KR101146769B1 - Electroless nikel plating solution, electroless plating method using the same and nikel coating layer prepared by the same - Google Patents

Abstract

The present invention includes metal additives, cyanide additives, sulfides in an electroless nickel plating solution containing nickel sulfate as a metal salt, sodium hypophosphite as a reducing agent, and adipic acid, succinic acid, citric acid and lactic acid mixed as a complexing agent. By further adding any one or more of the system additives, it relates to an electroless nickel plating solution with a very increased stability, an electroless plating process using the same and a nickel plating layer produced thereby.

Description

Electroless nickel plating solution, electroless plating process using the same and nickel plating layer produced by the same {Electroless nikel plating solution, electroless plating method using the same and nikel coating layer prepared by the same}

The present invention relates to an electroless nickel plating solution, an electroless plating process using the same, and a nickel plating layer prepared by the same, and more particularly, a metal additive to a plating solution in which adipic acid, succinic acid, citric acid, and lactic acid are mixed as a complexing agent. By further adding any one or more of the cyanide-based, sulfide-based additives, relates to an electroless nickel plating solution with very increased stability, an electroless plating process using the same, and a nickel plating layer produced thereby.

Since the plating by the electroless plating method utilizes reduction by the contact action of the surface of the material, the concave portion can be plated with a constant thickness. The electroless plating method may be classified into a substitution plating method which can obtain plating by only depositing a plated metal in a solution and a chemical plating method using chemical reduction.

The final plated surface by the electroless plating method is used as a mounting interface of a dense ultra-compact device and the like by various packaging technologies, and the importance in the parts and materials industry is increasing day by day. In addition, in recent years, due to the weight reduction, miniaturization, and high functionality of electronic components, high density and narrow pitch of internal circuits are required. Therefore, there is a need for an electroless plating method having a small variation in plating thickness without being affected by the plating area or plating shape. It is increasing.

In particular, the plated film formed by the electroless nickel plating method is capable of amorphous alloy plating by controlling the amount of deposition of phosphorus vacancy, and it is possible to obtain a uniform surface, which is excellent in diffusion preventing properties, corrosion resistance and abrasion resistance. It is used as a plating for the final surface treatment of electronic material parts, and its history is old. In recent years, it has been widely used in a wide variety of fields for the ground treatment of solder joints of printed wiring boards or for the primary treatment of compact disks (CDs) and hard disk drives (HDDs).

Conventional electroless nickel plating solutions contain nickel salts as metal salts providing divalent nickel ions, reducing agents capable of reducing divalent nickel ions, complexing agents capable of forming complexes with divalent nickel ions, pH regulators and stabilizers. It is common to do it.

As the nickel salt for providing the divalent nickel ions described above, nickel chloride such as nickel chloride, nickel sulfate, nickel sulfamate, and the like can be used. Examples of reducing agents for reducing divalent nickel ions include hypophosphite, borohydride, Dimethylamine borane, hydrazine and the like can be used. In addition, as a complexing agent that forms a complex with divalent nickel ions, amine compounds such as ethylenediamine, ethylenediaminetetraacetate, greencin, carboxylic salts such as citric acid, malic acid, succinic acid, tartaric acid, and the like can be used. In addition, an acidic aqueous solution such as sulfuric acid and hydrochloric acid and an alkaline aqueous solution such as ammonia water, sodium hydroxide and potassium hydroxide may be used as the pH adjuster. In addition, as a stabilizer, any one of thio compounds selected from thioglycolic acid, dithioglycolic acid, thioglycolic acid, and dithiodiglycolic acid and any thallium compound selected from thallium nitrate and thallium sulfate may be used.

However, in the case of the conventionally used electroless nickel plating liquid, it is somewhat unstable, thereby producing metal fine particles in the plating liquid or increasing the roughness of the plating film due to the incorporation of fine particles generated in the plating film, or pits occur. As a result, there was a problem in that gloss deterioration, corrosion resistance deterioration and the like occurred.

