Pretreatment cleaning agent for electroless plating and method for forming electroless plating using the same

Abstract

To provide a pretreatment cleaning agent for electroless plating and a method for forming electroless plating using the same that eliminate the need of surface roughening to a substrate with a strong acid such as a chromic acid or permanganic acid, can perform cleaning of the surface of a substrate and coupling treatment at the same time, and can form metal plating having a flat contact surface to a substrate.SOLUTION: A pretreatment cleaning agent for electroless plating includes an inorganic alkali, a cleaning agent including a surfactant, and a silane coupling agent and can perform cleaning of the surface of a substrate and coupling treatment at the same time.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pretreatment cleaner for electroless plating and a method for forming electroless plating using the same, and more particularly to a pretreatment cleaner for electroless plating that can form metal plating with a flat contact surface with a substrate, and a method for forming electroless plating using the same. [Background technology]

[0002] Printed wiring boards are made by forming a metal layer of a circuit pattern on the surface of an insulating substrate. In recent years, with the demand for smaller and lighter electronic products, there has been a demand for printed wiring boards (films) with more layers and finer circuit wiring. Conventionally, electroless plating methods for through holes and blind via holes have been proposed as methods for producing fine wiring circuits. Known methods involve forming a conductive seed layer on an insulating substrate by electroless copper plating or electroless nickel plating using a palladium catalyst. These methods involve surface treatment (surface roughening) using a strong chemical such as permanganate, known as desmear roughening, to ensure adhesion between the substrate and the copper plating film. This is done to utilize the anchor effect to ensure adhesion between the insulating substrate and the plating film.

[0003] [Prior art documents] [Patent documents]

[0004] [Patent Document 1] WO2020-003880 publication Summary of the Invention [Problem to be solved by the invention]

[0005] However, cleaning the substrate surface and applying the metal catalyst to the surface require complex processes, and there is a need to simplify the process. In addition, due to environmental concerns, there is a need to avoid the use of organic solvents such as strong acids. Furthermore, in some technical fields, roughening the metal surface is undesirable. In the technical field of circuit boards for high-speed communication (high frequency), the unevenness of the metal substrate causes skin transmission loss. Therefore, for example, in the electroless plating process used in manufacturing high-frequency electrical circuit boards, it is desirable to form metal plating with a smooth contact surface with the substrate. The problem to be solved by the present invention is to provide a pretreatment cleaner for electroless plating that can perform a coupling treatment simultaneously with cleaning of the surface of a substrate, without requiring surface roughening with a strong acid such as chromic acid or permanganic acid, and that can form a metal plating with a flat contact surface with the substrate, and a method for forming an electroless plating using the same. [Means for solving the problem]

