KR20050101057A - Electroless nickel plating solution, plating method for powder - Google Patents

Abstract

Electroless nickel which has irregular nickel-phosphorium plating layer on the surface of powder grinding material to improve bonding bonding of grinding wheels such as CBN, diamond, alumina and silicon carbide to grinding wheel. The plating solution and its plating method are improved.

According to the present invention, there is provided an electroless nickel plating solution for powder consisting of a nickel salt, a complexing agent and a pH adjusting agent and sodium dental phosphate which is a high concentration reducing agent of 100 to 700 g / L added separately from this.

In addition, according to the present invention as a method for plating the powder grinding material with a powder type electroless nickel plating solution,

After filling the plating liquid except the reducing agent in the plating tank, the powder grinding material pretreated by the usual method is added, and the temperature is raised to 60-90 ° C. When the temperature is reached, the reducing agent is 0.1 to 0.3 compared to the plating liquid at the beginning of plating. In order to cause the plating reaction by volume% and to obtain the target precipitation amount, the first plating for dispensing the specified reducing agent for a predetermined time and the nickel plating by immersing the powder grinding material in the normal activation solution for 1-2 minutes after the first plating. After adsorbing Pd ion on the surface layer, secondary plating is performed on the powder grinding material to which the Pd ion is adsorbed in the same manner as the primary plating. Electroless nickel plating method of powder grinding material consisting of adsorbing Pd ion to nickel plated surface layer after secondary plating and tertiary plating powder grinding material adsorbed Pd ion in the same way as primary plating This is provided.

Description

Electroless Nickel Plating Solution and Plating Method for Powder Grinding Material

The present invention relates to an electroless nickel plating solution and a plating method thereof. More specifically, the present invention relates to powder grinding materials such as cubic boron nitride (CBN), diamond, alumina, silicon carbide, etc. The present invention relates to an electroless nickel plating and plating method in which the surface of has a nickel-phosphorus alloy plating layer of irregular shape.

By the late 19th century, abrasive tools relied on naturally formed abrasives. Therefore, a process for producing a large amount of abrasive grains under strictly controlled conditions was required. As a result, the introduction of an electric furnace process for producing silicon carbide resulted in mass production of abrasive grains. Alumina was then developed.

However, the processing of many materials required by the industry requires harder and stronger abrasives than alumina or silicon carbide. In 1955, General Electric (GE) of the United States succeeded in making diamonds, and in addition to the diamond synthesis research, a unique material, CBN (Cubic Boron Nitride) was synthesized. CBN has a higher hardness than any other materials except diamond, suggesting considerable potential as an abrasive and is now an indispensable abrasive in the industry.

In general, various grinding materials such as silicon carbide, alumina, diamond and CBN are used for grinding tools used in the industry. Such a grinding material is uniformly bonded through a bonding operation to the grinding wheel to exhibit the performance as a grinding tool. However, the surface of the grinding material itself has a smooth surface layer, so that the grinding material bonded to the grinding wheel may be separated from the grinding wheel during the grinding process. Although the grinding wheel and the grinding material are bonded through the bonding process, it is caused by the deterioration of the bonding force due to the characteristics of the surface of the grinding material itself. This result in a problem of rapidly deteriorating the life of the grinding wheel and difficult to machine to the correct dimensions. In addition, the use of expensive diamonds or CBN can cause significant losses in terms of cost. In order to reduce this drawback, that is, irregular electroless nickel coating is applied to improve the bonding strength when bonding the grinding material and the grinding wheel. In this regard, Korean Patent Publication No. 2003-36277 discloses an acidic electroless nickel plating solution. The grinding material has a smooth surface layer, but the present invention provides an electroless nickel coating having the most irregular shape on the smooth surface layer, thereby greatly improving the bonding property in a subsequent bonding process between the powder grinding material and the grinding wheel having the maximum surface area at a constant volume. can do.

In addition, in the case of the grinding material, it is a non-conductor in the form of powder and it does not conduct current, so it is possible to metallize it through electroless plating, which requires the pretreatment of the powder to enable metallization on the surface of the powder. This allows cost savings by entering the electroless nickel plating process immediately after pretreatment.

