TWI867785B - Surface treatment of copper foil, copper clad laminates and printed wiring boards - Google Patents

Abstract

The present invention is a surface treated copper foil, which comprises a copper foil and a heteroaromatic compound layer formed on at least one side of the copper foil. The heteroaromatic compound layer contains a heteroaromatic compound and has an Ssk of -2.00 to -0.10, wherein the heteroaromatic compound has a heterocyclic ring containing a nitrogen atom as a heteroatom.

Description

Surface treatment of copper foil, copper clad laminates and printed wiring boards

The present invention relates to a surface treated copper foil, a copper clad laminate and a printed wiring board.

Copper clad laminates are widely used in various applications such as flexible printed wiring boards. The flexible printed wiring boards are manufactured by etching the copper foil of the copper clad laminate to form a conductor pattern (also called a "wiring pattern"), and then mounting electronic components on the conductor pattern by soldering.

In recent years, in electronic devices such as personal computers and mobile terminals, as communication speeds and capacities increase, electrical signals have become increasingly high-frequency, and flexible printed wiring boards are required to cope with this. In particular, the higher the frequency of the electrical signal, the greater the loss (attenuation) of the signal power, making it more likely that data will not be read, so there is a demand to reduce the loss of signal power.

The causes of signal power loss (transmission loss) in electronic circuits can be roughly divided into two categories. One is conductor loss, which is caused by copper foil, and the other is dielectric loss, which is caused by the resin substrate. Conductor loss has the following characteristics, that is, it has a skinning effect in the high-frequency band, and the current flows on the surface of the conductor. Therefore, if the surface of the copper foil is rough, the current will flow along a complex path. Therefore, in order to reduce the conductor loss of high-frequency signals, it is more ideal to reduce the surface roughness of the copper foil. Hereinafter, in this manual, when only "transmission loss" and "conductor loss" are described, they mainly refer to "transmission loss of high-frequency signals" and "conductor loss of high-frequency signals".

Dielectric loss depends on the type of resin substrate. Therefore, in circuit substrates where high-frequency signals flow, it is more ideal to use a resin substrate formed of a low-dielectric material (such as liquid crystal polymer, low-dielectric polyimide). In order to ensure the adhesion between the copper foil and the resin substrate, it is proposed to form a surface treatment layer containing roughened particles on at least one side of the copper foil. It aims to improve the adhesion by utilizing the anchoring effect of the roughened particles immersed in the resin substrate. For example, the following method is proposed in patent document 1: a roughened treatment layer formed by roughened particles is provided on the copper foil, and an anti-rust treatment layer is formed thereon. The anti-rust treatment layer is composed of a nickel-cobalt alloy coating layer, a zinc plating layer, a chromate treatment layer and a silane coupling treatment layer. [Prior art literature] [Patent literature]

[Patent Document 1] Japanese Patent Application Publication No. 2012-112009

[The problem that the invention wants to solve]

The surface treated copper foil described in Patent Document 1 has the problem of increasing the time and cost required for its manufacture because many layers must be formed on the copper foil. In addition, in resin substrates, especially low-dielectric materials, sometimes the anchoring effect of the roughened particles cannot ensure sufficient adhesion.

The embodiment of the present invention is completed to solve the above-mentioned problems. In one embodiment, the purpose is to provide a surface-treated copper foil that can suppress the time and cost required for manufacturing and improve the adhesion with a resin substrate, especially a resin substrate suitable for high-frequency use. In addition, the embodiment of the present invention in another embodiment aims to provide a copper-clad laminate that suppresses the time and cost required for manufacturing and has excellent adhesion between a resin substrate, especially a resin substrate suitable for high-frequency use, and a surface-treated copper foil. Furthermore, the embodiment of the present invention in another embodiment aims to provide a printed wiring board that suppresses the time and cost required for manufacturing and has excellent adhesion between a resin substrate, especially a resin substrate suitable for high-frequency use, and a circuit pattern. [Technical means to solve the problem]

After intensive research to solve the above problems, the inventors surprisingly obtained the following insight: specific heteroaromatic compounds have the function of improving adhesion to the resin substrate. Based on this insight, it was found that by forming a heteroaromatic compound layer containing a specific heteroaromatic compound on at least one side of the copper foil and controlling the Ssk of the surface within a specified range, the above problems can be solved, and the implementation form of the present invention is completed.

That is, in one embodiment of the present invention, there is a surface-treated copper foil having a copper foil and a heteroaromatic compound layer formed on at least one side of the copper foil, wherein the heteroaromatic compound layer contains a heteroaromatic compound and has an Ssk of -2.00 to -0.10, and the heteroaromatic compound has a heterocyclic ring containing a nitrogen atom as a heteroatom. In another embodiment of the present invention, there is a copper-clad laminate having the surface-treated copper foil and a resin substrate connected to the heteroaromatic compound layer of the surface-treated copper foil. Furthermore, another embodiment of the present invention relates to a printed wiring board having a circuit pattern formed by etching the surface-treated copper foil of the copper-clad laminate. [Effect of the invention]

According to an embodiment of the present invention, in one embodiment, a surface-treated copper foil can be provided that can suppress the time and cost required for manufacturing and improve the adhesion with a resin substrate, especially a resin substrate suitable for high-frequency use. Furthermore, according to an embodiment of the present invention, in another embodiment, a copper-clad laminate can be provided that can suppress the time and cost required for manufacturing and has excellent adhesion between a resin substrate, especially a resin substrate suitable for high-frequency use and a surface-treated copper foil. Furthermore, according to an embodiment of the present invention, in another embodiment, a printed wiring board can be provided that can suppress the time and cost required for manufacturing and has excellent adhesion between a resin substrate, especially a resin substrate suitable for high-frequency use and a circuit pattern.

