KR20140092597A - Electroless cobalt plating solution, method of electroless plating using the same, and cobalt plating layer using the same - Google Patents

Abstract

The present invention provides an electroless cobalt plating solution which provides excellent thermal properties, enhanced flexibility, and enhanced welding properties. According to an embodiment of the present invention, the electroless cobalt plating solution includes a cobalt metal salt which provides cobalt ions for plating; a reducing agent which reduces cobalt ions for plating; a complexing agent which forms a complex with the cobalt ions for plating and includes at least one of carboxylic acid and alpha-hydroxy acid; and a stabilizing agent which stabilizes the cobalt ions for plating and includes ammonium sulfate.

Description

[0001] The present invention relates to an electroless cobalt plating solution, an electroless plating method using the electroless cobalt plating solution, and a cobalt plating layer using the electroless cobalt plating solution,

Technical aspects of the present invention relate to electroless plating, and more particularly, to an electroless cobalt plating solution, an electroless plating method, and a cobalt plating layer.

Electroless plating is a method of forming a metal plating layer on a plating object from a metal salt by a redox reaction of metal without using external energy from a solution in which a metal salt is dissolved, After being subjected to the pretreatment process, they are also used in various industrial fields because they can be plated on insulating objects.

Plated surfaces using electroless plating are becoming increasingly important in the parts and materials industry, such as in mounting surfaces such as ultra-small devices with high density in various packaging fields and in bonding interfaces. In recent years, there has been a demand for an increase in the internal circuit density and a narrow pitch in accordance with the weight reduction, miniaturization and high performance of electronic products. Therefore, there is a need for an electroless plating method in which the variation in the thickness of the plating layer is small, Is increasing.

Particularly, since the electroless nickel plating method can provide a plating film excellent in corrosion resistance, abrasion resistance and the like, it is mainly used as a plating method for final surface treatment of an electronic material part. In recent years, the ENIG (electroless nickel immersion gold) method has been widely used as a final surface treatment method for printed wiring boards and is used for defective treatment of solder joints.

In the case of electroless nickel plating, the potential of nickel is -0.23 V, which facilitates precipitation of metal when a strong reducing agent is used. Further, copper (Cu), which is mainly used for electric wiring, has relatively poor autocatalytic properties and is difficult to form a plating layer on its surface even if it is immersed in a plating solution. Therefore, it is necessary to activate the copper surface to impart catalytic properties, and then proceed with electroless plating. In this case, a palladium solution is mainly used as a catalyst.

However, since the catalyst containing palladium easily forms an ionic state and easily adheres to the surface of the metal, it is easily attached to the remaining copper residues not removed in the etching process, and the space between copper wirings ) May be formed on the plated layer to form bridging.

Further, the general electroless nickel plating layer has excellent properties such as high hardness, abrasion resistance and corrosion resistance, but is not good in ductility and is easily broken due to warping or folding, and the surface is crystallized at a high temperature, .

The technical problem to be solved by the technical idea of the present invention is to provide an electroless cobalt plating liquid which is excellent in thermal characteristics and mechanical properties and in particular provides improved ductility and solderability.

The technical object of the present invention is to provide an electroless plating method using an electroless cobalt plating liquid which is excellent in thermal characteristics and mechanical properties and in particular provides improved ductility and solderability.

The technical object of the present invention is to provide a cobalt plated layer formed using the cobalt plating solution

However, these problems are illustrative, and the technical idea of the present invention is not limited thereto.

According to an aspect of the present invention, there is provided an electroless cobalt plating solution comprising: a cobalt metal salt for providing cobalt ions for plating; A reducing agent for reducing the cobalt ions for plating; A complexing agent which forms a complex with the cobalt ions for plating and contains at least one of a carboxylic acid and an aliphatic acid; And a main stabilizer stabilizing the cobalt ions for plating and containing ammonium sulfate.

In some embodiments of the present invention, the cobalt metal salt may comprise at least one of cobalt sulphate, cobalt sulfamate, cobalt acetate, and cobalt chloride.

In some embodiments of the present invention, the cobalt metal salt may be included in the range of 2 g to 7 g with respect to 1 liter of the cobalt plating solution.

In some embodiments of the present invention, the reducing agent may include at least one of hypophosphite, boron hydride, dimethylamine borane, and hydrazine.

In some embodiments of the present invention, the reducing agent may be included in the range of 20 g to 100 g per liter of the cobalt plating solution.

In some embodiments of the present invention, the complexing agent may include citric acid, glycine, lactic acid, or both.

In some embodiments of the present invention, the complexing agent may be included in the range of 10 g to 70 g with respect to 1 liter of the cobalt plating solution.

In some embodiments of the present invention, the complexing agent is a carboxylic acid and a derivative thereof, and may be included in the range of 10 g to 30 g per liter of the cobalt plating solution.

