KR0176299B1 - Electroless plating for shielding electromagnetic wave - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a one-sided electroless plating method for shielding harmful electromagnetic waves from plastic housings of electrical and electronic devices. It is left to paint for 35 to 40 minutes, dried at 60 to 65 ° C. for 1 hour, and then left to stand at room temperature for 3 hours or more to form a conductive coating on a portion to be electroless plated. When an electrically conductive layer is formed on the surface of the workpiece, alkali degreasing is performed on the surface for 5 to 7 minutes and activated for 3 to 5 minutes in a mixed aqueous solution of 0.2 to 0.3 g / l of palladium chloride (PdCl ₂ ) and 3% of hydrochloric acid (Hcℓ). After treatment and washing, radioactive (PuCl ₂ ) 5-6 g / l, formalin (HCHO) 2-3 g / l, EDTA-4 sodium 45-56 g / l, sodium hydroxide 6-7 g / l, PH 12-13 Electrolytic plating for 1 hour 20 minutes at 45 ~ 50 ℃ in the copper plating solution to form a uniform and dense electroconductive copper film. After washing with water three times again, Palladium chloride (PdCl ₂ ) 0.2 ~ 0.3g / ℓ, hydrochloric acid 3% active treatment in 30 ℃ mixed aqueous solution for 1 to 2 minutes and washed twice and nickel sulfate (NiSO ₄ ) 5-7g / l, sodium hypophosphite (NaH ₂ PO ₂ ) 30 to 50 g / l, sodium citrate 30 to 50 g / l, and then adjusted to pH 8.5 to 9.0 with aqueous ammonia (NH ₄ OH), 35 to 40 ℃ Single sided electroless plating method with uniform, durable and excellent electromagnetic shielding ability, which is electroless nickel plated and washed with water for 20 minutes at.

Description

Single sided electroless plating method to shield electromagnetic waves

1 is the change in resistance of a product over time in a SO ₂ environment.

2 shows the change in resistance of a product over time in an H ₂ O environment.

3 is a change in resistance caused by salt deposition of the one-side plating method and the conductive coating method.

The present invention relates to a single-sided electroless plating method for forming an electromagnetic wave shielding film on a plastic part.

The modern industrial society is an information society that needs to exchange and share a large amount of multi-national information in a short time. As a result, almost all devices are equipped with electric and electronic equipment for information processing, generation, management, etc. and improve the efficiency as a modern device.

However, as the use of such electric and electronic equipment increases, electromagnetic interference between devices and devices increases, causing a large social problem such as electromagnetic disturbances, and even harmfulness to the human body.

As a result, European and Western countries are increasingly tightening the regulation of electromagnetic waves, expanding the laws and regulations on the use and manufacturing of devices that do not have adequate countermeasures against electromagnetic interference, even as a means of trade barriers. Until. Because of this, more active countermeasures against electromagnetic interference have been required, and since the present inventors have already developed an electroless plating method for shielding electromagnetic waves on electrical and electronic device housings of plastics such as ABS, they are easily soluble in alkali. Inventions such as electroless plating solutions for materials have been completed, and industrial applications have been made. These inventions are mainly applied to plastic housings of electric and electronic devices. Electroless plating is applied to both inside and outside of the housings to shield electromagnetic waves, and they have the highest electric conductivity, electromagnetic shielding ability, chemical and thermal durability. It is applied to electric and electronic devices with built-in circuits, and the metal plating film is exposed on the outside, which requires additional decorative treatment by painting. It has been.

Conventional electromagnetic shielding plating technology for plastic materials gives electroless plating by adhering fine surface irregularities of several micrometers or less on the surface of plastic materials and adsorbing precious metals such as palladium and platinum with excellent catalytic activity. In addition, copper or nickel, which has good electrical conductivity, forms a metal film to block the passage of electromagnetic energy waves. The adhesion between the coating film and the plastic material is obtained by fine concavity and convexity strongly constraining the metal coating film with mechanical force.

