JP2010270389A - Plating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plating method which can inexpensively smoothening the surface of a resin base material after plating even if a projecting part exists upon forming the resin base material. <P>SOLUTION: The plating method comprises: a stage S2 where the surface of the resin base material 11 having an unsaturated bond is subjected to oxidation treatment; a stage S3 where the surface of the base material after the oxidation treatment is brought into contact with an alkali solution so as to be a hydroxide ion concentration of ≥5 mol/L, and the surface of the base material is subjected to smoothing treatment; and a stage S4 where the surface of the base material after the smoothing stage is subjected to electroless plating treatment. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a plating method for performing electroless plating on the surface of a resin substrate, and more particularly to a plating method that can smooth the plating surface.

  Conventionally, since metal properties such as high conductivity and metallic luster can be imparted while reducing the weight of the member, the surface of a resin base material made of a polymer resin has been coated with a metal film. . As an example of the metal plating process, an electroless plating process or a dry plating process is performed.

  The electroless plating treatment is a treatment for forming a metal film on the surface of a resin base material of a polymer resin that is an electrical insulator by chemically reducing and precipitating metal ions in a solution. In this treatment, as a pretreatment, after the resin material is treated with ozone water, it is treated with an alkali treatment liquid containing a surfactant (for example, see Patent Document 1), or etched with chromic acid or permanganic acid. Has been proposed to do. By such treatment, it is possible to improve the plating adhesion on the substrate surface and the adhesion strength of the coating.

JP 2002-309377 A

  However, when the plating process is performed by the method described above, convex portions having a rough width of several tens of μm and a height of several μm may be formed on the plating surface. For example, as shown in FIG. 7A, a convex portion P1 may occur on the surface when the resin base material 91 is molded. However, even when the ozone water treatment is performed, the convex portion P1 is oxidized but not removed, and the convex portion P1 of the resin base material 91 remains on the surface of the metal coating 93, and on the surface of the metal coating 93. The convex part P3 will be formed.

  In such a case, the surface of the resin base material at the time of molding may be smoothed, but the resin molding conditions (raw materials, molding mold, molding speed, etc.) must be strictly adjusted, and the number of manufacturing steps There is a risk that the manufacturing cost will increase.

  Moreover, as shown in FIG.7 (b), even if there is no convex part in the surface of the resin base material 91 at the time of shaping | molding, the weak layer 91a may be formed in the surface layer of the resin base material 91 at the time of shaping | molding. is there. When the metal coating is applied, a compressive stress (plating stress) acts on the fragile layer 91a, and a part of the fragile layer 91a swells into the convex portion P2 with respect to the resin base material 91. Protrusions P <b> 3 may also be formed on the surface of the film 93.

  Moreover, as shown in FIG.7 (c), when the ozone water process is performed on the surface of the resin base material 91 after a shaping | molding, the weak layer 91b may be formed by degradation by the radical at the time of an ozone process. is there. Due to the fragile layer 91b, a convex portion may be formed on the surface of the metal film 93 for the same reason as shown in FIG.

  Moreover, as shown in FIG.7 (d), if the etching process is performed after the shaping | molding of the resin base material 91, the convex part of the resin base material 91 will be removed. However, since the surface of the resin base material 91 is roughened by etching, when trying to coat a metal coating with higher smoothness, the plating solution containing a leveling agent is used to reduce the thickness of the metal coating to several. The thickness must be increased to 10 μm, which increases the number of steps and is disadvantageous in terms of cost. Although the leveling agent is consumed together with the plating treatment, the management range of the leveling agent to be contained is narrow, and the management including the replenishment of the leveling agent is not easy. In addition, chromic acid or permanganic acid must be used as an etching solution, and use in consideration of environmental resistance is required.

  The present invention has been made in view of the above-described problems, and the object of the present invention is to smooth the surface of the metal coating at a low cost even if the resin substrate has a convex portion or a fragile layer. An object of the present invention is to provide a plating method capable of performing

  In order to solve the above-mentioned problems, the inventors have intensively studied, and as a pretreatment for the plating treatment on the surface of the resin base material, an alkali solution having a high hydroxide ion concentration (high pH) (strong alkali solution) As a result, it is possible not only to preferentially remove the convex portions on the surface of the resin base material, but also to remove the fragile layer that causes the convex portions on the surface of the resin base material. Obtained knowledge.

