Surface-treated copper foil, copper-clad laminates using said surface-treated copper foil, and printed circuit boards

Abstract

This surface-treated copper foil, comprising a heat-resistant treatment layer and a chromate treatment layer but without a roughening treatment layer, exhibits excellent heat resistance and corrosion resistance. Furthermore, because the amount of nickel and chromium adhering to the treated surface is small, there is less conductor loss due to dissimilar metals, and because of its low roughness and lack of conductor loss due to roughening particles, it is suitable for copper-clad laminates used in high-speed transmission printed circuit boards. [Solution] The arithmetic mean height Sa of the untreated copper foil surface is less than 0.27 μm, the unfolded interface area ratio Sdr is less than 6%, the surface area ratio calculated from Sdr is A, and the two-dimensional area of ​​the surface-treated copper foil surface is 1 m². 2 When the amount of nickel deposited per unit area (mg) is B, the surface area is 1 m². 2 The amount of nickel deposited per unit [B / A] is 5 mg to 31 mg, and the two-dimensional area of ​​the surface-treated copper foil surface is 1 m². 2 When the amount of chromium deposited per unit area (mg) is C, the surface area is 1 m². 2 Surface-treated copper foil with a chromium content per unit area [C / A] of 1 mg to 4 mg.

Description

[Technical Field]

[0001] This invention relates to a surface-treated copper foil. More specifically, the surface-treated copper foil comprises a heat-resistant treatment layer containing nickel and a chromate treatment layer, but does not have a roughening treatment layer. It exhibits excellent heat resistance and corrosion resistance, and because the amount of nickel and chromium deposited per unit surface area of ​​the treated surface is small, there is little conductor loss due to these dissimilar metals. Furthermore, it has low roughness and no conductor loss due to roughening particles, making it suitable for use in copper-clad laminates for high-speed transmission printed circuit boards. [Background technology]

[0002] In recent years, printed circuit boards have increasingly been used in smartphones compatible with the fifth-generation mobile communication standard (5G), network equipment such as base stations and routers, and even in-vehicle millimeter-wave radar systems.

[0003] Development of next-generation printed circuit boards is also underway, with an eye on the 6th generation mobile communication standard (6G), which is scheduled to be available around 2030.

[0004] Printed circuit boards used in 5G / 6G compatible devices and millimeter-wave radars, etc., are required to minimize signal loss (hereinafter referred to as "insertion loss") when transmitting high-speed, high-frequency signals.

[0005] Generally, insertion loss is the sum of dielectric loss and conductor loss.

[0006] Copper-clad laminates, which are the material used for printed circuit boards, are composed of an insulating resin substrate and copper foil.

[0007] Insulating resin substrates are required to have low dielectric properties to suppress dielectric loss, and copper foils are required to have low roughness to suppress conductor loss.

[0008] Various types of low-dielectric insulating resin substrates have been developed.

[0009] Typical examples include m-PI( M odified P oly i mide, modified polyimide, and LCP ( L iquid C rystal P Olymer, liquid crystal polymer, m-PPE ( M odified P olyphenylene e Examples include (ther, modified polyphenylene ether), etc.

[0010] Various types of low-roughness copper foil are available from different copper foil manufacturers, and further improvements are being made to them.

[0011] For copper foil used in copper-clad laminates for high-speed transmission-compatible printed circuit boards, surface-treated copper foil with a ten-point average roughness Rz of less than 1 μm, as measured with a stylus-type roughness meter, is becoming the mainstream.

[0012] Conventionally, copper-clad laminates have ensured practically acceptable adhesion by combining two types of adhesion: physical adhesion utilizing the anchoring effect of irregularities derived from roughened particles formed on the copper foil surface to the insulating resin substrate, and chemical adhesion utilizing the chemical bonding at the interface between the copper foil and the insulating resin substrate.

[0013] However, low-dielectric insulating resin substrates have fewer highly polar functional groups, i.e., fewer functional groups that can bond with molecules on the copper foil surface, in order to reduce dielectric loss. As a result, their chemical adhesion is lower compared to ordinary insulating resin substrates.

[0014] Because of its low chemical adhesion, physical adhesion is crucial to ensure proper adhesion between the low-dielectric insulating resin substrate and the copper foil.

[0015] To achieve physical adhesion, copper foil requires an appropriate roughening treatment layer that provides a high anchoring effect to a low-dielectric insulating resin substrate while maintaining low roughness.

[0016] Among low-dielectric insulating resin substrates, fluorine-containing insulating resin substrates are particularly low dielectric, making them an important factor in achieving low insertion loss in high-speed transmission-compatible printed circuit boards for equipment using millimeter-wave signals and 6G-compatible equipment. It is expected that their use in copper-clad laminates for high-speed transmission-compatible printed circuit boards will increase in the future.

[0017] However, because it has lower dielectric properties, it has the problem of having lower adhesion to copper foil.

[0018] In response to this, in recent years, techniques have been put into practical use to improve the adhesion of fluorine-containing insulating resin substrates, such as providing an adhesive layer on the surface of the insulating resin substrate or chemically modifying the surface of the insulating resin substrate by irradiating it with plasma (for example, Patent Document 2, mentioned later).

[0019] Through surface modification technology for low-dielectric insulating resin substrates, a new chemical adhesion force is achieved between the fluorine-containing insulating resin substrate and the copper foil. This allows for sufficient adhesion even without the physical adhesion provided by roughened particles formed on the copper foil, as was the case in the past.

[0020] If the surface-treated copper foil does not have a roughening layer, the surface roughness will decrease, and furthermore, the surface area per two-dimensional area will also decrease. As a result, when a circuit is formed using this copper foil, the conductor distance over which the signal flows will be shortened.

