Fabrication and characterization of parylene-bonded Nd–Fe–B powder micromagnets

This paper presents the fabrication and characterization of parylene-bonded isotropic Nd–Fe–B powder micromagnets with dimensions in the range of 100–1000 μm. The batch fabrication process involves dry-pressing of magnetic powders into microstructured cavities in a substrate followed by conformal vapor deposition of parylene C. The parylene coating penetrates the gaps between the magnetic particles and mechanically bonds the powder. Additionally, by mixing magnetic powders with different particle sizes, higher fill factors are achieved, thereby increasing the magnetic moment and energy product. An intrinsic coercivity of 720 kA/m, a remanence of 0.36 T, and a maximum energy product of 22 kJ/m³ are demonstrated for magnets with dimensions 700 × 700 × 220 μm. The room-temperature processing steps and chemically stable parylene coating facilitate the integration of these magnets with other microfabrication processing steps.