High thermally stable hybrid materials for optical interconnects
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High thermally stable hybrid materials for optical interconnects Tetsuo Sato Nissan Chemical Industries, LTD., Funabashi, Japan.
ABSTRACT Optical materials in the optical circuit board are required to overcome soldering process. In detail, the material should not have absorption and shape changes after several tens of seconds heating at around 250 oC. For such application field, we have developed a novel organicinorganic hybrid material having a high thermal stability and low absorption at telecom wavelength. The hybrid material was designed to solvent less resin, which is free radical curable with heating at 150 oC or UV exposure at room temperature, for the sake of device fabrication activity. We demonstrated the waveguides fabrication by photolithography, and obtained high uniformity cured materials. Transparency of the waveguide sample at telecom wavelength was 0.10 dB/cm at 850 nm, 0.12 dB/cm at 1060 nm, 0.29 dB/cm at 1310 nm, and 0.45 dB/cm at 1550 nm. These values are good low attenuation for the Near-IR optical communication in optical interconnects. Without any further treatment such as post bake, the cured materials showed a high thermal stability. The temperature of 5 % weight loss was over 400 oC, and the transparency hardly changed after 1 min heating at 300 oC. In addition, the cured material showed a high refractive index of n=1.60 at 633 nm and a low curing shrinkage about 4.7 %. From these properties, the developed organic-inorganic material is expected to be beneficial for the optical interconnection such as micro lenses and optical packages.
INTRODUCTION With the resent increase in amount of computer processing, optical data transmission is expected to adopt in shorter length communications than current application field. One good example is the optical PCB (printed circuit board).1,3,4) Adoption of optical interconnects on board will bring some benefits such as lower cross talk, downsizing, lower power consumption, and thought to be one of key technologies in near future. Figure 1 shows a schematic image of the optical PCB.2) In general fabrication process, I/O devices are stabilized on the optical waveguides by optical adhesives, and then electrically connected to PCB by solder process. These optical adhesives are essential component to keep out dust from optical connections and improve coupling efficiency.
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VCSEL or PD
PCB
Optical Connections
Optical Waveguide
Figure 1. Schematic image of an optical PCB. Optical I/O devices (e.g., VCSEL or PD) are connected to PCB by solder balls, and space between I/O devices and optical waveguides are filled with optical materials to keep out dust. Though optical waveguides (glass optical fiber, plastic optical fiber, polymer waveguides, etc.) are energetically developed by many companies3), to our knowledge, optical adhesives for optical PCB are not so much in market.4) For this application field, we have newly developed an organic-inorganic hybrid polymer for optical interconnects. At the first of our development, we listed the requirement for op
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