The following specifically describes the preferred embodiments of the present invention, but the present invention should not be limited to these embodiments. As long as they do not deviate from the main purpose of the present invention, various changes and improvements can be made based on the knowledge of the industry. The multiple components disclosed in the following embodiments can form various inventions by appropriate combination. For example, some components can be deleted from all the components disclosed in the following embodiments, and the components of different embodiments can also be appropriately combined.

The surface-treated copper foil of the embodiment of the present invention has a copper foil and a heteroaromatic compound layer formed on at least one side of the copper foil. The heteroaromatic compound layer may be formed on only one side of the copper foil or on both sides of the copper foil. When the heteroaromatic compound layer is formed on both sides of the copper foil, the types of the heteroaromatic compound layers may be the same or different.

Copper foil is not particularly limited and may be either electrolytic copper foil or rolled copper foil. As the material of copper foil, high-purity copper such as refined copper (JIS H3100 alloy number C1100) or oxygen-free copper (JIS H3100 alloy number C1020 or JIS H3510 alloy number C1011) commonly used as circuit patterns of printed wiring boards can be used. In addition, copper alloys such as Sn-doped copper, Ag-doped copper, copper alloys with Cr, Zr or Mg added, and Carsonite copper alloys with Ni and Si added can also be used. Furthermore, in this specification, the term "copper foil" also includes the concept of copper alloy foil.

The thickness of the copper foil is not particularly limited, and may be, for example, 1 to 1000 μm, 1 to 500 μm, 1 to 300 μm, 3 to 100 μm, 5 to 70 μm, 6 to 35 μm, or 9 to 18 μm.

The heteroaromatic compound layer contains heteroaromatic compounds, and the heteroaromatic compounds have a heterocyclic ring containing a nitrogen atom as a heteroatom. The number of ring members of the heterocyclic ring is not particularly limited, and is, for example, 3 to 9, preferably 4 to 6, and more preferably 5. The heteroatoms contained in the heterocyclic ring may be composed of nitrogen atoms only, or may be composed of nitrogen atoms and atoms other than nitrogen atoms (such as oxygen atoms, sulfur atoms, etc.). The number of heteroatoms contained in the heterocyclic ring depends on the number of ring members, and is, for example, 1 to 5, preferably 1 to 4, and more preferably 1 to 3. The heterocyclic ring may be any of a saturated ring and an unsaturated ring. Here, the so-called unsaturated ring includes the concept of a partially unsaturated ring.

Specific examples of heterocyclic rings include acridine (an unsaturated three-membered ring containing one nitrogen atom), diazine (an unsaturated three-membered ring containing two nitrogen atoms), acridine (an unsaturated four-membered ring containing one nitrogen atom), diazine (an unsaturated four-membered ring containing two nitrogen atoms), pyrrole (an unsaturated five-membered ring containing one nitrogen atom), pyrrolidine (a saturated five-membered ring containing one nitrogen atom), imidazole and pyrazole (unsaturated five-membered ring containing two nitrogen atoms), imidazolidinyl and pyrazolidine (saturated five-membered ring containing two nitrogen atoms), Azoles and isothiocyanates Azoles (unsaturated 5-membered rings containing 1 nitrogen atom and 1 oxygen atom), Azolidine and isoxadiazine Azolidine (a saturated 5-membered ring containing 1 nitrogen atom and 1 oxygen atom), thiazole and isothiazole (an unsaturated 5-membered ring containing 1 nitrogen atom and 1 sulfur atom), tetrahydrothiazole and isotetrahydrothiazole (a saturated 5-membered ring containing 1 nitrogen atom and 1 oxygen atom), triazoles such as 1,2,3-triazole or 1,2,4-triazole (an unsaturated 5-membered ring containing 3 nitrogen atoms), tetrazoles (an unsaturated 5-membered ring containing 4 nitrogen atoms), pentazoles (an unsaturated 5-membered ring containing 5 nitrogen atoms), furazolidone and oxadiazole (an unsaturated 5-membered ring containing 2 nitrogen atoms and 1 oxygen atom), thiadiazole (an unsaturated 5-membered ring containing 2 nitrogen atoms and 1 sulfur atom), Azoles (unsaturated 5-membered rings containing 1 nitrogen atom and 2 oxygen atoms), dithiazoles (unsaturated 5-membered rings containing 1 nitrogen atom and 2 sulfur atoms), Tetrazolyl (unsaturated 5-membered ring containing 4 nitrogen atoms and 1 oxygen atom), thiatetrazolyl (unsaturated 5-membered ring containing 4 nitrogen atoms and 1 sulfur atom), pyridine (unsaturated 6-membered ring containing 1 nitrogen atom), piperidine (saturated 6-membered ring containing 1 nitrogen atom), di (unsaturated 6-membered ring containing 2 nitrogen atoms), piperidine (saturated 6-membered ring containing 2 nitrogen atoms), (unsaturated 6-membered ring containing 1 nitrogen atom and 1 oxygen atom), Phytophenone (a saturated six-membered ring containing one nitrogen atom and one oxygen atom), thiophene (unsaturated 6-membered ring containing 1 nitrogen atom and 1 sulfur atom), thio Phytophenone (a saturated six-membered ring containing one nitrogen atom and one sulfur atom), tri (unsaturated 6-membered ring containing 3 nitrogen atoms), tetra (unsaturated 6-membered ring containing 4 nitrogen atoms), five (unsaturated 6-membered ring containing 5 nitrogen atoms), azobenzene (unsaturated 7-membered ring containing 1 nitrogen atom), azepane (saturated 7-membered ring containing 1 nitrogen atom), diazepane (unsaturated 7-membered ring containing 2 nitrogen atoms), diazepane (saturated 7-membered ring containing 2 nitrogen atoms), azocyclooctatetraene (unsaturated 8-membered ring containing 1 nitrogen atom), azocyclooctane (saturated 8-membered ring containing 1 nitrogen atom), azonine (unsaturated 9-membered ring containing 1 nitrogen atom), azonane (saturated 9-membered ring containing 1 nitrogen atom), etc. Among these, from the viewpoint of stably improving the adhesion to the resin substrate, the heterocyclic ring is preferably a 5-membered ring containing 1 to 3 nitrogen atoms, and more preferably an unsaturated 5-membered ring containing 1 to 3 nitrogen atoms (pyrrole, imidazole, pyrazole, Azoles, Isopropylamine azole, thiazole, isothiazole, triazole).

