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|Numerical Analysis of Moisture Induced Failure in Semiconductor Package|
|Keywords: reliability, hygroscopic swelling, numerical simulation|
|In recent years many studies to demonstrate the physical phenomena related with moisture induced delamination, such as moisture diffusion, hygroscopic swelling, and interface delamination, have been published. Especially fracture mechanics based delamination modeling methodology has been proposed in several publications. Based on this methodology, crack propagation of initial small crack can be simulated. However, a unified numerical study about package warpage due to CME (Coefficient of Moisture Expansion) mismatch, resulting local stress concentration along the damaged interface, and qualitative life prediction has not been performed. In this paper, a unified simulation methodology based on FEM is proposed to predict package reliability under hot and humid condition. The unified methodology is composed of two parts : diffusion analysis part and structural analysis part. In the diffusion analysis, moisture flow rate in the package is obtained and resulting moisture concentration is stored at each integration point. In the following structural analysis, warpage due to hygroscopic swelling and local stress concentration is calculated based on the previous moisture concentration variation. In order to calculate local stress concentration due to CME mismatch, specially designed user defined subroutine is developed. The newly proposed numerical method is applied to predict the failure time of BOC package under reflow with moisture precondition (85¨¬C/85%RH). Material properties, such as diffusivity, solubility, CME, and interface strength are measured. The comparison between the numerical prediction and experimental results shows that the newly proposed method can successfully predict the damage evolution in the package.|
|Joonyoung Oh, Senior Engineer
Samsung Electronics Co.
Hwasung, Gyeonggi 445-701 ,