etching residue. Where N
When the amount of i deposition exceeds 500 μg / dm ² , the etching property tends to decrease. In other words, although it is not at the level where etching residue can be formed or cannot be etched,
Fine patterning becomes difficult. Preferred Co deposition amount is 2000~3000μg / dm ² and preferably nickel coating weight is 200~400μg / dm ^2. Here, the etching stain means that when etched with copper chloride, Co remains without dissolving, and when the etching residue is alkali-etched with ammonium chloride, Ni remains without dissolving. It means that.

The general bath and plating conditions for forming such a ternary alloy plating are as follows: (Cu-Co-Ni ternary alloy plating conditions) Cu: 10 to 20 g / liter Co: 1 to 10 g Per liter Ni: 1 to 10 g / liter pH: 1 to 4 Temperature: 40 to 50 ° C. Current density D _k : 20 to 30 A / dm ² hours: 1 to 5 seconds

According to the present invention, after the roughening treatment, 200
A cobalt plating layer having an adhesion amount of ３3000 μg / dm ² is formed. This cobalt plating needs to be performed to such an extent that the adhesive strength between the copper foil and the substrate is not substantially reduced. If the amount of cobalt deposited is less than 200 μg / dm ² , the heat-resistant peel strength decreases, and the oxidation resistance and chemical resistance deteriorate. Another reason is that if the amount of Co is small, the treated surface becomes reddish, which is not preferable. If the amount of deposited cobalt exceeds 3000 μg / dm ² , it is not preferable when the influence of magnetism must be taken into consideration, and etching stains occur, and deterioration in acid resistance and chemical resistance is taken into consideration. The preferred cobalt deposition amount is 500-3000 μg
/ Dm ² .

The conditions of the cobalt plating are as follows: (Cobalt plating) Co: 1 to 30 g / liter pH: 1.5 to 3.5 Temperature: 30 to 80 ° C. D _k : 1.0 to 20.0 A / Dm ² hours: 0.5-4 seconds

According to the present invention, zinc plating is further formed on the cobalt plating with an adhesion amount of 10 to 80 μg / dm ² . When the zinc adhesion amount is less than 10 μg / dm ² , there is no effect of improving the heat deterioration rate (the heat deterioration ratio is 40% or more). On the other hand, when the zinc adhesion amount exceeds 80 μg / dm ² , the hydrochloric acid deterioration rate is extremely poor. (50% or more). Preferably, the zinc deposit is 20 to 60 μg / dm ² , particularly preferably 30 to 50 μg / dm ² . The zinc plating conditions are as follows: Zn: 100 to 300 g / liter pH: 3 to 4 Temperature: 50 to 60 ° C. D _k : 0.1 to 0.5 A / dm ² hours: 1 to 3 seconds

Thereafter, a rust prevention treatment is carried out as required. In the present invention, a preferable rust preventive treatment is a film treatment of chromium oxide alone or a mixture of chromium oxide and zinc / zinc oxide. The coating treatment of a mixture of chromium oxide and zinc / zinc oxide refers to zinc-containing zinc or zinc oxide and chromium oxide by electroplating using a plating bath containing zinc salt or zinc oxide and chromate.
This treatment covers the rust-preventive layer of the chromium-based mixture. As a plating bath, typically, at least one of dichromates such as K ₂ Cr ₂ O ₇ and Na ₂ Cr ₂ O ₇ and CrO ₃ and a water-soluble zinc salt,
For example ZnO, and at least one ZnSO ₄ · 7H ₂ O, etc., a mixed aqueous solution of alkali hydroxide is used. Typical plating bath compositions and examples of electrolysis conditions are as follows: (Chromium rust preventive treatment) K ₂ Cr ₂ O ₇ (Na ₂ Cr ₂ O ₇ or CrO ₃ ): 2 to 10 g / liter NaOH or KOH: 10 to 50 g / liter ZnO or _{ZnSO 4 · 7H 2 O: 0.05~10g} / l pH: 7 to 13 bath temperature: 20 to 80 ° C. current density: 0.05~5A / dm ² Time: 5-30 seconds Anode: Pt-Ti plate, stainless steel plate, etc. Chromium oxide is required to have a coating amount of 15 μg / dm ² or more in terms of chromium, and zinc is required to have a coating amount of 30 μg / dm ² or more.

