Surface-treated copper foil, copper-clad laminates and printed wiring boards

Abstract

A surface-treated copper foil comprising a copper foil and a surface-treating layer formed on at least one surface of the copper foil. The surface-treating layer has an Sku of 2.50-4.50 and an Str of 0.20-0.40.

Description

[Technical Field]

[0001] The present disclosure relates to a surface-treated copper foil, a copper-clad laminate, and a printed wiring board. [Background technology]

[0002] Copper-clad laminates are widely used in various applications, such as flexible printed wiring boards. Flexible printed wiring boards are manufactured by etching the copper foil of a copper-clad laminate to form a conductor pattern (also called a "wiring pattern"), and then mounting electronic components on the conductor pattern by connecting them with solder.

[0003] In recent years, electronic devices such as personal computers and mobile terminals have been using higher frequencies for electrical signals in response to faster and larger communications volumes, creating a demand for flexible printed wiring boards that can accommodate this. In particular, the higher the frequency of the electrical signal, the greater the loss (attenuation) of signal power, making it easier for data to become unreadable, so there is a demand for reducing signal power loss.

[0004] The causes of signal power loss (transmission loss) in electronic circuits can be broadly divided into two categories: 1) conductor loss, i.e., loss due to copper foil, and 2) dielectric loss, i.e., loss due to the resin substrate. Conductor loss is characterized by the skin effect in the high frequency range, where current flows along the surface of the conductor. Therefore, if the copper foil surface is rough, the current will flow along a complex path. Therefore, to reduce the conductor loss of high-frequency signals, it is desirable to reduce the surface roughness of the copper foil. Hereinafter, when the terms "transmission loss" and "conductor loss" are simply used, they mainly mean "transmission loss of high-frequency signals" and "conductor loss of high-frequency signals."

[0005] On the other hand, since dielectric loss depends on the type of resin substrate, it is desirable to use a resin substrate made of a low-dielectric material (e.g., liquid crystal polymer, low-dielectric polyimide) for circuit boards through which high-frequency signals flow. Also, since dielectric loss is also affected by the adhesive used to bond the copper foil and resin substrate, it is desirable to bond the copper foil and resin substrate without using an adhesive. Therefore, in order to bond the copper foil and the resin substrate without using an adhesive, it has been proposed to form a surface treatment layer on at least one side of the copper foil.For example, Patent Document 1 proposes a method in which a roughening treatment layer made of roughening particles is provided on the copper foil, and a silane coupling treatment layer is formed on the outermost surface layer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-112009 Summary of the Invention [Problem to be solved by the invention]

[0007] The surface of copper foil on which a surface treatment layer is formed generally has minute irregularities. For example, in the case of rolled copper foil, oil pits formed by rolling oil during rolling form minute irregularities on the surface. In addition, in the case of electrolytic copper foil, grinding streaks formed by the rotating drum during polishing cause minute irregularities on the rotating drum side surface of the electrolytic copper foil that is deposited and formed on the rotating drum. If the copper foil has minute irregularities, for example, when forming a roughened layer, current concentrates in the convex parts, causing the roughening particles to overgrow, while insufficient current is supplied to the concave parts, making it difficult for the roughening particles to grow. As a result, coarse roughening particles are formed in the convex parts of the copper foil, while the roughening particles are too small in the concave parts of the copper foil, resulting in a state in which the roughening particles are not uniformly formed on the copper foil surface. In the case of a surface-treated copper foil containing a large number of coarse roughening particles, when a force is applied to peel the surface-treated copper foil after bonding to a resin substrate, stress concentrates on the coarse roughening particles, making the foil more likely to break, which can result in a decrease in adhesion to the resin substrate. Furthermore, in the case of a surface-treated copper foil with insufficient roughening particle size, the anchoring effect of the roughening particles is reduced, and sufficient adhesion between the copper foil and the resin substrate can be insufficient. In particular, resin substrates made from low-dielectric materials such as liquid crystal polymers and low-dielectric polyimides are more difficult to bond to copper foil than conventional resin substrates, so there is a need to develop a method for improving the adhesion between copper foil and resin substrates. Furthermore, although the silane coupling treatment layer has the effect of improving the adhesion between the copper foil and the resin substrate, depending on the type of the silane coupling treatment layer, the effect of improving the adhesion may not be sufficient.

[0008] The embodiments of the present invention have been made to solve the above-mentioned problems, and one object of the present invention is to provide a surface-treated copper foil that can improve adhesion to a resin substrate, particularly a resin substrate suitable for high-frequency applications. Another object of the present invention is to provide a copper-clad laminate having excellent adhesion between a resin substrate, particularly a resin substrate suitable for high-frequency applications, and a surface-treated copper foil. Furthermore, in another aspect, an object of the present invention is to provide a printed wiring board having excellent adhesion between a resin substrate, particularly a resin substrate suitable for high frequency applications, and a circuit pattern. [Means for solving the problem]

[0009] The present inventors have conducted extensive research into surface-treated copper foils to solve the above problems, and have discovered that adding a trace amount of a tungsten compound to a plating solution used to form a roughened layer can suppress overgrowth of roughening particles formed on the convex portions of the copper foil and facilitate the formation of roughening particles in the concave portions of the copper foil. The present inventors then analyzed the surface shape of the surface-treated copper foils obtained in this manner and found that the Sku and Str of the surface treatment layer are closely related to this surface shape, leading to the completion of an embodiment of the present invention.

