Bonding Semiconductor Laser Chips : Substrate Material Figure of Merit and Die Attach Layer Influence

The coefficient of thermal expansion (CTE) and the thermal conductivity are the two key parameters to consider when selecting a particular substrate material for a die bonding process. We will discuss here a model to determine the substrate material giving the best chip reliability expectations for GaAs and InP laser chips. In that respect, a comparison of the thermo-mechanical stresses induced during the soldering process of GaAs and InP semiconductor chips on different substrate materials used in optoelectronic packaging is presented. In parallel, the thermal resistances of the material stacks under consideration are evaluated. The comparison of the substrate materials is based on the evaluation of failure rates for two chip failures mechanisms. We will show that CuW is the best candidate for bonding GaAs lasers chips. In the case of InP chips, the AlN submount offers the best performances.