JP2004137533A - Method for manufacturing rare earth system permanent magnet having copper plating film on surface - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a rare earth system permanent magnet having a copper plating film provided with excellent adhesion properties on the surface by using a new electric copper plating solution. <P>SOLUTION: The copper plating film is formed directly or through another metal plating film on the surface of a rare earth system permanent magnet by electric copper plating treatment using the plating solution which contains 0.03 to 0.5 mol/L copper sulfate, 0.05 to 0.7 mol/L ethylenediaminetetraacetic acid, 0.02 to 1.0 mol/L sodium sulfate, and 0.1 to 1.0 mol/L at least one kind selected from tartrate and citrate and pH of which is adjusted to 11.0 to 13.0. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a rare-earth permanent magnet having a copper plating film having excellent adhesion on the surface using a novel plating solution for electrolytic copper plating.
[0002]
[Prior art]
Rare earth permanent magnets such as R-Fe-B permanent magnets represented by Nd-Fe-B permanent magnets and R-Fe-N permanent magnets represented by Sm-Fe-N permanent magnets are resources. In particular, R-Fe-B-based permanent magnets are used in various fields today because they are made of abundant and inexpensive materials and have high magnetic properties.
However, since rare-earth permanent magnets contain highly reactive rare-earth elements: R, they are easily oxidized and corroded in the air, and when used without any surface treatment, a slight amount of acid, alkali, moisture, etc. Corrosion progresses from the surface due to the presence of rust and rust is generated, which leads to deterioration and variation in magnet characteristics. Further, when the rusted magnet is incorporated into a device such as a magnetic circuit, the rust may scatter and contaminate peripheral components.
In view of the above, formation of a copper plating film, which is a corrosion-resistant film, on the surface of a rare-earth permanent magnet has been conventionally performed. In addition to having excellent corrosion resistance, the copper plating film has characteristics such as excellent turning property with the film and excellent adhesion to an organic adhesive.
Generally, a method of forming a copper plating film is roughly classified into an electrolytic copper plating process and an electroless copper plating process, but when forming a copper plating film on the surface of a rare earth permanent magnet by the electroless copper plating process, R and Fe, which are constituent metals of the magnet, elute into the plating solution and react with the reducing agent contained in the plating solution, and the formation of a copper plating film on the surface of the R and Fe eluted into the plating solution proceeds. It is important to control the plating solution to prevent such a problem. However, this is not always easy. Further, a plating solution for electroless copper plating is generally expensive. Therefore, when a copper plating film is formed on the surface of a rare-earth permanent magnet, a simple and low-cost electrolytic copper plating process is usually adopted.
When a copper plating film is formed on the surface of a rare earth permanent magnet by electrolytic copper plating, it is desirable that the plating solution used is alkaline in view of the strong corrosiveness of the rare earth permanent magnet under acidic conditions. Heretofore, plating solutions containing copper cyanide (copper cyanide bath) have been widely used. However, although the copper cyanide bath is excellent in the properties of the copper plating film to be formed and easy to control the plating solution, it has high utility value, but ignores the effect on the environment because it contains highly toxic cyanide. I can't. Therefore, in recent years, plating solutions containing copper pyrophosphate (copper pyrophosphate bath) are often used in place of copper cyanide bath. However, copper pyrophosphate bath contains a lot of free copper ions in the bath. When attempting to form a copper plating film directly on the surface of a rare earth permanent magnet using a copper pyrophosphate bath, a copper plating film with excellent adhesion is formed due to factors such as displacement plating reaction occurring on the magnet surface. There is a problem that you can not. Further, even when a copper plating film is formed on the surface of the rare-earth permanent magnet via another metal plating film, a phenomenon that the magnetic properties of the magnet deteriorate is caused.
In view of the above, the present inventors have conducted various studies in order to develop a new method for forming a copper plating film having excellent adhesion on the surface of a rare earth permanent magnet by electrolytic copper plating. , Focused on a plating solution containing copper sulfate and ethylenediaminetetraacetic acid. As a plating solution containing copper sulfate and ethylenediaminetetraacetic acid, various plating solutions are known as plating solutions for electroless copper plating. However, as a plating solution for electrolytic copper plating, a plating solution containing copper sulfate, ethylenediaminetetraacetic acid, glycine, and potassium chloride has been proposed in the following Non-Patent Document 1, but this plating solution contains chloride ions. Therefore, when a copper plating film is formed on the surface of a highly corrosive rare earth permanent magnet, it is difficult to apply.
