Parylene Process Optimization and Other Vacuum Deposited CoatingsAuthors: Amanda Rickman
Company: Raytheon Corporation
Date Published: 11/18/2014 Conference: Symposium
Throughout Raytheon, many company sites perform vacuum deposited coatings including Parylene C. Each site independently established operation and maintenance procedures as well as masking methods and surface preparation techniques. Over the course of investigating many coating successes and failures internally, the need for standardizing and optimizing became apparent. Several factors contribute to a repeatable vacuum deposition coating process including pressure, material selection, surface preparation, and maintenance of the coating equipment. A series of process experiments were performed with Parylene depositions systems to create an optimized process with respect to run time, film quality, adhesion, and equipment downtime. The parameters were adopted within the company as standard operating procedures. Chamber pressure is a critical parameter for the Parylene deposition process, controlling both the deposition rate and the quality of the deposited film. In addition to chamber pressure, any leak within the coating system can also impact quality of the deposited film as well as have a detrimental effect on times associated with pump down, deposition, and the total cycle. This presentation will discuss optimization of chamber pressure during deposition cycles and a real-time, in-line leak check process. The leak check process verifies the absence of leak paths prior to starting the coating deposition process. If leaks are detected, the exact location can be pinpointed and quickly fixed. Leaks have been virtually eliminated using a simple process that production operators use as part of each deposition run start-up. Data has shown substantial improvements in the total cycle time of the Parylene deposition process. Material selection is critical for vacuum deposition systems, including cleaning agents for the equipment, masking materials and tooling that must be matched to the product to be coated. Outgassing considerations apply to all vacuum deposited coatings, and surface preparation topics apply to all coatings in general. Maintenance procedures were re-written to optimize the turnover of the equipment and reduce contamination introduced into the next product run. These procedures led to better equipment utilization and more consistent film adhesion. Each factor considered on its own is well established throughout industry. However, when packaged together as a standard operating procedure, more robust and cost efficient Parylene and other vacuum deposited coatings have become the baseline process for Raytheon.
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