KR100321802B1 - Method of Silver-plating Microwave Band Pass Cavity Filter Products - Google Patents

Abstract

The silver plating method of the micro waveguide product of the present invention comprises a process of pretreating the material to be plated, subjecting the pretreated product to an electroless nickel plating method, and finally subjecting the underlying plated product to a silver plating process. The pretreatment step is also performed in a conventional plating method, and this step varies slightly depending on the material of the product. For example, in the case of aluminum material, a pretreatment process consisting of degreasing, alkali treatment, dismuting, and alkaline lead substitution treatment is performed. In the case of a general steel alloy material, pretreatment consisting of alkali degreasing, pickling, electrolytic degreasing, and activation is performed. The process is performed. The base plating process is a process of electroless nickel plating of a finished product, and further electro-plating 3 to 10 탆 thick on the electroless nickel plating layer in a high frequency region other than the frequency band which is possible only by electroless nickel plating. . The silver plating process is to perform silver plating on the electroless nickel plating layer or the copper plating layer after the electroless nickel plating in which the underlying plating treatment process is completed.

Description

Silver Plating Microwave Band Pass Cavity Filter Products

Field of invention

The present invention relates to a method for silver plating micro waveguide products. More specifically, the present invention relates to a method for silver plating a micro waveguide product made of aluminum or aluminum alloy material, this method is a pre-treatment of the material to be plated according to a conventional method, the electroless nickel The process consists of the process of performing the plating process which is the plating base material, and finally the silver plating process of the product which has been plated. Micro waveguide products made in accordance with the method of the present invention prevent high frequency loss, maintain high reliability, and have good durability.

Background of the Invention

Today, due to the rapid increase in demand for satellite communication, optical communication and personal cell phones, transmitters, receivers, duplexers, wave guides, etc. for CDMA and AMPS are mass-produced. It is installed. Various micro waveguide products are used in these equipments, but plating methods that can maintain the high frequency loss prevention, high reliability, and durability required by these products have not been developed yet. Therefore, a conventional micro waveguide product causes a deterioration in communication quality and requires a huge budget for post-processing of already installed products.

Micro waveguide products are made of aluminum or aluminum alloy. Among these materials, impurities such as zinc, magnesium, silicon, copper, etc. diffuse and penetrate through the pin holes of the silver plated layer to form oxides. It exists as an impurity of a silver plating layer. These impurities lower the electrical conductivity and cause high frequency loss, which in turn degrades the performance of the micro waveguide and degrades the communication quality.

In the case of applying a high frequency region of MHz or more using a micro waveguide, a phenomenon in which the high frequency current has a maximum current density in the surface layer is called a skin effect. In order to achieve the desired area characteristics of a micro waveguide product, a plating process must be adopted to reduce the AC loss.

In general, the factors affecting the high frequency AC loss of the micro waveguide products have been found to be the surface roughness of the waveguide inner surface and the plating method.

The surface roughness of the inner surface of the waveguide should be as smooth as possible, and the surface roughness should be in the range of 5.0 to 8.0 탆.

Regarding the plating method, the plating layer of the micro waveguide should maintain a uniform plating thickness on the inner surface. In order to obtain a uniform plating layer, a plating method suitable for a complicated shape product should be used, and an appropriate plating solution should be selected. As a plating method suitable for a product having a complicated shape, there is a method of applying a dedicated auxiliary jig (JIG). By selecting an appropriate plating solution, the uniform electrodeposition and surface smoothness can be improved, the electrical resistance can be reduced, and the adhesion strength with the material layer can be improved.

The plating layer of a micro waveguide may thinly plate silver or gold in the case of consisting only of copper plating and for the purpose of rust prevention of copper on copper plating. In the case of silver plating on copper plating, silver emulsification (AgS) is generated due to the effect of emulsion gas in the air, which may cause high frequency transmission loss. However, in the case of copper plating alone, there is no problem in the MHz band because the copper emulsion layer is not thicker than the silver plating layer. However, the thickness uniformity and surface smoothness of the plating layer should be good, and the electrical resistance of the plating layer should be small. Therefore, it is very important to form a functional surface in the plating layer.

In addition, the plating thickness of the plating layer has an important relationship with the physical properties, that is, the skin effect in the high frequency region, which can also be expressed as follows.

δ = 1 / πσμ × λ ₀

Where δ is the skin effect layer thickness, σ is the conductivity, μ is the speed of light, and λ ₀ is the wavelength of free space (C / F).

As shown in the above formula, π and μ are constants, and the larger the sigma, the smaller the δ. The better the conductivity of the plating layer, that is, the smaller the electrical resistance, the thinner the plating layer (skin effect layer) may be.

The inventors have developed a method of the present invention which can plate a micro waveguide product to prevent high frequency loss and to have high reliability and durability by removing defects of the micro waveguide product manufactured from the conventional plating method as described above. It is early.

It is an object of the present invention to provide a plating method capable of manufacturing a micro waveguide product capable of preventing high frequency loss.

