Surface-treated copper foil, copper-clad laminate, and printed wiring board

Abstract

To provide a surface-treated copper foil capable of suppressing magnetization of a nickel layer even after predetermined heat treatment and exhibiting excellent transmission characteristics and heat resistance, and to provide a copper-clad laminate and a printed wiring board.SOLUTION: A surface-treated copper foil comprising: a copper foil substrate; and a surface treatment coating on at least one surface of the copper foil substrate, the surface treatment coating including a surface treatment layer containing nickel, wherein the surface-treated copper foil has a saturation flux density (Bs300) of 5.0 * 10 - 3T or less after heat treatment at 300 °C. for 2 hours.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Surface-treated copper foils are used in a variety of applications, such as copper foils for circuits in printed wiring boards and negative electrode current collectors in lithium-ion secondary batteries.

[0003] In particular, in the field of printed wiring boards, the recent trend toward smaller electronic devices and increased performance has led to higher density mounting of mounted components and higher signal frequencies, creating a demand for printed wiring boards with excellent high-frequency compatibility.

[0004] As the frequency of the copper foil used for circuits in such printed wiring boards increases, the surface condition of the circuit conductor, that is, the dissimilar metals treated on the surface, becomes more important due to the influence of the skin effect. In particular, nickel (Ni), which is widely used as a dissimilar metal, is a metal that exhibits ferromagnetic properties at room temperature. Therefore, when nickel is present on the surface of copper foil for circuits, the magnetic effect affects the current distribution and magnetic field distribution within the conductor, resulting in a problem of deterioration in the transmission characteristics of the surface-treated copper foil.

[0005] On the other hand, when producing a printed wiring board, it is necessary to bond a copper foil for circuits to a resin substrate, and in this case, good adhesion is required between the copper foil and the resin substrate, and in particular, heat-resistant adhesion (hereinafter sometimes simply referred to as "heat resistance"). Nickel on the surface of the copper foil for circuits plays an important role in achieving such heat resistance. That is, the presence of nickel on the surface of the copper foil for circuits is in a trade-off relationship between transmission characteristics and heat resistance.

[0006] Known examples of techniques aimed at improving both of the above characteristics include the techniques of Patent Documents 1 and 2. Patent Document 1 proposes controlling the total amount of Co, Ni, and Mo deposited in the surface treatment layer of copper foil to a predetermined amount or less and forming particles of a predetermined shape in the surface treatment layer in order to suppress the influence of ferromagnetic metals on transmission characteristics. Patent Document 2 also proposes a surface-treated copper foil in which the magnetism is controlled to a predetermined condition (demagnetized) by controlling the manufacturing process of the base foil (copper foil substrate) of the surface-treated copper foil. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 7055049 [Patent Document 2] Patent No. 7174869 Summary of the Invention [Problem to be solved by the invention]

[0008] However, both Patent Documents 1 and 2 only consider the magnetism of the surface-treated copper foil that has no thermal history after production, and do not take into account the effects of thermal pressure bonding with a resin substrate or thermal load during solder reflow in the manufacturing process of a printed wiring board.

[0009] In response to this, the present inventors have conducted extensive research and found that even if a surface-treated copper foil having a surface treatment film containing a nickel-containing surface treatment layer (hereinafter simply referred to as a "nickel layer (Ni layer)") is demagnetized without any thermal history after production, when the surface-treated copper foil as a circuit conductor is subjected to a heat treatment in the process of producing the above-mentioned printed wiring board, the nickel layer in the surface treatment film of the surface-treated copper foil may subsequently develop magnetism (become magnetized). As described above, if the nickel layer in the surface treatment film of the surface-treated copper foil serving as a circuit conductor is magnetized due to the heat treatment that is performed during the manufacturing process of the printed wiring board, this will cause a problem of deterioration in transmission characteristics. Therefore, there is a demand for a surface-treated copper foil that can suppress magnetization of the nickel layer even after a predetermined heat treatment and can exhibit excellent transmission characteristics and heat resistance.

[0010] Therefore, an object of the present invention is to provide a surface-treated copper foil, a copper-clad laminate, and a printed wiring board that can suppress magnetization of the nickel layer even after a predetermined heat treatment and exhibit excellent transmission characteristics and heat resistance. [Means for solving the problem]

[0011] That is, the gist of the present invention is as follows. [1] A surface-treated copper foil having a surface treatment film including a nickel-containing surface treatment layer on at least one surface of a copper foil substrate, Saturation magnetic flux density (Bs) after heat treatment at 300°C for 2 hours 300 ) is 5.0 × 10 -3 Surface-treated copper foil with a resistance of T or less. [2] Residual magnetic flux density (Br 300 ) is 5.0 × 10 -4 The surface-treated copper foil according to the above [1], wherein the surface roughness is T or less. [3] The surface-treated copper foil according to [1] or [2] above, which satisfies the following requirements (I) and (II): Requirement (I): The rate of increase in saturation magnetic flux density Bs after heat treatment at 300°C for 2 hours [{(Bs 300 -Bs0) / Bs0}×100] is 300% or less. Requirement (II): The increase rate of residual magnetic flux density Br after heat treatment at 300°C for 2 hours [{(Br 300 -Br0) / Br0}×100] is 300% or less. In the above requirements (I) and (II), Bs 300 is the saturation magnetic flux density after heat treatment at 300°C for 2 hours, Bs0 is the saturation magnetic flux density before the heat treatment, Br 300 is the residual magnetic flux density after heat treatment at 300° C. for 2 hours, and Br0 is the residual magnetic flux density before the heat treatment. [4] On the surface having the surface treatment film, the nickel adhesion amount is 0.02 mg / dm 2 or more and 3.0 mg / dm 2 or less. The surface-treated copper foil according to any one of the above [1] to [3]. [5] The surface treatment film includes, in order from the copper foil substrate side, a roughening treatment layer and a surface treatment layer containing the nickel, and on the surface of the surface treatment film, the arithmetic mean height Sa measured optically in accordance with ISO25178 is 0.02 μm or more and 0.35 μm or less. The surface-treated copper foil according to any one of the above [1] to [4]. [6] The surface treatment layer containing the nickel is composed of a nickel alloy containing at least one element selected from the group consisting of zinc, phosphorus, molybdenum, tungsten, chromium, iron, cobalt, and niobium. The surface-treated copper foil according to any one of the above [1] to [5]. [7] A copper-clad laminate including the surface-treated copper foil according to any one of the above [1] to [6]. [8] A printed wiring board including the copper-clad laminate according to [7] above. [Advantages of the Invention]

[0012] According to the present invention, even after a predetermined heat treatment, it is possible to suppress magnetization of the nickel layer, and it is possible to provide a surface-treated copper foil, a copper-clad laminate, and a printed wiring board that can exhibit excellent transmission characteristics and heat resistance. [Embodiments for Carrying Out the Invention]

[0013] Embodiments of the surface-treated copper foil, copper-clad laminate, and printed wiring board according to the present invention will be described in detail below. In this specification, the term "A to B" regarding the description of numerical values means "A or more and B or less" (when A < B) or "A or less and B or more" (when A > B). Also, in the present invention, a combination of preferred embodiments is a more preferred embodiment.