[0010] That is, in one aspect, an embodiment of the present invention relates to a surface-treated copper foil having a copper foil and a surface treatment layer formed on at least one surface of the copper foil, wherein the surface treatment layer has an Sku of 2.50 to 4.50 and an Str of 0.20 to 0.40. In another aspect, an embodiment of the present invention relates to a copper-clad laminate comprising the surface-treated copper foil and a resin substrate adhered to the surface treatment layer of the surface-treated copper foil. Furthermore, in another aspect, an 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. [Effects of the Invention]

[0011] According to one aspect of the present invention, a surface-treated copper foil capable of improving adhesion to a resin substrate, particularly a resin substrate suitable for high-frequency applications, can be provided. In another aspect, an embodiment of the present invention can provide a copper-clad laminate having excellent adhesion between a resin substrate, particularly a resin substrate suitable for high-frequency applications, and a surface-treated copper foil. Furthermore, according to another aspect of the present invention, a printed wiring board can be provided that has excellent adhesion between a resin substrate, particularly a resin substrate suitable for high frequency applications, and a circuit pattern. [Brief explanation of the drawings]

[0012] [Figure 1]FIG. 1 is a schematic enlarged cross-sectional view of a surface-treated copper foil having a roughened layer on one side of the copper foil. DETAILED DESCRIPTION OF THE INVENTION

[0013] Preferred embodiments of the present invention will be described in detail below, but the present invention should not be construed as being limited thereto, and various modifications and improvements can be made based on the knowledge of those skilled in the art without departing from the gist of the present invention. The multiple components disclosed in the following embodiments can be appropriately combined to form various inventions. For example, some components may be deleted from all the components shown in the following embodiments, or components from different embodiments may be appropriately combined.

[0014] The surface-treated copper foil according to the embodiment of the present invention comprises a copper foil and a surface treatment layer formed on at least one surface of the copper foil. The surface treatment layer may be formed on only one side of the copper foil, or on both sides of the copper foil. When the surface treatment layer is formed on both sides of the copper foil, the types of the surface treatment layers may be the same or different.

[0015] The surface treatment layer has an Sku (kurtosis) of 2.50 to 4.50. Sku is defined in ISO 25178-2:2012. Sku is a parameter that expresses the degree of peaking (kurtosis) of a height histogram created based on the average height. For example, Sku = 3.00 means that the height distribution is normal. Furthermore, when Sku > 3.00, the larger the value, the more concentrated the height distribution. Conversely, when Sku < 3.00, the smaller the value, the more dispersed the height distribution.

[0016] The surface-treated copper foil according to the embodiment of the present invention has a surface irregularity, which contributes to improving the adhesion between the copper foil and the resin substrate. The Sku of the surface-treated layer is an index for evaluating the height distribution of the irregularities. An Sku of the surface treatment layer of 2.50 to 4.50 means that the height distribution is normal or close to normal. On the other hand, an Sku of the surface treatment layer of less than 2.50 means that the height distribution of the surface treatment layer (height from the copper foil surface) is not biased, resulting from a mixture of low and high parts. An Sku of the surface treatment layer of more than 4.50 means that the height distribution is biased, that is, the surface of the surface treatment layer is dominated by parts of a certain height. A surface treatment layer having a height distribution that is normal or close to normal means, for example, that when a roughening treatment layer is formed on the surface of a copper foil, there are few overgrown roughening particles, i.e., large roughening particles, on the convex portions of the copper foil, and there are few areas in the concave portions of the copper foil where no roughening particles are formed. Therefore, a surface treatment layer having an Sku of 2.50 to 4.50 means that the overgrowth of roughening particles formed on the convex portions of the copper foil is suppressed, and that roughening particles are also formed in the concave portions of the copper foil.

[0017] Neither surface-treated copper foils with many coarse roughening particles nor surface-treated copper foils with areas where no roughening particles are formed are preferable from the viewpoint of adhesion to resin substrates. For example, when a surface-treated copper foil with many coarse roughening particles is bonded to a resin substrate and a peel force is applied to the surface-treated copper foil, stress is concentrated on the coarse roughening particles, making the foil more likely to break, which is thought to result in a decrease in adhesion to the resin substrate. Furthermore, when a surface-treated copper foil with areas where no roughening particles are formed is bonded to a resin substrate, the anchoring effect of the roughening particles cannot be sufficiently ensured, and the adhesion between the surface-treated copper foil and the resin substrate is thought to be decreased. The present inventors measured and analyzed the peel strength of the surface-treated copper foils in the Examples and Comparative Examples described below, and found that the Sku of the surface treatment layer is involved in adhesion to the resin substrate. From the viewpoint of obtaining stable adhesive strength to a resin substrate, the Sku of the surface treatment layer is preferably 2.80 to 4.00, and more preferably 2.90 to 3.75. The Sku of the surface treatment layer is measured in accordance with ISO 25178-2:2012.

[0018] The surface treatment layer has an Str (texture aspect ratio) of 0.20 to 0.40. Str is a spatial parameter defined in ISO 25178-2:2012 that indicates the strength of anisotropy or isotropy of the surface. Str is in the range of 0 to 1, and the closer to 0, the stronger the anisotropy (for example, larger grain). Conversely, the closer to 1, Str is, the stronger the isotropy. When the Str of the surface treatment layer is 0.20 to 0.40, the surface of the surface treatment layer has moderate anisotropy. This state means that the surface treatment layer is uniformly formed along the minute irregularities on the surface of the copper foil. Therefore, for example, when a roughening layer is formed on the surface of the copper foil, this means that there are few areas where roughening particles overgrow on the convex portions and where no roughening particles are formed in the concave portions. In other words, when the Str of the surface treatment layer is 0.20 to 0.40, the overgrowth of roughening particles formed on the convex portions of the copper foil is suppressed, and roughening particles are also formed in the concave portions of the copper foil. As a result, the anchoring effect of the roughening particles can be sufficiently ensured, thereby increasing the adhesive strength between the surface-treated copper foil and the resin substrate. From the viewpoint of stably obtaining such effects, the Str of the surface treatment layer is preferably 0.26 to 0.35. The Str of the surface treatment layer is measured in accordance with ISO 25178-2:2012.