However, the electroless nickel plating solution as disclosed in the above-mentioned patent is used in one batch by preparing a single solution of other additives such as nickel salts, reducing agents, pH regulators, and stabilizers. However, in the case of electroless plating of fine powder, the active surface area of the plating reaction is very large because the specific surface area of the fine powder particles is much larger than that of ordinary plating. Therefore, when plating using a conventional electroless nickel plating solution, the initial plating reaction rate is very high, which causes problems such as bath decomposition at the initial stage of plating or generation of Ni fine particles at portions other than the surface of the plated body. In addition, there is a drawback that the grinding material of the intact powder cannot be obtained due to the aggregation phenomenon of the powder and the powder.

The present invention is to solve the problems of the prior art as described above, in the case of the electroless plating solution to determine that there is a limit to the stable plating of the fine powder to improve this through the electroless nickel plating solution and plating method for powder. Therefore, an object of the present invention is to control the reaction between the catalyst treated powder and nickel ions at the beginning of plating by controlling the input amount of the reducing agent by dualizing with a plating solution containing nickel salt, a complexing agent and a pH adjusting agent and a solution containing only a reducing agent. It is to provide a nickel plating solution for powder that can suppress the decomposition of the self and the production of Ni particles in the portion other than the surface to be plated. Still another object of the present invention is to provide an electroless nickel plating method on a powder capable of controlling the amount of deposition by adding a stabilizer and an accelerator to control the plating speed during the plating operation according to the plating purpose. The electroless nickel plating in the present invention is carried out in three steps and in order to obtain a more irregular plating shape after the first and second electroless nickel plating, the next electroless nickel plating process is performed by immersing the palladium catalyst solution or adding palladium ions. It is characterized by performing.

In order to achieve the object of the present invention as described above, the present invention,

It provides a powdered electroless nickel plating solution consisting of a nickel salt, a complexing agent and a pH adjusting agent, a pH buffer (A solution) and a reducing agent of high concentration sodium hypophosphite having a concentration of 100 to 700 g / L.

Nickel sulfate, which is a metal nickel salt, is used as the nickel salt, succinic acid is used as a complexing agent, ammonia water is used as a pH regulator, and acetic acid is used as a pH buffer.

In addition, when reducing the plating reaction rate during plating of the plating liquid, a small amount of lead chloride LAT may be added, or a small amount of a fluoride and / or sulfide accelerator may be added depending on the plating purpose.

The present invention also, by using a plating solution as described above, after the first and second nickel plating powder of CBN or the like and immersed in the palladium catalyst solution for 1 to 2 minutes to impart a palladium catalyst to the plating layer, and then electroless nickel plating powder It provides an electroless nickel plating method.

In the first and second nickel plating, the activation solution may be added to the nickel plated layer before the plating is completed.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments.

First, nickel salt in this invention uses nickel sulfate as a metal nickel salt. At this time, nickel sulfate used is 20 ~ 150g / L. If the concentration is less than 20g / L, the plating speed is decreased. If the concentration is more than 150g / L, the plating speed is increased but decomposition of plating solution occurs. easy. Preferred concentrations of the metal nickel salt are 30 to 100 g / L.

The complexing agent controls the plating rate and prevents the plating solution from self-decomposing. In the present invention, succinic acid is used. In the case of succinic acid, it is used at 5 ~ 50g / L. If the concentration is 5g / L or less, the amount of nickel ions which do not ignite increases, so that plating is not effective. If the concentration is 50g / L or more, the stability of the plating solution is Increases but decreases plating speed. Therefore, the concentration of succinic acid is preferably 5 ~ 30g / L.

In addition, the pH adjuster uses ammonia water to adjust the pH of the plating solution. With such a pH adjuster to adjust the pH of the plating solution to 4.5 ~ 6.5, at this pH the plating speed is fast and the plating is effectively performed. The pH of the plating liquid is most suitable 4.5 ~ 6.0.

