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The inductance of low temperature processable particulate filled polymer matrix composite inductors is constrained by the limited magnetic properties of the polymer matrix. The microstructural and electrical properties of inductors made from amorphous nickel-zinc-iron oxide matrix filled with polycrystalline Nickel Zinc Ferrite (NZF) fillers are investigated in this study. NZF has high resistance, and is essential for high Pequency application to reduce eddy current loss. Planar spiral NZF-composite (with 20v% fillers) inductors were fabricated on glass wafer substrate and heated treated at different temperatures. The electrical properties of the inductors were characterized at frequencies in the MHz range. The inductance is found to increase between 10% -20% for composite inductor afrer heated at 300°C for 1 hour. The increase is comparable to those reported previously for polymer fem'te composite inductors, albeit the polymer version has signijicantly higher filler content (90wt%) while the current NZFcomposite filler content is markedly less (IO-20%). This indicates that the increase is associatedwith improvement of the matrix's properties. The changes in matrix microstructures were characterized by X-ray diffraction. The increase in inductance and associated electrical properties are then explained based on the observed microstructural changes. The increase in matrix inductance indicates that the current approach has strong potential in giving a large enhancement in inductance when high jiller content is used.

Capacitors, resistors and inductors are surface mounted components on circuit boards, which occupy up to 70% of the circuit board area. For selected applications, these passives are packaged inside green ceramic tape substrates and sintered at temperatures over 700°C in a co-fired process. These high temperature processes are incompatible with organic substrates, and low temperature processes are needed if passives are to be embedded into organic substrates. A new high permeability dual-phase Nickel Zinc Ferrite (DP NZF) core fabricated using a low temperature sol-gel route was developed for use in embedded inductors in organic substrates. Crystalline NZF powder was added to the sol-gel precursor of NZF. The solution was deposited onto the substrates as thin films and heat-treated at different temperatures. The changes in the microstructures were characterized using XRD and SEM. Results showed that addition of NZF powder induced low temperature transformation of the sol-gel NZF phase to high permeability phase at 250°C, which is approximately 350°C lower than transformation temperature for pure NZF sol gel films. Electrical measurements of DP NZF cored two-layered spiral inductors indicated that the inductance increased by three times compared to inductors without the DP NZF cores. From microstructural observations, the increase is correlated with the changes in microstructural connectivity of the powder phase.