In this paper, self-assembled monolayer of 1-hexanethiol was formed on Cu thin layer to protect its surface against excessive oxidation during storage in the atmosphere. Then the self-assembled monolayer layer is dissolved using ethyl alcohol to expose the clean surface of Cu before bonding. The contact angles of the samples are measured so as to evaluate the passivation effect. The results indicate that after dealing with 1-hexanethiol, large contact angles of the samples can be acquired and remain stable in the air for a long time. Using this method, high-quality Cu-Cu thermo-compression bonding samples are obtained.