The electroless plating method is characterized in that the plastic coating is completely deposited in all the processing liquids in the process, thereby causing plating problems even where it is not desired. In order to prevent this, it is possible to cut off the contact between the treatment liquid and the measurement surface of the coating during the plating process by painting with a masking paint, etc. I can't. In addition, plastic materials such as ABS, PC / ABS, PC, etc., which are currently used as housing materials for electrical and electronic devices, exhibit such a remarkable feature. The exterior is painted on the side. Due to these problems, the surface characteristics of the plastic material are maintained on the outside of the housing and the conductive paint is applied only on the inside. Electromagnetic shielding characteristics by the conductive paint are determined by the thickness of the coating film formed by the conductive paint, and therefore, a conductive coating film is usually formed with a thickness of about 40 to 60 µm. However, when the conductive coating film is formed by the coating method, it is difficult to obtain a uniform coating film according to the shape of the coating object or the function of the painting worker, the quality of the coating film is not uniform, and it is difficult to form a coating film of an appropriate thickness in the corners of the coating material. Many powders made of conductive materials (metal particles, etc.) are generated, which may cause the failure of precise electric and electronic devices in the future. In addition, there is a problem that the surface conductivity, such as failing to maintain the original coating state while undergoing changes in the thermal, chemical environment, etc., can be applied only limitedly, and the electromagnetic shielding ability is also significantly higher than that of the electroless plating method. low. The current limit of electromagnetic shielding ability of conductive paints on the market is usually 80 dB or less, much lower than about 110 dB of electroless plating.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and an object thereof is to provide a one-side electroless plating method for plating only one side of a plastic housing for shielding electromagnetic waves of plastic parts of electrical and electronic devices.

In order to achieve the above object, the present invention degreasing plastic water as a plastic degreasing agent such as 60 g / l of a degreasing agent (PC-200), washing with water, drying and cooling down to 35-40 ° C., and then as a conductive paint. After application, it is allowed to stand for 35 to 40 minutes, dried at 60 to 65 ° C. for 1 hour, and then left to stand at room temperature for 3 hours or more, and then further degreased for 5 to 7 minutes, and 0.2 to 0.3 g of palladium chloride (PdCl ₂ ). / l, hydrochloric acid (HCI) in a mixed aqueous solution of 3% for 3 to 5 minutes, washed with water, copper chloride (CuCl ₂ ) 5-6 g / l, formalin (HCHO) 2-3 g / l, EDTA 18-22 g / 1 L, sodium hydroxide 6-7 g / L, pH 12-13, electroless plating solution deposited at temperature of 45-50 DEG C for 1 hour 20 minutes, electroless copper plating, washing with water three times, and again palladium chloride (PdCl ₂ ) 0.2 Substituted and plated for 1 to 2 minutes in a mixed solution of 30 ° C. containing 3% of 0.3 g / L hydrochloric acid, followed by washing twice with nickel sulfate (NiSO ₄ ). 5 to 7 g / l, sodium hypophosphite (NaH ₂ PO ₂ ) 30 to 50 g / l, sodium citrate 30 to 50 g / l, mixed with ammonia water (NH ₄ OH) to pH 8.5 to 9.0 It is characterized by washing with electroless nickel plating at 20 ° C. for 20 minutes.

Hereinafter, the manufacturing process of the present invention will be described in detail.

[Step 1]

Plastic degreaser is degreased with a plastic degreasing agent such as 60 g / l of degreasing agent (PC-200) for 3 to 5 minutes to remove oils such as mold release agent and washed twice.

Second Process

The plastic coating material which passed through the 1st process is dried at 60-65 degreeC until moisture dry completely.

[Third process]

After the second process, the plastic coating is cooled down to 35 to 40 ° C. Before the third step, the silver-based or nickel-based or copper-based conductive paint is sufficiently stirred.

[4th process]

After the third process, the conductive paint is sprayed and sprayed at the place where the surface of the workpiece is to be plated.

[5th process]

After the fourth step, it is left for 35 to 40 minutes and dried at 60 to 65 ° C. for 50 minutes for 1 hour.

[Sixth Step]

It is left to stand at room temperature for 3 hours or more after the 5th process.

