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54 DESIGN007 MAGAZINE I AUGUST 2021 Article by Chang Fei Yee KEYSIGHT TECHNOLOGIES Abstract is article briefly introduces various via structures on the printed circuit board (PCB) for layer transition purposes. It also investigates the impact of these via structures on multi- gigabit transmission by analysing time domain reflectometry (TDR), differential insertion loss (Sdd21), and eye diagrams. Introduction e via is an essential structure used to make an electrical connection between the layers in multilayered PCBs. Connecting multiple lay- ers of the board makes it possible to reduce the dimensions of the PCB. e via structures available in the PCB industry include through- hole vias and microvias, as depicted in Figure 1. A through-hole via goes straight through the PCB from top to the bottom and can be applied to connect all the layers of a PCB. It is the most common via and is easiest to con- struct. A microvia, on the other hand, con- nects the outermost layer of a PCB to an inner layer, but is not visible on the other side of the board. Microvias are classified as staggered or stacked. With stacked microvias, the via barrels are constructed on top of each other in distinct layers. Staggered microvias, however, are scat- tered in various layers, and each via barrel is linked with a short horizontal conductive bar. ere are two major advantages of selecting microvias over through-hole vias. First, the microvia has a smaller dimension and aspect ratio, which facilitates the miniaturization of The Impact of Via Structures on Multi-Gigabit Signal Transmission Figure 1: Various via structures on PCBs. (Source:

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