Assessment of Thermal Fatigue Reliability in 3D Integrated TSV and Solder Joint Structures Under Oil-Immersion Cooling

The growing demand for higher computational efficiency in data centers and AI hardware is accelerating the adoption of 3D heterogeneous integration and immersion-cooling technologies. Oil immersion offers significantly enhanced heat dissipation compared to conventional air cooling, improving thermal stability and enabling higher power densities. However, the thermo-mechanical environment created by oil immersion also introduces new reliability challenges. In 3D packages, mismatches in material properties like Coefficient of Thermal Expansion (CTE) and Elastic Modulus (E) can induce interfacial stresses that lead to through-silicon via (TSV) cracking, printed circuit board (PCB) warpage, and solder-joint fatigue failures. This study investigates the influence of oil-immersion cooling on the thermomechanical reliability of solder joints and TSV structures in advanced 3D packages. Plastic strain accumulation in solder joints under extreme thermal cycling is analyzed to evaluate the likelihood of crack initiation and propagation. Additionally, J-integral computations are performed to quantify crack-tip driving forces in TSVs across different PCB configurations, providing a comprehensive assessment of package lifetime reliability. To further enhance TSV resilience, this work examines alternative via–fill materials–including tungsten, silver, nickel, carbon nanotubes, aluminum, molybdenum, gold, graphene, and annealed copper which are possible alternatives-and compares their crack-propagation tendencies using J-integral–based metrics. Overall, this research not only identifies reliability risks associated with oil-immersion environments but also proposes material–level mitigation strategies.