NICKEL PLATING SOLUTION AND METHOD FOR FORMING NICKEL PLATING LAYER USING THE SAME

Abstract

Disclosed herein are a nickel plating solution and a method for forming a nickel layer on an external electrode of a chip component by using the nickel plating solution, the nickel plating solution including: a nickel ion; a chloride ion; and a pH buffer, wherein the pH buffer is used by mixing an inorganic acid, and an organic acid and a salt thereof, so that the damage to a body of the chip component can be reduced by containing organic acid and a salt thereof in the nickel plating solution for forming the nickel plating layer on the external electrode of the chip component having a body formed of a material including ferrite or manganese oxide.

Description

CROSS REFERENCE(S) TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. Section 119 of Korean Patent Application Serial No. 10-2012-0100435, entitled “Nickel Plating Solution and Method for Forming Nickel Plating Layer Using The Same” filed on Sep. 11, 2012, which is hereby incorporated by reference in its entirety into this application.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a nickel plating solution and a method for forming a nickel plating layer using the same.

2. Description of the Related Art

In general, as an external electrode of a chip component among electronic components, a nickel or tin plating layer is formed on an underlayer metal material through electroplating. The tin plating layer is used as a soldering layer at the time of mounting a printed circuit board, and the nickel plating layer serves as a barrier layer between the external electrode and a solder.

For the nickel plating layer, a nickel electroplating solution is used and a sulfamate bath or a watt bath is mainly used. However, in the case where a conventional nickel plating solution is used, a body of the electronic component may be damaged depending on the material of the electronic component.

A general nickel plating solution for the chip component is composed of the following chemicals. In the case of the sulfamate bath, nickel sulfamate is used as a nickel metal source, and in the case of the watt bath, nickel sulfate is used as a nickel metal source.

Commonly, in order to help anodic dissolution, nickel chloride is used as a chloride ion source, and boric acid is mainly used as a buffer and a pH adjuster. In addition, the plating solution is made up and used at a region of pH of 4.5 or lower.

However, in the case where the body is formed of materials containing ferrite or manganese oxide, the formation of the plating layer of a general nickel electroplating solution may cause the body to be damaged. For example, since the body is worn, electric property may be deteriorated; the plating solution may penetrate into a neighboring portion of the external electrode; or the external electrode may be lifted or peeled due to the wearing. In addition, the decrease in adhesive strength between the external electrode and the body may cause products to be defective.

In the related art, in the case where the body is damaged by the plating solution, a surface of the chip is coated to minimize the contact with the plating solution, and then plating is performed thereon. However, in the case where coating is performed, costs and time are required due to the use of an additional process before plating, and in the case where the quality of the coating film is bad, the risk of damage to products is high.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a nickel plating solution capable of minimizing damage without an additional process when a body of a chip component is formed of a material containing ferrite or manganese oxide.

Another object of the present invention is to provide a method for forming a nickel plating layer on an external electrode of the chip component by using the nickel electroplating solution.

According to one exemplary embodiment of the present invention, there is provided a nickel plating solution, including: a nickel ion; a chloride ion; and a pH buffer, wherein the pH buffer is used by mixing an inorganic acid, and an organic acid and a salt thereof.

The pH buffer may be contained in a concentration of 30˜100 g/L and the organic acid and the salt thereof may be contained in a concentration of 20˜50 g/L in the pH buffer.

The organic acid and the salt thereof may be at least one selected from the group consisting of succinic acid, gluconic acid, lactic acid, and a salt thereof.

The nickel ion may be contained in a concentration of 50˜100 g/L and the chloride ion may be contained in a concentration of 10˜50 g/L.

The nickel plating solution may have a pH value of 4.5˜6.0.

According to another exemplary embodiment of the present invention, there is provided a method for forming a nickel plating layer in which the nickel plating layer is formed on an external electrode of a chip component, wherein the nickel plating layer is formed by using a nickel electroplating solution containing a nickel ion, a chloride ion, and a pH buffer where an inorganic acid, and an organic acid and a salt thereof are mixed.

Here, a body of the chip component may be formed of a semiconductor ceramic material including ferrite; or Mn, Ni, Al or Co.

The chip component may be an inductor or a thermistor.

The forming of the nickel plating layer may be performed under a DC current application condition.

Here, in the forming of the nickel plating layer, a plating temperature of the plating solution may be 45˜55° C.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an image of a lateral surface of a control group (a chip component before plating);

FIG. 2 is an image of a lateral surface of a chip component after a nickel plating layer is formed on an external electrode by using a plating solution of Comparative Example 1;

FIG. 3 is an image of a lateral surface of a chip component after a nickel plating layer is formed on an external electrode by using a plating solution of Example 1;

FIG. 4 is a scanning electron microscope (SEM) image confirming corrosion or non-corrosion of a body when a nickel plating layer is formed on an external electrode of a chip component by using a nickel plating solution prepared according to Comparative Example 1; and

FIG. 5 is a scanning electron microscope (SEM) image confirming corrosion or non-corrosion of a body when a nickel plating layer is formed on an external electrode of a chip component including a material containing manganese oxide in the body by using a nickel plating solution prepared according to Example 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention will be described in detail. Terms used in the present specification are for explaining the embodiments rather than limiting the present invention. Unless explicitly described to the contrary, a singular form includes a plural form in the present specification. Also, used herein, the word “comprise” and/or “comprising” will be understood to imply the inclusion of stated constituents, steps, operations and/or elements but not the exclusion of any other constituents, steps, operations and/or elements.

