JPH0650794B2 - Method of treating copper foil for printed circuits - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for treating a copper foil for a printed circuit, and particularly to a printed circuit having good heat resistance and alkali etching properties and having a small magnetic susceptibility. TECHNICAL FIELD The present invention relates to a processing method for producing a copper foil for use. The copper foil of the present invention is used, for example, in a fine pattern printed circuit, an FPC (Frexible Printed C) for a magnetic head.
Particularly suitable as an ircuit).

BACKGROUND OF THE INVENTION Copper foil for printed circuits is generally laminated and adhered to a base material such as a synthetic resin under high temperature and high pressure, and after printing a necessary circuit to form a target circuit, an unnecessary portion is removed and etched. Processing is performed. Finally, the required elements are soldered to form various printed circuit boards for electronic devices.

Quality requirements for a copper foil for a printed wiring board are different between a surface bonded to a resin substrate (so-called roughened surface) and a non-bonded surface (so-called glossy surface), and it is important to satisfy both at the same time.

The requirements for the roughened surface are mainly that there is no oxidative discoloration during storage, that the peel strength with the substrate is sufficient even after high temperature heating, wet treatment, soldering, chemical treatment, etc. The absence of so-called laminated stain after the laminating and etching, etc. can be mentioned.

On the other hand, for glossy surface, good appearance, no oxidative discoloration during storage, good solder wettability, no oxidative discoloration at high temperature heating, good adhesion with resist, etc. Is required.

In order to meet these demands, many treatment methods have been proposed for copper foils for printed wiring boards. The treatment method is different between rolled copper foil and electrolytic copper foil, but after degreasing, the copper foil is subjected to pretreatment including plating and roughening treatment, if necessary, and then alloy plating to form the required copper foil surface. It has been established that one of the useful methods is to perform rust prevention treatment, silane treatment, and if necessary silane treatment.

2. Description of the Related Art The alloy plating treatment described above holds a major key in determining the surface properties of a copper foil. As a typical treatment method for alloy plating, the applicant of the present invention has already proposed that Cu-Ni treatment (JP-A-52-145769) and Cu-Co treatment (JP-B-63).
No. 2158) was proposed and the results were paid.

The former Cu-Ni treatment is excellent in heat-resistant peel strength and hydrochloric acid resistance, but it is difficult to etch even with a copper chloride (CuCl ₂ ) etching solution, and it is not suitable for printed circuits with a circuit width of 150μ pitch or less, and worse. It could not be etched with an alkaline etching solution.

The latter Cu-Co treatment is performed with a copper chloride (CuCl ₂ ) etching solution.
Printed circuits with a width of 50μ pitch or less can be etched,
Alkali etching was also possible, but the heat-resistant peel strength and hydrochloric acid resistance were inferior to those of the case of Ci-Ni treatment.

Problems to be Solved by the Invention With the recent trend toward fine patterning and diversification of printed circuits, it has the same heat-resistant peel strength and hydrochloric acid resistance as in the case of Cu-Ni treatment, and 150μ in CuCl ₂ etching solution. It has become necessary to be able to etch printed circuits with a pitch circuit width or less and also to be able to perform alkaline etching. That is, as the circuit becomes thinner,
The hydrochloric acid etching solution increases the tendency of the circuit to be easily peeled off, and its prevention is necessary. If the circuit becomes thin, the circuit will easily peel off due to the high temperature when solder is applied,
The prevention is also necessary. In the current fine patterning, it is already an essential requirement to be able to etch printed circuits having a circuit width of 150 μ pitch or less with a CuCl ₂ etching solution, and alkali etching is becoming a necessary requirement as resists are diversified.

More importantly, in view of higher performance of the printed circuit and expansion of its application, especially application as an FPC for a magnetic head, the printed circuit is often arranged close to the magnetic medium. There is a new interest in.
Alloys with large magnetic susceptibility as found in conventional Cu-Co alloys cannot be used, and the saturation magnetization, remanent magnetization and coercive force must be regulated to below a predetermined level.

