Planar spiral inductors with multilayer micrometer-scale laminated cores for compact-packaging power converter applications

Ultralow (0.4 mm) profile spiral inductors with multilayer micrometer-scale NiFe laminated cores were developed for compact-packaging power applications. A simple sacrificial Cu etching process was used to realize seven layers of 1.8-μm-thick laminations, forming the magnetic cores. The laminated cores were combined with a spiral coil to fabricate the spiral inductor in a hybrid fashion. The dimension of a complete device is 40 × 15 mm. In situ electrical characterization verified compatibility with compact-packaging applications. The inductor was implemented in a boost converter (5-10 V) operating at 2.2 MHz, which demonstrated 2-W output with overall efficiency exceeding 70%.