Investigations of Solder Ball Drop Reliability: BGA versus WLP
In this paper, finite element modeling is performed to investigate the mechanisms ofreliability performance for wafer level packages (WLP) compared to chip scale ball grid array (BGA) packagesunder impact or drop loading conditions. Several scenarios are defined to reveal the different mechanisms of dynamic performance in WLP and BGA packages. Global/local finite element modeling is performed with the use of the direct acceleration input (DAI) method. In the first scenario of the simulation, a WLP (ball on I/O) package is compared to a BGA package with same ball geometries when package size is fixed. The vertical compliance at the package corner balls in BGA, due to the corner ball attachment to the compliant substrate/mold compound, makes BGA producing significantly less stresses than in WLP. However, when considering the second scenario, in which the same die is packaged with BGA and WLP (ball on I/O), respectively,the size of the package in BGA has increased, which presents the opposite effect in reducing the solder ball drop reliability. In the third scenario, a copper post WLP package is studied. It is found that the horizontal compliance by the epoxy layer, which is used to encapsulate the copper posts, has released the stresses in solder balls greatly under impact loading. Package size, vertical local compliance in BGA, and the horizontal compliance in WLP, constitute the major factors in determining the reliability performance of final products. Therefore, in the last scenario, a same device is packaged with a copper post WLP and a BGA, respectively. It is found the drop performance of a WLP is comparable to a BGA package. Wafer level packages are demonstrated to have comparable or even better drop performance than a BGA package. Existing experimental data show excellent agreement with the findings and observations in this study.
Amarinder SinghRanouta Xuejun Fan
Department of Mechanical Engineering, Lamar University, PO Box 10028, Beaumont, TX 77710, USA
国际会议
上海
英文
626-631
2011-08-08（万方平台首次上网日期，不代表论文的发表时间）