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

Abstract

The present invention provides a surface-treated copper foil which is excellent in anchoring effect to an insulating resin substrate, can maintain high adhesion to a low dielectric constant resin substrate having a high molding temperature, can achieve high heat resistance, can suppress insertion loss to a very low level, and is therefore suitable for use in the production of a printed wiring board for high-frequency signal transmission using a low dielectric constant resin substrate having a molding temperature of 300°C or higher. A surface-treated copper foil has a roughening treatment layer on at least one side of an untreated copper foil, a heat-resistant treatment layer on the roughening treatment layer, and a chromate treatment layer on the heat-resistant treatment layer, wherein the roughening treatment layer is formed of copper particles having a primary particle diameter of 0.5 μm or more and 0.9 μm or less, the heat-resistant treatment layer is a heat-resistant treatment layer containing cobalt and molybdenum, and the glossiness Gs (85°) of the treatment surface of the chromate treatment layer is 60 or more and 80 or less.

Description

Technical Field

[0001] This invention relates to surface-treated copper foil. Specifically, the surface-treated copper foil relates to a surface-treated copper foil in which: because a roughening treatment layer is formed using copper particles with a primary particle size of 0.5 μm to 0.9 μm, it exhibits excellent anchoring effect on insulating resin substrates; furthermore, because a heat-resistant treatment layer containing cobalt and molybdenum is formed on the roughening treatment layer, and a chromate treatment layer containing chromium is formed on the heat-resistant treatment layer, the surface of the roughening treatment layer is not easily oxidized, and the copper particles are not easily deformed. Therefore, even with low-dielectric-constant resin substrates at high molding temperatures, high adhesion can be maintained, and high heat resistance can be achieved. Moreover, because the gloss Gs (85°) of the chromate treatment layer is 60 to 80 and copper particles are sparsely formed, insertion loss can be suppressed to a very low level. Therefore, it is suitable for the manufacture of printed circuit boards for high-frequency signal transmission using low-dielectric-constant resin substrates with molding temperatures of 300°C or higher. Background Technology

[0002] In Japan, 5G services began in March 2020, and although limited to certain locations in cities, high-speed communication is now available.

[0003] In addition, the use of Advanced Driver Assistance Systems (ADAS) has expanded beyond luxury cars to include light vehicles. For example, when driving at a constant speed on highways using constant speed control devices, the system can detect the approach of vehicles in front and automatically control the distance. Or, in urban areas, it can detect pedestrians, bicycles, etc., that suddenly appear and automatically apply the brakes. These technologies are becoming increasingly common and help reduce the burden on drivers and prevent traffic accidents.

[0004] Currently, 5G mostly uses the frequency band of 3.6GHz to less than 6GHz, which is called Sub6, but it is expected that the use of high-frequency bands above 28GHz, which is called millimeter wave, will also increase in the future.

[0005] In addition, the number of cars equipped with ADAS is expected to increase in the future. As the demand for millimeter-wave radar in the 24GHz to 79GHz frequency band, which is one of the sensors supporting ADAS, further increases, the requirements for millimeter-wave radar with higher performance are also becoming more and more stringent.

[0006] For communication systems using these high-frequency bands, it is required not only to transmit signals at high speed, but also to transmit with low loss.

[0007] Whether a signal can be transmitted with low loss is strongly influenced by the physical properties of the insulating resin substrate or copper foil that constitutes the printed wiring board or antenna, namely the dielectric properties or conductor resistance.

[0008] Typically, insertion loss is the sum of dielectric loss and conductor loss.

[0009] Dielectric loss is mainly caused by the insulating resin substrate. Due to the influence of dielectric properties, the insertion loss tends to increase when the dielectric constant or dielectric loss tangent becomes higher, and this tendency is more pronounced at high frequencies.

[0010] The conductor loss is mainly caused by the copper foil, and is affected not only by the surface roughness of the copper foil, but also by the type of dissimilar metal or the amount of dissimilar metal it is attached to. Therefore, if the surface roughness is large or a magnetic metal is used, the insertion loss tends to increase, and this tendency becomes more pronounced at high frequencies.

[0011] Therefore, in order to transmit signals at frequencies of approximately 30 GHz and above, known as millimeter waves, with low loss, the insulating resin substrate is preferably a material with excellent dielectric properties, and in particular, a low dielectric constant resin substrate composed of liquid crystal polymer resins or fluoropolymers with low permittivity and dielectric loss tangent is desirable.

[0012] In addition, copper foil with lower surface roughness and less magnetic metal adhesion is preferred, and many copper foils that significantly reduce the amount of micro-roughening treatment or dissimilar metal treatment have been proposed.

