Fabrication of Polymer Waveguides by Laser Ablation Using a 355 nm Wavelength Nd:YAG Laser

The demand for optical waveguides integrated into Printed Circuit Boards (PCBs) is increasing as the limitations of copper interconnects for greater than 10 Gb/s data rates are being reached. Optical polymer materials offer a good solution due to their relatively low cost and compatibility with traditional PCB manufacturing processes. Laser ablation is one method of manufacture, for which excimer lasers have been used, but UV Nd:YAG (Neodymium-doped Yttrium Aluminium Garnet) lasers are an attractive alternative due to their widespread use within the PCB industry for drilling vias. In this paper, 355 nm, 60 ns pulse length UV Nd:YAG laser ablation of Truemode™ acrylate-based optical polymer was investigated. The UV Nd:YAG laser was found to be able to ablate the polymer efficiently and the effects of laser ablation power and pulse repetition frequency (PRF) on depth of ablation were studied and used to determine preferred settings. 45 μm × 45 μm multimode optical waveguides were fabricated to demonstrate the process and optical loss measurements were carried out. These measurements demonstrated that the structures were able to transmit light at the data communications wavelength of 850 nm (NIR), but further work is required to reduce the level of loss. The use of UV Nd:YAG as a possible alternative to excimer for laser micromachining would facilitate the rapid deployment of the optical technology within the PCB industry

Integrated optical and electronic interconnect PCB manufacturing research

Purpose – The purpose of this paper is to provide an overview of the research in a project aimed at developing manufacturing techniques for integrated optical and electronic interconnect printed circuit boards (OPCB) including the motivation for this research, the progress, the achievements and the interactions between the partners. Design/methodology/approach – Several polymer waveguide fabrication methods were developed including direct laser write, laser ablation and inkjet printing. Polymer formulations were developed to suit the fabrication methods. Computeraided design (CAD) tools were developed and waveguide layout design rules were established. The CAD tools were used to lay out a complex backplane interconnect pattern to meet practical demanding specifications for use in a system demonstrator. Findings – Novel polymer formulations for polyacrylate enable faster writing times for laser direct write fabrication. Control of the fabrication parameters enables inkjet printing of polysiloxane waveguides. Several different laser systems can be used to form waveguide structures by ablation. Establishment of waveguide layout design rules from experimental measurements and modelling enables successful first time layout of complex interconnection patterns. Research limitations/implications – The complexity and length of the waveguides in a complex backplane interconnect, beyond that achieved in this paper, is limited by the bend loss and by the propagation loss partially caused by waveguide sidewall roughness, so further research in these areas would be beneficial to give a wider range of applicability. Originality/value – The paper gives an overview of advances in polymer formulation, fabrication methods and CAD tools, for manufacturing of complex hybridintegrated OPCBs. © 2010, Emerald Group Publishing Limite