The heteroaromatic compound having a heterocyclic ring may be a condensed ring compound of a benzene ring and a heterocyclic ring, a condensed ring compound of two or more heterocyclic rings, or a heterocyclic monocyclic compound. The condensed ring compound of a benzene ring and a heterocyclic ring is not particularly limited, and examples thereof include indole, indazole, isoindole, benzimidazole, benzotriazole, quinoline, isoquinoline, quinazoline, quinoline, and the like. Phosphine, The condensed ring compound of two or more heterocyclic rings is not particularly limited, and examples thereof include triazolopyridine, purine, pteridine, etc. The monocyclic compound of the heterocyclic ring is not particularly limited, and examples thereof include the compounds exemplified above as heterocyclic rings. Furthermore, the condensed ring compound and the monocyclic compound may also have a substituent. There is no particular limitation on the substituent. Examples of the substituent include alkyl groups such as methyl and ethyl, vinyl groups, and nitro groups.

The heteroaromatic compound layer is a layer containing the above-mentioned heteroaromatic compound. The heteroaromatic compound contained in the heteroaromatic compound layer may be a single type or may be two or more different types. In addition, the heteroaromatic compound layer may contain components other than the heteroaromatic compound within the range that does not impair the effect achieved by the embodiment of the present invention. Such components include solvents or additives mixed in when forming the heteroaromatic compound layer.

Compared with the conventional surface treatment layer including the roughening treatment layer, the hybrid aromatic compound layer has fewer peaks. That is, the hybrid aromatic compound layer has high smoothness. The reason is that the conventional surface treatment layer including the roughening treatment layer improves the adhesion between the surface treatment layer and the resin substrate by the anchoring effect, while the hybrid aromatic compound layer is not intended to obtain the adhesion improvement effect brought about by the anchoring effect. That is, the hybrid aromatic compound layer improves the adhesion between the surface treated copper foil and the resin substrate by the adhesion characteristics of the hybrid aromatic compound, so even if there are fewer peaks and valleys on the surface, the desired adhesion improvement effect can be obtained. Furthermore, the heteroaromatic compound layer has a higher surface smoothness than conventional surface treatment layers including a roughening treatment layer, and thus can reduce transmission loss caused by the skin collection effect.

As one of the indicators indicating the smoothness of the surface, Ssk (skewness) can be used as an indicator indicating the distribution of peaks and valleys on the surface. Ssk is a parameter in the height direction specified by ISO 25178-2:2012, which indicates the symmetry of the peaks and valleys relative to the average surface of the surface. When Ssk is 0, it means that the peaks and valleys are symmetrically distributed. In addition, if Ssk is greater than 0, it means that the peaks on the surface are more than the valleys, and if Ssk is less than 0, it means that the valleys on the surface are more than the peaks. The Ssk of the heteroaromatic compound layer is -2.00 to -0.10. That is, the surface of the heteroaromatic compound layer has more valleys than peaks. Since the surface treatment layer including the roughening treatment layer has many peaks, it can be said that the surface smoothness of the heteroaromatic compound layer is high. Since the heteroaromatic compound layer with Ssk controlled within this range is smooth, the adhesion between the surface-treated copper foil and the resin substrate can be improved due to the adhesion characteristics of the heteroaromatic compound. In addition, the effect of reducing transmission loss can also be achieved. From the perspective of stably obtaining the above effects, the Ssk of the heteroaromatic compound layer is preferably -2.00 to -0.50, more preferably -2.00 to -0.80, and further preferably -1.50 to -0.80. Furthermore, the Ssk of the heteroaromatic compound layer can be measured in accordance with ISO 25178-2:2012.