[0014] [Surface-Treated Copper Foil] The surface-treated copper foil of the present invention has a surface treatment film including a nickel-containing surface treatment layer on at least one surface of a copper foil substrate, and has a saturation magnetic flux density (Bs 300 ) is 5.0 × 10 -3 It is below T.

[0015] The surface-treated copper foil of the present invention has the above-described structure, and therefore can suppress magnetization of the nickel layer even after a predetermined heat treatment, and can exhibit excellent transmission characteristics and heat resistance. The detailed reason why such an effect is obtained is not clear, but one possible reason is as follows.

[0016] First, in order to solve the above problems, the present inventors focused on suppressing magnetization in the nickel layer after heat treatment and conducted extensive research. As a result of research, the inventors have found that in surface-treated copper foils having a conventional surface treatment film containing a nickel layer, (1) the magnetic flux density increases when subjected to a specified heat treatment, and (2) in copper foil types in which the increase is large, the transmission loss in the high frequency band increases significantly. The reason why the magnetic flux density increases in the surface-treated copper foil after a predetermined heat treatment is not clear, but one reason is thought to be that the heat treatment causes crystallization and / or an increase in the crystal grain size in the nickel layer, which magnetizes the nickel layer after the heat treatment.

[0017] Therefore, the inventors of the present invention have conducted further research and have found that by improving the nickel layer, it is possible to suppress the nickel layer from being magnetized by heat treatment, and that the saturation magnetic flux density (Bs 300 ) is 5.0 × 10 -3 It has been found that a surface-treated copper foil having a transmission loss of 1000 kJ / cm2 or less can be obtained, and that such a surface-treated copper foil can reduce transmission loss and further exhibit excellent heat resistance. Here, the relationship between saturation magnetic flux density and transmission loss is not entirely clear, but it is thought that the higher the frequency band, the greater the influence of the surface condition of the circuit conductor, and that when ferromagnetic metal adheres to the circuit conductor, the transmission loss of high-frequency signals increases due to losses caused by the generation of eddy currents (losses caused by an increase in the electrical resistance of the circuit conductor due to the generation of eddy currents) and magnetic hysteresis losses. Therefore, in the present invention, by controlling the saturation magnetic flux density of the nickel layer to a predetermined value or less, the magnetism of the circuit conductor can be made to a level that does not affect transmission loss in the high frequency band, which is thought to significantly reduce transmission loss. Furthermore, it is believed that the surface-treated copper foil of the present invention can also exhibit excellent heat resistance by including a nickel layer as a surface treatment film. The surface-treated copper foil of the present invention is suitable for use in, for example, printed wiring boards. When the surface-treated copper foil of the present invention is used, both reduced transmission loss and excellent heat resistance can be achieved.

[0018] The surface-treated copper foil of the present invention will be described in detail below.

[0019] The surface-treated copper foil of the present invention has a surface treatment film including a nickel-containing surface treatment layer on at least one surface of a copper foil substrate.

[0020] <Copper foil base> The copper foil substrate serves as the base layer of the surface-treated copper foil. The copper foil substrate may be an electrolytic copper foil or a rolled copper foil, and is preferably an electrolytic copper foil. The thickness of the copper foil substrate is, for example, 5 to 210 μm, preferably 5 to 100 μm, and more preferably 5 to 40 μm. Furthermore, when the copper foil substrate is an electrolytic copper foil, the surface having the surface treatment film may be the surface of the electrolytic copper foil that originates from the peeled surface from a rotating drum-shaped cathode (hereinafter simply referred to as a "drum-shaped cathode") (hereinafter referred to as the "drum side"), or the surface opposite to the drum side (hereinafter referred to as the "non-drum side"), but is preferably the non-drum side. In general, the drum side is sometimes called the shiny side (S side), and the non-drum side is sometimes called the deposit side or matte side (M side).

[0021] <Surface treatment film> The surface treatment film is a layer formed on at least one surface of the copper foil substrate, and serves to impart desired functions to the surface-treated copper foil. The surface treatment film may be formed on either the front or back surface of the copper foil substrate, or on both surfaces. The surface treatment film also includes a nickel layer. Specifically, the surface treatment film may be composed of only a nickel layer, or may include one or more other surface treatment layers. Examples of other surface treatment layers include a roughening treatment layer formed on a copper foil substrate, intermediate layers such as a surface treatment layer containing zinc (Zn) (hereinafter sometimes referred to as a "zinc layer (Zn layer)") and a surface treatment layer containing chromium (Cr) (hereinafter sometimes referred to as a "chromium layer (Cr layer)") formed on a nickel layer, and chemical adhesion layers formed using a silane coupling agent or the like.

[0022] The surface of the surface treatment film is at least one of the front and back surfaces of the surface-treated copper foil, and is the surface of the copper foil substrate having the surface treatment film containing a nickel layer. The surface of such a surface treatment film may be the surface of a nickel layer formed on a copper foil substrate, or the surface of another surface treatment layer (e.g., a chemical adhesion layer formed by a silane coupling agent) formed directly or indirectly on the nickel layer. Furthermore, when the surface-treated copper foil of the present invention is used for the conductor circuit of a printed wiring board, the surface of the surface treatment film, preferably the surface of the surface treatment film further including a roughening treatment layer, becomes the surface (adhesion surface) for adhering and laminating a resin substrate.

[0023] (Surface treatment layer containing nickel) The surface treatment film includes a nickel-containing surface treatment layer (nickel layer), which serves as a base layer for the surface-treated copper foil.

[0024] The nickel layer may be any layer containing nickel, and may be a single layer or a multi-layer consisting of two or more layers of different compositions, but is preferably a single layer from the viewpoint of ease of production.

[0025] The nickel layer may be composed of nickel alone or an alloy of nickel and other elements (hereinafter also referred to as "nickel alloy"), but from the viewpoint of being able to reduce transmission loss while exhibiting excellent heat resistance, it is preferable that the nickel layer be composed of a nickel alloy. The nickel alloy is preferably a nickel alloy containing one or more elements selected from the group consisting of zinc (Zn), phosphorus (P), molybdenum (Mo), tungsten (W), chromium (Cr), iron (Fe), cobalt (Co) and niobium (Nb), and more preferably a nickel alloy containing one or more elements selected from the group consisting of Zn, P, Mo, W, Cr and Co. More specifically, the nickel alloy is preferably one or more selected from the group consisting of Ni-P, Ni-Zn, Ni-Mo, Ni-W, Ni-Cr, Ni-Co, Ni-Zn-P, Ni-Zn-Mo, and Ni-Zn-Cr. The metal or alloy composition constituting the nickel layer can be confirmed by the method described in the examples.

[0026] On the surface having the surface treatment film, the nickel coating amount is preferably 0.02 mg / dm 2 More than 3.5mg / dm 2 Less than or equal to 0.02 mg / dm 2 ≥3.0 mg / dm 2 or less, more preferably 0.02 mg / dm 2 ≥2.0 mg / dm 2 or less, even more preferably 0.02 mg / dm2 More than 1.0 mg / dm 2 By setting the thickness within the above range, it is possible to reduce transmission loss and exhibit excellent heat resistance. The amount of nickel deposited on the surface having the surface treatment film can be measured by the method described in the examples.

