TWI882751B - Manufacturing method of surface treated copper foil, copper clad laminate and printed wiring board - Google Patents

Abstract

The surface treated copper foil 1 of the present invention comprises a copper foil 2 and a surface treated layer 3 formed on at least one side of the copper foil 2. The surface treated layer 3 contains Ni, Zn and Cr. In the surface treated layer 3, the Zn adhesion amount is 100-500 μg/dm ² , the Cr adhesion amount is 70-150 μg/dm ² , and the ratio of the Cr adhesion amount to the total of the Ni adhesion amount, the Zn adhesion amount and the Cr adhesion amount is 18.0-50.0%.

Description

Manufacturing method of surface treated copper foil, copper clad laminate and printed wiring board

The present invention relates to a method for manufacturing a surface treated copper foil, a copper clad laminate and a printed wiring board.

Copper clad laminates are manufactured by laminating copper foil to a base material made of resin or the like. Copper clad laminates are widely used in various applications such as flexible printed wiring boards. Flexible printed wiring boards are manufactured by etching the copper foil of copper clad laminates to form a circuit pattern (also called a "conductor pattern"), and connecting and mounting electronic components on the circuit pattern using solder. Regarding the circuit pattern, before mounting electronic components, unnecessary substances are removed from the surface of the copper foil, or soft etching is performed to roughen the surface of the copper foil.

The surface of the copper foil used for the copper-clad laminate is controlled in elements and/or shape to meet the required characteristics. For example, Patent Document 1 discloses a surface-treated copper foil having excellent adhesion to resin, chemical resistance and heat resistance, and being less likely to leave etching residues. The surface-treated copper foil comprises a copper foil and a surface-treated layer (Zn-Ni-Mo layer), which is disposed on at least one side of the copper foil, and the amount of Zn, Ni and Mo attached is controlled. [Prior Art Document] [Patent Document]

[Patent Document 1] International Publication No. 2019/188837

[The problem that the invention wants to solve]

The surface treated copper foil described in Patent Document 1 sometimes produces undercuts during soft etching, which reduces the reliability of the circuit pattern (for example, the adhesion strength between the substrate and the circuit pattern is reduced). The embodiment of the present invention is completed to solve the above-mentioned problems, and its purpose is to provide a surface treated copper foil and copper clad laminate that can suppress undercuts during soft etching in one embodiment. In addition, the purpose of the embodiment of the present invention is to provide a method for manufacturing a printed wiring board having a circuit pattern with suppressed undercuts in another embodiment. [Technical means for solving the problem]

After intensive research on surface-treated copper foil, the inventors of the present invention found that the above-mentioned problem can be solved by forming a surface-treated layer containing Ni, Zn and Cr on at least one side of the copper foil, and controlling the ratio of the Zn attachment amount and the Cr attachment amount together with the total of the Cr attachment amount to the Ni attachment amount, the Zn attachment amount and the Cr attachment amount within a specified range, thereby completing the implementation form of the present invention.

That is, an embodiment of the present invention, in one aspect, relates to a surface-treated copper foil, comprising a copper foil and a surface-treated layer formed on at least one side of the copper foil, wherein the surface-treated layer contains Ni, Zn and Cr, wherein the amount of Zn deposited in the surface-treated layer is 100 to 500 μg/dm ² , the amount of Cr deposited is 70 to 150 μg/dm ² , and the ratio of the amount of Cr deposited to the total amount of Ni deposited, the amount of Zn deposited and the amount of Cr deposited is 18.0 to 50.0%.

In another embodiment of the present invention, there is provided a copper-clad laminate having the surface-treated copper foil and a substrate disposed on the surface-treated layer of the surface-treated copper foil.

Furthermore, the present invention is implemented in another aspect in a method for manufacturing a printed wiring board, which comprises etching the surface-treated copper foil of the copper-clad laminate to form a circuit pattern and then performing soft etching. [Effect of the invention]

According to an embodiment of the present invention, a surface treated copper foil and a copper clad laminate capable of suppressing undercutting during soft etching can be provided in one embodiment. In addition, according to an embodiment of the present invention, a method for manufacturing a printed wiring board having a circuit pattern with suppressed undercutting can be provided in another embodiment.

The following specifically describes the appropriate implementation forms of the present invention, but the present invention should not be limited to these. As long as it does not deviate from the main purpose of the present invention, various changes and improvements can be made based on the knowledge of the industry. The multiple components disclosed in the following implementation forms can form various inventions through appropriate combinations. For example, some components can be deleted from all the components shown in the following implementation forms, and the components of different implementation forms can also be appropriately combined.

