Comparison of various substrate technologies under steady state and transient conditions

Several substrate technologies for use in automotive electronics applications have been studied for their relative thermal performance. These technologies include aluminum oxide (A1₂O₃) insulated metal substrate (collectively known as AIMS); aluminum nitride (AlN) direct-bond copper (DBCu); aluminum oxide direct-bond copper; insulated metal substrate; FR4 substrate; field effect transistor (FET) on copper spreader on FR4. All substrate configurations were attached to die-cast aluminum (Al) rigidizers. Only the AIMS substrate was studied as a system utilizing both die-cast and stamped aluminum rigidizers. The FR4 substrates included thermal vias. The technologies were compared under both steady state and transient power conditions. Additionally, conduction-only (localized) and conduction/convection (system-level) models were studied. Localized results indicate all substrate configurations perform better than FR4, provided the in-plane dimensions of the substrate under study remain the same. System-level results indicate all substrate configurations perform better than FR4, provided the FET spacing is maintained approximately the same. The slight influence of thermal property variation is demonstrated. Performance vs. normalized cost is also presented.