Packaging-compatible microinductors and microtransformers with screen-printed ferrite using low temperature processes

Fully integrated microinductors and microtransformers compatible with organic (low-temperature) electronic packaging are investigated for miniaturized power converters, filters, multichip modules (MCMs), and other consumer electronic products. Four differing geometries of ferrite-based integrated magnetic components have been designed, fabricated, and tested: sandwich-spiral, sandwich-meander, two layer vertically stacked spiral, and bar type (open and closed magnetic circuit). In the comparison of fabricated microinductors, two layers vertically stacked spiral inductors with 50 pm height has the largest inductance (15 μH/cm² at 10 MHz) and dc resistance (2.1 ohms). The smallest inductance (1.2 μH/cm² at 1 MHz) and dc resistance (0.35 ohms) are achieved in the fabricated bar type microinductor with a closed magnetic core. In the comparison of fabricated microtransformers, the EMI shielded sandwich type spiral transformer has the best gain characteristics and the lowest resonant frequency (27 MHz), the EMI shielded sandwich-meander-type transformer has the worst gain characteristics, and the closed bar type transformer has the highest resonant frequency (38 MHz)