The present invention is directed to a neutral type nickel plating solution for electroplating for forming a nickel plating layer formed on an external electrode of a chip component.

The nickel electroplating solution according to the present invention includes a nickel ion, a chloride ion, and a pH buffer, and the pH buffer is characterized by mixing an inorganic acid, and an organic acid and a salt thereof.

In the present invention, the pH buffer is used by mixing an inorganic acid, and an organic acid and a salt thereof. For this reason, the problem of the related art that the body is damaged due to the use of only an inorganic acid can be solved.

The reason why the body is corroded by the nickel electroplating solution of a general sulfamate bath or watt bath is a low pH value of the plating solution. In the case where the pH of the nickel electroplating solution is raised to be 4.5 or higher, the body may become less corroded. However, with respect to a general nickel electroplating solution, when the value of pH is raised by using a pH adjuster, for example, caustic soda, ammonia, or the like, the plating solution cannot be used due to precipitation of hydroxides.

In order to prevent this phenomenon, it is necessary to use a pH buffer. The present invention solves this problem by using an organic acid and a salt thereof as well as the existing inorganic acid, as a pH buffer. In particular, in the case of using the organic acid and the salt thereof, the nickel ion is made into a complex salt so that the nickel ion is stably present in the plating solution, thereby preventing formation of hydroxide precipitation.

Preferably, the pH buffer is contained in a concentration of 30˜100 g/L and the organic acid and the salt thereof are contained in a concentration of 20˜50 g/L within the plating solution.

If the concentration of the pH buffer is below 30 g/L, the pH variation of the plating solution before and after plating may be increased, unfavorably. If above 100 g/L, chemicals may not be easily dissolved in the plating solution, unfavorably.

In addition, if the concentration of the organic acid and the salt thereof in the pH buffer is below 20 g/L, the hydroxides may be easily generated at the time of an increase in pH value of the plating solution. If above 50 g/L, there may be problems with dissolution of chemicals and the plating efficiency may be reduced, unfavorably.

Examples of the organic acid and the salt thereof may include succinic acid, gluconic acid, lactic acid, sodium succinate, sodium gluconate, and the like, but are not limited thereto.

In addition, the pH buffer of the present invention includes an existing inorganic acid such as boric acid, and the inorganic acid may be contained in a concentration of 10˜50 g/L.

Preferably, the nickel ion is contained in the nickel electroplating solution of the present invention in a concentration of 50˜100 g/L. Examples of a nickel ion source may include nickel sulfamate, nickel sulfate, and the like, but are not limited thereto.

In addition, the chloride ion is preferably contained in the nickel electroplating solution of the present invention in a concentration of 10˜50 g/L. A chloride ion source may be nickel chloride, but is not limited thereto.

In addition, the pH of the nickel electroplating according to the present invention is preferably maintained at a pH range of 4.5˜6.0. If the pH of the plating solution is below 4.5, the body may be corroded, unfavorably. If above 6.0, the stability of the plating solution may be deteriorated and thus it is difficult to use the plating solution for a long time, unfavorably.

The plating temperature of the nickel electroplating of the present invention is preferably 45˜55° C., and as necessary, the plating solution may be stirred.

In addition, the present invention is also characterized in a method of forming a nickel plating layer on an external electrode of the chip component. Here, the nickel plating layer may be formed by using a nickel electroplating solution containing a pH buffer where a nickel ion, a chloride ion, inorganic acid, and organic acid and a salt thereof are mixed.

The nickel electroplating solution has been described in detail as above.

The body of the chip component is preferably formed of a semiconductor ceramic material including ferrite; or Mn, Ni, Al or Co. A representative example of the ferrite is NiZnCu ferrite, but is not limited thereto.

In view of forming the nickel plating layer on the external electrode of the chip component by using the nickel electroplating of the present invention, an inductor or a thermistor may be preferably used as the chip component.

In addition, when the nickel plating layer is formed on the external electrode of the chip component by using the nickel electroplating solution, electroplating is preferably performed under the DC current application condition. The cathode current density is preferably in the range of 2˜10 A/dm².

Hereinafter, examples of the present invention will be described in detail. The following examples are only for illustrating the present invention, and the scope of the present invention should not be construed as being limited by these examples. Further, specific compounds are used in the following examples, but it is obvious to those skilled in the art that equivalents thereof can exhibit the same or similar degrees of effects.

COMPARATIVE EXAMPLE 1

A plating solution containing a nickel ion of 80 g/L, nickel chloride of 15 g/L, and boric acid of 15 g/L was prepared, and the pH of the plating solution was adjusted by using sulfuric acid and nickel hydroxide. Nickel and tin electroplating was performed on an external electrode of a chip component having a body containing manganese oxide, at a temperature of 50° C. by using the plating solution.

