Theoretical study on lowering loss of skin effect suppressed multi-layer transmission line with positive/negative (Cu/NiFe) permeability materials for high data-rate and low delay-time I/O interface board

Abstract

This paper proposes a new application of skin effect suppression technology for long wiring on high-speed & low-delay I/O board. This proposal will overcome the difficulty of further reducing the transmission losses on the I/O board with vert >vert 50 Gb/s data rate. In previous research, it was demonstrated that suppression of the skin effect by electroplated conductor/magnetic multi-layer, and estimated that the degree of transmission loss decrease at 16 GHz would be 5 %. A major challenge in this paper is to propose an electromagnetic field calculation theory for rectangular multi-layer transmission line, verify it under the same conditions, clarify a lower loss structure by changing thickness of each layer. Also it is expanded to low loss design technology. Cu and NiFe were selected as metal conductor material and negative permeability magnetic material, respectively. The Cu and NiFe films are alternately stacked to form the multi-layer. The top and bottom surface layers are Cu layers. The loss suppression was compared under the following conditions. 1) Total number of layers was 33 and total thickness was 12.67 μm by a constant ratio, Cu: tN = 0.51μm and NiFe: tF = 0.25μm. 2) Optimal stacking determined by changing the thickness of each layer. Compared to conventional thickness by a constant ratio 1), in our proposal 2), we estimated that the loss would dropped to 92% in optimal thickness. By offsetting the phase change of current density, a lower loss structure could be determined. Compared with Cu conductor, the top and bottom surface current densities become low, and depth center current density becomes slightly high for the multi-layer, showing the skin effect is suppressed.