Study on moisture behavior in flip chip BGA packages and bake process optimization

The lead-free (LF) and halogen-free (HF) ldquogreenrdquo initiatives are driving the advanced packaging manufacturers to develop new generation materials and assembly technologies. However, the moisture related reliability issues become the significant technical challenge to meet stringent reliability and quality standards comparing to the previous Lead and halogen technology. In this study, the moisture absorption and desorption performance of halogen free and lead free material were investigated. The experimental data revealed that after fully baked process there was still some resident moisture which was mainly contained at substrate level. The modeling data of moisture absorption and desorption behavior with 125degC bake comparison was discussed and was fully aligned with experimental data. Moreover, a dasiasoft bakepsila method via Nitrogen and dry air was introduced. In low RH effect test, under 25degC / 60%RH precondition process, all the moisture absorbed for 1100 hours can be removed by dasiasoftpsila bake. This indicates that not only no moisture absorption in low RH environment, but also an additional dasiasoft bakepsila process occurring during the storage time. The results demonstrated that the storage of moisture-sensitive material in the optimized environment is an attractive facility solution which can reduce the risk of popcorn and cracking problems.