Evaluation of the corrosion performance of Cu–Al intermetallic compounds and the effect of Pd addition. (January 2016)

• Record Type: Journal Article
• Authors: Lim, Adeline B.Y.; Neo, Wei Jian; Yauw, Oranna; Chylak, Bob; Gan, Chee Lip; Chen, Zhong
• Is Part Of: Microelectronics and reliability. Volume 56(2016)
• Page Start: 155
• Page End: 161
• Publication Date: 2016-01
• Subjects: Palladium -- Cu–Al intermetallic compounds -- Copper wire bonding -- EIS -- Tafel; Electronic apparatus and appliances -- Reliability -- Periodicals; Miniature electronic equipment -- Periodicals; Appareils électroniques -- Fiabilité -- Périodiques; Équipement électronique miniaturisé -- Périodiques; Electronic apparatus and appliances -- Reliability; Miniature electronic equipment; Periodicals; 621.3815
• DOI: 10.1016/j.microrel.2015.10.012
• Languages: English
• ISSNs: 0026-2714

Abstract

Abstract: Copper wire has become a mainstream bonding material in fine-pitch applications due to the rising cost of gold wire. In recent years, palladium-coated copper (Pd–Cu) wire is being increasingly used to overcome some constraints posed by pure Cu wire. During wire bonding with aluminum bond pads, different intermetallic compound (IMC) phases that have been identified at the bond interface are typically CuAl2, CuAl and Cu9 Al4 . However, the corrosion susceptibility of these IMCs has not been investigated. This paper compares the electrical impedance and corrosion performance of the three types of Cu–Al IMCs in an acidic chloride medium by employing electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The analysis of the potentiodynamic polarization results was performed using Tafel extrapolation. A comparison was made with pure Cu and Al. The effect of Pd alloy on the IMC corrosion performance has also been studied. Among the three Cu–Al IMCs, Cu9 Al4 was observed to have the largest corrosion rate followed by CuAl2 and CuAl. For the metals, Cu was observed to have the lowest corrosion rate and Al is the most easily corroded. The addition of Pd of up to 10 wt.% replacement of the Cu in the alloys slightly improves the corrosion resistance of the metals and IMCs. Highlights: Corrosion performance of Cu, Al and Cu–Al IMCs in a chloride medium was studied. Effect of palladium addition on these corrosion properties was also investigated. Corrosion resistance of the metals and IMCs improved slightly with Pd addition. Cu9 Al4 has the highest corrosion rate among the IMCs.