Design For Board Level Reliability Improvement In EWLB (Embedded Wafer Level BGA) Packages
Authors: Won Kyoung Choi, Yaojian Lin, Chen Kang, Seng Guan Chow, Seung Wook Yoon, and Pandi Chelvam Marimuthu Company: STATS ChipPAC LTD Date Published: 10/3/2011
IWLPC (Wafer-Level Packaging)
Abstract: eWLB (Embedded Wafer Level BGA) is one of key advanced packages because of advantages of higher I/O density, process easiness and integration flexibilities. It facilitates integration of multiple dies vertically and horizontally in one package without using substrates. Thus, recently eWLB development is moving forward to the next generation packages of 3D integrations to meet the market demands. eWLB consists of diverse materials and structures built in a reconstituted wafer. As the volume gets increased, structural design as well as selection of materials becomes more important in determining process yield and long term reliabilities. Therefore it is necessary to investigate the key design factors affecting the reliability comprehensively. In this paper, the influences of materials characteristics and structural designs on the board level reliability will be demonstrated. Since the requirements for improving performances of drop and thermal cycling on boards are sometimes in trade-off, it is important to find the optimal design parameters to meet both reliability performances. Therefore, the constructive analysis has been performed by going through every design factor both in a component level and in a board level. And the reliability study was carried out in depth by experimental approaches as well as through thermo-mechanical simulations. As a result, the most influential factors for the reliability turned out to be relevant to the solder joint design, such as solder compositions and dielectric mechanical properties. On the other hand, the different structural design allows to prolong the life by giving more resistance to the crack propagation and also to make the entire package body more flexible.