Preparation of pine-like Cu-Ni-P coating and its application in 3D integration

A hierarchically structured Cu-Ni-P film fabricated via one-step route of electroless plating is reported. The morphology of deposits can be controlled by adjusting the additive in electrolyte. Due to the synergistic crystalline modification of polyethylene glycol (PEG), Janus Green B (JGB) and Cl − , the as-prepared Cu-Ni-P film exhibits pine-like architecture, about 2 µm in height and 1.5µm in root diameter. EDX result reveals that the pine-like coating is composed of about 94% Cu, 5%Ni and 1% P (weight %). Combined with the results of Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM), it can be seen that the pine-like Cu-Ni-P structure is ploy-crystalline. Bonding test shows that the adhesion strength between Sn and pine-like Cu-Ni-P substrate is about 8.4MPa. The reason for the excellent bonding performance could be ascribed to the mechanical interlocking effect caused by the roughened surface, which is proved to be an effective way to achieve low temperature bonding of Sn and Cu.