JPH03271375A - Electroless plating method and pretreating agent for electroless plating - Google Patents

Abstract

PURPOSE:To efficiently form a highly adhesive plating layer by applying a chitosan processing soln. on a non-conductive material, drying the soln., imparting a catalyst and then electroless-plating the material. CONSTITUTION:A processing soln. contg. chitosan or a chitosan derivative is applied on a non-conductive material (e.g. synthetic resin and glass) and then dried to form a hydrophilic coating film. The processing soln. consists of a hydrophilic solvent contg. about 0.01-1% chitosan, about 1% dil. acetic acid, etc., and the balance ethanol, and the surface to be plated is preferably coated with an undercoat (lacquer, etc.) before chitosan is applied. A catalyst is then imparted to sensitize and activate the material, and a plating layer is formed by electroless plating. Consequently, even the desired part of the surface of a non-conductive material is plated with good adhesion.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for electroless plating on a non-conductive material and a pretreatment agent for electroless plating, and more particularly, to The present invention relates to an electroless plating method and a pretreatment agent for electroless plating that can be formed well and can also be applied to partial plating. The present invention is applicable to the treatment of non-conductive materials to make them conductive, the inner coating of various members, the provision of electromagnetic shielding functions, the plating of printed circuits, CO alloy a! It can be used for membrane production, etc.

[Conventional technology]

In contrast to electroplating, which uses electric current to deposit metal through an electrochemical reaction, electroless plating uses the action of a reducing agent to reduce ions in the plating solution and deposit them on the object to be plated, without using electric current. It is widely used as a method for plating the surfaces of non-conductive materials such as plastics, ceramics, paper, and fibers.

The general steps of electroless plating are as shown in Figure 1. Among these steps, the etching step makes the surface of the material hydrophilic and improves the adhesion between the material surface and the plating layer. This is promoted by the anchoring effect, and is mainly carried out by mechanical means such as blasting and tampling, or chemically by corrosive liquids such as acids (chromic acid with sulfuric acid or phosphoric acid added as necessary) or alkali. It is done by means.

Then, on the surface of the non-conductive material to which electroless plating is applied,
Normally, a step of catalyst provision or activation is required to generate a metal salt that serves as a reduction catalyst, and Pd is an example of a substance that acts as such a reduction catalyst.

pt, Au, Ag, Ir, Os, Ru+ and l? h metal salts are used. The sensitizing step and the activating step are provided to supply active sites of the catalyst metal to the etched surface of the material to be plated. The activating step is carried out by applying a solution, for example a Pd salt.

This is carried out by applying a solution of Au salt, Ag salt, etc.

[Problem to be solved by the invention]

In such electroless plating methods, one of the main problems is the adhesion between the material to be plated and the plating layer. may not adhere sufficiently, resulting in poor plating. Therefore, measures have been taken to suppress the occurrence of plating defects by increasing the temperature of the plating bath, but the effect is insufficient and, in addition, when the material to be plated is plastic, there is a problem that the material to be plated melts. occurs.

Various proposals have been made for improving the adhesion between the plating material and the plating layer, such as U, S, and P.
, 4670306.

This publication presents various known publications related to adhesion, and is useful for understanding the technical background of the present invention. A method in which electroless plating is applied after coating a plating catalyst with a substance that has an appropriate absorbency and then contacting the surface of the coated non-conductive material with a catalyst and catalyst promoter to sufficiently apply the catalyst. This is said to improve the adhesion between the underlying plating material and the plating layer. Preferable examples of the coating material include acrylic latex paint and N-methyl-2-
It cites acrylic latex paints with added pyrrolidone.

However, the electroless plating method using the above-mentioned coating material is not only applicable to a limited range of materials to be plated, but also has an insufficient effect of improving adhesion.

Furthermore, Japanese Patent Application Publication No. 62-500344 discloses a method of applying electromagnetic radiation shielding or RFI shielding to a non-conductive enclosure, and in this method, Nt+Cu, PE is added to acrylic paint as the first layer of the shielding layer. , Co+Au
+Ag+A liquid organic binder in which active metal particles selected from pt and Pd are dispersed is used, and an electroless plating layer of Ni, Cu, or an alloy thereof is further laminated as a second layer on the first layer. are doing.

However, this method only uses acrylic paint as a binder for active metal particles, and the affinity and adhesion with the underlying material to be plated and the plating layer are not sufficient, and there is still room for improvement. ing.

The present invention has been made in view of these circumstances, and provides an electroless plating method that efficiently provides a plating layer with high adhesion to the base, and is particularly applicable to partial plating, and an electroless plating method that can be applied particularly to partial plating. The purpose is to provide a pretreatment agent.