The surface treated copper foil of the embodiment of the present invention comprises a copper foil and a surface treated layer formed on at least one side of the copper foil, wherein the surface treated layer contains Ni, Zn and Cr, wherein the amount of Zn deposited in the surface treated layer is 100 to 500 μg/dm ² , the amount of Cr deposited is 70 to 150 μg/dm ² , and the ratio of the amount of Cr deposited to the total amount of Ni deposited, the amount of Zn deposited and the amount of Cr deposited is 18.0 to 50.0%. The surface treated copper foil of the embodiment of the present invention can suppress undercutting during soft etching by being configured in this way.

Furthermore, the copper-clad laminate of the embodiment of the present invention comprises the surface-treated copper foil and a substrate disposed on the surface-treated layer of the surface-treated copper foil. The copper-clad laminate of the embodiment of the present invention is configured in this way to suppress undercutting during soft etching after etching the surface-treated copper foil to form a circuit pattern.

FIG1 is a cross-sectional view showing an example of a copper-clad laminate having a surface-treated copper foil in an embodiment of the present invention. As shown in FIG1 , the surface-treated copper foil 1 has a copper foil 2 and a surface-treated layer 3 formed on at least one side of the copper foil 2. In addition, the copper-clad laminate 10 has a surface-treated copper foil 1 and a substrate 11 disposed on the surface-treated layer 3 of the surface-treated copper foil 1.

FIG. 2 is a cross-sectional view showing an example of a state in which a circuit pattern is formed by etching the surface-treated copper foil of a copper-clad laminate having a surface-treated copper foil in an embodiment of the present invention and then soft-etching. As shown in FIG. 2, in the circuit pattern 20 formed using the copper-clad laminate having a surface-treated copper foil in an embodiment of the present invention, the surface-treated layer 3 in contact with the substrate 11 is not excessively etched and removed compared to the copper foil 2, and the generation of undercut can be suppressed.

FIG3 is a cross-sectional view showing an example of a state in which a circuit pattern is formed by etching the surface treated copper foil of a copper-clad laminate having a conventional surface treated copper foil and then soft etching is performed. As shown in FIG3, in the circuit pattern 30 formed using the copper-clad laminate having a conventional surface treated copper foil, the surface treated layer 4 in contact with the substrate 11 is excessively etched and removed compared to the copper foil 2, and undercut 40 is easily generated.

The surface treatment layer 3 used for surface treatment of the copper foil 1 may be formed on only one side of the copper foil 2 or on both sides of the copper foil 2. When the surface treatment layer 3 is formed on both sides of the copper foil 2, the types of the surface treatment layer 3 may be the same or different.

The surface treatment layer 3 contains Ni, Zn and Cr. In addition, the surface treatment layer 3 may further contain Co or may not contain Co. Among the various elements contained in the surface treatment layer 3, in order to suppress undercutting during soft etching, it is important to control the Zn attachment amount to 100-500 μg/dm ² , the Cr attachment amount to 70-150 μg/dm ² , and the ratio of the Cr attachment amount to the total of the Ni attachment amount, the Zn attachment amount and the Cr attachment amount (hereinafter referred to as "Cr ratio") to 18.0-50.0%. In addition, by controlling the Zn attachment amount within this range, the surface treatment layer 3 can be given characteristics such as heat resistance and chemical resistance; and by controlling the Cr attachment amount within this range, a rust-proof effect can also be given. From the viewpoint of stably ensuring the effect of suppressing undercut during soft etching, the Zn deposition amount is preferably 151 to 394 μg/dm ² , more preferably 151 to 331 μg/dm ² . From the same viewpoint, the Cr deposition amount is preferably 98 to 120 μg/dm ² , more preferably 98 to 107 μg/dm ² . From the same viewpoint, the Cr ratio is preferably 20.0 to 40.0%, more preferably 20.5 to 35.5%.

The Ni deposition amount in the surface treatment layer 3 is not particularly limited, but is preferably 10 to 100 μm/dm ² , and more preferably 27 to 72 μm/dm ² . By controlling the Ni deposition amount within such a range, the effect of suppressing undercut during soft etching can be enhanced.

Ni is a component that is difficult to dissolve in the soft etching solution used for soft etching, while Zn is a component that is easily soluble. Therefore, by controlling the balance of the Ni and Zn attachment amounts in the surface treatment layer 3 within an appropriate range, the effect of suppressing undercutting during soft etching can be improved. From the viewpoint of obtaining this effect, in the surface treatment layer 3, the ratio of the Ni attachment amount to the total of the Ni attachment amount and the Zn attachment amount is preferably 10.0 to 20.0%, and more preferably 15.2 to 18.2%. In addition, from the same viewpoint, in the surface treatment layer 3, the total of the Ni attachment amount and the Zn attachment amount is preferably 100 μg/dm ² or more and less than 500 μg/dm ² , and more preferably 178 to 466 μg/dm ² . Here, the soft etching solution used for soft etching is not particularly limited, and any known soft etching solution in the technical field can be used. A typical soft etching solution contains hydrogen peroxide and sulfuric acid as main components.

