The humidity and thermal characteristics of die-attach (DA) and its impact on the package reliability

In this paper, a humidity absorption test experiment is carried out under the temperature 20degC, 40degC and 60degC respectively and the environmental humidity was changed in different modes in each case. The experimental sample is from material of DA, and it is 14.5times5.5times0.37 mm³ in size, and 94.4 mg in weight. The experiment data are collected to gain the saturated moisture. The moisture diffusion coefficient (D) of the sample can be calculated by fitting the line of data curve and calculating the slope of the line. The constants (Q_D and D₀) which are in the Arrhenius formula are worded out by using the D [1]. In order to analyze the failure model in the interface between DA and die pad, a new type of system-in-package (SiP) is modeled. The simulation environments are set as the conditions of stored in the room temperature and processed in the SMT assembly production line. The analysis aim is to calculate the humidity distribution and the hygroscopic and thermal stress in these conditions. The results of FEM analysis shows that the max hygromechanical and thermo-mechanical stress appear in the corner of the interface between the Die and the DA, and the corner may be the risk location. The delamination may occur in this place. So it is necessary to analysis the reliability of the interface between the DA and others materials.