In some embodiments of the present invention, the complexing agent is an alpha hydroxy acid and a derivative thereof, and may be included in the range of 10 g to 50 g per liter of the cobalt plating solution.

In some embodiments of the present invention, the complexing agent may be a single component or a mixed component.

In some embodiments of the present invention, the main stabilizer may be included in the range of 10 g to 30 g per 1 liter of the cobalt plating solution.

In some embodiments of the present invention, the metal stabilizer may further include a metal stabilizer which inhibits the reduction reaction of the cobalt ions for plating and is contained in the range of 0.1 ppm to 5.0 ppm relative to 1 liter of the cobalt plating solution.

In some embodiments of the present invention, the metal stabilizer is selected from the group consisting of lead (Pb), thallium (Tl), tellurium (Te), selenium (Se), bismuth (Bi), tin (Sn) , And molybdenum (Mo).

In some embodiments of the present invention, the noble decomposition of the cobalt plating solution is suppressed, the precipitate formed by aging of the cobalt plating solution is prevented from reacting with the reducing agent, thereby stabilizing the cobalt plating solution, Based stabilizer contained in the range of 0.1 ppm to 5.0 ppm based on 1 liter.

In some embodiments of the present invention, the sulfide-based stabilizer comprises at least one of thiourea and derivatives thereof, sulfite, pyrosulfite, and thiocyanate .

Surfactants which, in some embodiments of the present invention, increase the interfacial characteristics and wettability of the plating layer and include alkyl sulfate-based surfactants and are included in the range of 1.0 ppm to 20 ppm based on 1 liter of the cobalt plating solution; . ≪ / RTI >

In some embodiments of the present invention, the pH adjusting agent may be at least one selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, ammonia water, sodium hydroxide, potassium hydroxide, and the pH of the cobalt plating solution is controlled within the range of 7.5 to 9.5. .

According to an aspect of the present invention, there is provided an electroless plating method using an electroless cobalt plating solution, comprising the steps of: preparing the electroless cobalt plating solution; And immersing the plating object in the electroless cobalt plating liquid to form an electroless plating layer on the plating object.

In some embodiments of the present invention, in the step of forming the electroless plating layer on the plating object, the electroless cobalt plating liquid may have a temperature in the range of 60 캜 to 95 캜.

According to an aspect of the present invention, a cobalt plated layer is plated on a surface of a plated object by the electroless cobalt plating solution.

The electroless cobalt plating solution according to the technical idea of the present invention includes cobalt instead of nickel as the metal salt to be plated on the plating object.

The electroless cobalt plating solution can increase the low ductility, which is a disadvantage of nickel plating, and can prevent the bridging phenomenon, while having high hardness, excellent abrasion resistance, solder resistance and corrosion resistance, which are advantages of silver and electroless nickel plating have.

The electroless cobalt plating solution can be used in a final surface treatment method for forming a bonding layer of a copper wiring and a bump of a hard and a flexible printed circuit board and a semiconductor and a package.

The effects of the present invention described above are exemplarily described, and the scope of the present invention is not limited by these effects.

1 is a schematic view showing a plating apparatus using an electroless cobalt plating solution according to an embodiment of the present invention.
2 is a flowchart illustrating an electroless plating method using an electroless cobalt plating solution according to an embodiment of the present invention.
3 is a scanning electron microscope (SEM) image showing the surface of a plating layer formed on a plating target using a cobalt plating solution of the embodiments of the present invention and a nickel plating solution of a comparative example, respectively.
FIG. 4 is a scanning electron microscope (SEM) image showing the surface of a plating layer formed on a plating target object in an enlarged scale, using the cobalt plating solution of the embodiments of the present invention and the nickel plating solution of the comparative example, respectively.
5 is a scanning electron microscope (SEM) image showing an enlarged cross section of a plating layer formed on a plating target using a cobalt plating solution of the embodiments of the present invention and a nickel plating solution of a comparative example, respectively.
FIG. 6 is a graph showing the results of the shrinkage test of the plating object in which the plating layer is formed by using the cobalt plating solution of the embodiments of the present invention and the nickel plating solution of the comparative example, respectively.
FIG. 7 is a scanning electron microscope photograph showing the fracture shape of the plating layers after the proofing test in FIG. 6; FIG.
FIG. 8 is a scanning electron microscope photograph showing a fracture section of plating layers after the shrinkage test of FIG. 6; FIG.
FIG. 9 is a graph showing the results of the bonding strength test of the plating object in which the plating layer is formed using the cobalt plating solution of the embodiments of the present invention and the nickel plating solution of the comparative example, respectively.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It will be apparent to those skilled in the art that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. The scope of technical thought is not limited to the following examples. Rather, these embodiments are provided so that this disclosure will be more thorough and complete, and will fully convey the scope of the invention to those skilled in the art. As used herein, the term "and / or" includes any and all combinations of one or more of the listed items. The same reference numerals denote the same elements at all times. Further, various elements and regions in the drawings are schematically drawn. Accordingly, the technical spirit of the present invention is not limited by the relative size or spacing depicted in the accompanying drawings.

