Photonic PCBs demonstrated

February 06, 2013 // By EE Times
A team of researchers from IBM and Dow Corning Electronics is claiming a breakthrough that could enable silicone to supplant copper for creating fast, energy efficient photonic interconnects on printed-circuit boards (PCBs). The team demonstrated optical waveguides using a photonic polymer at Photonics West 2013 on Monday (February 4).

IBM claims its collaboration with Dow Corning provides an integrated approach to optical interconnects, similar to how metal PCB traces route electrical signals around inside computers today. The polymer waveguides are "highly flexible and resistant to high temperatures," said Bert-Jan Offrein, manager of the Photonics Research Group at IBM Research (Zurich). Offrein said no curling or deformation was incurred for bends as tights a 1 millimeter, and for extreme operating conditions of 85 percent humidity and 185 degrees Fahrenheit.

Silicone makes uses of the same basic element as CMOS chips--silicon--but in a flexible form that can transmit light around the bends and turns with very little distortion. As a result, extremely fast and energy efficient photonic interconnects can be fabricated that are capable of carrying the exabytes of data needed for future data centers and supercomputers.

Eric Peeters, a vice president at Dow Corning Electronic Solutions, predicted that the new material will enable "silicone-based board-level interconnects that quickly supersede conventional electronic signal distribution methods."

Flexible photonic waveguide made from Dow-Corning silicone material in IBM's Binnig and Roher Nanotechnology Center (Rueschlikon, Switzerland).

The silicone polymer starts as liquid, like other optical materials such as glass, but can be dispensed under normal atmospheric conditions, solidifying in less than 45 minutes. The material also showed excellent adhesion to conventional PCB materials like polyimide, had losses as little as .03 dB per centimeter, was stable for over 2,000 hours at high temperature/humidity, and survived 500 thermal cycles between -40 and 248 degrees Fahrenheit.

The Photonics West presentation, "Stable and Easily Processable Optical Silicones for Low-Loss Polymer Waveguide" was presented by Brandon Swatowski, an application engineer at Dow Corning Electronics Solutions. Photonics West is taking place this week in San Francisco.