[0013] When using liquid crystal polymers or fluoropolymer substrates to fabricate copper-clad laminates, it is necessary to heat the temperature to a high temperature of over 300°C for molding. However, it is not possible to attach finely roughened copper foil or dissimilar metals with a particle size of less than submicron, or the amount of roughened copper foil attached is very small. The following problems exist: the surface of the roughened layer is prone to oxidation at high temperatures. In addition, the shape of the roughened particles is prone to change, and the physical anchoring effect is weak and cannot ensure sufficient adhesion.

[0014] Furthermore, even if the seal is high under normal conditions, significant deterioration can occur if long-term heat resistance tests are conducted.

[0015] Even when forming at temperatures above 300°C, if you want to suppress oxidation of the roughened layer surface or deformation of the roughened particles to ensure sufficient adhesion, you need to increase the amount of dissimilar metal or increase the size of the roughened particles.

[0016] However, if the amount of dissimilar metal processed is increased, or the coarsening particles are enlarged, there is a problem of increased insertion loss.

[0017] Therefore, it is desirable to develop a surface-treated copper foil that has sufficient adhesion and heat resistance to low dielectric constant resin substrates with molding temperatures above 300°C, thereby suppressing insertion loss during high-frequency signal transmission. This surface-treated copper foil can be used in printed wiring boards for high-frequency signal transmission that use low dielectric constant resin substrates.

[0018] Existing technical documents

[0019] Patent documents

[0020] Patent Document 1: Japanese Patent Application Publication No. 2015-147978.

[0021] Patent Document 2: Japanese Patent Application Publication No. 2021-098892. Summary of the Invention

[0022] The problem that the invention aims to solve

[0023] Patent Document 1 describes a surface-treated copper foil characterized in that, within a 30μm width length of the surface-treated copper foil cut in the width direction, there are one or more but less than five coarsened particles with a coarsening height of 1.5μm or more, and there are ten or more coarsened particles with a coarsening height of 1.0μm or less. According to the document, this surface-treated copper foil can also achieve high adhesion to low dielectric constant resin substrates with a molding temperature of 300°C or higher, and it also has excellent transmission characteristics as a copper foil for high-frequency circuits.

[0024] However, even if the coarsening height is below 1.0 μm, the insertion loss will increase if the number of coarsening particles is large.

[0025] Patent Document 2 describes a surface-treated copper foil characterized by comprising a surface-treated layer formed on at least one side of an untreated copper foil and an oxidation-preventing layer formed on the surface-treated layer. The surface-treated layer contains copper particles with an average particle size of about 10 nm to 100 nm, a ten-point average roughness Rz of about 0.2 μm to 0.5 μm, and a gloss Gs (60°) of about 200 or higher. The oxidation-preventing layer contains nickel and phosphorus. According to the description, this surface-treated copper foil has excellent adhesion strength to an insulating resin substrate, low insertion loss, and is excellent as a high-frequency foil.

[0026] However, for low dielectric constant resin substrates with molding temperatures above 300°C, copper particles are prone to deformation at high temperatures during molding, resulting in reduced adhesion to the resin substrate and reduced adhesion when exposed to high temperatures for extended periods after molding.

[0027] The inventors, taking the aforementioned problems as their technical objective, have repeatedly conducted numerous trials and evaluations, resulting in a surface-treated copper foil with the following characteristics: a roughening treatment layer is provided on at least one side of the untreated copper foil; a heat-resistant treatment layer is provided on the roughening treatment layer; and a chromate treatment layer is provided on the heat-resistant treatment layer. The roughening treatment layer is formed of copper particles with a primary particle size of 0.5 μm or more and 0.9 μm or less. The heat-resistant treatment layer is a heat-resistant treatment layer containing cobalt and molybdenum. As long as the gloss Gs (85°) of the surface treated by the chromate treatment layer is 60 or more and 80 or less, the surface-treated copper foil exhibits high adhesion even to low dielectric constant resin substrates with molding temperatures of 300°C or higher. Furthermore, it can maintain high adhesion without practical problems even when exposed to high temperatures for extended periods. Moreover, it can utilize the excellent transmission characteristics of the low dielectric constant resin substrate to achieve low conductor loss, thereby realizing the aforementioned technical objective.

[0028] Technical solutions for solving the problem

[0029] The technical issues mentioned below can be solved by the present invention.

