Injection Moulding of Highly Filled Soft Magnetic Compounds for the Production of Complex Electric/Electronic (Micro-) Parts

Summary Electric/electronic devices become increasingly more complex and are used in highly integrated assembly groups. Soft magnets generally show only “moderate” magnetic properties; however, they exhibit a comparably high permeability which allows the material for being used in conjunction with hard magnets as a “magnetic conductor”. Thus, the magnetic flux density of such parts can be improved leading to a better accuracy and functionality of switches, valves or pumps. In particular for micro applications the use of plastics‐bonded soft magnets in combination with hard magnets integrated in one injection moulded part provides new opportunities for electric/electronic devices. The Institute of Plastics Processing (IKV) at the RWTH Aachen further develops in cooperation with Siemens, Oechsler, and Arburg soft magnetic compounds focusing on micro applications. The magnetic properties of plastics‐bonded soft magnets are significantly reduced compared to pressed or sintered materials. Compounds filled with spherically shaped fillers as iron‐silicon show better flow and processing properties compared to irregular‐ or flaky‐shaped fillers. Due to the specific flow conditions the magnetic properties are not homogeneous throughout the part. At the end of the flow path the filler content is considerably increased leading to higher soft magnetic properties. This can be well correlated by means of microscopic analyses.