Fabrication Methods for SU-8 Optical Interconnects in Plastic Substrates

Buried optical interconnects promise high speed interconnections between electronic circuits on circuit boards. Previous attempts have relied on expensive microfabrication technologies and complex optical coupling systems. The circuits in plastic (CiP) manufacturing method has electronic components embedded in a plastic substrate making direct optical coupling possible. Four different machining methods were used to create optical waveguides in polymethyl methacrylate (PMMA) substrate and with SU8 channel, covered with a thin sheet of PMMA. A three-layer milling technique showed least attenuation (1.17 and 1.20 dB/cm at 1310 and 1550 nm, respectively). The technique shows significant promise for low cost fabrication of CiP with optical interconnects.