Fundamental study on the mechanical strength of soft magnetic composite prepared by ultra-high aspect ratio flake iron powder using ball-milling process

ABSTRACT Soft magnetic composites (SMCs) are consolidated ferromagnetic powders covered with polymers. Ultra-thin flat powder can effectively reduce eddy current loss of SMCs, even at the frequency at which next-generation semiconductor devices are driven. In this study, pure iron powders were processed with ball-milling to obtain the ultra-thin powder and prepare the SMC. The effect of aspect ratio of the powder on the mechanical strength of SMC was investigated. Although the maximum bending stress of SMC made of iron particles with an aspect ratio of 1140 reached 60% of the strength of sintered iron powder, the increase in the maximum bending stress with increasing aspect ratio slowed down when the aspect ratio exceeded 100. The reason for the slowdown was assumed to be a decrease in insulating film coverage on the particle at high aspect ratio ranges due to the stacking and welding of particles during the ball milling process.