Another object of the present invention is to provide a plating method capable of manufacturing a micro waveguide product capable of maintaining high reliability and durability.

Another object of the present invention is to provide a plating method for manufacturing a micro waveguide product which can improve the communication quality by preventing the diffusion of impurities into the silver plating layer of the micro waveguide.

Another object of the present invention is to provide a plating method for manufacturing a micro waveguide product that can improve the reliability of the micro waveguide equipment at the base station.

The above and other objects of the present invention can be achieved by the present invention described below.

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

The silver plating method of the micro waveguide product of the present invention comprises a process of pretreating the material to be plated, subjecting the pretreated product to an electroless nickel plating method, and finally subjecting the underlying plated product to a silver plating process.

The pretreatment step is also performed in a conventional plating method, and this step varies slightly depending on the material of the product. For example, in the case of aluminum material, a pretreatment process consisting of degreasing, alkali treatment, dismuting, and alkaline lead substitution treatment is performed. In the case of a general steel alloy material, pretreatment consisting of alkali degreasing, pickling, electrolytic degreasing, and activation is performed. The process is performed.

The base plating process is a process of electroless nickel plating of a finished product, and further electro-plating 3 to 10 탆 thick on the electroless nickel plating layer in a high frequency region other than the frequency band which is possible only by electroless nickel plating. .

The silver plating process is to perform silver plating on the electroless nickel plating layer or the copper plating layer after the electroless nickel plating in which the underlying plating treatment process is completed.

As described above, the silver plating method of the micro waveguide product of the present invention is composed of a pretreatment step, a base plating treatment step, and a silver plating treatment step.

The pretreatment process varies slightly depending on the material of the product, but in the case of an aluminum material, it is typically composed of degreasing, alkali treatment, desmut treatment and alkaline lead substitution. Representative examples of the aluminum material for the micro waveguide include aluminum extrusion processing material and aluminum die casting material.

First, degreasing treatment of aluminum material is a process for removing machine covalently attached to aluminum alloy. When the machine is adhered to the aluminum alloy layer, it is necessary to remove the oil completely by using a degreasing agent exclusively for aluminum because it causes a poor plating and an uneven plating layer is formed. The degreasing treatment is completed by holding at a pH of 9.5 to 10.5 and a temperature of 50 to 60 DEG C for 10 to 20 minutes and performing ultrasonic cleaning for 3 to 5 minutes.

When the degreasing treatment is completed, an alkali treatment is performed to improve the adhesion strength between the material and the plating layer. Alkaline treatment is carried out in a 5 to 10% by weight caustic soda solution at a temperature of 30 to 40 ° C. for 15 to 30 seconds.

When the alkali processing is completed, the destomping process is performed. The desmitting process is a process for removing metal impurity salts on the surface generated during alkali treatment. The dimmer treatment is an acidic solution containing 30% by volume nitric acid solution or 5% by volume hydrofluoric acid solution at room temperature for 10 to 20 seconds. The dimmer treatment removes metal salt impurities adhering to the product surface.

When the desmuting process is completed, an alkaline lead substitution process is performed. Alkaline lead substitution treatment is a step performed for the purpose of preventing oxidation during the treatment of aluminum material or during the movement between processes. In other words, the chemical surface treatment of the aluminum material surface layer with a metal compound of zinc, nickel, iron, or copper is used to prevent oxidation of the aluminum material surface layer, thereby improving adhesion to the metal nickel layer. Alkaline lead substitution is performed for 30 to 90 seconds in a mixed solution of a zinc compound and a caustic soda compound solution. Alkaline lead substitution treatment can be performed by the first substitution treatment as described above, but in order to improve reliability, the first treated product is added to 30 vol% nitric acid solution to dissolve zinc substituted metal and secondly, alkaline lead replacement treatment is performed. You can also do it. Alkaline lead substitution treatment is a process for forming a zinc-substituted protective film in order to completely prevent the formation of an oxide film during the plating process of the surface layer of the aluminum material.

When the material of the product is a general steel alloy material, a pretreatment process consisting of alkaline degreasing, pickling, electrolytic degreasing, and activation steps is performed, and this pretreatment process can be easily performed by a person skilled in the art. have.

The underlying plating treatment process according to the present invention is a process of electroless nickel plating of the finished product. Micro waveguide products are complex in shape and structure, have a lot of screws and adjustment bolt holes to keep the product completely sealed. Therefore, it is very difficult to obtain a uniform and smooth surface layer when electroplating these products. In addition, the adhesion of the effective surfaces inside these products should be enhanced and the diffusion of impurities into the silver plating layer on the aluminum alloy material should be prevented. The underlying plating process in the present invention is performed for this purpose. That is, as the base plating of silver plating, it has the best adhesion with an aluminum alloy material, the corrosion resistance is about five times that of the electric nickel, and the acidic electroless nickel plating which has a nonmagnetic characteristic is performed. The acidic solution for electroless nickel plating consists of 4.0 to 8.0 g / l nickel sulfate, 25 to 35 g / l sodium hypophosphite and 20 to 50 g / l complexing agent, to which caustic soda is added as a pH regulator. .

