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66 DESIGN007 MAGAZINE I APRIL 2019 Article by Chang Fei Yee KEYSIGHT TECHNOLOGIES This article briefly introduces the general purposes of copper ground pour on printed circuit boards. Subsequently, the impact of copper ground pour on PCB channel loss in terms of insertion loss and impedance in terms of time domain reflectometry (TDR) is studied with electromagnetic modeling using Mentor HyperLynx. Introduction Copper ground pours are created by filling open, unpopulated, or unrouted areas on outer layers of the PCB with copper. Subsequently, copper fill is hooked up to ground planes on inner layers with stitching vias as depicted in Figure 1. Copper ground pours on outer layers provide extra shielding against electromagnetic radiation by signals on inner layers. Besides that, copper pour also serves as a heat sink for the voltage regulator module on PCBs. In terms of manufacturability, copper pour reduces the possibility of PCB warpage during reflow by balancing the amount of copper on each side of the PCB. However, copper ground pour comes with some disadvantages, as there is a change in EM Modeling: The Impact of Copper Ground Pour on Loss and Impedance Figure 1: Top view of the PCB with copper ground pours.