[0030] This invention relates to a surface-treated copper foil, wherein at least one side of the untreated copper foil has a roughening treatment layer, a heat-resistant treatment layer is provided on the roughening treatment layer, and a chromate treatment layer is provided on the heat-resistant treatment layer. The roughening treatment layer is formed of copper particles with a primary particle size of 0.5 μm or more and 0.9 μm or less, the heat-resistant treatment layer is a heat-resistant treatment layer containing cobalt and molybdenum, and the gloss Gs (85°) of the treated surface of the chromate treatment layer is 60 or more and 80 or less.

[0031] In addition, the present invention provides a surface-treated copper foil in which the arithmetic mean height Sa of each treated surface of the roughening treatment layer, the heat-resistant treatment layer and the chromate treatment layer is 0.08 μm or more and 0.16 μm or less.

[0032] In addition, the present invention is a surface-treated copper foil having a silane coupling agent treatment layer on the chromate treatment layer.

[0033] In addition, the present invention is a copper-clad laminate formed by laminating the surface-treated copper foil onto an insulating resin substrate.

[0034] In addition, the present invention is a copper-clad laminate in which the insulating resin substrate is a low dielectric constant resin substrate.

[0035] In addition, the present invention is a printed wiring board using the copper-clad laminate.

[0036] Invention Effects

[0037] Because the roughening layer on the surface-treated copper foil of the present invention is formed by relatively large copper particles with a primary particle size of 0.5 μm to 0.9 μm, it is a surface-treated copper foil with excellent anchoring effect on insulating resin substrates.

[0038] Furthermore, since the heat-resistant treatment layer contains cobalt and molybdenum, and the chromate treatment layer contains chromium, the surface of the roughened treatment layer is not easily oxidized even at high temperatures, and the copper particles are not easily deformed. Therefore, it is a surface-treated copper foil that can maintain high adhesion and excellent heat resistance even for low dielectric constant resin substrates with molding temperatures above 300°C.

[0039] Furthermore, since the gloss Gs (85°) of the chromate-treated surface is relatively high, ranging from 60 to 80, and the copper particles are sparsely formed, it is a surface-treated copper foil that can suppress insertion loss very low.

[0040] Furthermore, as long as the arithmetic mean height Sa of each treated surface of the roughening layer, the heat-resistant layer, and the chromate treatment layer is 0.08 μm to 0.16 μm, it becomes a surface-treated copper foil that can further suppress insertion loss.

[0041] In addition, as long as a silane coupling agent treatment layer is provided on the chromate treatment layer, it becomes a surface-treated copper foil with better adhesion or heat resistance.

[0042] Therefore, the surface-treated copper foil of the present invention can be used in the manufacture of printed wiring boards for high-frequency signal transmission using low dielectric constant resin substrates with a molding temperature of 300°C or higher. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the surface-treated copper foil of the present invention.

[0044] Figure 2 This is a scanning electron microscope image (10,000x) of the surface-treated copper foil of the present invention (Example 1). Detailed Implementation

[0045] The present invention is a surface-treated copper foil having a roughening treatment layer on at least one side of the untreated copper foil, a heat-resistant treatment layer on the roughening treatment layer, and a chromate treatment layer on the heat-resistant treatment layer.

[0046] <Untreated copper foil>

[0047] The copper foil before surface treatment in this invention (hereinafter referred to as "untreated copper foil") is not particularly limited, and any type of copper foil with no distinction between the front and back, such as rolled copper foil or electrolytic copper foil, or copper foil with a distinction between the front and back, can be used.

[0048] There are no particular restrictions on the surface to be treated; any side of the rolled copper foil can be used, and any side of the electrolytic copper foil can be either the precipitated surface or the drum surface.

[0049] Regarding the surface to which surface treatment is performed, it is preferable that the gloss Gs(60°) at 60 degrees of specular gloss, as measured by JIS Z8471, is 500 or higher.

[0050] When using rolled copper foil, it is preferable to immerse it in a hydrocarbon-based organic solvent or an alkaline degreasing solution, and then perform surface treatment after removing the rolling oil.

[0051] When using electrolytic copper foil, it is preferable to immerse it in dilute sulfuric acid and then perform surface treatment after removing the oxide film.

[0052] There is no particular limitation on the thickness of the untreated copper foil, as long as it is thick enough to be used for printing wiring boards after surface treatment. Preferably, it is 6μm to 300μm, and more preferably, it is 12μm to 35μm.

[0053] <Roughening layer>

[0054] The surface-treated copper foil of the present invention has a roughening treatment layer on the untreated copper foil, in which copper particles are used as roughening particles.

[0055] The primary particle size of the copper particles is preferably 0.5 μm to 0.9 μm, more preferably 0.6 μm to 0.8 μm.

