Direct bonded aluminum on aluminum nitride substrates via a transient liquid phase and its application

A new bonding process has been developed for producing direct bonded aluminum (DBA) substrates using aluminum nitride (AlN). A transient eutectic liquid phase forms in aluminum-X (X = silicon, germanium, silver, or copper) systems at the interface between the aluminum foil and the AlN substrate. The aluminum-X liquid phase transiently contacts the AlN substrate prior to isothermal solidification by diffusion of the element X into the aluminum foil. We prepared DBA substrates using this process and demonstrated that they are highly stable after thermal cycling testing. Furthermore, we used this method to simultaneously bond and fabricate DBA substrates with an aluminum-alloy base plate. We confirmed that this new process for fabricating DBA substrates with an aluminum-alloy base plate has the potential to be cost-effective and to be applied to produce high-reliability, high-power modules used under conditions of severe thermal stress.