KR100499793B1 - Electroless plating method - Google Patents

Abstract

 The present invention discloses a method of forming a nickel film by an electroless plating method on a plated object made of a material selected from the group consisting of precious metals, stainless steels, and molybdenum steels. The method comprises the steps of electropolishing the surface of the workpiece; Forming a first plated layer by performing an electro-nickel strike plating process on the electroplated workpiece. Forming a second plating layer on the first plating layer by performing electroless nickel plating on the plated object; And immersing the plated object in an electroless nickel liquid containing a fluorine resin to form a third plating layer.

Description

Electroless Plating Method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electroless plating, and more particularly, to an electroless plating treatment method for forming an electroless plating film using electroless plating on the surface of an electropolished object.

Fluorine resins have characteristics that are extremely resistant to chemicals, have excellent electrical properties, and are stable even at high temperatures, and coating of the fluororesin film on the surfaces of mechanical parts, electrical parts, and electronic parts is generally performed. In order to improve the adhesiveness with respect to the to-be-processed object of such a fluororesin film, after the process which roughens the surface of a to-be-processed object beforehand, the method of coating a fluororesin is generally performed. Further, after the plated object is treated with an inorganic or organic binder, a method of coating the fluorine resin relatively thick so that the layer thickness is about 100 to 200 µm is also performed (for example, Japanese Patent Laid-Open No. 2001-A). 328121, Japanese Patent Laid-Open No. 2000-328256, Japanese Patent Laid-Open No. 4-365875, Japanese Patent Laid-Open No. Hei 1-60584, Japanese Patent Laid-Open No. 61-234202, Japanese Patent Laid-Open No. 51-1112348) . However, in the method of coating the fluorine resin on the rough surface after roughly forming the surface of the object to be treated as in the conventional art described above, the following problems may occur depending on the uneven shape. In other words, when a rough surface having an uneven shape in which the height between the recess and the protrusion is not very high is about 1 μm, the plating layer made of fluorine resin fills the recess so that the height of the unevenness is almost eliminated, and the adhesion of the fluorine resin It was remarkably low and there existed a problem that peeling etc. generate | occur | produce. In addition, since the fluorine resin is relatively expensive, there is a demand in the market to reduce the layer thickness of the fluorine resin, to reduce the amount of the fluorine resin used, and to achieve low cost. However, simply thinning the coating of the fluororesin is extremely poor in adhesion due to the low coefficient of friction between the fluororesin and the fluororesin coating, and it is impossible to form a fluororesin coating film having a thin layer thickness and easy pinholes. There was a problem.

In addition, International Publication No. WO 2004/024985 discloses a first plating layer by exposing an object to be treated with a first plating solution containing at least one selected from a composition solution containing aqueous ammonia and thiourate, and thiourea. It is disclosed to form a thin film of a fluororesin coating film having good adhesion by exposing to a second plating solution containing a fluorine resin on the surface of the second plating layer. However, the above prior art easily peels off the plating layer when the material to be processed is a noble metal, stainless steel or molybdenum steel. That is, as shown in FIG. 1, the height difference between the protrusions 12 and the recesses 14 of the unevenness formed on the surface of the plated object 10 is so great that a pinhole in the uneven groove is formed when the first plating layer is formed. This easily occurs, and these pinholes act to increase the likelihood of peeling of the plating layer.

Accordingly, the present invention has been made to solve the above problems, an object of the present invention is to provide an electroless plating method that can be applied to the object to be made of precious metals, stainless steel or molybdenum steel.

Another object of the present invention is to provide an electroless plating method which can increase the adhesion of the plated layer to the plated material by suppressing pinhole generation between the plated layer and the plated object.

In order to achieve the above object, the electroless plating method according to an aspect of the present invention, the electropolishing the surface of the plated by applying a positive voltage to immerse the plated in the electrolyte solution to function as an anode ( electroplating), electroplating the electroplated workpiece to form a first plating layer functioning as a protective layer, and forming a metal salt on the plating target including the first plating layer. Forming a second plating layer containing a fluororesin by electroless plating in a first electroless plating solution including; The first plating layer is a nickel layer when the plated material is stainless steel, the second plating layer is a nickel layer containing a fluorine resin. The electroless plating method according to another aspect of the present invention And electropolishing the surface of the plated object by applying a positive voltage so as to function as an anode by immersing the plated object in an electrolyte solution, and electroplating the electroplated object to be electroplated. Forming a first plating layer functioning as a protective layer, and electroless plating the first plating layer including the first plating layer in a first electroless plating solution containing a metal salt to contain a second fluorine resin. Forming a plating layer; The first plating layer is a zinc layer when the plated object is an aluminum alloy, and the second plating layer is a nickel layer containing a fluororesin.

