JPH02175895A - Method for plating nonconductor - Google Patents

Abstract

PURPOSE:To easily form a high-conductivity plating layer consisting essentially of Cu and a corrosion-resistant plating layer contg. Ni on a nonconductor in the same plating bath by activating the surface of the nonconductor, and then electroplating the nonconductor in a plating soln. contg. Cu ion, Ni ion, and a reducing agent while changing the current density. CONSTITUTION:When a conductive electromagnetic wave shielding layer is formed on a nonconductor of plastics, etc., by electroplating, the nonconductor is pretreated to clean the surface, and then a metallic Pd nucleus or a metallic Ag nucleus is deposited by the conventional method to activate the surface. The nonconductor is then dipped in the plating soln. contg. Cu ion, Ni ion, and the reducing agent for the ions, and firstly electroplated at the low current density of eta0.5A/dm<2> with a highly conductive Cu-Ni alloy contg. >80% Cu. The nonconductor is then plated in the same bath with a Cu-Ni alloy contg. >30% Ni and excellent in corrosion resistance at the current density of >=1A/dm<2>. An electromagnetic wave shielding layer is formed in a short time with such simple device and process.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of plating a non-conductive material, which is suitably employed when forming an electromagnetic shielding layer on a non-conductive material such as plastic.

[Conventional technology]

Conventionally, it has been known to form a copper plating layer or a nickel plating layer on a non-conductive material such as plastic as an electromagnetic shielding layer. In this case, the formation of the copper plating layer and the nickel plating layer follows the usual method for plating non-conductive materials such as plastics, and after degreasing, etching, etc. as appropriate,
A method has been adopted in which activation treatment is performed to form metal palladium nuclei or metal silver nuclei on the surface of a nonconductor, and then electroless copper plating or electroless nickel plating is applied.

It is also known to further form a nickel plating layer on the copper plating layer as an electromagnetic shielding layer (Patent Publication No. 62-500344 or U.S. Pat. No. 4,663).
, No. 240). This is because the nickel plating layer prevents the copper plating layer from being oxidized in the usage atmosphere and deteriorating the shielding effect.
The method for forming a nickel plating layer is to form an organic binder layer with metal particles dispersed on a non-conductor, form an electroless copper plating layer on top of that, and then form an electroless nickel plating layer on top of that. The method is adopted.

[Problem to be solved by the invention]

Conventionally, when forming an electromagnetic shielding layer consisting of two copper-nickel plating layers, electroless copper plating and electroless nickel plating are performed after forming an active metal core. , these steps are naturally carried out in separate tanks, and between each step there is water washing,
Processes such as pickling activation and water washing are required, making the process long. For this reason, especially when the object to be plated is a large plastic, great care is required in transporting the object, and the chance of the object falling increases. Furthermore, when applying electroless nickel plating on a copper plating layer, there is a problem that electroless nickel plating is difficult to deposit because copper is essentially not catalytically active with respect to electroless nickel plating solution. In this case, in order to hasten the start of electroless nickel plating,
If the amount of reducing agent is increased or the amount of complexing agent is decreased, the plating solution becomes unstable.

The present invention was made to improve the above-mentioned situation, and consists of two layers: a highly conductive layer mainly made of copper and a corrosion-resistant layer containing 30% (wt%) or more of nickel (the same applies hereinafter) in one plating bath. To provide a method for plating on a non-conductor, which can simplify the process and shorten the plating time.

[Means and effects for solving the problem] In order to achieve the above object, the present invention attaches metal palladium nuclei or metal silver nuclei to the surface of a non-conductor, and then converts the non-conductor into a copper salt and a nickel salt. Copper-based plating containing at least 80% copper, especially at least 85% copper, by first immersing it in a plating bath containing a reducing agent and electroplating at a low current density of 0.5 A/drrr or less. Form a coating, then LA/d
Electroplating is performed at a high current density of rrr or more to form a plating film containing 30% or more of nickel.

