The thermal comportment of a microchip with four heat sources made in a highly nonlinear material is considered, for various boundary conditions and thermal loads. To save computation time, a Reduced Order Model (ROM) is proposed to replace the original and high-order model. Among the different reduction methods, a modal method is chosen. The non-linearity is taken into account via a simplified quadratic law. This leads to a simple formulation and a prompt numerical implementation. The ROM is highly reliable whatever the environment conditions and the activated source, while the computation time is reduced by a factor 300.