[0019] The surface treatment layer preferably has an arithmetic mean height (Sa) of 0.18 to 0.43 μm. Sa is a parameter in the height direction defined in ISO 25178-2:2012, and represents the average height difference from the mean plane. If the Sa of the surface-treated layer is large, the surface of the surface-treated layer becomes rough, making it easier to exhibit an anchoring effect when the surface-treated copper foil is bonded to a resin substrate. On the other hand, if a copper-clad laminate is fabricated by bonding a surface-treated copper foil with a surface-treated copper foil having a surface-treated layer with a large Sa (i.e., a rough surface) to a resin substrate, transmission loss increases due to the skin effect of the surface-treated copper foil. Therefore, by setting the Sa of the surface-treated layer within the above range, a balance can be achieved between ensuring the adhesive strength of the surface-treated copper foil to the resin substrate and suppressing transmission loss. From the viewpoint of stably obtaining such effects, the lower limit of Sa of the surface-treated layer is preferably 0.20 μm, more preferably 0.23 μm, and even more preferably 0.24 μm, and the upper limit is preferably 0.40 μm, more preferably 0.35 μm.

[0020] The surface treatment layer preferably has a root mean square height (Sq) of 0.26 to 0.53 μm. Sq is a parameter in the height direction defined in ISO 25178-2:2012, and represents the variation in height of the convex portions on the surface of the surface treatment layer. If the Sq of the surface treatment layer is large, the variation in the height of the protrusions on the surface of the surface treatment layer increases, making it easier to achieve the anchoring effect when the surface-treated copper foil is bonded to a resin substrate. However, if the Sq is too large (the variation in the height of the protrusions is too large), this may cause problems in terms of quality control as an industrial product. Therefore, by setting the Sq of the surface treatment layer within the above range, it is possible to ensure a balance between ensuring the anchoring effect and quality control. From the viewpoint of stably obtaining such effects, the lower limit of the Sq of the surface treatment layer is preferably 0.29 μm, more preferably 0.30 μm, and even more preferably 0.34 μm, and the upper limit is preferably 0.48 μm, more preferably 0.43 μm. When emphasis is placed on suppressing transmission loss due to the skin effect and on easiness of quality control as an industrial product, the surface treatment layer preferably has Sa of 0.20 to 0.32 μm and Sq of 0.26 to 0.40 μm.

[0021] The surface treatment layer preferably has an Sdr (developed interface area ratio) of 30 to 79%, more preferably 38 to 79%. Sdr is a composite parameter defined in ISO 25178-2:2012 that represents the increase in surface area. In other words, it represents the increase in actual surface area relative to the area when a surface is viewed in plan. If the Sdr of the surface-treated layer is too large, the surface of the surface-treated layer becomes dense and has large undulations, which makes it easier to exhibit the anchoring effect when the surface-treated copper foil is bonded to a resin substrate, but increases transmission loss due to the skin effect. Therefore, by setting the Sdr of the surface-treated layer within the above range, it is possible to ensure a balance between ensuring the anchoring effect and suppressing transmission loss.

[0022] The type of the surface treatment layer is not particularly limited, and various surface treatment layers known in the art can be used. Examples of the surface treatment layer include a roughening treatment layer, a heat-resistant treatment layer, a rust-proofing treatment layer, a chromate treatment layer, and a silane coupling treatment layer. These layers can be used alone or in combination of two or more. Among these, it is preferable that the surface treatment layer contains a roughening treatment layer from the viewpoint of adhesion to the resin substrate. Furthermore, when the surface treatment layer contains one or more layers selected from the group consisting of a heat-resistant treatment layer, a rust-proofing treatment layer, a chromate treatment layer, and a silane coupling treatment layer, it is preferable that these layers are provided on the roughening treatment layer.

[0023] As an example, FIG. 1 shows a schematic enlarged cross-sectional view of a surface-treated copper foil having a roughened layer on one side of the copper foil. As shown in FIG. 1 , the roughened layer formed on one side of the copper foil 10 includes roughened particles 20 and a cover plating layer 30 that covers at least a portion of the roughened particles 20. The roughened particles 20 are formed not only on the convex portions 11 of the copper foil 10 but also on the concave portions 12. The roughened particles 20 formed on the convex portions 11 of the copper foil 10 are prevented from overgrowing by adding a trace amount of a tungsten compound to the plating solution. Therefore, the roughened particles 20 do not overgrow into large particles, but rather have a complex shape that grows in all directions. It is believed that such a structure can be achieved by controlling the parameters of the surface treatment layer, such as Sku and Str, within the above-mentioned ranges.

[0024] The roughening particles 20 are not particularly limited, but may be formed from a single element selected from the group consisting of copper, nickel, cobalt, phosphorus, tungsten, arsenic, molybdenum, chromium, and zinc, or an alloy containing two or more of these elements. Among these, the roughening particles 20 are preferably formed from copper or a copper alloy, and particularly preferably from copper. The cover plating layer 30 is not particularly limited, but may be formed from copper, silver, gold, nickel, cobalt, zinc, or the like.