[0021] Generally, due to the skin effect, signals flowing through a circuit, i.e., copper foil, become more concentrated on the surface of the copper foil as their frequency increases. Therefore, it is believed that reducing the surface roughness of the surface-treated copper foil and further reducing its surface area shortens the conductor distance and thus reduces conductor loss.

[0022] However, copper-clad laminates require not only transmission characteristics but also heat resistance and corrosion resistance, so they are generally equipped with heat-resistant and oxidation-preventive treatment layers made of dissimilar metals such as nickel.

[0023] Focusing on the amount of dissimilar metals such as nickel adhering to the treated surface, the absence of a roughening layer reduces the surface area. Therefore, even if the amount of metal adhering per two-dimensional area remains unchanged, the amount of metal adhering per surface area increases.

[0024] Compared to copper foil with a conventional roughened layer, an increase in the amount of adhesion per unit surface area will result in an increase in the thickness of the heat-resistant treatment layer made of dissimilar metals.

[0025] Even if the conductor distance is shortened, the presence of a thick layer of dissimilar metals, especially nickel which has a higher resistance than copper, in the heat-resistant treatment layer results in increased conductor loss.

[0026] Furthermore, if the thickness of the heat-resistant treatment layer is made too thin in order to reduce conductor loss, the heat resistance decreases, which can lead to problems such as oxidation of the copper foil treatment surface after solder floating, resulting in a decrease in peel strength.

[0027] Therefore, there is a need for the development of a surface-treated copper foil that can be suitably used in high-speed transmission printed circuit boards, which has low surface roughness without a roughening layer, a small surface area, low conductor loss, low conductor loss due to dissimilar metals, and excellent heat resistance and corrosion resistance. [Prior art documents] [Patent Documents]

[0028] [Patent Document 1] Japanese Patent Publication No. 2021-098892 [Patent Document 2] WO2023 / 032958 [Overview of the Initiative] [Problems that the invention aims to solve]

[0029] Patent Document 1 proposes a surface-treated copper foil comprising a surface treatment layer (roughening treatment layer) having an average particle size of roughened particles of 10 nm to 100 nm, and an oxidation-preventive layer containing nickel and phosphorus.

[0030] However, if the roughening treatment layer is removed from the surface-treated copper foil described in Patent Document 1, the conductor distance over which the signal flows is shortened, but the nickel and phosphorus contained in the anti-oxidation layer remain. As a result, the amount of nickel and phosphorus deposited per unit surface area, i.e., the thickness of the anti-oxidation layer, increases, resulting in a surface-treated copper foil with high conductor loss. Therefore, it has the problem that it cannot be used in printed circuit boards for high-speed transmission.

[0031] The inventors, with the resolution of the aforementioned problems as their technical challenge, conducted numerous prototypes and evaluations, and have now developed a surface-treated copper foil comprising a heat-resistant treatment layer containing nickel on at least one side of an untreated copper foil, a chromate treatment layer on the heat-resistant treatment layer, and no roughening treatment layer on either side of the untreated copper foil, wherein the untreated copper foil has an arithmetic mean height Sa of less than 0.27 μm as measured by a laser microscope on the surface treated, an undeveloped interface area ratio Sdr of less than 6%, and a surface area ratio (S) calculated from the Sdr (S) (Surface area (m 2 ) / 2D area (m 2 Let A be the surface treatment copper foil treatment surface, and the two-dimensional area of ​​the surface treatment copper foil treatment surface be 1 m². 2 When the amount of nickel deposited per unit area (mg) is B, the surface area is 1 m². 2 The amount of nickel deposited per unit [B / A] is 5 mg or more and 31 mg or less, and the two-dimensional area of ​​the treated surface is 1 m². 2 When the amount of chromium deposited per unit area (mg) is C, the surface area is 1 m². 2 A surface-treated copper foil with a chromium deposition rate [C / A] of 1 mg or more and 4 mg or less exhibits excellent heat resistance and corrosion resistance. Furthermore, because the amount of nickel and chromium deposited per unit surface area of ​​the treated surface is low, there is less conductor loss due to these dissimilar metals. Additionally, it has a low roughness and no conductor loss due to roughening particles, making it suitable for use in copper-clad laminates used in high-speed transmission printed circuit boards. This remarkable finding has thus achieved the aforementioned technical objective. [Means for solving the problem]

[0032] The aforementioned technical problems can be solved by the present invention as follows.

[0033] The present invention relates to a surface-treated copper foil having a heat-treatment layer containing nickel on at least one surface of an untreated copper foil, a chromate treatment layer on the heat-treatment layer, and no roughening treatment layer on any surface of the untreated copper foil. The untreated copper foil has an arithmetic mean height Sa measured by a laser microscope on the surface to be surface-treated of less than 0.27 μm and a developed interface area ratio Sdr of less than 6%. The surface area ratio (surface area (m 2 ) / two-dimensional area (m 2 )) calculated from the Sdr is designated as A, and the nickel adhesion amount per 1 m 2 of the two-dimensional area of the treated surface of the surface-treated copper foil is designated as B. The nickel adhesion amount per 1 m 2 of the surface area [B / A] is 5 mg or more and 31 mg or less. The chromium adhesion amount per 1 m 2 of the two-dimensional area of the treated surface is designated as C. The chromium adhesion amount per 1 m 2 of the surface area [C / A] is 1 mg or more and 4 mg or less. This is a surface-treated copper foil.

[0034] Further, the present invention relates to the surface-treated copper foil in which the chromate treatment layer is a chromate treatment layer containing zinc, and when the zinc adhesion amount per 1 m 2 of the two-dimensional area of the treated surface is designated as D, the zinc adhesion amount per 1 m 2 of the surface area [D / A] is 7 mg or less. This is the surface-treated copper foil according to claim 1.

