Package design optimization and materials selection for stack die BGA package

Due to an expanding consumer electronics market and the need for form factor reduction, stack packages have been gaining popularity in the last 3 years. With the incorporation of silicon die stacking, there is a corresponding increase in biomaterial coupling and interfacial adhesion becomes a prime reliability under the exposure of both moisture and thermal excursion. With the requirement for higher solder reflow temperatures for lead-free applications, the problem becomes even more severe. It becomes increasingly important to understand the combined effects of material selection and package structure on the interfacial delamination under temperature excursion in the presence of moisture. This paper presents a detailed analysis into the effects of packaging materials and structure on interfacial delamination under temperature excursion in the presence of moisture for two die stack fine pitch BGA (D2-FBGA). Upfront analysis based on thermo-mechanical modelling is performed prior to a full design of experiments (DOE) investigation. The current DOE matrix includes variation in mold compound delamination and other test factors such as geometrical variations in die stacking and the selection of mold compound influence the intensity of delamination.