[0003]
[Non-patent document 1]
Ministry of Internal Affairs and Communications of Ministry of Health, Mizumoto and four others, “Electro-copper plating from EDTA complex bath and its film properties”, Surface Technology, 1990 (separate volume), Vol. 41, No. 2, p156-160.
[0004]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a method for producing a rare earth permanent magnet having a copper plating film having excellent adhesion on the surface using a novel plating solution for electrolytic copper plating.
[0005]
[Means for Solving the Problems]
The present inventors have made repeated studies in view of the above points, and as a result, have adjusted copper sulfate, ethylenediaminetetraacetic acid, sodium sulfate, tartrate or citrate to a predetermined composition, and adjusted the pH to a predetermined range. It has been found that when the plating solution thus prepared is used, a copper plating film having excellent adhesion can be formed on the surface of the rare earth permanent magnet by electrolytic copper plating.
[0006]
The present invention has been made based on the above findings, and a method for producing a rare earth permanent magnet having a copper plating film on the surface thereof according to the present invention is as follows: 0.03 mol / L of copper sulfate. At least one selected from the group consisting of tartrate and citrate; 0.05 mol / L to 0.7 mol / L of ethylenediaminetetraacetic acid; 0.02 mol / L to 1.0 mol / L of sodium sulfate; Or 0.1 mol / L to 1.0 mol / L, and directly or on the surface of the rare earth permanent magnet by electrolytic copper plating using a plating solution having a pH adjusted to 11.0 to 13.0. A copper plating film is formed via another metal plating film.
A manufacturing method according to a second aspect is characterized in that, in the manufacturing method according to the first aspect, a copper plating film is directly formed on a surface of the rare-earth permanent magnet.
The manufacturing method according to a third aspect is characterized in that, in the manufacturing method according to the first aspect, a copper plating film is formed on the surface of the rare-earth permanent magnet via another metal plating film.
A manufacturing method according to a fourth aspect is characterized in that, in the manufacturing method according to the third aspect, a copper plating film is formed after a surface treatment of another metal plating film with an organic carboxylic acid-containing aqueous solution.
Further, a manufacturing method according to a fifth aspect is characterized in that, in the manufacturing method according to the fourth aspect, the organic carboxylic acid is oxalic acid.
Further, the production method according to claim 6 is characterized in that in the production method according to claim 4, the organic carboxylic acid concentration of the organic carboxylic acid-containing aqueous solution is 0.002 mol / L or more.
A manufacturing method according to a seventh aspect is characterized in that, in the manufacturing method according to the third aspect, the other metal plating film is a nickel plating film.
In the manufacturing method according to the eighth aspect, in the manufacturing method according to the seventh aspect, the nickel plating film is formed by electro nickel plating using a plating solution whose pH is adjusted to 6.0 to 8.0. It is characterized in that it is.
Further, the plating solution for electrolytic copper plating of the present invention, as described in claim 9, is 0.03 mol / L to 0.5 mol / L of copper sulfate and 0.05 mol / L to 0.7 mol / L of ethylenediaminetetraacetic acid. L, 0.02 mol / L to 1.0 mol / L of sodium sulfate, 0.1 mol / L to 1.0 mol / L of at least one selected from tartrate and citrate, and pH of 11.0 to It is characterized by being adjusted to 13.0.
Further, the rare earth permanent magnet having a copper plating film on the surface according to the present invention is manufactured by the manufacturing method according to claim 1 as described in claim 10.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
The method for producing a rare earth permanent magnet having a copper plating film on its surface according to the present invention includes a copper sulfate of 0.03 mol / L to 0.5 mol / L, an ethylenediaminetetraacetic acid of 0.05 mol / L to 0.7 mol / L, Sodium sulfate is contained at 0.02 mol / L to 1.0 mol / L, and at least one selected from tartrate and citrate is contained at 0.1 mol / L to 1.0 mol / L, and the pH is 11.0 to 13. It is characterized in that a copper plating film is formed on the surface of the rare-earth permanent magnet directly or via another metal plating film by electrolytic copper plating using a plating solution adjusted to zero.
[0008]
In the plating solution for electrolytic copper plating of the present invention, the content of copper sulfate is defined as 0.03 mol / L to 0.5 mol / L. If the concentration is less than 0.03 mol / L, the copper deposition efficiency may be deteriorated. On the other hand, if it exceeds 0.5 mol / L, copper sulfate tends to precipitate, and copper sulfate may be mixed into the copper plating film formed on the surface of the rare earth permanent magnet.