In addition, as a disadvantage of the electroless plating method, there is a problem that the lifetime of the electroless nickel plating solution is short, so that the efficiency is economically reduced and the productivity is lowered.

In view of the problems described above, the inventors of the present invention have shown that 1) more stable, 2) no pits in the plated coating, 3) no crystal grains are formed, and 4) plating solution compared with the conventionally used electroless nickel plating solution. Its lifespan has increased, leading to the invention of an electroless nickel plating solution that can improve efficiency economically.

The present invention has been made to solve the above-described problems, the object of the present invention, any of metal additives, cyanide additives, sulfide-based additives in the plating solution is mixed with adipic acid, succinic acid, citric acid and lactic acid as a complexing agent By adding one or more more, it is to provide an electroless nickel plating solution with a very increased stability.

It is also an object of the present invention to provide an electroless nickel plating solution which can increase the lifetime of the electroless nickel plating solution itself and economically improve the efficiency and productivity of the plating process.

It is also an object of the present invention to provide an electroless plating process capable of forming an amorphous plating film having no pits and no crystal grains formed in the plated film by performing the plating process using the electroless nickel plating solution described above. It is.

In addition, an object of the present invention, by performing the plating process using the electroless nickel plating solution described above, it is possible to maintain a stable plating solution even at 10 MTO or more and have a high plating speed, an electroless plating process that can improve productivity. To provide.

It is also an object of the present invention to provide an amorphous nickel plating layer in which the coated film is free of pits or cracks and no crystal grains are formed by using the electroless plating process described above.

As one aspect for achieving the above object, the present invention comprises nickel sulfate as metal salt, sodium hypophosphite as reducing agent, and adipic acid, lactic acid, succinic acid and citric acid as complexing agent. It relates to an electroless nickel plating solution.

Complexing agents are generally added to control the plating rate, to prevent spontaneous decomposition of the electroless nickel plating solution, and to control the plating reaction so that the reduction reaction occurs only on the metal surface. The complexing agent is an organic acid or a salt thereof, which controls the total amount of nickel ions participating in the reduction reaction and stabilizes the electroless nickel plating solution by delaying the precipitation of nickel ions into nickel phosphate. In addition, the complexing agent also serves to suppress the pH change of the electroless nickel plating solution by reducing the rapid generation of hydrogen ions by the reduction reaction.

In the plating liquid, citric acid and lactic acid have high ignition ability to stabilize the plating liquid and reduce plating speed, and adipic acid and succinic acid not only stabilize the plating liquid but also improve the plating speed which is drastically lowered due to citric acid and lactic acid. In more detail, the rate of plating is improved by weakening the bonding force between hydrogen and phosphorus atoms in the hypophosphorous acid molecule.

At this time, it is preferable that 5 to 7 g of nickel sulfate is contained with respect to 1 L of plating liquid as a metal salt, and 20 to 35 g is contained with respect to 1 L of plating liquid as a reducing agent.

When the concentration of nickel sulfate in the plating liquid is less than 5 g / l, the plating rate is lowered. When the concentration of nickel sulfate is more than 7 g / l, the plating rate is increased, but spontaneous decomposition of the plating liquid is likely to occur. Similarly, if the concentration of sodium hypophosphite is less than 20 g / l, the plating rate is lowered and productivity is lowered. If the concentration of sodium hypophosphite is higher than 35 g / l, the plating rate is increased, but the stability of the solution is lowered. There are disadvantages.

At this time, as a complexing agent, adipic acid is contained in 5 to 25 g per 1 L of the plating liquid, lactic acid is contained in 5 to 20 g per 1 L of the plating liquid, succinic acid is contained in 5 to 20 g per 1 L of the plating liquid, and citric acid is 5 to 1 L of the plating liquid. It is preferable to contain 20g. Moreover, the total content of these complexing agents is most preferably 20 to 30 g per 1 L of the plating liquid.

