Thermal reliability design and optimization for multilayer composite electronic boards

Boards made of composites are susceptible of structural failure or irreversible damage under thermally raised stresses. A thermal/structural finite element model is 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 is modeled as a thin plate containing four heated flush rectangular areas that represent the electronic modules. The finite element model should be to able to accept the convection heat transfer on the board surface, heat generation in the modules, and directional conduction inside the board. A detailed 3-D CFD model is incorporated to predict the conjugate heat transfer coefficients that strongly affect the temperature distribution in the board and modules. Structural analyses are performed by a FE model that uses the heat transfer coefficients mentioned above, and structural elements capable of handling orthotropic material properties. The stress fields are obtained and studied for the models possessing two and there laminates with different fiber orientations, and inter-fiber angles. Appreciable differences in values of max stress intensity were observed as the fiber orientation and inter-fiber angle changed. The angular parameters in this study were guided by experimental design (DOE) concepts leading to a metainodel of the stress intensity in the board. The optimum design variables found by the equations of the metamodel.