[0009]
Further, the content of ethylenediaminetetraacetic acid is defined as 0.05 mol / L to 0.7 mol / L. When the concentration is less than 0.05 mol / L, free copper ions in the plating solution cannot be sufficiently complexed, and On the other hand, if it is more than 0.7 mol / L, ethylenediaminetetraacetic acid may not be easily dissolved in the plating solution, or the copper plating film to be formed may have unevenness. is there.
[0010]
Further, the content of sodium sulfate is defined as 0.02 mol / L to 1.0 mol / L. When the concentration is less than 0.02 mol / L, the conductivity of the plating solution is reduced, and the copper deposition efficiency may be deteriorated. On the other hand, if it exceeds 1.0 mol / L, the formed copper plating film may be likely to be uneven in formation.
[0011]
In the plating solution for electrolytic copper plating of the present invention, the tartrate or the citrate exhibits an effect of effectively suppressing the passivation of the anode under alkaline conditions and promoting the elution of copper from the anode. Examples of the tartrate include a sodium salt, a potassium salt, and a sodium potassium salt. Examples of the citrate include a sodium salt and an ammonium salt. When the content is defined as 0.1 mol / L to 1.0 mol / L, the effect may not be sufficiently exerted if the concentration is less than 0.1 mol / L, whereas if the concentration is more than 1.0 mol / L, the cathode may be used. This is because the current efficiency may be reduced and the copper deposition efficiency may be deteriorated.
[0012]
The reason why the pH of the plating solution for electrolytic copper plating treatment of the present invention is specified to be 11.0 to 13.0 is to mainly consider the strong corrosiveness of a rare earth permanent magnet under acidic conditions. If it is less than 0, ethylenediaminetetraacetic acid cannot sufficiently form a complex with free copper ions in the plating solution having the above composition, and as a result, a copper plating film is not formed on the surface of the rare earth permanent magnet and a black cuprous oxide film is formed. On the other hand, if it exceeds 13.0, passivation of the anode may not be sufficiently suppressed. In adjusting the pH, sodium hydroxide or the like may be used.
[0013]
If necessary, a complexing agent such as monoethanolamine, diethanolamine, triethanolamine, glycine, 2,2-pipyridine, orthophenanthronine, or polyethylene glycol is added to the plating solution for electrolytic copper plating of the present invention. May be. If such a complexing agent is added, even if free monovalent copper ions are formed in the plating solution, the complexing agent forms a complex with the complexing agent, so that the displacement plating reaction due to the presence of free monovalent copper ions is suppressed. It is possible to effectively prevent a copper plating film having poor adhesion from being formed on the surface of the rare earth permanent magnet.
[0014]
When a copper plating film is formed directly on the surface of a rare earth permanent magnet using the plating solution for electrolytic copper plating of the present invention, the formed copper plating film has excellent adhesion to the surface of the magnet. .
[0015]
The copper plating film formed using the plating solution for electrolytic copper plating of the present invention may be formed on the surface of the rare-earth permanent magnet via another metal plating film such as a nickel plating film.
[0016]
For example, when a copper plating film is formed on the surface of a rare-earth permanent magnet via a nickel plating film, it is desirable that the nickel plating film be surface-treated with an organic carboxylic acid-containing aqueous solution before the copper plating film is formed. By performing such a treatment, peeling of the copper plating film from the nickel plating film due to poor adhesion between the nickel plating film and the copper plating film can be effectively prevented.
[0017]
The organic carboxylic acid-containing aqueous solution functions as an etching solution for the nickel plating film, removes the deteriorated layer formed on the surface, activates the surface, activates the surface, and removes the copper plating film formed on the surface. Contributes to the improvement of adhesion. For the purpose of etching the surface of the nickel plating film, it is not impossible to use an aqueous solution containing an inorganic acid such as hydrochloric acid, sulfuric acid or nitric acid. However, when an aqueous solution containing an inorganic acid is used, highly corrosive inorganic ions such as chloride ions (Cl ⁻ ), sulfate ions (SO ₄ ²⁻ ), and nitrate ions (NO ₃ ⁻ ) remain on the surface of the nickel plating film. This may cause corrosion of the nickel plating film and the copper plating film formed on the surface thereof. Further, when forming a copper plating film, inorganic ions may affect the properties of the plating solution near the surface of the nickel plating film, and may hinder the formation of a copper plating film having excellent adhesion. Since organic carboxylic acids are mild acids compared to inorganic acids, using an organic carboxylic acid-containing aqueous solution does not cause excessive etching as in the case of using an inorganic acid-containing aqueous solution, and moderate etching can be performed. As a result, only the deteriorated layer can be etched, and the above problems can be reduced.