[0035] Further, the present invention relates to the above-mentioned surface-treated copper foil provided with a silane coupling agent treatment layer on the chromate treatment layer.

[0036] Further, the present invention relates to a copper-clad laminate obtained by laminating the above-mentioned surface-treated copper foil on an insulating resin base material.

[0037] Further, the present invention relates to the above-mentioned copper-clad laminate in which the insulating resin base material is an adhesive layer and / or a surface-modified fluorine-containing insulating resin base material.

[0038] Further, the present invention relates to a printed wiring board using the above-mentioned copper-clad laminate. [Effects of the Invention]

[0039] The surface-treated copper foil of the present invention has a low roughness, with an arithmetic mean height Sa of less than 0.27 μm measured by a laser microscope on the surface treated of the untreated copper foil, and a developed interface area ratio Sdr of less than 6% measured by a laser microscope on the same surface. Furthermore, it is a surface-treated copper foil with low conductor loss because it does not have a roughening treatment layer and does not contain roughening particles.

[0040] Furthermore, because it is equipped with a heat-resistant treatment layer containing nickel and a chromate treatment layer, it is a surface-treated copper foil with high heat resistance and corrosion resistance.

[0041] Furthermore, the surface area ratio (surface area (m) calculated from the above Sdr 2 ) / 2D area (m 2 Let A be the surface treatment copper foil treatment surface, and the two-dimensional area of ​​the surface treatment copper foil treatment surface be 1 m². 2 When the amount of nickel deposited per unit area (mg) is B, the surface area is 1 m². 2 The amount of nickel deposited per unit [B / A] is 5 mg or more and 31 mg or less, and the two-dimensional area of ​​the treated surface is 1 m². 2 When the amount of chromium deposited per unit area (mg) is C, the surface area is 1 m². 2 The amount of chromium deposited per unit area [C / A] is 1 mg or more and 4 mg or less. Because the amount of nickel and chromium deposited per unit surface area is small, this surface-treated copper foil also exhibits low conductor loss due to dissimilar metals.

[0042] Furthermore, the chromate treatment layer is a chromate treatment layer containing zinc, and the two-dimensional area of ​​the treated surface is 1 m². 2 When the amount of zinc deposited per unit area (mg) is D, the surface area is 1 m². 2 If the zinc deposition rate per unit [D / A] is 7 mg or less, the surface-treated copper foil will have even better heat resistance and corrosion resistance.

[0043] Furthermore, by adding a silane coupling agent layer on top of the chromate treatment layer, a surface-treated copper foil with even better heat resistance can be obtained.

[0044] Because the surface-treated copper foil in this invention has low conductor loss, the copper-clad laminate obtained by laminating the surface-treated copper foil and an insulating resin substrate in this invention has low insertion loss and excellent transmission characteristics.

[0045] In particular, a copper-clad laminate formed by bonding a fluorine-containing insulating resin substrate, which has an adhesive layer on its surface and / or has undergone surface modification, will have low conductor loss in the surface-treated copper foil and low dielectric loss in the insulating resin substrate, resulting in a copper-clad laminate with excellent adhesion. Therefore, it can be suitably used in printed circuit boards for high-speed transmission. [Brief explanation of the drawing]

[0046] [Figure 1] This is a schematic diagram of the surface-treated copper foil according to the present invention. [Modes for carrying out the invention]

[0047] In this specification, the outermost surface of the surface-treated copper foil is referred to as the "treated surface," the unfolded interface area ratio measured in accordance with JIS B 0681-3 using a confocal microscope (laser microscope) in accordance with ISO 25178-607 is referred to as Sdr, and the surface area ratio (surface area (m)) is calculated from Sdr is referred to as the surface area ratio (m 2 ) / 2D area (m 2 )) is A, and the processing surface has a 2D area of ​​1 m². 2 Let B be the amount of nickel deposited per unit area (mg), and let B be the 2D area of ​​1 m². 2 Let C be the amount of chromium deposited per unit area (mg), and let C be the amount of chromium deposited per 2D area (1 m²). 2 Let D be the amount of zinc deposited per unit (mg), and the 2D area be 1 m². 2 The amount of phosphorus attached per unit (mg) is sometimes referred to as E.

[0048] The present invention relates to a surface-treated copper foil comprising a heat-resistant treatment layer on at least one side of an untreated copper foil, a chromate treatment layer on the heat-resistant treatment layer, and no roughening treatment layer on either side of the untreated copper foil.

[0049] <Untreated copper foil> The copper foil used in this invention before surface treatment (hereinafter referred to as "untreated copper foil") is not particularly limited, and any copper foil without a distinguishing front and back side, such as rolled copper foil, or copper foil with a distinguishing front and back side, such as electrolytic copper foil, can be used.

[0050] The surface of the untreated copper foil to which the surface treatment is applied is not particularly limited; any surface may be used for rolled copper foil, and either the deposited surface or the drum surface may be used for electrolytic copper foil.

[0051] The surface of the untreated copper foil to be surface-treated preferably has an arithmetic mean height Sa of less than 0.27 μm, and more preferably less than 0.15 μm, when measured using a confocal microscope (laser microscope) in accordance with ISO 25178-607 and in accordance with JIS B 0681-3.

[0052] This is because conductor loss may increase if the arithmetic mean height Sa exceeds 0.27 μm.

[0053] The Sdr of the surface of the untreated copper foil to be treated is preferably less than 6%, and more preferably less than 2.5%.

[0054] This is because if Sdr is 6% or higher, there is a risk that conductor loss will increase.

[0055] The thickness of the untreated copper foil is not particularly limited as long as it is a thickness that can be used on printed circuit boards after surface treatment, but it is preferably 6 μm to 300 μm, and more preferably 12 μm to 35 μm.

