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

Abstract

Provided is a surface-treated copper foil including a copper foil and a surface-treated layer formed on at least one surface of the copper foil. The average depth Svk in valley parts in the surface-treated layer is 0.35 to 0.63 μm.

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 become faster and larger in communication speed and capacity, leading to an increase in the frequency of electrical signals, and flexible printed wiring boards that can accommodate this are in demand. In particular, the higher the frequency of the electrical signal, the greater the loss (attenuation) of signal power, making it more difficult to read data. For this reason, 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. In the high frequency range, current has the property of flowing on the surface of a conductor (i.e., the skin effect). Therefore, if the copper foil surface is rough, the current will flow along a complex path. Therefore, in order 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 in this specification, they mainly mean "transmission loss of high frequency signals" and "conductor loss of high frequency signals."

[0005] Dielectric loss depends on the type of resin substrate. For this reason, 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. Dielectric loss is also affected by the adhesive used to bond the copper foil to the resin substrate. For this reason, it is desirable to bond the copper foil to the resin substrate without using an adhesive. Therefore, in order to bond the copper foil and the resin substrate without 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 recesses 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 a roughening treatment layer is formed, current concentrates around the convex parts, causing the roughening particles to overgrow, while current is insufficient around the concave parts, making it difficult for the roughening particles to grow. As a result, coarse roughening particles are formed around the convex parts of the copper foil, while the roughening particles are too small or not formed around 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 present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a surface-treated copper foil capable of improving 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] In order to solve the above problems, the present inventors have conducted extensive research into surface-treated copper foils. As a result, based on the finding that the state of formation of the surface treatment layer on the copper foil (particularly the state of formation of roughening particles around minute recesses in the copper foil) is related to the average depth Svk of the valleys of the surface treatment layer, they have found that the adhesion between the surface-treated copper foil and the resin substrate can be improved by controlling the average depth Svk of the valleys of the surface treatment layer within a predetermined range.

[0010] That is, in one aspect, an embodiment of the present invention is a copper foil having a surface treatment layer formed on at least one surface of the copper foil, wherein the average depth Svk of the valleys of the surface treatment layer is 0.35 to 0.63 μm. The core volume Vmc of the surface treatment layer is 0.32 to 0.60 μm 3 / μm 2 is This relates to surface-treated copper foil. In another 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 average depth Svk of the valleys of the surface treatment layer is 0.35 to 0.63 μm, and the level difference Sk of the core portion of the surface treatment layer is 0.70 to 1.50 μm.

[0011] 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]

[0012] 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]

[0013] [Figure 1] 1 is a graph showing a typical load curve of a surface treatment layer. [Figure 2] FIG. 2 is a conceptual schematic diagram for explaining roughening particles formed on a copper foil and surface texture parameters. DETAILED DESCRIPTION OF THE INVENTION

[0014] 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.

[0015] The surface-treated copper foil according to an embodiment of the present invention comprises a copper foil and a surface treatment layer formed on at least one surface of the copper foil, and the average depth Svk of the valleys of the surface treatment layer is 0.35 to 0.63 μm. According to the above-mentioned constitution, it is possible to realize a surface-treated copper foil capable of improving adhesion to a resin substrate, particularly a resin substrate suitable for high frequency applications.

[0016] The surface treatment layer may be formed on only one side of the copper foil, or may be formed on both sides of the copper foil. When the surface treatment layer is formed on both sides of the copper foil, the type of the surface treatment layer may be the same or different. When the types of the surface treatment layers formed on both sides of the copper foil are different, for example, a surface treatment layer including a roughening layer is formed on one side of the copper foil, and a surface treatment layer not including a roughening layer is formed on the other side of the copper foil.

[0017] The surface profile of the surface treatment layer can be determined using surface texture parameters, which are obtained in accordance with ISO 25178-2:2012 by measuring the surface profile and analyzing the load curve calculated from the measurement data. Before explaining the load curve, the load area ratio will be explained. The area coverage ratio is a ratio obtained by dividing the area corresponding to the cross section of a three-dimensional object to be measured when the object is cut at a plane of a certain height by the area of ​​the measurement field. In this disclosure, the object to be measured is assumed to be a copper foil or a surface treatment layer of a surface-treated copper foil. The load curve is a curve that shows the areal load ratio at each height. The height near an areal load ratio of 0% represents the height of the highest part of the object being measured. The height near an areal load ratio of 100% represents the height of the lowest part of the object being measured.

