KR100693902B1 - A double nickel plating method of a permanent magnet with Nd-Fe-B - Google Patents

Abstract

 The present invention relates to a double nickel plating to improve the adhesion and corrosion resistance of Nd-Fe-B-based sintered magnet and the nickel plating layer and to improve the uniform electrodeposition using pulse plating, and the present invention also relates to harmful effects such as nitric acid and hexavalent chromium. The purpose of the present invention is to provide a highly corrosion-resistant Nd-Fe-B permanent magnet by using an environmentally friendly etching agent and a post-treatment agent without materials, and is composed of the surface cleaning, immersion degreasing, etching, desmuting and stabilization processes of the permanent magnet. Pretreatment step (S1);

Forming a double nickel plated layer for performing secondary gloss nickel plating after the first semi-gloss nickel plating after the pretreatment step (S1) (S2); And

After the step (S2) double nickel layer of the Nd-Fe-B-based permanent magnet, characterized in that it comprises a post-treatment step (S3) to form a surface layer to prevent oxidation of the plated nickel layer and improve the corrosion resistance The object is achieved by providing a plating method.

Nd-Fe-B, Permanent Magnet, Plating, Electroplating, Nickel Plating, Etching Agent

Description

A double nickel plating method of a permanent magnet with Nd-Fe-B}

1 is a double nickel plated cross section on an Nd-Fe-B permanent magnet.

Figure 2 is a flow chart of the double nickel plating method of Nd-Fe-B-based permanent magnet

The present invention ultimately relates to a double nickel plating method of Nd-Fe-B-based permanent magnets, and more particularly, to remove the use of nitric acid and hexavalent chromium in the etching process and the post-treatment process during the nickel plating process. The present invention relates to a method for providing a double nickel plated Nd-Fe-B permanent magnet.

In general, Nd-Fe-B-based permanent magnets contain a lot of active Nd and Fe, and are easily corroded by oxidation in the atmosphere. Therefore, in order to solve these problems, a method of forming various protective layers on the surface has been proposed, and the protective layer is coated with a metal or resin layer alone or in combination, but the method of forming the film is electroplating with wet plating. Various methods, such as dry plating, deposition coating, hot dip coating, electrodeposition coating, such as sputtering, ion plating, and vacuum deposition, are used. Among them, wet plating such as electroplating is used most frequently because of excellent mass productivity and cost.

In the case of plating by a vacuum deposition method, the surface oxide layer may be removed by introducing an inert gas such as Ar into the vacuum evaporator and sputtering under high pressure. In addition, in order to increase adhesion, an ion plating method of ionizing and depositing evaporation materials is used. However, this method has to be installed in addition to the power supply for applying high pressure to the substrate, there is a problem that the productivity is low because there is a problem such as a complicated process and a long overall coating time.

In addition, the coating for improving the corrosion resistance of the Nd-Fe-B-based magnet has a method of plating the resin, but this has a weakness such as a poor surface appearance and a weakening of the magnetic properties if not plated thinly. In addition, vacuum deposition or ion plating may be performed on aluminum, but the adhesion and uniform electrodeposition are inferior, respectively, and the process conditions are complicated and the device price is high.

In particular, in the case of Nd-Fe-B magnets, the oxide layer of Fe is considered to be a major factor that lowers the adhesion at the time of plating. Ni, which is considered to have excellent adhesion to iron oxides, has excellent problems in adhesion but when the thickness of the coating becomes thick, there is a problem in that the stress of the coating increases, so that cracks occur and the corrosion resistance is lowered. In addition, in the case of general electro-nickel plating, there is a problem in uniform electrodeposition property such as poor plating on the inside of the hole when the sample has a complicated shape. In order to solve this problem, electroplating using pulse rectification is performed. The use of such a pulse rectifier has the advantage of reducing the thickness variation than a general DC rectifier.

Most of electroplating is nickel multi-coating followed by nickel-copper-nickel or semi-gloss nickel-electroless nickel-gloss nickel. It is difficult to control the process because it includes a number of different plating process and can be said to be a disadvantage in terms of cost. In addition, pretreatment of Nd-Fe-B-based permanent magnets is performed before electroplating. The solution used in the etching process, which is the most important in the pretreatment, contains a large amount of nitric acid, which generates nitrogen, which is a plant wastewater regulation substance. This increase leads to economic losses. After plating, chromate process and water proofing treatment are performed to give additional corrosion resistance. However, in the chromate process, hexavalent chromium, which is a hazardous substance, is generated, which makes it difficult to treat wastewater. In addition, corrosion resistance is improved when the water-proof rust treatment is performed, but the solderability is lowered, so that the utilization of the Nd-Fe-B permanent magnet as an electronic component is reduced. That is, in the post-treatment process, it is essential to develop a chemical that satisfies both solderability and corrosion resistance.