[0056] It is preferable to immerse the rolled copper foil in a hydrocarbon-based organic solvent or an alkaline degreasing solution to remove the rolling oil before performing surface treatment.

[0057] It is preferable to immerse the electrolytic copper foil in dilute sulfuric acid to remove the oxide film before performing surface treatment.

[0058] <Heat-resistant treatment layer> The surface-treated copper foil in this invention comprises a heat-resistant treatment layer on at least one surface of the untreated copper foil.

[0059] The heat-resistant treatment layer should contain at least nickel.

[0060] The heat-resistant treatment layer may contain phosphorus along with nickel, as this can improve heat resistance.

[0061] Surface area of ​​the treated surface: 1 m² 2 The nickel content per unit [B / A] is preferably 5 mg to 31 mg.

[0062] If the [B / A] ratio is less than 5 mg, the conduction loss due to nickel will be reduced, but there is a risk that sufficient heat resistance will not be obtained. On the other hand, if it exceeds 31 mg, sufficient heat resistance can be ensured, but there is a risk that the conduction loss will increase.

[0063] The heat-resistant layer can be formed by electrolysis while immersing untreated copper foil in an electrolyte solution.

[0064] The electrolyte used to form the heat-resistant layer is preferably an aqueous solution containing 10 g / L to 70 g / L of nickel-containing compound and 2 g / L to 40 g / L of acetate, prepared to a pH of 4.0 to 5.5, or an aqueous solution containing 10 g / L to 70 g / L of nickel-containing compound, 0.1 g / L to 10.0 g / L of hypophosphate and 2 g / L to 40 g / L of acetate, prepared to a pH of 4.0 to 5.5.

[0065] The nickel-containing compounds in the electrolyte are not particularly limited, but examples include nickel sulfate hexahydrate, nickel chloride hexahydrate, and nickel acetate tetrahydrate.

[0066] The hypophosphate contained in the electrolyte is not particularly limited, but examples include disodium hydrogen phosphite, sodium hypophosphate monohydrate, and nickel hydrogen phosphite.

[0067] The acetate contained in the electrolyte is not particularly limited, but sodium acetate trihydrate is an example.

[0068] Electrolysis involves immersing an insoluble electrode, such as platinum group oxide-coated titanium, as the anode in an electrolyte solution, and immersing an untreated copper foil as the cathode on the opposite side at a certain distance, with a current density of 0.1 A / dm². 2 ~2.0A / dm 2 Electrical charge 0.3C / dm 2 ~2.0C / dm 2 It is preferable to carry out the electrolysis under conditions where the liquid temperature is between 25°C and 45°C.

[0069] <Chromate-treated layer> The present invention relates to a surface-treated copper foil comprising a chromate treatment layer on a heat-resistant treatment layer.

[0070] The chromate-treated layer may contain chromium, or it may contain both chromium and zinc.

[0071] Surface area of ​​the treated surface: 1 m² 2 The amount of chromium deposited per unit [C / A] is preferably 1 mg to 4 mg.

[0072] If the [C / A] ratio is less than 1 mg, sufficient heat resistance may not be obtained. Furthermore, even if more than 4 mg is applied, no further improvement in heat resistance can be expected. Additionally, when a copper-clad laminate is fabricated and the copper is etched, a large amount of chromium may remain on the substrate.

[0073] Surface area of ​​the treated surface: 1 m² 2 The zinc content per unit [D / A] is preferably 7 mg or less.

[0074] This is because if the [D / A] ratio exceeds 7 mg, there is a risk that the drug solution may seep in during circuit formation, reducing adhesion to the insulating resin substrate.

[0075] The chromate treatment layer is formed by electrolyzing copper foil that has a heat-resistant treatment layer applied to it while immersing it in an electrolyte solution. It is possible.

[0076] The electrolyte used to form the chromate treatment layer is preferably an aqueous solution containing 10 g / L to 60 g / L of a chromic acid-containing compound, adjusted to pH 2 to pH 12 with sulfuric acid or sodium hydroxide, or an aqueous solution containing 10 g / L to 60 g / L of a chromic acid-containing compound and 0.2 g / L to 10.0 g / L of zinc ions, adjusted to pH 2 to pH 12 with sulfuric acid or sodium hydroxide.

[0077] Chromic acid-containing compounds are not particularly limited, but sodium dichromate dihydrate is an example.

[0078] The zinc ion source is not particularly limited, but zinc oxide is an example.

[0079] Electrolysis involves immersing an insoluble electrode, such as platinum group oxide-coated titanium, as the anode in an electrolyte solution, and immersing a copper foil with a heat-resistant layer formed on the opposite side at a certain distance as the cathode, with a current density of 0.5 A / dm². 2 ~5A / dm 2 Electrical quantity 1C / dm 2 ~6C / dm 2 It is preferable to carry out the electrolysis under conditions where the liquid temperature is between 25°C and 50°C.

[0080] <Silane coupling agent treated layer> In the present invention, the surface-treated copper foil can have a silane coupling agent treatment layer provided on top of the chromate treatment layer.

[0081] By applying a silane coupling agent treatment layer on top of the chromate treatment layer, a surface-treated copper foil with even greater heat resistance can be obtained.

[0082] The silane coupling agent treated layer can be formed by immersing a copper foil with a chromate-treated layer in an aqueous solution of silane coupling agent prepared at a liquid temperature of 20°C to 50°C, or by spraying it with water, and then washing it with water.

[0083] The silane coupling agent used in the silane coupling agent layer is not particularly limited, and silane coupling agents containing vinyl groups, epoxy groups, styryl groups, methacrylic groups, acrylic groups, amino groups, ureido groups, and mercapto groups can be used. However, silane coupling agents containing amino groups, epoxy groups, or vinyl groups are more preferably used because they have very high hygroscopic and rust-preventive effects.

