Finite Element Evaluation of Thermal Stresses in a Composite Circuit Board Cooled by Mixed Convection

Present-day interest in the thermal analysis of electronic circuit boards arises mainly because of the failure of such components as a result of thermal fatigue. A thermal/structural ANSYS model was 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. The ANSYS model was required to incorporate the effects of mixed convection on surfaces, heat generation in the modules, and conduction inside the board. Appropriate convection heat transfer coefficients and boundary conditions resulted in a temperature distribution in the board and chips. Then structural analyses were performed on the same finite element mesh with structural elements capable of handling orthotropic material properties. The stress fields were obtained and compared for the two models possessing different fiber orientations.

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