[0025] The roughening treatment layer can be formed by electroplating. In particular, the roughening particles 20 can be formed by electroplating using a plating solution to which a trace amount of a tungsten compound is added. The tungsten compound is not particularly limited, but for example, sodium tungstate (Na2WO4) can be used. The content of the tungsten compound in the plating solution is preferably 1 ppm or more. Such a content can suppress overgrowth of the roughening particles 20 formed on the protrusions 11 and facilitate the formation of the roughening particles 20 in the recesses 12. The upper limit of the content of the tungsten compound is not particularly limited, but is preferably 20 ppm from the viewpoint of suppressing an increase in electrical resistance.

[0026] The electroplating conditions for forming the roughened layer are not particularly limited and may be adjusted depending on the electroplating apparatus used, but typical conditions are as follows: Note that each electroplating step may be performed once or multiple times. (Conditions for forming roughening particles 20) Plating solution composition: 5-15g / L Cu, 40-100g / L sulfuric acid, 1-6ppm sodium tungstate Plating solution temperature: 20~50℃ Electroplating conditions: current density 30~90A / dm 2 , time 0.1 to 8 seconds

[0027] (Conditions for forming the cover plating layer 30) Plating solution composition: 10-30g / L Cu, 70-130g / L sulfuric acid Plating solution temperature: 30 to 60°C Electroplating conditions: current density 4.8~15A / dm 2 , time 0.1 to 8 seconds

[0028] The heat-resistant layer and the rust-proofing layer are not particularly limited and can be formed from materials known in the technical field. Note that the heat-resistant layer may also function as a rust-proofing layer, so a single layer having both the functions of the heat-resistant layer and the rust-proofing layer may be formed. The heat-resistant and / or rust-proofing layer may be a layer containing one or more elements (which may be in any form such as metal, alloy, oxide, nitride, or sulfide) selected from the group consisting of nickel, zinc, tin, cobalt, molybdenum, copper, tungsten, phosphorus, arsenic, chromium, vanadium, titanium, aluminum, gold, silver, platinum group elements, iron, and tantalum. Of these, the heat-resistant and / or rust-proofing layer is preferably a Ni-Zn layer.

[0029] The heat-resistant and rust-proof layers can be formed by electroplating. The conditions are not particularly limited and can be adjusted depending on the electroplating equipment used. However, the conditions for forming a heat-resistant layer (Ni-Zn layer) using a general electroplating equipment are as follows. Electroplating may be performed once or multiple times. Plating solution composition: 1 to 30 g / L Ni, 1 to 30 g / L Zn Plating solution pH: 2 to 5 Plating solution temperature: 30~50℃ Electroplating conditions: current density 0.1~10A / dm 2 , time 0.1 to 5 seconds

[0030] The chromate treatment layer is not particularly limited, and can be formed from materials known in the art. Here, in this specification, the term "chromate-treated layer" refers to a layer formed with a solution containing chromic anhydride, chromic acid, dichromate, or dichromate. The chromate-treated layer can be a layer containing elements such as cobalt, iron, nickel, molybdenum, zinc, tantalum, copper, aluminum, phosphorus, tungsten, tin, arsenic, and titanium (which may be in any form, such as a metal, alloy, oxide, nitride, or sulfide). Examples of chromate-treated layers include chromate-treated layers treated with an aqueous solution of chromic anhydride or potassium dichromate, and chromate-treated layers treated with a treatment solution containing chromic anhydride or potassium dichromate and zinc.

[0031] The chromate treatment layer can be formed by a known method such as immersion chromate treatment or electrolytic chromate treatment. The conditions are not particularly limited, but for example, the conditions for forming a general chromate treatment layer are as follows. The chromate treatment may be performed once or multiple times. Chromate solution composition: 1-10g / L K2Cr2O7, 0.01-10g / L Zn Chromate solution pH: 2 to 5 Chromate solution temperature: 30~55℃ Electrolysis conditions: current density 0.1~10A / dm2 , time 0.1 to 5 seconds (for electrolytic chromate treatment)

[0032] The silane coupling treatment layer is not particularly limited, and can be formed from a material known in the art. In this specification, the term "silane coupling treatment layer" means a layer formed with a silane coupling agent. The silane coupling agent is not particularly limited, and those known in the art can be used. Examples of silane coupling agents include amino-based silane coupling agents, epoxy-based silane coupling agents, mercapto-based silane coupling agents, methacryloxy-based silane coupling agents, vinyl-based silane coupling agents, imidazole-based silane coupling agents, and triazine-based silane coupling agents. Among these, amino-based silane coupling agents and epoxy-based silane coupling agents are preferred. The above silane coupling agents can be used alone or in combination of two or more. A typical method for forming the silane coupling treatment layer is to apply a 1 to 3% by volume aqueous solution of the above-mentioned silane coupling agent and dry it to form the silane coupling treatment layer.

[0033] The copper foil 10 is not particularly limited, and may be either an electrolytic copper foil or a rolled copper foil. Electrodeposited copper foil is generally produced by electrolytically depositing copper from a copper sulfate plating bath onto a titanium or stainless steel drum. It has a flat S-side (shine side) formed on the rotating drum side and an M-side (matte side) formed on the opposite side of the S-side. The M-side of electrodeposited copper foil generally has minute irregularities. Furthermore, the S-side of electrodeposited copper foil also has minute irregularities due to the transfer of polishing marks from the rotating drum during polishing. Furthermore, rolled copper foil has minute irregularities on its surface due to the formation of oil pits by rolling oil during rolling.

