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42 The PCB Design Magazine • December 2015 • The power and ground grid configuration is the best approach for providing power delivery on double sided boards. • Solid copper planes are a much better solution for high-speed design. • At high speeds, return currents flow the path of least inductance which tends to direct the current directly below the signal trace. • At high frequencies, a plane in a PCB is really two conductors, not one conductor, due to the skin effect. • Any voltage drop across a ground plane will excite cables terminating on the board, which causes them to radiate as dipole or monopole antennae. • Above 10MHz, multilayer PCBs with at least two plane layers should be seriously considered. • Multilayer boards reduce radiated emis- sion by more than 10 db compared to a double-sided board. PCBDESIGN References 1. Barry Olney Beyond Design Columns: There are no One-Way Trips, The Dumping Ground, Losing a Bit of Memory, Stackup Plan- ning 1-4. 2. Henry Ott, Electromagnetic Compatibil- ity Engineering. 3. Howard Johnson, High-Speed Signal Propagation. 4. Hashimoto & Nair, Power Integrity for Nanoscale Integrated Systems. 5. The ICD Stackup and PDN Planner, www. beyond design PLANE CRAzY, PART 1 Barry olney is managing director of In-Circuit Design Pty ltd (ICD), Australia. This PCB design service bureau specializes in board-level simulation, and has developed the ICD Stackup Planner and ICD PDN Planner software. To read past columns, or to contact olney, click here. Researchers at the university of Twente re- search institute MeSA+ have devised an elegant method for fitting various functional coatings to silicon microwires. The research has been pub- lished today in the prestigious scientific journal Advanced Materials. Microwires made of the semi-conductor sili- con are used in numerous fields. It is generally necessary to 'functionalize' them, by adding a lay- er of metal or a layer of a cata- lyst. In most cases, the wires are given a single layer, but in specific instances it is useful to put a different material on the bottom and on the top of the wires. However, creating these wires proved very dif - ficult and the process of making them involved many steps. Researchers from the university of Twente have now developed a new method that makes creating wires of this kind easy. According to university of Twente Professor Jurriaan Huskens, this has provided chemists with a versatile method for creating new materials. In their experiments, the university of Twente researchers first made microwires with a PN junc - tion halfway along the wires. In the experiment, the wires were submerged into a solution contain- ing platinum in the dark, causing the 'P side' of the wire to be covered in platinum. In the next stage, silver was added to the other side in the light. The result was a mi- crowire with silver on the top and platinum on the bottom. The wires can be very valu- able for the purpose of gen- erating energy from sunlight or purifying water with the help of sunlight. University of Twente Develops Versatile Method for Developing New Materials

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