  The present invention is based on the inventors' new knowledge, and the plating method according to the present invention includes a step of oxidizing a substrate surface of a resin substrate having an unsaturated bond, and the oxidation treatment. A step of smoothing the surface of the resin substrate by bringing an alkali solution having a hydroxide ion concentration of 5 mol / L or more into contact with the subsequent substrate surface, and the substrate surface after the smoothing treatment, And a step of performing an electroless plating process.

  According to the present invention, the surface of the resin substrate after the oxidation treatment is brought into contact with the alkali solution having the hydroxide ion concentration, thereby causing the protrusions and the protrusions of the resin substrate formed after molding. In addition to removing the fragile layer, the fragile layer on the surface of the resin substrate formed by oxidation treatment can be removed thereafter. Thereby, the surface of the smoothed metal film (plating film) can be obtained by the electroless plating process.

  That is, when the hydroxide ion concentration is less than 5 mol / L, the convex portion and the fragile layer of the resin base material cannot be sufficiently removed, and as a result, the metal film after the electroless plating treatment Protrusions are formed on the surface of the film. In addition, since the conventional alkaline solution containing a surfactant is intended to enhance the wettability of the substrate surface and attach a surfactant for adsorbing the metal catalyst, the hydroxide ion concentration is The concentration was lower than that of the smoothing treatment. Therefore, the resin base material is not smoothed.

  Examples of the oxidation treatment include ozone treatment, ultraviolet treatment, plasma treatment, treatment using various oxidizing agents such as permanganic acid and chromic acid, and the like. However, the oxidation treatment is more preferably an ozone treatment. According to the present invention, the ozone treatment can suitably oxidize the base material surface and the surface layer of the resin base material without roughening the surface of the resin base material as compared with other oxidation treatments.

  Examples of the ozone treatment include ozone water treatment in which the substrate surface of the resin base material is brought into contact with ozone water, and ozone gas treatment in which the substrate surface of the resin base material is brought into contact with ozone gas. Treatment is more preferred.

  In the case of ozone water treatment, not only the oxidation of the resin base material by ozone but also the oxidation of the resin base material by hydroxy radicals contained in the ozone water may cause the resin base material to deteriorate. When it is performed, only the oxidation of the resin by ozone occurs, so that it is considered that the resin does not deteriorate.

  As the alkaline solution, the alkaline solution is preferably a solution containing an alkali metal hydroxide or a solution containing an alkaline earth metal hydroxide. For example, a solution containing an alkali metal hydroxide or a solution containing an alkaline earth metal includes a sodium hydroxide solution, a potassium hydroxide solution, a sodium carbonate solution, a sodium bicarbonate solution, a calcium hydroxide solution, or a hydroxide. Examples of the alkaline solution used in the plating method according to the present invention include, but are not particularly limited, as long as the solution can satisfy the hydroxide ion concentration. A sodium hydroxide solution, a potassium hydroxide solution, or a sodium carbonate solution is preferable. Among these, a sodium hydroxide solution is more preferable.

  According to the present invention, these solutions can be alkali solutions having the hydroxide ion concentration. In particular, a sodium hydroxide solution is more preferable because it allows the hydroxide ions to be easily subjected to the concentration condition.

  The resin base material used in the plating method according to the present invention is, for example, an ABS resin, AS resin, PS resin, AN resin, epoxy resin, PMMA resin, polyimide resin, polyphenyl sulfide as the resin having an unsaturated bond. Although resin etc. can be mentioned, More preferably, it is more preferable that a resin base material consists of ABS resin.

  The ABS resin is a resin containing butadiene particles and an AS resin that is a matrix resin of the butadiene particles. According to the present invention, in the oxidation treatment, the butadiene particles existing on the substrate surface layer are eluted and escape. Furthermore, the AS resin that is the matrix resin is oxidized. And since the oxidized AS resin on the surface of the base material swells and elutes by contacting with the alkaline solution, not only the convex portion of the resin base material but also the fragile layer of the resin base material can be removed. . As a result, a smooth metal film can be formed on the surface of the resin substrate.

