High frequency high current point of load modules with integrated planar inductors

Abstract

Planar inductors made by mixed laminates of commercially available low-fire Ni-Cu-Zn ferrite tapes and metal-flake composites developed by NEC-TOKIN have been used for the high density integration of point-of-load (POL) modules. The incremental permeability and core loss density were characterized on the toroidal samples under high dc bias. Measurement results demonstrate that both materials are suitable for applications in high frequency high current POL converters. In order to realize a high power density POL module, a multilayer ferrite inductor laminated with alternating layers of ESL 40010 and ESL 40012 in a 1:1 ratio has been fabricated and integrated with the active layer using modified low temperature co-fired ceramics (LTCC) processing. Meanwhile, the standard printed circuit board (PCB) processing has been adopted for the POL integration with a PCB embedded inductor using metal-flake composite materials. These developed 3-dimensional (3-D) integration approaches can be used to reduce the footprint and increase the power density for the high frequency high current POL converter. It is demonstrated that the power efficiency of POL modules with integrated planar inductors can achieve above 87% at operating frequency of 2 MHz and output current of 15 A. Additionally, no obvious efficiency degradation was observed on the integrated POL modules after certain numbers of thermal cycling from -40 °C to +150 °C.