Brittle-to-ductile transition of Au2Al and AuAl2 intermetallic compounds in wire bonding

Yang, Hengfu; Cao, Ke; Zhao, Xiangyong; Liu, Wei; Lü, Jian; Lü, Yang

doi:10.1007/s10854-018-0357-6

Cited by 9 publications

(7 citation statements)

References 19 publications

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“…When the Ag content (x) was greater than 50 wt.%, no Au 2 Al phase was formed at the interface, as shown in Figures 8 and 11. Based on the research reported by Yang et al [20], we found the following results after comparing the mechanical properties between the AuAl 2 and Au 2 Al phases. The Au-rich Au-Al IMC was softer and more ductile than the Al-rich Au-Al IMC to resist the propagation of cracks.…”

Section: Ag Content Effect and Reaction Kinetics In The Au-xag/al Rea...mentioning

confidence: 60%

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Phase Equilibria of the Ag-Al-Au Ternary System and Interfacial Reactions in the Au-xAg/Al Couples at 450 °C

Ramadhani,

Laksono,

Liang

et al. 2023

Materials

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The phase equilibria of the Ag-Al-Au ternary system and the solid-state reaction couple for the Au-xAg/Al system were investigated isothermally at 450 °C. By investigating the Ag-Al-Au ternary system and its isothermal section, this study aims to provide a clearer understanding of the phase stability and interfacial reactions between different phases. This information is crucial for designing materials and processes in electronic packaging, with the potential to reduce costs and improve reliability. There were seven single-phase regions, thirteen two-phase regions, and six three-phase regions, with no ternary intermetallic compound (IMC) formed in the isothermal section of the Ag-Al-Au ternary system. When the Au-25 wt.% Ag/Al couple was aged at 450 °C for 240–1500 h, the AuAl2, Au2Al, and Au4Al phases formed at the interface. When the Ag contents increased to 50 and 75 wt.%, the Ag2Al, AuAl2, and Au4Al phases formed at the interface. When the aging time increased from 240 h to 1500 h, the total IMC thickness in all Au-xAg/Al couples became thicker, but the types of IMCs formed at the interface did not change. The total IMC thickness also increased with the increase in the Ag content. When the Ag content was greater than 25 wt.%, the Au2Al phase was converted into the Ag2Al phase. The IMC growth mechanism in all of the couples followed a reaction-controlled process.

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Section: Ag Content Effect and Reaction Kinetics In The Au-xag/al Rea...mentioning

confidence: 60%

Section: Ag Content Effect and Reaction Kinetics In The Au-xag/al Rea...mentioning

confidence: 62%

Phase Equilibria of the Ag-Al-Au Ternary System and Interfacial Reactions in the Au-xAg/Al Couples at 450 °C

Ramadhani,

Laksono,

Liang

et al. 2023

Materials

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“…13), indicating the presence of Au 4 Al or Au 8 Al 3 rather than brittle 'purple plague' AuAl 2 . These two types of Au-rich IMCs are considered to be ductile [50], [51], and thus potentially beneficial for the reliability of the bond.…”

Section: B Inspection Of Bond Interfacesmentioning

confidence: 99%

Wafer-Level Vacuum Sealing by Transfer Bonding of Silicon Caps for Small Footprint and Ultra-Thin MEMS Packages

