Apparatus and method for coating of small Nd-Fe-B magnets

A method of coating a plurality of Nd—Fe—B magnets including grease using a furnace having a side wall defining a chamber disposed on a center axis and an outlet aperture and an inlet aperture and, a rear wall affixed to the side wall, a shaft rotatable about the center axis extending through the rear wall and into the chamber, a roller defining a compartment and rotatably attached to the shaft, at least one target source holder disposed on the side wall, a target source of aluminum on the target source holder, and a plurality of conductors of metal and having a spherical shape, said method comprising the steps of;

• shaping the plurality of Nd—Fe—B magnets into a plurality of small Nd—Fe—B magnets,
• said step of shaping being further defined as shaping the plurality of Nd—Fe—B magnets into a plurality of small Nd—Fe—B magnets defining a length and a width and a thickness with each of the length and the width and the thickness being no more than 15 mm and the difference between the length and the width and the thickness being no more than 10 mm,
• cleaning the small Nd—Fe—B magnets to remove the grease,
• said step of cleaning further including a step of washing the small Nd—Fe—B magnets using an acid,
• disposing the small Nd—Fe—B magnets in the compartment of the roller in the chamber,
• sealing the chamber of the furnace,
• removing air from the chamber through the outlet aperture of the side wall to reduce pressure in the chamber to a first pressure range of between 6.0×10−3 Pa and 9.0×10−3 Pa,
• further removing air from the chamber through the outlet aperture of the side wall to further reduce the first pressure range in the chamber to a final pressure range of between 3.0×10−3 Pa and 6.0×10−3 Pa,
• feeding an inert gas of Argon into the chamber at the final pressure range to increase the pressure in the chamber to between 3.0×10−1 Pa and 6.0×10−1 Pa,
• said step of feeding the inert gas being further defined as feeding the inert gas of Argon through the inlet aperture of the side wall into the chamber at the final pressure range,
• depositing a film on the small Nd—Fe—B magnets,
• said step of depositing the film further including a step of applying an electrical potential of 20V to the target source of aluminum to produce a plurality of ions of aluminum,
• said step depositing the film further includes a step of directing the ions of aluminum to the small Nd—Fe—B magnets to produce the film,
• said step of disposing the small and the plurality of conductors in the compartment further including a step of disposing the plurality of conductors defining a particle size between 2 mm and 6 mm and having the predetermined weight of between 0.25 to 1.5 times the weight of the small Nd—Fe—B magnets with the small Nd—Fe—B magnets in the compartment of the roller in the chamber of the furnace,
• mixing the small Nd—Fe—B magnets and the plurality of conductors in the roller at the first pressure range,
• said step of mixing being further defined as rotating the roller containing the small Nd—Fe—B magnets and the plurality of conductors at a rate of between 5 rpm and 20 rpm.