# US 10,770,224 B2 · Method for forming electrolytic copper plating film on surface of rare earth metal-based permanent magnet

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- Number: US 10,770,224 B2
- Document ID: US10770224B2
- Status: Granted
- Kind: B2
- Application number: 16/020,650
- Filed: 2018-06-27
- Published: 2018-12-06
- Granted: 2020-09-08
- Earliest claimed: 2010-09-30
- Assignees: Hitachi Metals, Ltd.
- Applicants: Hitachi Metals, Ltd.
- Inventors: Masanao Kamachi; Koshi Yoshimura
- Web page: https://patentgrep.com/patent/US10770224B2

## CPC

- H01F 41/026: {protecting methods against environmental influences, e.g. oxygen, by surface treatment (magnetic particles with skin H01F1/061, H01F1/09, H01F1/24, H01F1/33 and G11B5/706)}
- C25D 3/38: of copper
- C25D 7/001: {Magnets}
- H01F 7/0221: {Mounting means for PM, supporting, coating, encapsulating PM}
- H01F 41/26: using electric currents {, e.g. electroplating}
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- C25D: PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR

## Abstract

An object of the present invention is to provide a novel method for forming an electrolytic copper plating film having excellent adhesion on the surface of a rare earth metal-based permanent magnet. The method of the present invention as a means for achieving the object is characterized in that after a magnet is immersed in a plating solution, a cathode current density of 0.05 A/dm2 to 4.0 A/dm2 for performing an electrolytic copper plating treatment is applied thereto over 10 seconds to 180 seconds to start the treatment.

## Claims

### Claim 1

A method for forming an electrolytic copper plating film on the surface of a rare earth metal-based permanent magnet, comprising the steps of:
immersing the rare earth metal-based permanent magnet in a plating solution containing Cu2+ ions,
applying an increasing cathode current density in a range of 0.05 A/dm2 to 4.0 A/dm2 to the rare earth metal-based permanent magnet over 10 seconds to 180 seconds, wherein a cathode current density increase rate for applying the increasing cathode current density is 0.002 A/(dm2×sec) to 0.4 A/(dm2×sec), until a predetermined value of current density is reached, and then
performing an electrolytic copper plating treatment at the predetermined value of current density.

### Claim 2 (depends on 1)

The method according to claim 1, characterized in that the step for performing an electrolytic copper plating treatment is performed for a period of time of 2 minutes to 450 minutes.

### Claim 3 (depends on 1)

The method according to claim 1, characterized in that the plating solution is alkaline.

### Claim 4

A method for improving the adhesion of an electrolytic copper plating film formed on the surface of a rare earth metal-based permanent magnet, comprising the steps of:
immersing the rare earth metal-based permanent magnet in a plating solution containing Cu2+ ions,
applying an increasing cathode current density in a range of 0.05 A/dm2 to 4.0 A/dm2 to the rare earth metal-based permanent magnet over 10 seconds to 180 seconds, wherein a cathode current density increase rate for applying the increasing cathode current density is 0.002 A/(dm2×sec) to 0.4 A/(dm2×sec), until a predetermined value of current density is reached, and then
performing an electrolytic copper plating treatment at the predetermined value of current density.