Embedded ferromagnetic technology

The processes used to manufacture magnetic components have changed little over the last several decades. Essentially, these components-which include isolation transformers, directional couplers, frequency mixers, common mode chokes, baluns, etc.-are hand-made. Manual operations include magwire prep, winding, dipping, solder termination, encapsulation and electrical testing. In addition, each process requires multiple inspections steps. Embedded ferromagnetic technology (EFT) provides an automated way to fabricate high-performance, high-reliability magnetic components at reasonable cost. The EFT process incorporates advanced PWB fabrication in combination with high-aspect ratio laser drilling and plating techniques, First, toroidal-shaped ferrite cores are embedded into a PWB laminate structure. Pairs of signal layers, comprised of patterned copper conductors, are joined electrically by laser drilled and plated micro-via through-holes to simulate electrical windings. Typical isolation transformers are fabricated with two isolated sets of micro-vias on pairs of signal layers. The presentation includes details of the fabrication processes and electrical testing of EFT-based transformers.