Moisture absorption and autoclave performance optimization of glob top ball grid array

Abstract

The glob top BGA has been pursued by multiple companies to reduce package cost and cycle time. This report discusses material and process improvements that can be made to enhance the packages' performance to a JEDEC Level 3. The material evaluations included in this report tested different liquid encapsulants, die attach epoxies and solder resist materials. Process improvements targeted using different cure profiles for the encapsulants, cleaning processes and location of special cleaning in the assembly process. Flag designs that reduce Cu surface area on the substrate for possible better die attach adhesion are also discussed. These results are benchmarked with the overmolded plastic ball grid area (PBGA) performance which is a JEDEC Level 5. The reliability test response was C-SAM to inspect for delamination at various package interfaces and weight gain to determine package moisture absorption and deabsorption rates.