Wang

Bleiker

Edinger

et al. 2019

J. Microelectromech. Syst.

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Vacuum and hermetic packaging is a critical requirement for optimal performance of many micro-electromechanical systems (MEMS), vacuum electronics, and quantum devices. However, existing packaging solutions are either elaborate to implement or rely on bulky caps and footprint-consuming seals. Here, we address this problem by demonstrating a waferlevel vacuum packaging method featuring transfer bonding of 25-µm-thin silicon (Si) caps that are transferred from a 100-mm-diameter silicon-on-insulator (SOI) wafer to a cavity wafer to seal the cavities by gold-aluminum (Au-Al) thermocompression bonding at a low temperature of 250 • C. The resulting wafer-scale sealing yields after wafer dicing are 98% and 100% with sealing rings as narrow as 6 and 9 µm, respectively. Despite the small sealing footprint, the Si caps with 9-µm-wide sealing rings demonstrate a high mean shear strength of 127 MPa. The vacuum levels in the getter-free sealed cavities are measured by residual gas analysis to be as low as 1.3 mbar, based on which a leak rate smaller than 2.8 × 10 −14 mbarL/s is derived. We also show that the thickness of the Si caps can be reduced to 6 µm by post-transfer etching while still maintaining excellent hermeticity. The demonstrated ultra-thin packages can potentially be placed in between the solder bumps in flip-chip interfaces, thereby avoiding the need of through-capvias in conventional MEMS packages. [2018-0257] Index Terms-Vacuum, hermetic, packaging, sealing, MEMS, ultra-thin package, small footprint, transfer bonding, 3D integration, flip chip, aluminum, gold, thermo-compression bonding. I. INTRODUCTION V ACUUM packaging is a process for encapsulating a device (e.g. a MEMS or nano-electro-mechanical system (NEMS) device) in a vacuum environment and maintaining the internal vacuum level using hermetic seals. It enables functionality and long-term reliability of various MEMS devices, such as inertial sensors, pressure sensors and infrared detectors, but typically also constitutes a significant part of their cost in high-volume production [1], [2]. As a general trend,

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“…The interface properties between the Au stud and Al pad have been studied in the wire bonding structures of the traditional electronic packaging (Zhang and Tee, 2006;Yang et al, 2019). It is found the Au and Al atoms are quite active and the IMC such as Au 4 Al, Au 5 Al 2 , Au 2 Al, AuAl and AuAl 2 will be formed (Kim et al, 2004a(Kim et al, , 2004bLee et al, 2008;Ha and Jung, 2013;Lim et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

“…Zhang and Tee (2006) show that the growth rate of IMC between the Au stud and the Al pad is much related to the temperature and obeys the Arrhenius equation, because the IMC formulation is controlled by the atoms diffusion process, and the temperature is one of the most important factors to affect the diffusion velocity. At the same time, Yang et al (2019) showed that the growth of the IMC layer will decrease the shear strength and the fatigue life of the wire boding structure which is the key factor to affect the long-term reliability. When it comes to the Au stud bonding structure, the failure mechanism will be different because of the difference in the structure.…”

Section: Introductionmentioning

confidence: 99%

Experimental study on the fracture behavior variation of the Au stud bump bonding with different high temperature storage times

Zhang

Wang

Sun

et al. 2023

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Purpose Au stud bump bonding technology is an effective means to realize heterogeneous integration of commercial chips in the 2.5D electronic packaging. The purpose of this paper is to study the long-term reliability of the Au stud bump treated by four different high temperature storage times (200°C for 0, 100, 200 and 300 h). Design/methodology/approach The bonding strength and the fracture behavior are investigated by chip shear test. The experiment is further studied by microstructural characterization approaches such as scanning electron microscope, energy dispersive spectrometer and so on. Findings It is recognized that there were mainly three typical fracture models during the chip shear test among all the Au stud bump samples treated by high temperature storage. For solder bump before aging, the fracture occurred at the interface between the Cu pad and the Au stud bump. As the aging time increased, the fracture mainly occurred inside the Au stud bump at 200°C for 100 and 200 h. When aging time increased to 300 h, it is found that the fracture transferred to the interface between the Au stud bump and the Al Pad. Originality/value In addition, the bonding strength also changed with the high temperature storage time increasing. The bonding strength does not change linearly with the high temperature storage time increasing but decreases first and then increases. The investigation shows that the formation of the intermetallic compounds because of the reaction between the Au and Al atoms plays a key role on the bonding strength and fracture behavior variation.

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Brittle-to-ductile transition of Au2Al and AuAl2 intermetallic compounds in wire bonding

Cited by 9 publications

References 19 publications

Phase Equilibria of the Ag-Al-Au Ternary System and Interfacial Reactions in the Au-xAg/Al Couples at 450 °C

Phase Equilibria of the Ag-Al-Au Ternary System and Interfacial Reactions in the Au-xAg/Al Couples at 450 °C

Wafer-Level Vacuum Sealing by Transfer Bonding of Silicon Caps for Small Footprint and Ultra-Thin MEMS Packages

Experimental study on the fracture behavior variation of the Au stud bump bonding with different high temperature storage times

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