Etchant and method for manufacturing a circuit substrate

Abstract

The present invention is an etchant that selectively etches the copper layer of a workpiece containing a precious metal layer of a metal more expensive than copper and a copper layer. The etchant comprises: copper ions, one or more nitrogen-containing compounds selected from the group consisting of heterocyclic compounds having two or more nitrogen atoms in the ring and compounds containing amino groups having eight or fewer carbon atoms, polyalkylene glycol, and halide ions; the aforementioned etchant contains 0.0005% to 7% by weight of polyalkylene glycol and contains 1 ppm to 250 ppm of halide ions.

Description

Technical Field

[0001] This invention relates to an etchant and a method for manufacturing a circuit board. Background Technology

[0002] Traditional methods for forming fine circuit patterns on circuit boards include a semi-additive process (SAP) where a seed layer is formed by electroless copper plating on the surface of an insulating resin layer, photoresist is plated onto this seed layer, copper is electroplated to form a circuit, and then the seed layer remaining on the substrate between the circuits is etched away. In this semi-additive process, the surface of the copper plating layer constituting the circuit is plated with metals more expensive than copper (metals with low ionization tendency), such as gold, silver, or palladium. Therefore, when etching away the seed layer, an etchant is needed that selectively etches the copper in the seed layer (especially the copper in the electroless copper plating layer).

[0003] Etching agents that select copper for etching on substrates where different types of metals coexist, such as the etchant disclosed in Patent Document 1 (Japanese Patent Application Publication No. 2012-129304).

[0004] On the other hand, when copper, which is electrically connected to a metal more expensive than copper, comes into contact with the etchant, a phenomenon known as galvanic corrosion may occur. Galvanic corrosion refers to the corrosion of the metal with a greater ionization tendency when two metals with different ionization tendencies are placed in an electrolyte, forming a localized cell. In the case of etching a substrate where copper and a more expensive metal coexist, some copper may be over-etched due to galvanic corrosion. Etching agents that suppress such galvanic corrosion include, for example, the etchant disclosed in Patent Document 2 (WO2019 / 013160). Patent Document 2 describes such an etchant as having excellent selective etching properties for copper, reliably suppressing galvanic corrosion, and also exhibiting excellent etching speed.

[0005] However, the etchant described in Patent Document 2 is an alkaline etchant with a pH of 7.8 to 11, which limits its application in the manufacturing process. Therefore, there is a need for an etchant that can reliably suppress over-etching of parts caused by galvanic corrosion, etc., even at lower pH levels, and that has excellent selective etching properties for copper.

[0006] [Existing Technical Documents]

[0007] [Patent Literature]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2012-129304

[0009] [Patent Document 2] International Publication No. WO2019 / 013160. Summary of the Invention

[0010] [The problem that the invention aims to solve]

[0011] The present invention was made in view of the aforementioned problems of conventional technology, with the aim of providing an etchant that can suppress partial over-etching even at relatively low pH and has excellent selective etching properties for copper.

[0012] Furthermore, the research focuses on providing a method for manufacturing circuit boards that can suppress over-etching of parts at relatively low pH and selectively etch copper.

[0013] [Methods for solving the problem]

[0014] This invention relates to etchants.

[0015] It selectively etches the copper layer of the workpiece, which contains a precious metal layer containing a metal more expensive than copper, and a copper layer.

[0016] The etchant contains: copper ions;

[0017] Selected from one or more nitrogen-containing compounds in the group consisting of heterocyclic compounds having two or more nitrogen atoms in the ring and compounds containing amino groups having eight or fewer carbon atoms;

[0018] Polyalkylene glycol; and

[0019] halide ions;

[0020] The aforementioned etchant contains 0.0005% by weight and 7% by weight of polyalkylene glycol;

[0021] It contains halide ions ranging from 1 ppm to 250 ppm.

[0022] The present invention allows the aforementioned halide ions to be at least one selected from the group consisting of chloride ions and bromide ions.

[0023] The pH of this invention can be above 6.0 or below 8.0.

[0024] The present invention may contain 0.5% by weight or more and 10.0% by weight of the aforementioned copper ions.

