Manufacture and characterisation of micro-engineered DC-DC power converter using UV-LIGA process

A novel method to manufacture a micro-inductor that is based on flip-chip bonding assembly is described. The micro-inductor is developed for DC-DC converters operating in the MHz switching frequency. The fabricated inductors have an inductance ranging from 0.12 to 118 µH. An optimum Q-factor of 2 was attained at 1 MHz. Nickel-iron cores with integrated air-gaps maintained a constant inductance across a 1 kHz-5 MHz bandwidth. The thin film laminate minimised eddy current loss and hysteresis loss was negligible. Impedance increased linearly with frequency, indicating that parasitic capacitance effects in this frequency range were negligible. The micro-inductor operated at an efficiency of 92% at 1 MHz, achieving a power density of 4.2 W/cm³.