EXAMPLE 1

A nickel plating solution containing a nickel ion of 80 g/L, nickel chloride of 15 g/L, boric acid of 15 g/L, and succinate acid of 40 g/L was prepared, and the pH of the nickel plating solution was adjusted to be 5.5 by using sulfuric acid and nickel hydroxide

Nickel and tin electroplating was performed on an external electrode of a chip component, having a body (semiconductor ceramic including Mn, Ni, Al and Co) containing manganese oxide, at a temperature of 50° C. of the nickel plating solution, by using the nickel plating solution.

EXAMPLE 2

Plating was performed on a chip component in the same manner as Example 1, except that sodium gluconate instead of succinate acid was used as the organic acid of the nickel electroplating solution of Example 1.

CONTROL GROUP

With respect to a chip component having a body containing manganese oxide before a plating layer is formed on an external electrode, as a control group, comparison of corrosion or non-corrosion of the body due to formation of a nickel plating layer was conducted between the plating solutions of Comparative Example and Examples.

EXPERIMENTAL EXAMPLE 1

Confirmation on Corrosion of Body

When each of the nickel plating solutions prepared according to Example 1 and Comparative Example 1 was used to form a nickel plating layer on an external electrode of a chip component having a body containing manganese oxide, corrosion or non-corrosion of the body was confirmed by observing a cross section thereof through an optical microscope. The results were shown in FIGS. 1 to 3.

FIG. 1 is an image of a lateral surface of a chip component before a nickel electrode layer is formed on an external electrode 20. Referring to FIG. 1, in the case of Comparative Example 1 where a nickel plating layer was formed on an external electrode 20 by using a nickel plating solution of the related art, a body 10 was corroded as shown in FIG. 2, so that it was observed that the thickness of the body (T2) was significantly decreased as compared with the thickness of the body before plating (T1).

However, in the case of Example 1 where a nickel plating layer was formed on an external electrode 200 by using a nickel plating solution containing organic acid, the body 100 was not corroded as shown in FIG. 3, so that it was confirmed that the thickness of the body (T3) is mostly similar to the thickness of the body before plating (T1).

Even in the case where the nickel plating layer was formed on the external electrode by using the nickel plating solution of Example 2, containing a different kind of organic acid, the body was not corroded like in Example 1.

EXPERIMENTAL EXAMPLE 2

Confirmation on Corrosion or Non-corrosion Structure of Body

When each of the nickel plating solutions prepared according to Comparative Example 1 and Example 1 was used to form a nickel plating layer on an external electrode of a chip component having a body containing manganese oxide, corrosion or non-corrosion of the body was confirmed by using a scanning electron microscope. The results were shown in FIGS. 4 to 5.

As can be seen from FIG. 4 showing a structure of the body according to Comparative Example 1, excessive corrosion of the body occurred. However, as can be seen from FIG. 5 showing a structure of the body according to Example 1 of the present invention, corrosion of the body did not occur.

These results resulted from the fact that the organic acid and the salt thereof contained in the nickel plating solution of the present invention form a complex salt together with the nickel ion so that the nickel ion can be stably present in the plating solution even at the time of increasing pH of 4.5 or higher, and thus effectively prevent formation of hydroxide precipitation.

As set forth above, according to the present invention, the nickel electroplating solution for forming a nickel plating layer on the external electrode of the chip component having a body formed of a material including ferrite or manganese oxide contains organic acid and a salt thereof, so that damage to the body can be reduced.

While the present invention has been shown and described in connection with the embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A nickel plating solution, comprising:

a nickel ion;

a chloride ion; and

a pH buffer,

wherein the pH buffer is used by mixing an inorganic acid, and an organic acid and a salt thereof.

2. The nickel plating solution according to claim 1, wherein the pH buffer is contained in a concentration of 30˜100 g/L and the organic acid and the salt thereof are contained in a concentration of 20˜50 g/L in the pH buffer.

3. The nickel plating solution according to claim 1, wherein the organic acid and the salt thereof are at least one selected from the group consisting of succinic acid, gluconic acid, lactic acid, and a salt thereof.

4. The nickel plating solution according to claim 1, wherein the nickel ion is contained in a concentration of 50˜100 g/L and the chloride ion is contained in a concentration of 10˜50 g/L.

5. The nickel plating solution according to claim 1, wherein it has a pH value of 4.5˜6.0.

6. A method for forming a nickel plating layer in which the nickel plating layer is formed on an external electrode of a chip component, wherein the nickel plating layer is formed by using a nickel electroplating solution containing a nickel ion, a chloride ion, and a pH buffer where an inorganic acid, and an organic acid and a salt thereof are mixed.

7. The method according to claim 6, wherein a body of the chip component is formed of a semiconductor ceramic material including ferrite; or Mn, Ni, Al or Co.

8. The method according to claim 6, wherein the chip component is an inductor or a thermistor.

9. The method according to claim 6, wherein the forming of the nickel plating layer is performed under a DC current application condition.

10. The method according to claim 6, wherein in the forming of the nickel plating layer, a plating temperature of the plating solution is 45˜55° C.