[0084] Silane coupling agents may be used individually or in combination of two or more.

[0085] Examples of the composition and conditions for forming the silane coupling agent treated layer include γ-aminopropyltriethoxysilane 1 mL / L to 5 mL / L, liquid temperature 25°C to 35°C, and immersion time 15 seconds.

[0086] <Insulating resin substrate> The insulating resin substrate to be bonded to the surface-treated copper foil in the present invention is not particularly limited.

[0087] Examples of insulating resin substrates include epoxy resin substrates and polyimide resin substrates, while examples of low-dielectric resin substrates include polyphenylene ether resin substrates, bismaleimide triazine resin substrates, cycloolefin polymer resin substrates, liquid crystal polymer resin substrates, and fluorine-containing resin substrates provided with a surface-modified layer or adhesive layer by plasma treatment.

[0088] High-speed transmission compatible printed circuit boards are equipped with a surface modification layer and adhesive layer created by plasma treatment. A fluorine-containing resin substrate is preferred. This is because it can improve chemical adhesion and reduce insertion loss. [Examples]

[0089] Examples and comparative examples of the present invention are shown below, but the present invention is not limited thereto.

[0090] For the untreated copper foils used in the examples and comparative examples, electrolytic copper foil or rolled copper foil with a nominal thickness of 18 μm was used. Note that the arithmetic mean heights Sa and Sdr are measurements taken from the surface of the untreated copper foil that has undergone surface treatment.

[0091] Copper foil a: Rolled copper foil with an arithmetic mean height Sa of 0.100 μm and an Sdr of 1.38%. Copper foil b: Rolled copper foil with an arithmetic mean height Sa of 0.060 μm and an Sdr of 0.90%. Copper foil c: Electrolytic copper foil with an arithmetic mean height Sa of 0.018 μm and an Sdr of 0.03%. Copper foil d: Electrolytic copper foil with an arithmetic mean height Sa of 0.156 μm and an Sdr of 2.61%. Copper foil e: Electrolytic copper foil with an arithmetic mean height Sa of 0.113 μm and an Sdr of 2.38%. Copper foil f: Electrolytic copper foil with an arithmetic mean height Sa of 0.275 μm and an Sdr of 6.02%.

[0092] The electrolytic copper foil was immersed in dilute sulfuric acid to remove the oxide film, and then each surface treatment layer was formed.

[0093] The rolled copper foil was immersed in a hydrocarbon-based organic solvent or an alkaline degreasing solution to remove the rolling oil, and then each surface treatment layer was formed.

[0094] (Example 1) <Untreated copper foil> Copper foil a was used as the untreated copper foil.

[0095] <Formation of heat-resistant layer> An electrolyte solution was used, prepared by adjusting the pH of an aqueous solution containing 30 g / L nickel sulfate hexahydrate, 2 g / L sodium hypophosphite monohydrate, and 10 g / L sodium acetate trihydrate to 4.5.

[0096] An insoluble electrode, such as platinum group oxide-coated titanium, is immersed as the anode in the electrolyte, and an untreated copper foil is immersed as the cathode on the opposite side at a certain distance, with a current density of 0.7 A / dm². 2 Electrical charge 1.4C / dm 2 A heat-resistant treated layer was formed by electrolysis under electrolytic conditions of a liquid temperature of 30°C.

[0097] <Formation of chromate-treated layer> An electrolyte solution was prepared by adjusting the pH of an aqueous solution containing 12.5 g / L of sodium dichromate dihydrate and 2.5 g / L of zinc ions to pH 12.

[0098] An insoluble electrode, such as platinum group oxide-coated titanium, is immersed in the electrolyte as the anode, and a copper foil with the heat-resistant treatment layer formed on the opposite side is immersed as the cathode at a certain distance, with a current density of 2.0 A / dm². 2 Electricity level 6.0 C / dm 2 A chromate-treated layer was formed by electrolysis under electrolytic conditions at a liquid temperature of 25°C.

[0099] <Formation of silane coupling agent treated layer> A copper foil with a chromate-treated layer was immersed for 10 seconds in an aqueous solution containing 5 ml / L of γ-aminopropyltriethoxysilane at a liquid temperature of 25°C, and then removed and dried to form a silane coupling agent-treated layer, thereby obtaining the surface-treated copper foil of Example 1.

[0100] (Example 2) Using copper foil c as the untreated copper foil, a heat-resistant treatment layer was applied, with a current density of 1.8 A / dm². 2 Electrical charge 1.8 C / dm 2 The product was prepared under the same conditions as in Example 1, except that it was formed under electrolytic conditions with a liquid temperature of 30°C.

[0101] (Example 3) Using copper foil c as the untreated copper foil, a heat-resistant treatment layer was applied, with a current density of 1.0 A / dm². 2 Electrical charge 1.0 C / dm 2 The product was prepared under the same conditions as in Example 1, except that it was formed under electrolytic conditions at a liquid temperature of 30°C.

[0102] (Example 4) Using copper foil c as the untreated copper foil, a heat-resistant treatment layer was applied to a current density of 0.5 A / dm 2 Electrical charge 0.5C / dm 2 The product was prepared under the same conditions as in Example 1, except that it was formed under electrolytic conditions with a liquid temperature of 30°C.

[0103] (Example 5) Using copper foil c as the untreated copper foil, a heat-resistant treatment layer was applied to a current density of 0.4 A / dm 2 Electrical charge 0.4C / dm 2 The product was prepared under the same conditions as in Example 1, except that it was formed under electrolytic conditions at a liquid temperature of 30°C.

[0104] (Example 6) Using copper foil d as the untreated copper foil, a heat-resistant treatment layer was applied, with a current density of 0.7 A / dm 2 Electrical charge 1.4C / dm 2 The product was prepared under the same conditions as in Example 1, except that it was formed under electrolytic conditions with a liquid temperature of 30°C.