1 is a schematic view showing a plating apparatus using an electroless cobalt plating solution according to an embodiment of the present invention.

1, the plating apparatus 10 includes an electroless cobalt plating liquid 30 housed in a plating bath 20, immersing the plating target object 40 in an electroless cobalt plating liquid 30, A plating layer 50 is formed. Hereinafter, the electroless cobalt plating solution 30 will be referred to as a cobalt plating solution 30 for the sake of simplicity. Also, the case of using a plating solution composed of a metal other than the cobalt plating solution 30 is also included in the technical idea of the present invention.

The cobalt plating liquid 30 includes a solvent and a cobalt metal salt, a reducing agent, a complexing agent, and a main stabilizer dissolved in the solvent. The cobalt plating solution 30 may further include at least one of a metal stabilizer, a sulfide stabilizer, a surfactant, and a pH adjuster.

The plating object 40 may include a metal or a polymer material. The plating object 40 may include, for example, copper or iron. The plating target 40 may be a hard printed circuit board or a flexible printed circuit board, or may be a semiconductor chip or a semiconductor package having a copper wiring or a bonding layer of bumps formed thereon.

The cobalt plating solution 30 may have a pH ranging from pH 7.5 to pH 9.5 and may be subjected to a plating process at 60 캜 to 95 캜.

Hereinafter, the constituent elements of the cobalt plating solution 30 will be described in detail.

The solvent may constitute most of the cobalt plating solution 30 in which the plating target object 40 is immersed. The solvent may include a substance which dissolves the cobalt metal salt, the reducing agent, the complexing agent, the main stabilizer, the pH adjusting agent, the metal stabilizer, and the sulfide stabilizer. The solvent may be, for example, water. However, this is illustrative and the technical idea of the present invention is not limited thereto.

The cobalt metal salt may be dissolved in the solvent. The cobalt metal salt may provide cobalt ions for plating to the plating target body 40 and the plating layer 50 may be formed on the plating target object 40 by the cobalt ions for plating. The cobalt metal salt may include a metal, for example, cobalt (Co). Accordingly, the cobalt ions for plating may include cobalt (Co) ions, and the cobalt ions may be, for example, bivalent ions or trivalent ions. The cobalt metal salt may include, for example, cobalt salt hydrate, and may include at least one of cobalt sulfate, cobalt sulfamate, cobalt acetate, and cobalt chloride, for example.

The cobalt metal salt may be contained in the range of 2 g to 7 g per 1 liter of the cobalt plating solution (30). For example, when the concentration of the cobalt metal salt is less than 2 g / liter, the plating rate may be lowered. If the concentration of the cobalt metal salt is more than 7 g / liter, the stability of the cobalt plating solution may be lowered and spontaneous decomposition of the cobalt plating solution may occur or the plating rate may be lowered.

The reducing agent may be dissolved in the solvent. The reducing agent may reduce the cobalt ions for plating. The reducing agent can reduce the cobalt ion, for example. The reducing agent may include at least one of, for example, hypophosphite, boron hydride, dimethylamine borane, and hydrazine. The reducing agent may include at least one of sodium hypophosphite, potassium hypophosphite, and ammonium hypophosphite as the hypophosphite.

The reducing agent may be included in the range of 20 g to 100 g per 1 liter of the cobalt plating solution (30). For example, when the concentration of the reducing agent is less than 20 g / liter, the plating rate may be lowered. If the concentration of the reducing agent is more than 100 g / liter, stability of the cobalt plating solution may be lowered, spontaneous decomposition of the cobalt plating solution may occur, and the plating rate may be lowered.

The complexing agent may be dissolved in the solvent. The complexing agent may form a complex with the cobalt ions for plating. For example, the complexing agent may be chemically bonded to the cobalt ion to form a cobalt complex. The stability characteristics of the cobalt plating solution 30 and the characteristics of the plating layer 50 are greatly changed depending on the type and amount of the complexing agent. Therefore, it is very important to select the type and quantity of the complexing agent depending on the intended use and application. The complexing agent controls the plating rate, prevents spontaneous decomposition of the cobalt plating solution 30, and controls the plating reaction so that the reduction reaction of cobalt occurs smoothly on the surface of the plating object 40. The complexing agent can control the total amount of cobalt ions participating in the reduction reaction with the organic acid or a salt thereof and can perform the function of keeping the stability of the cobalt plating solution 30 during the plating operation. Also, the complexing agent reduces the rapid formation of hydrogen ions by the reduction reaction, so that the pH of the cobalt plating solution 30 can be prevented from changing abruptly.

