Mechanical reliability issues in electronic package have drawn significant attention in semi-conductor industry for decades and have increased product development cost significantly. Recent rapid growth of various portable electronic devices like netbook and smartbook with increasing demand for more functionality in tighter space further challenges the limit of mechanical reliability. To reduce the product development cost and time-to-market, mechanical simulation has been extensively employed across semiconductor industry for the purpose of design optimization and reliability assessment. The importance of having the correct simulation methodology can?ˉt be overemphasized considering the extent of its utilization throughout the whole product development cycle. In this paper, we will discuss three fundamental mechanical modeling methodologies that are widely used for flip-chip overmolded packages in the industry. The first approach is to assume whole package is stress-free initially at a given uniform temperature, which is usually the peak temperature of the mold cure profile. However, this differs from the actual assembly process where reflow or cure temperature profiles are different at each process step. The second approach takes that into account and assigns different initial stress-free temperature to different package component. The last approach explores that idea further by simulating the actual assembly process, step by step through element removal and addition in the model. Details of each procedure are outlined in the paper. Package End of Line (EOL) warpage predictions from these models on a real device are compared and validated with shadow or data. Reliability assessment regarding different failure mechanism based on these three modeling methodology is also included. Finally, we will share our recommendation and highlight the advantage/disadvantage of each modeling methodology. These statements do not reflect opinions from Qualcomm Inc. All data shared in this paper will be screened such that no confidential information is published or presented.
展开▼
