Development of holmium doped eutectic Sn-Ag lead-free solder for electronic packaging

Abstract

Purpose This study aims to summarize the effects of minor addition of Ho REE on the structure, mechanical strength and thermal stability of binary Sn- Ag solder alloys for high-performance applications. Design/methodology/approach This study investigates the effect of a small amount of holmium addition on the microstructure, thermal stability, mechanical behaviour and wettability of environmentally friendly eutectic melt-spun process Sn – Ag solder alloys. Dynamic resonance technique, X-ray diffraction (XRD) and scanning electron microscopy were carried to study stiffness, identification of the phases and the morphology features of the solder. Structure and microstructure analysis indicated that presence of rhombohedral ß-Sn phase in addition to orthorhombic IMC Ag3Sn phase dispersed in Sn-matrix. Also, the results showed that Ho rare earth addition at a small trace amount into Sn-Ag system reduces and improves the particle size of both rhombohedral ß-Sn and orthorhombic IMC Ag3Sn based on the adsorption effect of the active RE element. The adsorption of Ho at grain boundaries resulted in Ag3Sn more uniform needle-like which is distributed in the ß-Sn matrix. The fine and uniform microstructure leads to improvement of mechanical strength. The microstructure refinement is due to the high surface free energy of IMC Ag3Sn grains, and it prevents the dislocation slipping. This maybe enhance the micro-hardness and micro-creep hence delays the breaking point of the solder. Ho (RE) trace addition could enhance the melting temperature and contact angle up to 215°C and 31°, Respectively, compared with plain solder. All results showed that Ho trace addition element has an effective method to enhance new solder joints. Findings Effect of rare earth element Ho particles on the microstructure and mechanical behavior of eutectic Sn-3.5Ag solder alloy was studied. Some important conclusions are summarized in the following: microstructure investigations revealed that the addition of Ho particles to eutectic Sn-3.5Ag inhibited in reducing and refines the crystallite size as well as the Ag3Sn IMC which reinforced the strength of plain solder alloy. The mechanical properties values such as Young’s modulus, Vickers microhardness of Sn-3.5Ag solder alloy can be significantly improved by adding a trace amount of Ho particles compared with plain solder due to the existence of finer and higher volume fraction of Ag3SnIMC. These variations can be understood by considering the plastic deformation. The strengthening mechanism of the Sn-3.5Ag-Ho solder alloy could be explained in terms of Ho harden particles and finer IMC, which are distributed within eutectic regions because they act as pinning centres which inhibited the mobility of dislocation that concentrated around the grain boundaries. The results show that the best creep resistance is obtained when the addition of Ho 0.5 is compared to plain solder. The addition of Ho on Sn-3.5Ag lead-free solder alloy decreases the melting temperature to few degrees. Originality/value Development of holmium-doped eutectic Sn-Ag lead-free solder for electronic packaging.

Effect of TiO2 nanoparticles on the microstructure, mechanical and thermal properties of rapid quenching SAC355 lead-free solder alloy

“…It is defined as Q −1 = Δ W / W where Δ W is the energy dissipated and W the energy stored during one cycle. Therefore, the measurement of internal friction can be used to obtain information about the microstructure of the material in a non-destructive way (Shalaby, 2022). By using the resonance curves shown in Figure 5, the internal friction was measured at room temperature for the melt-spun ribbons.…”

Effect of Ce and Sb doping on microstructure and thermal/mechanical properties of Sn-1.0Ag-0.5Cu lead-free solder

“…On the one hand, Sn tends to react with Sb to form SnSb particles, thus inhibiting the formation of Cu 6 Sn 5 and the coarsening of Ag 3 Sn at the interface. On the other hand, the heterogeneous nucleation rate increased by reducing the thermodynamic barrier with the Sb doping, leading to grain refinement (Shalaby, 2022). The mechanism of Ce inhibiting IMC growth at the interface is similar to that of Sb, which forms SnCe compounds and uses them as nucleation centers to refine IMC and inhibit their growth.…”

ZnO nanoparticles and compositional dependence of structural, thermal, mechanical and electrical properties of eutectic SAC355 lead-free solder

“…As shown in Table 1, the crystalline size of the β-Sn increased as the concentration of ZnO NPs increased, except for 0.5 and 1.0 Wt.% ZnO NPs, where the crystalline size decreased. According to the microstructure study, the increased elastic modulus could be attributed to the increased crystalline size of β-Sn in the (SAC355) 100- x (ZnO) x NPs solder alloys (Shalaby, 2022). As a result, it has been reported that the addition of ZnO NPs increases the elastic modulus of the Sn–Ag–Cu solder alloys, possibly because of the softening effect of the ZnO NPs particles in the ternary solder (Skwarek et al , 2021; Yousri et al , 2018).…”