[0018] FIG. 1 is a graph showing a typical load curve of a surface treatment layer. The load curve can be used to express the volume of the solid part and the volume of the void part of the surface treatment layer. The volume of the solid part corresponds to the volume of the part occupied by the solid part of the object to be measured in the measurement field of view. The volume of the void part corresponds to the volume occupied by the space between the solid parts in the measurement field of view. The load curve described in the present disclosure is divided into a valley portion, a core portion, and a peak portion, with the areal load ratios of 10% and 80% as boundaries. 1, the following describes each parameter in relation to the surface treatment layer according to the embodiment of the present invention. Vvv denotes the volume of the voids in the valleys of the surface treatment layer, Vvc denotes the volume of the voids in the core of the surface treatment layer, Vmp denotes the volume of the solid part of the peaks of the surface treatment layer, and Vmc denotes the volume of the solid part of the core of the surface treatment layer. Sk denotes the level difference of the core of the surface treatment layer (the difference between the upper and lower limit levels of the core), Spk denotes the average height of the peaks of the surface treatment layer, and Svk denotes the average depth of the valleys of the surface treatment layer. The peaks are the high parts of the object to be measured, the valleys are the low parts of the object to be measured, and the core is the part of the object to be measured other than the peaks and valleys, i.e., the part with a height close to the average.

[0019] Here, the relationship between the roughening treatment layer and the surface property parameters will be specifically described, taking a roughening treatment layer made of roughening particles as an example of the surface treatment layer. Fig. 2 is a conceptual schematic diagram for explaining the roughening particles formed on the copper foil and the surface texture parameters. Fig. 2 illustrates an example in which the surface treatment layer is a roughening treatment layer (roughening particles), but it should be noted that the surface treatment layer is not limited to a roughening treatment layer. As shown in FIG. 2, minute depressions 15 such as oil pits exist on the surface of the copper foil 10. The roughening particles 20 formed on the surface of the copper foil 10 vary in size. Roughening particles A represent roughening particles 20 of average size. Roughening particles B represent roughening particles 20 that are smaller than roughening particles A. Roughening particles C represent roughening particles 20 that are larger than roughening particles A. Roughening particles B, which are smaller than roughening particles A, are formed around the depressions 15 because current does not easily flow around them during the roughening process.

[0020] In the surface-treated copper foil according to the embodiment of the present invention, roughening particles B are also formed around the recesses 15 of the copper foil 10. Therefore, it is believed that the roughening particles B formed around the recesses 15 make the valleys relatively deep, increasing the value of the average depth Svk of the valleys (hereinafter sometimes simply abbreviated as "Svk"). In contrast, in conventional surface-treated copper foils, it is difficult for the roughening particles B to form around the recesses 15 of the copper foil 10. Therefore, it is believed that the depth of the valleys essentially reflects the depth of the recesses 15, resulting in a small value of Svk. From the above viewpoints, the Svk of the surface treatment layer of the surface-treated copper foil according to the embodiment of the present invention is specified to be 0.35 to 0.63 μm. If the Svk is within this range, it can be said that the roughening particles are sufficiently formed around the minute recesses of the copper foil. In other words, the formation region (area) of the roughening particles that contribute to the adhesive strength with the resin substrate increases, thereby improving the adhesiveness between the surface-treated copper foil and the resin substrate. From the viewpoint of stably increasing the area where roughening particles are formed, the Svk of the surface treatment layer is preferably 0.37 to 0.56 μm, and more preferably 0.40 to 0.56 μm.

[0021] As explained above, Vmc represents the solid volume of the core of the surface treatment layer. That is, in FIG. 2, it corresponds to the volume of the roughening particle (20) at the position indicated by Sk and represents a portion of the volume of the roughening particle A of average size. Therefore, it is considered that the larger the solid volume Vmc of the core (hereinafter sometimes simply abbreviated as "Vmc"), the greater the amount of particles of average size attached. However, if Vmc is too large, the amount of coarse roughening particles C, which are larger than the roughening particles A, attached increases, which may increase transmission loss or cause stress to concentrate on the coarse roughening particles C, making them more susceptible to breakage, which may actually reduce their adhesive strength to the resin substrate. Therefore, in the surface-treated copper foil according to the embodiment of the present invention, Vmc of the surface treatment layer is 0.32 to 0.60 μm 3 / μm 2 If Vmc is in this range, it can be said that the adhesion amount of roughening particles A of average size is in an appropriate range. In other words, the formation region (area) of roughening particles A that contributes to the adhesive strength with the resin substrate is sufficiently secured, thereby improving the adhesiveness between the surface treatment layer and the resin substrate. From the viewpoint of stably securing the above effects, the Vmc of the surface treatment layer is set to 0.35 to 0.50 μm. 3 / μm 2 More preferably, 0.38 to 0.45 μm 3 / μm 2 is more preferred.