[0027] (Other surface treatment layers) The surface treatment film may further include other surface treatment layers in addition to the nickel layer, as required. Other surface treatment layers include, for example, a roughening treatment layer formed on a copper foil substrate, an intermediate layer such as a Zn layer and a Cr layer formed on a Ni layer, and a chemical adhesion layer formed by a silane coupling agent.

[0028] <Magnetic properties of surface-treated copper foil> The surface-treated copper foil of the present invention has a saturation magnetic flux density (Bs 300 ) is 5.0×10 -3 T or less, preferably 2.0 × 10 -3 T or less, preferably 7.0×10 -4 T or less. By setting the magnetic flux density within the above range, it is possible to reduce the occurrence of magnetism due to heating, reduce transmission loss, and furthermore, to exhibit excellent heat resistance. 300 ) is preferably 1.0 × 10 -6 T or more, preferably 5.0 × 10 -6 T or more, more preferably 2.0 × 10 -5 T or greater.

[0029] The surface-treated copper foil of the present invention has a residual magnetic flux density (Br 300 ), but preferably 6.0 × 10 -4 T or less, preferably 5.0 × 10 -4 T or less, more preferably 4.0 × 10 -4T or less. By keeping it within the above range, it is possible to effectively reduce the development of magnetism due to heat treatment, and to further reduce transmission loss. In particular, it is thought that the higher the residual magnetic flux density, the greater the loss due to the generation of eddy currents and the magnetic hysteresis loss, resulting in a larger transmission loss of high frequency signals. Therefore, it is thought that by reducing the above-mentioned predetermined residual magnetic flux density, it is possible to further reduce transmission loss significantly. Note that the residual magnetic flux density (Br 300 ) is preferably 1.0 × 10 -7 T or more, preferably 5.0 × 10 -7 T or more, more preferably 3.0 × 10 -6 T or greater.

[0030] The surface-treated copper foil of the present invention preferably satisfies the following requirements (I) and (II). Requirement (I): The rate of increase in saturation magnetic flux density Bs after heat treatment at 300°C for 2 hours [{(Bs 300 −Bs0) / Bs0}×100] is preferably 310% or less, more preferably 300% or less, even more preferably 200% or less, and still more preferably 100% or less. Requirement (II): The increase rate of residual magnetic flux density Br after heat treatment at 300°C for 2 hours [{(Br 300 -Br0) / Br0}×100] is preferably 310% or less, more preferably 300% or less, even more preferably 200% or less, and still more preferably 100% or less. In the above requirements (I) and (II), Bs 300 is the saturation magnetic flux density after heat treatment at 300°C for 2 hours, Bs0 is the saturation magnetic flux density before the heat treatment, Br 300 is the residual magnetic flux density after heat treatment at 300° C. for 2 hours, and Br0 is the residual magnetic flux density before the heat treatment. By satisfying the above requirements, the surface-treated copper foil of the present invention can keep the increase in each magnetic flux density after heat treatment within a predetermined range, thereby further reducing transmission loss. In particular, surface-treated copper foils with a large increase in magnetic flux density after heat treatment tend to produce unstable waveforms of high-frequency signals when measuring transmission loss. It is believed that this phenomenon occurs because, when the thermal load during the manufacturing process of a printed wiring board is distributed in the plane, changes in the magnetization distribution occur within the plane of the printed wiring board. Therefore, it is believed that the quality of high-frequency signals can be improved by controlling the increase in magnetic flux density after heat treatment within a certain range.

[0031] The saturation magnetic flux density Bs and the residual magnetic flux density Br before and after the above-mentioned predetermined heat treatment can be measured by the following method. First, the surface-treated copper foil after a predetermined heat treatment is obtained by heating the surface-treated copper foil at 300°C for 2 hours. The surface-treated copper foil before and after the heat treatment was cut into a size of 10 mm x 10 mm to be used as the measurement object, and the saturation magnetic flux density Bs and the residual magnetic flux density Br were measured using a vibrating sample magnetometer (VSM) under the following conditions. Applied magnetic field range: ±10000[Oe] Sweep speed: 50[Oe / s] More specifically, the magnetic properties can be measured by the method described in the Examples.

[0032] <Surface roughness of surface-treated copper foil> In the surface-treated copper foil of the present invention, when the surface treatment film includes, in order from the copper foil substrate side, a roughened layer and the nickel layer, the arithmetic mean height Sa of the surface of the surface treatment film, measured optically in accordance with ISO 25178, is preferably 0.02 μm to 0.50 μm, more preferably 0.02 μm to 0.35 μm, even more preferably 0.02 μm to 0.30 μm, and even more preferably 0.02 μm to 0.20 μm. This configuration can reduce transmission loss while exhibiting excellent heat resistance. In particular, in the surface-treated copper foil, the surface treatment film includes a roughened layer below the nickel layer (on the copper foil substrate side), thereby improving adhesion to the resin substrate. In this case, by having the surface irregularities of the surface treatment film within the above-mentioned predetermined range, adhesion to the resin substrate can be improved without adversely affecting transmission loss. The arithmetic mean height Sa can be measured by the method described in the Examples.

[0033] <Method of manufacturing surface-treated copper foil> Next, an example of a preferred method for producing the surface-treated copper foil of the present invention will be described. A preferred method for producing the surface-treated copper foil of the present invention includes a step of forming a surface treatment film containing a nickel layer on at least one surface of a copper foil substrate, more specifically, a step of forming a nickel layer directly or indirectly on at least one surface of the copper foil substrate.

[0034] (Copper foil base) As the copper foil substrate, it is preferable to use electrolytic copper foil or rolled copper foil, which has a smooth and glossy surface without large irregularities. Among them, electrolytic copper foil is preferable from the viewpoints of productivity and cost, and it is particularly preferable to use the non-drum side of the electrolytic copper foil as the side on which the surface treatment film is formed. In addition, it is preferable that the surface of the drum-shaped cathode used in the production of electrolytic copper foil is polished with a buff of #1000 to #2500.

[0035] The copper foil substrate has a ten-point average roughness Rzjis of preferably 2 μm or less, more preferably 1 μm or less, and even more preferably 0.8 μm or less, at least on the surface on which the surface treatment film is formed. By keeping the roughness within the above range, adhesion to the resin substrate can be improved and transmission loss does not increase. The copper foil substrate has a ten-point average roughness Rzjis on both sides of the substrate of preferably 2 μm or less, more preferably 1 μm or less, and even more preferably 0.8 μm or less. The lower limit of the ten-point average roughness Rzjis on each surface of the copper foil substrate is, for example, 0.1 μm or more from the viewpoint of ease of production or availability. The ten-point average roughness Rzjis can be measured using a contact surface roughness measuring instrument in accordance with the method specified in JIS B0601: 2001. Specifically, it can be measured by the method described in the examples.

[0036] The thickness of the copper foil substrate is, for example, 5 to 210 μm, preferably 5 to 100 μm, and more preferably 5 to 40 μm.

[0037] (nickel treatment) The surface-treated copper foil of the present invention is subjected to a nickel treatment to form a nickel layer directly or indirectly on at least one surface of the copper foil substrate. An object of the present invention is to provide a surface-treated copper foil that can suppress magnetization of the nickel layer even after a predetermined heat treatment. In response to this, the present inventors conducted extensive research and concluded that the increase in magnetic flux density in surface-treated copper foil after a specified heat treatment is due to the progress of crystallization of the nickel layer and / or an increase in crystal grain size caused by the heat treatment. Focusing on this phenomenon, the inventors investigated nickel treatments that can suppress this. The following nickel treatment (A) and nickel treatment (B) will be described in detail below as suitable examples of nickel treatments investigated by the present inventors.

