KR20140013180A

KR20140013180A - Electroless plating method of optical fiber

Info

Publication number: KR20140013180A
Application number: KR1020120079097A
Authority: KR
Inventors: 유기석
Original assignee: 주식회사 마이크로테크
Priority date: 2012-07-20
Filing date: 2012-07-20
Publication date: 2014-02-05

Abstract

The present invention relates to an optical fiber plating method, and more particularly, to an optical fiber plating method capable of forming a uniform and durable gold plating layer on the outside of an optical fiber in an electroless manner.
In the electroless fiber plating method of the present invention, an etching step of increasing the roughness of the surface of the clad by immersing the optical fiber exposed to the clad with the cladding to remove the coating layer, and an activation step of forming a catalyst layer on the surface of the clad after the etching step And a nickel plating step of immersing the optical fiber on which the catalyst layer is formed in a nickel plating solution to form a nickel plating layer outside the catalyst layer, and a gold plating step of immersing the optical fiber having the nickel plating layer in a gold plating solution to form a gold plating layer outside the nickel plating layer. Include.

Description

Electroless plating method of optical fiber

The present invention relates to an optical fiber plating method, and more particularly, to an optical fiber plating method capable of forming a uniform and durable gold plating layer on the clad surface of an optical fiber in an electroless manner.

BACKGROUND OF THE INVENTION In optical communication systems using optical fibers, many require the ability to solder optical fibers to interconnect one another, to align with optical devices such as lasers and optical detectors, or to hermetic packaging.

Republic of Korea Patent No. 0511398 discloses a method for plating a metal on the outside of the optical fiber.

PVD (Physical Vapor Deposition) method of vaporizing silver, mercury, aluminum or nickel to be deposited in a gaseous state by vapor deposition using a plating method disclosed in the prior art, or vaporizing silver, mercury, aluminum or nickel once in a gaseous state Chemical Vapor Deposition (CVD) has been applied to transport and cause chemical reactions on the surface. However, the plating method by evaporation tends to be expensive and to form a non-uniform coating film and to weaken the optical fiber.

In addition, an electrolysis method is disclosed as another example of the plating method. The electrolytic method uses the optical fiber to be plated as a cathode, the metal to be electrodeposited as an anode, and puts it in an electrolyte containing ions of the metal to be electrodeposited, and conducts electricity to deliver the desired metal ions. It is a principle that precipitates on the surface of things.

However, electrolytic plating can form a film having good adhesion at a relatively low cost, and thus may be suitable for industrial machine parts, but it is difficult to form a precise film on a fine material such as optical fiber, discoloration, stains, etc. There is a problem that occurs. Therefore, there is a need for a reliable method for metal plating of optical fibers.

The present invention has been made to improve the above problems, by applying an electroless method capable of plating a metal to the optical fiber using a reduction reaction in solution to form a uniform and durable gold plating layer on the clad surface of the optical fiber. The purpose is to provide an optical fiber plating method.

An electroless optical fiber plating method of the present invention for achieving the above object includes an etching step of increasing the roughness of the clad surface by immersing the optical fiber exposed clad in the etching solution to remove the coating layer; An activation step of forming a catalyst layer on the clad surface after the etching step; A nickel plating step of immersing the optical fiber on which the catalyst layer is formed in a nickel plating solution to form a nickel plating layer outside the catalyst layer; And a gold plating step of forming a gold plating layer outside the nickel plating layer by immersing the optical fiber having the nickel plating layer formed in a gold plating solution.

The etching step is characterized by using a solution in which ammonium fluoride and hydrofluoric acid is mixed as the etchant, and immersing the optical fiber in the etchant while generating ultrasonic waves in the etchant.

The activating step includes a) immersing the optical fiber in a first solution of tin chloride and hydrochloric acid mixed at 25 to 35 ° C. for 5 to 10 minutes to adsorb tin ions to the clad surface, and b) 25 to 35 ° C. And immersing the optical fiber in a second solution mixed with palladium chloride and hydrochloric acid for 5 to 10 minutes to form the catalyst layer made of palladium on the clad surface.

The activation step is characterized in that the catalyst layer made of palladium on the surface of the clad by immersing the optical fiber in a third solution mixed with tin chloride, palladium chloride, hydrochloric acid at 50 to 70 ℃ for 5 to 10 minutes.

In the nickel plating step, the nickel plating solution is a solution in which nickel sulfate, ammonium acetate, and sodium hypophosphite are mixed, and the gold plating solution is a solution in which gold cyanide, sodium cyanide, and sodium carbonate are mixed. .

As described above, according to the present invention, an electroless method using a reduction reaction can be applied to form a uniform gold plating layer on the clad surface of the thin optical fiber.

In addition, it is expected that the adhesion and durability of the plating layer formed on the surface of the clad may be increased by increasing the roughness of the clad surface of the optical fiber by performing etching with acid as a pretreatment process before plating.

Hereinafter, an electroless fiber plating method according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

The present invention largely includes an etching step, an activation step, a nickel plating step, and a gold plating step. It will be described in detail step by step.

