Abstract
AuCu phase had a significant effect on the bonding strength of Au80Sn20 alloy and Cu substrate. The formation of the AuCu(200)/Cu(200) interface significantly improves the shear strength of solder joints. Therefore, it is particularly important to analyze the strengthening mechanism of the AuCu phase in the Cu matrix. The atomic structure, interfacial stability, and interfacial bonding properties of the Cu(200)/AuCu(200) interface were investigated using first-principle calculation. The layer spacing convergence results show that seven layers of Cu(200) surface and seven layers of AuCu(200) surface are enough thick to be chosen for the interface model. The calculation shows that the surface energies are 1.463 J/m2 and 1.081 J/m2 for AuCu(200) surface and Cu(200) surface, respectively. Four interface combinations of Top sit, Long bridge, Short bridge, and Hollow were investigated by considering four stacking methods of AuCu(200). It is shown that the interfacial configuration of the Long bridge is the most stable and favorable structure, which has the largest adhesion work, the smallest interfacial energy, and the smallest interfacial spacing. The density of states and electron difference density were calculated for the four interfacial configurations, and the results showed that the main bonding mode of the Long bridge interface is composed of both Cu-Cu covalent bonds and Au-Cu covalent bonds.
Highlights
Au80Sn20 alloy is widely used in power electronic devices and optoelectronic packages because of its high thermal conductivity, good fluidity, excellent fatigue resistance, corrosion resistance, creep resistance, high yield strength, and no flux soldering [1,2,3,4,5]
The reliability of the solder joint depends on the nature of the solder itself but is closely related to the intermetallic compounds (IMCs) formed in the interfacial reaction [9]
It has been shown that the preferential orientation of these IMCs to the Cu substrate is important for the interface bonding of the solder joint [15]
Summary
Au80Sn20 alloy is widely used in power electronic devices and optoelectronic packages because of its high thermal conductivity, good fluidity, excellent fatigue resistance, corrosion resistance, creep resistance, high yield strength, and no flux soldering [1,2,3,4,5]. The experimental results demonstrate that IMCs are mainly composed of AuCu and (Au,Cu)5Sn on the Au80Sn20/Cu interface [10,11,12,13,14,15]. These types of IMCs greatly affect the long-term reliability of the solder joints attributed to their intrinsic brittleness. The strong AuCu layers were partially destroyed, forming small cleavage surfaces This indicates that the stability of the solder joint is obviously improved when the AuCu/Cu interface is formed. The Cu(200)/AuCu(200) interface is studied, and subsequently, the binding energy, interfacial energy, electronic structure, and bonding properties of the Cu(200)/AuCu(200) interface are calculated using a first-principle approach
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
