The temperature of electronic systems plays a significant role in their lifespan. Therefore, it is crucial to regulate their temperature. In several applications, such as those involving commercial-off-the-shelf (COTS) components, the positioning of components and the structure of the board are not known to the manufacturer. The dimensions and configuration of electronic components, in addition to their spatial distribution on the circuit board, can vary significantly. This variation has a direct impact on the thermal conditions that prevail within the system. It is therefore important to be aware of these geometric factors and the power-up scenarios for each chip. This study investigates the challenge of identifying multiple internal sources inside an electronic board through surface temperature measurements. For this aim, a system-representative numerical model is established and employed in the ensuing inverse source identification process. The study presented in this article demonstrates that the identification of multiple volume sources with realistic ignition scenarios and different shape and size in an electronic board is possible.