Effects of different inhibitor on antioxidation of copper bonding wire at room temperature

With the rapid development of the electronic packaging industry, traditional gold bonding wires are tended to be replaced gradually and partially by copper bonding wires with low cost and better potential performance. However, it is difficult to control and prevent the oxidation of copper bonding wire even in the case of palladium plating. Therefore, it is necessary to explore a method to inhibit the oxidation of copper wire before plating at room temperature. In this paper, different inhibitors, including organic benzotriazole and carboxymethylcellulose sodium (BTA, CMC), inorganic (Ce(NO 3 ) 3 ·6H 2 O) and compound (CMC + Ce(NO 3 ) 3 ·6H 2 O), are selected to form a thin film on the surface of copper bonding wires with different diameters, respectively, and the effects on the antioxidation of copper wire at room temperature are discussed by means of electrochemical polarization and impedance measurement combined with SEM observation, EDS and XPS analysis. The kinetic results demonstrate the antioxidation properties of the copper bonding wires have been improved to a certain extent after an inhibitor film forms on the surface of copper wire. In particular, BTA and compound (CMC + Ce(NO 3 ) 3 ·6H 2 O) play a better role, attributed to the fact that BTA and compound (CMC + Ce(NO 3 ) 3 ·6H 2 O) are more beneficial to form a dense and evenly distributed smooth surface with higher electrochemical stability and impedance. For the CMC + Ce(NO 3 ) 3 ·6H 2 O system, the hydroxides or hydrated oxide particles of Ce 3+ would form on the surface of copper wire after immersion in the Ce(NO 3 ) 3 ·6H 2 O solution for the first 12 h. Subsequently, Ce 3+ would replace Na + to form a more compact and continuous complex film after immersed in CMC solution for another 12 h, as a result, the antioxidation property is enhanced under the synthetic effects.