[0105] (Example 7) Using copper foil e as the untreated copper foil, a heat-resistant treatment layer was applied to a current density of 0.7 A / dm². 2 Electrical charge 1.4C / dm 2 The product was prepared under the same conditions as in Example 1, except that it was formed under electrolytic conditions with a liquid temperature of 30°C.

[0106] (Example 8) Using copper foil c as the untreated copper foil, the heat-resistant treatment layer was prepared using an electrolyte solution containing 30 g / L nickel sulfate hexahydrate and 10 g / L sodium acetate trihydrate, adjusted to pH 4.5, with a current density of 0.7 A / dm². 2 Electrical charge 1.4C / dm 2 The product was prepared under the same conditions as in Example 1, except that it was formed under electrolytic conditions with a liquid temperature of 30°C.

[0107] (Example 9) Using copper foil c as the untreated copper foil, a heat-resistant treatment layer was applied, with a current density of 0.3 A / dm 2 Electrical charge 0.6C / dm 2 The sample was prepared under the same conditions as in Example 1, except that it was formed under electrolytic conditions at a liquid temperature of 30°C and no silane coupling agent treatment layer was formed.

[0108] (Example 10) Using copper foil c as the untreated copper foil, a heat-resistant treatment layer was applied, with a current density of 0.3 A / dm 2 Electrical charge 0.6C / dm2 The chromate treatment layer was formed under electrolytic conditions at a liquid temperature of 30°C, using an electrolyte solution prepared by adjusting the pH of an aqueous solution containing 12.5 g / L of sodium dichromate dihydrate and 2.5 g / L of zinc ions to 4.9, with a current density of 0.5 A / dm². 2 Electrical charge 1.0 C / dm 2 The sample was prepared under the same conditions as in Example 1, except that it was formed under electrolytic conditions at a liquid temperature of 25°C and that a silane coupling agent treatment layer was not formed.

[0109] (Example 11) Using copper foil c as the untreated copper foil, a heat-resistant treatment layer was applied, with a current density of 0.3 A / dm 2 Electrical charge 0.6C / dm 2 The chromate-treated layer was formed under electrolytic conditions at a liquid temperature of 30°C, using an electrolyte solution prepared by adjusting the pH of an aqueous solution containing 12.5 g / L of sodium dichromate dihydrate and 1.0 g / L of zinc ions to pH 12, with a current density of 2.0 A / dm². 2 Electricity level 6.0 C / dm 2 The sample was prepared under the same conditions as in Example 1, except that it was formed under electrolytic conditions at a liquid temperature of 25°C and that a silane coupling agent treatment layer was not formed.

[0110] (Example 12) Using copper foil c as the untreated copper foil, a heat-resistant treatment layer was applied, with a current density of 0.3 A / dm 2 Electrical charge 0.6C / dm 2 The chromate treatment layer was formed under electrolytic conditions at a liquid temperature of 30°C, using an electrolyte solution prepared by adjusting the pH of an aqueous solution containing 12.5 g / L of sodium dichromate dihydrate and 6.0 g / L of zinc ions to 12, with a current density of 2.0 A / dm². 2 Electricity level 6.0 C / dm 2 The sample was prepared under the same conditions as in Example 1, except that it was formed under electrolytic conditions at a liquid temperature of 25°C and that a silane coupling agent treatment layer was not formed.

[0111] (Example 13) Using copper foil c as the untreated copper foil, a heat-resistant treatment layer was applied to a current density of 0.3 A / dm². 2 Electrical charge 0.6C / dm 2The chromate treatment layer was formed under electrolytic conditions at a liquid temperature of 30°C, using an electrolyte solution prepared by adjusting the pH of an aqueous solution containing 12.5 g / L of sodium dichromate dihydrate to 12, with a current density of 2.0 A / dm². 2 Electricity level 6.0 C / dm 2 The sample was prepared under the same conditions as in Example 1, except that it was formed under electrolytic conditions at a liquid temperature of 25°C and that a silane coupling agent treatment layer was not formed.

[0112] (Comparative Example 1) Using copper foil b as the untreated copper foil, an aqueous solution with a pH of 4.8 containing 35 g / L of copper sulfate pentahydrate and 100 g / L of pentasodium diethylenetriaminepentaacetate was used as the electrolyte. An insoluble electrode such as platinum group oxide coated titanium was immersed in the electrolyte as the anode, and the untreated copper foil was immersed on the opposite side at a certain distance as the cathode, with a current density of 5 A / dm². 2 Electricity level 60C / dm 2 A roughened layer was formed on untreated copper foil under electrolytic conditions at a liquid temperature of 32°C.

[0113] A heat-resistant treatment layer is applied to the formed roughened layer at a current density of 2.5 A / dm 2 Electricity level 6.0 C / dm 2 It was formed under electrolytic conditions with a liquid temperature of 30°C.

[0114] The material was prepared under the same conditions as in Example 1, except for the formation of the roughened layer and the heat-resistant layer.

[0115] (Comparative Example 2) Copper foil b is used as the untreated copper foil, and the heat-resistant treatment layer is applied at a current density of 2.5 A / dm 2 Electricity level 6.0 C / dm 2 The product was prepared under the same conditions as in Example 1, except that it was formed under electrolytic conditions at a liquid temperature of 30°C.

[0116] (Comparative Example 3) The same conditions as in Example 1 were used, except that copper foil c was used as the untreated copper foil and no heat-resistant treatment layer was formed.

[0117] (Comparative Example 4) Copper foil c was used as the untreated copper foil, and the heat-resistant treatment layer was formed under the electrolysis conditions of a current density of 0.3 A / dm 2 , an electric quantity of 0.6 C / dm 2 , a liquid temperature of 30 °C, and it was fabricated under the same conditions as in Example 1 except that the chromate treatment layer was not formed.

