Optical, thermal-strain, and water-sorption properties of plastic resins for laser-diode molding

We studied the epoxy and silicone resins used for the plastic packaging of laser-diode (LD) modules with regard to their temperature dependence of the refractive index, stability at high temperature in a very humid atmosphere , contraction strain during the thermal curing process, temperature depende nce of the thermal strain, and water sorption. We found that these resins h ave refractive index temperature coefficients on the order of 10(-4)/deg, a nd that there is no variation in the refractive index in an 85 degrees C, 8 5% RH atmosphere. Moreover, the epoxy resins exhibited a thermal contractio n strain of about 0.1% and a thermal strain temperature coefficient of abou t 10(-6)/deg. With silicone resins, there is negligible strain resulting fr om thermal curing or temperature variation. Furthermore, we have determined that the moisture diffusion and permeability coefficients are, respectivel y, three orders and one order of magnitude smaller in the epoxy resin than in the silicone resin. (C) 1999 Scripta Technica.