[7th process]

In order to assist contact between the plating liquid and the coating surface, the coated material subjected to the sixth step is dipped in alkaline degreasing solution for 5 to 7 minutes to improve contact with the plating liquid and wash with water three times.

[Step 8]

After the seventh step, activation treatment is performed for 3 to 5 minutes in a mixed aqueous solution of 0.2 to 0.3 g / l palladium chloride (PdCl ₂ ) and 3% hydrochloric acid for 3 to 5 minutes, followed by washing with water three times.

[Ninth process]

Through the eighth process, a mixed aqueous solution of copper chloride (CuCl ₂ ) 5-6 g / l, formalin (HCHO) 2-3 g / l, EDTA-4 sodium 45-56 g / l, sodium hydroxide 6-7 g / l and pH 12- 13, electroless copper plating for 1 hour and 20 minutes at the temperature of 45-50 degreeC, and it washes three times.

[10th process]

Through the ninth step, the electroless copper-plated workpiece is again activated by substitution plating for 1-2 minutes in a 30 ° C. aqueous solution of 0.2-0.3 g / L hydrochloric acid 3% of palladium chloride (PdCl ₂ ) and washed twice.

[Step 11]

After the tenth step, the mixture was mixed with ₅ to 7 g / l of nickel sulfate (NiSO ₄ ), 30 to 50 g / l of sodium hypophosphite (NaH ₂ PO ₂ ), and 30 to 50 g / l of sodium citrate, followed by aqueous ammonia (NH ₄ OH). The pH is set to 8.5 to 9.0 and the temperature is set to 35 to 40 ° C. Electroless nickel plating is carried out for 20 minutes to form a nickel coating layer that protects the copper conductive film, which is the main electrically conductive layer, and washed with water five times.

[12th process]

After the eleventh step, the plated object is washed in distilled water at 50 to 55 ° C. for 5 to 7 minutes and then dried to complete the one-side plating on the plated object.

The plated material that has undergone the above process has the copper conductivity of about 3㎛ or more and about 0.7㎛ or more of nickel at the specific position of the coated material, and it shows electrical conductivity. Problems such as exterior coating and the problem of lowering the electromagnetic wave shielding ability due to the decrease in electromagnetic wave shielding ability, the non-uniformity of the thickness of the coating film, and the conductivity due to thermal and chemical environmental changes can be solved. Therefore, almost all electromagnetic wave shielding ability is provided in all the parts in which the plating film was formed. Almost all electromagnetic shielding surface treatment methods such as conductive coating method and double-sided electroless plating method increase the shielding ability according to the intrinsic electrical conductivity and thickness of the coating film, so it is very important to control the thickness uniformly in the manufacturing process. In the double-sided electroless plating method, a coating film is prepared by depositing a coating film on an electroless plating solution, so that the coating film is formed at a uniform speed where the plating liquid and the surface of the coating surface can be contacted. Partial uniformity is further improved. However, when the conductive film is manufactured by the conductive coating method, the corners or the covered areas of the coating are not properly coated, and the problem is more severe in the small and complicated shape of the coating. Therefore, there is a remarkable difference in the electrical conductivity for each part, and the electromagnetic shielding ability also has many variations. In the single-sided plating method, of course, like the conductive coating method, the conductive coating should be applied once, but since the electrical conductivity of the coating film is not dependent on the thickness of the coating film, the coating film can form a surface capable of electroless plating. As long as the adhesion between the plated film and the surface of the workpiece can be maintained, the thickness may be thin. In terms of the manufacturing cost of the conductive coating film, in the case of double-sided plating, the coating film manufacturing cost is relatively higher than that of the conductive coating method due to the exterior coating after plating. However, in the one-side plating method, the coating film may be made thinner. Since it can be kept much lower, the overall coating film manufacturing cost may be lower than that of the conductive coating method.

The electrical properties and the electromagnetic shielding ability of the single-side plated film thus prepared are shown in Table 1 and Table 2.

Hereinafter, an embodiment of the present invention will be described in detail.