If the mixed amount of adipic acid, succinic acid, citric acid and lactic acid in the plating liquid is within the above-mentioned range, the stability of the solution may be deteriorated and the plating liquid may be decomposed. There is a possibility that the speed is reduced and economic efficiency is lowered.

The electroless nickel plating solution further includes a metal additive, and the metal additive is selected from the group consisting of Sn, Zn, Mg, Pb, Tl, Se, Te, Mo, As, Bi, and mixtures thereof. .

The metal additive is added to improve the stability of the plating solution and the glossiness of the plating film, and the metal additive is added to the plating solution to stabilize the plating solution by suppressing a reduction reaction other than the metal surface to be plated.

At this time, the metal additive is preferably 0.1 to 5.0ppm. For this reason, when the metal additive is less than 0.1 ppm, the stability of the plating liquid and the glossiness of the plating film are lowered, and when it exceeds 5.0 ppm, the plating rate is very low.

The electroless nickel plating solution further includes a first stabilizer, and the first stabilizer is a cyan-based (CN-) compound. Preferably, the cyan-based compound is selected from the group consisting of NaSCN, KSCN, NaCN, KCN and mixtures thereof. The first stabilizer serves to prevent the occurrence of pits in the plated film to further improve the properties of the plated film.

In addition, the electroless nickel plating solution further includes a second stabilizer, the second stabilizer is selected from the group consisting of thiourea, K ₂ S ₂ O ₅ , NaS ₂ O ₃ and mixtures thereof. do. The second stabilizer inhibits spontaneous decomposition and the like of the plating liquid, and serves to stabilize the plating liquid by preventing hydrogen gas from being generated by reacting with the precipitation and reducing agent caused by aging of the plating liquid. On the other hand, it is noted that not only the above-mentioned compound but also all kinds of sulfide compounds can be used as the second stabilizer.

At this time, the first stabilizer is added in the range of 0.1 to 5.0 ppm and the second stabilizer is preferably added in the range of 0.1 to 5.0 ppm. This is because when the first stabilizer is less than 0.1 ppm, the plating rate is lowered. When the first stabilizer is higher than 5.0 ppm, crystal grains are formed in the plated film, thereby degrading the properties of the plated film. If the second stabilizer is less than 0.1 ppm, the stability of the plating liquid is lowered. If the second stabilizer is more than 5.0 ppm, pits are generated in the plating film, and crystal grains are formed to deteriorate the characteristics of the plating film.

The electroless nickel plating solution further includes any one or more of aqueous ammonia and sulfuric acid as a pH adjuster, characterized in that the pH of the electroless nickel plating solution is maintained in the range of 3.5 to 5.5. pH adjuster means a material used to prevent the pH change of the plating solution during the plating process. Since the plating is affected by the degree of plating and the thickness of the plating layer by the pH, it is preferable to add a material that can control the pH of the plating liquid.

When the pH range of the electroless nickel plating solution is 3.5 to 5.5, the electroless nickel plating solution can be more stably maintained, and the plating is effectively performed while the plating speed is high, thereby obtaining a high quality plating film.

As still another aspect of the present invention, the present invention includes the step of plating a metal (eg, iron) using the electroless nickel plating solution described above to form a nickel plating layer on the metal surface. It is related with the plating process.

At this time, the electroless plating process is preferably carried out in a temperature range of 70 to 95 ℃ and pH range of 3.5 to 5.5. These process conditions are set to minimize chemical effects such as deformation or erosion on the metal surface on which the nickel plating layer is formed, and are more easily set such that the nickel plating layer is formed on the metal surface.

In order to maintain the temperature of the plating liquid, it was intended to suppress decomposition of the plating liquid by using a hot bath method, and to stir using a magnetic bar, the plating liquid was rocked in the plating bath so that the nickel ions were easily precipitated on the plating material.

