Experimental and FEM studies have been under-taken in order to characterize the non-Fickian behavior of moisture absorption, temperature-dependent residual moisture content and hygroscopic swelling of epoxy molding compounds exposed to moist environments. Moisture absorption and desorption tests of two molding compounds and two IC packages using these materials have been carried out by gravimetric methods. Finite element analysis has been performed to simulate the anomalous dual-stage moisture absorption. To consider the residual moisture remaining in the package after the desorption process, a simple method has been developed, which allows for consideration of bake-out conditions and provides much more flexibility, enabling calculation of the non-Fickian moisture desorption with a specific residual moisture content. The Coefficient of Moisture Expansion (CME) has been also measured by coupling the results of Thermal Mechanical Analyzer (TMA) and Thermal Gravitational A nalyzer (TGA) at different temperatures. It has been shown that the moisture desorption model of this study can be used as an alternative for TGA. ©2008 IEEE

The use of temperature and time dependent material parameters is state-of-the-art in mechanical engineering. An advanced measurement method for the determination of moisture dependent parameters for micro and nano scale samples was developed. In combination with FE-analysis, this tool (involving time, temperature, and humidity) ensures a sure deployability. The present paper deals with the influence of the moisture absorption oil the time and temperature dependent properties of epoxy systems. These thermosetting polymers have strong time and temperature dependent mechanical properties. It is ail excellent material for understanding moisture induced thermo mechanical behaviour. The influence of humidity on the materials behaviour shows that the humidity diffusion does not only effect a shift in the glass transition temperature and a reduction in the modulus, but also influences the visco elastic properties significantly. The moisture-dependent properties are analyzed by novel experimental procedures. It was found that for a lifetime model the relaxation behaviour as a function of temperature over time and moisture has a significant influence, which increases not only with temperature but also with moisture concentration. The cause of variant properties is the free volume and /or polarity of the structure. The combination of several Such factors of different materials parameters (moisture concentration hygroscopic swelling, and diffusion coefficient) and their interrelated influences makes ail important contribution to mechanical reliability analysis

The dependency of the failure mechanisms of PCB/BGA assemblies subjected to drop impact on board designs variations is investigated in this study. Two key parameters are considered: the copper pad size and the trace routing. It is shown that the assemblies can exhibit various failure modes such as copper trace crack, pad cratering on PCB or crack at interposer on package side by varying these board design parameters, due to stress/strain redistribution in assembly, as well as the location change of the weakest link. The tradeoff between these failure modes during the design change is also investigated. With the help of finite element simulations, reliable failure indicators for each possible failure mode can be defined. With all these indicators considered, it is therefore possible to establish rules for predicting the failure behavior and the lifetime of PCB/BGA assemblies subjected to drop impacts, depending on the board layout

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