Restoration of Broadband Inductor and Transformer Performance After Ferrite Grinding

For broadband inductor and signal transformer applications, ferrite core materials deliver the best magnetic performance. For low-profile circuit-board applications, ferrite materials must be ground to the proper thickness to fit within the desired form factor. Ferrite grinding, however, will result in mechanical stresses in the ferrite, reducing the material permeability. In this study, three methods of restoring ferrite permeability after grinding were surveyed (etching, polishing, and annealing) on three different ferrite materials. Advantages and disadvantages of the three techniques are discussed, though it has been found that only etching and polishing were effective in permeability restoration; annealing, by means carried out in this study, reduced the ferrite permeability.