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General Manager James Hofer of Accurate Circuit Engineering discusses the process of backdrilling vias, including the benefits and drawbacks. Backdrilling can improve signal integrity, but it can create stubs that may act as unwanted antennas.
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Yuriy Shlepnev, Simberian
The usual way of signaling through PCB interconnects is a two-level pulse, an encoding of 1s and 0s or bits, named NRZ (non-return-to-zero) or PAM-2 line code type. Increasing the data rate with the NRZ code type presents some obstacles. For a 28 Gbps NRZ signal, the bit time is about 35.7 ps with the main spectral lobe below 28 GHz. For a 56 Gbps NRZ signal, the bit time is about 17. 86 ps, with the main spectral lobe below 56 GHz. One can feel the problem already: Getting PCB interconnect analysis and measurements up to 56 GHz and beyond is very challenging, to say the least.
Bill Acito, Cadence Design Systems
The challenges faced by the PCB designers of today are significant. If we examine the breadth of designs, we find ever-increasing data rates and more high-speed signal routing that drive additional challenges meeting signal-quality requirements, including reflection signal loss and crosstalk issues. At the same time, designers are being asked to complete designs in shorter cycle times and in smaller form factors. They must come up with new and more complex routing strategies to better control impedance and crosstalk. Manual implementation is often time-consuming and prone to layout errors.
Christian Keller, Altium
PCB developers are deluged with new challenges caused by increasing density and smaller components. Ball grid arrays (BGAs) create particular challenges during layout, with hundreds of connections in just a few square centimeters. Fortunately, designers now have options for addressing these issues.