Thermomechanical Challenges of 2.5-D Packaging: A Review of Warpage and Interconnect Reliability

Advanced packaging technology, also known as system scaling, bridges the gap between chip and package sizes by mounting multiple chips on a single package substrate. 2.5-D packaging utilizing a passive device has been widely adopted and showed enhanced capacity and performance. However, 2.5-D packaging presents its own challenges related to thermomechanical reliability because of the large size of the silicon interposer. This article reviews academic and industrial efforts to address the thermomechanical challenges associated with 2.5-D packaging, particularly silicon interposers, focusing on the warpage and board-level interconnect reliability. The topics include simulation and measurement methods to evaluate and predict the thermomechanical characteristics of package components, such as warpage and strain distribution, as well as fatigue and lifetime of ball grid arrays. The impacts of materials and geometrical design factors are also discussed. Finally, challenges of current approaches and outlooks are presented.