  Furthermore, as a pretreatment of the electroless plating treatment in the plating method according to the present invention, a step of bringing an alkali solution containing a surfactant into contact with the treated surface after the smoothing treatment and attaching the surfactant to the substrate surface And a step of performing a catalyst adsorption treatment for adsorbing the metal catalyst.

  According to the present invention, by contacting an alkali solution containing a surfactant, the wettability of the surface of the resin substrate can be improved, and the surfactant can be suitably attached to the surface of the resin substrate. Here, the hydroxide ion concentration in the alkaline solution is sufficient as long as it improves the wettability of the surface of the resin substrate so as to attach the surfactant of the resin substrate. It is sufficiently lower than the hydroxide ion concentration of the alkaline solution in the smoothing treatment.

  In addition, examples of the plating material for performing such electroless plating treatment include copper and nickel, and particularly, if a metal film is formed on the surface of the resin base material by electroless plating. It is not limited. However, a more preferable metal catalyst is a palladium catalyst, and a plating material for performing electroless plating is nickel. The palladium catalyst is excellent in the adsorptivity with respect to the above-mentioned resin, and is rich in versatility. When nickel is formed, it is preferable from the viewpoint of adhesion and the like.

  According to the present invention, even if the resin substrate has a convex portion or a fragile layer, the surface of the metal coating can be smoothed at a low cost.

FIG. 1A is a flowchart for explaining each step of the plating method according to the present embodiment, and FIG. 1B is a diagram illustrating the process performed by the plating method shown in FIG. The schematic diagram of an electroplating material. 2A is a view showing a resin base material after molding, FIG. 2B is a view showing a resin base material after ozone water treatment, and FIG. 2C is a smooth view. The figure which showed the resin base material after a chemical conversion process. FIG. 3A is a view showing a resin base material in which convex portions or fragile layers are formed on the surface of the base material after molding, and FIG. 3B shows the resin base material after ozone water treatment. FIG. 3C is a diagram showing a resin base material that has been subjected to electroless plating treatment without performing alkali treatment on the surface of the base material after the ozone water treatment, and FIG. FIG. 3 is a diagram showing a resin base material that has been subjected to a smoothing treatment with strong alkali on the surface of the base material after the ozone water treatment, and FIG. 3E shows an electroless plating treatment on the surface after the smoothing treatment. The figure which showed the electroless-plating material. The figure which showed the relationship between the hydroxide ion density | concentration in the smoothing process process in Example 1 and Comparative Example 1, and the density of the convex part formed in a metal film. The figure which showed the relationship between the liquid temperature of the sodium hydroxide in the smoothing process process in the confirmation test 1, and the density of the convex part formed in a metal film. The figure which showed the relationship between the immersion time of the sodium hydroxide in the smoothing process process in the confirmation test 2, and the density of the convex part formed in a metal film. Fig.7 (a) is a figure for demonstrating the conventional plating process, FIG.7 (b) is a figure for demonstrating the plating process when a weak layer is formed at the time of shaping | molding of a base material. FIG.7 (c) is a figure for demonstrating the plating process when a weak layer is formed at the time of ozone water processing, and FIG.7 (d) is a figure for demonstrating the plating process after an etching.

  Below, with reference to drawings shown typically, it explains based on an embodiment of a plating treatment method to a resin substrate concerning the present invention. FIG. 1A is a flowchart for explaining each step of the plating method according to the present embodiment, and FIG. 1B is a diagram illustrating the process performed by the plating method shown in FIG. The electrolytic plating material is shown. FIG. 2 (a) shows the resin base material after molding, FIG. 2 (b) shows the resin base material after ozone water treatment, and FIG. 2 (c) shows the result after smoothing treatment. The resin base material is shown.

  First, as shown to Fig.1 (a), in step S1, a base material (resin base material) is shape | molded from resin which has unsaturated bonds, such as an ABS resin (molding process). The molding method of the substrate is not particularly limited, and various molding methods such as compression molding, extrusion molding, blow molding, and injection molding can be employed. When an ABS resin is used for the resin base material, as shown in FIG. 2A, the resin base material 11 includes butadiene particles 11b and an AS resin 11a that is a matrix resin of the butadiene particles 11b. It becomes a structure.

