FEA-based Layout Optimization of E1.S Solid-State Drive to Improve Thermal Cycling Reliability

E1.S is the family of Enterprise and Data Center Standard Form Factor (EDSFF) for NVMe Solid-State Drive (SSD), providing higher capacities and performance as well as improved power/thermal solution compared to conventional M.2 SSDs. Due to its spatial limitation and high density of NAND packages and other electrical components, however, the BGA-type packages in E1.S enclosure-type SSD suffer from low thermal cycle reliability induced by creep of solder joint, especially in the case of packages near physical constraints like screw joints. In this study, we use Finite Element Analysis (FEA) to estimate the risk of solder joint crack of NAND BGA solder balls near the screw joint in E1.S enclosure-type SSD. The plastic work per cycle on each solder was calculated by FEA and compared to the Dye-and-Pry results of the real SSD sets after thermal cycle test (- 40~85°C) to evaluate the relationship between thermal fatigue life of solder balls and the plastic work. We confirm that the mechanical restraint near the screw joint is the major cause of the reduction of the solder ball fatigue life in the E1.S SSD. Further, we suggest the optimal layout for package placement and housing design to improve thermal cycle by up to 51%, as a design rule of E1.S form factor.