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26 The PCB Design Magazine • December 2014 Charles Pfeil is an engineering director in the systems Design Division at Mentor graphics. He was the original product archi- tect for Xpedition PCB and an inventor of XtremePCB. Pfeil has been in the PCB industry over 40 years as a designer, owner of a service bureau, and has also worked in marketing and engineering management at racal-redac, asI, Cadence, PaDs, and veriBest. To contact him, click here. Happy Holden has been working with printed circuits in various capacities since 1970. He retired from Hewlett-Packard after nearly 29 years, and was senior PCB technologist for Mentor graphics' system Design Division. Happy also served as a senior technologist with Foxconn and gentex before retiring, finally, in 2013. He's currently working with Clyde Coombs on the 7 th edition of the PCB Handbook, due out in mid-2015. To contact him, click here. • The skip via reduces laminations and plating steps, which lowers cost; however, this contributes to a relatively low route density. Stackup E comments: • The via models are simple and it won't be difficult to find vendors who can fabricate it. • The lack of a GND plane on the outer layers reduces power and signal integrity; however, it does provide for improved route density assuming routing would be done on the outer layers. Stackup F comments: • The GND plane on the outer layers provides the high rating for power and signal integrity. • The extended buried via reduces lamination and plating steps, which lowers cost; however, it also reduces route density. Stackup G comments: • The GND plane on the outer layers provides the high rating for power and signal integrity. • The extended buried via and the skip via reduces the lamination and plating steps which lowers cost; however it also reduces route density. PCBDESIGN HDI LAYER STACkUPS FOR LARGE, DENSE PCBS continues feature by Real Time with... NEPCON South China a team of engineers and scientists has identi- fied a source of electronic noise that could affect the functioning of instruments operating at very low temperature. The findings, detailed in the journal na- ture Materials, could have implications for the future design of transistors and other electronic components. The electronic noise the team iden- tified is related to the temperature of the electrons in a given device, which in turn is governed by heat transfer due to packets of vibrational energy, called phonons, that are present in all crystals. "a phonon is similar to a photon, which is a discrete packet of light," says austin Minnich, an assistant pro- fessor of mechanical engineering and applied physics in Caltech's Division of engineering and applied sci- ence and corresponding author of the new paper. one way that engineers have traditionally re- duced phonon scattering is to use high-quality materials that contain as few defects as possible. a more common solution, however, is to operate electronics in extremely cold condi- tions because scattering drops off dra- matically when the temperature dips below about 50 kelvins, or about -370 degrees Fahrenheit. "We don't know what the precise strategy will be yet, but now we know the direction we should be going. That's an improvement." Noise Floor for Ultrasensitive Electronics Identified

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