[Means to solve the problem]

The electroless plating method of the present invention, which achieves the above object, involves applying a treatment solution containing chitosan or a chitosan derivative onto the non-conductive material when forming an electroless plating layer on the surface of the non-conductive material. The main point is that after drying, a catalyst is applied and electroless plating is carried out, and the pretreatment agent for electroless plating of the present invention is a treatment agent used in electroless plating of non-conductive materials. The gist is that it consists of a treatment liquid containing chitosan or a chitosan derivative, and is used in a pretreatment step that is performed prior to the application of a catalyst.

[Effect]

Chitosan (β-1,4゛-poly〇glucosamine) used in the present invention is a natural polymeric substance, and chitin (β1.4゛-poly-N) is extracted from crustaceans such as crabs. -acetyl-D-glucosamine) can be obtained by tax acetylation. This chitosan is a cationic electrolyte polymer having amino groups and has excellent water retention. In the present invention, chitosan derivatives such as carboxymethyl chitosan and glycol chitosan can be used in the same manner as chitosan, and these chitosan or chitosan derivatives can be used in powder or liquid form.

In addition, as the non-conductive substance in the present invention, synthetic resin 1
Examples include paper, glass, ceramics, etc. that cannot be directly plated by electroplating.

In the method of the present invention, when forming an electroless plating layer on the surface of a non-conductive substance as described above, the above-mentioned chitosan or chitosan is applied to the surface of the non-conductive substance prior to the application of a catalyst and each step of electroless plating. A treatment liquid containing a derivative (hereinafter simply referred to as chitosan) is applied to form a hydrophilic film on the surface.

The hydrophilic film obtained in this way adheres well to the underlying non-conductive material due to the good wettability of chitosan, and since chitosan exhibits a strong adsorption effect on heavy metals, it The catalyst layer formed by the heavy metal catalyst etc. is sufficiently captured. As a result, in the electroless plating process, a sufficient amount of active catalyst can be supported on the surface to be plated, and an electroless plating layer with good adhesion can be efficiently formed in a uniform state on top of the active catalyst. can do.

The treatment liquid containing chitosan contains 0.01 to 1% chitosan.
It is desirable to contain a range of 0.1%, preferably around 0.1%.
As the amount decreases below 0.01%, the effect of addition becomes smaller, and sufficient effects on adhesion to the substrate and catalyst trapping ability cannot be obtained. On the other hand, even if it is added in an amount exceeding 1%, the effect of addition becomes saturated and becomes uneconomical.

Components other than chitosan in the treatment liquid containing chitosan may include dilute acids such as acetic acid, formic acid, and hydrochloric acid, and these dilute acids are used to dissolve chitosan in the treatment liquid. Its concentration is around 1%, especially 0.2 to 1.
5% is appropriate. Most of the remainder is water and a hydrophilic solvent such as ethanol or methanol, and the hydrophilic solvent exhibits the effect of accelerating drying after application of the treatment liquid containing chitosan. Furthermore, if necessary, a leveling agent consisting of a surfactant can be added to the processing solution in a proportion of several percent.
This allows the treatment agent to be applied thinly and widely to the underlying surface.

The treatment solution containing chitosan is applied with a brush or roller to the surface of the non-conductive substrate.

It can be applied by spraying, dipping, or other methods, and can form a hydrophilic film that exhibits excellent adhesion to the base.

After applying a treatment solution containing chitosan to the surface of the base, the steps of catalyst application and electroless plating are sequentially performed to form an electroless plating layer with good adhesion to the surface of the non-conductive material serving as the base. It can be formed efficiently. Furthermore, in the present invention, by pre-treating a part of the surface of the non-conductive material with a treatment solution containing chitosan, it is possible to selectively support the catalyst only on the pre-treated part, and as a result, partial electroless plating can be achieved. can be implemented effectively. Furthermore, in the present invention, electroless plating can be successfully applied to styrene resins and acrylic resins, which have conventionally been difficult to electroless plate.

In addition, in the above, the treatment liquid containing chitosan was applied directly to the surface of the non-conductive material serving as the base, but it is desirable to apply an undercoat before applying the treatment liquid containing chitosan, and the undercoat paint layer By forming microscopic irregularities on the surface to be plated, the anchoring effect can improve the adhesion of the electroless plating layer. In other words, the application of a primer paint is an alternative treatment to etching, and is a milder treatment than physical or chemical etching, and can provide a finely uneven surface, as well as being a low-cost base treatment in terms of equipment. can be carried out. Various types of paints such as oil-based paints, lacquer types, 9 synthetic resin-based paints, etc. can be used as the undercoat paint, and there are no particular restrictions on the type, but it is recommended to use a paint that has excellent adhesion to the base. desired.

