Summers Jason M, Sakri Shambhavi, Chakma Nishako, Luyen Hung, Bujanda Andres, Parker Thomas, Tsang Harvey, Shepherd Nigel D
Department of Materials Science and Engineering, University of North Texas, Denton, TX 76207, USA.
Department of Electrical Engineering, University of North Texas, Denton, TX 76207, USA.
Materials (Basel). 2024 Apr 11;17(8):1756. doi: 10.3390/ma17081756.
High-frequency transmission is limited to the skin depth in metals. Because poor conductivity cannot be compensated for by increasing the conductor thickness as with DC, optimal transport properties are prerequisites for radio frequency (RF) use. Structural and chemical analyses of transmission lines printed using a traditional ink consisting of Ag nanoflakes in a dispersing phase revealed that optimized thermal treatments yielded thorough burnout of the binder, significant grain growth, elimination of the pore volume, and electrical responses that were comparable to values obtained for thermally evaporated, fully dense Ag controls. Specifically, a low DC resistivity of 2.3 μΩ·cm (1.4× bulk Ag) and RF transmission coefficients of 0.87 and 0.75 at 5 GHz and 10 GHz, respectively, were measured in the nanoflake Ag prints. Conversely, in transmission lines printed from a metal-organic decomposition ink, residual chemical contamination impeded diffusion and densification, yielding greater porosity, small grains that are pinned, and a degraded RF response. Reasonably good porosity approximations were obtained from a model based on percolation theory. The results indicate that contaminants at interfaces and pore surfaces impede diffusion, pore elimination, and full densification, and further, alter carrier dynamics and degrade RF response.
高频传输限于金属中的趋肤深度。由于不像直流那样可以通过增加导体厚度来补偿导电性差的问题，因此最佳传输特性是射频（RF）应用的先决条件。对使用由分散相中银纳米片组成的传统油墨印刷的传输线进行的结构和化学分析表明，优化的热处理可使粘合剂彻底烧尽、晶粒显著生长、孔隙体积消除，并且电响应与热蒸发的完全致密银对照所获得的值相当。具体而言，在纳米片银印刷品中测得的直流电阻率低至2.3μΩ·cm（为块状银的1.4倍），在5GHz和10GHz时的射频传输系数分别为0.87和0.75。相反，在由金属有机分解油墨印刷的传输线中，残留的化学污染物阻碍了扩散和致密化，导致孔隙率更高、晶粒细小且被固定，以及射频响应变差。基于渗流理论的模型获得了合理良好的孔隙率近似值。结果表明，界面和孔表面的污染物会阻碍扩散、孔隙消除和完全致密化，进而改变载流子动力学并降低射频响应。
