Quad Flat No-Lead or QFN is able to provide lighter, thinner and higher performance packaging requirement with its exposed pad and leads at the package bottom for better heat dissipation. However, QFN packages possess certain weaknesses. QFN package failures are related to crack and delaminating, such as die cracking, moulding compound and solder mask interfacial delaminating. From previous projects, the epoxy thickness and die thickness plays an important role in reducing failures in QFN package. The objective of this project is to observe the effects of die and epoxy thickness. The effects on QFN are measured in the die and lead frame part. Stress towards the die is also measured: including thermal, first principle and Von Misses stress. The structural optimization is based on the Finite Element Analysis (FEA). By using ANSYS 10.0, six models were constructed, where three models were built to analyse in thickness of epoxy, and another three to study the effects on die thickness. The effect was measured by the value stress (first principle stress and Von Misses stress) and thermal strain effect, which will lead to a result of how the dimensions of the packaging will give a better tolerance towards stress.