| 摘要 |
PURPOSE:To eliminate errors of reading and writing of signals occurring in noises by producing a molding material contg. magnetic particles by injection molding and specifying its actual magnetic permeability to a prescribed value or above at a prescribed frequency. CONSTITUTION:A slurry-like raw material is obtd. by adding 15 to 50vol.% binder 12 to ferrite powder 11 composed of 40 to 70mol% Fe2O3 0 to 30mol% ZnO and the balance Mn0, as ferrite, and subjecting the mixture to kneading 13 under heating at 90 deg.C in order to produce the shielding ring made of the ferrite. The average grain size of the ferrite powder 11 is specified to 0.5 to 2.0mum. This raw material is injected into the molds of an injection molding machine, by which a composite molding 14 is obtd. The shielding ring core molded by the injection molding is afterward made into the shielding ring core 23 having an intricate shape but the composite molding 14 contains a large amt. of the binder 12 and is, therefore, thermally decomposed first in a degreasing furnace, by which the molding is degreased 15. The molding is then calcined at a high temp. from 1000 to 1400 deg.C, by which the product core 23 is obtd. The actual magnetic permeability mu.' at 100KHz frequency is increased to >=4000 and the errors occurring in the noises generated by peripheral apparatus are eliminated. |
