Design and analysis of magnetically coupled coil structures for PCB-to-active interposer wireless power transfer in 2.5D/3D-IC

In this study, magnetically coupled coil design for high efficiency wireless power transfer (WPT) in PCB-to-active silicon (Si) interposer is proposed and analyzed using Z-parameter analysis. For strong magnetic coupling between transmitter (Tx) coil on PCB and receiver (Rx) coil on Si-interposer, each coil structure is selected considering process dimension difference between PCB and Si-interposer. The equivalent circuit models for Tx coil on PCB and Rx coil on Si-interposer are suggested. Especially, the Rx coil model includes lossy Si-substrate characteristics and eddy current effect. In addition, analytical model for vertically aligned Tx coil and Rx coil in 2.5D/3D-IC is developed by considering LC resonance. All the proposed equivalent circuit models are analyzed by comparing Z-parameters (Z₁₁) with 3D EM simulation results. In this coil system, series-series WPT topology is applied to achieve high power transfer efficiency (PTE) and maintain a constant resonant frequency regardless of load impedance. The resonant frequency for high PTE is decided to be 100 MHz.