Latest developments of compact thermal modeling of system-in-package devices by means of Genetic Algorithm

Nowadays, thermal designers have to deal with sophisticated 3D component packaging, enclosing several chips or conventional individually-packaged Integrated circuits with various power densities, embedded in small volumes that will drive up the complexity of their thermal management. Previous analyses were made on system-in-package (SIP) modules to better know the thermal behavior of its encapsulated chips as well as the ability to create a Compact Thermal Model with numerous power sources. These works demonstrated that the creation of thermal resistance networks with n sources, compliant with a large set of realistic boundary conditions, can be achieved with success using superposition principle and Genetic Algorithm (GA) fitting technique. To pursue the development of effective thermal models for DC-DC converter devices, a set of experiments was performed to assess the pertinence of numerical simulations. Thus the upper surface of the asymmetric side-by-sidechips package was subdivided to characterize a set of local maximal and average temperatures. The temperature predictions of the numerical models were compared with the experimental infrared results. The present work describes the process flow that has to be led to generate a detailed numerical model having a low divergence with experimental results. It also declines the creation of DELPHI style models of the discrete sensitive parts of the package, such as inductor device. Each deducted network predicts the monitored key temperatures of the detailed thermal model with a discrepancy lower than 10%. Further a reduction methodology which nests these SubCompact Thermal Models promotes an alternative solution to realize more quickly the generation of a multiple sources thermal resistance networks, according to the boundary condition independent concept [3]. Therefore, the paper summarizes the comparison of a "state-of-the-art" numerical detailed model and its deducted compact model with the help of infrared experi- ental results in order to establish a modeling guideline.