The reliability study on electrochemical migration evaluations for common substrates in power electronics

The miniaturized electronic devices are driving the development of higher density and integration of smaller components, which leads to reliability issues for electronic devices in harsh environments such as high temperature and high voltage. Electrochemical migration (ECM) is an important phenomenon related to the failure of electronic devices, causing short-circuit failures between closed metal surfaces and significantly reducing the reliability of electronic products. Moreover, the complexity of the materials used in modern circuit boards, the increased number of component pins and the reduced spacing of multilayer boards have all increased the risk of failure from electrochemical migration, making it an unavoidable failure threat in the reliability of electronic packaging. Recently, silicon nitride (Si₃N₄) ceramics have received wide attentions due to their excellent mechanical properties, such as high bending strength and high fracture toughness. The Si₃N₄ substrate is not only responsible for electrical connections and mechanical support, but reliability is also important. However, the effect of Si₃N₄ ceramic substrate on the reliability of electrochemical migration is rarely studied.In this paper, we use the water drop (WD) test to investigate the effect of four commonly used substrate material types (aluminum nitride, alumina, silicon nitride, PCB) and bias voltages on electrochemical migration experiments in electronic products. The WD test was chosen due to the fact that results on the effect of conditions such as electrode spacing, bias voltage, ion type and concentration in the liquid on electrochemical migration can be obtained in a short time. During electrochemical migration, samples were recorded in situ under an ultra-deep field microscope (MPI TS150) for video of the entire WD process. The mean time to failure was determined based on the first sharp increase in current and the dendritic bridges observed under the optical microscope. In addition, the morphology of the dendrites and elemental analysis of the post-experimental samples were carried out by scanning electron microscopy (SEM), energy spectroscopy (EDS) and XPS, while the statistical electrochemical migration failure times were monitored in real time.