Hou Ruiqing, Zhang Keke, Zhao Wenjia, Zhang Haizhou, Zhang Chao, Wang Yonglei
School of Materials Science and Engineering, Henan University of Science and Technology, Luoyang, 471000, China.
Key Laboratory of Nonferrous Metals Science and Processing Technology in Henan Province, Luoyang, 471000, China.
Sci Rep. 2025 Mar 11;15(1):8420. doi: 10.1038/s41598-025-89492-1.
The Ni-P stratum was fabricated upon the Cu substrate via an electroless plating technique, and the microstructure and properties of electroless Ni-P/Sn2.5Ag0.7Cu0.1RE micro-joints under temperature gradient was studied. Research indicates that in the initial stage of thermomigration in micro-solder joints, the intermetallic compound (IMC) in the Ni-P/soldering seam transition area appears as both "needle-shaped" and "block-shaped" (Ni, Cu)Sn, with an average thickness of 1.1-1.5 μm. Additionally, between Cu and (Ni, Cu)Sn IMC, there exists a 0.8 μm thick "layered" NiP within the Ni-P layer. The temperature gradient causes the asymmetric growth of (Ni, Cu)Sn IMC and the asymmetric evolution of the Ni-P layer at the hot and cold ends of the micro-solder joint. The Ni-P layer evolution is divided into two stages: Ni-P → NiP + Ni and NiP + Sn → Ni-Sn-P, and the cold end structure evolves faster than the hot end. After 60 h under the temperature gradient condition of 550 °C/cm, the shear fracture position of the micro-solder joint shifts from the soldering seam to the Ni-Sn-P/IMC layer junction, and fracture mode changes from ductile fracture dominated by dimples to brittle fracture dominated by cleavage and slip steps, corresponding to a decrease of 21.8% in micro-solder joint pushing shear force from 16N.
通过化学镀技术在铜基板上制备了Ni-P镀层，并研究了化学镀Ni-P/Sn2.5Ag0.7Cu0.1RE微焊点在温度梯度下的微观结构和性能。研究表明，在微焊点热迁移的初始阶段，Ni-P/焊缝过渡区的金属间化合物（IMC）呈现为“针状”和“块状”（Ni, Cu）Sn，平均厚度为1.1-1.5μm。此外，在Cu与（Ni, Cu）Sn IMC之间，Ni-P层内存在一层厚度为0.8μm的“层状”NiP。温度梯度导致微焊点热端和冷端的（Ni, Cu）Sn IMC不对称生长以及Ni-P层不对称演变。Ni-P层的演变分为两个阶段：Ni-P→NiP+Ni和NiP+Sn→Ni-Sn-P，且冷端结构的演变比热端快。在550°C/cm的温度梯度条件下60小时后，微焊点的剪切断裂位置从焊缝转移到Ni-Sn-P/IMC层交界处，断裂模式从以韧窝为主的韧性断裂转变为以解理和滑移台阶为主的脆性断裂，对应微焊点推剪力从16N下降了21.8%。