       In addition, the pH buffering agent uses acetic acid in order to prevent a sudden drop in the pH of the plating solution while plating. The pH buffering agent is used at 3 ~ 20ml / L, but it depends on the content of complexing agent. However, the pH buffering effect is generally less than 3ml / L and more than 20ml / l. none.

In addition, lead chloride (LAT), a stabilizer, may be added with 1 to 3 ppm to reduce the plating reaction rate if necessary to suppress the autolysis reaction of the plating solution. If it is less than 1ppm, it does not perform as a stabilizer, and if it is more than 3ppm, the plating reaction is not stopped or partially plated.

In addition, fluorides and / or sulfides (ACT), which are accelerators, may be used to increase the amount of precipitation depending on the plating purpose of the powder, that is, when the accelerator is not used at the same time. In this case, about 1 to 3 ppm is appropriate. It is because the effect is not exerted at 1 ppm or less, and at 3 ppm or more, it shows bad results such as autolysis reaction.

The concentration of sodium hypophosphate in a typical electroless nickel plating solution in which nickel salts, complexing agents, and reducing agents are added in a solution is 20-50 g / L. However, the concentration of sodium hypophosphite used as a reducing agent in the present invention is quite high concentration of 100 ~ 700g / L. Because the high concentration of reducing agent is added to the A solution containing nickel salt through the metering pump at a rate of about 1 ml per minute, the concentration is higher than that of the general electroless nickel plating solution to increase the initial reaction rate. If less than 100g / L, the initial plating reaction rate is slow and more than 700g / L reaction rate is too fast even with a small amount of the plating solution causes a self-decomposition reaction. The input amount of the reducing agent depends on the target precipitation amount, and plating can be performed by adjusting the target precipitation amount at about 2-15 ml. If the concentration of the reducing agent is concentrated in a short time, the reaction rate is so fast that the self-decomposition reaction is performed. Therefore, the total plating time and the proportion of the reducing agent are determined in proportion thereto, and the amount of the reducing agent determined is uniformly distributed during the plating time. When the nickel ions in the solution are exhausted, the plating reaction does not occur even if the reducing agent is added.

The method of plating nickel on a powder such as CBN using the above plating solution,

After filling the plating liquid except the reducing agent in the plating tank, the powder-type grinding material pretreated by the usual method was added, and the temperature was raised to 60-90 ° C., and then the reducing agent was added at a volume of 0.1-0.3% by volume to the plating solution while stirring. Causing a first plating step (S1);

A second plating step of removing the plating solution after the first plating step (S1) and passing through the first plating step (S2);

After the secondary plating step (S2) step of immersing the powder grinding material in a normal activation solution for 1 to 2 minutes to adsorb Pd ions to the nickel-plated surface layer (S3); And

(S4) using the electroless nickel plating method (Example 1) of completing the powder grinding material to which the Pd ion is adsorbed in the step (S3) through the first plating step (S1), wherein the step (S1) After the powder grinding material is immersed in a normal activation solution for 1 to 2 minutes, it is more preferable to adsorb Pd ions to the nickel plated surface layer. Before the steps (S1) and (S2) is completed, 0.1 to 0.3 ml of the usual activation solution is added to the plating tank to attach the palladium catalyst to the nickel plating layer, and then the step (S4) is performed again (S2). ).

The pretreatment process is similar to the conventional electroless nickel plating process. In other words, SnCl ₂ · 2H ₂ O 5 ~ 30g / ℓ, 36% HCl 5 ~ 30mL / ℓ immersed in a sensitizing solution at 30 ~ 40 ℃ for 20 to 40 minutes and immersed in divalent on the surface of the powder Adsorb tin ions. After washing with water the PdCl ₂ 0.1 ~ 0.3g / ℓ, HCl 1 ~ at 20 ~ 30 ℃ in ekti Renovation solution having a composition of 5㎖ / ℓ stirred for 20 to 40 minutes, by immersion whereby the two electrons from the divalent tin ions After divalent palladium ions change the divalent tin into tetravalent tin ions, only the palladium nuclei are adsorbed on the surface of the powder.

