... not merely interested in particles!
Washing and cleaning processes are of great importance in the manufacture of complex technical products. They serve for example:
- elimination of passivation and corrosion protection layers before further processing.
- removal of particles.
- preparation and activation of surfaces before coating.
- improvement of solderability, ...
To control cleaning processes, optical assessments and the use of color references are established methods. However, if particles are persistent or there is evidence of a contamination film, more detailed analysis is needed to identify potential sources of contamination. Depending on the exact issue at hand, the use of methods such as SEM/EDX, FTIR or ToF-SIMS is helpful.
Cleaning of metal surfaces
ToF-SIMS to control the cleaning process
Before many process steps in the processing of metals, a thorough surface cleaning is necessary. When the result of the cleaning is insufficient, naturally the question arises which components have remained on the treated surface. For very thin or sheeted surfaces, ToF-SIMS analysis can help to identify sources of contamination. In addition, the effect of a reliably functioning cleaning process can be documented by analyses before and after a cleaning step, as the following example shows:
The illustrated parts of ToF-SIMS spectra show the chemical changes on a stainless steel surface caused by a cleaning process (surfactant solution & ultrasound). Mineral oil and fats are clearly detected on the unwashed surface. The spectrum of negatively charged secondary ions can even be used to distinguish individual fatty constituents (for example palmitate (255 u), arachidate (311 u)). After rinsing, the intensities of the characteristic mineral oil and fatty acid signals are significantly reduced.