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MAY 2021 I DESIGN007 MAGAZINE 69 of the SMD pads is only 0.5 mm, those cop- per "noses" can result in solder bridges during assembly of the components. As a result, we removed all reported copper stubs. Several warnings for stubbed vias were also reported. Buried vias between layer 2 and 9 of the core were only connected on one side. ose vias are useless, can cause a significant signal degradation, and lead to higher drill- ing cost. We could improve the quality of our design by removing those buried vias. A violation against the constraint "same net spacing" was reported on layer 3 (Figure 4). e small space between copper structures of the same net creates an acid trap. An acid trap has the potential to trap chemical etchants used to strip excess copper from a board during the manufacturing process. When the etching solution pools in a certain area, there is a risk for corrosion of traces and creation of faulty connections or open circuits. So we changed the routing, keeping in mind the length-match- ing requirement. Our experience with running DFM analysis with PCBflow on this board, and many other experiments, illustrated that we could improve the design in a very short time without any interaction with the PCB manufacturer during the layout phase. DESIGN007 Pol Ghesquiere is a project manager with the Technology Department of Siemens in Munich, Germany. Oren Manor serves as the director of business develop- ment for Valor Division of Siemens Digital Industries Software. Unconventional superconductors contain a num- ber of exotic phases of matter that are thought to play a role, for better or worse, in their ability to con- duct electricity with 100% efficiency at much higher temperatures than scientists had thought possi- ble—although still far short of the temperatures that would allow their wide deployment in perfectly effi- cient power lines, maglev trains and so on. Now scientists at the Department of Energy's SLAC National Accelerator Laboratory have glimpsed the signature of one of those phases, known as pair- density waves or PDW, and confirmed that it's inter- twined with another phase known as charge density wave (CDW) stripes—wavelike patterns of higher and lower electron density in the material. Observing and understanding PDW and its cor- relations with other phases may be essential for understanding how superconductivity emerges in these materials, allowing electrons to pair up and travel with no resistance, said Jun-Sik Lee, a SLAC staff scientist who led the research at the lab's Stan- ford Synchrotron Radiation Lightsource (SSRL). The existence of the PDW phase in high-temper- ature superconductors was proposed more than a decade ago and it's become an exciting area of research, with theorists developing models to explain how it works and experimentalists search- ing for it in a variety of materials. The researchers said these results not only dem- onstrate the value of the new RSXS approach, but also support the possibility that the PDW is present not just in this material, but in all of the supercon- ducting cuprates. (Source: SLAC National Accelerator Laboratory) Scientists Glimpse Signs of a Puzzling State of Matter in a Superconductor

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