OBJECTS OF THE INVENTION It is an object of the invention, of course, to provide many of the general properties described above for printed circuit copper foils, especially Cu-N.
It has the same heat-resistant peel strength and hydrochloric acid resistance as in the case of i-treatment, it can etch printed circuits with a CuCl ₂ etching solution of less than 150μ pitch circuit width, and it can also perform alkaline etching. It is an object of the present invention to provide a copper foil for a printed circuit that satisfies the requirement of being.

SUMMARY OF THE INVENTION As a result of repeated studies aimed at the above objects, the inventors of the present invention have found that copper-cobalt-containing cobalt and nickel having predetermined cobalt and nickel contents.
It has been found that a ternary alloy containing nickel can satisfy the above purpose. By having a ternary alloy with controlled cobalt and nickel contents,
It was for the first time found here that the advantages of Cu-Ni alloys and Cu-Co alloys can be fully exploited and their disadvantages eliminated. Even if cobalt is included in an amount sufficient to satisfy the above-mentioned etching property requirements, it is possible to reduce the magnetic susceptibility to below an acceptable level, and also by adding cobalt, Cu
It was an unexpected finding that the same heat resistant peel strength and hydrochloric acid resistance as in the case of -Ni alloy can be maintained.

Based on these findings, the present invention provides (1) a method for treating a copper foil for a printed circuit, wherein an electroplating layer made of copper, cobalt and nickel is formed on the surface of the copper foil to be treated. There is provided a method for treating a copper foil for a circuit, and (2) a method for treating a copper foil for a printed circuit according to (1) above, which comprises performing rustproofing treatment after forming the electroplated layer.

Detailed Description of the Invention The copper foil used in the present invention may be either an electrolytic copper foil or a rolled copper foil.

Usually, on the surface of the copper foil that is bonded to the resin substrate, that is, the roughened surface, for the purpose of improving the peeling strength of the copper foil after lamination, the surface of the copper foil after degreasing, for example, is made of copper A roughening treatment for performing electrodeposition is performed. Such copper kinky electrodeposition is easily brought about by so-called burn electrodeposition.
Conventional copper plating may be performed as a pretreatment before roughening and as a finishing treatment after roughening. Roughening treatment by other known methods can also be carried out. The rolled copper foil and the electrolytic copper foil have different processing contents.
The roughening treatment itself may be omitted in some types of rolled copper foil. In the present invention, such processing is generically called preprocessing.

The present invention relates to the treatment of copper foil after pretreatment. After pretreatment, an alloy surface is formed by plating on at least one side of the copper foil, which provides many of the properties required for a printed circuit surface.

According to the invention, this alloy plating is performed by electroplating 20-40 mg / dm ² copper-100-3000 μg / dm ²
Cobalt-100 to 1000 [mu] g / dm < ² > Nickel implemented to form a ternary alloy. 100μ cobalt
If it is less than g / dm ² , heat resistance is deteriorated and etching property is deteriorated. On the other hand, when the cobalt content exceeds 3000 μg / dm ² , the influence of magnetism becomes large, which is not preferable. If the nickel content is less than 100 μg / dm ² , the heat resistance will be poor, and if it exceeds 1000 μg / dm ² , etching residue will be large.

It is difficult to uniquely determine the thickness of the Cu-Co-Ni ternary alloy layer because the copper foil has irregularities on the surface and the true specific gravity when the alloy is formed is unknown.

Therefore, if the true specific gravities of Cu, Co, and Ni alone are used and the unevenness is ignored, and expressed by the calculated average thickness,
The thickness is 0.2 to 0.5 μm, preferably 0.3 to 0.4 μm. 0.2μ
If it is less than m, the peel strength is lowered and the heat resistance and chemical resistance are deteriorated.