The complexing agent may be at least one selected from the group consisting of a carboxylic acid having a carboxyl group (COOH) and at least one of the derivative thereof and an alpha-hydroxy acid (AHAs) in which a part of the carboxyl group (COOH) is substituted with a hydroxyl group And may include at least any one of them.

The complexing agent may be at least one selected from the group consisting of carboxylic acid and derivatives thereof such as acetic acid, adipic acid, citric acid, formic acid, propionic acid, butyric acid, wherein the acid is selected from the group consisting of capric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, ), Stearic acid, arachidic acid, oxalic acid, malonic acid, tartaric acid, succinic acid, glutaric acid, But are not limited to, pimelic acid, suberic acid, azelaic acid, sebacic acid, ortho-phthalic acid, The compounds of formula (I) are selected from the group consisting of isophthalic acid, terephthalic acid, taleic acid, fumaric acid, glutaconic acid, traumatic acid, and muconic acid. And may include at least any one of them.

The complexing agent may be at least one compound selected from the group consisting of glycine, glycolic acid, lactic acid, citric acid, mandelic acid, ). ≪ / RTI >

The complexing agent may be included in the range of 10 g to 70 g with respect to 1 liter of the cobalt plating solution (30). When the concentration of the complexing agent is less than 10 g / liter, the stability of the cobalt plating solution is lowered, and spontaneous decomposition of the cobalt plating solution may occur. When the concentration of the complexing agent is more than 70 g / liter, the stability of the cobalt plating solution is increased, but the plating rate can be reduced. If the plating rate is decreased, the production time is prolonged and the economical efficiency and the product characteristics may be deteriorated. As the number of plating increases, the decomposed complexing agent exists in the cobalt plating solution to reduce the lifetime of the cobalt plating solution .

When the complexing agent is a carboxylic acid or a derivative thereof, the complexing agent may be included in the range of 10 g to 30 g per 1 liter of the cobalt plating solution (30). When the complexing agent is an alpha hydroxy acid and a derivative thereof, the complexing agent may be included in an amount of 10 g to 50 g per 1 liter of the cobalt plating solution (30).

For example, the complexing agent may be citric acid and may be included in the range of 10 g to 30 g per liter of the cobalt plating solution 30. [ The complexing agent is glycine and may be contained in the range of 10 g to 50 g per 1 liter of the cobalt plating solution (30). The complexing agent is lactic acid and may be contained in the range of 10 g to 30 g per 1 liter of the cobalt plating solution (30).

The complexing agent may be a mixture of various kinds of materials depending on the purpose of use and the characteristics of the plating object. The complexing agent may be a single component or a mixed component. The complexing agent may be used, for example, as a single component in only one kind, or as a mixed component in which two to four kinds of substances are mixed.

The main stabilizer may be dissolved in the solvent. The main stabilizer is added to increase the stability of the cobalt plating solution 30 because the complex stabilizer is difficult to maintain stability of the cobalt plating solution 30 only by the complexing agent. The cobalt ions can be stabilized by the main stabilizer. The main stabilizer may include, for example, ammonium sulfate.

The main stabilizer may be included in the range of 10 g to 30 g per 1 liter of the cobalt plating solution (30). For example, if the concentration of the main stabilizer is less than 10 g / liter, the plating rate may be lowered. When the concentration of the main stabilizer is more than 30 g / liter, the quality of the plating layer is lowered, and a plated layer having a large amount of cracks can be formed.

The metal stabilizer may be added for the following reasons. In electroless plating, the reduction reaction of the cobalt ions for plating, for example, cobalt, should be controlled so that the deposition rate can be predicted and the reaction should be controlled to occur only on the surface of the plating object. If such control is insufficient, the cobalt plating liquid itself may be unstable, so that cobalt may precipitate in the cobalt plating liquid or on the wall of the plating bath by itself, and thus the cobalt plating liquid may lose its original function. The decomposition of this cobalt plating solution can be triggered by colloidal particles or suspended particles present in the cobalt plating solution. These particles have a very large specific surface area and act as a catalyst for the reduction reaction so that cobalt is precipitated and the hydrogen gas is released in a large amount by the reduction reaction to form a fine black precipitate. . Therefore, a stabilizer for suppressing the reduction reaction from occurring other than the surface of the object to be plated is required, and the metal stabilizer can perform this function.