[0118] (Comparative Example 5) Copper foil c was used as the untreated copper foil, and the heat-resistant treatment layer was formed under the electrolysis conditions of a current density of 0.3 A / dm 2 , an electric quantity of 0.6 C / dm 2 , a liquid temperature of 30 °C, and it was fabricated under the same conditions as in Example 1 except that the chromate treatment layer and the silane coupling agent treatment layer were not formed.

[0119] (Comparative Example 6) Copper foil f was used as the untreated copper foil, and the heat-resistant treatment layer was formed under the electrolysis conditions of a current density of 0.7 A / dm 2 , an electric quantity of 1.4 C / dm 2 , a liquid temperature of 30 °C, and it was fabricated under the same conditions as in Example 1 except for this.

[0120] (Comparative Example 7) Copper foil c was used as the untreated copper foil, and it was immersed in an electrolytic solution at a liquid temperature of 40 °C containing 57 g / L of copper sulfate pentahydrate, 100 g / L of sulfuric acid, 15 mg / L of tungsten ions, and 35 mg / L of chlorine ions, with an insoluble electrode of platinum group oxide-coated titanium as the anode, and an untreated copper foil was immersed as the cathode on the opposite side at regular intervals. The electrolysis conditions were a current density of 50 A / dm 2 , an electric quantity of 125 C / dm 2 to form a dendritic particle layer on the untreated copper foil.

[0121] It was immersed in an electrolytic solution at a liquid temperature of 40 °C composed of 220 g / L of copper sulfate pentahydrate and 110 g / L of sulfuric acid, with an insoluble electrode of platinum group oxide-coated titanium as the anode, and a copper foil on which a dendritic particle layer was formed was immersed as the cathode on the opposite side at regular intervals, and electrolyzed at a current density of 5 A / dm 2 , an electric quantity of 440 C / dm 2 to form a roughened treatment layer by electroplating copper on the dendritic particle layer.

[0122] A current density of 1.8 A / dm² was applied to the formed roughened layer. 2 Electrical charge 1.8 C / dm 2 A heat-resistant treated layer was formed under electrolytic conditions at a liquid temperature of 30°C.

[0123] The material was prepared under the same conditions as in Example 1, except for the formation of the roughened layer and the heat-resistant layer.

[0124] Table 1 shows the surface-treated copper foils of the examples and comparative examples.

[0125] [Table 1]

[0126] The surface-treated copper foil was evaluated using the following method.

[0127] <Measurement of arithmetic mean height Sa> In the examples and comparative examples without a roughened layer, the surface of the untreated copper foil was treated. In comparative examples 1 and 7, which had a roughened layer, the roughened surface was treated. Using a laser microscope LEXT OLS5000 (manufactured by Olympus Corporation), a confocal microscope compliant with ISO 25178-607, the arithmetic mean height Sa was measured in accordance with JIS B 0681-3, with an evaluation area of ​​125 μm × 125 μm, an S filter of 0.5 μm, an L filter of 50 μm, and an F calculation for a multi-order surface (3rd order).

[0128] <Measurement of the unfolded surface area ratio (Sdr)> In the examples and comparative examples without a roughened layer, the surface of the untreated copper foil that has undergone surface treatment, and in comparative examples 1 and 7 with a roughened layer, the roughened surface, are subject to ISO 25178- Using a laser microscope LEXT OLS5000 (manufactured by Olympus Corporation), a confocal microscope compliant with JIS B 0687, the unfolded interface area ratio Sdr was measured in accordance with JIS B 0681-3, with an evaluation area of ​​125 μm × 125 μm, an S filter of 0.5 μm, an L filter of 50 μm, and an F calculation for a multi-order surface (3rd order).

[0129] <Calculation of surface area ratio> The surface area ratio A (surface area (m 2 ) ÷ two-dimensional area (m 2 )) was calculated by the following formula (1) using each measured Sdr.

[0130] (Formula 1) Surface area ratio A = (Sdr / 100) + 1

[0131] <Surface area of 1 m 2 Calculation of nickel deposition amount (mg) per unit area (B / A)> For each treated surface of the surface-treated copper foils of the examples and comparative examples, the nickel deposition amount B (mg) per unit area of 2D area of 1 m was calculated by the fundamental parameter method from the fluorescence X-ray intensity measured with a fluorescence X-ray analyzer ZSX Primus IV (manufactured by Rigaku Corporation), and the nickel deposition amount per unit area (B / A) of 1 m was calculated by dividing by the surface area ratio A. 2 2

[0132] <Surface area of 1 m 2 Calculation of chromium deposition amount (mg) per unit area (C / A)> For each treated surface of the surface-treated copper foils of the examples and comparative examples, the chromium deposition amount C (mg) per unit area of 2D area of 1 m was calculated by the fundamental parameter method from the fluorescence X-ray intensity measured with a fluorescence X-ray analyzer ZSX Primus IV (manufactured by Rigaku Corporation), and the chromium deposition amount per unit area (C / A) of 1 m was calculated by dividing by the surface area ratio A. 2 2

[0133] <Surface area of 1 m 2 Calculation of zinc deposition amount (mg) per unit area (D / A)> For each treated surface of the surface-treated copper foils of the examples and comparative examples, the zinc deposition amount D (mg) per unit area of 2D area of 1 m was calculated by the fundamental parameter method from the fluorescence X-ray intensity measured with a fluorescence X-ray analyzer ZSX Primus IV (manufactured by Rigaku Corporation), and the zinc deposition amount per unit area (D / A) of 1 m was calculated by dividing by the surface area ratio A. 2 2 ​​​​​​

[0134] <Surface area 1m 2 Calculation of phosphorus deposition amount per unit (mg) (E / A) For each treated surface of the copper foil in the examples and comparative examples, the fluorescence X-ray intensity was measured using a ZSX Primus IV (manufactured by Rigaku Corporation) X-ray fluorescence analyzer, and the fundamental parameter method was used to obtain the two-dimensional area of ​​1 m². 2 The amount of phosphorus deposited per unit area E (mg) is calculated and divided by the surface area ratio A to obtain a surface area of ​​1 m². 2 The amount of phosphorus deposited per unit area (E / A) was calculated.