Compared to the conventional surface treatment layer including the roughening treatment layer, the heteroaromatic compound layer has fewer peaks on the surface because there are no roughening particles. As an indicator of the peak ratio on the surface of such a heteroaromatic compound layer, Vmp (solid volume of the peak) can be used. Vmp is a functional (volume) parameter specified by ISO 25178-2:2012, which represents the solid volume of the peak of the heteroaromatic compound layer. Vmp can be specified as follows: According to ISO 25178-2:2012, the surface roughness is measured and the load curve calculated from the measured data is analyzed. When explaining the load curve, the load area ratio is explained first. The so-called loading area ratio refers to the ratio obtained by dividing the area of the cross section of the three-dimensional object to be measured when it is cut at a certain height by the area of the measurement field of view. Furthermore, in the present invention, it is assumed that the copper foil or the mixed aromatic compound layer of the surface-treated copper foil is used as the measurement object. The loading curve is a curve representing the loading area ratio at each height. The height near the loading area ratio of 0% represents the height of the highest part of the measurement object, and the height near the loading area ratio of 100% represents the height of the lowest part of the measurement object.

Next, an example of a loading curve is shown in Figure 1. The loading curve can be flexibly used to represent the solid volume and space volume of the heteroaromatic compound layer. The so-called solid volume is equivalent to the volume of the solid part of the measured object in the measurement field, and the so-called space volume is equivalent to the volume of the space between the solid parts in the measurement field. In the loading curve, the positions where the loading area ratio is 10% and 80% are used as boundaries to divide it into the valley, the core and the peak. If referring to FIG. 1 and corresponding to the heteroaromatic compound layer of the embodiment of the present invention, Vvv means the spatial volume of the valley of the heteroaromatic compound layer, Vvc means the spatial volume of the core of the heteroaromatic compound layer, Vmp means the solid volume of the peak of the heteroaromatic compound layer, and Vmc means the solid volume of the core of the heteroaromatic compound layer. Furthermore, the peak is the part with a high height in the object to be measured. The valley is the part with a low height in the object to be measured. The core is the part other than the peak and valley in the object to be measured, that is, the part close to the average height.

The peak solid volume Vmp is the solid volume of the peak, i.e., the part of the object to be measured with a high height, which means the solid volume of the part of the heteroaromatic compound layer with a particularly high height. The Vmp of the heteroaromatic compound layer is preferably 0.001 to 0.010 μm ³ /μm ² , and more preferably 0.001 to 0.006 μm ³ /μm ^2. The range of the Vmp of the solid volume of the part with a particularly high height is such a range, which means that the heteroaromatic compound layer is smooth. Moreover, by controlling Vmp within such a range, the adhesion between the surface-treated copper foil and the resin substrate can be improved due to the adhesion characteristics of the heteroaromatic compound. In addition, the effect of reducing transmission loss can also be obtained. Furthermore, the Vmp of the heteroaromatic layer can be determined according to ISO 25178-2:2012.

Compared to the conventional surface treatment layer including the roughening treatment layer, the heteroaromatic compound layer is smoother because there are no roughening particles. The surface valleys of this heteroaromatic compound layer are also shallower. As an indicator of the depth of the valley, Sv (maximum valley depth of the valley) can be used. Sv is a height parameter specified by ISO 25178-2:2012, which indicates the minimum value of the height from the average surface of the heteroaromatic compound layer surface. The Sv of the heteroaromatic compound layer is preferably less than 1.50 μm, more preferably 0.10 to 1.25 μm, and further preferably 0.50 to 1.20 μm. By controlling Sv within this range, the adhesion between the surface-treated copper foil and the resin substrate can be improved due to the adhesion characteristics of the heteroaromatic compound. In addition, the effect of reducing transmission loss can also be achieved. Furthermore, the Sv of the heteroaromatic compound layer can be measured according to ISO 25178-2:2012.

The surface treated copper foil of the embodiment of the present invention is preferably in direct contact with the heteroaromatic compound layer, but a functional layer may be provided between the copper foil and the heteroaromatic compound layer within the scope of not damaging the effect of the embodiment of the present invention. Examples of the functional layer include: a heat resistant treatment layer, a rustproof treatment layer, a chromate treatment layer, etc.

The method for manufacturing the surface-treated copper foil as an embodiment of the present invention is not particularly limited, and can be manufactured, for example, by the following method. First, the copper foil is manufactured by a known method in the technical field. For example, when electrolytic copper foil is used as the copper foil, it can generally be manufactured by electrolytically depositing copper from a copper sulfate bath on a titanium or stainless steel drum. In addition, when rolled copper foil is used as the copper foil, it can generally be manufactured by sequentially subjecting the copper ingot to homogenization annealing, hot rolling, cold rolling, annealing, etc. Alternatively, since copper foil is commercially available, commercially available products can also be used. However, when using commercially available copper foil, rust-proofing agents or oils may adhere to the surface of the copper foil, so the copper foil is degreased and pickled. The reason is that if various surface treatment layers are formed on the surface of the copper foil, it is difficult to form a mixed aromatic compound layer on the surface of the copper foil.