The metal stabilizer may be dissolved in the solvent. The metal stabilizer can suppress the reduction reaction of the cobalt ions for plating. In particular, the metal stabilizer can perform the function of stabilizing the cobalt plating liquid 30 by suppressing the reduction reaction in regions other than the region where the plating layer 50 of the plating target body 40 is desired to be formed. The metal stabilizer may include a metal element. The metal stabilizer may be at least one selected from the group consisting of lead (Pb), thallium (Tl), telenium (Te), selenium (Se), bismuth (Bi), tin (Sn), cadmium (Cd), and molybdenum And may include at least any one of them.

The metal stabilizer may include at least one of a metal element that is the metal itself, a cobalt metal salt that includes the metal element, a metal oxide that includes the metal element, and a metal sulfide that includes the metal element.

The metal stabilizer may be contained in the range of 0.1 ppm to 5.0 ppm with respect to 1 liter of the cobalt plating solution (30). That is, the metal stabilizer may be contained in the range of 0.1 mg to 5.0 mg per 1 liter of the cobalt plating solution (30). When the concentration of the metal stabilizer is less than 0.1 ppm, the stability of the cobalt plating solution 30 may be deteriorated and the gloss of the plating layer may be deteriorated. When the concentration of the metal stabilizer is more than 5.0 ppm, May be deteriorated.

The sulfide stabilizer suppresses natural decomposition of the cobalt plating solution 30 and prevents the precipitate formed by aging of the cobalt plating solution 30 from reacting with the reducing agent to stabilize the cobalt plating solution 30 can do. The sulfide-based stabilizer may include, for example, a sulfide-based compound. The sulfide stabilizer may include at least one of thiourea and derivatives thereof, sulfite, pyrosulfite, and thiocyanate.

The sulfide-based stabilizer may be included in the range of 0.1 ppm to 5 ppm based on 1 liter of the cobalt plating solution (30). That is, the sulfide stabilizer may be contained in the range of 0.1 mg to 5 mg per 1 liter of the cobalt plating solution (30). If the sulfide stabilizer is less than 0.1 ppm, the stability of the cobalt plating solution may be lowered. When the amount of the sulfide stabilizer exceeds 3.0 ppm, the plating rate can be remarkably reduced, the gloss of the plating layer may be lowered, pits may be formed in the plating layer, and coarse and non- It may be formed on the plating layer to deteriorate the characteristics of the plating layer.

The surfactant can improve the wettability in order to improve the interfacial property between the matrix layer of the plating object 40 and the plating layer and to prevent pit formation. The surfactant may include an alkylsulfate-based surfactant. The surfactant may be contained in the range of 1 ppm to 20 ppm based on 1 liter of the cobalt plating solution (30).

The pH adjusting agent may be dissolved in the solvent. The plating layer 50 formed on the plating target object 40 is affected by the plating speed and the thickness of the plating layer due to the pH of the cobalt plating liquid 30. Therefore, the material of the plating layer 50, which can maintain and adjust the pH of the cobalt plating liquid 30 Is preferably added. Therefore, the pH adjuster may be added to the cobalt plating solution 30 as a substance that performs such a function. The pH adjusting agent may adjust the pH of the cobalt plating solution 30. The pH adjusting agent may include an acidic substance such as sulfuric acid, hydrochloric acid, nitric acid, or the like, or a basic substance such as ammonia water, sodium hydroxide, and potassium hydroxide.

The amount of the pH adjusting agent added to the cobalt plating solution may be adjusted so as to maintain the cobalt plating solution 30 in the range of pH 7.5 to pH 9.5. The cobalt plating liquid 30 has a slow plating rate in an acidic atmosphere, but the plating rate is accelerated in a basic atmosphere. When the pH of the cobalt plating solution 30 is less than pH 7.5, the plating rate is significantly decreased. When the pH of the cobalt plating solution 30 is more than 9.5, the plating rate is decreased and the plated film is densely formed, .

During the plating process, the cobalt plating solution 30 may have a temperature ranging from about 60 캜 to about 95 캜. When the temperature of the cobalt plating solution 30 is less than 60 ° C, the plating rate is very slow. When the temperature of the cobalt plating solution 30 is more than 95 ° C, the stability of the plating solution is decreased and the coated film can be formed coarser.

2 is a flowchart showing an electroless plating method (S1) using an electroless cobalt plating solution according to an embodiment of the present invention.

Referring to FIG. 2, the electroless plating method (S1) includes a step (S10) of preparing an electroless cobalt plating liquid as described above, and a step of immersing a plating object in the electroless cobalt plating liquid to form an electroless plating layer (S20).

Characterization of cobalt plating solution

In order to examine the characteristics of the electroless cobalt plating solution according to the technical idea of the present invention, a plating experiment was conducted. The electroless cobalt plating solution was cobalt sulphate or cobalt sulphate.

