Influence of ultrasounds on interfacial microstructures of Cu-Sn solder joints

Abstract

Purpose This study aims to investigate the interfacial microstructures of ultrasonic-assisted solder joints at different soldering times. Design/methodology/approach Solder joints with different microstructures are obtained by ultrasonic-assisted soldering. To analyze the effect of ultrasounds on Cu6Sn5 growth during the solid–liquid reaction stage, the interconnection heights of solder joints are increased from 30 to 50 μm. Findings Scallop-like Cu6Sn5 nucleate and grow along the Cu6Sn5/Cu3Sn interface under the traditional soldering process. By comparison, some Cu6Sn5 are formed at Cu6Sn5/Cu3Sn interface and some Cu6Sn5 are randomly distributed in Sn when ultrasonic-assisted soldering process is used. The reason for the formation of non-interfacial Cu6Sn5 has to do with the shock waves and micro-jets produced by ultrasonic treatment, which leads to separation of some Cu6Sn5 from the interfacial Cu6Sn5 to form non-interfacial Cu6Sn5. The local high pressure generated by the ultrasounds promotes the heterogeneous nucleation and growth of Cu6Sn5. Also, some branch-like Cu3Sn formed at Cu6Sn5/Cu3Sn interface render the interfacial Cu3Sn in ultrasonic-assisted solder joints present a different morphology from the wave-like or planar-like Cu3Sn in conventional soldering joints. Meanwhile, some non-interfacial Cu3Sn are present in non-interfacial Cu6Sn5 due to reaction of Cu atoms in liquid Sn with non-interfacial Cu6Sn5 to form non-interfacial Cu3Sn. Overall, full Cu3Sn solder joints are obtained at ultrasonic times of 60 s. Originality/value The obtained microstructure evolutions of ultrasonic-assisted solder joints in this paper are different from those reported in previous studies. Based on these differences, the effects of ultrasounds on the formation of non-interfacial IMCs and growth of interfacial IMCs are systematically analyzed by comparing with the traditional soldering process.

Microstructures evolution and growth kinetics of intermetallic compounds in Cu/Sn/Cu system during ultrasonic soldering process

“…This resulted in the decrease in the thickness of the liquid Sn layer, which weakened the ultrasonic effects. Han et al (Han et al, 2021) found that the non-interfacial Cu 6 Sn 5 grains in ultrasonic solder joints with thick liquid Sn layer were more than those in the solder joints with thin liquid Sn. With the extension in the ultrasonic time to 50 s, the interfacial Cu 6 Sn 5 at some positions grew toward the center of the interfacial region and subsequently merged with interfacial Cu 6 Sn 5 at the opposite side, as shown in Figure 3(h).…”

Microstructural and Mechanical Characterization of Cu/Sn Slid Bonding Utilizing Co as Contact Metallization Layer

“…Nevertheless, the processing time to achieve the Cu/Cu 3 Sn/Cu bond structure is much longer than Cu/Cu 3 Sn/Cu 6 Sn 5 /Cu 3 Sn/Cu, which can cause extra thermal stress and subsequently deteriorate the reliability of the packaging system. However, the development of effective approaches to shorten the bonding time has been explored in the literature [37,38]. For instance, it has been shown that obtaining a Cu/ Cu 3 Sn/Cu joint requires a short bonding time by employing a pulsed High Frequency Electromagnetic Field (HFEF) [37].…”

Effect of external static magnetic field on the particle distribution, the metallurgical process and the microhardness of Sn3.5Ag solder with magnetic Ni particles

“…Because of the increasing awareness of environmental protection among the public, many countries have followed this practice and began to seek new lead-free solder to substitute the traditional harmful lead-based solder in the field of electronic packaging (Zeng and Tu, 2002;Lauro et al,2003;Seo et al, 2009;El-Ashram, 2005;Felberbaum et al, 2011;Wu et al, 2017). In recent years, the development of lead-free solder is very rapid and a variety of tin-based lead-free solder materials have appeared, such as Sn-Ag-Al (Xu et al, 2021), Sn-Bi (Xu et al, 2019), Sn-Cu (Kelly et al, 2021;Han et al,2021), Sn-3.5Ag-Cu (Shalaby et al, 2018), Sn-3.5Ag-xCu (Shalaby et al, 2017), Sn-Ag (Gumaan, 2020;Wang et al,2019), Sn-Ni (Lin, 2021;Liu et al,2019), Sn-Zn (Hu, 2021).…”