Next, prepare a coating liquid of a mixed aromatic compound. The coating liquid may contain a solvent such as water or an additive. In addition, the concentration of the mixed aromatic compound in the coating liquid can be adjusted according to the type of mixed aromatic compound used, and is not particularly limited, for example, 0.1 to 10% by mass. Next, a mixed aromatic compound layer is formed by applying the coating liquid of the mixed aromatic compound to the surface of the copper foil and drying it. There is no particular limitation on the coating method, for example, various methods such as dipping, spraying, curtain-type flat coating machine coating, roll-type coating machine coating, brush coating, roller brush coating, etc. can be used. In addition, there is no particular limitation on the drying method, and room temperature drying or heating drying can be selected according to the type of solvent used. The coating and drying of the doped aromatic compound coating liquid can be performed once, but can also be performed multiple times to form a doped aromatic compound layer of the desired thickness. Furthermore, the Ssk, Vmp and Sv of the doped aromatic compound layer can be controlled mainly by adjusting the surface roughness of the copper foil forming the doped aromatic compound layer. The roughness of the copper foil can be controlled by adjusting the manufacturing conditions of the copper foil, the degreasing conditions or the pickling conditions before the doped aromatic compound layer is formed, etc.

The surface treated copper foil of the embodiment of the present invention has a heteroaromatic compound layer containing a specific heteroaromatic compound, and the Ssk of the heteroaromatic compound layer is controlled within -2.00 to -0.10, thereby being able to suppress the time and cost required for manufacturing and improving the adhesion with a resin substrate, especially a resin substrate suitable for high-frequency applications.

The copper-clad laminate of the embodiment of the present invention has the surface-treated copper foil and a resin substrate connected to the surface-treated copper foil and the mixed aromatic compound layer. The copper-clad laminate can be manufactured by connecting the resin substrate to the mixed aromatic compound layer of the surface-treated copper foil. The resin substrate is not particularly limited, and those known in the technical field can be used. Examples of resin substrates include: paper-based phenolic resins, paper-based epoxy resins, synthetic fiber cloth-based epoxy resins, glass cloth-paper composite-based epoxy resins, glass cloth-glass non-woven composite-based epoxy resins, glass cloth-based epoxy resins, polyester films, polyimide resins, liquid crystal polymers, fluororesins, etc. Among these, the resin substrate is preferably polyimide resin. In addition, the resin substrate can also be formed from a low dielectric material. Examples of low dielectric materials include liquid crystal polymers, low dielectric polyimides, etc.

There is no particular limitation on the method for bonding the surface-treated copper foil and the resin substrate, and the bonding can be carried out according to a known method in the technical field. For example, the surface-treated copper foil and the resin substrate can be laminated and bonded by heat pressing. The copper-clad laminate manufactured in the above manner can be used for the manufacture of printed wiring boards.

The copper-clad laminate of the embodiment of the present invention uses the surface-treated copper foil, thereby reducing the time and cost required for manufacturing and improving the adhesion between the resin substrate, especially the resin substrate suitable for high-frequency applications, and the surface-treated copper foil.

The printed wiring board of the embodiment of the present invention has a circuit pattern formed by etching the surface-treated copper foil of the copper-clad laminate. The printed wiring board can be manufactured by etching the surface-treated copper foil of the copper-clad laminate to form a circuit pattern. There is no particular limitation on the method for forming the circuit pattern, and known methods such as a subtractive method and a semi-additive method can be used. Among them, the method for forming the circuit pattern is preferably a subtractive method.

When a printed wiring board is manufactured by a subtractive method, it is preferably carried out as follows. First, a resist is applied to the surface of the surface-treated copper foil of the copper-clad laminate, and exposure and development are performed to form a prescribed resist pattern. Then, the surface-treated copper foil where the resist pattern is not formed (unnecessary portion) is removed by etching to form a circuit pattern. Finally, the resist pattern on the surface-treated copper foil is removed. Furthermore, the various conditions in the subtractive method are not particularly limited and can be performed according to the conditions known in the technical field.

Since the printed wiring board of the embodiment of the present invention uses the above-mentioned copper-clad multilayer board, the time and cost required for manufacturing can be reduced, and the adhesion between the resin substrate, especially the resin substrate suitable for high-frequency use, and the circuit pattern can be improved. [Example]

Hereinafter, the embodiments of the present invention will be described in more detail, but the present invention is not limited to these embodiments.

(Example 1) A commercially available rolled copper foil (HA-V2 manufactured by JX Metal Co., Ltd.; thickness 12 μm) is prepared as a copper foil, and both sides of the copper foil are degreased and pickled. Degreasing is carried out in the following manner: the surface of the rolled copper foil is electrolyzed in a 20 g/L aqueous solution of GN cleaning liquid 87 (JX Metal Trading Co., Ltd.) at a current density of 11.3 A/dm ² and a time of 8.6 seconds. In addition, pickling is carried out by immersing in a 20 g/L aqueous solution of sulfuric acid for 30 seconds. Next, using benzotriazole represented by the following formula (1) as a heteroaromatic compound, an aqueous solution of benzotriazole (coating solution) is prepared. The concentration of benzotriazole in the aqueous solution is set to 1 mass %.

Next, the copper foil was immersed in an aqueous solution of benzotriazole for 30 seconds, then washed with water and dried in a dryer. In this way, a surface-treated copper foil having a benzotriazole layer (heteroaromatic compound layer) formed on the surface of the copper foil was obtained.

(Example 2) Except for using indazole represented by the following formula (2) as the heteroaromatic compound, a surface-treated copper foil having an indazole layer (heteroaromatic compound layer) formed on the surface of the copper foil is obtained by the same conditions as in Example 1.

(Example 3) Except for using the benzimidazole represented by the following formula (3) as the heteroaromatic compound, a surface-treated copper foil having a benzimidazole layer (heteroaromatic compound layer) formed on the surface of the copper foil is obtained by the same conditions as in Example 1.

