Tiny Wafer Level Chip Scale Packaged Inductive Components for High Frequency Isolated/Non-Isolated DC-DC Converters

This paper shows fully packaged on-chip microtransformers and microinductors fabricated on silicon using thin film technology. The devices are packaged using wafer level chip scale packaging (WLCSP) technology. The microtransformer device presented in this paper shows a self-inductance of about 85 nH with a Q-factor of 13.6 at frequency in the range between 20 MHz and 30 MHz. The microtransformer has stable characteristics up to 50 MHz, has a saturation current of 480mA, and rated current of 850mA. The microinductor has an inductance of 97 nH with a Q-factor higher than 15. Both devices have the same package size. The package footprint (chip size) is 2.6 mm x 2.4 mm with a package height of 0.4 mm where the soldering balls height is about 170 μm. Soldered device on a printed circuit board (PCB) has a total height lower than 0.3 mm.