The present invention provides an Nd-Fe-B-based magnet having excellent adhesion and corrosion resistance only by double nickel plating without performing various plating processes to solve various problems of the prior art as described above, and etching during the pretreatment process ( Etching) Eliminates the use of nitric acid in the process to minimize environmental pollution. Also, paraffin-based water cutting that impairs the solderability of the nickel layer and the chromate process using hexavalent chromium, which is an environmentally harmful substance during the post-treatment process. Its purpose is to provide a double nickel plating method to cope with environmental problems and to provide high corrosion resistance Nd-Fe-B permanent magnets by excluding antirust treatment process.

The present invention to achieve the above object; Performing a pretreatment to remove the oxide layer on the surface of the Nd-Fe-B-based permanent magnet to improve adhesion with the nickel plating layer (S1);

Double nickel of Nd-Fe-B-based permanent magnet, consisting of a plating step (S2) for plating nickel after the pretreatment step (S1) and a post-treatment step (S3) after the plating step (S2). Provide a plating method.

The overall process of the present invention will be described in detail by dividing into a pretreatment process, a plating process, and a post-treatment process.

The pretreatment step (S1) above is a very important step to remove the oxide layer generated on the surface of the Nd-Fe-B permanent magnet and to improve the adhesion with the nickel plated layer before performing nickel electroplating. . First, degreasing is performed here. After removing stains and foreign substances on the surface, and then rinsed with DI water, the etching process is performed. In general, in the case of a conventional etchant, nitric acid was added as a main component thereof. However, from January 1, 2004, a total amount regulation law regulating nitrogen and phosphorus in plant wastewater was implemented, excluding nitric acid, which is the main component of the etchant, and in the present invention, ethanol, acetic acid, glacial, and lactic acid acid), hydrogen peroxide, etc. After etching, washing with pure water is followed by an ultrasonic desmut process to remove foreign substances remaining on the surface. After washing with pure water again, a stabilization process is performed. After the stabilization process, the water is washed with pure water and then moved to the plating process.

The etchant in the above is used by including all of ethanol, glacial acetic acid, lactic acid, hydrogen peroxide, depending on the state of the sintered Nd-based permanent magnet, ethanol (100 ~ 500mL / L), lactic acid (30 ~ 100mL / L), Glacial acetic acid (60-120 ml / l) and hydrogen peroxide (20-100 ml / l) are mixed and used as an etchant.

In the plating process step (S2), the separation is performed by primary semi-gloss nickel plating and secondary gloss nickel plating. Here, it is preferable that primary semi-gloss nickel uses nickel sulfate as a nickel source, and secondary gloss nickel uses nickel phamparate. The plating thickness is 5 to 10 µm for primary semi-gloss nickel and 10 to 15 µm for secondary gloss nickel plating to provide a high corrosion resistant Nd-Fe-B permanent magnet. In addition, it is preferable to use a pulse rectifier to reduce the thickness variation of the low current portion and the high current portion according to the shape of the magnet. Plating with pulse rectifier can reduce the plating thickness variation by 30 ~ 35% on average compared to general DC rectifier. The maximum current decreased by 40% and the low current decreased by 10%. The average plating thickness is reduced because the thickness is greatly reduced in the high current portion where the plating thickness is thick. Therefore, plating time is increased by about 20 ~ 30% than general DC rectifier. Between the first semi-gloss nickel plating process and the second gloss nickel plating process, a 10% sulfuric acid dipping process and a washing process are generally included. After the second polished nickel plating, washed with pure water and then moved to the post-treatment process.

Condition Primary semi-gloss nickel Second semi-gloss nickel Working temperature (℃) 45-55 45-55 Working minutes 40-60 60-90 Current density (A / dm ² ) 1 to 3 1.5 ~ 3

The primary nickel plating is semi-gloss nickel plating using nickel sulfate and nickel chloride as the nickel salt. In addition, boric acid and semi-gloss-1 and semi-gloss-2 are mixed with additives to form one plating solution. Secondary nickel plating is polished nickel plating, and nickel sulfamate and nickel chloride are used as nickel salts. In addition, the polisher-1 and the polisher-2 are mixed with boric acid and an additive to complete one plating solution. In addition, the anti-pitching agent is added to the primary and secondary nickel plating solutions to understand the anti-pitching of the plating layer. The plating conditions of the primary and secondary plating solutions are shown in the table above.

Low currents (1 A / dm ² or less) take too long plating time and reduce working efficiency. In case of high current (3A / dm ² or more), the plating time is shortened but the uniform electrodeposition of the product is reduced.)

In the post-treatment process step (S3), the conventional technique has improved the corrosion resistance of nickel-plated permanent magnets through the chromate process containing hexavalent chromium and paraffin-based water rust prevention treatment, but in the present invention After eliminating the post-treatment process, OSP (Organic solderability preservatives) process was developed and used as a post-treatment process to satisfy both corrosion resistance and solderability. Therefore, the post-treatment chemical in the post-treatment process of the present invention uses a benzoimidazole and a nickel atom as the main component, so that a nickel atom and a substituted benzoimidazole (Benzoimidazole) layer on the surface of the electroplating nickel layer to form a layer Corrosion resistance is improved by preventing oxidation of the nickel layer. Finally, the process is completed by washing with water in 50 ~ 60 ℃ pure water and drying.