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EMBODIMENT OF THE INVENTION Hereinafter, the preferable form of the electroless plating method which concerns on this invention is demonstrated in detail.

Electroless plating treatment method according to the invention, the step of electrolytic polishing the surface of the plated object; Forming a first plated layer by subjecting the electroplated workpiece to an electric strike plating process using a metal having a high adhesive strength with the plated article; Forming a second plating layer on the first plating layer by electroless plating the plated object including the first plating layer in a first electroless plating solution containing a metal salt; And electroless plating the plated material including the first and second plating layers in a second electroless plating solution containing a fluorine resin to form a third plating layer.

The electropolishing process, which is the first process of the electroless plating method according to the present invention, is first described.

As illustrated in FIG. 2, in the electropolishing process, the first electrode 20, the second electrode 30, and the electrolyte are prepared. A positive voltage is applied to the plated object, which is the first electrode 20, that is, the plated object acts as an anode, and a negative voltage is applied to the second electrode 30 so that the second electrode 30 is a cathode. To work.

As the voltage is applied, the surface of the plated object 20 serving as the anode is electrically polished. Specifically, the surface of the electroplated workpiece 20 has a structure in which protrusions and recesses alternately appear, as shown by a dotted line in FIG. 3. As mentioned above, the depth of the concave portion before electropolishing is very deep, but as shown by the solid line in FIG. The height difference between the top surface of the protrusion 22 and the bottom surface of the recess 24 is reduced. As a result, the likelihood of pinhole generation in the recess decreases, and the adhesion between the surface of the plated material and the plating layer increases. For this reason, the possibility of peeling of a plating layer becomes remarkably low. That is, the surface roughness of the plated material after the electropolishing process is completed is reduced and the gloss is significantly increased.

After the electropolishing process is completed, the plated material is preferably plated over three times. That is, one electroplating and two electroless platings are performed.

Optionally, after completion of the electrolytic polishing process, the electroless plating process containing fluorine resin may be performed only once.

In addition, after completion of the electrolytic polishing process, the electroless plating process containing no fluorine resin and the electroless plating process containing fluorine resin may be performed once each.

The electroless plating solution (first and second electroless plating solutions) according to the present invention contains a metal salt, a metal complexing agent, a reducing agent, and a composition liquid containing ammonia water and thio lactate.

Electroless plating employed in the present invention is a method of plating on a workpiece without passing through a current.

The substrate may be a base substrate made of various materials such as metal, aluminum, rubber, or synthetic resin. Preferably, products made of a material such as precious metal, stainless steel, and molybdenum steel are used.

The metal salts contained in the electroless plating solution include nickel salts, zinc salts, cobalt salts, chromium salts, titanium salts, hypochlorite salts, and the like, but may be used alone or in combination, but is not limited thereto. It is preferable that it is at least 1 sort (s) or more chosen from the group which consists of a nickel salt and a zinc salt.

As the metal complexing agent contained in the electroless plating solution of the present invention, it is preferable to use nitric acid, succinic acid or lactic acid as an organic substance or the like forming a complex with a metal salt.

The fluorine resin refers to a resin containing a fluorine group, and it is possible to use a fluorine resin such as polytetrafluoroethylene (PTFE). The content concentration of the fluororesin in the third electroless plating solution can be arbitrarily selected according to the use.

The surfactant prevents precipitation of the compound to be complexed and functions as a dispersant of the fluororesin. Thus, it is preferable to use at least one of the group which consists of a cationic surfactant and a nonionic surfactant as surfactant. The cationic surfactants include fourth ammonia salts, second ammonias, third amines, and indazolines, and nonionic surfactants include polyoxyethylene, polyethylene, carboxylic, and sulfonic acids. Nonionic surfactants can be used, but the present invention is not limited thereto. Moreover, it is also preferable to use the fluorine surfactant which has a bond of a carbon element or a fluorine atom in a molecule | numerator. Optionally, the third electroless plating solution preferably contains a dispersing aid in order to further improve dispersion penetration of the fluororesin in the second plating layer. Such dispersion aids include, but are not limited to, cerium oxide and silicon carbide.