When the surface treatment layer 3 contains Co, the amount of Co deposited in the surface treatment layer 3 is preferably 100 μg/dm ² or less, and more preferably 80 μg/dm ² or less. By controlling the amount of Co deposited within this range, the effect of suppressing undercutting during soft etching can be ensured. In addition, since Co is a magnetic metal, by controlling the amount of Co deposited within this range, a surface-treated copper foil 1 capable of manufacturing a printed wiring board with excellent high-frequency characteristics can be obtained. In addition, the lower limit of the amount of Co deposited is not particularly limited, and is typically 0.1 μg/dm ² , and preferably 0.5 μg/dm ² .

The amount of Zn, Ni and Co (when present) in the surface treatment layer 3 can be measured by dissolving the surface treated copper foil 1 in a nitric acid aqueous solution mixed in a volume ratio of nitric acid: water = 1:2, and then measuring it by ICP analysis. The measurement can be performed using an inductively coupled plasma emission spectrometer (SPS3520UV manufactured by Hitachi High-Tech Sciences, Inc.) or an equivalent device. The amount of Cr in the surface treatment layer 3 can be measured by boiling and dissolving the surface treated copper foil 1 in a hydrochloric acid aqueous solution mixed in a volume ratio of hydrochloric acid: water = 1:4, and then quantitatively analyzing it using an atomic absorption method. The measurement can be performed using an atomic absorption spectrophotometer (200 Series AA manufactured by Agilent) or an equivalent device.

Regarding the type of surface treatment layer 3, if the amount of the specified element in the surface treatment layer 3 is controlled as described above, there is no particular limitation, and a layer formed by various surface treatments known in the art can be used. Examples of the surface treatment layer 3 include a roughening treatment layer, a chemical resistance treatment layer, a heat resistance treatment layer, a chromate treatment layer, a silane coupling treatment layer, etc. These layers can be used alone or in combination of two or more. Among these layers, in order to improve the adhesion with the substrate 11 (especially the resin substrate), the surface treatment layer 3 preferably contains a roughening treatment layer. Here, in this manual, the so-called "roughening treatment layer" refers to a layer formed by roughening treatment, which is a layer containing roughening particles. In addition, in the roughening treatment, conventional copper plating is sometimes performed as a pre-treatment, or conventional copper plating is performed as a finishing treatment to prevent the roughening particles from falling off, but the "roughening treatment layer" in this manual includes the layer formed by such pre-treatment and finishing treatment.

When the surface treatment layer 3 includes one or more layers selected from the group consisting of a chemical resistance treatment layer, a heat resistance treatment layer, a chromate treatment layer, and a silane coupling treatment layer, these layers are preferably provided on the roughening treatment layer.

The roughening particles are not particularly limited and may be formed of any single substance selected from the group consisting of copper, nickel, cobalt, phosphorus, tungsten, arsenic, molybdenum, chromium and zinc, or an alloy containing any one or more of them. The roughening particles may contain primary roughening particles and secondary roughening particles. The secondary roughening particles preferably have a chemical composition different from that of the primary roughening particles. The primary roughening particles may be formed of copper or a copper alloy, especially copper. The secondary roughening particles may be formed of an alloy containing copper, cobalt and nickel, for example. A coating layer may be formed on at least a portion of the surface of the primary roughening particles. The coating layer is not particularly limited and may be formed of copper, silver, gold, nickel, cobalt, zinc, etc. Among these, the covering layer is preferably formed of copper.

The roughening treatment layer can be formed, for example, by performing a primary roughening treatment to form primary roughening particles, performing a cover plating to form a cover plating layer, and then performing a secondary roughening treatment to form secondary roughening particles. By performing the roughening treatment in this way, it is easy to form a surface treatment layer 3 having the above-mentioned characteristics.

The roughened particle layer can be formed by electroplating. The conditions of the roughening treatment are not particularly limited, but typical conditions are as follows. Electroplating can be performed once or multiple times. (Conditions for roughening treatment) Plating solution composition: 5-15 g/L Cu, 40-100 g/L sulfuric acid, 1-6 ppm tungsten (from sodium tungstate dihydrate) Plating solution temperature: 20-50°C Electroplating conditions: current density 30-90 A/dm ² , time 0.1-8 seconds (Conditions for covering coating) Plating solution composition: 10-30 g/L Cu, 70-130 g/L sulfuric acid Plating solution temperature: 30-60°C Electroplating conditions: current density 4.8-15 A/dm ² , time 0.1-8 seconds

There is no particular limitation on the chemical-resistant layer and the heat-resistant layer, and the layer can be formed of materials known in the art. The chemical-resistant layer sometimes also functions as a heat-resistant layer, so a layer having the functions of both the chemical-resistant layer and the heat-resistant layer can be formed as the chemical-resistant layer and the heat-resistant layer. As a chemical treatment resistant layer and/or heat treatment resistant layer, a layer containing one or more elements selected from the group consisting of nickel, zinc, tin, cobalt, molybdenum, copper, tungsten, phosphorus, arsenic, chromium, vanadium, titanium, aluminum, gold, silver, platinum group elements, iron and tantalum (can be any form of metal, alloy, oxide, nitride, sulfide, etc.) can be formed. Among these, the chemical treatment resistant layer and the heat treatment resistant layer are preferably Ni-Zn layers.

