PCB and package level wireless power transfer interconnection scheme using magnetic field resonance coupling

Abstract

To keep up with the rising trend of high-performance mobile devices, various chips with different functions are mixed and packaged into individual products. As the technology develops, the number of chips increases while the thickness of mobile products continuously decreases, which requires high-density packaging technique with high number of power and signal lines. For routability of signal and power pins, avoiding crosstalk and overlap between high pitch metal lines has become a challenge in printed circuit board (PCB) and package design. By applying wireless power transfer technology in PCB and package level, the number of power pins can be greatly reduced to produce more space for signal pins and other components in the system. For the first time, in this paper, we propose and demonstrate high efficiency PCB and package level wireless power transfer interconnection scheme using magnetic field resonance coupling. The proposed scheme wirelessly transfers power from the source to the receiver on PCB and package level using rectangular spiral coils. The equivalent circuit model is suggested with analytic equations, and the values of each component are calculated by applying the physical dimensions and material properties. Including the effect of parasitic components in PCB and package level, the suggested model is experimentally validated up to 1 GHz by comparing Z-parameter results from the model-based equation and measurement of the designed and fabricated test vehicles. The test vehicles consist of two major parts: the source board and the receiver board. On both of the boards, 10 mm by 10 mm sized rectangular spiral coils are printed for the actual wireless transfer of power and matching capacitors are mounted for resonance frequency tuning. The measurement of the test vehicles is conducted in various conditions to enhance the efficiency of the scheme. We analyzed the impact of ferrite material beneath the source and receiver boards for shielding and guiding of the magnetic field. In addition, we measured the test vehicles by supplying sinusoidal source from a signal generator with 50 Ω source resistance and a bipolar amplifier with 3.3 Ω source resistance for comparison. Finally, The power transfer efficiency from the source coil to the receiver coil in this scheme is able to reach 85.6% and we designed and fabricated a CMOS full bridge rectifier and mounted it on the receiver board to convert the transferred voltage from AC voltage to DC voltage. The measured DC voltage of 2.0 V is sufficient to operate the circuit, which generally consists of 1.5 V devices. The model-based equations are further analyzed to estimate the voltage transfer ratio and power transfer efficiency in the proposed scheme for design optimization.