Thermal RC-network approach to analyze multichip power packages

Semiconductor packaging and interconnect technologies today focus more and more on system solutions with increased modularity and functionality. As an example, mechanical relay replacement by semiconductor solutions rely on the additional control, diagnostic and communication functions that cannot be provided by power devices alone. For cost, thermal performance and mechanical reliability reasons multi chip solutions with separate control and power functions are required. Associated high integration packaging with a high power density can yield critical temperature states in the sensitive semiconductor devices. Enhanced thermal concepts are needed in order to avoid overheating and provide the necessary package performance. The definition of certain junction to case or junction to ambient thermal resistance values alone does not satisfy these needs. Profound understanding of the heat transfer mechanisms at any steady or transient loading is essential for the development of new assemblies. The temperature rises in all dice have to be known at any combination of electrical loading functions. It is practically impossible to replicate all possible field conditions in a laboratory environment. Thermal RC-networks, representing the heat transfer behavior of a multi chip package, help to overcome that issue. Arbitrary stimulus functions can be applied in order to simulate the time dependent temperature responses. The required network parameters can be identified with transient temperature measurements or even finite element simulations.