[0135] <Heat resistance test> The surface-treated copper foils of the examples and comparative examples were cut into 5cm x 5cm pieces to serve as test specimens. The test specimens were suspended in solder so that the side opposite to the treated surface was in contact with solder at 260°C, and the time until the treated surface changed color after contact with the solder was measured and evaluated as follows. ◎: 60 seconds or more ○: 40 seconds or more ×: Less than 40 seconds

[0136] <Transmission Characteristics> Using the treated surfaces of the copper foils in the examples and comparative examples as the bonding surfaces, both sides of a fluorine-containing resin substrate RO3003 (nominal thickness 100 μm / manufactured by Rogers Corporation) were aligned, and a vacuum hot press machine KVHC-II (manufactured by Kitagawa Seiki Co., Ltd.) was used to heat and press mold the copper foils under vacuum, at a temperature of 370°C and a surface pressure of 3 MPa for 45 minutes to obtain a copper-clad laminate.

[0137] The obtained copper-clad laminate was used to form a single-ended microstrip circuit on an etching device SPE-40 (manufactured by Ninomiya Systems Co., Ltd.) to create a test specimen.

[0138] The test specimen had a circuit length of 100 mm, and the circuit width was set so that the characteristic impedance was 50 Ω.

[0139] For each test specimen, the insertion loss (S21) at a frequency of 20 GHz was measured using a network analyzer E5071C (manufactured by Keysight Technologies, Inc.) and evaluated as follows. ○: -1.84dB / 100mm or higher ×: -1.84dB / less than 100mm

[0140] <Overall Rating> Based on a comprehensive evaluation of the heat resistance test and transmission characteristics, the following results were obtained. ○: If the evaluation for all of the above tests was ○ or ◎ ×: If one or more of the above tests receive an evaluation of ×.

[0141] The measurement results for each surface-treated copper foil in the examples and comparative examples are shown in [Table 2], and the results for the heat resistance test and transmission characteristics are shown in [Table 3].

[0142] [Table 2]

[0143] [Table 3]

[0144] Examples 1 to 13 demonstrate that the surface-treated copper foil of the present invention exhibits excellent transmission characteristics, with an insertion loss S21 of -1.84 dB / 100 mm or more even at a high frequency of 20 GHz, and also possesses excellent heat resistance, not discoloring even when exposed to solder at a temperature of 260 °C for 40 seconds. [Industrial applicability]

[0145] The surface-treated copper foil of the present invention comprises a heat-resistant treatment layer and a chromate treatment layer, exhibiting excellent heat resistance and corrosion resistance. Furthermore, because the amount of nickel and chromium deposited per unit surface area of ​​the treated surface is small, there is little conductor loss due to dissimilar metals. Moreover, it has low roughness and does not have a roughening treatment layer, so there is no conductor loss due to roughening particles. Therefore, a copper-clad laminate formed by laminating the surface-treated copper foil of the present invention with a low-dielectric resin substrate has very low insertion loss and can be suitably used in high-speed transmission-compatible printed circuit boards. Therefore, the industrial applicability of the present invention is high.

Claims

1. A surface-treated copper foil comprising a heat-resistant treatment layer containing nickel on at least one surface of an untreated copper foil, a chromate treatment layer on the heat-resistant treatment layer, and no roughening treatment layer on either surface of the untreated copper foil, wherein the untreated copper foil has an arithmetic mean height Sa of less than 0.27 μm measured by a laser microscope on the surface to be treated, and an unfolded interface area ratio Sdr of less than 6%. The surface area ratio (surface area (m)) calculated from the aforementioned Sdr ２ ) / 2D area (m ２ )) is A, and the two-dimensional area of ​​the surface-treated copper foil treatment surface is 1 m ２ When the amount of nickel deposited per unit area (mg) is B, the surface area is 1 m². ２ The nickel deposition amount per unit [B / A] is 5 mg or more and 31 mg or less, and the two-dimensional area of ​​the treated surface is 1 m². ２ When the amount of chromium deposited per unit area (mg) is C, the surface area is 1 m². ２ Surface-treated copper foil having a chromium deposition rate [C / A] of 1 mg or more and 4 mg or less per unit area.

2. The chromate treatment layer is a chromate treatment layer containing zinc, and the two-dimensional area of ​​the treated surface is 1 m². ２ When the amount of zinc deposited per unit area (mg) is D, the surface area is 1 m². ２ The surface-treated copper foil according to claim 1, wherein the amount of zinc deposited per unit [D / A] is 7 mg or less.

3. The surface-treated copper foil according to claim 1 or 2, comprising a silane coupling agent treatment layer on the chromate treatment layer.

4. A copper-clad laminate obtained by laminating the surface-treated copper foil according to claim 1 or 2 onto an insulating resin substrate.

5. A copper-clad laminate obtained by laminating the surface-treated copper foil described in claim 3 onto an insulating resin substrate.

6. The copper-clad laminate according to claim 4, wherein the insulating resin substrate is an adhesive layer and / or a surface-modified fluorine-containing insulating resin substrate.

7. A printed circuit board using the copper-clad laminate described in claim 4.

8. A printed circuit board using the copper-clad laminate according to claim 6.

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