In Example 1, water was used as a solvent, and about 20 g of cobalt sulfate as a cobalt metal salt was added to 1 liter of cobalt plating solution. Accordingly, the cobalt metal is contained in an amount of 5 g per 1 liter of the cobalt plating solution. As the reducing agent, 25 g of sodium hypophosphite was added to 1 liter of the cobalt plating solution. The complexing agent was added with 20 g of citric acid to 1 liter of the cobalt plating solution. Further, 12 g of ammonium sulfate as a main stabilizer for the stability of the plating rate of the cobalt plating solution and the stability of the plating solution was added to 1 liter of the above cobalt plating solution. In addition, several ppm of the above-described metal stabilizer and alkyl sulfate-based surfactant were added.

In Example 2, deionized water was used as a solvent, and about 30 ml of cobalt sodium hypophosphite as a cobalt metal salt was added to 1 liter of cobalt plating solution. Accordingly, the cobalt metal is contained in an amount of 5 g per 1 liter of the cobalt plating solution. Sodium hypophosphite as a reducing agent was added in an amount of 50 g per 1 liter of the cobalt plating solution. The complexing agent was added with 30 g of glycine to 1 liter of the cobalt plating solution. Further, 12 g of ammonium sulfate as a main stabilizer for the stability of the plating rate of the cobalt plating solution and the stability of the plating solution was added to 1 liter of the above cobalt plating solution. In addition, several ppm of the above-described metal stabilizer and alkyl sulfate-based surfactant were added.

As a comparative example, a commercially available electroless nickel plating solution was used. The nickel plating solution used as a comparative example is the product number ECO NP 309 manufactured by Ecostar Co., and is commercially available.

The plating object to be plated in the cobalt plating liquids according to the embodiments of the present invention and the nickel plating liquid of the comparative example was prepared through the following process. The flexible printed circuit board (PCB) substrate was pickled with 10% sulfuric acid solution and washed with deionized water. In order to improve the adhesion of the plating layer, an object to be plated was prepared by performing an etching treatment and a washing treatment for 2 minutes at a temperature range of 20 캜 to 30 캜. The surface was then activated with a palladium catalyst for about 1 minute. Thereafter, the plating object was immersed in the cobalt plating liquids and the nickel plating liquid, respectively, and electroless plating was performed. The plating layer was formed to have a thickness of about 5 mu m on the copper wiring of the printed circuit board as the plating target.

For surface observation, cross-section observation, and bonding strength test, gold (Au) plating was performed on the plating layer to a thickness of 100 nm. Gold plating was performed for about 10 minutes.

MIT type test coupons were used for the theft test, and specimens each having an electroless plating layer of about 5 탆 thickness were prepared from the cobalt plating solutions of the examples and the nickel plating solution of the comparative examples. The thawing test was carried out by applying a load of 500 g at an angle of 135 degrees per minute (175 cpm) using an MIT type Folding Endurance Tester.

For the bonding strength test, a chip was soldered on a plating layer which was plated with gold, and then subjected to a shear test. In the test, the load was 5 kg and the speed was 500 μm / sec.

3 is a scanning electron microscope (SEM) image showing the surface of a plating layer formed on a plating target using a cobalt plating solution of the embodiments of the present invention and a nickel plating solution of a comparative example, respectively.

Referring to Fig. 3, wiring lines in which a 5 탆 thick electroless plating layer and a gold plating layer are formed on a copper wiring line of a printed circuit board are shown. In Examples 1 and 2, a plating layer was formed only on the wiring line.

On the other hand, in the comparative example including nickel, not only the plating layer was formed on the wiring line but also the plating layer was formed in the space between the wiring lines.

Therefore, the cobalt plating solutions of Examples 1 and 2 can form a more precise plating layer than the nickel plating solution of the comparative example.

FIG. 4 is a scanning electron microscope (SEM) image showing the surface of a plating layer formed on a plating target object in an enlarged scale, using the cobalt plating solution of the embodiments of the present invention and the nickel plating solution of the comparative example, respectively.

Referring to Fig. 4, in Examples 1 and 2, a plating layer formed by gold substitution plating is shown after cobalt plating. Example 1 using cobalt sulfate as a metal source showed a larger size of crystal grains than Example 2 using cobalt sodium hypophosphite.

On the other hand, in the comparative example including nickel, such crystal grains were not formed.

5 is a scanning electron microscope (SEM) image showing an enlarged cross section of a plating layer formed on a plating target using a cobalt plating solution of the embodiments of the present invention and a nickel plating solution of a comparative example, respectively.

Referring to Figure 5, the plated layer appears light gray. In Examples 1 and 2, the shape of the plating layer was not formed outside the wiring line.

