対応力磁気特性安定化フェライト材料の開発 Development of Stress-insensitive Ferrite
The sensitivity of the magnetic property to the external stress in NiCuZn ferrite was examined from the relationship between stress and permeability. In the production process of inductors, external stress is applied to the NiCuZn ferrite core by molding the resin, which is a protection against humidity or shock. As the permeability of NiCuZn ferrites are very sensitive against the external stress, the inductance of inductors changes very easily by the applied stress. This change has been recognized as the barrier to produce the inductors with a narrow inductance tolerance. We found the best way to control the stress-sensitivity of permeability in NiCuZn ferrite by the addition of oxide such as SiO2, and the inductance change can be completely explained from the residual stress caused by the difference of coefficients of linear thermal expansion between spinet phase (magnetic) and second phase (non-magnetic). By this new process, we succeeded in developing "Stress-insensitive Ferrite", and the mass production of the inductors with a narrow inductance tolerance.
粉体および粉末冶金 45(1), 53-57, 1998-01-15
Japan Society of Powder and Powder Metallurgy