1. Etching Step

A typical optical fiber consisting of a core and a cladding surrounding the core is covered with a coating layer on the outside of the clad. Therefore, after removing the coating layer of the portion to be plated, the surface of the clad is plated. The coating layer can be removed by a mechanical device such as a stripper or by a chemical method with a strong acid.

After the coating layer of the optical fiber is removed, an etching step is performed. Through the etching step, fine irregularities may be formed on the surface of the clad to effectively increase the roughness of the surface. By increasing the roughness of the surface, the adhesion and durability of the plated film formed on the clad surface can be improved.

As the etching solution, a solution in which ammonium fluoride (NH ₄ F) and hydrofluoric acid (HF) are mixed is used. Ammonium fluoride and hydrofluoric acid may be mixed in a weight ratio of 2 to 15: 1. For example, an ammonium fluoride solution having a concentration of 50%: hydrofluoric acid: water having a concentration of 49% is mixed with an etching solution in a weight ratio of 2 to 15: 1: 1. When only hydrofluoric acid is used, an uneven etching may be formed on the surface of the clad, but an etching solution in which ammonium fluoride is added to hydrofluoric acid induces uniform etching.

The coating layer is removed, and the clad-exposed optical fiber is immersed in an etchant for 5 to 10 minutes at room temperature (20-25 ° C.) to perform an etching step. In the optical fiber immersed in the etchant, the surface of the clad is corroded by the etchant to increase the surface roughness. After etching, the etching site is washed with distilled water to remove the etching solution.

On the other hand, the above-described etching step can be performed while generating ultrasonic waves in the etching solution. Ultrasonic agitation of the etchant helps to achieve a uniform etch over the entire surface of the clad. For this purpose, ultrasonic generating means may be installed in the bath stored in the etchant. Ultrasonic generating means includes an ultrasonic vibrator installed on the bottom or side of the bathtub, and ultrasonic control unit for adjusting the frequency of the ultrasonic vibrator. The ultrasonic controller is electrically connected to the ultrasonic vibrator and is disposed outside the bathtub.

2. Activation step

The activation step forms a catalyst layer on the clad surface of the etched optical fiber. The catalyst layer serves to reduce nickel (Ni ² ⁺ ) to be described later.

As an example of the activation step, the optical fiber is immersed in the first solution of tin chloride and hydrochloric acid to adsorb tin ions to the clad surface, and the optical fiber is immersed in the second solution of palladium chloride and hydrochloric acid to palladium on the clad surface. It may be made of a step of forming a catalyst layer consisting of.

Tin ion (Sn ⁺ ²⁾ is a sensitizer (sensitizer) serves to facilitate the formation of a palladium catalyst. When stannous chloride (SnCl ₂₎ and hydrochloric acid (HCl) dipping the fiber in the first solution are mixed is adsorbed on the cladding surface etching is stannous ion (Sn ⁺ ²⁾ in the solution.

As a first solution, a solution obtained by dissolving tin chloride in a ratio of 15 to 25 g / l in hydrochloric acid having a concentration of 36% is used. It is preferable to immerse the optical fiber in the first solution for 5 to 10 minutes at 25 to 35 ℃.

Tin ion-sensitized surface of the cladding to the adsorption of (Sn ⁺ ²⁾ is by washing with distilled water and then immersed in an optical fiber to the second solution to form a catalyst layer on the surface of the cladding.

As a second solution, a mixture of palladium chloride (PdCl ₂ ) and hydrochloric acid (HCl) is used. For example, the second solution may be a solution in which palladium chloride is dissolved in a ratio of 3 to 7 g / l in hydrochloric acid having a concentration of 36%. It is preferable to immerse the optical fiber in the second solution for 5 to 10 minutes at 25 to 35 ℃.

When the clad comes into contact with a second solution containing palladium ions (Pd ² ⁺ ), an oxidation-reduction reaction occurs, whereby tin ions are oxidized from Sn ² ⁺ to Sn ⁴ ⁺ , and palladium ions (Pd ²⁺ ) are zero-valent palladium. It is reduced to metal (Pd ⁰ ) to form a catalyst layer on the surface of the clad. After forming a catalyst layer made of palladium, it was immersed in hydrochloric acid at a concentration of 5% for about 3 minutes and then washed with distilled water.

On the other hand, it is possible to perform the formation of a palladium catalyst and adsorption of tin ion (Sn ⁺ ²⁾ other examples carried out in solution, a type of contrast to the activation step described above of the present invention at the same time. For example, in the activation step, an optical fiber etched on the surface of the clad in the etching step is immersed in a third solution to form a catalyst layer on the surface of the clad.

As a third solution, a solution containing tin chloride, palladium chloride, and hydrochloric acid may be used. For example, the third solution is a solution of 25 to 50 g / l tin chloride and 2 to 10 g / l palladium chloride in 36% hydrochloric acid. The third solution is when the fiber is immersed for 5-10 minutes at 50 to 70 ℃ the tin ion (Sn ⁺ ²⁾ is adsorbed soon as the clad surface is simultaneously oxidized by the palladium ion (Pd ² ^+), palladium ion (Pd ²⁺ ) Is reduced to ^zero- valent palladium metal (Pd ⁰ ) to form a catalyst layer on the surface of the clad. After the formation of the catalyst layer made of palladium, the surface of the clad is washed with distilled water.