[0056] In this invention, the lower limit of the primary particle size is set to 0.5 μm, but the presence of copper particles smaller than 0.5 μm is not excluded.

[0057] However, when there are many particles with a single particle size of less than 0.5 μm, the surface of the roughening layer may oxidize or the copper particles may deform during bonding with a low dielectric constant resin substrate with a molding temperature of 300°C or higher. As a result, the anchoring effect on the low dielectric constant resin substrate is reduced, and the adhesion or heat resistance may be significantly reduced.

[0058] In addition, when there are many particles with a diameter exceeding 0.9 μm, the surface roughness increases, and the conductor loss may increase.

[0059] The primary particle size can be determined by selecting 10 copper particles observed with a scanning electron microscope at a tilt angle of 0° and a magnification of 10,000, measuring the maximum length of each copper particle, and averaging the results.

[0060] The roughening layer in this invention can be formed by electroplating the copper particle layer after forming a copper particle layer on an untreated copper foil.

[0061] The copper particle layer can be formed as follows: An aqueous solution at 40°C containing 20 g / L–110 g / L copper sulfate pentahydrate, 45 g / L–150 g / L sulfuric acid, 4 mg / L–60 mg / L tungsten ions, and 225 mg / L–1200 mg / L titanium ions is used as the electrolyte. An insoluble titanium electrode coated with platinum group oxides is immersed in the electrolyte as the anode. Untreated copper foil is immersed on the opposite side as the cathode at a certain interval, and a current density of 10 A / dm³ is applied. 2 ~40A / dm 2 20C / dm of electricity 2 ~100C / dm 2 Electrolysis is carried out.

[0062] Regarding copper plating, an aqueous solution at 40°C containing 150 g / L to 300 g / L copper sulfate pentahydrate and 50 g / L to 400 g / L sulfuric acid is used as the electrolyte. A platinum group oxide-coated titanium insoluble electrode is immersed in the electrolyte as the anode. Additionally, a copper foil with a copper particle layer is immersed on the opposite side as the cathode at a certain interval, and a current density of 2 A / dm² is applied. 2 ~10A / dm 2 60C / dm 2 ~240C / dm 2 Electrolysis can be performed.

[0063] <Heat-resistant treatment layer and chromate treatment layer>

[0064] The present invention is a surface-treated copper foil having a heat-resistant treatment layer containing cobalt and molybdenum on a roughening treatment layer, and a chromate treatment layer containing chromium on the heat-resistant treatment layer.

[0065] This is because if a heat-resistant treatment layer or a chromate treatment layer is not formed, the adhesion to the low-dielectric-constant resin substrate may be significantly reduced if the laminate is exposed to a high temperature above 150°C after being bonded to a low-dielectric-constant resin substrate.

[0066] The heat-resistant treatment layer can be formed by immersing a copper foil with a roughening treatment layer formed on an untreated copper foil in an electrolyte while electrolyzing it.

[0067] Regarding the electrolyte for forming the heat-resistant treatment layer, it is preferable to prepare an electrolyte with pH 4 to pH 10 by adjusting an aqueous solution containing 20 g / L to 70 g / L of cobalt compound, 10 g / L to 50 g / L of molybdenum compound and 10 g / L to 100 g / L of sodium citrate dihydrate.

[0068] Regarding electrolysis, it is preferable to immerse an insoluble electrode such as titanium coated with platinum group oxide as the anode in the electrolyte. Additionally, a copper foil with a roughened layer is immersed on the opposite side as the cathode at a certain interval, at a current density of 3 A / dm². 2 ~14A / dm 2 7C / dm of electricity 2 ~30C / dm 2 The electrolysis is carried out under conditions where the liquid temperature is between 25℃ and 45℃.

[0069] There are no particular limitations on cobalt-containing compounds, examples of which include cobalt sulfate heptahydrate and cobalt dichloride hexahydrate.

[0070] There are no particular limitations on molybdenum-containing compounds; an example is sodium molybdate dihydrate.

[0071] The chromate treatment layer can be formed by electrolyzing a copper foil with a heat-resistant treatment layer while immersing it in an electrolyte.

[0072] Regarding the electrolyte for forming the chromate treatment layer, it is preferable to use sulfuric acid or sodium hydroxide to prepare an aqueous solution containing 10 g / L to 60 g / L of chromium compounds, or an aqueous solution containing 10 g / L to 60 g / L of chromium compounds and 0.2 g / L to 4.0 g / L of zinc ions, to obtain an electrolyte with a pH of 2 to 12.

