A study on intermetallic compound formation in Ag–Al system and evaluation of its mechanical properties by micro-indentation

Abstract

In electronic packaging in recent years, silver (Ag) alloy wires have been widely adopted in wire-bond processes. The bond pads on the device chips are mostly aluminum (Al). Thus, the bonding interface is mainly Ag-Al. In recent Ag alloy wirebond publications, it is unclear what intermetallic phases form at the interface. In this research, experiments were designed to understand the Ag-Al intermetallic compound (IMC) formation in the Ag-Al system and evaluate its mechanical properties. First, the Ag-Al alloys with compositions from 19 to 43 at.% Al were evaluated to identify the phase equilibrium and crystal structure of the Ag-Al intermetallic phases. Microstructures and phase compositions of the designed Ag-Al alloys are presented. To further study the intermetallic compound formation at the Ag/Al interface, the interfacial reaction of the Ag/Al joints at 200 °C was investigated. The µ-Ag 3 Al and δ-Ag 2 Al IMC were identified to form at the Ag/Al interface and stabilize after long-time annealing at 200 °C. At last, deformation and fracture behaviors of the bulk µ-Ag 3 Al and δ-Ag 2 Al were analyzed by the micro-indentation. The measured results reveal that µ-Ag 3 Al exhibits significantly higher hardness and lower fracture toughness as compared to δ-Ag 2 Al. Indentation crack propagation in µ-Ag 3 Al demonstrates the fracture characteristics of brittle materials. In the case of δ-Ag 2 Al, the presence of slip bands exhibits the ductility of δ-Ag 2 Al to endure plastic deformation prior to fracture. The effect of the mechanical properties of the µ-Ag 3 Al and δ-Ag 2 Al IMC on the Ag-Al joint reliability is discussed. New information obtained in this research is important for future study of the joint reliability and failure mechanism of Ag-Al wire bonds.

The Role of Interlayer Chemistry in Li‐Metal Growth through a Garnet‐Type Solid Electrolyte

“…[42] Metals with high solubilities in the matrix possibly exhibit lower interfacial energies between the precipitate and matrix material by creating a chemically compatible interface as the precipitates nucleate. [57][58][59] According to phase diagrams, [48] lithium does not exhibit appreciable silicon solubility, whereas the β-Li phase has a high silver solubility limit. [49] Moreover, intermetallic Li-Si compounds do not show noticeable lithium solubilities in any phase; on the other hand, Li-Ag alloys allow a wide range of composition variations.…”

“…In a previous report, Yan et al studied the behavior of lithium‐metal nucleation on a variety of metal substrates with different alloying properties and suggested that the solubility of a metal in the lithium alters the magnitude of the electrochemical overpotential to eventually facilitate nucleation behavior 42. Metals with high solubilities in the matrix possibly exhibit lower interfacial energies between the precipitate and matrix material by creating a chemically compatible interface as the precipitates nucleate 57–59. According to phase diagrams,48 lithium does not exhibit appreciable silicon solubility, whereas the β‐Li phase has a high silver solubility limit 49.…”

Silver Foams with Hierarchical Porous Structures: From Manufacturing to Antibacterial Activity

“…Overall, these XRD patterns are consistent with the previously published literature on Al–Ag alloys with similar Ag contents treated with HCl and NaOH. 23 , 25 , 26 Analysis of the XRD pattern for the Ag–HCl sample shows not only that the α-Al(Ag) phase was completely dissolved but also that the Al contained in the intermetallic β-Ag 2 Al was dissolved concurrently. It was shown that dissolution of the primary α-Al(Ag) crystals in HCl acid creates penetration pathways that exhibit a catalytic effect for the dissolution of β-Ag 2 Al in biphasic Al–Ag alloys.…”

Влияние структурных свойств на электросопротивление тонких пленок Al/Ag в процессе твердофазной реакции

“…Соединения с алюминием представляют огромный интерес для микроэлектронной промышленности. Они используются в качестве электрических соединений, диффузионных барьеров, материалов для увеличения сопротивления к электромиграции [1][2][3][4][5]. Интерметаллические соединения Al-Ag имеют потенциальное практическое применение в микроэлектронных устройствах [6], конструкциях светоизлучающих диодов [7][8][9][10].…”

“…Фаза µ-Ag 3 Al представляет больший интерес, т. к. по сравнению с фазой γ-Ag 2 Al она обладает большим коэффициентом отражения, а также значительно большей твердостью и более низкой вязкостью разрушения [2].…”