Fracture phenomena induced by Front-End/Back-End interactions: Dedicated failure analysis and numerical developments

Related to Front-End/Back-End compatibility problematic, a systematic scheme to investigate and solve mechanical concerns is described: numerical study coupled with experimental failure analysis is proposed. Observations on Ball Grid Array (BGA) packages show that a reproducible failure mechanism appears within the low-k layers. Mechanical modeling is then used to reproduce and forecast this phenomenon. To define the most suitable method to be implemented, i.e. which combines accuracy and little arduousness, benchmark of two numerical failure criteria is performed: the widely known Cohesive Zone Method and an in-house developed Nodal Release Energy method. This latter has the higher easiness of use and implementation, especially in complex three dimensional architectures. Using this criterion, good correlation with the crack features experimentally observed is found near the die corner. Additional trends are drawn to depict and explain the crack behavior within the die. Finally, a trustful and benchmarked simulation frame, validated by experiments, brings key advantages for new product introductions, low cost development and optimized cycle time.