[0025] The present invention may contain 0.1% to 30.0% by weight of the aforementioned nitrogen-containing compound.

[0026] This invention does not contain organic acids or contains more than 0% by weight but less than 7% by weight of organic acids.

[0027] The aforementioned nitrogen-containing compound can be an imidazole.

[0028] In this invention, the aforementioned alkyldiol can be polyethylene glycol.

[0029] The present invention relates to a method for manufacturing a circuit board, wherein an etchant described in any of the foregoing is used to selectively etch a copper layer of a workpiece containing a precious metal layer containing a metal more expensive than copper and a copper layer, thereby forming a circuit.

[0030] In the present invention relating to a method for manufacturing a circuit board, the aforementioned noble metal layer may be a layer containing gold.

[0031] [The effects of the invention]

[0032] According to the present invention, an etchant that can reliably suppress partial over-etching even at relatively low pH and has excellent selective etching properties for copper can be provided.

[0033] Furthermore, a method for manufacturing circuit boards that can reliably suppress over-etching of parts and selectively etch copper can be provided even at relatively low pH levels. Attached Figure Description

[0034] Figure 1 This is a partial cross-sectional schematic diagram showing the outline of the circuit board.

[0035] Figure 2 This is a partial cross-sectional schematic diagram showing the outline of the circuit board.

[0036] Figure 3 This is a schematic diagram used to illustrate the measurement of the side etching amount. Detailed Implementation

[0037] The following describes embodiments of the etchant of the present invention and the method for manufacturing the circuit board of the present invention (hereinafter also referred to as the manufacturing method).

[0038] (Etching agent)

[0039] The etchant of this embodiment selectively etches the copper layer of a workpiece containing a precious metal layer (more expensive than copper) and a copper layer. The etchant contains copper ions, one or more nitrogen-containing compounds selected from the group consisting of heterocyclic compounds having two or more nitrogen atoms in the ring and compounds containing amino groups having eight or fewer carbon atoms, polyalkylene glycol, and halide ions. The etchant contains 0.0005% to 7% by weight of polyalkylene glycol and 1 ppm to 250 ppm of halide ions.

[0040] Furthermore, in this embodiment, "copper" refers to pure copper and copper alloys containing 90% by weight or more. Moreover, in this embodiment, "metals more expensive than copper" refers to metals with a lower ionization tendency than Cu.

[0041] [Copper ions]

[0042] The etchant in this embodiment contains copper ions. Copper ions, preferably divalent copper ions (Cu), are preferred.2+ Copper ions are supplied to the etchant from a copper ion source. Copper ions are a component that acts as an oxidizing agent for copper.

[0043] Copper ion sources that supply copper ions include, for example, copper hydroxide, copper complexes of organic acids, copper carbonate, copper sulfate, copper oxide, copper chloride, copper bromide, copper halides, or copper complexes of nitrogen-containing compounds, as described below.

[0044] From the perspective of improving etching speed, copper formate, copper acetate, copper chloride, and copper bromide are listed as examples.

[0045] Copper ion sources can be used alone or in combination.

[0046] From the viewpoint of increasing the etching rate, the aforementioned copper ion content is exemplified by, for example, 0.5% to 10.0% by weight or 1.0% to 5% by weight.

[0047] The content of the copper ion source can be appropriately determined to achieve the aforementioned copper ion content.

[0048] [Nitrogen-containing compounds]

[0049] The etchant of this embodiment includes one or more nitrogen-containing compounds (hereinafter referred to as nitrogen-containing compounds) selected from the group consisting of heterocyclic compounds having two or more nitrogen atoms in the ring (hereinafter also referred to as heterocyclic compounds) and compounds containing amino groups with eight or fewer carbon atoms (hereinafter also referred to as amino-containing compounds). The nitrogen-containing compound is a complex with copper dissolved in the etchant and is formulated as a component retained in the etchant.