  In step S2, the base material surface of the resin base material having an unsaturated bond is oxidized. Specifically, ozone water is brought into contact with at least the substrate surface (treated surface) that covers the metal coating (oxidation treatment step). In this ozone water treatment, the butadiene particles present on the surface layer of the base material are eluted and escape to form the oxidized layer 12 in which the AS resin as the matrix resin is oxidized. The surface layer of the oxide layer 12 includes a fragile layer.

  In step S3, the surface of the resin substrate 11 is smoothed by a strong alkali treatment in which a sodium hydroxide aqueous solution having a hydroxide ion concentration of 5 mol / L or more is brought into contact with the substrate surface after the oxidation treatment ( Smoothing process).

  At this time, in FIG. 2 (c), the AS resin of the oxide layer on the surface of the base material swells and elutes by coming into contact with the strong alkaline solution. Can be processed. That is, as will be described later, not only the convex portion of the resin base material but also the fragile layer (fragile layer) of the surface layer of the oxide layer 12 of the resin base material can be removed. In this smoothing treatment step, the surface roughness of the resin substrate is, as a guide, in the range of the center line average roughness Ra 0.05 to 0.2 μm or the ten-point average roughness Rz 0.5 to 2 μm. It is preferable.

  Thereafter, as shown in step S4, a metal film is coated on the surface of the base material by electroless plating (electroless plating process). Specifically, first, alkali treatment is performed. In this alkali treatment, an alkali solution containing at least a surfactant is brought into contact with the surface after the smoothing treatment step.

  Surfactant is for improving the adsorption property of the palladium catalyst mentioned later, and can mention anionic surfactants, such as sodium lauryl sulfate. Examples of the alkaline component of the alkaline solution include sodium hydroxide, potassium hydroxide, lithium hydroxide and the like, and an alkali metal such as sodium can be imparted to the treated surface. Furthermore, it is desirable to use a polar solvent as the solvent of the solution containing the surfactant and the alkali component, and water can be used as a representative. May be.

  Alkali treatment can increase the adsorptivity of the palladium catalyst to the treatment surface in the catalyst adsorption treatment step described later, but if the desired amount of palladium catalyst can be adsorbed, this alkali treatment step is omitted. May be.

  Next, in the catalyst adsorption treatment, the treated surface subjected to alkali treatment is immersed in a catalyst solution (catalyzer) in which palladium chloride and tin chloride are dissolved in an aqueous hydrochloric acid solution. Thereby, a palladium catalyst is made to adsorb | suck to the process surface of a base material. Then, the treatment surface is brought into contact with an acidic solution to activate the palladium catalyst.

  Thereafter, in the electroless plating treatment, a nickel plating solution was immersed in the treated surface after the catalyst adsorption treatment to deposit nickel on the surface, and the catalyst adsorption treatment was performed as shown in FIG. An electroless nickel metal film 13 is formed on the treated surface.

  Below, when a convex part or a weak layer is formed in the base-material surface of the resin base material after shaping | molding, it explains in full detail about a plating processing method. FIG. 3A is a view showing a resin base material in which convex portions or fragile layers are formed on the surface of the base material after molding, and FIG. 3B shows the resin base material after ozone water treatment. FIG. 3C is a diagram showing a resin base material that has been subjected to electroless plating treatment without performing alkali treatment on the treated surface after the ozone water treatment. FIG. 3D is a view showing a resin base material that has been subjected to a smoothing treatment with strong alkali on the surface of the base material after the ozone water treatment, and FIG. It is the figure which showed the resin base material which performed the electroplating process.

  Specifically, as shown in FIG. 3A, a convex portion P1 or a fragile layer 11d is formed on the surface of the resin base material 11 after molding. Next, as shown in FIG. 3B, even when ozone water treatment is performed, the butadiene particles 11b contained in the resin base material 11 are eluted, and the surface layer of the resin base material 11 is oxidized. However, although the oxide layer 12 is formed, the convex portion P1 and the fragile layer 11d remain.