[0038] Nickel treatment (A) The nickel treatment (A) is an example of a nickel treatment that can suppress an increase in the crystal grain size in the nickel layer after a predetermined heat treatment, and is performed by pulse electrolysis with flow rate control.

[0039] Generally, pulse electrolysis allows for instantaneous application of a higher current density than normal DC electrolysis, making it possible to form a plating film with a dense microcrystalline structure. On the other hand, because the instantaneous application of high electric current causes the loss of reactive species near the electrode, pulse electrolysis requires alternating periods of current application and rest, and in order to obtain a dense crystalline structure, the duty ratio (current application time / [current application time + current rest time]) must be reduced. However, if the duty ratio is reduced, the time when no current is applied will occupy a large portion of the process, raising concerns about a decline in productivity. Furthermore, because discontinuous multi-step plating is performed, impurities are more likely to be incorporated into the nickel layer, raising concerns about a decline in heat resistance, which poses challenges in terms of manufacturing.

[0040] Therefore, the inventors conducted extensive research and found that the above-mentioned problems could be solved by controlling the liquid flow rate in the tank to increase the stirring speed in the liquid and supply sufficient reactive species near the electrodes, which serve as the reaction field. In other words, by performing pulse electrolysis in a reaction field where the liquid flow rate is controlled, reactive species can be supplied immediately near the electrodes immediately after current application, making it possible to efficiently deposit nickel under conditions with a higher duty ratio than conventional methods. This also reduces the amount of impurities trapped between the nickel layers and enables electroplating of nickel layers with fine crystal grain sizes.

[0041] In such pulse electrolysis, the duty ratio is preferably 0.1 to 0.9, more preferably 0.1 to 0.8, and the solution flow rate is preferably 15 to 110 L / min, more preferably 20 to 100 L / min. By keeping the duty ratio and solution flow rate within the above ranges, it is possible to efficiently deposit microcrystalline nickel, resulting in a microcrystalline nickel layer. Therefore, even after a predetermined heat treatment, the crystal grain size does not fully increase, and it is thought that magnetization of the nickel layer can be suppressed. On the other hand, if the duty ratio is too small, productivity tends to deteriorate. If the duty ratio is too large, reactive species are not sufficiently supplied to the electrode surface, which tends to result in poor plating appearance on the electrode surface. Furthermore, if the flow rate is too small, reactive species are not sufficiently supplied to the electrode surface, and if the flow rate is too large, air bubbles are present in the solution, which tends to result in poor plating appearance on the electrode surface.

[0042] An example of the plating bath composition and electrolysis conditions suitable for the nickel treatment (A) is shown below. Note that the following conditions are a preferred example, and the type and amount of additives, electrolysis conditions, etc. can be appropriately changed and adjusted as needed within the range that does not impair the effects of the present invention. <Plating bath composition> Nickel sulfate hexahydrate: 10-80g / L in terms of nickel (atom) Boric acid: 5~40g / L pH: 3.0 to 5.0 <Conditions for pulse electrolysis> Bath temperature: 10~60℃ Current density: 1~15A / dm 2 Current application time: 5 to 100 milliseconds Duty ratio:0.1~0.9 Total charge: 0.5 to 30 A·S / dm 2 Liquid flow rate: 15~110L / min

[0043] Nickel treatment (B) The nickel treatment (B) is an example of a nickel treatment that can suppress an increase in the crystal grain size in the nickel layer after a predetermined heat treatment, and is carried out by an electrochemical reduction reaction of nickel hydroxide. Specifically, it is as follows.

[0044] First, a nickel layer is formed on the surface of a copper foil substrate. Then, nickel hydroxide is deposited on the surface of the copper foil substrate by methods such as alkaline immersion, anodic oxidation, or nickel plating under alkaline pH conditions (hereinafter referred to as "hydroxide treatment"). The nickel hydroxide is then reduced to nickel through an electrochemical reduction reaction (hereinafter referred to as "reduction treatment") to re-form the nickel layer. It is believed that performing the reduction treatment under appropriate conditions can form a mixture of nickel hydroxide and metallic nickel in the nickel layer, resulting in random crystallinity and making the nickel layer amorphous. Furthermore, the presence of some oxygen atoms incorporated into the hydroxide at grain boundaries is believed to have the effect of suppressing the growth of crystal grain size during heating.

[0045] In such an electrochemical reduction reaction of nickel hydroxide, the current density is preferably 0.1 to 2.7 A / dm 2 , more preferably 0.2 to 2.5 A / dm 2 It is believed that the above-mentioned effects can be obtained by keeping the current density within the above range. On the other hand, if the current density is too low, the reduction of nickel hydroxide tends to be insufficient, and if the current density is too high, the crystal grain size tends to increase, and magnetism tends to be exhibited.

[0046] Examples of electrolytic plating conditions, hydroxide treatment conditions, and reduction treatment conditions suitable for the nickel treatment (B) are shown below. Note that the following conditions are preferred examples, and the type and amount of additives, electrolysis conditions, etc. can be appropriately changed and adjusted as needed within the range that does not impair the effects of the present invention. (1) First, it is preferable to perform electroplating under the following conditions: <Plating solution composition> Nickel sulfate hexahydrate: 20-60g / L in terms of nickel (atom) Boric acid: 5~40g / L pH: 3.0 to 5.0 <Electrolysis conditions> Bath temperature: 20~60℃ Current density: 0.1~2.7A / dm 2 Current application time: 1.5 to 30 seconds

[0047] (2) Next, it is preferable to sequentially perform a hydroxide treatment and a reduction treatment on the surface of the nickel layer obtained in (1) above under the following conditions. <Conditions for hydroxide treatment> Sodium hydroxide solution: sodium hydroxide concentration 5-50g / L Immersion time: 10 to 60 seconds <Conditions for reduction treatment> Current density: 0.1~2.7A / dm 2 Current application time: 10 to 60 seconds

[0048] In addition, by alloying the nickel layer with different metals such as Zn, P, Mo, W, Cr, Fe, Co, and Nb, it is possible to further suppress the increase in magnetization and improve heat resistance. The reaction mechanism for suppressing the magnetism of nickel as described above has a similar effect in plating baths containing different metals. For example, in nickel treatment (A), adding elements such as a Zn source or a P source to the nickel plating bath used in pulse electrolysis can form a finely crystallized nickel layer.

[0049] In this embodiment, it is considered that the increase in magnetic flux density in the surface-treated copper foil after the specified heat treatment is due to the progress of crystallization of the nickel layer and / or an increase in the crystal grain size caused by the heat treatment, and the nickel treatments (A) and (B) are preferably exemplified as a means for improving this. However, the increase in magnetic flux density in the surface-treated copper foil after the specified heat treatment may be suppressed by means other than those described above.

[0050] (roughening treatment) The surface of the surface-treated copper foil of the present invention may be roughened to form a roughened layer on the surface of the copper foil substrate before the nickel treatment, for example, by electrolytic deposition of copper particles or etching with hydrogen peroxide or the like.

