This paper describes the realization of bond-wire micro-magnetics by using standard bonding-wires and a toroidal ferromagnetic LTCC core with high resistivity. The proposed fabrication procedure is suitable for the development of magnetic components on top of an IC with small profile and small size (< 15 mm2). A transformer is designed and applied over-chip, working in the MHz range with high inductance (~33 μ H) and high effective turns-ratio (~20). Applications include bootstrap circuits and micro-power conversion for energy harvesting. Measurements demonstrate a maximum secondary Q-factor of 11.6 at 1.3 MHz, and a coupling coefficient of 0.65 with an effective turns ratio of 19, which are among the highest values reported for toroidal miniaturized magnetics. The achieved inductance density is 2 μH/mm2, along with an inductance per unit core volume of 15.6 μH/mm3, and a DC inductance-to-resistance ratio of 2.23 μH/Ω. The presented technique allows to obtain over-chip magnetics trough a post-processing of the core, and it is also suitable for highdensity power supply in package (PwrSiP) and power supply on chip (PwrSoC). Finally, a series of optimization techniques for planar core magnetic devices in order to maximize the inductance per unit area are discussed and applied to the considered case.
Design and Optimization Techniques of Over-Chip Bondwire MicroTransformers with LTCC core
CAMARDA, ANTONIO;TARTAGNI, MARCO;ROMANI, ALDO
2018
Abstract
This paper describes the realization of bond-wire micro-magnetics by using standard bonding-wires and a toroidal ferromagnetic LTCC core with high resistivity. The proposed fabrication procedure is suitable for the development of magnetic components on top of an IC with small profile and small size (< 15 mm2). A transformer is designed and applied over-chip, working in the MHz range with high inductance (~33 μ H) and high effective turns-ratio (~20). Applications include bootstrap circuits and micro-power conversion for energy harvesting. Measurements demonstrate a maximum secondary Q-factor of 11.6 at 1.3 MHz, and a coupling coefficient of 0.65 with an effective turns ratio of 19, which are among the highest values reported for toroidal miniaturized magnetics. The achieved inductance density is 2 μH/mm2, along with an inductance per unit core volume of 15.6 μH/mm3, and a DC inductance-to-resistance ratio of 2.23 μH/Ω. The presented technique allows to obtain over-chip magnetics trough a post-processing of the core, and it is also suitable for highdensity power supply in package (PwrSiP) and power supply on chip (PwrSoC). Finally, a series of optimization techniques for planar core magnetic devices in order to maximize the inductance per unit area are discussed and applied to the considered case.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.