Similarly, C in the Cu-Co-Ni ternary alloy layer
The contents of o and Ni are as follows. First, the Co content is preferably 1 to 8% by weight, and if it is less than 1%, the heat resistance becomes poor, and if it exceeds 8%, the influence of magnetism becomes large. On the other hand, the Ni content is preferably 0.5 to 3% by weight, and if less than 0.5%, the heat resistance and the chemical resistance are deteriorated,
On the other hand, if it exceeds 3%, etching cannot be performed with an alkaline etching solution. Further, the total content of Co + Ni is 20
0 to 4000 μg / dm ² is preferable.

The general bath and plating conditions for forming such a ternary alloy are as follows.

Bath composition and plating conditions Cu: 10 to 20 g / Co: 1 to 10 g / Ni: 1 to 10 g / pH: 1 to 4 Temperature: 40 to 50 ° C. Current density D _k : 20 to 30 A / dm ² hours: 1 to 5 Seconds After this, anticorrosion treatment is performed. In the present invention, the preferred rust preventive treatment is a coating treatment of chromium oxide alone or a coating treatment of a mixture of chromium oxide and zinc / zinc oxide. Chromium oxide and zinc / zinc oxide mixture coating treatment means zinc or zinc consisting of zinc oxide and chromium oxide by electroplating using a plating bath containing zinc salt or zinc oxide and chromate. This is a treatment for coating the anticorrosion layer of the chromium-based mixture. The plating bath is typically K ₂ Cr ₂ O ₇ , at least one of dichromates such as Na ₂ Cr ₂ O ₇ and CrO _3, and a water-soluble zinc salt such as ZnO, ZnSO ₄ .7H
A mixed aqueous solution of at least one of ₂ O and alkali hydroxide is used. Typical plating compositions and electrolysis conditions are as follows: K ₂ Cr ₂ O ₇ (Na ₂ Cr ₂ O ₇ or CrO ₃ ) 2-10 g / NaOH or KOH 10-50 g / ZnO or ZnSO ₄ .7H ₂ O 0.05 to 10 g / pH 7 to 13 Bath temperature 20 to 80 ° C. Current density 0.05 to 5 A / dm ² hours 5 to 30 seconds Anode Pt-Ti plate, stainless steel plate, etc. Chromium oxide has a chromium content of 15 μg / dm ² or more and zinc 30 [mu] g / dm ² or more coverage is required. The rough surface side and the glossy surface side may have different thicknesses. Such rust prevention methods are disclosed in Japanese Examined Patent Publications Sho 58-7077 and 61-3390.
8, 62-14040 and the like.

The copper foil thus obtained had a significantly reduced nickel content and contained a considerable amount of cobalt, and thus Cu-N
It has heat-resistant peel strength and hydrochloric acid resistance comparable to the case of i-treatment, and can etch printed circuits with a circuit width of 150 μ pitch or less with CuCl ₂ etching solution, and also enables alkali etching. Examples of the alkaline etching solution include NH ₄ OH: 6 mol /; NH ₄ Cl: 5 mol /;
Liquids such as CuCl ₂ : 2 mol / (temperature of 50 ° C.) are known. Despite containing cobalt, the magnetic susceptibility is below the allowable level. Here, "the magnetic susceptibility is below an allowable level" means that the saturation magnetization M _s is 160 emu / cc or less, the remanent magnetization M _r is 70 emu / cc or less, and the coercive force H _c is 3000 e.
The following are tentative standards at the present time. In the present invention, the saturation magnetization M _s of 50 emu / cc or less, the residual magnetization M _r of 40 emu / cc or less, and the coercive force H _c of 220 e or less can be easily realized.