[0073] Regarding electrolysis, it is preferable to use an insoluble electrode such as titanium coated with platinum group oxide as the anode, immersed in the electrolyte. Additionally, copper foil with a heat-resistant treatment layer is immersed on the opposite side as the cathode at a certain interval, and the current density is 0.5 A / dm³. 2 ~5A / dm 2 1C / dm 2 ~6C / dm 2 The electrolysis is carried out under conditions where the liquid temperature is between 25℃ and 50℃.

[0074] There are no particular limitations on chromium-containing compounds; for example, sodium dichromate.

[0075] There are no particular restrictions on the zinc ion source; zinc oxide is an example.

[0076] <Gloss>

[0077] The present invention relates to a surface-treated copper foil with a gloss level (Gs) (85°) of 60 to 80 on the treated surface of the chromate-treated layer.

[0078] This is because if the gloss level is less than 60, the number of copper particles becomes too large, resulting in increased conductor loss; if it exceeds 80, the number of copper particles becomes too small, potentially leading to insufficient adhesion or heat resistance to low dielectric constant resin substrates.

[0079] Regarding Gs(85°), the 85-degree specular gloss can be determined based on JIS Z8741.

[0080] <Surface Roughness>

[0081] The arithmetic mean height Sa of each treated surface of the roughening treatment layer, the heat-resistant treatment layer and the chromate treatment layer of the surface-treated copper foil of the present invention is preferably 0.08 μm to 0.16 μm, more preferably 0.09 μm to 0.15 μm.

[0082] This is because if the arithmetic mean height Sa is less than 0.08 μm, it may not provide sufficient adhesion or heat resistance to low dielectric constant resin substrates. In addition, if it exceeds 0.16 μm, conductor loss may increase.

[0083] <Silane Coupling Agent Treatment Layer>

[0084] Regarding the surface-treated copper foil of the present invention, a silane coupling agent treatment layer may be provided on the chromate treatment layer.

[0085] By forming a silane coupling agent treatment layer on the chromate treatment layer, a surface-treated copper foil with excellent adhesion or heat resistance is further obtained.

[0086] Regarding the silane coupling agent treatment layer, it can be formed by immersing the copper foil with the chromate treatment layer in an aqueous solution of silane coupling agent prepared at a liquid temperature of 20℃~50℃, or by spreading it by spraying or other methods and then washing it with water.

[0087] There are no particular limitations on the silane coupling agent used for the silane coupling agent layer. Silane coupling agents containing vinyl, epoxy, styrene, methacryl, acryloyl, amino, urea, and mercapto groups can be used. However, silane coupling agents containing amino, epoxy, or vinyl groups have excellent moisture resistance and rust prevention properties, and are therefore more suitable for use.

[0088] Regarding silane coupling agents, one type can be used, or two or more types can be used in combination.

[0089] Examples of the composition and conditions for the aqueous solution used to form the silane coupling agent treatment layer include γ-aminopropyltriethoxysilane at a concentration of 1 mL / L to 5 mL / L, a liquid temperature of 25°C to 35°C, and an immersion time of 15 seconds.

[0090] <Insulating Resin Substrate>

[0091] The insulating resin substrate used in the copper-clad laminate of the present invention is not particularly limited, but examples include epoxy resin substrate or polyimide resin substrate. In addition, examples of low dielectric constant resin substrates include polyphenylene ether resin substrate, bismaleimide triazine resin substrate, and cycloolefin polymer resin substrate.

[0092] In addition, the surface-treated copper foil of the present invention can also be applied to low dielectric constant resin substrates with a molding temperature of 300°C or higher.

[0093] Examples of low dielectric constant resin substrates with molding temperatures of 300°C or higher include liquid crystal polymer resin substrates and fluorinated resin substrates.

[0094] Example

[0095] The following are embodiments of the present invention, but the present invention is not limited thereto.

[0096] <Untreated copper foil>

[0097] As examples and comparative examples, untreated copper foil with a nominal thickness of 18 μm and a gloss level of Gs(60°) of 500 or higher was used.

[0098] Electrolytic copper foil is immersed in dilute sulfuric acid to remove the oxide film, and then undergoes various treatments.

[0099] (Example 1)

[0100] <Formation of the roughening layer>

[0101] As the electrolyte, an aqueous solution containing 47 g / L copper sulfate pentahydrate, 95 g / L sulfuric acid, 15 mg / L tungsten ions, and 500 mg / L titanium ions at a temperature of 40°C was used. An insoluble titanium electrode coated with platinum group oxides was immersed in the electrolyte as the anode. Meanwhile, untreated copper foil was immersed on the opposite side as the cathode at a certain interval, with a current density of 25 A / dm³. 2 50C / dm of electricity 2 Electrolysis is performed to form a layer of copper particles on the untreated copper foil. The resulting copper particle layer is dendritic.