[0051] Furthermore, when a roughened layer is formed, it is desirable to control the treatment conditions so that the arithmetic mean height Sa of the surface of the surface treatment film including the roughened layer and the nickel layer, measured optically in accordance with ISO 25178, is preferably 0.02 μm to 0.50 μm, more preferably 0.02 μm to 0.35 μm, even more preferably 0.02 μm to 0.30 μm, and still more preferably 0.02 μm to 0.20 μm. By controlling the surface condition of the obtained surface-treated copper foil as described above, it is possible to further improve adhesion to the surface of the resin substrate while reducing transmission loss. The treatment conditions can be controlled, for example, by adjusting the duration or amount of current flow in the case of forming roughening particles by copper electrodeposition, or by adjusting the treatment time in the case of forming roughening particles by etching.

[0052] As a roughening treatment, it is preferable to subject the copper foil substrate surface before nickel treatment to the roughening plating treatment (1) described below. If necessary, a fixed plating treatment (2) may be combined. Roughening plating treatment (1) <Plating bath composition> Copper sulfate pentahydrate: 3~20g / L in terms of copper (atoms) Sulfuric acid: 100~250g / L Ammonium molybdate: 400-1200 mg / L in molybdenum (atom) equivalent <Electroplating processing conditions> Bath temperature: 5~20℃ Current density: 5~55A / dm 2 Current application time: 0.5 to 15 seconds Fixed plating process (2) <Plating bath composition> Copper sulfate pentahydrate: 40~70g / L in terms of copper (atoms) Sulfuric acid: 100~250g / L <Electroplating processing conditions> Bath temperature: 15~30℃ Current density: 2~10A / dm 2 Current application time: 0.5 to 5 seconds

[0053] (Other processing) Furthermore, the surface-treated copper foil of the present invention may further have a chemical adhesion layer such as a silane coupling agent layer formed on the nickel layer, either directly or via an intermediate layer such as a heat-resistant layer containing zinc (Zn) or a rust-proofing layer containing chromium (Cr). Note that the intermediate layer and the chemical adhesion layer are very thin, so they do not affect the roughness of the surface treatment surface and have little effect on the magnetism.

[0054] The heat-resistant layer is preferably formed when it is necessary to further improve the heat resistance of the surface treatment film. The heat-resistant layer is preferably formed of, for example, zinc or an alloy containing zinc. Examples of alloys containing zinc include zinc-tin (Sn) alloy, zinc-cobalt (Co) alloy, zinc-copper (Cu) alloy, zinc-molybdenum (Mo) alloy, zinc-chromium (Cr) alloy, and zinc-vanadium (V) alloy.

[0055] The rust prevention layer is preferably formed when it is necessary to further improve the corrosion resistance of the surface treatment film. Examples of the rust prevention layer include a chrome layer formed by chrome plating and a chromate layer formed by chromate treatment.

[0056] When both the heat-resistant treatment layer and the rust-proofing treatment layer are formed, it is preferable to form them on the surface treatment layer in this order. That is, when all of them are provided, the order is copper foil substrate-roughened treatment layer-nickel layer-heat-resistant treatment layer-rust-proofing treatment layer. Furthermore, depending on the application and the desired properties, only one or two of the heat-resistant treatment layer and the rust-proofing treatment layer may be formed.

[0057] The chemical adhesion layer can be formed, for example, by applying a silane coupling agent solution directly or via an intermediate layer to the surface of the nickel layer of the surface-treated copper foil, followed by air drying (natural drying) or heat drying. The silane coupling agent layer is formed when the water in the applied coupling agent solution evaporates. In particular, from the viewpoint of further promoting the dehydration reaction of the silane coupling agent, it is preferable to dry by heating at 100 to 220°C.

[0058] Furthermore, the silane coupling agent layer preferably contains one or more agents selected from the group consisting of epoxy-based silane coupling agents, amino-based silane coupling agents, vinyl-based silane coupling agents, methacrylic-based silane coupling agents, acrylic-based silane coupling agents, azole-based silane coupling agents, styryl-based silane coupling agents, ureido-based silane coupling agents, mercapto-based silane coupling agents, sulfide-based silane coupling agents, and isocyanate-based silane coupling agents.

[0059] [Application] The surface-treated copper foil of the present invention is suitable for use in the manufacture of copper-clad laminates and further in the manufacture of printed wiring boards. That is, the copper-clad laminate of the present invention comprises the surface-treated copper foil of the present invention, and preferably further comprises a resin substrate laminated onto the surface treatment layer of the surface-treated copper foil. Furthermore, the printed wiring board of the present invention comprises the copper-clad laminate of the present invention. When such surface-treated copper foil is used to produce a copper-clad laminate or a printed wiring board, the nickel layer can be prevented from being magnetized even after a predetermined heat treatment. Therefore, the resulting copper-clad laminate or printed wiring board can reduce transmission loss and also exhibit good heat resistance due to the nickel layer.

[0060] Incidentally, in next-generation wireless transmission applications, the fact that the circuit board has magnetism can itself become a major problem. For example, telemedicine is one of the technologies expected to be used in the next generation of 5G and 6G. However, when considering the use of printed circuit boards in magnetically-based testing equipment such as MRI, there is a possibility that problems may arise, such as inaccurate test results, due to the printed circuit board itself being magnetized. Other technologies include wearable devices such as smartwatches, but as these devices become more sophisticated, there is a possibility that they may also encounter problems such as malfunction due to magnetic defects. As the frequency of high-frequency signals increases in the future, it is expected that the impact of magnetic metals on magnetic fields will become greater. Therefore, in addition to reducing transmission loss, there is a demand for the use of non-magnetic surface-treated copper foil as a circuit conductor for printed wiring boards. From this viewpoint, the surface-treated copper foil of the present invention is extremely useful.

[0061] That is, the printed wiring board having the surface-treated copper foil of the present invention is suitable as a printed wiring board for use in a high frequency band (particularly a high frequency band of 1 to 100 GHz) and as a printed wiring board where the influence of a magnetic field is a concern.

[0062] A copper-clad laminate comprising the surface-treated copper foil of the present invention can be formed by a known method. Specifically, a copper-clad laminate is generally produced by laminating and adhering a surface-treated copper foil and a resin substrate (insulating substrate) so that the roughened surface (adhesion surface) of the surface-treated copper foil faces the resin substrate. In particular, when producing a copper-clad laminate using the surface-treated copper foil of the present invention, it is preferable to use the surface having a predetermined surface treatment film as the adhesive surface for the resin substrate. This reduces transmission loss and also provides good heat resistance due to the nickel layer.

[0063] The resin substrate may be, for example, a flexible resin substrate or a rigid resin substrate, and the surface-treated copper foil of the present invention is particularly suitable for use in combination with a rigid resin substrate, which requires high transmission characteristics and adhesion in the high frequency band. Examples of resins that can form the resin substrate include epoxy resins, polyphenylene ethers, phenolic resins, bis(phenoxyphenoxy)benzene, polyimides, liquid crystal polymers, and fluororesins (such as polytetrafluoroethylene).

[0064] In addition, when producing a copper clad laminate for printed wiring boards, it may be produced by laminating a surface-treated copper foil having a silane coupling agent layer and a resin substrate by hot pressing. Note that a copper clad laminate for printed wiring boards produced by applying a silane coupling agent to a resin substrate, and laminating the resin substrate coated with the silane coupling agent and a surface-treated copper foil having a rust prevention treatment layer on the outermost surface by hot pressing also has the same effect as when using the surface-treated copper foil having the above-mentioned silane coupling agent layer.