[0034] The material of the copper foil 10 is not particularly limited. However, when the copper foil 10 is a rolled copper foil, high-purity copper such as tough pitch copper (JIS H3100 alloy number C1100) or oxygen-free copper (JIS H3100 alloy number C1020 or JIS H3510 alloy number C1011), which are commonly used for circuit patterns on printed wiring boards, can be used. Also usable are copper alloys such as Sn-containing copper, Ag-containing copper, copper alloys containing Cr, Zr, or Mg, and Corson copper alloys containing Ni and Si. In this specification, the term "copper foil 10" is intended to encompass copper alloy foils.

[0035] The thickness of the copper foil 10 is not particularly limited, but can be, for example, 1 to 1000 μm, alternatively 1 to 500 μm, alternatively 1 to 300 μm, alternatively 3 to 100 μm, alternatively 5 to 70 μm, alternatively 6 to 35 μm, or alternatively 9 to 18 μm.

[0036] The surface-treated copper foil having the above-described configuration can be produced according to a method known in the art. Here, the parameters of the surface treatment layer, such as Sku and Str, can be controlled by adjusting the conditions for forming the surface treatment layer, particularly the conditions for forming the roughened treatment layer.

[0037] When the surface-treated copper foil according to the embodiment of the present invention is subjected to an acid decomposition treatment to form a solution and the tungsten content in the solution is measured by inductively coupled plasma mass spectrometry, the tungsten content is preferably 1.0×12 / t to 4.0×12 / t [ppm] (t is the thickness of the copper foil 10). If the tungsten content is within this range, the Sku and Str of the surface treatment layer can be controlled within the above ranges. When the copper foil 10 is made from high-purity copper, such as tough-pitch copper or oxygen-free copper, or a copper alloy containing Sn, Ag, Cr, Zr, or Mg, which are commonly used for circuit patterns on printed wiring boards, the copper foil 10 typically does not contain W. Therefore, the tungsten content of the surface treatment layer can be estimated by analyzing a solution of a surface-treated copper foil containing the copper foil 10 and calculating the amount of tungsten based on the amount obtained, taking into account the thickness of the copper foil 10. The above formula is the estimation method. The solution by acid decomposition treatment is carried out by dissolving a 10 cm square piece of surface-treated copper foil in a mixture of nitric acid and hydrofluoric acid, and then diluting the solution. Inductively coupled plasma mass spectrometry can be performed using an inductively coupled plasma mass spectrometer (ICP-MS).

[0038] The surface-treated copper foil according to an embodiment of the present invention has a surface treatment layer with Sku controlled to 2.50 to 4.50 and Str controlled to 0.20 to 0.40, thereby improving adhesion to resin substrates, particularly resin substrates suitable for high-frequency applications.

[0039] A copper clad laminate according to an embodiment of the present invention comprises the above-described surface-treated copper foil and a resin substrate adhered to the surface treatment layer of the surface-treated copper foil. This copper-clad laminate can be produced by adhering a resin substrate to the surface-treated layer of the above-mentioned surface-treated copper foil. The resin substrate is not particularly limited, and those known in the art can be used. Examples of the resin substrate include a paper substrate with a phenolic resin, a paper substrate with an epoxy resin, a synthetic fiber cloth substrate with an epoxy resin, a glass cloth / paper composite substrate with an epoxy resin, a glass cloth / glass nonwoven fabric composite substrate with an epoxy resin, a glass cloth substrate with an epoxy resin, a polyester film, a polyimide resin, a liquid crystal polymer, and a fluororesin. Among these, a polyimide resin is preferred as the resin substrate.

[0040] The method for bonding the surface-treated copper foil to the resin substrate is not particularly limited and can be performed according to a method known in the art. For example, the surface-treated copper foil and the resin substrate may be laminated and thermocompressed together. The copper clad laminate produced as described above can be used in the production of printed wiring boards.

[0041] The copper clad laminate according to the embodiment of the present invention uses the above-mentioned surface-treated copper foil, and therefore can improve adhesion to resin substrates, particularly resin substrates suitable for high frequency applications.

[0042] A printed wiring board according to an embodiment of the present invention includes a circuit pattern formed by etching the surface-treated copper foil of the above-described copper-clad laminate. This printed wiring board can be produced by etching the surface-treated copper foil of the copper-clad laminate to form a circuit pattern. The method for forming the circuit pattern is not particularly limited, and known methods such as subtractive and semi-additive methods can be used. Among these, the subtractive method is preferred as the method for forming the circuit pattern.

[0043] When a printed wiring board is manufactured by the subtractive method, it is preferably carried out as follows. First, a resist is applied to the surface of the surface-treated copper foil of a copper-clad laminate, followed by exposure and development to form a predetermined resist pattern. Next, the surface-treated copper foil in the areas where the resist pattern is not formed (unnecessary areas) is removed by etching to form a circuit pattern. Finally, the resist pattern on the surface-treated copper foil is removed. The conditions for this subtractive method are not particularly limited, and the method can be carried out according to conditions known in the art.

[0044] The printed wiring board according to the embodiment of the present invention uses the above-mentioned copper-clad laminate, and therefore has excellent adhesion between the resin substrate, particularly a resin substrate suitable for high frequency applications, and the circuit pattern. [Example]

[0045] Hereinafter, the embodiments of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples in any way.