[0022] As explained above, Sk represents the level difference of the core portion of the surface treatment layer. That is, in FIG. 2, it represents a portion of the height of the roughening particles A of average size formed on the copper foil (10). That is, the level difference Sk of the core portion (hereinafter sometimes simply abbreviated as "Sk") represents a portion of the height of the roughening particles A that significantly contributes to the adhesion between the copper foil (10) and the resin substrate. Note that, in the surface-treated copper foil according to this embodiment, it is thought that the presence of the roughening particles B around the recesses (15) of the copper foil (10) increases the value of Svk while decreasing the value of Sk. Therefore, in the surface-treated copper foil according to the embodiment of the present invention, the Sk of the surface treatment layer is preferably 0.70 to 1.50 μm. If the Sk is within this range, the size of the roughening particles A, which greatly contributes to the adhesion between the surface treatment layer and the resin substrate, becomes appropriate, and when the surface treatment layer is adhered to the resin substrate, stress concentration on the roughening particles A, which causes breakage, can be suppressed. In other words, a decrease in adhesive strength to the resin substrate can be suppressed. From the viewpoint of stably ensuring the above effects, the thickness Sk of the surface treatment layer is more preferably 1.01 to 1.18 μm.

[0023] The amount of Zn attached in the surface treatment layer is not particularly limited, but is preferably 6 to 200 μm / dm 2 By controlling the Zn coating weight within this range, the solder heat resistance of the circuit pattern formed from the surface-treated copper foil can be improved. From the viewpoint of stably improving this effect, the Zn coating weight in the surface treatment layer is preferably 82 to 200 μm / dm 2 It is more preferable that: The Zn adhesion amount in the surface treatment layer can be measured by dissolving the surface treatment layer in 20% by mass nitric acid and performing quantitative analysis by atomic absorption spectrometry using an atomic absorption spectrophotometer (AA240FS, manufactured by VARIAN). When surface treatment layers are provided on both sides of the copper foil, the surface of the surface treatment layer that is not to be measured is protected, and then the surface treatment layer to be measured is dissolved and quantitatively analyzed.

[0024] The type of surface treatment layer is not particularly limited as long as it has the above-mentioned surface shape, and various surface treatment layers known in the art can be used. Examples of the surface treatment layer include a roughening treatment layer, a chemical-resistant treatment layer, a heat-resistant 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. When the surface treatment layer contains one or more layers selected from the group consisting of a chemical-resistant treatment layer, a heat-resistant 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.

[0025] The roughening treatment layer contains roughening particles. The roughening particles may include primary roughening particles and secondary roughening particles. The secondary roughening particles preferably have a different chemical composition from the primary roughening particles. It is preferable that a cover plating layer be formed on at least a portion of the surface of the primary roughening particles. The roughening particles may be formed from, but are not limited to, 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. Of these, the primary roughening particles are preferably formed from copper or a copper alloy, and particularly preferably from copper. The secondary roughening particles are preferably formed from an alloy containing copper, cobalt and nickel. The cover plating layer is not particularly limited, but can be formed from copper, silver, gold, nickel, cobalt, zinc, etc. Among these, it is preferable that the cover plating layer be formed from copper.

[0026] The roughened layer can be formed, for example, by performing a primary roughening treatment to form primary roughening particles, followed by cover plating to form a cover plating layer, and then a secondary roughening treatment to form secondary roughening particles. By performing the roughening treatment in this manner, it becomes easier to form a surface treatment layer having the above-described surface shape. Each particle and layer can be formed by electroplating. Specifically, the primary roughening particles can be formed by electroplating using a plating solution containing a trace amount of a tungsten compound. The cover plating layer and secondary roughening particles can be formed by electroplating using a plating solution containing specific components.

[0027] 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. This content prevents overgrowth of primary roughening particles formed on relatively smooth portions of the copper foil, and also facilitates the formation of primary roughening particles around recesses. The upper limit of the content of the tungsten compound is not particularly limited, but is preferably 20 ppm from the viewpoint of preventing an increase in electrical resistance.

