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December 2014 • The PCB Magazine 37 The Japanese suppliers for module sub- strates remain at the top of the food chain in the global market for semiconductor pack- aging thanks to Intel. Intel recognized that Japanese manufacturers are the most reliable partners, and they continue to use them as an approved vendor. Unfortunately, some new competition from Taiwanese and Korean manufacturers will force the Japanese to low- er their margins in the near future. Japanese PWB manufacturers forecast negative growth over the next four years from their traditional product line. The manufacturers are trying to generate business opportunities in new areas such as automobiles, medical devices, health care equipment and more. This could still take a few years to recognize any substantial business. PCB JAPAN'S PWB MARkET—2015 continues dominique numakura is managing director of dKn research llc. 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 temperatures, such as radio telescopes and advanced physics experiments. the findings, detailed in the november 10 is- sue of the journal nature materials, could have implications for the future design of transistors and other electronic components. the electronic noise the team identified is re- lated 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, which are pres- ent in all crystals. "a phonon is similar to a photon, which is a discrete packet of light," says austin minnich, a corre- sponding author of the new paper. "in many crystals, from ordinary table salt to the indium phosphide crystals used to make transistors, heat is carried mostly by phonons." how swiftly and efficiently phonons ferry away heat from electronics is partly dependent on the temperature at which the device is operated. one way that engineers have tradi- tionally reduced phonon scattering is to use high-quality materials that contain as few defects as possible. "the fewer defects you have, the fewer 'road blocks' there are for the moving phonons," minnich says. a more common solution, however, is to op- erate electronics in extremely cold conditions because scattering drops off dramatically when the temperature dips below about 50 kelvins, or about –370 degrees Fahrenheit. "as a result, the main strategy for reducing noise is to operate the devices at colder and colder temperatures," minnich says. but the new findings by minnich's team suggest that while this strategy is effective, an- other phonon transfer mechanism comes into play at extremely low temperatures and severely restricts the heat transfer away from a device. Heat Transfer Sets Noise Floor for Ultrasensitive Electronics

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