A study on the characteristic of UV curved die-attach films in stack CSP (Chip Scale Package)

In this paper, a study on the relationship between UV cured die-attach film (UVDAF) characterizes, process design, and the failure mechanism of reliability test were reported. The novelty films were a multifunctional tape, which consists of the function for dicing tape and die bonding tape. It focused on investigation of the behavior under the JEDEC level 3 precondition conditions, pressure cook test (PCT) and thermal cycle test (TCT). Besides, the paper discusses the thermal history effect on the chemical stability of UVDAF for the reliability issue. For instance, initial crosslinkage temperature of UVDAF affect on effectually contact area after the die-mount process. The cure kinetic and thermal resistances of the UVDAF were analyzed by Differential Scanning Calorimetry (DSC) and Thermo gravimetric Analysis (TGA). The delamination surfaces were analysis by Scanning Acoustic Tomograph (SAT), Cross-section were scanned by electronic microscopy (SEM) and Optical Microscope (OM). The thermo-deformation and pressure-induced flow behaviors of UVDAF were evaluated by both penetration mode in Thermal Mechanical Analyzers (TMA) and dynamic mode in rheology test, respectively. Furthermore, OM and SEM results revealed that the chemical stability of UVDAF in process, from die-mount to molding, affect the final effectually adhesive area that obviously influenced the quality of stack CSP reliability.