[0006] The present invention relates to the following. <1> A cleaning agent containing an inorganic alkali and a surfactant, and a silane coupling agent, A pre-treatment cleaner for electroless plating that can simultaneously clean the surface of synthetic resin or glass substrates and perform coupling treatment. <2> The cleaning agent according to <1>, which is used in producing high-frequency electric circuit boards. <3> The cleaning agent according to <1> or <2>, wherein the silane coupling agent has an amino group as a functional group. <4> The cleaning agent according to <2> or <3>, wherein the silane coupling agent is contained in an amount of 0.5 to 4 mass % based on the total mass of the cleaning agent. <5> The cleaning agent according to <2> or <3>, wherein the silane coupling agent is contained in an amount of 0.8 to 2 mass % based on the total mass of the cleaning agent. <6> The cleaning agent according to <2> or <3>, wherein the alkali is NaOH, KOH, or a silicate. <7> The cleaning agent according to <2> or <3>, further comprising a chelating agent, wherein the chelating agent is an alkali salt of phosphoric acid or phosphonic acid. <8> The cleaning agent according to <2> or <3>, wherein the surfactant has a surface tension of 30 mN / m or less. <9> The cleaning agent is a mixture of potassium silicate aqueous solution or sodium silicate aqueous solution and metasilicate ions (SiO3 2- ) and hydroxide ions (OH - ) and potassium ions (K + ) or sodium ion (Na + The cleaning agent according to <2> or <3>, comprising: <10> The cleaning agent according to <2> or <3>, wherein the base material is formed of a synthetic resin selected from the group consisting of polyimide resin (PI), epoxy resin (EP), fluororesin (FP), cycloolefin resin (COP), polyphenylene ether resin (PPEP), and liquid crystal polymer (LCP). <11> A method for forming an electroless plating layer on the surface of a synthetic resin or glass substrate, the method comprising: a cleaning and coupling step of immersing the substrate in a cleaning agent containing an inorganic alkali, a surfactant, and a silane coupling agent to simultaneously clean and couple the substrate; a metal catalyst supporting step of immersing the substrate that has been subjected to the cleaning and coupling treatment in a solution containing a metal catalyst; and a plating step of immersing the substrate, on which the metal catalyst has been supported, in a plating bath containing metal ions to plate the surface of the substrate with metal. <12> The method for forming an electroless plating according to <11>, wherein the substrate is formed from a synthetic resin selected from the group consisting of polyimide resin (PI), epoxy resin (EP), fluororesin (FP), cycloolefin resin (COP), polyphenylene ether resin (PPEP), and liquid crystal polymer (LCP). <13> The method for forming an electroless plating according to <11> or <12>, wherein after the cleaning and coupling step, the substrate is rinsed and dried, and then the metal catalyst supporting step is performed on the substrate, and / or after the metal catalyst supporting step, the substrate is rinsed and dried, and then the plating step is performed on the substrate. <14> The method for forming an electroless plating film according to <11> or <12>, wherein the surface of the substrate is made hydrophilic before the washing and coupling step. <15> A plated molded body formed by the method for forming an electroless plating according to <11> or <12>. <16> The plated body according to <11> or <12>, which is a high-frequency electric circuit board. [Effects of the Invention]

[0007] The present invention provides a pretreatment cleaner for electroless plating that can perform a coupling treatment simultaneously with cleaning of the surface of a substrate, without requiring surface roughening with a strong acid such as chromic acid or permanganic acid, and can form a metal plating with a flat contact surface with the substrate, as well as a method for forming an electroless plating using the same. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a conceptual diagram of a primer layer formed on the surface of a synthetic resin substrate. [Figure 2] 2A and 2B are diagrams showing the reaction mechanism of a silane coupling agent. [Figure 3] FIG. 3 is a conceptual diagram of surface modification of polyimide resin. [Figure 4] FIG. 4 is a chart showing the modified state of the sample surface using infrared spectroscopy (FTIR). [Figure 5] Figure 5A is a photograph showing the state of the copper plating layer formed on the surface of the sample, and Figure 5B is a diagram summarizing the sample preparation conditions. [Figure 6] FIG. 6 is a photograph showing the effect of the wettability of the cleaning agent on each substrate. [Figure 7] FIG. 7 is a diagram showing the results of an investigation into the thickness of the copper plating film. [Figure 8] FIG. 8A is a graph showing the electroless copper plating film formation rate for polyimide, FIG. 8B is a graph showing the electroless copper plating film formation rate for a glass plate, and FIG. 8C is a graph showing the film formation conditions for electroless copper plating. [Figure 9] FIG. 9 shows an observation photograph after simple pressing. [Figure 10] Figure 10A is a photograph showing the state of the copper plating layer formed on the surface of the glass plate, and Figure 10B is a photograph showing the effect of the coupling agent. [Figure 11] Figure 11A is a photograph showing the state of the copper plating layer formed on the surface of the sample, and Figure 11B is a diagram summarizing the sample preparation conditions. [Figure 12] FIG. 12 is a photograph showing the effect of the coupling agent concentration on the copper plating formed on the surface of the sample. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described below with reference to embodiments, but the present invention is not limited to the following embodiments.

[0010] [Pre-treatment cleaning agent for electroless plating] The present invention relates to a pretreatment cleaner for electroless plating, which contains (A) a cleaner containing an inorganic alkali and a surfactant, and (B) a silane coupling agent. Figure 1 is a conceptual diagram of a primer layer formed on the surface of a synthetic resin substrate. When the cleaning agent of the present invention is applied to the substrate, it spreads widely without roughening the surface, cleaning the substrate surface and simultaneously performing a coupling treatment. Then, by further applying silver particles as a reaction catalyst, a primer layer is formed on the substrate, with the silver particles adsorbed via the coupling agent. Then, by performing electroless plating, a plating layer of copper or other metals is formed starting from the silver particles in the primer layer. The cleaning agent of the present invention has extremely low surface tension and good wetting properties, allowing it to penetrate and clean even small via holes. Furthermore, since it does not roughen the substrate surface, it can form a flat metal plating layer on the contact surface with the substrate, making it suitable for use in the manufacture of high-frequency electrical circuit boards. It can form a flat plating film while maintaining adhesive strength.