 In the pretreatment method, there is also a method of performing one pretreatment process with a mixture of Pd ions and Sn ions. However, this method does not provide an irregular shape of the plating layer. The pretreatment is performed by using a bastion process.

It is preferable to perform the temperature of the present invention plating method at 60 ~ 90 ℃, below 60 ℃, the plating reaction is significantly reduced, the precipitation amount is reduced, and the plating rate is increased above 90 ℃, but the evaporation amount of the liquid is increased to facilitate the smooth plating process. Can't proceed. In addition, in the first electroless nickel process, the plating reaction rate is drastically reduced below 80 ° C., so the plating operation should be performed at 80 ° C. or higher for the first electroless nickel process. In the case of the 2nd and 3rd electroless nickel process, the plating reaction can be seen at 60 ~ 90 ℃, so the temperature can be selected according to the purpose of plating.

The following shows a typical electroless nickel precipitation reaction mechanism.

^{_{2H 2 PO2 - + 2H 2 O}} 〓» 2HPO 3 - + 4H + + 2H -

Ni ²⁺ + 2H ^- 〓≫ Ni + H ₂

_{^{H 2 PO 2 - + H +}} 〓» P + 2OH - + 1 / 2H 2

The reactor tool of the present invention is also the same, and as shown in the reaction scheme, electroless nickel plating cannot be made without a reducing agent.

Hereinafter, the present invention will be described through an example in which CBN is plated with the above plating solution.

In the present invention, in order to have a plating layer having an irregular shape as much as possible, the same plating solution was used and plating was performed as described above. As a powder material, electroless nickel plating was performed with CBN excellent in the performance as a grinding material.

<Example 1>

A solution Solution B (Reduction Agent) Nickel Sulfate: 20 ~ 150g / L Succinic Acid: 5 ~ 30g / L Ammonia Water (pH Adjustment): pH 4.5 ~ 6.0 Sodium hypophosphite: 100-700 g / L Working temperature: 60 ~ 90 ℃

Example 1 is by the first method as described above by the first and second nickel plating solution with the following composition and then immersed in the palladium catalyst solution to impart a palladium catalyst to the plating layer and then electroless nickel plating again .

After filling the solution A to the working indicator in the plating tank of the composition as described above, put the pre-treated CBN powder and raise the temperature to the working temperature. When the temperature rises, slowly add the solution B while stirring. The initial dose of solution B should be about 0.1 ~ 0.3% of solution A. Make solution B initially 0.1 ~ 0.3%. After adding, stop adding and stop stirring and wait until plating reaction occurs. The plating reaction starts to occur in about 1 to 3 minutes. What is important at this time is that the autolysis reaction occurs when the solution B is added immediately. When the plating reaction becomes violent and slightly weak, the solution B is added in small portions. The amount of precipitation can be adjusted by adding B solution. After the 1st and 2nd electroless nickel plating is finished, the powder is immersed in the activation solution for 1 ~ 2 minutes and adsorbed Pd ion on the nickel plated surface layer. You can get it.

The shape of the plated layer after plating carried out by the above method has a large irregular surface as shown in FIG.

<Example 2>

In Example 2, the activation method was added to the nickel plating layer before the plating was completed in the first and the second nickel plating using the plating solution of the following composition, and then the electroless nickel plating was performed again. will be.

A solution Solution B (Reduction Agent) Nickel Sulfate: 20 ~ 150g / L Succinic Acid: 5 ~ 30g / L Ammonia Water (pH Adjustment): pH 4.5 ~ 6.0 Sodium hypophosphite: 100-700 g / L Working temperature: 60 ~ 90 ℃

Proceed in the same manner as in Example 1, but 5 ~ 10 minutes before the completion of the first and second nickel plating is added 0.1 ~ 0.3ml about the activation solution. It is not effective at 0.1 ml or less, and at 0.3 ml or more, the solution turns black.