That is, in the present invention, after a metal palladium nucleus or a metal silver nucleus is deposited on a non-conductor according to a conventional method, a plating bath containing a copper salt, a nickel salt, and a reducing agent is used to deposit a metal palladium nucleus or a metal silver nucleus on a non-conductor. Electroplating is performed at a current density to form a plating film mainly composed of copper. In this case, the metal palladium core or the metal silver core is formed extremely thinly on the non-conductor, and conventionally, for this reason, electroless plating is first performed,
When electroplating was performed, it was performed after electroless plating, but according to the present invention, the first electroplating is performed at a low current density, and furthermore, reducing agents such as hypophosphite are used in the plating bath. is added, electroless plating is performed at the same time as electroplating, and the metal palladium cores and metal silver cores are reinforced. Therefore, there is no problem when directly electroplating a thin layer of metal palladium cores or metal silver cores. There is no, and moreover,
Because electroplating is performed at such a low current density, even if copper salt and nickel salt coexist in the plating bath, copper will precipitate preferentially, and the ratio of copper as the main component, for example, 80%.
% or more of the plating layer is formed.

Next, in the present invention, after forming a plating layer mainly composed of copper to a predetermined thickness, the object to be plated is directly placed in the same plating bath without being lifted from the plating bath and transferred to another plating bath. Electroplating is performed by increasing the current density to IA/d+rr or higher. In this case, even if plating is performed at such a high current density, there will be no problem since a copper plating film has already been formed as the base film, and furthermore, by plating at such a high current density, the nickel will be removed. A plating layer containing 30% or more of the metal and having good corrosion resistance is formed.

Therefore, according to the present invention, a highly conductive plating layer mainly composed of copper and a highly corrosion-resistant plating layer containing 30% or more of nickel are successively formed in the same plating bath by simply changing the current density, and the process Since both layers are formed by electroplating, the plating time can also be shortened, and both layers can be formed smoothly and reliably.

The present invention will be explained in more detail below.

The non-conductive materials to be plated in the present invention include plastics, ceramics, etc. When plating these according to the present invention, if necessary, after performing pretreatment such as degreasing and etching, the surface is coated with metallic palladium. An activation treatment is performed to form a nucleus or a metallic silver nucleus. This activation treatment can be carried out by a conventional method.For example, when forming palladium nuclei, methods such as sensitizing-activating method and catalystizing-acmorelating method can be adopted, and methods such as forming silver nuclei can be used. In this case, a known method can be used, such as a method using a silver mirror reaction.

Next, in the present invention, the thus activated non-conductor is electroplated in a plating bath containing a copper salt and a nickel salt, and also containing a reducing agent.

Here, as the plating bath, one containing a water-soluble copper salt, a water-soluble salt of nickel, and a complexing agent is preferably used, but as the copper salt, copper sulfate, cupric chloride, etc. are used, As the nickel salt, nickel sulfate, nickel chloride, etc. are used. In this case, the concentration of the copper salt is 0.001-0.2 mol/Q, especially 0.01-0.2 mol/Q, and the concentration of the nickel salt is 0.001-0.2%, 1Lz/fl, especially 0.
01 to 0.2 mol/Q. Further, the complexing agent is one with 0-coordination (for example, various organic acids such as acetic acid, lactic acid, citric acid, tartaric acid, etc., and their salts).

S-coordination agents (e.g., thioglycolic acid, cysteine) and N-coordination agents (e.g., ammonia, glycine, ethylenediamine) are used as appropriate; particularly preferred complexing agents include citric acid, Examples include tartaric acid, thioglycolic acid, glycine, and salts thereof.

These complexing agents can be used alone or in combination of two or more, but the concentration is preferably at least equimolar to the total metal salt concentration, more preferably about twice the molar concentration. It is.

In addition, a reducing agent is further added to the above plating bath, and hypophosphites such as NaHP O, .H2O, boron-based reducing agents such as dimethylamine borane, etc. are used as reducing agents. The concentration is 1 mol/Q or less, especially 0.1~
It is preferable to set the amount to 0.5 mol/Q.Furthermore, a pH adjuster, a buffer, a stabilizer, and other additives may be added to the plating bath as necessary.

Note that the pH of the plating bath is preferably 5 to 13, particularly 8 to 12.

In the present invention, as described above, a non-conductor to which metal palladium nuclei or metal silver nuclei are attached is immersed in the above plating bath, and first electroplated at a low current density of Dko, 5 A/d- or less. As a result, electroplating is performed directly on the non-conductive material on which a thin layer (usually 0.IIAn or less) of metallic palladium nuclei or metallic silver nuclei has been formed, and moreover, copper is deposited by 80% or more.
In particular, a plating film containing 85% or more of copper as a main component is formed. In this case, a more suitable range of current density is 0.01 to 0.5 A/dr& from the viewpoint of obtaining a plating film with a high copper content, but the current density at the initial stage of plating should be set to 0, LA/drrr or less, and then the current density should be 0.1-0.5A/dr with voltage control etc.
It is preferable to raise the value to f.

