High power transistor, laser, and LED devices require packaging to remove thermal energy from the die. Although some silver filled epoxies provide thermal conductivity approaching 60 W/mK, AuSi and AuSn solder have long proven superior thermal performance. Materials such as Si and GaAs on CuW and GaN on SiC will be discussed in three case studies for die sizes ranging from 12 x 21 x 4 mil thick to 453 x 274 x 12 mil thick, using AuSi or AuSn eutectic die attach processes. The cases provide an overview of material selection and methods for optimized utilization of eutectic solders. Bond quality metrics such as fillet, voiding, and shear will also be covered in this paper.