In particular, according to the process temperature range and the process pH range, it is possible to prevent the spontaneous decomposition of the plating liquid to maintain the plating liquid more stably, acidic electroless nickel plating can be more easily precipitated, the pit on the plated nickel plating layer And can reduce the formation of crystal grains.

As another aspect of the present invention, the present invention relates to a nickel plating layer plated on a metal surface by the electroless nickel plating solution described above.

According to the present invention, plating of the electroless plating solution of the heavy metal type by further adding any one or more of a metal additive, a cyanide additive, and a sulfide additive to a plating solution containing adipic acid, succinic acid, citric acid and lactic acid as a complexing agent There is an effect that the stability can be greatly increased by controlling spontaneous decomposition while increasing the speed.

In addition, according to the present invention, the lifespan of the electroless nickel plating solution itself is increased to economically improve the efficiency and productivity of the plating process.

In addition, according to the present invention, by performing the plating process using the electroless nickel plating solution described above, there is an effect that an amorphous plating film without pit and crystal grains is formed in the plated film.

Further, according to the present invention, by performing the plating process using the electroless nickel plating solution described above, it is possible to maintain a stable plating solution even at 10 MTO or more and to have a high plating rate of about 12 μm / h, thereby improving the productivity of the plating process. It can be effective.

In addition, according to the present invention, by using the electroless plating process described above, there is no pit or crack in the plated film, no crystal grains are formed, and an amorphous nickel plating layer having excellent hardness, abrasion resistance, and corrosion resistance can be formed. There is.

1 is a photograph of the appearance of the plating film formed by the electroless nickel plating solution prepared by Comparative Preparation Example 1,
Figure 2 is a photograph of the appearance of the plating film formed by the electroless nickel plating solution prepared by Preparation Example 1 according to the present invention,
3 is a photograph of the appearance of the plating film formed by the electroless nickel plating solution prepared by Preparation Example 2 according to the present invention,
4 is a photograph of the appearance of the plating film formed by the electroless nickel plating solution prepared by Preparation Example 3 according to the present invention.

Hereinafter, the content of the present invention will be described in more detail with reference to Examples. However, the following examples are merely provided to more easily understand the present invention, and the present invention is not limited by these examples.

<Comparative Production Example 1>

A solution was prepared such that 22 g of nickel sulfate was dissolved in 1 L of the solvent so that the concentration of nickel ions was about 5 g / L. Then, 25 g of sodium hypophosphite was dissolved in 1 L of another solvent, and a solution B was prepared by mixing 10 g / l of adipic acid, 5 g / l of succinic acid, 5 g / l of citric acid, and lactic acid with a complexing agent. Then, A solution and B solution were mixed to prepare a plating solution. At this time, the pH of the plating solution was kept constant at about 4.5 using ammonia water. In this way an electroless nickel plating solution was obtained.

On the other hand, when dissolving nickel sulfate as a metal salt and sodium hypophosphite as a reducing agent at the same time, the plating solution can be easily decomposed, so a solution in which nickel ions are dissolved (A solution) and a solution in which sodium hypophosphite is dissolved (B solution) are dissolved. Note that they are prepared separately and mixed.

<Manufacture example 1>

A solution and B solution were prepared in the same manner as in Comparative Preparation Example 1. However, 0.1 ppm of thallium (Tl) was added to the solution B, 0.5 ppm of sodium thiocyanate (NaSCN) was added, and 0.1 ppm of thiourea was added to prepare a solution B. It was. Then, A solution and B solution were mixed to prepare a plating solution. At this time, the pH of the plating solution was kept constant at about 4.5 using ammonia water. In this way an electroless nickel plating solution was obtained.

