Interfacial reaction and mechanical properties for Cu/Sn/Ag system low temperature transient liquid phase bonding

Abstract

Low temperature transient liquid phase (LTTLP) bonding is a promising technology to enable in high temperature electronic packaging. In this study, interfacial reaction and mechanical characterizations for Cu/Sn/ Ag system LTTLP bonding at temperatures ranging from 260 to 340°C for various time were investigated. Experimental results showed that Cu and Ag substrate independently reacted with molten Sn, and the growth of IMCs on one side was hindered by the opposite IMCs layer after scalloped Cu 6 Sn 5 contacted with the Ag 3 Sn, and there was no ternary alloy phase formed all the time. Pores were found and distributed at the Cu 6 Sn 5 /Ag 3 Sn interface or between grain boundaries after the residual Sn was fully consumed, however, they gradually disappeared with continuing reaction of that Cu 6 Sn 5 phase converted into Cu 3 Sn phase. Shear strength of the LTTLP joints increased with increasing bonding time, and the adhesive strength of Cu 6 Sn 5 /Ag 3 Sn interface was weaker than that of the Cu 3 Sn/Ag 3 Sn interface. The rupture behaviors were also discussed with a fracture model. As follow, cracks initiated in the pore and mainly propagated along the Cu

Morphology transformation on Cu3Sn grains during the formation of full Cu3Sn solder joints in electronic packaging

“…Comparatively, under the interconnected height less than dozens of micrometers, the IMCs account for a larger proportion in the interfacial region after soldering. Even, when the soldering time is extended, the solder can be consumed completely to form IMCs, leading to the formation of full IMCs joints (Chiu et al, 2014;Flötgen et al, 2014;Kato et al, 1999;Li and Chan, 2017;Li and Agyakwa, 2010;Li et al, 2011;Luu et al, 2013;Mo et al, 2015;Shao et al, 2016Shao et al, , 2017aShao et al, , 2017bTian et al, 2014a;Yao et al, 2017aYao et al, , 2017b. In other words, when the interconnected height is less than dozens of micrometers, the interfacial structure of joints can be transformed from substrates/IMCs/solder/IMCs/substrates to substrates/IMCs/substrates with the increase of soldering time.…”

“…Undoubtedly, it is very essential to conduct studies regarding the formation of full IMCs solder joints. Currently, relevant studies mainly focus on growth kinetics of IMCs layers during the formation of full IMCs joints (Li and Chan, 2017;Li and Agyakwa, 2010;Mo et al, 2015), soldering process and interfacial phase evolution for the formation of full IMCs joints (Chiu et al, 2014;Flötgen et al, 2014;Kato et al, 1999;Li et al, 2011;Luu et al, 2013;Shao et al, 2016;Yao et al, 2017aYao et al, , 2017b and reliabilities of full IMCs joints Shao et al, 2017aShao et al, , 2017bTian et al, 2014a). For the studies regarding interfacial phase evolution, these can be divided into two parts.…”

“…For the studies regarding interfacial phase evolution, these can be divided into two parts. The two parts includes the studies regarding interfacial phase transition (Kato et al, 1999;Li et al, 2011;Shao et al, 2016;Yao et al, 2017a) and the studies regarding the morphology transformation of interfacial phases (Yao et al, 2017b). The interfacial phase transition was usually concerned through observing cross-sectional micrographs of joints with different soldering time (Kato et al, 1999;Li et al, 2011;Shao et al, 2016;Yao et al, 2017a).…”

Study on Microstructure and Shear Property of Cu/In-xCu/Cu Transient Liquid Phase Bonding Joints

“…15 Cu-Sn solder has been widely used in the semiconductor industry due to the low cost, high electronic conductivity and low melting temperature. [16][17][18] However, some reliability problems of the Cu-Sn bonding system exist on account of the formation of brittle Cu-Sn IMCs and Kirkendall voids. [19][20][21] Moreover, the melting point of Sn (231°C) is higher than that of In (156°C), and the bonding temperature is relatively high, so it is difficult to use in chip bonding which needs a lowtemperature process.…”

Rapid Ag/Sn/Ag transient liquid phase bonding for high-temperature power devices packaging by the assistance of ultrasound

“…The TLP-bonded joints have much higher thermal reliabilities than the traditional soldered joints with Sn-based solders. However, the bonding process to obtain full IMCs is highly time-consuming (>60 min) due to its diffusion controlled reaction, which would lead to extra thermal stress and then decline the reliability [5][6][7]. Therefore, the development of a TLP process needing short time period is necessary, for not only the reliability of electronic devices but also the economically viable for mass production.…”