On the other hand, in the comparative example including nickel, the plating layer appeared to spread outward from the wiring line. This is consistent with the results of FIG. As a result, the plating layer formed by the cobalt plating liquid can prevent bridging phenomenon which is plated in the space between the wiring lines. This is attributed to the lower catalytic activity and higher surface tension under given cobalt conditions than nickel.

Therefore, the cobalt plating solutions of Examples 1 and 2 can form a more precise plating layer than the nickel plating solution of the comparative example.

In Example 1 using cobalt sulfate, the plating layer of the wiring line was found to have a thickness in the range of 3.28 mu m to 3.41 mu m. In Example 2 using cobalt sodium hypophosphite, the plated layer of the wiring line was found to have a thickness in the range of 4.11 탆 to 4.50 탆. Therefore, since the variation in the thickness of the plating was small in Example 1 and Example 2, a plating layer having a uniform thickness could be realized.

Table 1 is a table showing the results of the shrinkage test of the plating object in which the plating layer is formed using the cobalt plating solution of the embodiments of the present invention and the nickel plating solution of the comparative example, respectively. FIG. 6 is a graph showing the results of the shrinkage test of the plating object in which the plating layer is formed by using the cobalt plating solution of the embodiments of the present invention and the nickel plating solution of the comparative example, respectively.

division Example 1 Example 2 Comparative Example Number of bends at break 850 662 25

Referring to Table 1 and FIG. 6, in Example 1 using cobalt sulfate, the plating layer was broken at 850 times of bending times. In Example 2 using cobalt sodium hypophosphite, the plated layer was broken at the number of times of flexing 662 times.

On the other hand, in the comparative example including nickel, the plating layer was broken at the number of times of bending 25 times.

Therefore, the cobalt plating solutions of Examples 1 and 2 can form a plating layer having better bending properties, compared with the nickel plating solution of the comparative example.

FIG. 7 is a scanning electron microscope photograph showing the fracture shape of the plating layers after the proofing test in FIG. 6; FIG.

Referring to FIG. 7, in both of Example 1 using cobalt sulfate and Example 2 using cobalt sodium hypophosphite, the plated layer was fractured in multiple pieces and fractured. It is analyzed that the progress of the destruction is disturbed by the obstacles, and the destruction starting point is generated, and the growth destruction is merged to the final destruction. Generally, in this case, the resistance to destruction is great.

On the other hand, in the comparative example including nickel, the plated layer showed a destructive fracture in a straight line. This means that there is a single fracture initiation point, from which destruction proceeds, with no or few obstacles to obstruct or block the destruction, and thus the progress of destruction is analyzed to be very fast. In this case, the resistance to failure is small.

The results of FIG. 7 are consistent with the results of FIG. The reason for this is that the fracture fractures in Examples 1 and 2 result in a large fracture resistance of the plating layer, resulting in a large bending strength. On the other hand, the fracture in the comparative example indicates that the fracture resistance of the plating layer is small as a result, so that the bending strength is small.

FIG. 8 is a scanning electron microscope photograph showing a fracture section of plating layers after the shrinkage test of FIG. 6; FIG.

Referring to FIG. 8, in Example 1 using cobalt sulfate and Example 2 using cobalt sodium hypophosphate, the fracture section of the plated layer indicates that fracture occurred along the grain boundaries of the plated layer. Therefore, even if the fracture starts, it proceeds according to the grain boundaries, so that the fracture rate is analyzed to be slow. In other words, brittle fracture and ductile fracture were mixed. On the other hand, in the nickel-containing comparative example, the fracture surface of the plated layer indicates fracture similar to brittle fracture. Therefore, once the fracture starts in the plating layer of the comparative example, it is analyzed that the fracture proceeds at a high speed. Therefore, the first and second embodiments have ductility improving effect.

Table 2 is a table showing the bonding strength test results of the plating object in which the plating layer is formed by using the cobalt plating solution of the embodiments of the present invention and the nickel plating solution of the comparative example, respectively. FIG. 9 is a graph showing the results of the bonding strength test of the plating object in which the plating layer is formed using the cobalt plating solution of the embodiments of the present invention and the nickel plating solution of the comparative example, respectively. The bonding strength test was carried out three times for each plating solution.

division One 2 3 Average (g) Example 1 3455 3615 3746 3605 Example 2 4869 4002 5102 4657 Comparative Example 3465 3874 3259 3532

Referring to Table 2 and FIG. 9, in Example 1 using cobalt sulfate, an average bonding strength of 3605 g was shown. In Example 2 using cobalt sodium hypophosphite, an average bonding strength of 4657 g was shown. The bonding strength of Example 2 was larger than that of Example 1.