  And as shown in FIG.3 (c), even if it is a case where the base material surface of the resin base material 11 of this state is covered with a metal film through an alkali treatment and a catalyst adsorption treatment, the convex portion P1 and the brittleness The convex part P3 is formed in the metal film 13 by the layer 11d.

  However, as shown in FIG. 3D, as in this embodiment, the substrate surface after the ozone water treatment swells and elutes by contacting with the strong alkaline solution. As a result, not only the convex portion P1 and the fragile layer 11d of the resin substrate, but also the fragile layer of the surface layer in the oxidized layer 12 of the resin substrate can be removed, so that the substrate surface of the resin substrate 11 is suitable. Can be smoothed. As shown in FIG. 3E, the surface of the resin base material 11 thus obtained can be smoothed by performing an electroless plating process.

The present invention will be described below based on examples.
Example 1
First, as a resin base material, a resin base material of ABS resin (UMGABS, plating clade) was prepared. Next, as an oxidation treatment, an ozone water treatment was performed on the surface of the molded resin base material under the conditions of an ozone concentration of 40 ppm, a treatment temperature of 20 ° C., and an immersion time of 8 minutes (oxidation treatment step).

  Next, under the condition of ● shown in FIG. 4 as the sodium hydroxide concentration condition, the resin base material was immersed in a 5 mol / L or higher sodium hydroxide aqueous solution at 50 ° C. for 10 minutes (strong alkali treatment), and the base material surface The smoothing process was performed (smoothing process step). That is, since sodium hydroxide has an ionization degree of 1.0, the hydroxide ion concentration contained in this aqueous solution is 5 mol / L or more.

  Next, as an alkali treatment, a mixed aqueous solution in which 50 g / L of NaOH is dissolved and 1 g / L of sodium lauryl sulfate is dissolved is heated to 60 ° C., and the resin substrate after the smoothing treatment step is immersed therein for 2 minutes. Then, an anionic surfactant (sodium lauryl sulfate) was adsorbed.

  The metal catalyst which pulled up the resin base material which adsorbed the anionic surfactant, washed with water and dried, dissolved 0.1% by mass of palladium chloride in 3N hydrochloric acid aqueous solution and dissolved 5% by mass of tin chloride and heated to 50 ° C. It was immersed in the solution for 3 minutes and then immersed in a 1N aqueous hydrochloric acid solution for 3 minutes in order to activate palladium. Thereby, the metal catalyst was made to adsorb | suck to the base-material surface.

  Then, the resin base material was immersed in the Ni-P chemical plating bath kept at 40 degreeC, and the Ni-P plating film (metal film) was deposited for 10 minutes. The thickness of the deposited Ni—P plating film is 0.5 μm. Furthermore, 5 μm of copper plating was deposited on the surface of the Ni—P plating film in a copper sulfate-based Cu electroplating bath.

(Example 2)
In the same manner as in Example 1, the resin substrate was plated. The difference from Example 1 is that ozone gas treatment was performed instead of ozone water treatment in the oxidation treatment step. Specifically, the ozone gas treatment was performed on the base material surface of the molded resin base material under the conditions of ozone gas 200 g / m ³ and contact time 8 minutes.

(Comparative Example 1)
In the same manner as in Example 1, the resin substrate was plated. The difference from Example 1 is that, in the smoothing treatment step, the resin base material was placed in a sodium hydroxide aqueous solution of less than 5 mol / L at 50 ° C. for 10 minutes under the condition of ◯ shown in FIG. This is the point of immersion.

(Comparative Example 2)
In the same manner as in Example 1, the resin substrate was plated. The difference from Example 1 is that the resin base material was immersed in a 3 mol / L sodium hydroxide aqueous solution at 50 ° C. for 5 minutes as a treatment condition for the ozone water treatment in the smoothing treatment step.

(Comparative Example 3)
In the same manner as in Example 1, the resin substrate was plated. The difference from Example 1 is that the alkali treatment shown below was performed on the surface of the base material after the oxidation treatment without performing the strong alkali treatment. Specifically, a mixed aqueous solution in which 1 g / L of sodium lauryl sulfate is dissolved in 1 mol / L NaOH aqueous solution is heated to 60 ° C., and the resin base material after the smoothing treatment step is immersed therein for 2 minutes. An ionic surfactant (sodium lauryl sulfate) was adsorbed.

