The effect of the pre-treatment of metal foil on Sulfur's Corrosive Reaction Rate in Flower of Sulfur test

In recent years, the data center reliability is paid more attention due to in cloud computing application. In general, the longer term reliability requirement is concerned for it than in general products when in service life. With the more and more severe environmental pollution, the air quality will also directly or indirectly influence the life of data center wherever indoor and outdoor. The air pollution usually has many sources, such as automotive emissions, heavy industrial emissions, volcanoes, landfill sites and so on. Various air pollutant rich in oxide, chloride and sulfur can potentially cause electrical function failure due to creep corrosion phenomenon on electronic equipment. Besides, the haze can also accelerate the creep corrosion, especially in northeast region of China. Therefore, it is necessary to develop an effective methodology to estimate the failure model and extend the life of the data center, as well as the reliability qualification method for material selection whatever in PCB design and surface finish. Currently, there are 3 kinds of popular methods to simulate the contaminated air atmosphere in the industry. They are Mixing Flowing Gas (MFG), Chavant Clay and Flower of Sulfur (FoS) tests. MFG is a precise method able to combine various corrosive gases in the chamber for real environmental simulation while FoS and Clay method only take sulfur containing gas into account. However, the pre-treatment of metal foil is a crucial factor for corrosion rate model building whatever which one method. In this paper, chemical etching and mechanical polishing treatments will be carried out and compared with non-treatment for silver and copper foils. Surface morphology and the residue of metal oxide will be exhibited and identified. Besides, the pre-treatment effect on corrosion rate which will be discussed in FoS test. Several analytical methods were used in this work, including, Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray spectroscopy (EDX), Atomic Force Microscopy (AFM), X-ray Photoelectron Spectroscopy (XPS) and Coulometric Reduction (CR) Analysis. On the other hand, three kinds of three kinds of conformal coating materials have been used to evaluate the corrosion resistance ability through FoS test, including PolyUrethane (PU), epoxy and silicone. Finally, we will find an effective pre-treatment of metal foil base on those evidences to determinate the more accurate failure model and extend the life of the data center in future.