[0050] Heterocyclic compounds are not particularly limited to any heterocyclic compound having two or more nitrogen atoms within the ring, such as imidazoles, pyrazoles, triazoles, tetraazoles, and azoles of their derivatives. From the viewpoint of forming complexes with dissolved copper, imidazoles such as imidazoles and benzimidazoles, or pyrazoles such as pyrazoles, are preferred. Specifically, imidazoles, 2-methylimidazolium, 1,2-diethylimidazolium, benzimidazoles, pyrazoles, triazoles, and benzotriazoles are examples, with imidazoles, 2-methylimidazolium, 1,2-diethylimidazolium, and 2-ethyl-4-methylimidazolium being particularly preferred.

[0051] [Amino-containing compounds]

[0052] There are no particular restrictions on the amino-containing compounds as long as they have 8 or fewer carbon atoms. From the viewpoint of forming complexes with dissolved copper, compounds with 0 or more carbon atoms and 7 or fewer, or 0 or more carbon atoms and 5 or fewer carbon atoms, are more preferred.

[0053] Amino compounds include, for example, ammonia; alkylammonium compounds such as methylammonium, dimethylammonium, and trimethylammonium; alkanolamines; and aromatic amines such as phenylamine. Furthermore, compounds having two or more amino groups, such as ethylenediamine, and quaternary ammonia compounds such as tetramethylammonium are also suitable. From the viewpoint of forming complexes with dissolved copper, ammonia and alkanolamines are particularly preferred.

[0054] Specific examples of alkanolamines include monoethanolamine, N-methylethanolamine, N-ethylethanolamine, N-butylethanolamine, N,N-dimethylethanolamine, N,N-diethylethanolamine, 2-(2-hydroxy)ethoxyethanolamine, and their derivatives; diethanolamine, N-methyldiethanolamine, N-butyldiethanolamine, and their derivatives; triethanolamine; propanolamine; isopropanolamine; hydroxyethyl piperazine; and their derivatives. From the viewpoint of forming complexes with dissolved copper, monoethanolamine, triethanolamine, and N-methyldiethanolamine are particularly preferred.

[0055] From the viewpoint of forming complexes with dissolved copper, nitrogen-containing compounds are more preferably imidazoles, pyrazoles, ammonia, alkanolamines, and more preferably 2-methylimidazole, imidazole, 1,2-diethylimidazole, 2-ethyl-4-methylimidazole, triethanolamine, monoethanolamine, and N-methyldiethanolamine.

[0056] The content of nitrogen-containing compounds is, for example, 1.0% to 30.0% by weight, 5.0% to 25.0% by weight, or 10.0% to 20.0% by weight. By setting the content of nitrogen-containing compounds within the aforementioned range, the etching rate can be increased while suppressing the increase in the viscosity of the etchant.

[0057] Nitrogen-containing compounds can be either heterocyclic compounds or amino-containing compounds, or both.

[0058] In addition, nitrogen-containing compounds can be used individually or in combination of the aforementioned components.

[0059] Heterocyclic compounds and amino-containing compounds are preferred to be used together.

[0060] When both heterocyclic compounds and amino-containing compounds are used as nitrogen-containing compounds, examples include azoles as heterocyclic compounds and alkanolamines as amino-containing compounds. Specifically, examples include selecting one or more of imidazole, 2-methylimidazolium, 1,2-diethylimidazolium, and 2-ethyl-4-methylimidazolium as heterocyclic compounds, and selecting one or more of triethanolamine, monoethanolamine, and N-methyldiethanolamine as amino-containing compounds.

[0061] In this case, the content of azoles is, for example, 0.1% to 25% by weight or 1.0% to 20% by weight or 3.0% to 10% by weight, and the content of alkanolamines is, for example, 0.1% to 25% by weight or 1.0% to 20% by weight or 2.5% to 11% by weight.

[0062] [Polyalkyldiol]

[0063] The etchant in this embodiment contains polyalkylene glycol. Polyalkylene glycol is a component that can suppress excessive etching due to galvanic corrosion and promote uniform etching.

[0064] The polyalkylene glycol in this embodiment also includes polyalkylene glycol and its derivatives.

[0065] Polyalkylene glycols are not particularly limited, but examples include polyethylene glycol, polypropylene glycol, polybutane glycol, and polyoxyethylene-polyoxypropylene block copolymers. From the viewpoint of improving the final result by suppressing uneven etching, polyethylene glycol is preferred. When using polyethylene glycol, polyethylene glycol with a weight-average molecular weight of 200 to 20,000 is preferred.

