Challenge
Moisture absorption is a potential problem for any non-hermetic (unsealed) package. Any moisture absorbed by the permeable plastics during package manufacture, handling, shipping, storage, etc is driven out of the package during the assembly process fitting the package onto the circuit board; this rapid moisture desorption can cause damage/delamination of the package.
Solution
The Mutiphysics solution from SIMULIA allows electronic package manufacturers to analyze the rapid moisture desorption process, taking into account the coupling between thermal and moisture fields and then to extract the resulting stresses from the process. State-of-the-art fracture, failure and delamination capabilities are available to capture the progressive failure of a package.
Benefit
Accurate simulation taking into account coupled-thermal, moisture, and mechanical fields is key to electronic component and package design. Virtual package design and qualification for moisture sensitivity offers significant time savings over physical testing.
A simplified 2D representation of an electronic package for demonstration purposes. The same model techniques are equally applicable to full 3D simulation models.
The following plots show the residual Mises stress in the electronic package following a 178 hour moisture absorption conditioning and then desorption during the reflow process. The moisture field is driven by both the thermal and the mechanical fields. These results are used to calculate the hygrostresses, which when combined with the thermal stresses provide the total stress in the package.
Reference:
Coupled Thermal-Moisture-Stress Analysis for Electronic Packages, Cadge, Wang, Bie, Sun, Gong - EMAP2006