[0028] 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 primary roughening particles) 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

[0029] (Conditions for forming the cover plating layer) 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

[0030] (Conditions for forming secondary roughening particles) Plating solution composition: 10-20g / L Cu, 5-15g / L Co, 5-15g / L Ni Plating solution temperature: 30~50℃ Electroplating conditions: current density 24~50A / dm 2 , time 0.3~0.8 seconds

[0031] The chemical-resistant treatment layer and the heat-resistant treatment layer are not particularly limited and can be formed from materials known in the technical field. Note that, since the chemical-resistant treatment layer may also function as a heat-resistant treatment layer, a single layer having the functions of both the chemical-resistant treatment layer and the heat-resistant treatment layer may be formed as the chemical-resistant treatment layer and the heat-resistant treatment layer. The chemical-resistant layer and / or heat-resistant 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. Among these, the chemical-resistant layer is preferably a Co-Ni layer. The heat-resistant layer is preferably a Ni-Zn layer.

[0032] The chemical-resistant layer and the heat-resistant layer 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 the chemical-resistant layer (Co-Ni layer) and the heat-resistant layer (Ni-Zn layer) using a general electroplating equipment are as follows. Note that the electroplating may be performed once or multiple times.

[0033] (Chemical-resistant layer: Co-Ni layer formation conditions) Plating solution composition: 1-8g / L Co, 5-20g / L Ni Plating solution pH: 2 to 3 Plating solution temperature: 40~60℃ Electroplating conditions: current density 1~20A / dm 2 , time 0.3~0.6 seconds

[0034] (Heat-resistant layer: Ni-Zn layer formation conditions) 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

[0035] 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 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 cobalt, iron, nickel, molybdenum, zinc, tantalum, copper, aluminum, phosphorus, tungsten, tin, arsenic, and titanium. 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.

[0036] 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 / dm 2 , time 0.1 to 5 seconds (for electrolytic chromate treatment)

[0037] 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.

[0038] The copper foil 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. Rolled copper foil has minute irregularities on its surface due to the formation of oil pits by rolling oil during rolling.

[0039] The material of the copper foil is not particularly limited. When the copper foil 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" is intended to encompass copper alloy foils.

[0040] When the copper foil is a rolled copper foil, the rolled copper foil may have a composition containing 99.0 mass% or more of Cu and 0.003 to 0.825 mass% of one or more elements selected from the group consisting of P, Ti, Sn, Ni, Be, Zn, In, and Mg, with the balance being unavoidable impurities. Alternatively, the rolled copper foil may have a composition containing 99.9 mass% or more of Cu and 0.0005 to 0.0220 mass% of P, with the balance being unavoidable impurities. Furthermore, the rolled copper foil may have a composition containing 99.0 mass% or more of Cu and the balance being unavoidable impurities. When the copper foil is a rolled copper foil, the average crystal grain size may be 0.5 to 4.0 μm, and the tensile strength in the rolling direction may be 235 to 290 MPa. Furthermore, the rolled copper foil may have a conductivity of 75% IACS or more. The conductivity of the copper foil can be measured at room temperature (25°C) by the four-terminal method in accordance with JIS H0505 (1975).

[0041] The thickness of the copper foil is not particularly limited, but can 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.

[0042] The surface-treated copper foil having the above-described configuration can be produced according to a method known in the art. Here, the surface property parameters such as Svk of the surface treatment layer can be controlled by adjusting the conditions for forming the surface treatment layer, particularly the conditions for forming the roughening treatment layer.

[0043] In the surface-treated copper foil according to the embodiment of the present invention, the Svk of the surface treatment layer is controlled to 0.35 to 0.63 μm, and therefore the adhesion to resin substrates, particularly resin substrates suitable for high frequency applications, can be improved.

[0044] 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. Furthermore, resin substrates particularly suitable for high-frequency applications include those made of low-dielectric materials. Examples of low-dielectric materials include liquid crystal polymers, low-dielectric polyimides, and fluororesins. The low-dielectric material may be, for example, a material having a dielectric constant of 3.5 or less at 1 MHz. The low-dielectric material suitable for high-frequency applications may be a material having a dielectric constant of 3.4 or less at 30 GHz.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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, and a predetermined resist pattern is formed by exposure and development. Next, the surface-treated copper foil in the areas where the resist pattern is not formed (i.e., 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.