[0066] From the viewpoint of suppressing excessive etching, the content of polyalkylene glycol is, for example, 0.0005% to 7% by weight, or 0.001% to 5% by weight.

[0067] [Halo ions]

[0068] The etchant in this embodiment contains halide ions. Halide ions are components that improve the solubility and stability of copper and accelerate the etching rate.

[0069] There are no particular restrictions on the source of halide ions supplied to the etchant, including inorganic acids such as hydrogen chloride, hydrogen bromide, and hydrogen iodide; and inorganic salts such as copper chloride, copper bromide, ferric chloride, sodium chloride, sodium iodide, ammonium chloride, and ammonium bromide.

[0070] There are no particular restrictions on the type of halide ions supplied, but examples include halogens such as chlorine, iodine, and bromine. In particular, from the viewpoint of optimizing both galvanic corrosion suppression and etching rate, halide ions selected from at least one group consisting of chloride ions and bromide ions are preferred.

[0071] From the perspective of a suitable etching rate range, the halide ion content can be, for example, 1 ppm to 250 ppm, or 2 ppm to 200 ppm, or 4 ppm to 100 ppm.

[0072] More specifically, for example, when the halide ion is chloride ion, the range is 50 ppm to 200 ppm, and when the halide ion is bromide ion, the range is 2 ppm to 40 ppm, etc.

[0073] [Organic acids]

[0074] The etchant of this embodiment preferably does not contain organic acids, or contains only a small amount. Although organic acids can increase the solubility of copper in the etchant, they can also promote excessive etching due to galvanic corrosion. Therefore, it is preferable that the etchant does not contain organic acids, or if it does contain them, that the content is more than 0% but less than 7% by weight, or more than 1% by weight but less than 6% by weight.

[0075] In cases involving organic acids, the type of organic acid is not particularly limited, but examples include aliphatic saturated monocarboxylic acids, aliphatic saturated dicarboxylic acids, and oxocarboxylic acids, provided that they do not hinder the oxidation of copper or cause an increase in the viscosity of the etchant. Formic acid, acetic acid, propionic acid, butyric acid, hexanoic acid, oxalic acid, lactic acid, malic acid, citric acid, and tartaric acid are particularly preferred.

[0076] [Other ingredients]

[0077] The etchant of this embodiment can be formulated with any of the components that do not impede the purpose of the etchant of this embodiment, as long as they are components that can be formulated in a general etchant.

[0078] [pH]

[0079] In this embodiment, it is preferred to adjust the pH of the etchant to 6.0 or higher and 8.0 or lower, or 6.2 or higher and 7.5 or lower.

[0080] By adjusting the pH to the aforementioned range, excessive etching due to galvanic corrosion can be easily suppressed.

[0081] The pH of the etchant can be adjusted by adjusting the content of the aforementioned components, such as nitrogen-containing compounds, copper ion sources, and halide ion sources. It can also be adjusted by using a pH adjuster.

[0082] The etchant of this embodiment is suitable for etching even at low pH levels. Therefore, it can be easily used even in manufacturing steps that require etching at low pH conditions.

[0083] The etchant of this embodiment can be prepared by dissolving the aforementioned components in water. Examples of water include ion-exchanged water, distilled water, pure water, and ultrapure water. Furthermore, the etchant of this embodiment only needs to be adjusted so that the aforementioned components reach a specified concentration before use. For example, a concentrated solution can be prepared first, and the components can be diluted to a specified concentration before use; or multiple solutions of a portion of all the components can be prepared first, and then the solutions can be mixed before use to ensure that all the components are contained.

[0084] The etchant of this embodiment has an etching rate for copper that is, for example, adjusted to be between 0.3 μm / min and 1.0 μm / min. Furthermore, the etching rate for metals other than copper can be adjusted to be 0.1 μm / min or less. As long as the etching rate is within this range, over-etching of copper can be reliably suppressed, and selective etching of copper is good.