[0046] (Example 1) A rolled copper foil (thickness 12 μm) was prepared. After degreasing and pickling one surface, a surface-treated copper foil was obtained by sequentially forming a roughened treatment layer as the surface treatment layer, a Ni-Zn layer as the heat-resistant treatment layer, a chromate treatment layer, and a silane coupling treatment layer. The formation conditions for each treatment layer were as follows. (1) Roughened treatment layer (Formation conditions of roughened particles) Plating solution composition: 11 g / L of Cu, 50 g / L of sulfuric acid, 1 ppm of tungsten (derived from sodium tungstate dihydrate) Plating solution temperature: 27 °C Electroplating conditions: Current density 38.8 A / dm 2 , time 1.3 seconds Number of electroplating treatments: 2 times

[0047] (Formation conditions of overlay plating layer) Plating solution composition: 20 g / L of Cu, 100 g / L of sulfuric acid Plating solution temperature: 50 °C Electroplating conditions: Current density 8.2 A / dm 2 , time 1.4 seconds Number of electroplating treatments: 2 times

[0048] (2) Heat-resistant treatment layer (Formation conditions of Ni-Zn layer) Plating solution composition: 23.5 g / L of Ni, 4.5 g / L of Zn Plating solution pH: 3.6 Plating solution temperature: 40 °C Electroplating conditions: Current density 0.6 A / dm 2 , time 0.7 seconds Number of electroplating treatments: 1 time

[0049] (3) Chromate treatment layer (Formation conditions of electrolytic chromate treatment layer) Chromate solution composition: 3 g / L of K2Cr2O7, 0.33 g / L of Zn Chromate solution pH: 3.7 Chromate solution temperature: 55 °C Electrolysis conditions: current density 1.4A / dm 2 , time 0.7 seconds Number of chromate treatments: 2 times

[0050] (4) Silane coupling treatment layer A 1.2% by volume aqueous solution of N-2-(aminoethyl)-3-aminopropyltrimethoxysilane was applied and dried to form a silane coupling treatment layer.

[0051] Example 2 A surface-treated copper foil was obtained under the same conditions as in Example 1, except that the amount of tungsten in the plating solution composition was changed to 2 ppm in the roughening particle formation conditions.

[0052] Example 3 A surface-treated copper foil was obtained under the same conditions as in Example 1, except that the amount of tungsten in the plating solution composition was changed to 3 ppm in the roughening particle formation conditions.

[0053] Example 4 A surface-treated copper foil was obtained under the same conditions as in Example 1, except that the amount of tungsten in the plating solution composition was changed to 4 ppm in the roughening particle formation conditions.

[0054] Example 5 A surface-treated copper foil was obtained under the same conditions as in Example 1, except that the amount of tungsten in the plating solution composition was changed to 5 ppm in the roughening particle formation conditions.

[0055] Example 6 A surface-treated copper foil was obtained under the same conditions as in Example 1, except that the amount of tungsten in the plating solution composition was changed to 6 ppm in the roughening particle formation conditions.

[0056] Example 7 The same rolled copper foil as in Example 1 was prepared. After degreasing and pickling one surface, a surface treatment copper foil was obtained by sequentially forming a roughened treatment layer as the surface treatment layer, a Ni-Zn layer as the heat-resistant treatment layer, a chromate treatment layer, and a silane coupling treatment layer. The formation conditions for each treatment layer were as follows. (1) Roughened treatment layer <Formation conditions of roughened particles> Plating solution composition: 11 g / L of Cu, 50 g / L of sulfuric acid, 5 ppm of tungsten (derived from sodium tungstate dihydrate) Plating solution temperature: 27 °C Electroplating conditions: Current density 46.8 A / dm 2 , time 1.0 second Number of electroplating treatments: 2 times

[0057] <Formation conditions of overlay plating layer> Plating solution composition: 20 g / L of Cu, 100 g / L of sulfuric acid Plating solution temperature: 50 °C Electroplating conditions: Current density 8.2 A / dm 2 , time 1.4 seconds Number of electroplating treatments: 2 times

[0058] (2) Heat-resistant treatment layer <Formation conditions of Ni-Zn layer> Plating solution composition: 23.5 g / L of Ni, 4.5 g / L of Zn Plating solution pH: 3.6 Plating solution temperature: 40 °C Electroplating conditions: Current density 0.7 A / dm 2 , time 0.7 second Number of electroplating treatments: 1 time

[0059] (3) Chromate treatment layer <Formation conditions of electrolytic chromate treatment layer> Chromate solution composition: 3 g / L of K2Cr2O7, 0.33 g / L of Zn Chromate solution pH: 3.7 Chromate solution temperature: 55 °C Electrolysis conditions: Current density 1.5 A / dm 2 , time 0.7 second Number of chromate treatments: 2 times

[0060] (4) Silane coupling treatment layer A 1.2% by volume aqueous solution of N-2-(aminoethyl)-3-aminopropyltrimethoxysilane was applied and dried to form a silane coupling treatment layer.

[0061] Example 8 The current density for forming the cover plating layer was 9.6A / dm 2 A surface-treated copper foil was obtained under the same conditions as in Example 7, except that the above-mentioned conditions were changed.