The electroless plating process of this invention can be performed similarly to the electroless plating method normally performed in the plating industry.

The plated object to be plated by the electroless plating method according to the present invention will be described. The film thickness of the first plated layer of the plated object is selected to be suitable for adhesion with the plated object. In addition, each film thickness of a 2nd plating layer and a 3rd plating layer selects an appropriate thickness in consideration of hardness, cost, etc. of a plating film.

The plated workpiece obtained by the above method has excellent adhesion to the workpiece 20 due to the presence of the first plating layer 21, which is an electropolishing treatment and a protective layer, as shown in FIG. Reference numeral 23 is a second plating layer, and reference numeral 25 is a third plating layer.

Hereinafter, although the electroless-plating method and the to-be-processed object which concern on this invention are shown, this Example is an illustration of embodiment of this invention and is not limited to this at all.

Example 1

Stainless plates and other metal plates are immersed in the prepared electrolytic polishing solution. At this time, the stainless plate is applied a positive voltage to act as a positive electrode and the other metal plate is applied a negative voltage to act as a cathode.

After the lapse of a predetermined time, the stainless plate was extracted from the electrolytic polishing electrolytic solution, washed, and left to dry under an ambient temperature environment. After electropolishing, the surface of the stainless steel plate was intensively polished so that the height between the recess and the protrusion was reduced than before electropolishing.

Subsequently, the stainless steel plate was immersed in the electroless plating solution maintained at 86 ° C. for a predetermined time, and then the stainless steel plate was extracted from the electroless plating solution, washed with water, and left to stand in a room temperature environment and dried. The electroless plating solution contained nickel lactate as the metal salt, sodium hypochlorite as the reducing agent, and polytetrafluoroethylene (PTEF) as the fluorine resin. On the stainless steel plate, a plating layer having a predetermined thickness was formed. The surface of this plating layer was flattened by PTFE.

The plated stainless steel plate deposited on the surface was placed in a furnace kept at 300 ° C. or higher, left to stand for 60 minutes, and baked to obtain a to-be-processed object, which was a final product in which a thin film by electroless plating was formed on the surface. .

The final plated workpiece had very high flatness and plating adhesion density compared to that of the prior art.

Example 2

Stainless plates and other metal plates are immersed in the prepared electrolytic polishing solution. At this time, the stainless plate is applied a positive voltage to act as a positive electrode and the other metal plate is applied a negative voltage to act as a cathode.

After the lapse of a predetermined time, the stainless plate was extracted from the electrolytic polishing electrolytic solution, washed, and left to dry in an ambient temperature environment. After electropolishing, the surface of the stainless plate was intensively polished so that the height between the recess and the protrusion was reduced than before electropolishing. The electropolished stainless steel plate was immersed for 1 to 10 minutes at room temperature in an electroplating solution of nickel chloride 220-250 g / L, hydrochloric acid (specific gravity 1.18), 110 to 140 ml / L, and current density of 5 to 10 A / dm2. This stainless steel plate was extracted from the electroplating solution, washed with water, and left to dry in an ambient temperature environment. On the surface of the stainless steel plate, a first nickel plating layer as a protective layer of a predetermined thickness was formed.

Subsequently, after the stainless steel plate having the first plating layer was further immersed in the electroless plating solution maintained at 86 ° C. for a predetermined time, the stainless steel plate was extracted from the electroless plating solution, washed with water, and left to stand in a room temperature environment and dried. . The electroless plating solution contained nickel lactate as the metal salt, sodium hypochlorite as the reducing agent, and polytetrafluoroethylene (PTEF) as the fluorine resin. A second nickel plated layer having a predetermined thickness was formed on the first nickel plated layer of the stainless plate. The surface of this second nickel plated layer was flattened by PTFE.