[0085] (Manufacturing method of circuit board)

[0086] Next, a method for manufacturing a circuit board using the etchant of this embodiment will be described.

[0087] The circuit board manufacturing method of this embodiment is to use the etchant of this embodiment to selectively etch the copper layer of the workpiece containing a precious metal layer containing a metal more expensive than copper and a copper layer to form a circuit.

[0088] Examples of circuit boards in this embodiment include printed circuit boards and copper circuit components of thin-film touch sensors. In this case, the workpiece in which a noble metal layer containing a metal more expensive than copper coexists with a copper layer includes, for example... Figure 1 The surface of the insulating resin layer 1 is electroless copper plating to form a seed layer 2 (copper layer), and copper is electrolytically plated on the seed layer 2 to form the circuit board 10 of the circuit 3, etc.

[0089] A gold plating layer 4 (noble metal layer) is formed on the surface of circuit 3 by electrolytic plating or electroless plating. In addition, to prevent diffusion between the gold plating layer 4 and circuit 3, a diffusion prevention layer made of nickel or the like can be formed (not shown in the figure).

[0090] In addition, the precious metal layer formed on the surface of circuit 3 contains metals more expensive than copper, such as palladium, mercury, silver, and platinum, in addition to gold.

[0091] The etchant of this embodiment is suitable for use, particularly in the manufacture of circuit boards where a precious metal layer containing gold coexists with copper.

[0092] Such a circuit board 10 can be formed, for example, by a semi-additive process.

[0093] First, a seed layer 2 is formed on the surface of the insulating resin layer 1 by electroless copper plating. An electroplated photoresist (not shown) is then placed on the seed layer 2, and a circuit 3 is formed by electrolytic copper plating. Additionally, a diffusion prevention layer and a gold plating layer 4 are formed on the surface of the circuit 3 by electroplating. Then, the electroplated photoresist is removed, resulting in a circuit with the following characteristics: Figure 1 The circuit board 10 is composed of circuit 3.

[0094] In addition, in order to etch away the seed layer 2 remaining on the insulating resin layer 1 between the circuits 3, in this embodiment, the etchant described in this embodiment is used for etching to obtain the following result: Figure 2 The circuit board 10 is shown. In addition, the circuits 3 can be electrically connected to each other through inner layer circuits (not shown in the figure).

[0095] There are no particular limitations on the etching method; examples include spraying and immersing the workpiece in an etchant. From the viewpoint of efficiently etching metal in narrow areas such as seed layers between circuits, spraying is preferred.

[0096] There are no particular restrictions on the temperature of the etchant and the processing time during the etching process, but examples include the etchant temperature being above 20°C and below 40°C, and the processing time being above 20 seconds and below 120 seconds.

[0097] During such etching, because the gold in the gold plating layer 4 and the copper in the circuit 3 coexist, and the circuits are electrically connected to each other via inner-layer circuitry, they are prone to galvanic corrosion. In this situation, when combined with... Figure 3 Near the gold plating layer 4 at the top of the circuit 3 shown, excessive etching due to galvanic corrosion has created a recessed state, i.e., side etching. If such side etching is excessive, the circuit width will become narrower, the resistance will increase, and a short circuit may occur.

[0098] The etchant used in this embodiment can suppress side etching caused by galvanic corrosion and maintain a uniform etching rate. Furthermore, it allows for selective etching of copper, particularly the seed layer of electroless copper plating. Therefore, it can also suppress increases in circuit resistance and short circuits in the circuit board.

[0099] The circuit board manufacturing method of this embodiment can also be implemented in a semi-additive process manufacturing method. In other processes, it is also possible to selectively etch the copper layer of the workpiece in which a precious metal layer containing a metal more expensive than copper coexists with a copper layer.

[0100] The etchant and circuit board manufacturing method of this embodiment should be explained separately. Therefore, various embodiments can be implemented by using the etchant of this embodiment in other manufacturing methods, and by combining other technologies.

[0101] Regarding the etchant and circuit board manufacturing method of this embodiment, as described above, it should be understood that the disclosed embodiments are not limited to all the illustrated points. The scope of the present invention is indicated by the scope of the claims, not by the foregoing description, and refers to all modifications within the same sense and scope as the claims.

