Thermal and thermo-mechanical behavior of silicon platform with direct lead attachment

Miniaturization, low cost, and high performance are the trends in optical data link device packaging markets. Low cost, miniaturization, and high performance are achieved by reduction in the number of piece parts, process and assembly steps by populating the platform directly with piece parts without compromising package performance. Performance is a function of the packaging material. Maximizing the heat dissipation in the package (T_j⩽T_jmaxand T_jmin<T_j<T_jmax) and minimizing the effects of the temperature differences among the structural components (σ=E αΔT) enhances performance. Both the heat dissipation and the effect of temperature differences are functions of the material(s) used in the packaging. This paper discusses the thermal and thermomechanical results obtained by bonding different electrical lead materials directly on to a silicon platform. We will review the contributions of different solder materials as bonding agents. We will show that thermo-mechanically, Kovar leads exhibit less thermal stresses when solder bonded to silicon, but are thermally non-compatible due to the large difference between their thermal conductivity coefficients. We will also show that copper leads solder bonded to a silicon platform with AuSn solder causes the silicon to fracture. Finally, we show that Cu-W leads provide the best compromise for heat dissipation and stress minimization