[0011] (Issues and solutions based on reaction mechanisms) 2A and 2B are diagrams showing the reaction mechanism of a silane coupling agent. The coupling effect will be explained in more detail with reference to examples of silane coupling agents in FIGS. 2A and 2B. Coupling agents are compounds that bond materials with different properties, primarily inorganic and organic materials. Metal coupling agents form strong covalent or ionic bonds on the metal surface and also have bonding sites on the polymer side. Silane coupling agents and polymer coupling agents, in particular, are known to exhibit coupling effects as coupling agents for metal adhesion, although they have problems with film-forming properties. Polycarboxylic acid coupling agents are also known to exhibit coupling effects by forming ionic bonds between their carboxyl groups and the oxide layer on the metal surface and stabilizing this with polymer adsorption.

[0012] As shown in Figure 2A, in the reaction mechanism, the silanol groups generated by the hydrolysis reaction are adsorbed onto the inorganic material (metal surface) and oriented by hydrogen bonding. A condensation reaction then occurs through a dehydration reaction, forming a strong covalent bond with the inorganic material (target reaction). However, as shown in Figure 2B, once the silanol groups are generated by hydrolysis, they undergo a self-condensation reaction within the solution, and there are concerns that this side effect of promoting bonding between effective coupling agents may shorten the solution's lifespan. The present inventors have discovered that, as a countermeasure for suppressing the side reaction of self-condensation, silanol groups become silanolate ions under basic conditions, resulting in resonance stabilization and making self-condensation less likely to occur. In addition, the presence of interfering ions in the detergent beforehand can suppress the self-condensation reaction, thereby further stabilizing the detergent.

[0013] (Prescription) Component (A) The alkaline agent is not particularly limited and various agents can be used, but it is preferable to use NaOH or KOH.

[0014] Although various surfactants can be used without any particular limitation, it is preferable to use a surfactant having a surface tension of 30 mN / m or less. For example, it is preferable to use a polyoxyalkylene alkyl ether. Specific examples include EMALEX 640 (Nihon Emulsion Co., Ltd.), EMALEX 130 (Nihon Emulsion Co., Ltd.), EMALEX 120 (Nihon Emulsion Co., Ltd.), EMALEX 115 (Nihon Emulsion Co., Ltd.), Adekatal SO-145 (ADEKA Corporation), Noigen TDS-80 (Dai-ichi Kogyo Seiyaku Co., Ltd.), Noigen XL-80 (Dai-ichi Kogyo Seiyaku Co., Ltd.), Noigen XL-60 (Dai-ichi Kogyo Seiyaku Co., Ltd.), Noigen SD-70 (Dai-ichi Kogyo Seiyaku Co., Ltd.), Noigen SD-60 (Dai-ichi Kogyo Seiyaku Co., Ltd.), and Noigen EA-137. (Dai-ichi Kogyo Seiyaku Co., Ltd.), ADEKA NOL B-4009 (ADEKA Corporation), FINESURF 9161 (Aoki Oil & Fat Industries Co., Ltd.), ADEKA NOL AS-054C (Dai-ichi Kogyo Seiyaku Co., Ltd.), FINESURF D-1305 (Aoki Oil & Fat Industries Co., Ltd.) One of these may be used alone, or two or more may be used in combination.

[0015] The component (A) may further contain a chelating agent. Various chelating agents can be used without particular limitation, but it is preferable to use an alkali salt of phosphoric acid or phosphonic acid. The alkali salt of phosphoric acid or phosphonic acid is preferably an alkali salt of etidronic acid. Specifically, tripotassium phosphate, potassium pyrophosphate, sodium tripolyphosphate, sodium tetraphosphate, sodium hexametaphosphate, and potassium etidronate can be used. One of these may be used alone, or two or more may be used in combination.

