Coated electrical assembly

An electrical assembly which has a multi-layer conformal coating 4 on at least one surface of the electrical assembly, wherein each layer of the multi-layer coating is obtainable by plasma deposition of a precursor mixture comprising (a) one or more organosilicon compounds, (b) optionally 02, N20, NO2, H2, NH3, N2, SiF4 and/or hexafluoropropylene (HFP), and (c) optionally He, Ar and/or Kr. The chemistry of the resulting plasma-deposited material chemistry can be described by the general formula: SiOxHYCZFaNb. The properties of the conformal coating are tailored by tuning the values of x, y, z, a and b. The electrical assembly may be an electrical component 3 mounted onto a substrate 1.