[0049] 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]

[0050] 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.

[0051] (Example 1) A rolled copper foil with a thickness of 12 μm (HG foil manufactured by JX Metals Co., Ltd.) was prepared. After degreasing and pickling both sides of the copper foil, a surface-treated copper foil was obtained by sequentially forming a roughened treatment layer, a chemical-resistant treatment layer (Co-Ni layer), a heat-resistant treatment layer (Ni-Zn layer), a chromate treatment layer, and a silane coupling treatment layer on one side (hereinafter referred to as the "first side") as the surface treatment layer. The formation conditions of each treatment layer were as follows. (1) Roughened treatment layer / first side (Formation conditions of primary roughened particles) Plating solution composition: 12 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 39.5 A / dm 2 , time 1.2 seconds Number of electroplating treatments: 2 times

[0052] (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 9.6 A / dm 2 , time 1.8 seconds Number of electroplating treatments: 2 times

[0053] (Formation conditions of secondary roughened particles) Plating solution composition: 15.5 g / L of Cu, 7.5 g / L of Co, 9.5 g / L of Ni Plating solution temperature: 50 °C Electroplating conditions: Current density 33.3 A / dm 2 , time 0.55 seconds Number of electroplating treatments: 2 times

[0054] (2) Chemical-resistant treatment layer / first side (Formation conditions of Co-Ni layer) Plating solution composition: 3 g / L of Co, 13 g / L of Ni Plating solution pH: 2.0 Plating solution temperature: 50 °C Electroplating conditions: Current density 4.5 A / dm 2 , time 0.48 seconds Number of electroplating treatments: 1 time

[0055] (3) Heat-resistant treatment layer / First surface <Formation conditions of Ni-Zn layer> Plating solution composition: 23.5 g / L of Ni, 4.5 g / L of Zn pH of plating solution: 3.6 Temperature of plating solution: 40 °C Electroplating conditions: Current density 0.7 A / dm 2 , time 0.90 seconds Number of electroplating treatments: 1 time

[0056] (4) Chromate treatment layer / First surface <Formation conditions of electrolytic chromate treatment layer> Chromate solution composition: 3 g / L of K2Cr2O7, 0.33 g / L of Zn pH of chromate solution: 3.7 Temperature of chromate solution: 55 °C Electrolysis conditions: Current density 1.2 A / dm 2 , time 0.90 seconds Number of chromate treatments: 2 times

[0057] (5) Silane coupling treatment layer / First surface A 1.2% by volume aqueous solution of N-2-(aminoethyl)-3-aminopropyltrimethoxysilane was applied and dried to form a silane coupling treatment layer.

[0058] (Example 2) In the formation conditions of the primary roughened particles, the electroplating conditions were changed to a current density of 43.7 A / dm 2 , and in the formation conditions of the overlay plating layer, the electroplating conditions were changed to a current density of 12.3 A / dm 2 , time 1.8 seconds. Except for these changes, a surface-treated copper foil was obtained under the same conditions as in Example 1.

[0059] (Example 3) The conditions for forming the heat-resistant layer (Ni-Zn layer) on the first surface were electroplating conditions with a current density of 0.5 A / dm 2 A surface-treated copper foil was obtained under the same conditions as in Example 1, except that the heating time was changed to 0.90 seconds.

[0060] Example 4 No heat-resistant layer was formed on the first surface, and the chemical-resistant layer (Co-Ni layer) was formed under the electroplating conditions of a current density of 3.0 A / dm 2 A surface-treated copper foil was obtained under the same conditions as in Example 1, except for changing the temperature.

[0061] Example 5 No heat-resistant layer was formed on the first surface, and the electroplating conditions for the formation of the primary roughening particles were set to a current density of 35.2 A / dm 2 In addition, the electroplating conditions for forming the chemical-resistant layer (Co-Ni layer) were changed to a current density of 3.0 A / dm 2 A surface-treated copper foil was obtained under the same conditions as in Example 1, except for changing the temperature.

[0062] Example 6 No heat-resistant layer was formed on the first surface, and the electroplating conditions for the formation of the primary roughening particles were set at a current density of 42.9 A / dm 2 In addition, the electroplating conditions for forming the chemical-resistant layer (Co-Ni layer) were changed to a current density of 3.0 A / dm 2 A surface-treated copper foil was obtained under the same conditions as in Example 1, except for changing the temperature.

