Heat-cycle endurance and in-plane thermal expansion of Al₂O₃/Al substrates formed by aerosol deposition method

Abstract

A new heat radiation substrate for high power modules has been proposed by utilizing Al₂O₃ thick films formed by the aerosol deposition method (ADM) on Al substrates. Dense Al₂O₃ thick films (AD-Al₂O₃) could be obtained by the ADM at room temperature. A heat-cycle endurance test between -80°C and 180°C revealed that the AD-Al₂O₃/Al substrates were superior to the conventional direct brazed aluminum (DBA) substrates using AlN ceramics bounded to Al substrates. No lamination was observed between the AD-Al₂O₃ films and Al substrates after heat-cycle test in spite of the difference of thermal expansion coefficient between Al₂O₃ and Al. The in-plane thermal expansion coefficient of AD-Al₂O₃ films was almost the same as that of Al substrates, indicating that plastic deformation was induced in the AD-Al₂O₃ films consisting of nano-sized grains to relax the stress caused by the difference of thermal expansion coefficient.