The chemical-resistant layer and the heat-resistant layer can be formed by electroplating. The conditions of electroplating are not particularly limited. The typical conditions of chemical-resistant and heat-resistant treatments using general electroplating equipment are as follows. Furthermore, each electroplating can be performed once or in multiple times. (Chemical-resistant and heat-resistant treatments: conditions for forming Ni-Zn layer) Coating liquid composition: 1-30 g/L Ni, 1-30 g/L Zn Coating liquid pH: 2-5 Coating liquid temperature: 30-50°C Electroplating conditions: current density 0.1-10 A/dm ² , time 0.1-5 seconds

The chromate treatment layer is not particularly limited and can be formed by materials known in the art. In this specification, the so-called "chromate treatment layer" means a layer formed by a liquid containing chromic anhydride, chromic acid, dichromic acid, chromate or dichromate. The chromate treatment layer can be formed as a layer containing one or more elements selected from the group consisting of cobalt, iron, nickel, molybdenum, zinc, tantalum, copper, aluminum, phosphorus, tungsten, tin, arsenic and titanium (can be any form of metal, alloy, oxide, nitride, sulfide, etc.). Examples of the chromate-treated layer include a chromate-treated layer treated with an aqueous solution of chromic anhydride or potassium dichromate, a chromate-treated layer treated with a treatment solution containing chromic anhydride or potassium dichromate and zinc, etc.

The chromate treatment layer can be formed by known methods such as immersion chromate treatment and electrolytic chromate treatment. The conditions of the chromate treatment are not particularly limited. The typical conditions of general chromate treatment are as follows. Furthermore, the chromate treatment can be performed once or multiple times. Composition of chromate solution: 1-10 g/L K ₂ Cr ₂ O ₇ , 0.01-10 g/L Zn Chromate solution pH: 2-5 Chromate solution temperature: 30-55°C Electrolysis conditions: current density 0.1-10 A/dm ² , time 0.1-5 seconds (in the case of electrolytic chromate treatment)

The silane coupling treatment layer is not particularly limited, and can be formed of materials known in the art. In this specification, the so-called "silane coupling treatment layer" means a layer formed by a silane coupling agent. The silane coupling agent is not particularly limited, and those known in the art can be used. Examples of silane coupling agents include amino silane coupling agents, epoxy silane coupling agents, butyl silane coupling agents, methacryloyl silane coupling agents, vinyl silane coupling agents, imidazole silane coupling agents, tris silane coupling agents, and the like. Silane coupling agents, etc. Among them, amino-based silane coupling agents and epoxy-based silane coupling agents are preferred. Silane coupling agents can be used alone or in combination of two or more. As a typical method for forming a silane coupling treatment layer, the following method can be cited, that is, by applying a 1-3 volume % aqueous solution of the above-mentioned silane coupling agent and drying it to form a silane coupling treatment layer.

The copper foil 2 used for the surface-treated copper foil 1 is not particularly limited and may be either an electrolytic copper foil or a rolled copper foil. The electrolytic copper foil can be produced, for example, by electrolytically depositing copper from a copper sulfate bath onto a drum formed of titanium or stainless steel. The electrolytic copper foil has a flat S surface (glossy surface) formed on the drum side and an M surface (matte surface) formed on the opposite side of the S surface.

The material of the copper foil 2 is not particularly limited. When the copper foil 2 is a rolled copper foil, high-purity copper such as refined copper (JIS H3100 alloy number C1100) or oxygen-free copper (JIS H3100 alloy number C1020 or JIS H3510 alloy number C1011) which is generally used as a circuit pattern of a printed wiring board can be used. In addition, copper alloys such as tin-doped copper, silver-doped copper, copper alloys added with Cr, Zr or Mg, and Carsonite copper alloys added with Ni and Si can also be used. In this specification, the so-called "copper foil 2" refers to a concept that also includes copper alloy foil.

The thickness of the copper foil 2 is not particularly limited, and may be, for example, 1 to 1000 μm, 1 to 500 μm, 1 to 300 μm, 3 to 100 μm, 5 to 70 μm, 6 to 35 μm, or 9 to 18 μm.