[0062] Example 9 Under the roughening particle formation conditions, the current density was set to 46.0 A / dm 2 The current density under the conditions for forming the cover plating layer was 9.6A / dm 2 and the current density was 0.9 A / dm under the conditions for forming the Ni-Zn layer. 2 A surface-treated copper foil was obtained under the same conditions as in Example 7, except that the above conditions were changed to the following:

[0063] Example 10 A rolled copper foil (thickness: 12 μm) was prepared, one side was degreased and pickled, and then a roughening treatment layer as a surface treatment layer, a Ni-Zn layer as a heat-resistant treatment layer, a chromate treatment layer, and a silane coupling treatment layer were sequentially formed to obtain a surface-treated copper foil. The formation conditions for each treatment layer were as follows. (1) Roughened layer <Conditions for forming roughening particles> Plating solution composition: 12 g / L Cu, 50 g / L sulfuric acid, 5 ppm tungsten (derived from sodium tungstate dihydrate) Plating solution temperature: 27℃ Electroplating conditions: current density 48.3A / dm 2 , time 0.81 seconds Number of electroplating treatments: 2

[0064] <Conditions for forming the cover plating layer> Plating solution composition: 20g / L Cu, 100g / L sulfuric acid Plating solution temperature: 50 °C Electroplating conditions: Current density 11.9 A / dm 2 , time 1.15 seconds Number of electroplating treatments: 2 times

[0065] (2) Heat-resistant treatment layer <Formation conditions of Ni-Zn layer> Plating solution composition: 23.5 g / L of Ni, 4.5 g / L of Zn Plating solution pH: 3.6 Plating solution temperature: 40 °C Electroplating conditions: Current density 1.07 A / dm 2 , time 0.59 seconds Number of electroplating treatments: 1 time

[0066] (3) Chromate treatment layer <Formation conditions of electrolytic chromate treatment layer> Chromate solution composition: 3 g / L of K2Cr2O7, 0.33 g / L of Zn Chromate solution pH: 3.65 Chromate solution temperature: 55 °C Electrolysis conditions: Current density 1.91 A / dm 2 , time 0.59 seconds Number of chromate treatments: 2 times

[0067] (4) Silane coupling treatment layer A 1.2% by volume aqueous solution of N-2-(aminoethyl)-3-aminopropyltrimethoxysilane was applied and dried to form a silane coupling treatment layer.

[0068] (Comparative Example 1) The rolled copper foil (copper foil without surface treatment) used in Example 1 was used for comparison.

[0069] (Comparative Example 2) A surface-treated copper foil was obtained under the same conditions as in Example 1, except that the amount of tungsten in the plating solution composition was set to 0 ppm (sodium tungstate was not added) in the formation conditions of the roughened particles.

[0070] For the surface-treated copper foil or copper foil obtained in the above Examples and Comparative Examples, the following characteristic evaluations were performed. <Sku, Str, Sa, Sq and Sdr> Imaging was performed using a laser microscope (LEXT OLS4000) manufactured by Olympus Corporation. Analysis of the captured images was performed using the analysis software of a laser microscope (LEXT OLS4100) manufactured by Olympus Corporation. The measurements of Sku, Str, Sa, Sq and Sdr were performed in accordance with ISO 25178-2:2012, respectively. Also, the average value of the values measured at five arbitrary locations was used as the measurement result. The temperature during measurement was 23 to 25 °C. The main setting conditions for the laser microscope and analysis software are as follows. Objective lens: MPLAPON50XLEXT (Magnification: 50 times, Numerical aperture: 0.95, Immersion type: Air, Mechanical tube length: ∞, Cover glass thickness: 0, Field number: FN18) Optical zoom magnification: 1 time Scanning mode: XYZ high-precision (Height resolution: 60 nm, Number of pixels of captured data: 1024 × 1024) Captured image size [Number of pixels]: Horizontal 257 μm × Vertical 258 μm [1024 × 1024] (For measurement in the horizontal direction, the evaluation length corresponds to 257 μm) DIC: Off Multilayer: 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, λs and λf are none Filter: Gaussian filter Noise removal: Pretreatment before measurement Surface (tilt) correction: Performed Brightness: Adjusted to be in the range of 30 to 50 The brightness should be set appropriately depending on the color tone of the object being measured. The above settings are appropriate for measuring the surface of surface-treated copper foil with L* of -69 to -10, a* of 2 to 32, and b* of 221. Here, the λs filter corresponds to the S filter in ISO 25178-2:2012, and the λc filter corresponds to the L filter in ISO 25178-2:2012.

[0071] <Measuring the color tone of the object> Using a MiniScan (registered trademark) EZ Model 4000L manufactured by HunterLab, measurements of L*, a*, and b* in the CIE L*a*b* color system were carried out in accordance with JIS Z8730:2009. Specifically, the surface of the surface-treated copper foil or copper foil to be measured obtained in the above Examples and Comparative Examples was pressed against the photosensitive part of the measuring instrument, and measurements were carried out while preventing light from entering from outside. Furthermore, measurements of L*, a*, and b* were carried out based on geometric condition C of JIS Z8722:2009. The main conditions of the measuring instrument are as follows: Optical system: d / 8°, integrating sphere size: 63.5mm, observation light source: D65 Measurement method: reflection Lighting diameter: 25.4mm Measuring diameter: 20.0 mm Measurement wavelength / interval: 400~700nm / 10nm Light source: Pulsed xenon lamp, 1 light emission / measurement Traceability standards: National Institute of Standards and Technology (NIST) compliant calibration based on CIE 44 and ASTM E259 Standard observer: 10° The white tiles used as the measurement standards were the following object colors: When measured at D65 / 10°, the CIE XYZ color system values ​​are X: 81.90, Y: 87.02, and Z: 93.76

[0072] <Tungsten (W) content> The surface-treated copper foil or copper foil was subjected to acid decomposition treatment to form a solution, and the tungsten content in the solution was measured by inductively coupled plasma mass spectrometry. The solution forming conditions were the same as those described above. This evaluation was not performed for Examples 7 to 9 because the W concentration in the surface treatment layer was considered to be equivalent to that of Example 5. Furthermore, this evaluation was not performed for Example 10, so the W concentration in the surface treatment layer is unknown.

