Reliability investigation and mechanism analysis for a novel bonding method of flexible substrate in 3D integration

A breakthrough in vertical stacking and bonding method in flexible substrates is developed and presented in this paper. Unlike current ACF and NCP approaches, which are used in most manufacturing industry, our novel stacking method uses only metal thin film as bonding material. Two different bonding material bumps are carried out in our experiment. Both show better electrical and reliability outcomes compared to current methods. Our proposed method can reach ultra-fine pitch, metal bonding without polymer material, simplified manufacturing process, better electrical performance and less reliability issues. It can be considered as a future bendable and flexible substrate stacking approach.