The copper foil thus obtained has excellent heat-resistant peeling strength, oxidation resistance and hydrochloric acid resistance, and furthermore has CuCl
₍₂₎ A printed circuit having a pitch of 150 μm or less can be etched with an etching solution, and alkali etching is also possible. Examples of the alkaline etching solution include NH ₄ O
H: 6 mol / l; NH ₄ Cl: 5 mol / l; CuCl ₂ : 2 mol / l
(Temperature 50 ° C.) and the like are known.

More importantly, the obtained copper foil is made of Cu
-Has black color as in the case of the Ni treatment. Such black color is important in terms of high alignment accuracy and high heat absorption. Specifically, printed circuit boards, including rigid boards and flexible boards, are equipped with components such as ICs, resistors, and capacitors in an automated process.
At that time, the chip is mounted while reading the circuit with the sensor. At this time, the alignment on the copper foil treated surface may be performed through a film such as Kapton. The same applies to the positioning at the time of forming the through hole. At this time, the closer the processing surface is to black, the better the light absorption, and thus the higher the positioning accuracy. Further, when producing a substrate, the copper foil and the film are often subjected to curing while being heated and adhered. In this case, when heating is performed by using long-wavelength waves such as far-infrared rays and infrared rays, the black surface tone of the treated surface improves the heating efficiency.

Finally, if necessary, a silane treatment for applying a silane coupling agent to at least the roughened surface on the rust preventive layer is performed mainly for the purpose of improving the adhesive strength between the copper foil and the resin substrate. The application method may be any of spraying of a silane coupling agent solution, application with a coater, immersion, and pouring. For example, Japanese Patent Publication No. 60-15654 describes that the adhesive strength between a copper foil and a resin substrate is improved by performing a silane coupling agent treatment after performing a chromate treatment on a rough surface side of the copper foil. . Please refer to this for details. Thereafter, if necessary, an annealing treatment may be performed for the purpose of improving ductility of the copper foil.

[0022]

EXAMPLES Examples and comparative examples will be described below. Copper range of conditions previously described rolled copper foil - cobalt - is subjected to nickel plating roughening treatment, copper 17 mg / dm ^2, the cobalt 2200μg / dm ² and nickel 300 [mu] g /
After dm ^{2 was} adhered, it was washed with water and a cobalt plating was formed thereon. The amount of cobalt deposited was 700 μg / dm ² . Therefore, the total deposition amount of cobalt is 2900 μg / d
m ² . Sample No. As for No. 2, an example in which the amount of deposited cobalt was increased (Sample Nos. 2A and 2B)
Was added. After washing with water, zinc was applied in a range of 10 to 90 μg / dm ² , and finally rustproofing was performed and dried. A sample of Comparative Example to which no zinc was attached was designated as Sample No. 10 was prepared.

The sample was laminated and bonded to a glass cloth base epoxy resin plate, and peeling strength (kg / cm) under normal conditions (room temperature)
Was measured, and the heat resistance deterioration was shown as a deterioration rate (%) of the peel strength after heating at 180 ° C. for 48 hours.
% Immersion in 1% hydrochloric acid for 1 hour
It is shown as a deterioration rate (%) when measured with 10 circuits. In the alkaline etching, the following liquids were used to visually observe the etching state. (Alkali etching solution) NH ₄ OH: 6 mol / l NH ₄ Cl: 5 mol / l CuCl ₂ .2H ₂ O: 2 mol / l Temperature: 50 ° C.

