Effect of Material Aging on the Reliability of an Automotive BGA Device Under Temperature Cycling Test Conditions

Microelectronic packaging technology is evolving towards the use of complex structures with finer routing layers, which poses significant reliability challenges. This is especially true for stringent requirements on semiconductor devices such as AEC Grade 1 automotive applications and beyond (e.g., AEC Grade 0 and other extended mission profiles). The requirements for the stable mechanical performance of packaging materials under extreme thermal loading will significantly increase. Die attach and solder mask cracks have been observed on BGA plastic packages when subjected to component level temperature cycling stress tests between -55 and 150°C. Cracks in the bulk die attach & solder mask layer can propagate within the substrates thereby causing Cu trace cracks after 'n' no of thermal cycles leading to electrical failures. This can create challenges to meet automotive grade reliability requirements, also due to the Q006 2x readpoint requirement for copper wire. In any case, such failures can also significantly reduce the reliability margin and make it extremely challenging for such packages to meet extended mission profiles.In this paper, it will be shown that the high temperature exposure to air during thermal cycling is the primary root cause resulting in aging induced degradation and changes in material behavior significantly. This can alter the thermomechanical behavior of the encapsulated electronic components, impacting the overall package reliability. A unique characteristic of the observed aging of the "internal" materials is the access path for air or oxygen towards the interior of the package.In this study, the thermomechanical behavior of die attach, substrate solder mask with a specific core material has been evaluated under pristine and post aging conditions. Several materials have been evaluated and compared with the POR (plan of record) material set at T0 and post TC2000 preconditioning. A damage model was created using Finite Element Modeling (FEM) and the performance of various materials was compared by normalizing damage (expressed as an elastic strain energy density ESED) to the fracture toughness of each material.