Further, preferably, for the main purpose of improving the adhesive force between the copper foil and the resin substrate, a silane coupling agent is applied to at least the roughened surface of the anticorrosion layer to perform a silane treatment for forming a thin film. The coating method may be spraying of a silane coupling agent solution, coating with a coater, dipping, pouring, or the like. For example, Japanese Patent Publication No. 60-15654
No. 6 describes that the adhesion between the copper foil and the resin substrate is improved by subjecting the rough surface side of the copper foil to a chromate treatment and then a silane coupling agent treatment, so refer to this for details. I want to be done.

Thereafter, if necessary, an annealing treatment may be performed for the purpose of improving the ductility of the copper foil.

Examples and Comparative Examples After subjecting the rolled copper foil to pretreatment including ordinary roughening treatment,
Several alloy plating treatments were carried out for the purposes of the present invention and comparative purposes.

The conditions for the copper roughening treatment were as follows.

Copper roughening treatment Cu: 10 to 25 g / H ₂ SO ₄ : 20 to 100 g / Temperature: 20 to 40 ° C. D _k : 30 to 70 A / dm ² hours: 1 to 5 seconds Cu-Ni plating (JP-A-52- Substantially according to No. 145769) Cu: 5-10 g / Ni: 10-20 g / pH: 1-4 Temperature: 20-40 ° C. _Dk : 10-30 A / dm ² hours: 2-5 seconds Cu-Co plating (special Substantially according to Kosho 63-2158) Cu: 2.5 g / Co: 20 g / pH: H ₂ SO ₄ 5 g / Temperature: 30 ° C. D _k : 7 A / dm ² hours: 60 seconds Cu-Co-Ni plating (book) Invention) Cu: 5 to 25 g / Co: 3 to 15 g / Ni: 3 to 15 g / pH: 1 to 4 Temperature: 20 to 50 ° C. _Dk : 10 to 30 A / dm ² hours: 2 to 5 seconds After the rust treatment, surface layer component analysis, peel strength characteristics, magnetic properties and etching characteristics were evaluated.

The magnetic characteristics were measured as follows.

Samples 5.5 mm diameter samples were punched with punched punches, 20 plies were stacked and VSM measured. Processing surface area S
Was 0.0475 dm ² .

Evaluation item Saturation magnetization M _s (emu / cc) Remanent magnetization M _r (emu / cc) Coercive force H _c (0e) Measurement Use a VSM made by Toei Industry Co., Ltd. to draw a hysteresis curve and read each characteristic value. It was Maximum applied magnetic field is 10 kOe
And Regarding the residual magnetization and the coercive force, both values were read and the average value was adopted.

Regarding the peel strength, the sample was laminated and adhered to a glass cloth base epoxy resin plate, and the normal (room temperature) peel strength (kg /
cm), and the heat resistance deterioration is shown as the deterioration rate (%) of the peel strength after heating at 180 ° C. for 48 hours, and the hydrochloric acid resistance deterioration is the peel strength after dipping in 18% hydrochloric acid for 1 hour. Deterioration rate (%) when measured by.

The results are summarized in the table below.

The alkali etching is the result of visual observation of the etching state using the above-mentioned alkali etching solution.

Effects of the Invention The present invention provides a method for treating a copper foil capable of accommodating high density and high number of layers for a printed circuit accompanying the recent rapid development of semiconductor devices. The copper foil produced by this method has heat-resistant peel strength and hydrochloric acid resistance, and it has a CuCl ₂ etching solution
Printed circuits with a width of 50μ pitch or less can be etched,
Moreover, alkali etching is also possible. Moreover, with regard to magnetic properties that will become more important in the future, we succeeded in keeping the magnetic susceptibility below the allowable level. The present invention can be used particularly as a fine pattern and as an FPC for a magnetic head.

Claims (2)

[Claims] 1. A method of treating a copper foil for a printed circuit, comprising forming an electroplating layer made of copper, cobalt and nickel on the surface of the copper foil to be treated. 2. The method for treating a copper foil for a printed circuit according to claim 1, further comprising a rustproofing treatment after the electroplating layer is formed.