[0102] As the electrolyte, an aqueous solution containing 220 g / L copper sulfate pentahydrate and 110 g / L sulfuric acid at a temperature of 40°C was used. An insoluble titanium electrode coated with platinum group oxides was immersed in the electrolyte as the anode. Meanwhile, a freshly fabricated copper foil with a copper particle layer was immersed on the opposite side as the cathode at a certain interval, and a current density of 10 A / dm² was applied. 2 120C / dm 2 Electrolysis is performed to form a roughening layer by plating copper onto the copper particle layer.

[0103] <Formation of the heat-resistant treatment layer>

[0104] As the electrolyte, an electrolyte prepared by adjusting an aqueous solution containing 39 g / L cobalt sulfate heptahydrate, 24 g / L sodium molybdate dihydrate, and 45 g / L sodium citrate dihydrate to pH 5.6 was used.

[0105] Regarding electrolysis, an insoluble titanium electrode coated with platinum group oxides is immersed in the electrolyte as the anode. Additionally, a copper foil with a roughened layer is immersed on the opposite side as the cathode at a certain interval, and the current density is 7 A / dm². 2 14C / dm 2 The process is carried out under electrolysis conditions at a liquid temperature of 30°C to form a heat-resistant treatment layer.

[0106] <Chromate-treated layer>

[0107] As the electrolyte, an electrolyte prepared by adjusting an aqueous solution containing 12.5 g / L sodium dichromate and 2.5 g / L zinc ions to pH 12 is used.

[0108] Regarding electrolysis, an insoluble titanium electrode coated with platinum group oxides is immersed in the electrolyte as the anode. Additionally, copper foil with a heat-resistant coating is immersed on the opposite side as the cathode at a certain interval, at a current density of 2 A / dm². 2 10C / dm 2 The electrolysis is carried out under an electrolysis temperature of 25°C to create a chromate treatment layer.

[0109] <Silane Coupling Agent Treatment Layer>

[0110] The copper foil with the chromate treatment layer formed thereon is immersed in an aqueous solution containing 5 ml / L of γ-aminopropyltriethoxysilane at a liquid temperature of 25°C for 10 seconds, then lifted out and dried to form a silane coupling agent treatment layer, thereby obtaining a surface-treated copper foil. Figure 2 ).

[0111] (Example 2)

[0112] In addition to setting the electrolysis conditions for forming the first stage of copper particle layer to a current density of 22 A / dm³, 2 55C / dm of electricity 2 In addition, the roughening treatment layer was formed under the same conditions as in Example 1.

[0113] (Example 3)

[0114] In addition to setting the electrolysis conditions for forming the first stage of copper particle layers to a current density of 23 A / dm³, 2 52C / dm 2 Furthermore, except for the silane coupling agent treatment layer, the conditions for forming the roughening treatment layer are the same as those in Example 1.

[0115] (Comparative Example 1)

[0116] In addition to setting the electrolysis conditions for forming the first stage of copper particle layer to a current density of 16 A / dm³ 2 40C / dm of electricity2 In addition, the roughening treatment layer was formed under the same conditions as in Example 1.

[0117] (Comparative Example 2)

[0118] In addition to setting the electrolysis conditions for forming the first stage of copper particle layer to a current density of 24 A / dm³ 2 60C / dm 2 In addition, the roughening treatment layer was formed under the same conditions as in Example 1.

[0119] (Comparative Example 3)

[0120] As the electrolyte for forming the first-stage copper particle layer, an aqueous solution at 40°C was used, containing 57 g / L copper sulfate pentahydrate, 100 g / L sulfuric acid, 15 mg / L tungsten ions, and 35 mg / L chloride ions. The electrolysis conditions were set to a current density of 50 A / dm³. 2 125C / dm 2 Furthermore, the electrolytic conditions for copper plating on the copper particle layer in the second stage are set to a current density of 5 A / dm³. 2 440C / dm 2 In addition, the roughening treatment layer was formed under the same conditions as in Example 1.

[0121] (Comparative Example 4)

[0122] As the electrolyte for forming the first-stage copper particle layer, an aqueous solution at 40°C was used, containing 100 g / L copper sulfate pentahydrate, 100 g / L sulfuric acid, 150 mg / L indium sulfate, and 5 g / L starch decomposition product. The electrolysis conditions were set to a current density of 50 A / dm³. 2 130C / dm 2 Furthermore, no copper plating is performed; except for the same conditions as in Example 1, the roughening treatment layer is formed under the same conditions.