[0016] (B) Component The coupling agent is not particularly limited and various types can be used, but it is preferable to use a silane coupling agent, and more preferably to use a silane coupling agent having an amino group as a functional group (manufactured by Shin-Etsu Chemical Co., Ltd., trade names "KBE-903" or "X-12-972F")

[0017] The content of the coupling agent is preferably 0.5 to 4 mass %, more preferably 0.8 to 2 mass %, based on the total mass of the coupling agent-containing cleaner.

[0018] The coupling agent-containing detergent is a mixture of potassium silicate aqueous solution or sodium silicate aqueous solution and metasilicate ions (SiO3 2- ) and hydroxide ions (OH - ) and potassium ions (K + ) or sodium ion (Na + ) is preferably contained in the cleaning agent containing the coupling agent, because the presence of interfering ions inhibits self-condensation of silanol groups, improving the stability of the cleaning agent containing the coupling agent and extending its life.

[0019] (base material) The substrate can be made of synthetic resins such as polyimide resin (PI), epoxy resin (EP), fluororesin (FP), cycloolefin resin (COP), polyphenylene ether resin (PPEP), and liquid crystal polymer (LCP). Among these, polyimide resin is preferred. This is because the cleaning agent can easily wet and spread on the substrate even without making the surface hydrophilic, for the following reasons: Figure 3 is a conceptual diagram of surface modification of polyimide resin. Polyimide is a substance with imide rings in its molecular structure, synthesized by dehydration condensation. Therefore, it is easily hydrolyzed by alkali in cleaning agents, forming carboxyl groups on the surface, making it hydrophilic. As a result, cleaning agents easily wet and spread on substrates made of polyimide resin. When using a substrate made of a synthetic resin other than polyimide resin, it is preferable to hydrophilize the surface of the substrate before pretreating it with a cleaning agent. This improves the wettability of the surface and makes it easier for the cleaning agent to spread. The method of hydrophilization is not particularly limited, but examples include UV treatment, corona discharge treatment, and plasma treatment.

[0020] Furthermore, the base material is not limited to organic materials such as synthetic resins, and inorganic materials such as glass may also be used, as long as a plating layer can be formed on the base material by electroless plating.

[0021] The metal can be any metal that can be used for electroless plating without any particular limitation, and examples thereof include gold, silver, copper, nickel, tin, chromium, and NiCr. Of these, copper is preferred.

[0022] [Method for forming electroless plating] The method for forming electroless plating will be described below, taking as an example a polyimide substrate and copper as the metal, while also explaining the effects of the cleaning agent. (i) A polyimide substrate, (A) a cleaning agent containing an inorganic alkali and a surfactant, and (B) a cleaning agent containing a silane coupling agent are prepared. (b) The substrate is immersed in the prepared cleaning agent. This spreads the cleaning agent over a wide area of ​​the substrate surface. Cleaning and coupling treatment of the substrate surface are performed simultaneously. The adhering cleaning agent is removed by rinsing. It is preferable to then dry the substrate. (c) Next, the substrate that has been washed and coupled is immersed in a solution containing silver as a metal catalyst. As a result, a primer layer is formed on the substrate, with silver particles adsorbed via the coupling agent, as shown in Figure 1. It is preferable to then dry the substrate. The silver-containing solution can be, for example, colloidal particles of silver nanoparticles (particle size approximately 12 nm), as described in the Examples section below. (ii) The substrate carrying the metal catalyst is immersed in a plating bath containing copper ions as the metal ion, and electroless plating is performed, whereby a copper plating layer grows starting from the silver particles in the primer layer, forming a plating film. Through the above steps, a plated molded product with a uniform plating film is manufactured. After immersing the sample in each solution in steps (b) and (c), excess solution remaining on the sample surface is removed by rinsing.

[0023] The electroless plating method described above allows the cleaning agent to wet and spread to the interior of small via holes due to its excellent wettability. Furthermore, a uniform primer layer is formed on the substrate surface without roughening the substrate surface, resulting in a metal plating layer with a flat contact surface with the substrate while maintaining adhesive strength. For example, when a UV laser is used for small via processing, smear generation is minimal, and smear cleaning is performed using plasma treatment. While this method can make the substrate hydrophilic, it does not firmly retain the metal catalyst for plating metal. Therefore, the surface is roughened and the metal catalyst is held in place using an anchor method. Even if the substrate is not dried after steps (b) or (c), a plating film similar to that formed when these steps are performed can be formed, thereby simplifying the work process.