[0063] Example 7 No heat-resistant layer was formed on the first surface, and the electroplating conditions for the formation of the primary roughening particles were set at a current density of 46.7 A / dm 2 In addition, the electroplating conditions for forming the chemical-resistant layer (Co-Ni layer) were changed to a current density of 3.0 A / dm 2 A surface-treated copper foil was obtained under the same conditions as in Example 1, except for changing the temperature.

[0064] Example 8 No heat-resistant layer was formed on the first surface, and the electroplating conditions for forming secondary roughening particles were set at a current density of 28.9 A / dm 2 In addition, the electroplating conditions for forming the chemical-resistant layer (Co-Ni layer) were changed to a current density of 3.0 A / dm 2 A surface-treated copper foil was obtained under the same conditions as in Example 1, except for changing the temperature.

[0065] Example 9 No heat-resistant layer was formed on the first surface, and the electroplating conditions for forming secondary roughening particles were set at a current density of 37.7 A / dm 2 In addition, the electroplating conditions for forming the chemical-resistant layer (Co-Ni layer) were changed to a current density of 3.0 A / dm 2 A surface-treated copper foil was obtained under the same conditions as in Example 1, except for changing the temperature.

[0066] Example 10 No heat-resistant layer was formed on the first surface, and the electroplating conditions for forming secondary roughening particles were set at a current density of 42.1 A / dm 2 In addition, the electroplating conditions for forming the chemical-resistant layer (Co-Ni layer) were changed to a current density of 3.0 A / dm 2 A surface-treated copper foil was obtained under the same conditions as in Example 1, except for changing the temperature.

[0067] (Comparative Example 1) A 12 μm thick rolled copper foil (HG foil manufactured by JX Nippon Mining & Metals Corporation) was prepared, and after degreasing and pickling on both sides, a roughening treatment layer, a chemical-resistant treatment layer (Co-Ni layer), a chromate treatment layer, and a silane coupling treatment layer were sequentially formed on one side (first side) as surface treatment layers to obtain a surface-treated copper foil. The conditions for forming each treatment layer were as follows: (1) Roughened layer / first surface <Conditions for forming primary roughening particles> Plating solution composition: 12g / L Cu, 50g / L sulfuric acid Plating solution temperature: 25℃ Electroplating conditions: current density 45A / dm 2, Time: 0.68 seconds Number of electroplating processes: 2 times

[0068] <Formation conditions of the coating layer> Composition of the plating solution: 20 g / L of Cu, 100 g / L of sulfuric acid Temperature of the plating solution: 50 °C Electroplating conditions: Current density 4.9 A / dm 2 [[ID=1​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​A 1.2% by volume aqueous solution of N-2-(aminoethyl)-3-aminopropyltrimethoxysilane was applied and dried to form a silane coupling treatment layer.

[0072] The surface-treated copper foils obtained in the above examples and comparative examples were evaluated for the following properties. <Svk, Sk and Vmc of the surface treatment layer (first side)> Images were taken using a laser microscope (LEXT OLS4000) manufactured by Olympus Corporation. The captured images were analyzed using analysis software for a laser microscope (LEXT OLS4100) manufactured by Olympus Corporation. Measurements of Svk, Vmc, and Sk of the surface treatment layer were performed in accordance with ISO 25178-2:2012. The measurement results were calculated by averaging values ​​measured at 10 random locations. The temperature during measurement was 23 to 25°C. The main settings for the laser microscope and analysis software are as follows: Objective lens: MPLAPON50XLEXT (Magnification: 50x, Numerical Aperture: 0.95, Immersion Type: Air, Mechanical Tube Length: ∞, Cover Glass Thickness: 0, Field Number: FN18) Optical zoom magnification: 1x Scanning mode: XYZ high precision (height resolution: 60 nm, number of pixels of captured data: 1024 x 1024) Captured image size [pixels]: 257 μm wide x 258 μm high [1024 x 1024] (As the measurement is made in the horizontal direction, the evaluation length is equivalent to 257 μm) DIC: Off Multilayer: Off Laser Intensity: 100 Offset: 0 Confocal level: 0 Beam diameter aperture: Off Image average: 1 time Noise reduction: On Brightness correction: On Optical noise filter: On Cutoff: λc=200μm, λs and λf are none Filter: Gaussian filter Noise reduction: Measurement preprocessing Surface (tilt) correction: Implemented Brightness: Adjust to a range of 30-50 The brightness should be set appropriately depending on the color tone of the object to be 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 2 to 21.