On the other hand, the comparative example including nickel showed an average bonding strength of 3532 g. The bonding strength of the comparative example was similar to that of Example 1 and smaller than that of Example 2. [

Thus, Example 1 and Example 2 show bonding strengths that are similar to or greater than the bonding strength of commercial nickel plating liquids, so that the bonding strength required for the plating layer can be provided.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. Will be apparent to those of ordinary skill in the art.

10: plating apparatus, 20: plating bath,
30: Cobalt plating solution, 40: Plating object, 50: Plating layer,

Claims (20)

A cobalt metal salt providing a cobalt ion for plating;
A reducing agent for reducing the cobalt ions for plating;
A complexing agent which forms a complex with the cobalt ions for plating and contains at least one of a carboxylic acid and an aliphatic acid; And
A main stabilizer stabilizing the cobalt ions for plating and containing ammonium sulfate;
And an electroless cobalt plating solution. The electroless cobalt plating solution according to claim 1, wherein the cobalt metal salt comprises at least one of cobalt sulfate, cobalt sulfamate, cobalt acetate, and cobalt chloride. The electroless cobalt plating solution according to claim 1, wherein the cobalt metal salt is contained in the range of 2 g to 7 g with respect to 1 liter of the cobalt plating solution. The electroless cobalt plating solution according to claim 1, wherein the reducing agent comprises at least one of hypophosphite, boron hydride, dimethylamine borane, and hydrazine. The electroless cobalt plating solution according to claim 1, wherein the reducing agent is contained in an amount ranging from 20 g to 100 g per 1 liter of the cobalt plating solution. 2. The electroless cobalt plating solution of claim 1, wherein the complexing agent comprises citric acid, glycine, lactic acid, or both. The electroless cobalt plating solution according to claim 1, wherein the complexing agent is contained in an amount ranging from 10 g to 70 g based on 1 liter of the cobalt plating solution. The electroless cobalt plating solution according to claim 1, wherein the complexing agent is a carboxylic acid and a derivative thereof, and is contained in an amount ranging from 10 g to 30 g per 1 liter of the cobalt plating solution. 2. The electroless cobalt plating solution according to claim 1, wherein the complexing agent is an alpha hydroxy acid and a derivative thereof, and is contained in an amount ranging from 10 g to 50 g per liter of the cobalt plating solution. The electroless cobalt plating solution according to claim 1, wherein the complexing agent is a single component or a mixed component. The electroless cobalt plating solution according to claim 1, wherein the main stabilizer is contained in an amount of 10 g to 30 g based on 1 liter of the cobalt plating solution. The metal stabilizer according to claim 1, wherein the metal stabilizer suppresses the reduction reaction of the cobalt ions for plating and is contained in the range of 0.1 ppm to 5.0 ppm relative to 1 liter of the cobalt plating solution;
Further comprising an electroless cobalt plating solution. The method of claim 12, wherein the metal stabilizer is selected from the group consisting of lead (Pb), thallium (Tl), tellurium (Te), selenium (Se), bismuth (Bi), tin (Sn), cadmium (Cd), and molybdenum Mo). ≪ / RTI > The cobalt plating solution according to claim 1, wherein the cobalt plating solution is naturally decomposed to prevent the precipitate formed by aging of the cobalt plating solution from reacting with the reducing agent to stabilize the cobalt plating solution, A sulfide-based stabilizer contained in the range of 0.1 ppm to 5.0 ppm;
Further comprising an electroless cobalt plating solution. The method of claim 14, wherein the sulfide-based stabilizer is at least one selected from the group consisting of electroless cobalt (TiO2) and at least one compound selected from the group consisting of thiourea and derivatives thereof, sulfite, pyrosulfite, and thiocyanate. Plating solution. The surfactant according to claim 1, wherein the surfactant increases the interfacial characteristics and wettability of the plating layer, and contains an alkyl sulfate-based surfactant in an amount of 1.0 ppm to 20 ppm based on 1 liter of the cobalt plating solution.
Further comprising an electroless cobalt plating solution. The method of claim 1, further comprising: adjusting the pH of the cobalt plating solution to a range of 7.5 to 9.5 and adjusting at least one of sulfuric acid, hydrochloric acid, nitric acid, ammonia water, sodium hydroxide, and potassium hydroxide;
Further comprising an electroless cobalt plating solution. 17. A method for manufacturing a semiconductor device, comprising: preparing an electroless cobalt plating solution according to any one of claims 1 to 17; And
Immersing the plating object in the electroless cobalt plating liquid to form an electroless plating layer on the plating object;
The electroless plating method using the electroless cobalt plating solution. The electroless plating method according to claim 1, wherein in the step of forming an electroless plating layer on the plating object, the electroless cobalt plating liquid has a temperature in a range of 60 캜 to 95 캜. 17. A cobalt plated layer plated on a surface of a plating object by an electroless cobalt plating solution according to any one of claims 1 to 17.

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