Richard, As Joyce already pointed out, air, more specifically oxygen, will terminate the polymerization of the free radical monomer. Those familiar with Parylene have likely experienced a vacuum leak at some location in the chamber. The Parylene near the point of the leak, depending on the severity of the leak, may be opaque, cloudy, or white. If the substrate outgasses, then there will be a competing effect between molecules leaving the substrate's surface and the monomer molecules trying to deposit on the surface. I have not seen any areas completely void of Parylene, but the area of outgassing may be thinner than other areas that do not outgas. At some point, the rate of outgassing decreases and is overcome by the Parylene deposition, which further seals the surface and further slows the outgassing from the substrate. I have not experienced anything 'poisoning' the polymerization process. For the polymerization to not occur, something would have to react with all the CH2's to prevent the Parylene from growing. As Doug stated, contaminants usually impact adhesion. Lamar Young Specialty Coating Systems, Inc. 7645 Woodland Dr. Indianapolis, IN 46278 (317) 244-1200 Ext. 276 www.scscoatings.com From: Douglas Pauls <[log in to unmask]> To: <[log in to unmask]> Date: 08/29/2013 10:26 AM Subject: Re: [TN] Poisoning of Parylene Polymerization Sent by: TechNet <[log in to unmask]> Rich, The one to answer this would probably be Lamar Young at SCS in Indianapolis. I know that in our Parylene machines, we regularly clean the pyrolysis tube where the dimer decomposes to the monomer and the reaction occurs. I don't think contaminants on the board would have much effect, other than perhaps interfering with adhesion. Do you have much unused dimer at the end of a deposition run? If so, does it look really burnt? Is your dimer powder old or has it been stored improperly? Doug Pauls From: Richard Kraszewski <[log in to unmask]> To: <[log in to unmask]> Date: 08/28/2013 03:54 PM Subject: [TN] Poisoning of Parylene Polymerization Sent by: TechNet <[log in to unmask]> Is anyone aware of any specific contaminants that can poison the polymerization process in parylene type coatings? Rich Kraszewski ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________