Thermal interaction of semiconductor devices on copper clad ceramic substrates

The temperature rise due to the spacing between two heat dissipating devices mounted on metallized or copper-clad ceramic substrates is presented. The thickness of the copper layer, the thermal conductivity of the substrate material, and the thermal resistance of the heat sink system are considered. Results for parameters typically found in power hybrid applications are presented in nondimensional form. The results indicate that increasing the thickness of the copper metallization requires that the devices be placed farther apart to prevent thermal interaction. An increase in the copper layer thickness can significantly decrease the device temperatures on alumina, but may increase temperatures on high thermal conductivity ceramic substrates such as beryllia (BeO). The results also demonstrate that the external heat sink thermal resistance can cause significant heat flow spreading and increased temperatures in the substrate. As the external resistance increases, the spacing required to prevent thermal interaction also increases