Effects of High Humidity and High Salt Spray Environments on Surface Properties of Direct Bonding Copper

Packaging degradation of power devices in a converter is easily caused by high humidity and high salt spray environments. The bonding interface between copper layer of direct bonding copper (DBC) and encapsulating materials inside a power device is destroyed by the salt spray, resulting in functional failure of devices. Surface properties of DBC-Cu are directly related to the encapsulating reliability of a power device. The corrosion process and products of copper have been discussed in high humidity and mixed atmosphere, while surface properties of DBC-Cu in high humidity and salt spray environments are seldom reported. In this paper, the surface roughness, hydrophobicity and corrosion rate of DBC-Cu in high humidity and high salt spray environments are investigated. Surface roughness and hydrophobicity of DBC-Cu are close to a multiple polynomials trend while the corrosion rate is presented as a single exponential trend with time during two environments. The precipitation process of corrosion products in two environments is the main reason for surface properties variation of DBC-Cu. Based on scanning electron microscope (SEM) and X‑ray diffraction (XRD), the composition and morphology of corrosion products are analyzed to reveal the corrosion process of copper surface. Research results are expected to be of great significance for analyzing the degradation mechanism of interface strength between DBC-Cu and encapsulating materials in high humidity and high salt spray environments, which can provide guidance for improving the interface strength and encapsulating reliability of power devices.