Atomic Layer Deposition + Parylene Conformal Nanocoatings for Robust Corrosion Protection of Electronics

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The use of flexible and miniaturized electronic devices is continuously growing with the advancement of interconnect, microvia and microBGA technologies. While these advancements have offered many benefits to high speed and complex electronics applications, they also have some design and reliability challenges, including corrosion protection. The drive for ultra-thin conformal coatings that can provide long-term robust and reliable protection for electronics and their components in harsh environments is continuing. While advancement of conformal coatings, including plasma polymerized coatings, nano liquid coatings and ultra-thin vapor phase coatings, have been able to meet the requirements up to a certain extent, the need to have an ultra-thin, lightweight conformal coating option that can provide the moisture barrier and corrosion resistance to a hermetic level is still unmet. The Atomic Layer Deposition (or ALD) technique, which was introduced in late 1990’s, has been advancing in many applications as it deposits ultra-thin films (a few nanometers) of metal and metal oxides with a precise thickness and conformality. However, its use in general electronics has been limited due to its high temperature processing conditions. This paper introduces an advanced ALD conformal coating - both alone and in combination with Parylenes - that is applied at room temperature, making it suitable for printed circuit boards and other components to provide robust and reliable protection from corrosion and other harsh environments. To understand the effectiveness of this coating on electronics against corrosion resistance, the mixed flow gas (MFG) testing was performed using Chlorine (Cl2), Hydrogen sulfide (H2S), Nitrogen dioxide (NO2) and Sulfur dioxide (SO2) for the period of 21 days. A long-term evaluation results demonstrates a robust and reliable protection against severe corrosive environments. In addition to these beneficial properties, experiments demonstrate excellent corrosion resistance, adhesion to the substrate, electrical insulation and a significant (sixty-three times) improvement on Parylene C’s water vapor transmission rate when combined with ALD.