Unique approach to materials allows temperature-stable circuits

Sandia National Laboratories researcher Steve Dai jokes that his approach to creating materials whose properties won't degenerate during temperature swings is a lot like cooking - mixing ingredients and fusing them together in an oven.

Sandia has developed a unique materials approach to multilayered, ceramic-based, 3-D microelectronics circuits, such as those used in cell phones. The approach compensates for how changes due to temperature fluctuations affect something called the temperature coefficient of resonant frequency, a critical property of materials used in radio and microwave frequency applications.

Sandia filed a patent for its new approach last fall. The work was the subject of a recently completed two-year 'early career laboratory directed research and development' (LDRD) project that focused on understanding why certain materials behave as they do. That knowledge could help manufacturers design and build better products.

''At this point we're just trying to demonstrate that the technology is practical,'' Dai said. ''Can we design a device with it, can we design it over and over again, and can we design this reliably?''

The familiar cell phone illustrates how the development might be used. The Federal Communications Commission allocates bandwidth to various users - aviation, the military, cell phones, and so on. Each must operate within an assigned bandwidth with finite signal-carrying capacity. But as temperatures vary, the properties of the materials inside the phone change, and that causes a shift in the resonant frequency at which a signal is sent or received.

Because of that shift, cell phones are designed to operate squarely in the middle of the bandwidth so as not to break the law by drifting outside their assigned frequency range. That necessary caution wastes potential bandwidth and sacrifices higher rates at which data could move.