High-speed Cu electrodeposition and its solderability

Abstract The effects of the plating current density ( j ) on the electroplated Cu microstructure, impurity distribution, and the solderability of the electroplated Cu were investigated. Analyses of electron backscatter diffraction and transmission electron microscopy showed that the Cu grain size ( D ) decreased from microscale to submicron-scale, and the predominant crystallographic orientation translated from [111]||ND + [101]||ND into [101]||ND (ND: Cu deposition direction) with increasing j . Time-of-flight secondary ion mass spectrometry analysis showed that the impurity content in the Cu platings (especially the Cl content) increased as a function of j . These investigations showed that j posed a significant influence on the characteristics of the electroplated Cu. Two intermetallic compound (IMC) species (η-Cu 6 Sn 5 and Cu 3 Sn) accompanied with some material defects (e.g., nanovoids and microcracks) formed at the solder/Cu pillar interface after reflow. The IMC (Cu 6 Sn 5 ) growth morphology and orientation, and the defect distribution were also strongly j -dependent. These j -dependent interfacial microstructures were closely related to different D and impurity contents of the Cu platings. The results of this study advanced our understanding of the effects of j on electrochemical metal deposition, and they were helpful in the development of the high-speed Cu electrodeposition technology.