[0123] (Comparative Example 5)

[0124] The electrolysis conditions for forming the first stage of the copper particle layer were set to a current density of 22 A / dm³. 2 55C / dm of electricity 2 Furthermore, no heat-resistant treatment layer is formed. Otherwise, the roughening treatment layer is formed under the same conditions as in Example 1.

[0125] (Comparative Example 6)

[0126] The electrolysis conditions for forming the first stage of the copper particle layer were set to a current density of 22 A / dm³. 2 55C / dm of electricity 2Furthermore, the formation conditions for the heat-resistant treatment layer are set as follows: using an electrolyte prepared by adjusting the pH of an aqueous solution containing 30 g / L nickel sulfate hexahydrate, 2 g / L sodium phosphate monohydrate, and 10 g / L sodium acetate trihydrate to pH 4.5 with sulfuric acid, and setting the electrolysis conditions to a current density of 5 A / dm³. 2 10C / dm 2 The liquid temperature was 30°C. Otherwise, the roughening treatment layer was formed under the same conditions as in Example 1.

[0127] (Comparative Example 7)

[0128] The electrolysis conditions for forming the first stage of the copper particle layer were set to a current density of 23 A / dm³. 2 52C / dm 2 It does not have a chromate treatment layer, except that the roughening treatment layer is formed under the same conditions as in Example 1.

[0129] (Comparative Example 8)

[0130] The electrolysis conditions for forming the first stage of the copper particle layer were set to a current density of 23 A / dm³. 2 52C / dm 2 It does not have a chromate treatment layer and a silane coupling agent treatment layer. Otherwise, the roughening treatment layer is formed under the same conditions as in Example 1.

[0131] The processing conditions for each surface-treated copper foil in the examples and comparative examples are shown in [Table 1].

[0132] [Table 1]

[0133]

[0134] <Fabrication of Copper-Clad Laminate A>

[0135] The treated surfaces of the copper foils in the examples and comparative examples were used as the bonding surfaces, and were bonded to one or both sides of a fluoropolymer substrate (ROGERS CORPORATION / RO3003 / nominal thickness 100μm). A vacuum hot press (Kitagawa Seiki Co., Ltd. / KVHC-II) was used to heat and pressurize the substrate under vacuum at a temperature of 370°C and a surface pressure of 3MPa for 45 minutes to obtain copper-clad laminate A.

[0136] <Fabrication of Copper-Clad Laminate B>

[0137] The treated surfaces of the copper foils in the examples and comparative examples were used as the bonding surfaces, and were bonded to one or both sides of a liquid crystal polymer resin substrate (Kuraray Co., Ltd. / CTQ-50 / nominal thickness 50μm). A vacuum hot press (Kitagawa Seiki Co., Ltd. / KVHC-II) was used to heat and pressurize the substrate under vacuum at a temperature of 300°C and a surface pressure of 4MPa for 10 minutes to obtain copper-clad laminate B.

[0138] The surface-treated copper foil is evaluated using the following method.

[0139] <Determination of primary particle size>

[0140] Using a scanning electron microscope (SEM) (JSM-6010LA, manufactured by Nippon Electron Ltd.), the surface with the roughened layer was observed at a tilt angle of 0° and a magnification of 10,000. Based on the obtained SEM image, the maximum length of each of the 10 copper particles was measured and averaged to obtain the primary particle size.

[0141] <Measurement of Gloss>

[0142] Regarding the gloss of the treated surface, it was determined by measuring the 85-degree specular gloss (Gs(85°)) using a gloss meter (KONICA MINOLTA Co., Ltd. / GM-268A) based on JIS Z8741.

[0143] <Surface Roughness Measurement>

[0144] Using a confocal microscope, i.e. a laser microscope (manufactured by Olympus Corporation / LEXT OLS5000) in accordance with ISO25178-607, the arithmetic mean height Sa was measured according to JPCA-KHS01 (2021) with the evaluation area set to 125μm×125μm, the S filter set to 0.5μm, the L filter set to 50μm, and the F operation set to multi-surface (3rd order).

[0145] <Normal peel strength>

[0146] For the copper-clad laminate A produced above, an etching apparatus (Ninomiya Corporation / SPE-40) was used to form a copper circuit with a width of 10 mm, thereby producing a test piece.

[0147] According to JIS C6481, the peel strength is determined using a universal testing machine. A peel strength of 0.53 kN / m or higher is rated as “0”, and a peel strength of less than 0.53 kN / m is rated as “×”.