[0024] (Other embodiments) As described above, the present invention has been described by way of the embodiments, but the descriptions and drawings that form part of this disclosure should not be understood as limiting the present invention. Various alternative embodiments, examples, and operating techniques will become apparent to those skilled in the art from this disclosure.

[0025] In the electroless plating method, a polyimide substrate was used to manufacture the plated molded product. However, substrates made of other synthetic resins may also be used. In such cases, it is preferable to hydrophilize the surface of the substrate beforehand. In the electroless plating method, plated molded products were manufactured by a wet method. However, a method in which the substrate is dried after the washing and coupling step and / or the metal catalyst supporting step (dry method) may also be used. The dry method tends to produce higher plating film bond strength than the wet method, so from the viewpoint of film bond strength, the dry method is preferred. The dry method is particularly preferred when the substrate is glass. As such, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention-specifying matters according to the scope of the claims that are appropriate from the above description. [Example]

[0026] [Example 1] [Preparation of cleaning agent for electroplating pretreatment] (a) A 10% aqueous solution of a cleaning agent (manufactured by Yokohama Oil & Fat Industries Co., Ltd., product name "HDM-1") containing inorganic alkali, chelating agent, and surfactant (multiple nonionic surfactants) was prepared as the cleaning agent. A silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBE-903") having an amino group as a functional group was prepared as the coupling agent. A pretreatment cleaner for electroplating was prepared by adding a silane coupling agent to the cleaner so that the amount was 1% by mass based on the total mass. In order to suppress the self-condensation of the hydrolyzed product, a potassium silicate aqueous solution and metasilicate ions (SiO3 2- ) and hydroxide ions (OH - ) and potassium ions (K + ) was confirmed to be included.

[0027] (b) A sample made of polyimide (manufactured by Toray DuPont Co., Ltd., polyimide film, registered trademark "Kapton 200EN") was immersed in the prepared cleaning agent for 10 minutes. It was then thoroughly rinsed with ion-exchanged water. The rinsing removed excess coupling agent, leaving only the molecular layer oriented and adsorbed on the surface by hydrogen bonding. It was then left to air dry for 1 hour.

[0028] (c) The sample was immersed in a solution containing silver ion particles (7 g / L) for 5 minutes, then thoroughly rinsed with ion-exchanged water and left to air dry for 1 hour. The silver ion solution used was colloidal silver nanoparticles (approximately 12 nm in diameter), which were prepared by reacting 0.1 mol / L of silver nitrate and sodium citrate with iron sulfate heptahydrate and water, and then centrifuging the resulting solution at 30,000 rpm.

[0029] (d) Next, the sample was immersed in a plating solution containing copper ions to plate the surface of the sample with copper.

[0030] [Example 2] The surface of the sample was copper-plated in the same manner as in Example 1, except that the sample was not dried. Specifically, the same cleaning solution as in Example 1 was prepared, and the polyimide sample was immersed in the cleaning solution for 10 minutes. The sample was then immersed in a solution (7 g / L) containing silver ion particles for 5 minutes. Thereafter, the surface of the sample was copper-plated.

[0031] [Comparative Example 1] Except for the fact that no coupling agent was added to the cleaning solution, copper plating was performed on the surface of the sample in the same manner as in Example 1. Specifically, the experiment was carried out according to the following procedure. (a) As a cleaning agent, a 10% aqueous solution of a cleaning agent (manufactured by Yokohama Oil & Fats Industries Co., Ltd., product name "HDM-1") containing inorganic alkali, a chelating agent, and a surfactant (multiple nonionic surfactants) was prepared. (b) A polyimide sample was immersed in the prepared cleaning agent for 10 minutes, then thoroughly rinsed with ion-exchanged water, and left to air dry for 1 hour.

