More than just optics
The deposition of metallic layers on material surfaces by means of galvanic, chemical or physical deposition processes is common practice in almost all industrial sectors. They serve, for example, to change the optical properties of lenses, as a barrier layer in semiconductor structures, as corrosion protection or simply to improve the visual appearance of plastic or paper surfaces. When disruptions of the deposited layers occur in the form of flaking, abrasion, corrosion, surface adhesion failure or flawed optical properties, then surface analysis methods are often used in the investigation of the underlying cause. They can be used to characterize trace impurities on, in or between individual layers, to determine the layer thickness or to elucidate the structure of entire layer systems.
Adhesive failure of a metallic coating
A two-component metallic coating occasionally showed too little adhesion to the underlying substrate. The interface of such an area could be exposed by grinding a specimen embedded in epoxy resin. With the help of a ToF-SIMS mapping (imaging) fatty acid conjugates were identified as the cause of the adhesion failure. Based on this result, the substrate pretreatment (cleaning and activation) was checked and improved accordingly.
|Fatty acid conjugates|
In cases of pronounced delamination usually less expensive methods for preparation are used instead of the grinding technique used here. Often layers can be released with the help of adhesive tape and a cross-hatch or even by simple mechanical prying with a surgical blade. Subsequently, the back of the delaminated coating and the exposed surface of the substrate are chemically analized for the presence of any adhesion reducing substances (e.g., mineral oils, polysiloxanes, etc.).