(Comparative Example 4)
In the same manner as in Example 1, the resin substrate was plated. The difference from Example 1 is that the surface of the resin substrate is etched by chromic acid by immersing the resin substrate in a solution of chromic acid 400 g / L and sulfuric acid 200 g / L instead of performing a strong alkali treatment. The copper plating is performed until the surface is smoothed (up to a film thickness of 50 μm).

(Comparative Example 5)
In the same manner as in Example 1, a resin base material was prepared. Next, after applying an undercoat on the substrate surface of the resin substrate, copper sputtering was performed. In the undercoat treatment, the first agent and the second agent of a two-component urethane coating agent were mixed, and this mixture agent (undercoat agent) was applied to the substrate surface. Thereafter, the applied undercoat agent was cured at 70 ° C. for 60 minutes. Here, a polyol manufactured by Nippon Urethane Co., Ltd. was used as the first agent of the urethane coating agent, and a polyisocyanate manufactured by Takeda Pharmaceutical Co., Ltd. was used as the second agent.

As dry plating, the ultimate vacuum is 0.02 to 0.04 Pa, the sputtering gas pressure (Ar + nitrogen) is 0.1 to 0.5 MPa, and the sputtering power is 1.3 to ³ W / cm ^3. A copper film was coated on the material surface (undercoat surface) by copper sputtering.
[Evaluation methods]
The film thicknesses of the coatings shown in Examples 1 and 2 and Comparative Examples 1 to 5 and the density of the projections on the coating surface (convex density) were measured. The results are shown in Table 1.

[result]
As shown in Examples 1 and 2, when the aqueous sodium solution of 5 mol / L or more, that is, when the hydroxide ion is 5 mol / L or more, the surface of the resin base material after the ozone water treatment is smoothed, Thereby, it is thought that the convex part was not formed in the surface of a metal film. However, when chromic acid etching is performed as in Comparative Example 4, since the surface is roughened during etching, the surface of the coating cannot be smoothed unless the thickness of the coating is increased.

(Confirmation test 1)
In the same manner as in Example 1, the resin base material was plated. The difference from Example 1 is that the concentration of the sodium hydroxide aqueous solution in the smoothing treatment is 5 mol / L, the temperature of the solution shown in FIG. 5 is constant, and the resin base material is immersed for 10 minutes. It is. And the density of the convex part of the metal film coat | covered on the surface of these resin base materials was measured. The result is shown in FIG.

(Result 2)
As shown in FIG. 5, if the temperature of the sodium hydroxide aqueous solution is 30 ° C. or higher, the occurrence of convex portions of the coating can be reliably suppressed.

(Confirmation test 2)
In the same manner as in Example 1, the resin base material was plated. The difference from Example 1 is that the concentration of the sodium hydroxide aqueous solution in the smoothing treatment is 5 mol / L, the liquid temperature is constant at 50 ° C., and the resin base material is immersed for the immersion time shown in FIG. And the density of the convex part of the metal film coat | covered on the surface of these resin base materials was measured. The result is shown in FIG.

(Result 3)
From this result, if the immersion time in the sodium hydroxide aqueous solution is 10 minutes or more, the occurrence of the convex portions of the coating can be reliably suppressed.

  As mentioned above, although embodiment of this invention has been explained in full detail using drawing, a concrete structure is not limited to this embodiment, Even if there is a design change in the range which does not deviate from the gist of the present invention. These are included in the present invention.

  11: resin base material, 12: oxide layer, 13: metal coating

Claims (3)

A step of oxidizing the base material surface of the resin base material having an unsaturated bond;
A step of bringing the base material surface after the oxidation treatment into contact with an alkali solution having a hydroxide ion concentration of 5 mol / L or more to smooth the base material surface;
And a step of performing an electroless plating process on the surface of the substrate after the smoothing process.   The plating treatment according to claim 1, wherein the oxidation treatment is an ozone treatment, and the alkaline solution is a solution containing an alkali metal hydroxide or a solution containing an alkaline earth metal hydroxide. Method.   The plating method according to claim 1, wherein the resin base material is made of an ABS resin.

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