[0032] (c) The sample was immersed in a solution containing silver ion particles (7 g / L) for 5 minutes, then thoroughly rinsed with ion-exchanged water and left to air dry for 1 hour. (d) Next, the sample was immersed in a plating solution containing copper ions to plate the surface of the sample with copper.

[0033] [Surface modification evaluation] Experiments similar to steps (a) and (b) of Example 1 and Comparative Example 1 were conducted. The surface modification state of the obtained samples was analyzed by infrared spectroscopy (FTIR). The results are shown in Figure 4. The chart in Figure 4 shows, from top to bottom, (1) the substrate only, (2) the substrate treated with only the (A) cleaning agent (corresponding to the sample of Comparative Example 1), and (3) the substrate treated with the (A) cleaning agent and the (B) coupling agent (corresponding to the sample of Example 1). Comparing charts (1) and (2), in the case of (2), no modification of the sample surface was observed. On the other hand, comparing charts (1) and (3), in the case of (3), absorption waveforms were observed at positions corresponding to the alcohol, amine, and saturated aliphatic (-CH2CH2OH) in the coupling agent. This result confirmed that when the sample was cleaned with a cleaning agent containing a coupling agent, the coupling agent remained on the sample surface. This confirmed that cleaning the substrate with the prepared cleaning agent in step (b) resulted in the formation of a coupling layer on the surface of the substrate.

[0034] [Appearance evaluation] The conditions of the plating films obtained in Example 1, Example 2, and Comparative Example 1 were visually observed. Photographs of the appearance of the obtained samples are shown in Figure 5A. From left to right in Figure 5A, Comparative Example 1 (no coupling agent, rinsed, and dried), Example 1 (coupling agent included, rinsed, and dried), and Example 2 (coupling agent included, rinsed, and not dried) are shown. Figure 5B outlines the preparation conditions for each sample.

[0035] Copper plating was formed on the surface of the sample in Example 1. In Example 2, in which the sample was not dried, copper plating was also formed on the surface of the sample, similar to Example 1. On the other hand, in Comparative Example 1, no copper plating was formed on the surface of the sample. These experimental results suggest that using a cleaning agent containing a coupling agent allows the coupling agent to spread widely over the sample surface, supporting (orienting) the silver catalyst on the sample via the coupling agent to form a primer layer, and that copper ions then grow from the silver catalyst in the primer layer, resulting in copper plating on the sample surface.

[0036] [Simple evaluation of copper plating adhesion] When the adhesive strength was measured in accordance with the copper clad sheet test method for printed wiring boards of the Japanese Industrial Standards (JIS C6481-1996), the adhesion strength of the plating film was confirmed to be 1.2 kN / m or more.

[0037] [Wettability evaluation] Figure 6 is a photograph showing the effect of the wettability of cleaning agents on substrates made of various synthetic resins. Plating films were formed on polyimide substrates in the same manner as in Example 1. Except for using substrates made of liquid crystal polymer (LCP) and glass epoxy resin (FR4), plating films were formed on the substrates in the same manner as in Example 1. The appearances of the obtained samples are shown in Figure 6. From the left in Figure 6, plating films formed on substrates made of polyimide, LCP, and FR4 are shown. A uniform plating film was formed on the polyimide substrate. On the other hand, the plating film was sparsely formed on the LCP and FR4 substrates. From these results, it is believed that the cleaning agent spread widely on the polyimide substrate, forming a wide and even primer layer, resulting in a clean and uniform plating film. On the other hand, on the LCP and FR4 substrates, the cleaning agent did not spread widely on the substrate, forming a sparse primer layer, which is thought to be why the plating film was also sparsely formed. From these findings, it can be said that when the substrate is polyimide, there is no need to perform hydrophilic treatment, but when the substrate is LCP or FR4, it is preferable to perform a hydrophilic treatment on the surface of the substrate in advance.