EXAMPLE

The polycarbonate plate was cut into 10 cm and 10 cm lengths, and then degreased at 50 ° C. for 3 minutes with 60 g / L of degreasing agent (PC200) and 10 g / L of NaOH, washed three times, and dried at 62 ° C. for 1 hour. After cooling the polycarbonate plate which completely evaporated the moisture until it reached 37 degreeC in air | atmosphere, only one side was cross-coated with the nickel-based electroconductive paint purchased commercially, and it raised up to 10 micrometers in thickness. The polycarbonate plate coated with the conductive nickel-based paint was left at 25 ° C. for 40 minutes, dried at 62 ° C. for 1 hour, and left at 25 ° C. for 4 hours. The conductive polycarbonate plate was again immersed in a mixed solution of 60 g / l of degreasing agent (PC200) and 10 g / l of NaOH for 6 minutes to improve contact between the coating film and the plating solution and washed three times, followed by 0.3 g / l of palladium chloride. The solution was activated for 4 minutes in a 30% solution of 3% hydrochloric acid and washed three times. After completion of washing with water, the electroless solution of copper chloride (CuCl ₂ ) 5g / ℓ formalin (HCHO) 3g / ℓ, EDTA-4 sodium 48g / ℓ, sodium hydroxide (NaOH) 7g / ℓ was prepared at pH 12.7, temperature 45 ℃. Then, the conductive coated polycarbonate plate was deposited, plated for 1 hour and 20 minutes, washed with water three times, and again treated with Palladium chloride 0.3 g / L hydrochloric acid 3% in a 30 ° C. solution for 1 minute, and washed twice. Do not leave the activated and washed objects in the air immediately, but 6 g / l of nickel sulfate (NiSO ₄ ), 40 g / l of sodium hypophosphite (NaH ₂ PO ₂ ), and 40 g / l of sodium citrate as aqueous ammonia (NH ₄ OH). It adjusted to PH 8.8 and electroless nickel plating was performed to the liquid mixture which is 37 degreeC. The electrical resistance values of the single-sided plating thus prepared are shown in Table 4, and the electrical conductivity change with respect to chemical environment change is shown in Table 3, Table 4, and Table 5, respectively. Shown in

The one-sided electroless plating method of the present invention as described above is a surface treatment method for electromagnetic shielding having effects such as excellent electromagnetic shielding characteristics, uniformity of coating film, ease of single-sided surface treatment of conductive paint, and variety of selection of workpiece plastic materials.

Claims (1)

Degreasing and washing the plastic plated product with a plastic degreasing agent such as 60 g / l of a degreasing agent (PC-200), drying, cooling it to 35-40 ° C., and then conducting conductive coating with a conductive paint for 35-40 minutes. After being left to stand and dried at 60 to 65 ° C. for 1 hour and then at room temperature for 3 hours or longer, alkali degreasing treatment is performed for 5 to 7 minutes again, and 0.2 to 0.3 g / l of palladium chloride (PdCl ₂ ) and hydrochloric acid (HCI). Activation and washing in 3% mixed aqueous solution for 3 to 5 minutes, followed by 5-6 g / l copper chloride (CuCl ₂ ), formalin (HCHO) 2-3 g / l, EDTA-4 sodium 45-56 g / l, hydroxide In electroless plating solution of sodium 6-7g / l PH 12-13, it was immersed at 45-50 ℃ for 1 hour 20 minutes, electroless copper plating, washed three times, and again 0.2-0.3g of palladium chloride (PdCl ₂ ) / ℓ hydrochloric acid was replaced 3% 30 ℃ 1~2 minutes in a mixed aqueous solution of the coating, and then twice washed with water, and nickel sulfate (NiSO ₄₎ 5~7g / ℓ, and hypophosphorous acid, or Cerium _{(NaH 2 PO 2) 30~50g /} ℓ of citric acid was mixed with sodium 30~50g / ℓ of aqueous ammonia (NH ₄ OH) to adjust the PH to 8.5 to 9.0 for 20 minutes at a temperature in the electroless nickel plating as a 35~40 ℃ Single-sided electroless plating method for shielding electromagnetic waves by washing with water.