Effects of Combining Hygro-Thermal Stress on Reliability of Plastic QFN Package
In this paper, finite element analysis (FEA) was used to evaluate the stress distribution on quad flat no-lead (QFN) packages. Different models were established, including moisture diffusion, thermo-mechanical stress, hygromechanical stress and hygro-thermo-mechanical stress models. The transient moisture absorption and desorption analysis were performed to estimate the package moisture distribution. A variety of experimental works were designed to study the hygro-thermal stress on the interface of die/mold compound and die attachment delaminaion. After the moisture preconditioning under 85℃/85％RH, it is found that the external mold compound (MC) material of package is almost fully saturated. The differential swelling that occurs between the mold compound and nonpolymeric materials leads to hygroscopic mismatch stresses in the package. The FEA results revealed that there is a significant contribution of hygroscopic swelling induced stress and an obvious effect of hygro-thermo-mechanical stress on package reliability. The experimental results also show that the hygro-thermomechanical stress under lead free reflow temperature produce considerable influence to the package integrity after moisture precondition.
Hailong Liu Shaohua Yang Guoyuan Li
School of Electronic and Information Engineering, South China University of Technology, Guangzhou 51 National Key Laboratory of Science and Technology on Reliability Physics and Application of Electron School of Electronic and Information Engineering, South China University of Technology, Guangzhou 51
国际会议
西安
英文
1059-1063
2010-08-16（万方平台首次上网日期，不代表论文的发表时间）