[0102] [Example]

[0103] The present invention will be described in more detail below with reference to embodiments, but the present invention is not limited to these examples.

[0104] (Etching agent)

[0105] The etching agents for the examples and comparative examples were prepared using the materials shown in Tables 1 to 3 (the remainder being ion-exchanged water).

[0106] Use the following as raw materials.

[0107] A. Halogen ion supply source

[0108] Sodium chloride (manufactured by Kishida Chemical Co., Ltd., Grade 1)

[0109] Ammonium bromide (manufactured by Kishida Chemical Co., Ltd., premium grade)

[0110] Potassium iodide (manufactured by Kishida Chemical Co., Ltd., Grade 1)

[0111] B. Polyalkylene glycol

[0112] Polyethylene glycol (manufactured by Kishida Chemical Co., Ltd., Grade 1, molecular weight 1000)

[0113] C. Copper ion source

[0114] Copper formate (manufactured by Fuji Film & Television and Wako Pure Chemical Industries, Grade 1)

[0115] Copper acetate (manufactured by Kishida Chemical Co., Ltd., Grade 1)

[0116] D. Amino-containing compounds

[0117] Monoethanolamine (manufactured by Fuji Film & Television and Kazuko Pure Chemicals Co., Ltd., Grade 1)

[0118] Triethanolamine (manufactured by Kishida Chemical Co., Ltd., Grade 1)

[0119] N-Methyldiethanolamine (manufactured by Tokyo Chemical Industry Co., Ltd., Grade 1)

[0120] E. Heterocyclic compounds

[0121] 2-Methylimidazole (manufactured by Tokyo Chemical Industry Co., Ltd., Grade 1)

[0122] Imidazole (manufactured by Kishida Chemical Co., Ltd., premium grade)

[0123] F. Organic acids

[0124] Maleic acid (manufactured by Fuji Film & Television and Koko Pure Chemical Industries, Grade 1)

[0125] Malic acid (manufactured by Kishida Chemical Co., Ltd., premium grade)

[0126] Lactic acid (manufactured by Fuji Film & Television and Kazumitsu Pure Chemicals Co., Ltd., Grade 1)

[0127] d-Tartaric acid (manufactured by Kishida Chemical Co., Ltd., Grade 1)

[0128] (pH measurement)

[0129] The pH of each etchant was measured at 30°C using a pH measuring device F-71 manufactured by Horiba. The results are shown in Table 2.

[0130] (Test substrate)

[0131] Prepare the test substrate as shown below.

[0132] On a resin substrate with a resin layer thickness of 0.2 mm, a copper seed layer with a thickness of 0.3 μm was prepared using an electroless copper plating solution (manufactured by Okuno Pharmaceutical Co., Ltd., electroless copper plating solution: ADCOPPER (trade name)). Then, photoresist (manufactured by Hitachi Chemical Co., Ltd., RD-1225 (trade name)) was used to form a photoresist pattern (approximately 25 μm thick, line and spacing L / S = 15 μm / 30 μm). Separately, an electrolytic copper plating layer with a thickness of 15 μm and a width of 30 μm was prepared using an electrolytic copper plating solution (manufactured by Okuno Pharmaceutical Co., Ltd., electrolytic copper plating solution: TOPLUCINA (trade name)). Then, an electrolytic nickel-gold plating layer was prepared on top of the electrolytic copper plating layer using an electrolytic nickel-gold plating solution. Finally, the photoresist was removed by treating with a removal solution (manufactured by Mitsubishi Gas Chemical Co., Ltd., CLEAN ETCHR-100) for 1 minute.

[0133] (Etching)

[0134] Using the aforementioned test substrate, etching was performed using the etchants of the examples and comparative examples to remove the seed layer exposed between the electrolytic copper plating layers.

[0135] Etching was performed using a nozzle (Ikenai Co., Ltd., Yamagata fan nozzle INVV9030) at a spray pressure of 0.1 MPa and a processing temperature of 40°C. The processing time was until the seed layer between the electrolytic copper plating layers on the test substrate was completely removed. After etching, the substrate was rinsed with water, dried, and evaluated as shown below.