The thickness of the plating film mainly made of copper by electroplating at Dko, 5A/d- or less is appropriately selected and is not particularly limited, but if an electromagnetic shielding layer is to be formed, it is usually 1. ~lopm.

Next, in the present invention, after electroplating at 0.5 A/drrr or less, electroplating is performed in the same plating bath by increasing the current density to LA/drrr or more, preferably from 1 to 5 A/dnr. As a result, a highly corrosion-resistant plating film containing 30% or more of nickel is formed on the copper-based plating film. This nickel is 30
The thickness of the plating film containing % or more is also selected appropriately, but when forming an electromagnetic shield layer, it is usually 0.2 to 5%.
− is.

In addition, in the electroplating mentioned above, the plating temperature is 15
The temperature can be set at ~90°C, and stirring can be performed if necessary. In this case, the copper content in the plating film can be increased by stirring, and the nickel content can be increased by stopping stirring.

Further, as the anode, copper, nickel, or a copper-nickel alloy can be used, and in some cases, an insoluble anode can also be used.

Next, the present invention will be explained in more detail with reference to Examples.
The invention is not limited to the following examples.

〔Example〕

After degreasing and etching an ABS resin plate (50 nyn x 15 mm x 3 uw) by a conventional method, metal palladium nuclei were formed on the surface using the following activation solution.

Process and conditions 2, warm water washing at 50°C, 2 minutes 4, pickling 10vo1% H, S 0425°C,
2 minutes 7: Accelerator AT-10610vo1% 25
℃, 5 minutes Using a commercially available chemical (Kamiso Kogyo Plastic Pretreatment Process) Next, after washing with water, plating was performed using the following plating bath under the following conditions.

Liyuo Silkworm Copper Sulfate 0.05 mol/Q Nickel Sulfate 0.05 II Sodium Hypophosphite Q, 3N Sodium Citrate 0, 2N Burial Sand 0
．． 05 〃Stabilizer 5 ρp
mp) l 8, 3 standing Tojo stop plating temperature 80℃ Stirring No anode Platinum plated titanium cathode current density (Dk) 0 minutes 6 minutes 0.05 → 0.5 A/d polo → 7 minutes
5 A/d plated film thickness (total)
3.7 As a result of 4, when electroplating is performed at 0.05 to 0.5 A/drd' for the first 0 to 6 minutes, the copper content in the plating film is approximately 85%, which is the primary 6 When plating was performed at 5 A/drrr for a period of 7 minutes, the nickel content in the plating film was about 35%.

Moreover, the appearance of the obtained plating film was good.

The drawings show the relationship between the nickel content in the plating film and the current density when plating was performed at various current densities using the above plating bath.

〔Effect of the invention〕

According to the present invention, a highly conductive plating film mainly composed of copper,
Two layers of a highly corrosion-resistant plating film containing 30% or more of nickel can be formed continuously without removing the object to be plated from a single plating bath, which simplifies the process and shortens the plating time. An electroplated film can be formed directly on a thin metal palladium core or metal silver core without electroless plating in advance, and therefore the process can be simplified in this respect as well. For this reason, the present invention is suitably employed when forming an electromagnetic shielding layer on plastic or the like.

[Brief explanation of the drawing]

The drawing is a graph showing the relationship between various current densities and the amount of nickel in the plating film when using the plating bath of the example. Applicant Uemura Kogyo Co., Ltd. Agent Patent Attorney Takashi Kojima

Claims (1)

[Claims] 1. After attaching a metal palladium nucleus or a metal silver nucleus to the surface of a non-conductor, the non-conductor is immersed in a plating bath containing a copper salt and a nickel salt and a reducing agent.
Electroplating is performed at a low current density of /dm^2 or less to form a copper-based plating film containing 80% by weight or more of copper, and then electroplating is performed at a high current density of 1A/dm^2 or more. A method for plating a non-conductor, the method comprising: forming a plating film containing 30% by weight or more of nickel.