(Example 4) Except for using indole represented by the following formula (4) as the heteroaromatic compound, a surface-treated copper foil having an indole layer (heteroaromatic compound layer) formed on the surface of the copper foil is obtained by the same conditions as in Example 1.

(Example 5) Except for using the triazolopyridine represented by the following formula (5) as the heteroaromatic compound, a surface-treated copper foil having a triazolopyridine layer (heteroaromatic compound layer) formed on the surface of the copper foil is obtained by the same conditions as in Example 1.

(Example 6) Except for using 1-methylbenzotriazole represented by the following formula (6) as the heteroaromatic compound, a surface-treated copper foil having a 1-methylbenzotriazole layer (heteroaromatic compound layer) formed on the surface of the copper foil is obtained by the same conditions as in Example 1.

(Example 7) Except for using 5-methylbenzotriazole represented by the following formula (7) as the heteroaromatic compound, a surface-treated copper foil having a 5-methylbenzotriazole layer (heteroaromatic compound layer) formed on the surface of the copper foil is obtained by the same conditions as in Example 1.

(Example 8) Except for using 1,2,3-triazole represented by the following formula (8) as the heteroaromatic compound, a surface-treated copper foil having a 1,2,3-triazole layer (heteroaromatic compound layer) formed on the surface of the copper foil is obtained by the same conditions as in Example 1.

(Comparative Example 1) A commercially available rolled copper foil (HA-V2 manufactured by JX Metal Co., Ltd.; thickness 12 μm) that was degreased and pickled on both sides (copper foil without a doped aromatic compound layer) was used as a comparative sample. Furthermore, the degreasing and pickling were performed under the same conditions as in Example 1.

(Comparative Example 2) Under the same conditions as in Example 1, both sides of a commercially available rolled copper foil (HA-V2 manufactured by JX Metal Co., Ltd.; thickness 12 μm) were degreased and pickled. Then, a surface-treated copper foil was obtained by sequentially forming a roughening treatment layer, an anti-rust layer, and a silane coupling treatment layer on the surface of the copper foil. The conditions for forming each layer are as follows.

<Roughening layer> The roughening layer is formed by electroplating. Electroplating is performed in three stages. The composition of the plating solution and the current density are basically the values obtained by rounding off the first decimal point. (Conditions for the first stage) Plating solution composition: 11 g/L Cu, 50 g/L sulfuric acid Plating solution temperature: 27°C Electroplating conditions: current density 40 A/dm ² , time 1.4 seconds (Conditions for the second stage) Plating solution composition: 20 g/L Cu, 100 g/L sulfuric acid Plating solution temperature: 50°C Electroplating conditions: current density 5 A/dm ² , time 2.0 seconds (Conditions for the third stage) Plating solution composition: 16 g/L Cu, 8 g/L Co, 10 g/L Ni Plating solution pH: 2.4 Plating solution temperature: 36°C Electroplating conditions: current density 32 A/dm ² , time 0.2 seconds

<Anti-rust layer> Anti-rust layer is formed by electroplating. Electroplating is carried out in 3 stages. (Conditions for the first stage) Plating solution composition: 3 g/L Co, 13 g/L Ni Plating solution pH: 2.0 Plating solution temperature: 50°C Electroplating conditions: current density 2 A/dm ² , time 0.8 seconds (Conditions for the second stage) Plating solution composition: 5 g/L Zn, 24 g/L Ni Plating solution pH: 3.6 Plating solution temperature: 40°C Electroplating conditions: current density 4 A/dm ² , time 0.4 seconds (Conditions for the third stage) Plating solution composition: 3 g/L K ₂ Cr ₂ O ₇ , 0.3 g/L Zn Plating solution pH: 3.7 Plating solution temperature: 55°C Electroplating conditions: current density 3 A/dm ² , time 0.8 seconds

<Silane coupling treatment layer> A 4.0 volume % aqueous solution (pH: 10.4) of N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (KBM603 manufactured by Shin-Etsu Chemical Co., Ltd.) was applied and dried to form a silane coupling treatment layer.

(Comparative Example 3) Under the same conditions as in Example 1, both sides of a commercially available rolled copper foil (HA-V2 manufactured by JX Metal Co., Ltd.; thickness 12 μm) were degreased and pickled. Then, a surface-treated copper foil was obtained by sequentially forming a roughening treatment layer, a heat-resistant layer, a chromate treatment layer, and a silane coupling treatment layer on the surface of the copper foil. The conditions for forming each layer are as follows.

<Roughening layer> The roughening layer is formed by electroplating. Electroplating is performed in two stages. (Conditions for the first stage) Plating solution composition: 11 g/L Cu, 50 g/L sulfuric acid Plating solution temperature: 25°C Plating conditions: current density 42.7 A/dm ² , time 1.4 seconds (Conditions for the second stage) Plating solution composition: 20 g/L Cu, 100 g/L sulfuric acid Plating solution temperature: 50°C Plating conditions: current density 3.8 A/dm ² , time 2.8 seconds

<Heat-resistant layer> The heat-resistant layer is formed by electroplating. Plating solution composition: 23.5 g/L Ni, 4.5 g/L Zn Plating solution pH: 3.6 Plating solution temperature: 40°C Electroplating conditions: current density 1.1 A/dm ² , time 0.7 seconds

<Chromate treatment layer> The chromate treatment layer is formed by electroplating. Plating solution composition: 3.0 g/L K ₂ Cr ₂ O ₇ , 0.33 g/L Zn Plating solution pH: 3.6 Plating solution temperature: 50°C Electroplating conditions: current density 2.1 A/dm ² , time 1.4 seconds

<Silane coupling treatment layer> A 1.2 volume % aqueous solution (pH: 10) of N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (KBM603 manufactured by Shin-Etsu Chemical Co., Ltd.) was applied and dried to form a silane coupling treatment layer.