The surface treated copper foil 1 composed of the copper foil 2 and the surface treated layer 3 as described above can be manufactured according to a method known in the art. Here, the amount of Ni, Zn, Cr and Co (when present) in the surface treated layer 3 can be controlled by adjusting the formation conditions of the surface treated layer 3. The formation conditions include, for example, the current value, the surface treatment time, the concentration of each metal ion in the bath, the temperature or pH of the bath, etc.

The copper-clad laminate 10 of the embodiment of the present invention, as described above, has a surface-treated copper foil 1 and a substrate 11 disposed on the surface-treated layer 3 of the surface-treated copper foil 1. This copper-clad laminate 10 can be manufactured by connecting the substrate 11 to the surface-treated layer 3 of the surface-treated copper foil 1. The substrate 11 is not particularly limited, and those known in the art can be used, preferably a resin substrate. Examples of resin substrates include substrates composed of the following resins, namely, paper-based phenolic resins, paper-based epoxy resins, synthetic fiber cloth-based epoxy resins, glass cloth-paper composite-based epoxy resins, glass cloth-glass non-woven cloth composite-based epoxy resins, glass cloth-based epoxy resins, polyester films, polyimide resins, liquid crystal polymers, fluororesins, etc. Among these, the resin substrate is preferably a substrate composed of polyimide resins.

The method for bonding the surface-treated copper foil 1 and the substrate 11 is not particularly limited and can be performed according to a method known in the art. For example, the surface-treated copper foil 1 and the substrate 11 can be laminated and heat-pressed. The copper-clad laminate 10 manufactured in this way can be used to manufacture a printed wiring board.

The copper-clad laminate 10 of the embodiment of the present invention uses the surface-treated copper foil 1, so after the surface-treated copper foil 1 is etched to form the circuit pattern 20, undercutting can be suppressed during soft etching.

The manufacturing method of the printed wiring board of the embodiment of the present invention is carried out in the following manner, that is, after etching the surface treated copper foil 1 of the copper clad laminate 10 to form the circuit pattern 20, soft etching is performed. The method for forming the circuit pattern 20 is not particularly limited, and known methods such as subtractive method and semi-additive method can be used. Among them, the method for forming the circuit pattern 20 is preferably the subtractive method.

When a printed wiring board is manufactured by a subtractive method, it is preferably carried out in the following manner. First, a resist is applied to the surface of the surface-treated copper foil 1 of the copper-clad laminate 10, and then exposed and developed to form a prescribed resist pattern. Then, the surface-treated copper foil 1 where the resist pattern is not formed (i.e., the useless part) is removed by etching to form a circuit pattern 20. Finally, the resist pattern on the surface-treated copper foil 1 is removed and soft etching is performed. Furthermore, the various conditions in the subtractive method are not particularly limited and can be performed according to the conditions known in the technical field.

The manufacturing method of the printed wiring board of the embodiment of the present invention uses the above-mentioned copper-clad multilayer board 10, so that the circuit pattern 20 with suppressed undercut can be formed, and the reliability of the circuit pattern 20 (for example, the close contact strength between the substrate 11 and the circuit pattern 20) is particularly good. [Example]

Hereinafter, the embodiments of the present invention will be described in more detail, but the present invention is not limited to these embodiments.

(Example 1) Prepare a rolled copper foil (HG foil manufactured by JX Metal Co., Ltd.) with a thickness of 12 μm. After degreasing and pickling the surface of the copper foil, a roughening treatment layer, a heat-resistant and chemical-resistant treatment layer (Ni-Zn layer), a chromate treatment layer and a silane coupling treatment layer are sequentially formed on one side as surface treatment layers to obtain a surface-treated copper foil. The formation conditions of each treatment layer are set as follows.

(1) Roughening treatment layer <Conditions for forming roughening particles> Coating solution composition: 12 g/L Cu, 50 g/L sulfuric acid, 5 ppm tungsten (from sodium tungstate dihydrate) Coating solution temperature: 27°C Number of coating treatments: 2 times Electroplating conditions: current density 49.8 A/dm ² , time 0.81 seconds <Conditions for forming covering coating> Coating solution composition: 20 g/L Cu, 100 g/L sulfuric acid Coating solution temperature: 50°C Number of coating treatments: 2 times Electroplating conditions: current density 11.9 A/dm ² , time 1.15 seconds

(2) Heat-resistant and chemical-resistant layer <Conditions for forming the Ni-Zn layer> Coating solution composition: 23.5 g/L Ni, 4.5 g/L Zn Coating solution pH: 3.6 Coating solution temperature: 40°C Electroplating conditions: Current density 0.70 A/dm ² , time 0.59 seconds Number of plating treatments: 1

(3) Chromate treatment layer <Conditions for forming the electrolytic chromate treatment layer> Chromate solution composition: 3 g/L K ₂ Cr ₂ O ₇ , 0.33 g/L Zn Chromate solution pH: 3.65 Chromate solution temperature: 55°C Electrolysis conditions: Current density 1.9 A/dm ² , time 0.59 seconds Chromate treatment times: 2 times

(4) Silane coupling treatment layer The silane coupling treatment layer is formed by applying a 1.2 volume % aqueous solution of N-2-(aminoethyl)-3-aminopropyltrimethoxysilane and drying it.