[0038] [Copper plating thickness investigation] A polyimide substrate (manufactured by DuPont-Toray Co., Ltd., polyimide film, registered trademark "Kapton 200EN") was prepared. Then, a plating film was formed on the substrate so that the plating area was 75 × 15 mm using the same method as in Example 1. The substrate was then immersed in the plating solution, and the thickness of the plating film was calculated from the increase in weight of the plating film at each elapsed time from the start of plating. Figure 7 shows photographs of the appearance of the resulting plating film. In Figure 7, the photographs show the plating film after 5 minutes, 10 minutes, and 15 minutes, respectively, starting from the top. The thickness results for the resulting plating film are shown below. After 5 minutes: Weight increase 2.1 mg (film thickness 0.104 μm) After 10 minutes: Weight increase 5.1 mg (film thickness 0.253 μm) After 15 minutes: Weight increase 9.8 mg (film thickness 0.487 μm)

[0039] The electroless copper plating film formation rate is shown in Figure 8. It was confirmed that there is a correlation between the copper plating thickness survey results and the electroless copper plating film formation rate in Figure 8.

[0040] Figure 9 shows a photograph of the sample after simple pressing. Only the sample treated with the base cleaner, which does not contain a coupling agent, shows a different color in the area immersed in the treatment solution. This difference in color is due to the color change caused by thermal oxidation of the copper plate (Yuki Haijima, Ayaka Matsumura, et al.: Surface Treatment, Vol. 59, No. 12, 2008). It was confirmed that the area with the adsorbed coupling agent was uniformly protected from oxidation. This suggests that the oriented adsorption of the coupling agent was uniformly attached.

[0041] [Example 3] In addition to substrates made of synthetic resin, experiments were also conducted to determine whether electroless plating films could be formed on the surfaces of inorganic materials such as glass. The surface of the sample was copper-plated in the same manner as in Example 1, except that the substrate was replaced from polyimide to a glass plate. Specifically, the same cleaning solution as in Example 1 was prepared, and the sample consisting of a glass plate was immersed in the cleaning solution for 10 minutes. The sample was then immersed in a solution (7 g / L) containing silver ion particles for 5 minutes. Thereafter, the surface of the sample was copper-plated.

[0042] Comparative Example 2 The surface of the sample was copper plated in the same manner as in Example 3, except that no coupling agent was added to the cleaning solution.

[0043] FIG. 10A is a photograph showing the state of copper plating formed on the surface of the glass plate in Example 3. As shown in FIG. 10A, copper plating was also formed on the surface of the glass plate. On the other hand, as shown in FIG. 10B, no copper plating layer was formed in Comparative Example 2, which did not contain a coupling agent. Comparing Example 3 and Comparative Example 2, it was confirmed that the coupling agent contributed to the formation of copper plating even when the substrate was replaced from polyimide to a glass plate.

[0044] We also conducted experiments to determine whether rinsing and drying have any effect when the substrate is made of inorganic materials such as glass. [Example 4] The surface of the sample was copper-plated in the same manner as in Example 2, except that the substrate was replaced from polyimide to a glass plate. Specifically, the same cleaning solution as in Example 1 was prepared, and the sample consisting of a glass plate was immersed in the cleaning solution for 10 minutes. The sample was then immersed in a solution (7 g / L) containing silver ion particles for 5 minutes. Thereafter, the surface of the sample was copper-plated.

[0045] [Appearance evaluation] The conditions of the plating films obtained in Example 3, Example 4, and Comparative Example 2 were visually observed. Photographs of the appearance of the obtained samples are shown together in Figure 11A. To illustrate the influence of differences in substrate, Example 1 and Comparative Example 1, in which the substrate is polyimide, are also shown in Figure 11A for reference. In Figure 11A, from left to right, the samples are Example 1, Comparative Example 1 (containing no coupling agent), Example 4, Comparative Example 2, and Example 3. Figure 11B outlines the preparation conditions for each sample.

[0046] Copper plating was formed on the surface of the glass plate in both Examples 3 and 4. On the other hand, no copper plating was formed in Comparative Example 2, which did not contain a coupling agent. When the samples of Examples 3 and 4 were washed with water, the copper plating of Example 3 did not peel off under water pressure, but the copper plating of Example 4 did peel off under water pressure. This indicates that drying results in copper plating with higher peel strength being formed on the surface of the sample.