The surface treated copper foil or copper foil obtained in the above-mentioned embodiment and comparative example was evaluated for the following characteristics. ＜Ssk, Vmp and Sv＞ The image was photographed using a laser microscope (LEXT OLS4000) manufactured by Olympus Corporation. The image was analyzed using the analysis software of the laser microscope (LEXT OLS4100) manufactured by Olympus Corporation. The measurement of Ssk, Vmp and Sv was performed in accordance with ISO 25178-2:2012. In addition, for these measurement results, the average value of the values measured at any three locations was taken as the measurement result. In addition, the temperature during the measurement was set to 23 to 25°C. In addition, the main setting conditions in the laser microscope and the analysis software are as follows. Objective lens: MPLAPON50XLEXT (magnification: 50x, numerical aperture: 0.95, immersion type: air, mechanical barrel length: ∞, cover glass thickness: 0, field of view: FN18) Optical zoom ratio: 1x Scanning mode: XYZ high precision (height resolution: 60 nm, number of pixels of input data: 1024×1024) Input image size [number of pixels]: horizontal 257 μm × vertical 258 μm [1024×1024] (Since it is measured in the horizontal direction, the evaluation length is equivalent to 257 μm) DIC: Off Multi-layer: Off Laser intensity: 100 Offset: 0 Confocal level: 0 Beam diameter aperture: Off Image averaging: 1 time Noise reduction: On Brightness unevenness correction: On Optical noise filter: On Cutoff: λc=200 μm, no λs and λf Filter: Gaussian filter Noise removal: Pre-measurement processing Surface (tilt) correction: Implemented Brightness: Adjusted to a range of 30 to 50 Brightness is a value that should be appropriately set according to the color tone of the object being measured. The above settings are appropriate values when measuring the surface of surface-treated copper foil with L* of -69 to -10, a* of 2 to 32, and b* of 2 to 21.

<Measurement of the color tone of the measurement object> MiniScan (registered trademark) EZ Model 4000L manufactured by HunterLab was used as a measuring instrument to measure L*, a* and b* of the CIE L*a*b* colorimetric system in accordance with JIS Z8730:2009. Specifically, the surface-treated copper foil or copper foil obtained in the above-mentioned embodiment and comparative example was pressed against the photosensitive part of the measuring instrument, and the measurement was performed without light entering from the outside. In addition, the measurement of L*, a* and b* was performed based on the geometric condition C of JIS Z8722:2009. In addition, the main conditions of the measuring instrument are as follows. Optical system: d/8°, integrating sphere size: 63.5 mm, observation light source: D65 Measurement method: reflection Illumination diameter: 25.4 mm Measurement diameter: 20.0 mm Measurement wavelength, interval: 400-700 nm, 10 nm Light source: pulsed xenon lamp, 1 light/measurement Traceability standard: Calibrated according to the National Institute of Standards and Technology (NIST) based on CIE 44 and ASTM E259 Standard observer: 10° In addition, the white tile used as the measurement standard is the one with the following object color. When measured at D65/10°, the values in the CIE XYZ colorimetric system are X: 81.90, Y: 87.02, Z: 93.76

<Peeling strength> After bonding the surface treated copper foil to a resin substrate formed of a low dielectric material, a circuit with a width of 3 mm was formed along the MD direction (the length direction of the rolled copper foil). The circuit formation was carried out according to the usual method. Then, the strength (MD90° peeling strength) when the circuit (surface treated copper foil) was peeled off at a speed of 50 mm/min in the 90° direction relative to the surface of the resin substrate, that is, directly above the lead relative to the surface of the LCP substrate, was measured in accordance with JIS C6471:1995. The measurement was performed 3 times, and the average value was taken as the peeling strength result. If the peel strength is above 0.50 kgf/cm, it can be said that the adhesion between the circuit (surface-treated copper foil) and the LCP substrate is good.

The results of the above-mentioned characteristic evaluation are shown in Table 1.

[Table 1] Ssk Vmp [μm ³ /μm ² ] Sv [μm] Peel strength [kgf/cm] Embodiment 1 -1.20 0.004 0.92 0.56 Embodiment 2 -1.34 0.004 1.16 0.60 Embodiment 3 -0.94 0.007 1.11 0.58 Embodiment 4 -1.00 0.005 1.04 0.63 Embodiment 5 -1.09 0.005 0.96 0.59 Embodiment 6 -1.10 0.005 1.06 0.64 Embodiment 7 -1.26 0.004 1.03 0.52 Embodiment 8 -1.13 0.005 1.10 0.56 Comparison Example 1 -1.18 0.004 0.95 0.18 Comparison Example 2 0.57 0.036 1.74 0.60 Comparison Example 3 -0.32 0.013 1.20 0.20

As shown in Table 1, the surface-treated copper foils of Examples 1 to 8, which formed a heteroaromatic compound layer and had an Ssk in the range of -2.00 to -0.10, had the same peel strength as the surface-treated copper foil of Comparative Example 2, which formed a surface-treated layer such as a roughening treatment layer, and the adhesion between the LCP substrate and the surface-treated copper foil was good. In contrast, the copper foil of Comparative Example 1, which did not form a heteroaromatic compound layer, had a low peel strength. In addition, it is believed that the peel strength of Comparative Example 3 was lower because the roughening was smaller than that of Comparative Example 2. The above results are surprising. As mentioned above, the adhesion between copper foil and resin substrates such as LCP substrates is generally improved by forming a surface treatment layer containing roughened particles. In the embodiment of the present invention, the adhesion with resin substrates such as LCP substrates is fully ensured by the presence of a mixed aromatic compound layer with a smooth surface.