<Manufacture example 2>

A solution and B solution were prepared in the same manner as in Comparative Preparation Example 1. However, 0.1 ppm of thallium (Tl) is further added to the solution B, 1.0 ppm of sodium thiocyanide (NaSCN) is added, and 0.1 ppm of potassium metabisulfite (K ₂ S ₂ O ₅ ) is added. It was further added to prepare a B solution. Then, A solution and B solution were mixed to prepare a plating solution. At this time, the pH of the plating solution was kept constant at about 4.5 using ammonia water. In this way an electroless nickel plating solution was obtained.

<Manufacture example 3>

A solution and B solution were prepared in the same manner as in Comparative Preparation Example 1. However, 0.5 ppm of thallium (Tl) was added to the solution B, 0.5 ppm of sodium thiocyanide (NaSCN) was added, and 0.5 ppm of thiourea was added to prepare the solution B. It was. Then, A solution and B solution were mixed to prepare a plating solution. At this time, the pH of the plating solution was kept constant at about 4.5 using ammonia water. In this way an electroless nickel plating solution was obtained.

&Lt; Preparation Example 4 &

A solution and B solution were prepared in the same manner as in Comparative Preparation Example 1. However, 0.5 ppm of thallium (Tl) is further added to the solution B, 1.0 ppm of sodium thiocyanide (NaSCN) is added, and 0.5 ppm of potassium metabisulfite (K ₂ S ₂ O ₅ ) is added. It was further added to prepare a B solution. Then, A solution and B solution were mixed to prepare a plating solution. At this time, the pH of the plating solution was kept constant at about 4.5 using ammonia water. In this way an electroless nickel plating solution was obtained.

Experimental Example 1 Performance Comparison of the Electroless Nickel Plating Solution

In order to compare the performance of the electroless nickel plating solution according to the present invention, the following plating process was performed using the electroless nickel plating solution prepared in Preparation Examples 1, 2, 3 and Comparative Preparation Example 1.

1) 5 minutes deposition using 10% sulfuric acid to remove the coated zinc of the iron material for the hull cell test;

2) washing the iron material with non-phosphorus water;

3) soft etching treatment and water washing treatment for 1-2 minutes in the temperature range of 20-30 ° C. to improve adhesion;

4) Perform the plating process (The temperature of the plating liquid is kept constant at about 85 ° C. using a hot bath method, the pH of the plating liquid is kept constant at about 4.5 using ammonia water, and the plating time is performed for about 1 hour.)

The surface appearance of each nickel plating layer obtained through this process was compared through FIGS. 1 to 4.

1 is a photograph of the plating film formed by the electroless nickel plating solution prepared by Comparative Preparation Example 1, and FIG. 2 is a plating film formed by the electroless nickel plating solution prepared by Preparation Example 1 according to the present invention. 3 is a photograph of the appearance of the plating film formed by the electroless nickel plating solution prepared by Preparation Example 2 according to the present invention, and FIG. 4 is prepared by Preparation Example 3 according to the present invention. It is a photograph regarding the appearance of the plating film formed by the electroless nickel plating solution.

Referring to FIG. 1, it can be seen that a large amount of pits occurred on the surface of the plated nickel plating layer. Meanwhile, in this case, the plating rate was 13.1 μm / h, and the amount of vacancy in the precipitated phosphorus in the plated nickel plating layer was 8.9 wt.%. The electroless nickel plating solution was spontaneously decomposed after a certain time.

Referring to FIG. 2, although some pits occurred on the surface of the plated nickel plating layer, it was found that the nickel plating layer having an amorphous shape was plated as a whole. Meanwhile, in this case, the plating rate was 21 μm / h and the amount of vacancy in the deposited phosphorus in the plated nickel plating layer was 7.3 wt.%.

Referring to FIG. 3, it could be seen that an amorphous nickel plating layer having no pits or cracks and no crystal grains was formed on the surface of the plated nickel plating layer. On the other hand, in this case the plating rate was 20.8㎛ / h and the amount of vacancy in the precipitated phosphorus in the plated nickel plating layer was 6.8wt.%. And it was found that the electroless nickel plating solution did not decompose for a considerable time.