[0065] Furthermore, a printed wiring board including the surface-treated copper foil of the present invention can be formed by a known method. Specifically, it may be formed using the above-mentioned copper-clad laminate for printed wiring boards. Such a printed wiring board preferably includes the above-mentioned copper-clad laminate for printed wiring boards.

[0066] The printed wiring board according to this embodiment can be obtained by, for example, etching the surface-treated copper foil of a copper-clad laminate to form a circuit, and then laminating another resin substrate to cover the circuit. The resin substrate to be laminated to cover the circuit may be of the same type as or a different type from the resin substrate of the copper-clad laminate.

[0067] The surface-treated copper foil of the present invention can also be suitably used as a negative electrode current collector for lithium ion secondary batteries and the like. The negative electrode current collector including the surface-treated copper foil of the present invention can be formed by a known method, specifically by coating the surface of the copper foil with carbon particles or the like as a negative electrode active material layer, drying the coated copper foil, and then pressing the coated copper foil.

[0068] Although the embodiments of the present invention have been described above, the above embodiments are merely examples of the present invention. The present invention includes all aspects encompassed by the concept of the present invention and the scope of the claims, and various modifications can be made within the scope of the present invention. [Example]

[0069] The present invention will be described in more detail below based on examples, which are merely examples of the present invention.

[0070] (Manufacturing Example 1: Preparation of copper foil substrate) A roll of electrolytic copper foil (double-sided glossy foil) having a ten-point average roughness Rzjis of 0.8 μm on the M side and a thickness of 18 μm was produced using the following cathode and anode as a copper foil substrate serving as a base material for forming a surface treatment film, and a copper sulfate electrolyte of the following composition under the following electrolysis conditions. The ten-point average roughness Rzjis on the M side is a value measured under the following measurement conditions.

[0071] <Cathode and Anode> Cathode: Titanium rotating drum with surface roughness adjusted by buffing with #1000 to #2000 grit Anode: Dimensionally Stable Anode DSA® <Electrolyte composition> Copper sulfate pentahydrate: 75g / L in terms of copper (atoms) Sulfuric acid: 65g / L Chlorine concentration: 20mg / L (additives) Sodium 3-mercapto-1-propanesulfonate: 2mg / L Hydroxyethylcellulose: 10mg / L ·Low molecular weight glue (molecular weight 3000): 50mg / L <Electrolysis conditions> Liquid temperature: 55℃ Current density: 45A / dm 2

[0072] <Ten-point average roughness Rzjis> On the M side of the electrodeposited copper foil, a contact surface roughness measuring instrument (manufactured by Kosaka Laboratory Co., Ltd., "Surfcorder SE1700") was used to measure the ten-point average roughness Rzjis (μm) defined in JIS B 0601:2001 in the direction perpendicular to the longitudinal direction (machine direction, MD) of the electrodeposited copper foil (TD direction), i.e., the ten-point average roughness Rzjis (μm) of the TD.

[0073] (Examples 1 to 10 and 48 to 51 and Comparative Examples 4 and 5) In Examples 1 to 10 and 48 to 51 and Comparative Examples 4 and 5, the electrolytic copper foil produced in Production Example 1 was used as the copper foil substrate, and the copper foil substrate was subjected to the following steps [1] to [3] to obtain surface-treated copper foils, which will be explained in detail below.

[0074] [1] Formation of nickel layer A nickel layer was formed on the M side of the electrodeposited copper foil by electroplating (nickel treatment (A)) using a pulse electrolysis device. A bath capable of circulating the plating solution was used, and plating was performed while controlling the flow rate. The plating bath composition and pulse electrolysis conditions were as follows: <Plating bath composition> Nickel sulfate hexahydrate: 50g / L in terms of nickel (atom) Boric acid: 20g / L pH: 4.3 <Conditions for pulse electrolysis> Bath temperature: 20℃ Current density: 10A / dm 2 Current application time: 10 milliseconds Duty ratio: Shown in Tables 1 and 2. Total charge: 4A·S / dm 2 Liquid flow rate: shown in Tables 1 and 2.

[0075] [2] Formation of the intermediate layer Subsequently, the surface of the nickel layer formed in [1] above was subjected to zinc plating and chromium plating in this order under the following conditions to form an intermediate layer. The compositions of the plating baths and the electrolysis conditions for the zinc plating and chromium plating were as follows:

[0076] Zinc plating treatment <Plating bath composition> Zinc sulfate heptahydrate: 2.5g / L in terms of zinc (atom) Sodium hydroxide): 25g / L pH: 10-12 <Electrolysis conditions> Bath temperature: 20℃ Current density: 0.7A / dm 2 Processing time: 4 seconds

[0077] Chrome plating <Plating bath composition> Chromium (VI) oxide: 8 g / L in terms of chromium (atom) pH: 2.4 <Electrolysis conditions> Bath temperature: 30℃ Current density: 5A / dm 2 Processing time: 4 seconds

[0078] [3] Formation of a chemical adhesion layer Finally, a 0.8% by mass aqueous solution of 3-aminopropyltrimethoxysilane was applied onto the intermediate layer (particularly the outermost chrome plating layer) formed in [2] above, and dried at 200°C to form a chemical adhesion layer using a silane coupling agent.

[0079] (Examples 11 to 17 and Comparative Example 6) In Examples 11 to 17 and Comparative Example 6, surface-treated copper foils were obtained in the same manner as in Example 1, except that in the above [1], instead of the nickel treatment (A), an electrochemical reduction reaction of nickel hydroxide (nickel treatment (B)) was carried out under the conditions shown below. Specifically, the following procedure was performed.

[0080] (1) First, a nickel layer was formed on the M side of the above-mentioned electrolytic copper foil by the following electrolytic plating. The plating bath composition and electrolysis conditions were as follows. <Plating bath composition> Nickel sulfate hexahydrate: 40g / L in terms of nickel (atom) Boric acid: 20g / L pH: 4.2 <Electrolysis conditions> Bath temperature: 30℃ Current density: 0.5A / dm 2 Power-on time: 5 seconds

[0081] (2) Next, the surface of the nickel layer obtained in (1) above was immersed in an aqueous sodium hydroxide solution (sodium hydroxide concentration: 30 g / L) for 30 seconds to perform hydroxide treatment on the nickel layer. Thereafter, an electrochemical reduction reaction of nickel hydroxide was carried out in an aqueous sodium hydroxide solution under the following conditions to obtain a nickel layer. <Conditions for reduction treatment> Current density: shown in Tables 1 and 2. Current application time: 30 seconds