[0136] (Measurement of side etching amount)

[0137] A portion of each etched test substrate is cut and embedded in thermosetting resin, then polished to allow observation of the cross-section of the electrolytic copper plating layer, creating samples for cross-sectional observation. The cross-section of the electrolytic copper plating layer is observed using SEM (Scanning Electron Microscopy) to capture images and perform [further processing]. Figure 3 The measurements of the width TW of the nickel / gold layer and the width BW of the electrolytic copper plating on the electrolytic copper plating layer are shown in Tables 1 to 3. The side etching amount is expressed as (TW-BW)÷2 (μm).

[0138] (Judging uneven etching)

[0139] A 5×5cm electrolytic copper plating plate was etched using the etchant from each example and comparative example under the same conditions as the etching of each test substrate. The copper surface was then visually observed. A uniform finish was considered to indicate no unevenness, while the presence of shadows indicated unevenness.

[0140] (Measurement of etching rate)

[0141] Prepare a 5×5cm electrolytic copper plating plate and measure its weight W1 (g). Treat each plating plate with the etchant of each example and comparative example for 1 minute at 40°C. Measure the weight W2 (g) after treatment. The etching rate is calculated using the following formula and is shown in Tables 1 to 3.

[0142] (W1-W2)×10000÷223(μm / min)

[0143] The results are shown in Tables 1 to 3.

[0144] [Table 1]

[0145]

[0146] [Table 2]

[0147]

[0148] [Table 3]

[0149]

[0150] (Self-criticism)

[0151] As shown in Table 1, in each embodiment, the amount of side etching is less than that in the comparative example, and the etching rate can be maintained. Moreover, no etching unevenness is generated.

[0152] In Comparative Examples 3 and 4, due to uneven etching, the test substrates were not etched.

[0153] Moreover, as shown in Table 2, side etching can be suppressed even at pH 8.0 in each embodiment.

[0154] Furthermore, as shown in Table 3, even when the types of amino-containing compounds and heterocyclic compounds are changed, side etching can be suppressed in each embodiment.

[0155] Explanation of reference numerals in the attached figures

[0156] 1: Insulating resin layer, 2: Seed layer (copper layer), 3: Circuit, 4: Noble metal layer, 10: Circuit board.

Claims

1. An etchant that selectively etches the copper layer of a workpiece containing a noble metal layer with a metal having a lower ionization tendency than copper, in which a copper layer coexists. The etchant contains: copper ions; Selected from one or more nitrogen-containing compounds in the group consisting of heterocyclic compounds having two or more nitrogen atoms in the ring and compounds containing amino groups having eight or fewer carbon atoms; Polyalkylene glycol; and halide ions; The aforementioned etchant contains 0.0005% to 7% by weight of polyalkylene glycol. It contains halide ions ranging from 1 ppm to 250 ppm.

2. The etchant according to claim 1, wherein the halide ion is at least one selected from the group consisting of chloride ions and bromide ions.

3. The etchant according to claim 1 or 2, wherein the pH is above 6.0 and below 8.

0.

4. The etchant according to claim 1 or 2, comprising 0.5% to 10.0% by weight of the aforementioned copper ions.

5. The etchant according to claim 1 or 2, comprising 1.0% to 30% by weight of the aforementioned nitrogen-containing compound.

6. The etchant according to claim 1 or 2, wherein it does not contain organic acids or contains more than 0% by weight but less than 7% by weight of organic acids.

7. The etchant according to claim 1 or 2, wherein the aforementioned nitrogen-containing compound is an imidazole.

8. The etchant according to claim 1 or 2, wherein the aforementioned polyalkylene glycol is polyethylene glycol.

9. A method for manufacturing a circuit board, comprising the following steps: using an etchant according to any one of claims 1 to 8, selectively etching a copper layer of a workpiece containing a noble metal layer with a metal having a lower ionization tendency than copper, in which a copper layer coexists, to form a circuit.

10. The method for manufacturing a circuit board according to claim 9, wherein the aforementioned noble metal layer is a layer containing gold.

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