Effects of alloying elements in high reliability copper wire bond material for high temperature applications
Recently, a shift from Au bonding wire to Cu bonding wire is expected for automotive application. Palladium coated copper (PCC) wire is strong candidate since it is widely used in LSI packages owing to its high performance and low cost. In order to apply PCC wire to automotive devices, long-term reliability specific to automobiles including stable operation under harsh environment with high temperature and humidity is required. However, pitting corrosion at the wedge bond portion was reported with PCC wire under high temperature storage life (HTSL) test. Depending on the surrounding environment such as mold compound, it is difficult for conventional PCC wire to achieve the target of automotive application. A newly developed PCC wire (EX1R) has thus developed. By using additive element in Cu core, halide induced interface corrosion and also pitting corrosion can be prevented successfully. In this paper, effect of additive element on the corrosion resistance will be discussed. The result shows that additive element forms protective passivation layer on the intermetallic compound (IMC) and Cu surface. Thereby, EX1R improves bond reliability even under severe reliability test condition.