Thermal fatigue life simulation on DDR3 package

Abstract

For high memory density DDR3 BOC packages with thin copper foil thickness, module level solder joint reliability during the thermal cycling test is a critical issue. In this paper, 3D FEA thermal fatigue life models are established and analyzed with detailed considerations of pad design, realistic geometry of solder joint and nonlinear material properties. The validated models have the capability to predict the fatigue life of solder joint during the thermal cycling test within µ25% error against in-house test data. Simulation shows that the high density DDR3 fatigue life is 63% lower than DDR2. Under worst case condition, there is a possibility that the package will failed to meet Micron reliability performance. Therefore, parametric studies are performed to enhance the fatigue life performance through 10 factors, consist of key package dimensions and material properties. To enhance the solder joint reliability of DDR3 BOC package, it is recommended to have a thinner die and core thickness, a higher solder joint standoff height and a thicker copper thickness. Furthermore, the solder joint reliability can be greatly improved by choosing a mold compound physical property with matching CTE to the board and interposer. To match and exceed the SJR of 22um using 13um copper thickness, a combination of several design and material factors are needed.