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60 DESIGN007 MAGAZINE I OCTOBER 2019 The new 5G cellular infrastructure has many technological differences from previous infra- structures, which will impact the PCBs and materials used to build these circuits. 5G ap- plications are generally split up into two fre- quency bands: sub-6 GHz and millimeter-wave (mmWave). Most of the initial deployments for 5G technology will be based on the sub-6 GHz band of frequencies; however, there are al- ready mmWave 5G systems, and in the future, there will be more. A quick overview of the benefits of the 5G systems shows that 5G will have much high- er digital rates and lower latency. The data rates will likely be in the hundreds of Mbits/ second, and the latency will be better than 20 ms. The boosts in 5G technology will enable enhanced mobile broadband (eMBB), massive machine-type communications (MMTC) and ultra-reliable and low-latency communications (uRLLC). The PCBs associated with 5G appli- cations will have a much higher level of inte- gration and greater functionality, which trans- lates to more demanding designs and a broad- er combination of circuit materials. The enhancements of 5G can cause more PCB thermal management issues for certain cir- cuit functions. The heat generated by the 5G PCB is often related to insertion loss. Basically, a circuit with higher insertion loss will generate more heat. Once the heat is generated, chan - neling the heat effectively to a heat sink struc- ture is important. Some circuit material proper- ties that are important to consider include dis- sipation factor and thermal conductivity. A low-loss, high-frequency circuit material will have lower insertion loss and will, there- fore, generate less heat. These high-frequency circuit materials usually have a low dissipa- tion factor (Df) and often use a copper with a smoother surface. It is well-known that copper surface roughness will impact insertion loss, and a copper with a low profile, or smooth cop- per surface, will generate less insertion loss. Material Choices for 5G PCB Applications Lightning Speed Laminates by John Coonrod, ROGERS CORPORATION

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