[0082] (Examples 18 to 35) In Examples 18 to 35, surface-treated copper foils were obtained in the same manner as in Example 3, except that each component was added to the plating bath in [1] above at the concentrations shown below so that the composition of the Ni-containing surface treatment layer would be the alloy composition shown in Table 1. In the case of Ni-P Sodium hypophosphite monohydrate: 15g / L in phosphorus (atom) equivalent In the case of Ni-Zn Zinc sulfate heptahydrate: 5g / L in terms of zinc (atom) For Ni-Mo Sodium molybdate dihydrate: 5g / L in molybdenum (atom) equivalent For Ni-W Sodium tungstate dihydrate: 5g / L in terms of tungsten (atom) In the case of Ni-Cr Chromium (VI) oxide: 4 g / L in terms of chromium (atom) In the case of Ni-Co Cobalt chloride hexahydrate: 4g / L in terms of cobalt (atom) In the case of Ni-Zn-P Zinc sulfate heptahydrate: 5g / L in terms of zinc (atom) Sodium hypophosphite monohydrate: 15g / L in phosphorus (atom) equivalent In the case of Ni-Zn-Mo Zinc sulfate heptahydrate: 5g / L in terms of zinc (atom) Sodium molybdate dihydrate: 5g / L in molybdenum (atom) equivalent In the case of Ni-Zn-Cr Zinc sulfate heptahydrate: 5g / L in terms of zinc (atom) Chromium (VI) oxide: 4 g / L in terms of chromium (atom)

[0083] Examples 36 to 40 In Examples 36 to 40, surface-treated copper foils were obtained in the same manner as in Example 3, except that a roughened layer was first formed on a copper foil substrate under the following conditions, and then a surface-treated layer containing Ni was formed on the roughened layer.

[0084] [Formation of roughened layer] Before the nickel treatment in [1] above, a roughened layer was formed on the M side of the electrodeposited copper foil by a roughening plating treatment. By varying the current application time, roughening particles of different shapes were formed on the surface of the copper foil substrate. The plating bath composition and plating conditions were as follows: <Plating bath composition> Copper sulfate pentahydrate: 10g / L in terms of copper (atoms) Sulfuric acid: 150g / L Ammonium molybdate: 600 mg / L of molybdenum (atom) <Electroplating processing conditions> Bath temperature: 12℃ Current density: 20A / dm 2 Current application time: 2 to 8 seconds

[0085] (Examples 41 to 47) In Examples 41 to 47, the total charge of Ni plating was set to 1 to 20 A·S / dm 2 A surface-treated copper foil was obtained in the same manner as in Example 3, except that the temperature was changed within the range of .

[0086] (Comparative Examples 1 to 3) In Comparative Examples 1 to 3, surface-treated copper foils were obtained in the same manner as in Example 1, except that in the above [1], nickel treatment (A) was replaced by nickel treatment under the following conditions as a general nickel plating method. The plating bath composition and electrolysis conditions were as follows. <Plating bath composition> Nickel sulfate hexahydrate: 45g / L in terms of nickel (atom) Boric acid: 20g / L pH: 3.5 <Electrolysis conditions> Bath temperature: 20℃ Current density: 0.5A / dm 2 Power-on time: 9 seconds

[0087] (Comparative Example 7) In Comparative Example 7, a surface-treated copper foil was obtained in the same manner as in Example 1, except that Ni plating was not performed.

[0088] (Comparative Example 8) In Comparative Example 8, a surface-treated copper foil was obtained in the same manner as in Example 1, except that a surface treatment layer containing Ni was formed under the same Ni-Co treatment conditions as in Example 4 of Patent Document 1.

[0089] (Comparative Example 9) In Comparative Example 9, a surface-treated copper foil was obtained in the same manner as in Example 1 of Patent Document 2.

[0090] (evaluation) The surface-treated copper foils according to the above examples and comparative examples were used to evaluate the following characteristics. The evaluation conditions for each characteristic were as follows, and unless otherwise specified, each measurement was carried out at room temperature (20°C ± 5°C). The results are shown in Tables 1 and 2.

[0091] [Composition of surface treatment layer containing Ni] The composition of the nickel layer of the surface-treated copper foil was analyzed by X-ray photoelectron spectroscopy (XPS) using an X-ray photoelectron spectrometer (manufactured by ULVAC-PHI, Inc., "PHI Quants"). The incident X-rays used were monochromated Al-Kα rays (hν=1486.6 eV) with an escape angle of 45°. The surface of the surface treatment film including the nickel layer of the surface-treated copper foil was measured in an analysis area of ​​100 μmφ, and depth direction analysis was performed by Ar sputtering. When one or more elements selected from the group consisting of Zn, P, Mo, W, Cr, and Co were detected in the same depth region as the depth region where nickel was detected, it was determined that nickel was alloyed, and the alloy composition was estimated to be an alloy of nickel and the detected elements.

[0092] [Ni deposition amount] The surface of the surface-treated copper foil having a surface treatment film containing a nickel layer was analyzed by fluorescent X-ray analysis using a scanning X-ray fluorescence analyzer (Rigaku Corporation, ZSX Primus IV) to determine the Ni coating amount (mg / dm 2 The amount of Ni attached was determined using a calibration curve obtained using a known standard sample.

[0093] [Magnetic properties] The magnetic properties of the surface-treated copper foil were measured by the following method before and after the following predetermined heat treatment. (Heat treatment) The surface-treated copper foil was cut into a size of 40 mm x 80 mm, and the cut foil was heat-treated in an oven at 300°C in an inert atmosphere for 2 hours to prepare a heat-treated surface-treated copper foil.

[0094] (Measurement of magnetic properties) The magnetic properties of the surface-treated copper foil before and after the heat treatment were measured by the following method. (1) First, the surface-treated copper foil to be measured was cut into 10 measurement samples measuring 10 mm x 10 mm. (2) The magnetic properties of the measurement sample obtained in (1) above were measured under the following conditions. The measurements were carried out using a vibrating sample magnetometer (manufactured by Tamagawa Manufacturing Co., Ltd., "TM-VSM211483-HGC type"). First, the measurement sample was set in a sample holder, and while vibrating the measurement sample, a magnetic field was applied up to +10,000 Oe at a sweep rate of 50 Oe / s, then the magnetic field was swept down to -10,000 Oe at a sweep rate of 50 Oe / s, and then up to +10,000 Oe at a sweep rate of 50 Oe / s, thereby obtaining a BH curve with the vertical axis representing magnetic flux density and the horizontal axis representing magnetic field. (3) Based on the BH curve obtained in (2) above, the magnetic flux density when the magnetic field was +10,000 Oe and the magnetic flux density when the magnetic field was 0 Oe were read, and these were taken as the saturation magnetic flux density Bs [T] and the residual magnetic flux density Br [T]. In this method, two values ​​of magnetic flux density are obtained for each magnetic field. Normally, if the magnetic property measurement is performed correctly, the BH curve will be a vertically symmetrical graph, and the absolute values ​​of the two values ​​calculated for the magnetic field will be almost the same. In this example, we confirmed that the BH curve was vertically symmetrical, and used the value calculated first. (4) The above measurement was performed once for each measurement sample, and the measured values ​​of the 10 measurement samples were averaged to obtain the magnetic flux density of each of the surface-treated copper foils to be measured. The saturation magnetic flux density Bs and residual magnetic flux density Br of the surface-treated copper foil before the heat treatment are "Bs0" and "Br0", and the saturation magnetic flux density Bs and residual magnetic flux density Br of the surface-treated copper foil after the heat treatment are "Bs 300 " and "Br 300 " will be displayed. In addition, "A×10^-B" in the table means "A×10 -B " means (5) Furthermore, the saturation magnetic flux density Bs0 and residual magnetic flux density Br0 of the surface-treated copper foil before the heat treatment obtained by the above measurement and the saturation magnetic flux density Bs 300 and residual magnetic flux density Br 300Based on the values ​​of Bs and Br, the increase rate of the saturation magnetic flux density Bs and the increase rate of the residual magnetic flux density Br after the heat treatment were calculated using the following formulas (I) and (II), respectively. Increase rate of saturation magnetic flux density Bs after heat treatment (%) = [{(Bs 300 -Bs0) / Bs0}×100] (I) Increase rate of residual magnetic flux density Br after heat treatment (%) = [{(Br 300 -Br0) / Br0}×100] (II)