(Example 2) A surface-treated copper foil was obtained under the same conditions as in Example 1 except that the electroplating conditions were changed to a current density of 1.5 A/dm ² and a time of 0.59 seconds in forming the heat-resistant and chemical-resistant layer (Ni—Zn layer).

(Example 3) A surface-treated copper foil was obtained under the same conditions as in Example 1 except that the electroplating conditions were changed to a current density of 1.9 A/dm ² and a time of 0.59 seconds in forming the heat-resistant and chemical-resistant layer (Ni—Zn layer).

(Example 4) A surface-treated copper foil was obtained under the same conditions as in Example 1 except that the electroplating conditions were changed to a current density of 2.2 A/dm ² and a time of 0.59 seconds in forming the heat-resistant and chemical-resistant layer (Ni—Zn layer).

(Comparative Example 1) (1) Roughening layer <Conditions for forming roughening particles> Coating solution composition: 11 g/L Cu, 50 g/L sulfuric acid Coating solution temperature: 27°C Number of coating passes: 2 times Electroplating conditions: Current density 41.3 A/dm ² , time 0.68 seconds <Conditions for forming a covering layer> Coating solution composition: 20 g/L Cu, 100 g/L sulfuric acid Coating solution temperature: 50°C Number of coating passes: 2 times Electroplating conditions: Current density 8.2 A/dm ² , time 0.77 seconds

(2) Heat-resistant and chemical-resistant layer <Conditions for forming the Ni-Zn layer> Coating solution composition: 23.5 g/L Ni, 4.5 g/L Zn Coating solution pH: 3.6 Coating solution temperature: 40°C Electroplating conditions: Current density 3.42 A/dm ² , time 0.39 seconds Number of plating treatments: 1

(3) Chromate treatment layer <Conditions for forming the electrolytic chromate treatment layer> Chromate solution composition: 3 g/L K ₂ Cr ₂ O ₇ , 0.33 g/L Zn Chromate solution pH: 3.65 Chromate solution temperature: 55°C Electrolysis conditions: Current density 2.7 A/dm ² , time 0.39 seconds Chromate treatment times: 2 times

(4) Silane coupling treatment layer The silane coupling treatment layer is formed by applying a 1.2 volume % aqueous solution of N-2-(aminoethyl)-3-aminopropyltrimethoxysilane and drying it.

The following evaluations were performed on the surface-treated copper foils obtained in the above-mentioned Examples 1 to 4 and Comparative Example 1. ＜The amount of each element attached in the surface-treated layer＞ Regarding the amount of Zn and Ni attached in the surface-treated layer, the surface-treated copper foil obtained was dissolved in an aqueous nitric acid solution prepared by mixing nitric acid: water in a volume ratio of 1:2, and the amount was measured by ICP analysis. An inductively coupled plasma emission spectrometer (SPS3520UV, manufactured by Hitachi High-Tech Sciences, Inc.) was used for the measurement. The amount of Cr attached in the surface-treated layer was measured in the following manner, that is, the surface-treated copper foil obtained was boiled and dissolved in an aqueous hydrochloric acid solution prepared by mixing hydrochloric acid: water in a volume ratio of 1:4, and quantitative analysis was performed using atomic absorption spectrometry. The measurement was performed using an atomic absorption spectrophotometer (Agilent, 200 Series AA). The amounts of Zn, Ni, and Cr deposited were expressed as the mass (μg) of Zn, Ni, and Cr deposited per unit area (dm ² ) of each surface-treated copper foil. Based on the amounts of the elements deposited, the ratio of the Ni deposited amount to the total of the Ni deposited amount and the Zn deposited amount (expressed as "Ni ratio") and the ratio of the Cr deposited amount to the total of the Ni deposited amount, the Zn deposited amount, and the Cr deposited amount (expressed as "Cr ratio") were calculated.

