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70 The PCB Magazine • December 2017 THE POWER OF FLEX had a wire that was visible to the patient. Al- though the medical device was working perfect- ly, patients' perception of and confidence in the procedure was not high. This was traced back to patients not being comfortable with the percep- tion of the wire. That simple wire was replaced with a very simple flexible circuit, so simple, there were only two traces. But, by making this simple change, the patients' perception and confidence in the medical device skyrocketed. Polyimide is also bio-compatible. Most of- ten, the polymide material is fully encapsulated before being inserted into the body. New devel- opments are exciting. Polyimide laminate with gold, rather than copper traces are fully bio- compatible and being tested as sensors to be implanted into the human body. This develop- ment is also aided by additive technology that allows trace size in the 5- to 10-micron range, significantly shrinking the package size as well. There are exciting things on the horizon. Intrinsically More Reliable and Reduced Opportunity for Operator Error Flexible circuits can significantly simpli- fy the system design by reducing the number and levels of interconnection required. Because the design is controlled by the artwork, the op- portunity for human error is eliminated. Aero- space is great example. Spacecraft are subject- ed to many kinds of dynamic forces, especially during take-off. In traditional PCBs these vibra- tions contribute to failure. Rigid-flex circuits are made to twist and flex and are a benefit in these harsh environments. Solder joints, crimps, etc., are also at risk for failure in these conditions. Flexible circuits can remove this concern by eliminating connections. Yes, our industry has developed so many in- teresting, life-enhancing and life-saving prod- ucts and for that we should all be proud to be a part of the growth in this market. To finish the story I started earlier, this little boy emerged from the field, a little tired, very muddy and mostly angry that he still had not found his puppy. Guess what. The person stationed at the edge of the field that spotted him was able to notify his parents and the command center immediately with his cellphone, which, you guessed it, also contains a flexible circuit. PCB Tara Dunn is the president of Omni PCB, a manufacturer's rep firm spe- cializing in the printed circuit board industry. To read past columns or to contact Dunn, click here. While most consumers don't pay much at- tention to the fate of dead smartphones, Prince- ton University researchers are envisioning a way to breathe new life into them. Instead of tossing old phones in a junk drawer or burying them in a landfill, the researchers want to turn them into high-powered computer servers. In a recent paper, graduate student Mo- hammad Shahrad and David Wentzlaff, an as- sistant professor of elec- trical engineering, dem- onstrated that it is pos- sible to build servers out of ranks of old smart- phones. Servers are specialized computers that provide data, storage or computing power to other computers. The research showed that not only are smartphone servers feasible, they are often cheaper to build and operate than conven- tional high-end servers. In part, this is a result of supply costs. "You can get decommissioned smartphones at low cost because used phones are inexpensive and no one else wants them," Wentzlaff said. The researchers said that reusing smartphones not only makes economic sense, it is a good environmental policy. Electronic waste, of which smartphones play a substantial part, is a growing concern worldwide. Old Phones Get New Life in High-Powered Computer Servers