[0073] <Measuring the color tone of the object> The measurement instrument used was a MiniScan (registered trademark) EZ Model 4000L manufactured by HunterLab, and 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 measurement surface of the surface-treated copper foil obtained in the above Examples and Comparative Examples was pressed against the photosensitive part of the measurement 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 measurement 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

[0074] <Peel strength> After laminating the surface-treated copper foil (first surface side) to a resin substrate made of a low-dielectric material, 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 180° peel strength) when the circuit (surface-treated copper foil) was peeled from the surface of the resin substrate in a 180° direction, i.e., in the MD direction, at a speed of 50 mm / min was measured in accordance with JIS C6471:1995. Five measurements were performed, and the average value was used as the peel strength result. A peel strength of 0.60 kgf / cm or higher indicates good adhesion between the circuit (surface-treated copper foil) and the resin substrate.

[0075] The results of the above characteristic evaluation are shown in Table 1.

[0076] [Table 1]

[0077] As shown in Table 1, the surface-treated copper foils of Examples 1 to 10, in which the Svk of the surface treatment layer was within the range of 0.35 to 0.63 μm, had higher peel strength than Comparative Example 1, in which the Svk of the surface treatment layer was outside the specified range.

[0078] Next, we investigated the effect of the amount of Zn deposited in the surface treatment layer on solder heat resistance.

[0079] Example 11 A surface-treated copper foil was obtained under the same conditions as in Example 1, except that no heat-resistant layer was formed on the first surface and that the immersion was carried out under the conditions for forming a chromate treatment layer without applying a current.

[0080] Example 12 No heat-resistant layer was formed on the first surface, and the electrolysis conditions for forming the chromate layer were set at a current density of 0.64 A / dm 2 A surface-treated copper foil was obtained under the same conditions as in Example 1, except for changing the temperature.

[0081] Example 13 No heat-resistant layer was formed on the first surface, and the electrolysis conditions for forming the chromate layer were set at a current density of 1.4 A / dm 2 A surface-treated copper foil was obtained under the same conditions as in Example 1, except for changing the temperature.

[0082] For the surface-treated copper foils obtained in the above examples, Svk, Sk, Vmc and peel strength were measured in the same manner as above, and the following evaluations were also made.

[0083] <Measurement of Zn adhesion amount on the surface treatment layer (first side)> The amount of Zn attached to the surface treatment layer (first side) was measured by dissolving the surface treatment layer (first side) in 20 mass% nitric acid and performing quantitative analysis by atomic absorption spectrometry using an atomic absorption spectrophotometer (AA240FS, manufactured by VARIAN).

[0084] <Solder heat resistance> The surface-treated copper foil was laminated to a resin substrate made of a low-dielectric material, and then etched to a size of 25 mm x 25 mm. Circuit formation was performed according to standard methods. Next, the sample was placed in a thermo-hygrostat and maintained at 85°C and 85% relative humidity for 48 hours. The sample was then floated in a solder bath containing solder at a specified temperature and removed after 30 seconds. The sample circuit was visually inspected for the presence of bubbles. If no bubbles were observed in the sample circuit, another sample was prepared, the solder temperature in the solder bath was increased, and the presence of bubbles in the sample circuit was inspected again. This procedure was repeated until bubbles appeared in the sample circuit. The evaluation results were expressed as the maximum temperature at which no bubbles were observed in the sample circuit. If the maximum temperature at which no bubbles were observed in the sample circuit was 290°C or higher, the sample had good solder heat resistance.

[0085] [Table 2]

[0086] As shown in Table 2, the surface-treated copper foils of Examples 11 to 13 had a surface treatment layer Svk in the range of 0.35 to 0.63 μm, similar to the surface-treated copper foils of Examples 1 to 10, and therefore had higher peel strength than the surface-treated copper foil of Comparative Example 1. Furthermore, the surface-treated copper foils of Examples 11 to 13 had a Zn coating weight in the surface treatment layer of 6 to 200 μm / dm 2 In particular, the Zn adhesion was 82 to 200 μm / dm 2 Examples 12 and 13, in which the soldering heat resistance was particularly excellent.

[0087] As can be seen from the above results, according to an embodiment 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. Furthermore, according to an embodiment of the present invention, a copper-clad laminate having excellent adhesion between a resin substrate, particularly a resin substrate suitable for high-frequency applications, and the surface-treated copper foil can be provided. Furthermore, according to an embodiment of the present invention, a printed wiring board having excellent adhesion between a resin substrate, particularly a resin substrate suitable for high-frequency applications, and a circuit pattern can be provided.