 It can be seen that the shape of the plated layer after plating carried out by the method is irregular as shown in FIG.

Comparing FIGS. 1 and 2 with FIG. 3, the difference can be easily found. It can be seen that the shape of the plated layer is much more irregular in FIG. 1 and FIG. 2, which is a photograph after plating according to the present invention than in FIG. 3, which is a case of the conventional method, and thus the surface area is relatively large. This corresponds to the purpose of plating, and it can be seen that the present invention provides an optimal electroless nickel plating solution and plating method for coating powder materials used as grinding materials.

As described above, according to the present invention, the surface area of the powder such as CBN can be maximized by the plating solution and the plating method of the present invention. In other words, the grinding material has a smooth surface layer, but the present invention provides an electroless nickel coating having the most irregular shape on the smooth surface layer to improve the bonding property in a subsequent bonding process between the grinding powder and the grinding wheel having the maximum surface area at a constant volume. We can plan greatly.

In addition, in the case of the grinding material, it is a non-conductor in the form of powder and it does not conduct current, so it is possible to metallize it through electroless plating, which requires the pretreatment of the powder to enable metallization on the surface of the powder. This allows cost savings by entering the electroless nickel plating process immediately after pretreatment.

1: SEM photograph of the powder after plating according to the present invention

2: SEM image of the powder after plating according to another embodiment of the present invention

3: SEM image when plating by the conventional method

4 is a schematic diagram of one embodiment of the present invention.

5 is a schematic diagram of another embodiment of the present invention.

Claims (9)

An electroless nickel plating solution for powder, comprising a plating solution consisting of a nickel salt, a complexing agent, a pH adjusting agent and a pH buffer, and sodium phosphate, a high concentration reducing agent of 100 to 700 g / L, which is added separately. 2. The electroless nickel plating solution of claim 1, wherein the nickel salt is nickel sulfate, the complexing agent is succinic acid, the pH adjusting agent is ammonia water, and the pH buffer is acetic acid. According to claim 2, wherein the concentration of the nickel sulfate is 20 ~ 150g / L, the succinic acid concentration is 5 ~ 50g / L, pH adjustment with the pH regulator is 4.5 ~ 6.5, pH buffer is 3 ~ 20ml Electroless nickel plating solution for powder, characterized by the use of / L. 2. The electroless nickel plating solution for powder according to claim 1, wherein the electroless nickel plating solution for powder further comprises 1 to 3 ppm of lead chloride and / or 1 to 3 ppm of accelerator. 5. The electroless nickel plating solution for powder according to claim 4, wherein the accelerator is sulfide and / or fluoride. A method of plating a powder grinding material with the powder type electroless nickel plating liquid according to any one of claims 1 to 5, After filling the plating liquid except the reducing agent in the plating tank, put the powder grinding material pretreated by the usual method, raise the temperature to 60-90 ° C., and then add the reducing agent at 0.1-0.3% by volume to the plating liquid while stirring to cause the plating reaction. Primary plating to be performed (S1); After the first plating step (S1) to remove the plating solution and the reducing agent after the second plating step (S2) undergoing the first plating step again; After the plating reaction in the step (S2) step of immersing the powder grinding material in a conventional activation solution for 1 to 2 minutes to adsorb Pd ions to the nickel-plated surface layer (S3); And Electroless nickel plating method of the powder grinding material, characterized in that the step (S4) of the powder grinding material adsorbed Pd ion in step (S3) to perform the third step (S1). 7. The electroless nickel plating of the powder grinding material as claimed in claim 6, wherein the step S3 is achieved by adding 0.1 to 0.3 ml of activation solution to the plating tank before the steps S1 and S2 are completed. Way. 8. The electroless nickel plating method of claim 7, wherein the activation solution is added 5 to 10 minutes before the steps (S1) and (S2) are completed. 7. The powder grinding according to claim 6, wherein after the step S1, the powder grinding material is immersed in a normal activation solution for 1 to 2 minutes to adsorb Pd ions to the nickel-plated surface layer, followed by step S2. Electroless nickel plating of materials.