[0148] <Peel strength after heat treatment>

[0149] For the test piece obtained by forming a 10mm wide circuit on the copper-clad laminate A made above, a thermostat was used to heat it at 177°C in an atmospheric atmosphere for 5 days to obtain the test piece.

[0150] According to JIS C6481, the peel strength after heat treatment is determined using a universal testing machine. A peel strength of 0.53 kN / m or higher is rated as “0”, and a peel strength of less than 0.53 kN / m is rated as “×”.

[0151] <Transmission Characteristics>

[0152] For the copper-clad laminate B obtained above, a single-ended microwave transmission band circuit was formed using an etching apparatus (manufactured by Ninomiya Systems Co., Ltd. / SPE-40) as a test piece.

[0153] For the test piece, set the circuit length to 100mm and the circuit width to a characteristic impedance of 50Ω.

[0154] For the test piece, the insertion loss (S21) at a frequency of 20 GHz was measured using a network analyzer (KEYSIGHT TECHNOLOGIES, INC. / E5071C). A value above -4.4 dB / 100 mm was rated as "0", and a value below -4.4 dB / 100 mm was rated as "×".

[0155] <Overall Evaluation>

[0156] The evaluations of the peel strength under normal conditions and the peel strength and transmission characteristics after heat treatment are combined. The test in which any evaluation is 0 is evaluated as "0", and the test in which more than one evaluation is "×" is evaluated as "×".

[0157] The results of the adhesion, heat resistance and transport characteristics of the surface-treated copper foils of the Examples and Comparative Examples are shown in [Table 2].

[0158] [Table 2]

[0159]

[0160] As shown in Examples 1-3, the surface-treated copper foil of the present invention has a peel strength of 0.53 kN / m or higher under normal conditions and after heat treatment, which is a relatively high value that is not a problem in practical use. Even at a high frequency of 20 GHz, the insertion loss S21 is -4.4 dB / 100 mm or higher, which has good transmission characteristics.

[0161] Industrial availability

[0162] The surface-treated copper foil of the present invention is as follows: since a roughening treatment layer is formed using copper particles with a primary particle size of 0.5 μm to 0.9 μm, it exhibits excellent anchoring effect on insulating resin substrates. In addition, since a heat-resistant treatment layer containing cobalt and molybdenum is formed on the roughening treatment layer, and a chromate treatment layer containing chromium is formed on the heat-resistant treatment layer, the surface of the roughening treatment layer is not easily oxidized, and the copper particles are not easily deformed. Therefore, it can maintain high adhesion and achieve high heat resistance even for low dielectric constant resin substrates with high molding temperatures. Furthermore, since the gloss Gs (85°) of the chromate treatment layer is 60 to 80 and the copper particles are sparsely formed, insertion loss can be suppressed to a low level. Therefore, it can be used in the manufacture of printed wiring boards for high-frequency signal transmission using low dielectric constant resin substrates with molding temperatures of 300°C or higher.

[0163] Therefore, this invention is highly industrially applicable.

Claims

1. A surface-treated copper foil, comprising a roughening layer on at least one side of an untreated copper foil, a heat-resistant treatment layer on the roughening layer, and a chromate treatment layer on the heat-resistant treatment layer, wherein, The roughening layer is formed of copper particles with a primary particle size of 0.5 μm or larger and 0.9 μm or smaller. The heat-resistant layer is a heat-resistant layer containing cobalt and molybdenum. The gloss (Gs 85°) of the treated surface of the chromate treatment layer is 60 or larger and 80 or smaller. The primary particle size is determined by selecting 10 copper particles observed using a scanning electron microscope at a tilt angle of 0° and a magnification of 10,000, measuring the maximum length of each copper particle, and averaging the results.

2. The surface-treated copper foil according to claim 1, wherein, The arithmetic mean height Sa of each treated surface of the roughening layer, the heat-resistant layer, and the chromate treatment layer is greater than 0.08 μm and less than 0.16 μm.

3. The surface-treated copper foil according to claim 1 or 2, wherein, A silane coupling agent treatment layer is provided on the chromate treatment layer.

4. A copper-clad laminate, wherein, It is formed by bonding the treated surface of the surface-treated copper foil as described in claim 1 or 2 to an insulating resin substrate.

5. The copper-clad laminate according to claim 4, wherein, The insulating resin substrate is an insulating resin substrate selected from epoxy resin substrates, polyimide resin substrates, polyphenylene ether resin substrates, bismaleimide triazine resin substrates, cyclic olefin polymer resin substrates, liquid crystal polymer resin substrates, and fluorinated resin substrates.

6. A printed wiring board, wherein, It uses the copper-clad laminate as described in claim 4.

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