[0018]
The above effects can be obtained by nickel electroplating using a plating solution whose pH has been adjusted to 6.0 to 8.0 (for example, a plating solution described in JP-A-6-13218). Particularly effective for plating films. The nickel plating film formed by electro-nickel plating using such a neutral plating bath easily forms a deteriorated layer made of nickel hydroxide or nickel oxide on the surface, and is formed on the surface. The present inventors have found that the poor adhesion to the copper plating film is caused by the presence of such an altered layer. Therefore, by treating the surface of the nickel plating film formed under the above forming conditions with an organic carboxylic acid-containing aqueous solution, it is possible to improve the adhesion with the copper plating film formed on the surface. It is considered that this is because the altered surface composed of such nickel hydroxide or nickel oxide is removed from the surface of the nickel plating film to activate the surface.
[0019]
Examples of the organic carboxylic acid include oxalic acid, tartaric acid, citric acid, succinic acid, malic acid, malonic acid, and the like.Because oxalic acid has an appropriate etching rate for a nickel plating film, It can be said that it is a suitable organic carboxylic acid. The organic carboxylic acid concentration of the organic carboxylic acid-containing aqueous solution is desirably 0.002 mol / L or more. If the concentration is lower than 0.002 mol / L, a sufficient effect may not be obtained. Since oxalic acid is a water-soluble solid substance, the upper limit of the concentration in an aqueous solution is the concentration in a saturated aqueous solution.
[0020]
The pH of the organic carboxylic acid-containing aqueous solution is desirably 1 or more from the viewpoint of preventing excessive etching. In addition, in order to obtain a sufficient effect, it is preferably 5 or less, more preferably 3 or less (since the dissolution lower limit pH of nickel is 3.5, it is more acidic than the pH. Because it is preferred).
[0021]
The surface treatment of the nickel plating film using the organic carboxylic acid-containing aqueous solution is performed by using a rare earth permanent magnet having a nickel plating film subjected to a normal cleaning treatment on the surface, for example, an organic carboxylic acid adjusted to 20 ° C to 40 ° C. What is necessary is just to immerse in a containing aqueous solution for 60 to 240 seconds. When the temperature of the organic carboxylic acid-containing aqueous solution is set to 20 ° C. to 40 ° C., if the temperature is lower than 20 ° C., a sufficient effect may not be obtained. A large amount of etching components are mixed into the acid-containing aqueous solution to accelerate the deterioration of the organic carboxylic acid-containing aqueous solution, or the mixed components adhere to the surface of the nickel plating film, thereby forming a copper plating film having excellent adhesion on the surface. This is because there is a risk of inhibiting formation. After the surface treatment as described above, it is desirable to perform ultrasonic cleaning in order to remove the organic carboxylic acid remaining on the surface of the nickel plating film.
[0022]
The copper electroplating treatment using the plating solution in the present invention can be carried out by a conventional copper electroplating, whether the copper plating film is formed directly on the surface of the rare earth permanent magnet or through another metal plating film. The treatment may be performed in accordance with the conditions of the treatment. From the viewpoint of ensuring good workability, the treatment temperature (liquid temperature) is 30 ° C to 70 ° C, preferably 40 ° C to 60 ° C, and the treatment time is 30 minutes to 300 ° C. Minutes. The thickness of the copper plating film is not particularly limited, but is preferably 1 μm or more, more preferably 3 μm or more in order to sufficiently exhibit the function as a corrosion-resistant film. On the other hand, in order to secure an effective volume of the rare-earth permanent magnet, when it is formed directly on the surface of the magnet, it is preferably 50 μm or less, more preferably 30 μm or less. When the magnet is formed on the surface of the magnet via another metal plating film, the thickness is preferably 30 μm or less, more preferably 20 μm or less.
[0023]
In addition, by adding a metal plating film, a resin film, a chemical conversion coating film, and the like on the surface of the copper plating film formed by the electrolytic copper plating process using the plating solution in the present invention, it is possible to further impart corrosion resistance and functionality. May be provided.
