Finite Element Stress Evaluation of a Composite Board Using 2-D and 3-D Convection Models

Thermal fatigue and high levels of thermal stresses in electronic circuit boards have been of great concerns to designers in a wide range of applications such as avionics and computers. Fluid/thermal/structural models were integrated in this study to enable the predictions of the temperature and stress distribution of vertically clamped parallel circuit boards that include series of symmetrically mounted heated electronic modules (chips). The board was modeled as a thin plate containing heated flush rectangular areas representing the heat generating modules. Initially two convection models, a 2-D and a 3-D model were incorporated to predict the heat transfer coefficients that strongly affect the temperature distribution in the board and chips. Then ANSYS models were used to incorporate the effects of mixed convection on surfaces, heat generation in the modules, and conduction inside the board. Then analyses were performed by ANSYS using structural elements capable of handling orthotropic material properties. The stress fields were obtained and compared for the two models possessing different convection models.

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