Cu-Cu Bonding by Low-Temperature Sintering of Self-Healable Cu Nanoparticles

The Cu-Cu bonding temperature by using Cu nanoparticles is mainly influenced by the size and the purity of Cu nanoparticles. To remove the oxides of Cu, reducing atmosphere is always introduced into the sintering and bonding process. In this paper, a new Cu-Cu bonding method by sintering of self-healable Cu nanoparticles was proposed. With this method, the surface oxidation layer of Cu nanoparticle can be removed without reducing atmosphere at sintering and bonding process. In order to research the self-healing properties of the surface oxidized Cu nanoparticles, the sintering and bonding experiments were carried out under an Ar atmosphere. With self-healable Cu nanoparticles, the electrical resistivity of sintered Cu film can be reduced to lower than 5 µΩ·cm after sintering, and a high shear strength Cu-Cu joint over 25 MPa can be achieved after bonding at 250 °C. The oxygen content was also significantly reduced during the sintering and bonding process, which reflected the excellent self-healing property of Cu nanoparticle paste. The high Cu-Cu bonding strength and no requirement for reducing atmosphere indicate that the proposed self-healable Cu nanoparticle paste is promising to be wildly used in advanced electronics packaging.