抄録
A material mixing method to obtain an optimal topology for a structure made of several materials in static problems has been developed based on Evolutionary Structural Optimization (ESO). We extended the material mixing method to a structure with the multiple thermal criteria of thermal flux and thermal stress. To examine the validity of the method, it was applied to a printed circuit board (PCB) substrate. The overall efficiency of material usage in PCB substrate was measured in terms of the combination of thermal stress levels and heat flux densities by using a combination strategy with weighting factors. Pareto optimal topology solution having multiple thermal criteria was obtained. The effects of weighting factors for thermal stress and heat flux criteria as well as mechanical boundary conditions on optimal topologies were investigated. It is found that as the weighting factor for heat flux density is getting larger, the size of holes at the center portion become larger in proportion to the weighting factor in order to dissipate thermal energy much efficiently. The thermal stress on the clamped four sides is larger than that on the two sides clamped. It was verified that the suggested material mixing method works very well for topology optimization of a PCB substrate for various mechanical boundary conditions with multiple thermal criteria.