[0024]
The rare earth metal-based permanent magnets, for example, R-Co based permanent magnet, R-Fe-B based permanent magnet, etc. R-Fe-N based permanent magnet, the maximum magnetic energy product of 80 kJ / ^{m 3} or more magnetic properties Known rare earth permanent magnets. Among them, R-Fe-B-based permanent magnets are desirable, as described above, in that they have particularly high magnetic properties, are excellent in mass productivity and economical efficiency, and have excellent adhesion to a coating film. . The rare earth element (R) in these rare earth permanent magnets is at least one of Nd, Pr, Dy, Ho, Tb, and Sm, or further, La, Ce, Gd, Er, Eu, Tm, Yb, Lu, Those containing at least one of Y are desirable.
Normally, one kind of R is sufficient, but in practice, a mixture of two or more kinds (such as misch metal or dymium) can be used for convenience and other reasons.
Further, by adding at least one of Al, Ti, V, Cr, Mn, Bi, Nb, Ta, Mo, W, Sb, Ge, Sn, Zr, Ni, Si, Zn, Hf and Ga, It is possible to improve the coercive force and the squareness of the demagnetization curve, improve the manufacturability, and reduce the cost. Further, by replacing a part of Fe with Co, the temperature characteristics can be improved without impairing the magnetic characteristics of the magnet obtained.
[0025]
【Example】
The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention should not be construed as being limited to the following description.
[0026]
As starting materials, electrolytic iron, ferroboron, and Nd as R are blended in a required magnet composition, melt-cast, coarsely ground by a mechanical grinding method, and then finely ground to obtain a fine powder having a particle size of 3 μm to 10 μm. After being molded in a magnetic field of 10 kOe and sintering at 1100 ° C. × 1 hour in an argon atmosphere, the obtained sintered body is subjected to an aging treatment at 600 ° C. × 2 hours. , 15Nd-7B-78Fe. A test piece A having a size of 3 mm × 20 mm × 40 mm and a test piece B having a size of 1 mm × 1.5 mm × 2 mm were cut out from the magnet body, surface-activated with a 0.1 mol / L nitric acid solution, and then washed with water. For the following experiment.
[0027]
Example 1
Contains 0.1 mol / L of copper sulfate pentahydrate, 0.16 mol / L of ethylenediaminetetraacetic acid disodium salt, 0.4 mol / L of sodium sulfate, and 0.2 mol / L of disodium tartrate, and is adjusted to pH with sodium hydroxide. Using a copper plating solution adjusted to 12.3, electrolytic copper plating was performed for 200 minutes at a solution temperature of 50 ° C. and a cathode current density of 0.2 A / dm ² , and copper was applied to the surfaces of the test pieces A and B. A plating film was formed. When the film thickness of the copper plating film was measured for the test sample A, 10 samples having the copper plating film on the surface, the average value was 15 μm. In addition, when an adhesion test was performed on a test sample A, 10 samples having a copper plating film on the surface thereof, which was peeled off with a tape after cross-cutting in accordance with JIS (K5400), the copper plating film was peeled from the test piece. No sample was present. When the magnetic properties of the test pieces B and 10 samples each having a copper plating film on the surface were evaluated, the average value was 0.98 iHc / Hk, which was excellent.
[0028]
Comparative Example 1:
A copper plating solution containing 0.2 mol / L of copper pyrophosphate, 1.1 mol / L of potassium pyrophosphate, and 0.1 mol / L of potassium nitrate and adjusted to pH 8.5 with aqueous ammonia was used. An electrolytic copper plating process was performed at a cathode current density of 0.2 A / dm ² for 60 minutes to form a copper plating film on the surfaces of the test pieces A and B, but no copper plating film was formed on the entire surface. (Therefore, the thickness of the copper plating film was not measured). When an adhesion test similar to that of Example 1 was performed on the 10 test pieces A and 10 samples, the copper plating film partially formed on the surface of the test piece was found to be in all samples. Peeled off.