[0073] <Peel strength> After laminating the surface-treated copper foil to a polyimide resin substrate, a 3 mm-wide circuit was formed in the MD direction (the longitudinal direction of the rolled copper foil). The circuit was formed according to a conventional method. Next, the strength (MD 90° peel strength) when the circuit (surface-treated copper foil) was peeled off from the surface of the resin substrate at a speed of 50 mm / min in a 90° direction, i.e., vertically upward relative to the surface of the resin substrate, was measured according to JIS C6471:1995. The measurement was performed three times, and the average value was used as the peel strength result. A peel strength of 0.50 kgf / cm or higher indicates good adhesion between the circuit (surface-treated copper foil) and the resin substrate. The copper foil of Comparative Example 1 was not subjected to this evaluation because it could not be bonded to a polyimide resin substrate.

[0074] The results of the above characteristic evaluation are shown in Table 1.

[0075] [Table 1]

[0076] As shown in Table 1, the surface-treated copper foils of Examples 1 to 10, in which the Sku and Str of the surface-treated layer were within the predetermined ranges, had high peel strength. On the other hand, the surface-treated copper foil of Comparative Example 2, whose Sku was outside the specified range, had a low peel strength, although the Sa of the surface-treated layer was equivalent to that of the surface-treated copper foils of Examples 1 to 10. In general, the larger the Sa of the surface-treated layer, the better the adhesion to the resin substrate. Considering this, this result, that the peel strength was improved by controlling Sku and Str while the Sa was approximately equivalent, was surprising. A comparison of the surface-treated copper foils of Examples 1 to 10 and the copper foil of Comparative Example 1 reveals that the Str values ​​are very similar. Considering that the surface-treated copper foils of Examples 1 to 10 are the copper foil of Comparative Example 1 that has been surface-treated, and that Str represents the anisotropy and isotropy of the surface, it can be seen that, as already mentioned, the surface-treated copper foil according to the embodiment of the present invention has a surface treatment layer, particularly a roughening particle layer, formed uniformly along the minute irregularities on the copper foil surface (oil pits in the case of rolled copper foil). If the roughening particle layer were not formed along the minute irregularities, the Str value would be significantly different before and after the surface treatment. The W content of Comparative Example 2 is 0.4 ppm, which is believed to be due to the fact that W unintentionally remained in one of the plating solutions used to form the surface treatment layer when the surface-treated copper foil of Comparative Example 2 was produced. The present inventors believe that W did not remain in the plating solution used to form the roughened treatment layer, but rather in the plating solutions used to form the other surface treatment layers.

[0077] As can be seen from the above results, embodiments of the present invention can provide a surface-treated copper foil that can improve adhesion to a resin substrate, particularly a resin substrate suitable for high-frequency applications. Furthermore, embodiments of the present invention can provide a surface-treated copper foil in which roughening particles are formed along the minute irregularities on the copper foil surface. Furthermore, embodiments of the present invention can provide a copper-clad laminate that has excellent adhesion between a resin substrate, particularly a resin substrate suitable for high-frequency applications, and the surface-treated copper foil. Furthermore, embodiments of the present invention can provide a printed wiring board that has excellent adhesion between a resin substrate, particularly a resin substrate suitable for high-frequency applications, and the circuit pattern. [Explanation of symbols]

[0078] 10 Copper foil 11 Convex part 12 recess 20 Roughening particles 30 Cover plating layer

Claims

1. A copper foil and a surface treatment layer formed on at least one surface of the copper foil, The surface-treated copper foil has a surface-treated layer having an Sku of 2.50 to 4.50 and an Str of 0.20 to 0.

40.

2. The surface-treated copper foil according to claim 1, wherein the Sku is 2.80 to 4.00 and the Str is 0.26 to 0.

35.

3. The surface-treated copper foil according to claim 1 or 2, wherein the surface treatment layer has an Sa of 0.18 to 0.43 μm.

4. The surface-treated copper foil according to any one of claims 1 to 3, wherein the surface treatment layer has an Sq of 0.26 to 0.53 µm.

5. The surface-treated copper foil according to claim 1 or 2, wherein the surface treatment layer has an Sa of 0.20 to 0.32 μm and an Sq of 0.26 to 0.40 μm.

6. The surface-treated copper foil according to any one of claims 1 to 5, wherein the surface treatment layer has an Sdr of 30 to 79%.

7. The surface-treated copper foil according to any one of claims 1 to 6, wherein when the surface-treated copper foil is subjected to acid decomposition treatment to form a solution and the tungsten content in the solution is measured by inductively coupled plasma mass spectrometry, the tungsten content is 1.0 x 12 / t to 4.0 x 12 / t [ppm] (t is the thickness of the copper foil).

8. The surface-treated copper foil according to any one of claims 1 to 7, wherein the surface treatment layer contains a roughening treatment layer.

9. A copper-clad laminate comprising the surface-treated copper foil according to any one of claims 1 to 8 and a resin substrate adhered to the surface treatment layer of the surface-treated copper foil.

10. A printed wiring board comprising a circuit pattern formed by etching the surface-treated copper foil of the copper-clad laminate according to claim 9.

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