In general, the OSP process is a surface treatment that protects the surface from oxidation and improves solderability of the copper circuit without affecting the gold circuit in an electronic component such as a printed circuit board (PCB) having both a copper circuit and a gold circuit. One way. The OSP process of the present invention is applied to the nickel plating layer rather than the copper layer, and may be similar to the mechanism applied to the copper layer. For the aftertreatment OSP chemicals developed in the present invention, formic acid (40 to 45 wt%) and benzoimidazole (5 to 10 wt%) are the main components, and nickel of 30 ppm or less is preferably added and the working temperature (40 to 50 ° C.), Working time (100-150 seconds) is preferred.

Hereinafter, specific features of the present invention will be described through examples. The plating thickness represents the average thickness, and during electroplating, the rectifier was plated using a pulse rectifier.

<Example>

After the sintered Nd-Fe-B permanent magnet was subjected to a pretreatment process using the etchant developed in the present invention, the primary nickel sulfate plating (7 μm) and the secondary nickel sulfamate plating (13 μm) presented in the present invention were carried out. Plating). And finished with the OSP process, a post-treatment process developed in the present invention.

Comparative Example 1

 Unlike Example, the pretreatment is performed using an etchant including nitric acid and other additives according to TDS (Technical Data Sheet) provided by other companies. Double nickel plating proceeds in the same conditions as in [Example]. The post-treatment process is conventionally finished by chromate treatment followed by paraffin water rust prevention treatment.

Comparative Example 2

The pretreatment step is carried out under the same conditions as in [Example]. In the plating process, primary nickel sulfate plating (5 μm) is performed followed by secondary copper cyanide plating (5 μm). Thereafter, nickel plating is performed in the third step to finish nickel plating (10 µm), thereby completing the plating process. The post-treatment step is carried out under the same conditions as in [Example].

Comparative Example 3

The pretreatment step is carried out under the same conditions as in [Example]. The plating process proceeds to primary nickel sulfate plating (5 mu m), secondary electroless nickel plating (5 mu m), and tertiary nickel sulfate plating (10 mu m). The post-treatment step is carried out under the same conditions as in [Example].

[Table 1] is a product obtained through the [Example] and [Comparative Example] to confirm the performance of the product through the salt spray test and PCT (Pressure cooking test) test.

Salt spray test PCT After 72 hours 96 hours later After 72 hours 96 hours later Example No change No change No change Bulging corners Comparative Example 1 No change Fine rusting of low current part No change Bulging corners Comparative Example 2 Rust in general - Bulging corners - Comparative Example 3 No change Fine rusting of low current part No change Bulging corners

As described in detail above, it is possible to eliminate the existing process of etching using nitric acid in the pretreatment process and to reduce the occurrence of environmental pollutants and reduce the waste water treatment cost by using the etching agent whose main components are ethanol, glacial acetic acid, lactic acid, and hydrogen peroxide. have.

In addition, by reducing the complex plating process such as nickel-copper-nickel, electrolytic nickel-electroless nickel-electrolyte nickel, etc. into a double electronickel plating process, the corrosion resistance of the Nd-Fe-B magnet provided by the conventional method is equal to or It provides a product having the above high corrosion resistance.

In the post-treatment process, waste water treatment costs and environmental problems are reduced by developing a chromate process using hexavalent chromium and a post-treatment process that satisfies corrosion resistance and solderability at the same time by eliminating the use of paraffin-based water rust preventive agents that reduce solderability. Can actively respond to

Claims (7)

As a double nickel plating method of Nd-Fe-B-based permanent magnet composed of a pretreatment step, plating step and post-treatment step, A pretreatment step (S1) consisting of surface cleaning, immersion degreasing, etching, desmuting and stabilization of the permanent magnet; Forming a double nickel plated layer for performing secondary gloss nickel plating after the first semi-gloss nickel plating after the pretreatment step (S1) (S2); And After the step (S2) comprises a post-treatment step (S3) to form a surface layer to prevent oxidation of the plated nickel layer and improve the corrosion resistance, A water washing step is included between each step in the step (S1), in the etching step in the step (S1) ethanol 100 ~ 500mL / L, glacial acetic acid 60 ~ 120mL / L, lactic acid 30 ~ 100mL / L Using an etchant which is at least one main ingredient selected from the group consisting of hydrogen peroxide 20 ~ 100ml / l, using nickel sulfate in the first plating in the step (S2) and the second plating is nickel sulfamate , The first and second plating is performed using a pulse rectifier, the step (S3) is carried out by the OSP process consisting of benzoimidazole and nickel atoms, and after drying the water after washing with water in 50 ~ 60 ℃ pure water after the OSP process Double nickel layer plating method of Nd-Fe-B-based permanent magnets, characterized in that made. delete delete delete delete delete delete

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