Effect of Consecutive Plasma Polymerizations

This film system was seen to outperform others not incorporating the adhesion-promoting HFE film when a primer is applied to the LCVD coated alloy surface. The alloy panels were always treated with O2 plasma to remove any organic contaminants from the alloy surface prior to film deposition. The entire steps involved in the plasma coating process are  

Solvent cleaning of the alloy surface with acetone 

Steps 2-4 were carried out in a vacuum reactor consecutively. Thus, the plasma reactor follows the cycle (1) pump down from ambient environment (2) O2 plasma (3) TMS plasma (4) HFE plasma (5) exposure to ambient air. The sequences of plasma processes are O2/TMS, TMS/HFE, and HFE/O2, or can be expressed -(02/TMS/HFE/)-. 

It is important to note that plasma deposition occurs predominantly on the cathode surface in the cathodic polymerization, and a new cathode (substrate) was used in every plasma coating operation. In other words, the contamination of the reactor is considered to be minimal. 

This reversal of the sequence from TMS/HFE to HFE/TMS is the most important issue. The second major issue is the effect of the O2 plasma treatment on the fluorine-containing contaminants. The XPS analysis of an initial sample revealed virtually no silicon on the alloy surface beneath the lifted primer but did indicate a rather substantial fluorine presence. The appearance of a strong silicon signal on the interface side of the removed primer indicated that the entire plasma film had likely delaminated at the interface with the alloy. Analysis of additional samples confirmed that the entire film and primer system had delaminated from the alloy panels. 

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