Simulations and Experiments to Analyze Stress Phenomena in Soldered and Sintered Interconnections between Silicon Nitride chips and Copper Substrates

Thermomechanical stress in microelectronics packaging systems is a very complex phenomenon. Understanding of behaviours of the systems, in terms of origin, assessment and impact of the stress on an assembly, is a successful strategy to develop devices with high performances and reliability. Based on the fine element method, virtual prototypes can be investigated to simulate the thermomechanical behaviour and stress in real assemblies. Micro-Raman spectroscopy is a valid method to determine the stress distribution in a material because the perturbation due to stress can be observed as variation of wavenumber of phonon modes. In this paper, a FEM model is developed and experimental results of Raman investigations are compared to the theoretical results obtained from the model. The model and the processing approach are validated by the analysis of the stress in test assembles where $Si_{3} \mathrm{N}_{4}$ chips are bonded onto Cu substrates via AuSn-soldering, SAC305-soldering, and Cu-sintering. Compressive stress with values between 150 and 1100 MPa is determined in $Si_{3} \mathrm{N}_{4}$ /AuSn/Cu assemblies.