Performance of 96.5Sn–3Ag–0.5Cu/fullerene composite solder under isothermal ageing and high-current stressing

Abstract

Purpose The purpose of this paper is to investigate the effect of fullerene (FNS) reinforcements on the microstructure and mechanical properties of 96.5Sn3Ag0.5Cu (SAC305) lead-free solder joints under isothermal ageing and electrical-migration (EM) stressing. Design/methodology/approach In this paper, SAC305 solder alloy doped with 0.1 Wt.% FNS was prepared via the powder metallurgy method. A sandwich-like sample and a U-shaped sample were designed and prepared to conduct an isothermal ageing test and an EM test. The isothermal ageing test was implemented under vacuum atmosphere at 150°C, whereas the EM experiment was carried out with a current density of 1.5 × 104 A/cm2. The microstructural and mechanical evolutions of both plain and composite solder joints after thermal ageing and EM stressing were comparatively studied. Findings A growth of Ag3Sn intermetallic compounds (IMCs) in solder matrix and Cu-Sn interfacial IMCs in composite solder joints was notably suppressed under isothermal ageing condition, whereas the hardness and shear strength of composite solder joints significantly outperformed those of non-reinforced solder joints throughout the ageing period. The EM experimental results showed that for the SAC305 solder, the interfacial IMCs formulated a protrusion at the anode after 360 h of EM stressing, whereas the surface of the composite solder joint was relatively smooth. During the stressing period, the interfacial IMC on the anode side of the plain SAC305 solder showed a continuous increasing trend, whereas the IMC at the cathode presented a decreasing trend for its thickness as the stressing time increased; after 360 h of stressing, some cracks and voids had formed on the cathode side. For the SAC305/FNS composite solder, a continuous increase in the thickness of the interfacial IMC was found on both the anode and cathode sides; the growth rate of the interfacial IMC at the anode was higher than that at the cathode. The nanoindentation results showed that the hardness of the SAC305 solder joint presented a gradient distribution after EM stressing, whereas the hardness data showed a relatively homogeneous distribution in the SAC305/FNS solder joint. Originality/value The experimental results showed that the FNS reinforcement could effectively mitigate the failure risk in solder joints under isothermal ageing and high-current stressing. Specifically, the FNS particles in solder joints can work as a barrier to suppress the diffusion and migration of Sn and Cu atoms. In addition, the nanoidentation results also indicated that the addition of the FNS reinforcement was very helpful in maintaining the mechanical stability of the solder joint. These findings have provided a theoretical and experimental basis for the practical application of this novel composite solder with high-current densities.

Research Status of Evolution of Microstructure and Properties of Sn-Based Lead-Free Composite Solder Alloys

“…Kumar et al [85,86] confirmed that the addition of CNTs could refine the microstructure of SAC solder. The other carbon-based nanomaterials of FNSs was also added into SAC305 solder [41,43]. They confirmed that the grain size of β-Sn displays an evident reduction trend with the addition of FNSs.…”

“…Consequently, trace amount of alloying elements (Ni [8][9][10], Mn [11], Bi [12], Co [13,14], Cr [15], Al [9], Sb [10], Fe [16], and rare earth (RE) [17,18]) is incorporated with Sn-based lead-free solder to enhance the comprehensive properties. Moreover, with the popularity and utilization of nanometer materials fabricating technology, the nanometer particles are doped with Sn-based lead-free solder to improve the comprehensive properties, such as nanometer oxide (Al 2 O 3 [19][20][21], BaTiO 3 [22], Y 2 O 3 [23], TiO 2 [24][25][26][27], and ZrO 2 [28,29]), nanometer carbide ( [30,31]), nanometer IMC (Cu 6 Sn 5 [32][33][34]), and carbon-based nanometer materials (carbon nanotubes (CNTs) [35][36][37], graphene [38][39][40], and fullerenes [41][42][43]). Generally speaking, the addition of nanoparticles acts as reinforcing phase in the Sn-based lead-free composite solder alloys.…”

Research Overview on the Electromigration Reliability of SnBi Solder Alloy

“…Fullerene (FNS) nanomaterial exhibits excellent electrical properties. Incorporating fullerene FNS in the study resulted in a reduction in the average thickness of the Cu 6 Sn 5 (IMC) layer at the initial composite solder joint interface compared to conventional solder joints [ 113 ]. The FNS particles in the solder joint can act as barriers to inhibit the diffusion and migration of Sn and Cu atoms [ 114 ].…”

Effect of Carbon Nanotubes on the Mechanical, Thermal, and Electrical Properties of Tin-Based Lead-Free Solders: A Review

“…Alloying or particle-strengthening methods can address these shortcomings [7]. In particular, doped nanomaterials have attracted significant interest in developing high-performance tin-based, lead-free solders [8][9][10].…”