Cleaning processes

When is a surface clean??

Cleaning processes are indispensable in the manufacture of almost all industrial goods. Cleaning operations, that can be complex, serve to remove unwanted layers or particles from surfaces to ensure the quality of either subsequent processes (e.g., paint coating, plating, curing) or the purity of the final products. The following shows an example of the surface of an optical filter, illustrating how modern surface analytical methods can contribute to the optimization of cleaning processes.


Optimization of cleaning processes

Analysis of cleaning residue with Tof-SIMS Imaging

Secondary ion mass spectrometry (ToF-SIMS) was used to investigate the outcome of purification processes that occur during the production of optical filters. Static ToF-SIMS analyses were performed to determine the chemical composition of the glass surfaces before and after cleaning. On the basis of the ToF-SIMS data, organic contaminants such as triglycerides and dodecylbenzenesulfonate were identified on the special glasses prior to cleaning. After wiping the optics with acetone at the end of the cleaning, the proportion of these substances was significantly reduced. Nevertheless, in the subsequent coating of the glass surfaces point defects in the adhesion were observed. Therefore, in a second analysis step, the lateral distribution of organic residues on cleaned glass surfaces was analyzed by imaging on 60x60 mm² field of view ("macroscan").

The secondary ion images shown here demonstrate that dodecylbenzenesulfonate salts and oxygen-containing hydrocarbons can be detected and localized also after the purification procedure. Based on these and other data, the dripping and wiping of acetone was identified as a production issue and replaced with a more effective purification step.

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