Referring to FIG. 4, it could be seen that an amorphous nickel plating layer having no pits or cracks and no crystal grains was formed on the surface of the plated nickel plating layer. Meanwhile, in this case, the plating rate was 21.1 μm / h, and the amount of vacancy in the precipitated phosphorus in the plated nickel plating layer was 6.7 wt.%. And it was found that the electroless nickel plating solution did not decompose for a considerable time.

Experimental Example 2 MTO (metal turn over) test

The MTO (metal turn over) test is a method of indicating the life of a plating solution in an electroless nickel plating solution, and the sum of the plating solution life and the precipitation amount represents a multiple of the weight of the metal contained in the first dry solution, which is expressed as MTO. . For example, if 5 g of nickel is currently dissolved in the plating solution, the point at which 5 g of nickel is consumed is 1 MTO, that is, 1 MTO corresponds to the amount of plated metal.

The MTO test was performed using the electroless nickel plating solution prepared in Preparation Example 4. The metal or reducing agent consumed when performing the MTO test was added through analysis. And the plating rate was measured for every MTO. The plating rates measured are listed in Table 1 below.

MTO One 2 3 4 5 6 7 8 9 10 Plating rate
(Μm / h) 17.9 16.1 16.2 16.2 14.5 14.1 13.1 13.5 12.1 12

Referring to Table 1, MTO experiments using the electroless nickel plating solution prepared in Preparation Example 4 showed that plating rates of 12 µm / h or more were obtained even at 10 MTO, and the electroless nickel plating solution itself was also stable. Could know.

Considering that most of the currently commercially available electroless nickel plating solutions are decomposed at around 5 MTO, which is economically problematic in terms of plating cost, the electroless nickel plating solution according to the present invention is stable and plated up to 10 MTO. Since the speed is maintained, the plating process can be performed more efficiently and economically.

As mentioned above, although the present invention has been illustrated and described with reference to specific embodiments, the present invention is not limited thereto, and the following claims are not limited to the scope of the present invention without departing from the spirit and scope of the present invention. It can be easily understood by those skilled in the art that can be modified and modified.

Claims (12)

Nickel sulfate as a metal salt;
Sodium hypophosphite as reducing agent;
Adipic acid, lactic acid, succinic acid and citric acid as complexing agents;
Tl as a metal additive;
NaSCN as the first stabilizer; And
Comprising thiourea or K ₂ S ₂ O ₅ , as a second stabilizer,
Electroless Nickel Plating Solution.
The method of claim 1,
Per 1 L of the plating solution, 5 to 25 g of the adipic acid, 5 to 20 g of the lactic acid, 5 to 20 g of the succinic acid, and 5 to 20 g of the citric acid,
Electroless Nickel Plating Solution.
delete The method of claim 1,
The metal additive is characterized in that it is added in the range of 0.1 to 10.0 ppm,
Electroless Nickel Plating Solution.
delete delete delete The method of claim 1,
Wherein the first stabilizer is added in the range of 0.1 to 5.0 ppm, and the second stabilizer is added in the range of 0.1 to 5.0 ppm,
Electroless Nickel Plating Solution.
The method of claim 1,
The electroless nickel plating solution further comprises any one or more of aqueous ammonia and sulfuric acid as a pH adjuster, characterized in that the pH of the electroless nickel plating solution is maintained in the range of 3.5 to 5.5,
Electroless Nickel Plating Solution.
A method of forming a nickel plating layer on a metal surface by plating a metal using the electroless nickel plating solution according to any one of claims 1, 2, 4, 8 and 9. Characterized by
Electroless Plating Process.
The method of claim 10,
The electroless plating process is characterized in that it is carried out in a temperature range of 70 to 95 ℃ and a pH range of 3.5 to 5.5,
Electroless Plating Process.
It is plated on the metal surface by the electroless nickel plating solution as described in any one of Claims 1, 2, 4, 8, and 9.
Nickel plating layer.

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