[0047] [Reference example] [Concentration evaluation] Pretreatment cleaners for electrolytic plating were prepared in the same manner as in Example 1 so that the coupling agent concentrations were 0 mass%, 0.2 mass%, 0.5 mass%, 0.8 mass%, 1 mass%, 2 mass%, and 4 mass%, respectively. Thereafter, copper plating was performed on the surface of the polyimide sample in the same manner as in Example 1. The obtained results are summarized in Figure 12. It was confirmed that good copper plating was formed at 0.5 mass% or more. In particular, it was confirmed that extremely good copper plating was formed at 0.8 mass% to 2 mass%. [Industrial Applicability]

[0048] When forming a metal plating film on a synthetic resin substrate, it is common to use the surface roughness of the metal to create an anchoring effect to ensure adhesive strength between the two. However, this coupling mechanism suggests that an oriented adsorption layer is important, which in turn suggests that molecular orientation is important. This is a molecular bond with a strong chemical bond. We hope that this will be of some help in overcoming the transmission loss caused by metal surface roughness when developing high-frequency electrical circuits. Because it does not use strong acids and existing cleaning equipment can be used as is, it is significant that this cleaning agent makes it possible to ideally achieve cleaning and coupling treatment in a one-step process.

Claims

1. a cleaning agent containing an inorganic alkali and a surfactant; a silane coupling agent, A pre-treatment cleaner for electroless plating that can simultaneously clean the surface of synthetic resin or glass substrates and perform coupling treatment.

2. 2. The cleaning agent according to claim 1, which is used in the production of high-frequency electric circuit boards.

3. 2. The cleaning agent according to claim 1, wherein the silane coupling agent has an amino group as a functional group.

4. 4. The cleaning agent according to claim 2, wherein the silane coupling agent is contained in an amount of 0.5 to 4 mass % based on the total mass of the cleaning agent.

5. 4. The cleaning agent according to claim 2, wherein the silane coupling agent is contained in an amount of 0.8 to 2 mass % based on the total mass of the cleaning agent.

6. 4. The cleaning agent according to claim 2, wherein the alkali is NaOH, KOH, or a silicate.

7. Further comprising a chelating agent, 4. The cleaning agent according to claim 2, wherein the chelating agent is an alkali salt of a phosphoric or phosphonic acid.

8. 4. The cleaning agent according to claim 2, wherein the surfactant has a surface tension of 30 mN / m or less.

9. The cleaning agent contains a mixture of an aqueous potassium silicate solution or an aqueous sodium silicate solution and metasilicate ions (SiO ３ ２－ ) and hydroxide ions (OH － ) and potassium ions (K ＋ ) or sodium ion (Na ＋ 4. The cleaning agent according to claim 2 or 3, comprising:

10. 4. The cleaning agent according to claim 2 or 3, wherein the base material is formed from a synthetic resin selected from the group consisting of polyimide resin (PI), epoxy resin (EP), fluororesin (FP), cycloolefin resin (COP), polyphenylene ether resin (PPEP), and liquid crystal polymer (LCP).

11. A method for forming an electroless plating layer on a surface of a substrate made of synthetic resin or glass, comprising: a cleaning / coupling step of immersing the substrate in a cleaning agent containing an inorganic alkali, a surfactant, and a silane coupling agent to simultaneously perform cleaning and coupling treatment of the substrate; a metal catalyst supporting step of immersing the substrate that has been subjected to the washing and coupling treatment in a solution containing a metal catalyst; a plating step of immersing the substrate carrying the metal catalyst in a plating bath containing metal ions to form a metal plating on the surface of the substrate.

12. 12. The method for forming an electroless plating according to claim 11, wherein the substrate is formed from a synthetic resin selected from the group consisting of polyimide resin (PI), epoxy resin (EP), fluororesin (FP), cycloolefin resin (COP), polyphenylene ether resin (PPEP), and liquid crystal polymer (LCP).

13. After the washing and coupling step, the substrate is rinsed and dried, and then the metal catalyst supporting step is performed on the substrate; and / or 13. The method for forming an electroless plating film according to claim 11, wherein after the metal catalyst supporting step, the substrate is rinsed and dried, and then the plating step is carried out on the substrate.

14. The method for forming an electroless plating film according to claim 11 or 12, wherein the surface of the substrate is made hydrophilic before the cleaning and coupling step.

15. A plated molded body formed by the method for forming an electroless plating according to claim 11 or 12.

16. 13. The plated body according to claim 11, wherein the plated body is a high-frequency electric circuit board.

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