[0088] Therefore, the embodiment of the present invention can have the following aspects. [1] A copper foil and a surface treatment layer formed on at least one surface of the copper foil, The average depth Svk of the valleys of the surface treatment layer is 0.35 to 0.63 μm. [2] The surface-treated copper foil according to [1], wherein the average depth Svk of the valleys is 0.37 to 0.56 μm. [3] The surface-treated copper foil according to [1], wherein the average depth Svk of the valleys is 0.40 to 0.56 μm. [4] The core volume Vmc of the surface treatment layer is 0.32 to 0.60 μm 3 / μm 2 The surface-treated copper foil according to any one of [1] to [3], [5] The core volume Vmc of the surface treatment layer is 0.35 to 0.50 μm 3 / μm 2 The surface-treated copper foil according to any one of [1] to [3], wherein [6] The core volume Vmc of the surface treatment layer is 0.38 to 0.45 μm 3 / μm 2 The surface-treated copper foil according to any one of [1] to [3], wherein [7] The surface-treated copper foil according to any one of [1] to [6], wherein the level difference Sk of the core portion is 0.70 to 1.50 μm. [8] The surface-treated copper foil according to any one of [1] to [6], wherein the level difference Sk of the core portion is 1.01 to 1.18 μm. [9] The Zn coating weight of the surface treatment layer is 6 to 200 μm / dm 2 The surface-treated copper foil according to any one of [1] to [8], wherein

[10] The Zn coating weight of the surface treatment layer is 82 to 200 μm / dm 2 The surface-treated copper foil according to [9],

[11] The surface-treated copper foil according to any one of [1] to

[10] , wherein the surface treatment layer contains a roughening treatment layer.

[12] A copper clad laminate comprising the surface-treated copper foil according to any one of [1] to

[11] and a resin substrate adhered to the surface treatment layer of the surface-treated copper foil.

[13] A printed wiring board having a circuit pattern formed by etching the surface-treated copper foil of the copper-clad laminate described in

[12] . [Explanation of symbols]

[0089] 10 Copper foil 15 recess 20 Roughening particles

Claims

1. A copper foil and a surface treatment layer formed on at least one surface of the copper foil, the average depth Svk of the valleys of the surface treatment layer is 0.35 to 0.63 μm, The surface-treated copper foil has a core portion having a substantial volume Vmc of 0.32 to 0.60 μm 3 / μm 2 .

2. A substrate comprising a copper foil and a surface treatment layer formed on at least one surface of the copper foil, the average depth Svk of the valleys of the surface treatment layer is 0.35 to 0.63 μm, The surface-treated copper foil has a level difference Sk of 0.70 to 1.50 μm between the core and surface-treated layers.

3. The surface-treated copper foil according to claim 1 or 2, wherein the average depth Svk of the valleys is 0.37 to 0.56 μm.

4. The surface-treated copper foil according to claim 1 or 2, wherein the average depth Svk of the valleys is 0.40 to 0.56 μm.

5. The core volume Vmc of the surface treatment layer is 0.35 to 0.50 μm 3 / μm 2 The surface-treated copper foil according to claim 1,

6. The substantial volume Vmc of the core portion of the surface treatment layer is 0.38 to 0.45 μm 3 / μm 2 The surface-treated copper foil according to claim 1,

7. 2. The surface-treated copper foil according to claim 1, wherein the level difference Sk of the core portion is 0.70 to 1.50 μm.

8. The surface-treated copper foil according to claim 2 or 7, wherein the level difference Sk of the core portion is 1.01 to 1.18 μm.

9. The Zn deposition amount in the surface treatment layer is 6 to 200 μm / dm 2 The surface-treated copper foil according to claim 1 or 2,

10. The Zn deposition amount in the surface treatment layer is 82 to 200 μm / dm 2 The surface-treated copper foil according to claim 9,

11. The surface-treated copper foil according to claim 1 or 2, wherein the surface treatment layer comprises a roughening treatment layer.

12. A copper-clad laminate comprising the surface-treated copper foil according to claim 1 or 2 and a resin substrate adhered to the surface treatment layer of the surface-treated copper foil.

13. A printed wiring board comprising a circuit pattern formed by etching the surface-treated copper foil of the copper-clad laminate according to claim 12.

Images