In the case where the electrical conductivity of the electroless nickel plating layer is insufficient only in the high frequency region other than the frequency band which is possible only by electroless nickel plating, electrocopper plating is performed with a thickness of 3 to 10 µm. The copper copper plating solution used at this time includes an alkali copper cyanide plating solution, an acidic copper sulfate plating solution and a copper pyrophosphate plating solution.

When the base plating process is completed, silver plating is performed. Silver plating is performed on the electroless nickel plating layer or the copper plating layer after electroless nickel plating. Silver plating is a process to reduce high frequency losses. Silver plating is performed by silver-strike plating in order to improve adhesiveness with an electroless nickel plating layer or the copper plating layer after electroless nickel plating, and silver plating of 6-12 micrometers thick is again performed on it. The thickness of the silver plating is determined based on the thickness of the bottom portion of the micro waveguide because the current density at the bottom portion is the lowest. The composition of the silver strike solution used in the present invention is composed of 1 to 2 g / l of silver cyanide and 60 to 150 g / l of potassium cyanide, and the plating method is performed at a voltage of 6 to 7 V and a current density of 2 to 3 A / dm 2. 5 to 10 seconds at room temperature. When the silver strike plating is completed, silver plating is performed. The composition of the silver plating solution is composed of 35 to 50 g / l of silver cyanide, 70 to 115 g / l of potassium cyanide and 10 g / l of potassium carbonate, at a temperature of 20 to 30 ° C. Silver plating is performed at a current density of 0.4 to 1.0 A / dm 2 at.

The present invention will be further illustrated by the following examples, but the following examples are only described for the purpose of illustrating the present invention and are not intended to limit the protection scope of the present invention.

Example

Silver plating of the micro waveguide was carried out according to the method of the present invention as follows.

(1) Pretreatment Process

A micro waveguide made of an aluminum extruded material was maintained at a pH of 10.0 at 55 ° C. for 15 minutes, degreased by ultrasonic cleaning for 4 minutes, treated in an 8 wt% caustic soda solution at 35 ° C. for 20 seconds, and 30 volume% nitric acid solution at room temperature. The solution was immersed in for 15 seconds, treated for 60 seconds in a solution of zinc compound and caustic soda compound, dissolved in 30% by volume nitric acid solution, and further subjected to alkaline lead replacement.

(2) Under plating process

The micro waveguide in which the pretreatment was completed was plated with an electroless nickel plating solution consisting of 6.0 g / l nickel sulfate, 30 g / l sodium hypophosphite and 40 g / l complexing agent. It was again plated with an alkali copper plating solution.

(3) Silver Plating Process

The plated micro waveguide was plated with a silver strike solution consisting of 1.5 g / l silver cyanide and 90 g / l potassium cyanide, on top of which 45 g / l silver cyanide, 95 g / l potassium cyanide and 10 g / l It was plated with a silver plating solution made of potassium carbonate. Since the electroless nickel plated layer or the electroless nickel plated layer and the electro-copper plated layer are formed before the silver plated layer prepared according to the method of the present invention, impurities can be prevented from being diffused into the silver plated layer of the micro waveguide. Improve the reliability and durability of micro waveguide products.

The present invention can prevent high frequency loss, maintain high reliability and durability, and can prevent the diffusion of impurities into the silver plating layer of the micro waveguide to improve communication quality, and improve the micro waveguide equipment of the base station. The invention has the effect of producing a micro waveguide product capable of improving reliability.

Simple modifications and variations of the present invention can be readily used by those skilled in the art, and all such variations or modifications can be considered to be included within the scope of the present invention.

Claims (5)

Pretreat the micro waveguide product to be silver plated; The pre-treated micro waveguide product is composed of 4.0 to 8.0 g / l nickel sulfate, 25 to 35 g / l sodium hypophosphite and 20 to 50 g / l complexing agent, and is electroless with an acidic solution containing caustic soda as a pH adjuster. Nickel under plating; And Silver plating the underlying plated micro waveguide product; A silver plating method of a micro waveguide product, characterized in that consisting of a step. The method of claim 1, wherein when the micro waveguide product is made of aluminum, the pretreatment process includes degreasing, alkali treatment, desmut treatment, and alkaline lead substitution. 2. The method of claim 1, wherein when the micro waveguide product is made of a steel alloy material, the pretreatment process comprises alkaline degreasing, pickling, electrolytic degreasing and activation. The method of claim 1, wherein the base plating process further comprises electroplating 3 to 10 mu m thick on the electroless nickel plated layer. 2. The silver plating process according to claim 1, wherein the silver plating process comprises performing a silver strike plating with a plating liquid consisting of 1 to 2 g / l silver cyanide and 60 to 150 g / l potassium cyanide, and 35 to 50 g / l silver cyanide, 70 to 115 g / l. A silver plating method of a micro waveguide product, comprising the step of silver plating with a silver plating solution consisting of l potassium cyanide and 10 g / l potassium carbonate.