From the above results, it can be seen that according to the implementation form of the present invention, a surface-treated copper foil can be provided that can suppress the time and cost required for manufacturing and improve the adhesion with a resin substrate, especially a resin substrate suitable for high-frequency use. In addition, according to the implementation form of the present invention, a copper-clad laminate can be provided that suppresses the time and cost required for manufacturing and has excellent adhesion between a resin substrate, especially a resin substrate suitable for high-frequency use and a surface-treated copper foil. Furthermore, according to the implementation form of the present invention, a printed wiring board can be provided that suppresses the time and cost required for manufacturing and has excellent adhesion between a resin substrate, especially a resin substrate suitable for high-frequency use and a circuit pattern.

The present invention can also be implemented in the following forms. <1> A surface-treated copper foil having a copper foil and a heteroaromatic compound layer formed on at least one side of the copper foil, wherein the heteroaromatic compound layer contains a heteroaromatic compound and has an Ssk of -2.00 to -0.10, and the heteroaromatic compound has a heterocyclic ring containing a nitrogen atom as a heteroatom. <2> The surface-treated copper foil as described in <1>, wherein the heterocyclic ring is a 5-membered ring containing 1 to 3 nitrogen atoms. <3> The surface-treated copper foil as described in <1> or <2>, wherein the heteroaromatic compound is a condensed ring compound of a benzene ring and the heterocyclic ring, a condensed ring compound of two or more heterocyclic rings, or a monocyclic compound of the heterocyclic ring. <4> The surface-treated copper foil as described in any one of <1> to <3>, wherein the heteroaromatic compound is one or more selected from the group consisting of benzotriazole, indazole, benzimidazole, indole, triazolopyridine, 1-methylbenzotriazole, 5-methylbenzotriazole, and 1,2,3-triazole. <5> The surface-treated copper foil as described in any one of <1> to <4>, wherein the Ssk is -2.00 to -0.50. <6> The surface-treated copper foil as described in <5>, wherein the Ssk is -2.00 to -0.80. <7> The surface-treated copper foil as described in <5>, wherein the Ssk is -1.50 to -0.80. <8> The surface-treated copper foil as described in any one of <1> to <7>, wherein the Vmp of the heteroaromatic compound layer is 0.001 to 0.010 μm ³ /μm ² . <9> The surface-treated copper foil as described in <8>, wherein the Vmp is 0.001 to 0.006 μm ³ /μm ² . <10> A copper-clad laminate having a surface-treated copper foil as described in any one of <1> to <9>, and a resin substrate having the mixed aromatic compound layer attached to the surface-treated copper foil. <11> A printed wiring board having a circuit pattern formed by etching the surface-treated copper foil of the copper-clad laminate as described in <10>.

without

[Figure 1] is an example of the loading curve of the heteroaromatic compound layer.

Claims (10)

A surface-treated copper foil having a copper foil and a heteroaromatic compound layer formed on at least one side of the copper foil, wherein the heteroaromatic compound layer contains a heteroaromatic compound and has an Ssk of -2.00 to -0.10, wherein the heteroaromatic compound has a heterocyclic ring containing a nitrogen atom as a heteroatom, and the heteroaromatic compound is selected from at least one of the group consisting of benzotriazole, indazole, benzimidazole, indole, triazolopyridine, 1-methylbenzotriazole, 5-methylbenzotriazole and 1,2,3-triazole. The surface treated copper foil of claim 1, wherein the heterocyclic ring is a 5-membered ring containing 1 to 3 nitrogen atoms. The surface-treated copper foil of claim 1, wherein the heteroaromatic compound is a condensed ring compound of a benzene ring and the heterocyclic ring, a condensed ring compound of two or more heterocyclic rings, or a monocyclic compound of the heterocyclic ring. For example, the surface treated copper foil of claim 3, wherein the Ssk is -2.00~-0.50. For example, the surface treated copper foil of claim 3, wherein the Ssk is -2.00~-0.80. For example, the surface treated copper foil of claim 3, wherein the Ssk is -1.50~-0.80. The surface treated copper foil of any one of claims 1 to 6, wherein the Vmp of the heteroaromatic compound layer is 0.001-0.010 μm ³ /μm ² . The surface treated copper foil of claim 7, wherein the Vmp is 0.001-0.006 μm ³ /μm ² . A copper-clad laminate having a surface-treated copper foil as described in any one of claims 1 to 8, and a resin substrate having the heteroaromatic compound layer attached to the surface-treated copper foil. A printed wiring board having a circuit pattern formed by etching the surface treated copper foil of the copper clad laminate as claimed in claim 9.