<Undercut width> After the surface-treated copper foil and the 25 μm-thick polyimide film (PIXEO (registered trademark) manufactured by Kaneka Co., Ltd.) were laminated, they were heat-pressed at 360°C for 30 minutes. This heat-pressing was performed entirely at 2.5 kPa. Then, using an etching solution, a circuit pattern was formed in such a way that the width became 200 μm. Next, the circuit pattern was soft-etched for 1 minute using a soft etching solution containing hydrogen peroxide and sulfuric acid as the main components (Clean Etch CPE-750 manufactured by Mitsubishi Gas Chemical Co., Ltd.). Then, the undercut after soft etching was observed from the back side of the polyimide film using an optical microscope. Here, an example of an observed image of a circuit pattern with undercut is shown in FIG4. Since the polyimide film is thin and has transmissive properties, the undercut can be observed through the polyimide film and the undercut widths W1 and W2 can be measured. The undercut widths W1 and W2 are measured at three randomly selected locations, and the average value thereof is taken as the result of the undercut width. The results of the above-mentioned characteristic evaluations are shown in Table 1.

[Table 1] Adhesion amount (μg/dm ² ) Ni rate (%) Cr rate (%) Undercut width (μm) Ni Zn Cr Ni＋Zn Embodiment 1 27 151 98 178 15.2 35.5 2.9 Embodiment 2 58 261 101 319 18.2 24.0 2.3 Embodiment 3 65 331 107 396 16.4 21.3 4.7 Embodiment 4 72 394 120 466 15.5 20.5 5.8 Comparative example 1 70 450 61 520 13.5 10.5 7.5

As shown in Table 1, the surface treated layers of the surface treated copper foils of Examples 1 to 4 contain Ni, Zn and Cr, and in the surface treated layers, the Zn attachment amount is 100 to 500 μg/dm ² , the Cr attachment amount is 70 to 150 μg/dm ² , and the Cr ratio is 18.0 to 50.0%. The Cr attachment amount and Cr ratio of the surface treated layer of Comparative Example 1 are outside the above ranges. Compared with Comparative Example 1, the undercut width of the surface treated copper foils of Examples 1 to 4 is smaller.

From the above results, it can be seen that according to the embodiment of the present invention, a surface treated copper foil and copper clad laminate can be provided that can suppress undercut when forming a circuit pattern by soft etching. In addition, according to the embodiment of the present invention, a method for manufacturing a printed wiring board having a circuit pattern with suppressed undercut can be provided.

Therefore, the embodiments of the present invention may be as follows. [1] A surface-treated copper foil having a copper foil and a surface-treated layer formed on at least one side of the copper foil, wherein the surface-treated layer contains Ni, Zn and Cr, wherein the amount of Zn deposited in the surface-treated layer is 100 to 500 μg/dm ² , the amount of Cr deposited in the surface-treated layer is 70 to 150 μg/dm ² , and the ratio of the amount of Cr deposited to the total amount of Ni deposited, the amount of Zn deposited and the amount of Cr deposited is 18.0 to 50.0%. [2] A surface-treated copper foil as described in [1], wherein the surface-treated layer further contains Co, wherein the amount of Co deposited in the surface-treated layer is less than 100 μg/dm ² . [3] The surface-treated copper foil as described in [1], wherein the surface treatment layer does not contain Co. [4] The surface-treated copper foil as described in any one of [1] to [3], wherein the Zn attachment amount is 151 to 394 μg/dm ² . [5] The surface-treated copper foil as described in [4], wherein the Zn attachment amount is 151 to 331 μg/dm ² . [6] The surface-treated copper foil as described in any one of [1] to [5], wherein the Cr attachment amount is 98 to 120 μg/dm ² . [7] The surface-treated copper foil as described in [6], wherein the Cr attachment amount is 98 to 107 μg/dm ² . [8] The surface-treated copper foil as described in any one of [1] to [7], wherein the Ni attachment amount is 10 to 100 μg/dm ² . [9] The surface-treated copper foil as described in [8], wherein the Ni attachment amount is 27 to 72 μg/dm ² . [10] The surface-treated copper foil as described in any one of [1] to [9], wherein the ratio of the Cr attachment amount to the total of the Ni attachment amount, the Zn attachment amount and the Cr attachment amount is 20.0 to 40.0%. [11] The surface-treated copper foil as described in [10], wherein the ratio of the Cr attachment amount to the total of the Ni attachment amount, the Zn attachment amount and the Cr attachment amount is 20.5 to 35.5%. [12] The surface-treated copper foil as described in any one of [1] to [11], wherein the ratio of the Ni attachment amount to the total of the Ni attachment amount and the Zn attachment amount is 10.0 to 20.0%. [13] The surface-treated copper foil as described in [12], wherein the ratio of the Ni attachment amount to the total of the Ni attachment amount and the Zn attachment amount is 15.2 to 18.2%. [14] The surface-treated copper foil as described in any one of [1] to [13], wherein the total of the Ni attachment amount and the Zn attachment amount is 100 μg/dm ² or more and less than 500 μg/dm ² . [15] A surface treated copper foil as described in [14], wherein the total amount of Ni and Zn deposited is 178 to 466 μg/dm ² . [16] A surface treated copper foil as described in any one of [1] to [15], wherein the surface treatment layer includes a roughening treatment layer. [17] A copper clad laminate comprising a surface treated copper foil as described in any one of [1] to [16], and a substrate disposed on the surface treatment layer of the surface treated copper foil. [18] A method for manufacturing a printed wiring board, comprising etching the surface treated copper foil of the copper clad laminate as described in [17] to form a circuit pattern, and then performing soft etching.

