Purpose The purpose of this paper is to investigate the effect of nickel-plated graphene (Ni-GNS) on the microstructure and mechanical properties of 96.5Sn3Ag0.5Cu (SAC305) lead-free solder joints before and after an electro-migration (EM) experiment. Design/methodology/approach In this paper, SAC305 solder alloy doped with 0.1 Wt.% Ni-GNS was prepared via the powder metallurgy method. A U-shaped sample structure was also designed and prepared to conduct an EM experiment. The EM experiment was carried out with a current density of 1.5 × 104 A/cm2. The microstructural and mechanical evolutions of both solder joints under EM stressing were comparatively studied using SEM and nanoindentation. Findings The experimental results showed that for the SAC305 solder, the interfacial intermetallic compounds (IMC) formulated a protrusion with an average height of 0.42 µm at the anode after 360 h of EM stressing; however, despite this, 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, while 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/ Ni-GNS composite solder, a continuous increase in the thickness of the interfacial IMC was found on both the anode and cathode side; 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, while the hardness data showed a relatively homogeneous distribution in the SAC305/ Ni-GNS solder joint. Originality/value The experimental results showed that the Ni-GNS reinforcement could effectively mitigate the EM behavior in solder joints under high current stressing. Specifically, the Ni particles that plated the graphene sheets can work as a fixing agent to suppress the diffusion and migration of Sn and Cu atoms by forming Sn-Cu-Ni IMC. In addition, the nanoidentation results also indicated that the addition of the Ni-GNS 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.

中文翻译：

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高电流密度应力下Ni包覆石墨烯掺杂SAC305无铅复合焊料可靠性研究

目的本文的目的是研究镀镍石墨烯 (Ni-GNS) 在电迁移 (EM) 前后对 96.5Sn3Ag0.5Cu (SAC305) 无铅焊点的微观结构和机械性能的影响实验。设计/方法/途径 在本文中，SAC305 焊料合金掺杂 0.1 Wt.% Ni-GNS 是通过粉末冶金方法制备的。还设计并准备了 U 形样品结构以进行 EM 实验。EM 实验以 1.5 × 104 A/cm2 的电流密度进行。使用 SEM 和纳米压痕对两种焊点在 EM 应力下的微观结构和机械演变进行了比较研究。结果 实验结果表明，对于 SAC305 焊料，经过 360 小时的 EM 应力后，界面金属间化合物 (IMC) 在阳极处形成了一个平均高度为 0.42 µm 的突起；然而，尽管如此，复合焊点的表面还是比较光滑的。在施压期间，SAC305素面焊料阳极侧界面IMC呈现持续增加的趋势，而阴极侧IMC随着施压时间的增加，其厚度呈下降趋势；加压 360 小时后，阴极侧形成了一些裂纹和空隙。对于 SAC305/Ni-GNS 复合焊料，发现阳极和阴极侧的界面 IMC 厚度不断增加；阳极界面IMC的生长速率高于阴极。纳米压痕结果表明，SAC305焊点的硬度在EM应力后呈现梯度分布，而硬度数据显示SAC305/Ni-GNS焊点的硬度分布相对均匀。原创性/价值 实验结果表明，Ni-GNS 增强材料可以有效减轻高电流应力下焊点中的电磁行为。具体来说，镀在石墨烯片上的镍颗粒可以作为固定剂，通过形成 Sn-Cu-Ni IMC 来抑制 Sn 和 Cu 原子的扩散和迁移。此外，纳米识别结果还表明，Ni-GNS 增强剂的加入对维持焊点的机械稳定性非常有帮助。