Fabrication of hard magnetic microarrays by electroless codeposition for MEMS actuators

We report on a new electroless codeposition system for fabricating hard magnetic NdFeB particle-NiP alloy magnets for magnetic micro-electro-mechanical systems (MEMS) actuators. In the newly developed electroless codeposition process, an NdFeB hard magnetic particle, which cannot be independently deposited from aqueous electrolytes, is added to an acidic NiP alloy electroless plating electrolyte. An NdFeB (particle)-NiP (matrix) composite thin film has been successfully obtained using an optimized electroless codeposition technique. In addition, NdFeB-NiP microarrays magnets with a thickness of 20 μm have been realized by surface micro-machining techniques. These micromachined magnets exhibit good magnetic properties such as a large (BH)max and a high perpendicular coercivity (Hc) that are particularly well suited for magnetic MEMS actuators. This deposition technique is compatible with many MEMS fabrication processes since it does not demand high processing temperatures.