The stainless steel plate on which the first to second nickel plated layers are deposited on the surface is placed in a furnace in which the temperature is maintained at 300 ° C. or higher, and left for 60 minutes for baking, and the final product on which the thin film by electroless plating is formed on the surface is plated. The final target workpiece had a very high flatness and plating adhesion density compared to that of the prior art.

Example 3

Stainless plates and other metal plates are immersed in the prepared electrolytic polishing solution. At this time, the stainless plate is applied a positive voltage to act as a positive electrode and the other metal plate is applied a negative voltage to act as a cathode.

After the lapse of a predetermined time, the stainless plate was extracted from the electrolytic polishing electrolytic solution, washed, and left to dry under an ambient temperature environment. After electropolishing, the surface of the stainless steel plate was intensively polished so that the height between the recess and the protrusion was reduced than before electropolishing.

The electropolished stainless steel plate was immersed for 1 to 10 minutes at room temperature in an electroplating solution of nickel chloride 220-250 g / L, hydrochloric acid (specific gravity 1.18), 110 to 140 ml / L, and current density of 5 to 10 A / dm2. This stainless steel plate was extracted from the electroplating solution, washed with water, and left to dry in an ambient temperature environment. On the surface of a stainless steel plate, the 1st nickel plating layer which is a protective layer of predetermined thickness was formed.

Next, the stainless plate was immersed in the first electroless plating solution containing nickel lactic acid as a metal salt, sodium charine as a reducing agent, nitric acid, succinic acid or lactic acid as a complexing agent, a regulator, a pH regulator, and the like for a first predetermined time. The stainless steel plate was extracted from the first electroless plating solution, washed with water, and left to dry in an ambient temperature environment. A second nickel plating layer having a predetermined thickness was formed on the surface of the stainless steel plate. Subsequently, the stainless steel plate having the second nickel plating layer was further immersed in the second electroless plating liquid held at 86 ° C. for a predetermined time, and then the stainless steel plate was formed. The plate was extracted from the second electroless plating solution, washed with water and left to dry in an ambient temperature environment. The second electroless plating solution contained nickel lactate as the metal salt, sodium hypochlorite as the reducing agent, and polytetrafluoroethylene (PTEF) as the fluorine resin. On the second plating layer of the stainless steel plate, a third plating layer having a predetermined thickness was formed. The surface of this third plating layer was flattened by PTFE.

The first to third plated layers were placed in a furnace in which the stainless steel plate deposited on the surface was held at 300 ° C. or higher, left to stand for 60 minutes, and baked, and the plated product, which was the final product on which the thin film by electroless plating was formed on the surface. The treated product was obtained.

The final plated workpiece had very high flatness and plating adhesion density compared to that of the prior art.

According to the electroless plating method of the present invention, an electroless plate having a high flatness and a very high adhesion to the plated material can be suppressed by inhibiting the occurrence of pinholes between the plated plated material made of a precious metal, stainless steel or molybdenum steel and the plated layer. The plating film can be formed.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

1 is a cross-sectional view showing a surface state of a plated object according to the prior art.

2 is a schematic diagram illustrating an electropolishing process in the electroless plating process according to the embodiment of the present invention.

3 is a cross-sectional view showing a surface state of a plated object manufactured according to an embodiment of the present invention.

4 is a cross-sectional view illustrating a state in which an electroless plating layer is coated on a plated object according to an embodiment of the present invention.

Claims (14)

delete delete delete delete delete delete Electropolishing the surface of the plated object by applying a positive voltage to immerse the plated object in the electrolyte to function as an anode; Forming a first plated layer functioning as a protective layer by electroplating the electroplated object to be electroplated; Forming a second plating layer containing a fluorine resin by electroless plating the plated object including the first plating layer in a first electroless plating solution containing a metal salt; And the first plating layer is a nickel layer when the plated object is stainless steel, and the second plating layer is a nickel layer containing fluorine resin. Electropolishing the surface of the plated object by applying a positive voltage to immerse the plated object in the electrolyte to function as an anode; Forming a first plated layer functioning as a protective layer by electroplating the electroplated object to be electroplated; Forming a second plating layer containing a fluorine resin by electroless plating the plated object including the first plating layer in a first electroless plating solution containing a metal salt; The first plating layer is a zinc layer when the plated object is an aluminum alloy, and the second plating layer is a nickel layer containing a fluorine resin. delete delete delete delete delete delete