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Design007-Apr2018

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APRIL 2018 I DESIGN007 MAGAZINE 57 may result in nonfunctional boards being built successfully, tested and shipped. Care should be taken to not assign net points to things that should not be electrical nets, such as non-plated holes or targets. Before any fabrication edits have been performed, a netlist compare is performed. Any known or otherwise intentional shorts or opens should be noted on a "read me" file Word document or on the drawing itself. For example: "AGND to DGND short net000 is intentional by design." Then, after any manufacturing edits such as drill compensations or etch compensa- tions are performed, the netlist is run again to ensure the fabricators has not created any electrical anomalies. Some of the most com- mon netlist types for fabrication are IPC D356, IPC D356A and a Mentor neutral file. Lastly, any specific panelization require- ments such as the addition of text for part marking, fiducials of a specific size, or sub- panel tooling of a specific size should be negotiated with the fabricator prior to quote. If no sub-panel drawing can be provided, you will want to, at the very least, indicate to a board fabricator areas of either part overhang or feature proximity where you DO NOT wish frame tabs to be located. This will keep you from having to go back into CAM to move tabs or add cutouts in the frame. Conclusion PCB fabricators are basically an extension of our customers, and for this relationship to be successful both sides need to work collab- oratively. It all starts with the output package. Following these guidelines is the critical first step to assuring product quality and reliability. As I've said before, your best bet is to communicate with your fabricator early on. DESIGN007 Mark Thompson is in engineering support at Prototron Circuits. Gold Changes the Photoluminescence of Silicon Quantum Dots Silicon quantum dots have a wealth of potential applications in cell biology and medicine thanks to their selective cell penetration capability and luminescence. Biosensors based on silicon quantum dots can be used as an early diagnosis tool for various diseases, while silicon nanocrystals hold great potential for develop- ing silicon-based light-emitting devices and producing highly efficient solar cells. Scientists from the theoretical nanophotonics team led by Skoltech Professor Nikolay Gippius jointly with researchers from Moscow State University and the Royal Institute of Technology (KTH) in Stockholm dem- onstrated that gold nanostripes are capable of chang- ing the extinction and photoluminescence spectra of silicon nanocrystals. The researchers' findings are of particular value for practical applications of silicon nanocrystals, as they provide scientists with a novel tool for controlling the quantum dots' properties. Inter- estingly, the use of silicon quantum dots in photocells would significantly reduce technical losses in the solar power industry and help to avoid using arsenic, lead and other toxicants in solar cells production. "Derived from the interaction between a sample of silicon quantum dots and gold nanostripes is a quasi- particle called the 'waveguide plasmon polariton.' This leads to a change in the optical properties of silicon nanocrystals. If we wish to use them in solar batteries or light emitters, we should have a metal electrode and know how to control the extinction and emission spec- tra. Gold nanostripes are a solution to both issues," said Sergey Dyakov, the main author of the study and a Skoltech researcher.

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