Nickel Nanoparticle/Carbon Films as an Interlayer To Improve the Stability of Solder Joints

The growth of brittle intermetallic compounds (IMCs) generated between a solder and a substrate is crucial for the reliability of solder joints. Therefore, it is necessary to control the growth of IMCs at the interface. Herein, we propose a strategy with the nickel nanoparticle/carbon (Ni&C) films as an interlayer to improve the stability of the solder joint. After adding the interface with the Ni&C film and reflowing for 450 s, the growth of IMCs decreased by 41.05%. After reflowing for 450 and 2100 s, the grain size in the 300 s-Ni&C/Cu substrate decreased by 14.34 and 20.50%, respectively, compared with the pure Cu substrate. Furthermore, the Ni&C film changes the microstructure of the interface and the diffusion pattern of elements, thus reducing the number of Kirkendall voids. As the reflow time increases, the scalloped IMCs are transformed to be prismatic, which can be well explained by the Gibbs–Thomson effect. The synergistic effect between Ni and carbon in Ni&C can jointly control the interface reaction and the growth of IMCs, with the Ni&C film acting as an inert barrier to inhibit the growth of IMCs.