3. Nickel Plating Step

After the catalyst layer is formed, a nickel plating step is performed in which the optical fiber is immersed in a nickel plating solution to form a nickel plating layer outside the catalyst layer.

60 to 80 g of nickel sulfate (NiSO ₄ 6H ₂ O), 5 to 15 g of ammonium acetate (CH ₃ COONH ₄ ) and 15 to 25 g of sodium hypophosphite (NaH ₂ PO ₂ 2H ₂ O) were mixed with a nickel plating solution. Solutions may be used. The pH of the nickel plating solution can be adjusted to 6.

Nickel ions (Ni ²⁺ ) in the nickel plating solution are reduced to nickel valent metal (Ni ⁰ ) by sodium hypophosphite as a reducing agent. In addition to the sodium hypophosphite, ammonium, potassium combined hypophosphite, dimethylamine borane, sodium borohydride, phosphites (ammonium, potassium, ammonium salts, etc.), formate (ammonium, sodium, potassium, calcium salts, etc.) Single or mixtures of two or more may be used.

When reducing nickel ions (Ni ²⁺ ), the zero valent palladium (Pd ⁰ ) acts as a catalyst to promote the reduction reaction. The nickel plating step is carried out in a nickel plating solution of 55 to 65 ℃. Proper temperature control is important because the plating effect of nickel is rapidly reduced at low temperatures and unnecessary nickel plating can occur on the inner surface of the bath stored in the nickel plating solution at high temperatures.

In the clad contacting the nickel plating solution, nickel is grown outside the catalyst layer to form a nickel plating layer. Nickel plated layer is thicker in proportion to the immersion time, it may be 4 to 6㎛ as a preferred thickness.

4. Gold Plating Step

The cladding on which the nickel plating layer is formed is washed with distilled water and then immersed in a gold plating solution to perform a gold plating step of forming a gold plating layer outside the nickel plating layer.

As a gold plating solution, a solution containing 3 to 5 g of potassium cyanide (KAu (CN) ₂ ), 25 to 50 g of sodium cyanide (NaCN), and 30 to 50 g of sodium carbonate (Na ₂ Co ₃ ) may be used as a gold plating solution. The pH of the gold plating solution can be adjusted to 4.6.

Gold ions in the gold plating solution are adsorbed and reduced outside the nickel plating layer to form a gold plating layer. Gold plating step may be performed in a gold plating solution of 80 to 90 ℃. The immersion time is 10 to 20 minutes, in which case a gold plated layer having a thickness of 0.2 to 0.4 µm can be obtained. After the gold plated layer is formed, the clad may be finally washed with distilled water and dried to prepare a gold plated optical fiber.

Although the present invention has been described with reference to the embodiments, these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent embodiments are possible therefrom. Accordingly, the true scope of protection of the present invention should be determined only by the appended claims.

Claims

An etching step of removing the coating layer and immersing the clad-exposed optical fiber in an etching solution to increase the roughness of the clad surface;
An activation step of forming a catalyst layer on the clad surface after the etching step;
A nickel plating step of immersing the optical fiber on which the catalyst layer is formed in a nickel plating solution to form a nickel plating layer outside the catalyst layer;
And a gold plating step of immersing the optical fiber on which the nickel plating layer is formed in a gold plating solution to form a gold plating layer on the outside of the nickel plating layer.

The method of claim 1, wherein the etching step uses a solution in which ammonium fluoride and hydrofluoric acid are mixed as the etching solution,
The electroless plating method of the electroless type, characterized in that the optical fiber is immersed in the etching solution while generating ultrasonic waves in the etching solution.

The method of claim 1, wherein the activating step comprises: a) adsorbing tin ions to the clad surface by immersing the optical fiber in a first solution of tin chloride and hydrochloric acid mixed at 25 to 35 ° C. for 5 to 10 minutes; b) electrolessly immersing the optical fiber in a second solution in which palladium chloride and hydrochloric acid are mixed at 25 to 35 ° C. for 5 to 10 minutes to form the catalyst layer made of palladium on the surface of the clad. Optical fiber plating method.

The method of claim 1, wherein the activating step is to immerse the optical fiber in a third solution of tin chloride, palladium chloride, hydrochloric acid for 5 to 10 minutes at 50 to 70 ℃ to form the catalyst layer made of palladium on the clad surface Electroless plating method of the electroless type, characterized in that.

The method of claim 1, wherein the nickel plating solution in the nickel plating step is a mixture of nickel sulfate, ammonium acetate, sodium hypophosphite,
In the gold plating step, the gold plating solution is an electroless plating method of the electroless type, characterized in that the solution is a mixture of gold cyanide potassium, sodium cyanide, sodium carbonate.