As for the catalyst application step, a method conventionally employed in electroless plating can be adopted, and as described above, after performing the pretreatment, sensitizing is performed with an aqueous solution of stannous chloride, for example, Next, Pd, Ni,
The catalyst application step can be completed by activating with a catalytic metal such as Cu, Fe, Co, Au, Ag, or Pt or a compound thereof. Then, the surface to be plated with the catalyst is coated with Cu, Ni,
When immersed in a plating bath of Co, Pd, Au or their alloys, an electroless plating layer can be efficiently formed due to the reduction action of the active catalyst, and the desired electroless plating material of non-conductive material can be obtained. can.

〔Example〕

After applying an acrylic undercoat to the surface of the styrene resin material using a spray or brush, apply a treatment solution containing chitosan (chitosan 0.5%, acetic acid 0.5%, balance: methanol and water) as an undercoat. Apply it on the surface and let it dry thoroughly.

Next, the sensitizers and activators shown in Table 1 were used in the following combinations to apply a catalyst to the surface coated with the treatment solution (sensitization treatment and activation treatment were each carried out for 10 seconds), Electroless plating was performed by placing the sample in a plating bath having the composition shown in Table 2 for 30 minutes.

(Experimental conditions) Experiment 1: Sensitizer A - Activator C Experiment 2: Sensitizer B - Activator C Experiment 3: Sensitizer A - Activator Table 1 Table 2 Treatments containing chitosan After applying the liquid and drying it thoroughly,
In Experiment 1 using sensitizer A and activator C, the catalyst could be sufficiently applied to the surface coated with the treatment solution containing chitosan, and an electroless plating layer (1 to 2 μm thick) with good adhesion was formed. ) could be selectively formed.

Incidentally, the various test results regarding the appearance and adhesion of the Ni plating layer obtained in Experiment 1 are as shown in Table 3. The adhesion was determined by dividing a 110 m x 10 plating surface into 100 micro areas every 1 fi vertically and horizontally, pasting Sellotape on the plating layer forming surface, and then peeling it off [number of remaining plating areas/total number of areas]. As shown in Table 3, the Ni plating layer obtained in Experiment 1 was
It was confirmed in various tests that it exhibited good appearance and excellent adhesion.

On the other hand, in Experiment 2, sensitizing agent B adhered to the entire surface, that is, to some extent to the surface other than the surface coated with the treatment solution containing chitosan, and along with this, the activation progressed across the entire surface and selectively. Plating could not be performed, and poor adhesion of the plating layer occurred on the back side, which was not coated with the treatment liquid. Further, in Experiment 3, since it was difficult for Pd as an activator to replace Sn as a sensitizing agent, sufficient catalyst could not be applied, resulting in non-plated areas.

On the other hand, under the same conditions as in Experiment 1 above, but when the treatment solution containing chitosan was not sufficiently dried after coating, color unevenness and blistering occurred on the plated surface.

Margins belowFurthermore, in Experiment 1 above, electroless plating was performed under the same conditions except that the plating bath was the copper plating bath shown in Table 4. As a result, a good Cu plating layer was selectively formed on the styrene resin surface. We were able to.

As shown in Table 4, plating layers can be selectively formed, and partial plating can be freely performed in which only necessary parts are plated. Furthermore, by applying a treatment solution containing chitosan, the etching process can be omitted, the plating process can be simplified, and productivity can be increased. Moreover, a high-quality plated product with excellent adhesion can be obtained.

In this way, it has been possible to bring great benefits to fields such as electromagnetic shielding and internal metal coating.

[Brief explanation of drawings]

FIG. 1 is a flow explanatory diagram showing an electroless plating process carried out by boat. 〔Effect of the invention〕

Claims (3)

[Claims] (1) To form an electroless plating layer on the surface of a non-conductive material, apply a treatment solution containing chitosan or a chitosan derivative onto the non-conductive material and dry it, then apply a catalyst and electroless plating. An electroless plating method characterized by: (2) The electroless plating method according to claim 1, wherein an undercoat is applied on the non-conductive substance prior to applying the treatment liquid containing chitosan or a chitosan derivative. (3) A treatment agent used for electroless plating of non-conductive materials, consisting of a treatment liquid containing chitosan or a chitosan derivative, characterized by being used in a pretreatment step that is performed prior to applying a catalyst. A pretreatment agent for electroless plating.