[0029]
Example 2:
It contains 0.5 mol / L of nickel sulfate hexahydrate, 0.1 mol / L of diammonium citrate, 0.2 mol / L of boric acid, 0.15 mol / L of ammonium chloride, and 0.5 mol / L of saccharin. Using a nickel plating solution whose pH was adjusted to 6.8 with a nickel plating solution at a solution temperature of 50 ° C. and a cathode current density of 0.25 A / dm ² for 15 minutes, the surfaces of the test pieces A and B were Then, a nickel plating film was formed. When the film thickness of the nickel plating film was measured for 10 samples of the test piece A having the nickel plating film on the surface, the average value was 1 μm. The test piece A and the test piece B having the nickel plating film on the surface were immersed in an aqueous solution (pH 1.5) containing 0.033 mol / L of oxalic acid at a liquid temperature of 30 ° C. for 2 minutes to perform the surface treatment of the nickel plating film. After ultrasonic cleaning with ion-exchanged water for 2 minutes from the above, using the copper plating solution described in Example 1, electrolytic copper plating treatment was performed at a solution temperature of 50 ° C. and a negative current density of 0.2 A / dm ² for 60 minutes. Then, a copper plating film was formed on the surface of the nickel plating film. When the thickness of the copper plating film was measured on 10 samples and the test piece A having the copper plating film on the surface via the nickel plating film, the average value was 5 μm. When an adhesion test similar to that of Example 1 was performed on 10 samples A and samples having a copper plating film on the surface via the nickel plating film, there was a sample in which the copper plating film was separated from the nickel plating film. Did not. When the magnetic characteristics of the sample B, 10 samples having a copper plating film on the surface via the nickel plating film were evaluated, the average value was 0.95 iHc / Hk, which was excellent.
[0030]
Comparative Example 2:
Using the nickel plating solution described in Example 2, an electro-nickel plating treatment was performed under the same conditions, and a nickel plating film was formed on the surfaces of the test pieces A and B. After performing the same surface treatment as in Example 2 on the nickel plating films formed on the surfaces of the test piece A and the test piece B, the copper plating solution described in Comparative Example 1 was used, and the same conditions were applied. Copper plating was performed to form a copper plating film on the surface of the nickel plating film. When the thickness of the copper plating film was measured on 10 samples and the test piece A having the copper plating film on the surface via the nickel plating film, the average value was 5 μm. When an adhesion test similar to that of Example 1 was performed on the test samples A and 10 samples having a copper plating film on the surface via the nickel plating film, the copper plating film was peeled off from the nickel plating film in one sample. . When the magnetic properties of the sample B and the 10 samples having the copper plating film on the surface via the nickel plating film were evaluated, the average value was 0.71 iHc / Hk, and the deterioration of the magnetic characteristics was remarkable.
[0031]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the rare earth permanent magnet which has the copper plating film excellent in adhesiveness on the surface using the novel plating solution for electrolytic copper plating processing is provided.

Claims (10)

A method for producing a rare earth permanent magnet having a copper plating film on its surface, comprising 0.03 mol / L to 0.5 mol / L of copper sulfate, 0.05 mol / L to 0.7 mol / L of ethylenediaminetetraacetic acid, sulfuric acid It contains 0.02 mol / L to 1.0 mol / L of sodium, 0.1 mol / L to 1.0 mol / L of at least one selected from tartrate and citrate, and has a pH of 11.0 to 13.0. A copper plating film is formed on the surface of a rare-earth permanent magnet directly or via another metal plating film by an electrolytic copper plating process using a plating solution adjusted to the above. 2. The method according to claim 1, wherein a copper plating film is formed directly on the surface of the rare earth permanent magnet. 2. The method according to claim 1, wherein a copper plating film is formed on the surface of the rare earth permanent magnet via another metal plating film. The method according to claim 3, wherein the copper plating film is formed after the surface treatment of another metal plating film with an aqueous solution containing an organic carboxylic acid. The method according to claim 4, wherein the organic carboxylic acid is oxalic acid. The method according to claim 4, wherein the organic carboxylic acid-containing aqueous solution has an organic carboxylic acid concentration of 0.002 mol / L or more. 4. The method according to claim 3, wherein the other metal plating film is a nickel plating film. 8. The method according to claim 7, wherein the nickel plating film is formed by electro-nickel plating using a plating solution having a pH adjusted to 6.0 to 8.0. 0.03 mol / L to 0.5 mol / L of copper sulfate, 0.05 mol / L to 0.7 mol / L of ethylenediaminetetraacetic acid, 0.02 mol / L to 1.0 mol / L of sodium sulfate, tartrate and citric acid A plating solution for electrolytic copper plating, wherein the plating solution contains at least one selected from acid salts in an amount of 0.1 mol / L to 1.0 mol / L and has a pH adjusted to 11.0 to 13.0. A rare earth permanent magnet having a copper plating film on the surface, which is manufactured by the manufacturing method according to claim 1.