Deposition of thin layer barrier coating on plastics for barrier improvement is nowadays state of the art. To support online quality management of plasma processes the Institute of Plastics Processing (IKV) in Industry and the Skilled Crafts at RWTH Aachen University is investigating the use spectroscopic plasma monitoring. Plasma emissions are strongly associated to the process parameters such as pressure, applied power and gas flow. However, looking at complex or rapid processes there is still a lack of viable and reliable industrial quality management systems. In these cases, establishing a temporal link between process variables and plasma properties is a crucial factor in order to obtain quality-related data in real-time.
Based on the optical emission spectroscopy (OES) spectroscopic plasma monitoring can survey the plasma process in real-time and thus the treatment or coating processes. The advantage of this technique is its ability to monitor different process information, e.g., the condition of the processing chamber, like the degree of contamination the expected layer properties, such as barrier properties, scratch resistance or wettability or the reproducibility of batch processes.
With this in mind, a plant control system based on programmable logic controller (PLC) has been developed at IKV. In close collaboration with PLASUS Ingenieurbüro, Kissing, the PLASUS EMICON system was integrated into the plant control system via Profibus DP. All available process data can thereby be collected and analysed along with the measured plasma emissions simultaneously, so that preventive action can be taken even in complex and rapid processes. Time and cost expensive sample checks are reduced to a minimum by continuous in-process performance monitoring
Further investigations on process monitoring, for example automatic acquisition of process homogeneity in large area coating processes, are in progress.
Photo IKV: Plasma monitoring in action