[0095] [Surface roughness (arithmetic mean height Sa)] The arithmetic mean height Sa was measured on the surface of the surface-treated copper foil having a surface treatment film containing a nickel layer using a confocal laser microscope (manufactured by Keyence Corporation, "VK-X1050" and "VK-X1000") in accordance with ISO25178. The objective lens magnification of the confocal laser microscope is 100x, the scan mode is laser confocal, the measurement size is 2048 x 1536, the measurement quality is high precision, and the pitch is 0.08 μm. The calculation of Vvc and Sa was performed under the following filter processing and calculation conditions. <Filter processing and calculation conditions> Image processing: averaging, 3x3, median S filter: None F-operation: Plane tilt correction L filter: 0.025 μm Calculation area: 100μm x 100μm

[0096] [Transmission characteristics] To evaluate the high-frequency characteristics, the transmission loss in the high-frequency band was measured, as described in detail below. A copper-clad laminate was produced by laminating two low-dielectric polyphenylene ether resin films (MEGTRON7, a multilayer substrate material manufactured by Panasonic Corporation, 60 μm thick) with surface-treated copper foil on both sides. The resin film surface and the surface of the nickel-containing surface treatment film on the surface-treated copper foil were positioned facing each other, and the two films were pressed together at a surface pressure of 3.5 MPa and 210°C for 2 hours to produce a double-sided copper-clad laminate. The obtained copper-clad laminate was subjected to circuit processing to produce a printed wiring board with a stripline having a transmission path width of 140 μm and a circuit length of 1000 mm. A high-frequency signal was transmitted through the transmission path of this printed wiring board using a network analyzer (Keysight Technologies, "N5291A"), and the transmission loss was measured. The characteristic impedance was set to 50 Ω. The above measurement was performed three times for one copper-clad laminate, and the average value was used as the measured value. The smaller the absolute value of the measured transmission loss, the smaller the transmission loss and the better the high-frequency characteristics. Using the obtained measured value as an index, the high-frequency characteristics were evaluated according to the following evaluation criteria. S: Absolute value of transmission loss at 40 GHz is less than 41.5 dB A: The absolute value of transmission loss at 40 GHz is 41.5 dB or more and less than 43.0 dB. B: The absolute value of the transmission loss at 40 GHz is 43.0 dB or more and less than 45.0 dB. C: Absolute value of transmission loss at 40 GHz is 45.0 dB or more

[0097] [Heat resistance] A double-sided copper-clad laminate was produced in the same manner as described in the above [Evaluation of high-frequency characteristics]. The obtained double-sided copper-clad laminate was cut into pieces measuring 5 cm x 5 cm to prepare 10 test pieces. The resulting 10 test pieces were heat treated in an oven at 290°C in an air atmosphere for 1 hour. After the heat treatment, the test pieces were removed and each test piece was visually inspected to determine whether or not peeling had occurred between the copper foil and the resin. Based on the results of the inspection of the 10 test pieces, the heat-resistant adhesion was evaluated according to the following criteria. <Evaluation criteria for heat-resistant adhesion> A: 0 or 1 test piece has peeled off B: Two or three test pieces have peeled off. C: Four or more test pieces have peeled off.

[0098] [Table 1]

[0099] [Table 2]

[0100] As shown in Tables 1 and 2, the saturation magnetic flux density (Bs 300 ) is 5.0 × 10 -3 It was confirmed that the surface-treated copper foils having a hardness of 0.1% or less can suppress the magnetization of the nickel layer even after heat treatment, and therefore have excellent transmission characteristics and heat resistance (Examples 1 to 51).

[0101] In contrast, the saturation magnetic flux density (Bs 300 ) is 5.0 × 10 -3 It was confirmed that the surface-treated copper foils exceeding T (Comparative Examples 1 to 6, 8 and 9) had inferior transmission properties compared to the surface-treated copper foils of Examples 1 to 51 because the nickel layer was magnetized after heat treatment. Furthermore, it was confirmed that the surface-treated copper foil (Comparative Example 7), which does not have a surface treatment film including a nickel-containing surface treatment layer on at least one side of the copper foil substrate, has good transmission characteristics but inferior heat resistance compared to the surface-treated copper foils of Examples 1 to 51.

Claims

1. A surface-treated copper foil having a surface treatment film including a nickel-containing surface treatment layer on at least one surface of a copper foil substrate, On the surface having the aforementioned surface treatment film, the amount of nickel deposited is 0.02 mg / dm² or more and 3.5 mg / dm² or less. The saturation magnetic flux density (Bs) after heat treatment at 300°C for 2 hours. ３００ ) is 5.0 x 10 －３ Surface-treated copper foil with a temperature of T or less.

2. The residual magnetic flux density (Br) after heat treatment at 300°C for 2 hours. ３００ ) is 5.0 x 10 －４ The surface-treated copper foil according to claim 1, wherein T is less than or equal to T.

3. The surface-treated copper foil according to claim 1, satisfying the following requirements (I) and (II). Requirement (I): Percentage increase in saturation magnetic flux density Bs after heat treatment at 300°C for 2 hours [{(Bs ３００ - Bs ０ ) / Bs ０ The result of} × 100 is 300% or less. Requirement (II): The increase rate of the residual magnetic flux density Br [{(Br ３００ - Br ０ ) / Br ０} × 100] after heat treatment at 300°C for 2 hours is 300% or less. In the above requirements (I) and (II), Bs ３００ This is the saturation magnetic flux density, Bs, after heat treatment at 300°C for 2 hours. ０ Br is the saturation magnetic flux density in the state before the heat treatment. ３００ This is the residual magnetic flux density after heat treatment at 300°C for 2 hours, Br ０ This is the residual magnetic flux density in the state before the heat treatment.

4. On the surface having the aforementioned surface treatment film, the amount of nickel deposited is 0.02 mg / dm ２ The above 3.0 mg / dm ２ The surface-treated copper foil according to claim 1, which is as follows:

5. The surface treatment film comprises, in order from the copper foil substrate side, a roughening treatment layer and a nickel-containing surface treatment layer. The surface-treated copper foil according to claim 1, wherein the arithmetic mean height Sa on the surface of the surface-treated film, measured optically in accordance with ISO 25178, is 0.02 μm or more and 0.35 μm or less.

6. The surface-treated copper foil according to claim 1, wherein the nickel-containing surface treatment layer is composed of a nickel alloy containing one or more elements selected from the group consisting of zinc, phosphorus, molybdenum, tungsten, chromium, iron, cobalt, and niobium.

7. A copper-clad laminate comprising a surface-treated copper foil according to any one of claims 1 to 6.

8. A printed circuit board comprising a copper-clad laminate as described in claim 7.