ESTIMA:: A thermal simulation software for the optimal design of printed circuit board in the automotive industry

The optimisation of the design of printed circuits boards (PCB) for automotive junction boxes is leading the industry towards the inclusion of the numerical prediction of local temperatures at the board and the electrical/electronic components in the initial stages of the design process. The paper shows the modelling and numerical characteristics of ESTIMA, an integrated software specifically developed for the numerical prediction of the coupled electrical and thermal fields in a PCB with active electrical or electronic components. The software includes the modelling of the conduction heat transfer through an heterogeneous solid (board and tracks) with temperature dependent physical properties, the modelling of the electrical field, submitted to local differences in resistivities and also to heterogeneities (tracks, solders and jumpers), and the thermal modelling of electrical (fuses, relays,) and electronic (solid state relays) components. The program is based on a second order accurate finite volume formulation. The thermal field is computed in a regular 3D grid, fine enough to resolve the track shape, while the electrical field is computed in a finer 2D mesh that solves the details of the electrical intensity field within every active track. Components are modelled as a finite set of nodes, taking into account their intrinsic power dissipation, their connection to different points of the board and their relation to the ambient both through convection and though radiation processes. Extensive comparison with experiments has allowed Lear Co. to use this software as a standard tool in the design process of PCB's.