The bath composition and plating conditions used were as follows: [Bath composition and plating conditions] (A) Roughening treatment (Cu-Co-Ni) Cu: 15 g / l Co: 8.5 g / l Ni: 8.6g / l pH: 2.5 temperature: 38 ℃ Dk: 20A / dm 2 Time: 2 seconds copper deposition amount: 17 mg / dm ² of cobalt deposition amount: 2200μg / dm ² of nickel adhesion amount: 300 [mu] g / dm ² (B) Rust prevention treatment (Co) Co: 10 g / l pH 2.5 Temperature: 50 ° C. Dk: 5.6 to 14.4 A / dm ² hours: 0.5 seconds Cobalt adhesion amount: 700 to 2600 μg / dm ² (C) Heat-peeling resistance improving treatment (Zn) Zn: 200 g / l pH: 3.7 Temperature: 56 ° C. Dk: 0.1 to 0.5 A / dm ² hours: 1 second (D) Rust prevention treatment (chromate) K ₂ Cr ₂ O ₇ (Na ₂ Cr ₂ O ₇ or CrO
_3): 5g / l NaOH or KOH: 30g / l ZnO or _{ZnSO 4 · 7H 2 O: 5g} / l pH: 10 Temperature: 40 ℃ Dk: 2A / dm 2 hours 10 seconds anode: Pt-Ti plate

[0025]

[Table 1]

If the zinc deposition amount is less than 10 μg / dm ² , the heat deterioration rate becomes 40% or more, which is not preferable. On the other hand, when the zinc deposition amount exceeds 80 μg / dm ² , the rate of deterioration with hydrochloric acid is 5%.
0% or more, which is not preferable. In consideration of both, preferably, the zinc deposition amount is 20 to 60 μg / dm ² ,
Particularly preferably, it is 30 to 50 μg / dm ² . All alkali etching properties were good.

[0027]

According to the present invention, copper-cobalt-
In a method for treating a copper foil for a printed circuit, which forms a cobalt plating layer after a roughening treatment by plating comprising nickel,
While taking advantage of its beneficial advantages, it succeeded in further improving the heat-resistant peeling property, and in recent years, the processing temperature has been increased due to the rapid development of semiconductor devices, and the density and multilayer structure of printed circuits have been increased. The present invention provides a method for treating a copper foil that can cope with the above.

Continuation of front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) H05K 3/38 H05K 1/09

Claims (6)

(57) [Claims] 1. A method for treating a copper foil for a printed circuit, comprising forming a cobalt plating layer on a surface of the copper foil after a roughening treatment by plating of copper-cobalt-nickel, and further forming a zinc layer. Method for processing copper foil for printed circuits. 2. The method for treating a copper foil for a printed circuit according to claim 1, wherein a rust preventive treatment is performed after the formation of the zinc layer. 3. The copper foil for a printed circuit according to claim 2, wherein the rust preventive treatment is a single film treatment of chromium oxide or a mixed film treatment of chromium oxide and zinc and / or zinc oxide. Processing method. 4. A method for treating a copper foil for a printed circuit, wherein the amount of adhesion on the surface of the copper foil is 15 to 40 mg / dm ² copper-100.
３3000 μg / dm ² cobalt-100-1000 μ
g / dm ² after roughening treatment by copper-cobalt-nickel alloy plating such as nickel
00μg / dm ² of forming a coating weight of cobalt plating layer, further the copper foil for printed circuit according to claim 1 to 3 any one, characterized by forming a zinc layer of 10~80μg / dm ² deposited amount Processing method. 5. The method for treating a copper foil for a printed circuit, wherein the amount of adhesion on the surface of the copper foil is 15 to 40 mg / dm ² copper-200.
0-3000 μg / dm ² cobalt -200-400 μ
g / dm ² after roughening treatment by alloy plating of copper-cobalt-nickel such as nickel,
The copper foil for a printed circuit according to any one of claims 1 to 3, wherein a cobalt plating layer having an adhesion amount of 00 µg / dm ² is formed, and a zinc layer having an adhesion amount of ^{20 to} 60 µg / dm ^{2 is} further formed. Processing method. 6. An adhesion amount of a zinc layer of 30 to 50 μg / dm.
^The method for treating a copper foil for a printed circuit according to claim 5, which is ² .