In the last decade, failure of microelectronic devices has become a prominent field of research all across the world. The results of this of failure analysis allow an engineer to choose package geometries and materials which reduce the risk of failure. This paper is meant to relate the stress effect on material properties during Quad Flat No-Leads (QFN) stacked-die packages manufacturing processes. To achieve the study, the finite element technique was used to perform an extensive structural analysis on a QFN package design once it was verified by related experiments. A QFN unit was developed in three dimensional geometry with various materials be will simulated in order to determine the location of failure. The induced stress results were also measured in the maximum value, indicating the low modulus and coefficient of thermal expansion (CTE) in the packaging material were important for reducing high stress during the manufacturing stages. However, numerical simulation demonstrated that the stress developments increased exponentially when the die attach temperature increased. Therefore, the induced stress can be relieved by having high die attach process temperature with an adequate bonding force and time. It was vital to control the induced stress in package materials during die attachment process for ensuring the reliability level of QFN packages.