Coatings on strongly curved surfaces

In PVD processes, the coating layer does not grow up with homogeneous layer thickness over substrate surfaces, which is due to the nature of the process using directed particle flux. Therefore, the layer thickness varies laterally. The optical and mechanical properties of the resulting coating follow the resulting layer thickness gradient.

These effects can be counteracted in many cases by targeted adaptation of the coating design but especially on strongly curved surfaces, those effects may lead to insufficient results.

To minimize the layer thickness gradient and the associated performance effects, substrates with rotationally symmetrical surface shapes can be put into self-rotation by means of planetary gears.

In other cases, the precise control of thickness gradients opens the option to tailor the optical response to the optic's designated application such as various illumination conditions.

Opcos AG developed a very flexible planetary fixture in order to cover a wide range of product requirements. In addition, the lateral layer thickness gradient for a given surface can be estimated and optimized by means of an in- house simulation software which significantly reduces the expenditure for optimization test in this regard.