Enhancing Reliability of Multi-Chip Modules by Using the Reinforcement Mechanisms of Side-Fill Technology

With increasing reliability requirements for automotive electronics, reinforcement structures have become essential for enhancing the durability of automotive modules. The underfill process is widely used to mitigate thermal-mechanical stress exerted on solder joints during reliability tests. To address the limitations of underfill, including process complexity, material usage, non-reworkability, and the potential for voids caused by capillary flow. This study proposes an alternative side-fill reinforcement structure using in automotive multi-chip modules (MCM), where the adhesive material is dispensed along the edges of ball grid array (BGA) components. In this study, non-linear finite element analysis (FEA), combined with an equivalent material approach, is employed to evaluate the reinforcement mechanisms for enhancing solder joint reliability under various side-fill configurations. The simulation results show that applying 2 U side-fill pattern in wafer level chip scale packaging of MCM can reduces the increment of stabilized equivalent plastic strain under thermal cycling tests (TCT) by approximately 57% compared to none of any adhesive. The side-fill structure exhibits a significant reinforcement effect by redistributing thermal stress during thermal cycling. The thermal stress, initially concentrated within the solder balls, is transferred to the four corners where the side-fill material interfaces with the chip. This indicates that the side-fill structure effectively absorbs and mitigates thermally induced stress, thereby enhancing the overall reliability of the package. Side-fill technology has provided a more efficient and cost-effective solution for mechanical reliability in automotive applications.