(Contribution to SDGs) According to the implementation form of the present invention, a surface-treated copper foil and a copper-clad laminate that can suppress undercutting during soft etching, as well as a method for manufacturing a printed wiring board having a circuit pattern with suppressed undercutting can be provided, thereby potentially improving the product yield of electronic equipment and the like. Improving the product yield is related to the stable supply of products or the reduction of the loss of metal raw materials, which are limited resources. Therefore, the above implementation form may contribute to Goal 9 of the Sustainable Development Goals (SDGs) led by the United Nations, "Strive for resilient infrastructure, promote inclusive and sustainable industrialization, and promote innovation" or Goal 12, "Ensure sustainable production and consumption patterns."

1: Surface treated copper foil 2: Copper foil 3,4: Surface treatment layer 10: Copper clad laminate 11: Substrate 20,30: Circuit pattern 40: Undercut

[FIG. 1] is a cross-sectional view showing an example of a copper-clad laminate having a surface-treated copper foil of an embodiment of the present invention. [FIG. 2] is a cross-sectional view showing an example of a state where a circuit pattern is formed by etching the surface-treated copper foil of a copper-clad laminate having an embodiment of the present invention, and then soft etching is performed. [FIG. 3] is a cross-sectional view showing an example of a state where a circuit pattern is formed by etching the surface-treated copper foil of a copper-clad laminate having a conventional surface-treated copper foil, and then soft etching is performed. [FIG. 4] is an example of an observed image of a circuit pattern with undercut.

Claims (17)

A surface-treated copper foil comprises a copper foil and a surface-treated layer formed on at least one side of the copper foil. The surface-treated layer contains Ni, Zn and Cr. In the surface-treated layer, the Zn attachment amount is 100-500 μg/dm ² , the Cr attachment amount is 70-150 μg/dm ² , and the ratio of the Cr attachment amount to the total of the Ni attachment amount, the Zn attachment amount and the Cr attachment amount is 18.0-50.0%, and the ratio of the Ni attachment amount to the total of the Ni attachment amount and the Zn attachment amount is 10.0-18.2%. The surface treated copper foil of claim 1, wherein the surface treated layer further contains Co, and the amount of Co deposited in the surface treated layer is less than 100 μg/dm ² . The surface-treated copper foil of claim 1, wherein the surface-treated layer does not contain Co. The surface treated copper foil of claim 1, wherein the Zn attachment amount is 151-394 μg/dm ² . The surface treated copper foil of claim 4, wherein the Zn attachment amount is 151-331 μg/dm ² . The surface treated copper foil of claim 1, wherein the Cr adhesion amount is 98-120 μg/dm ² . The surface treated copper foil of claim 6, wherein the Cr adhesion amount is 98-107 μg/dm ² . The surface treated copper foil of claim 1, wherein the Ni adhesion amount is 10-100 μg/dm ² . The surface treated copper foil of claim 8, wherein the Ni adhesion amount is 27-72 μg/dm ² . The surface-treated copper foil of claim 1, wherein the ratio of the Cr attachment amount to the total of the Ni attachment amount, the Zn attachment amount and the Cr attachment amount is 20.0-40.0%. The surface-treated copper foil of claim 10, wherein the ratio of the Cr attachment amount to the total of the Ni attachment amount, the Zn attachment amount and the Cr attachment amount is 20.5-35.5%. The surface-treated copper foil of claim 1, wherein the ratio of the Ni attachment amount to the total of the Ni attachment amount and the Zn attachment amount is 15.2-18.2%. The surface-treated copper foil of claim 1, wherein the total amount of Ni adhesion and the amount of Zn adhesion is greater than or equal to 100 μg/dm ² and less than 500 μg/dm ² . The surface-treated copper foil of claim 13, wherein the total amount of Ni and Zn deposited is 178-466 μg/dm ² . A surface-treated copper foil as claimed in any one of claims 1 to 14, wherein the surface treatment layer comprises a roughening treatment layer. A copper-clad laminate comprises a surface-treated copper foil according to any one of claims 1 to 14, and a substrate disposed on the surface-treated layer of the surface-treated copper foil. A method for manufacturing a printed wiring board comprises etching the surface treated copper foil of the copper clad laminate of claim 16 to form a circuit pattern and then performing soft etching.