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QPL Verification - A Key Element in Parylene Coating Specification


by William Gleason, General Manager at Para Tech Coating

Vacuum-deposited film has been used for decades to protect surfaces and components in aerospace electronics, medical technology, automotive and wide ranging industrial applications. While the Parylene formulation is molecularly specific, the Parylene dimer — the raw form of the coating — varies in purity and performance from one manufacturer to another. A deficient dimer formulation will degrade the ability of finished Parylene film to protect critical assemblies under harsh conditions.

Threat of Substitution

Manufacturers of critical systems are threatened by the possibility that a subcontractor might substitute counterfeit or fraudulent components or materials for Mil-Spec assemblies and other high risk devices. Such unauthorized and potentially undiscovered substitutions threaten the performance and ultimate reliability of such assemblies. A chemically based material such as Parylene dimer presents a particular risk, since it is very difficult to detect an inferior, non-QPL (Qualified Product List) material apart from destructive testing, and effective coating encapsulation is a key component in system reliability.

Ensuring Dimer Quality

The Defense Logistics Agency manages QPL operations through its Defense Supply Center, Columbus (see The QPL certification program is intended to assist design engineers and circuit manufacturers with the complex task of analyzing and qualifying products and materials such as Parylene dimer to ensure they conform to standards and meet the high performance requirements of aerospace, defense, medical and other critical electronics applications. Today there are more than 30,000 products or components in eight categories that are covered by the ongoing QPL process.

Products submitted for QPL review are subject to extensive testing against detailed performance and quality requirements, and then validated by subsequent audits on a continuing basis. Products that achieve QPL status are listed by the Defense Logistics Agency Land and Marine in a qualified product database that is subject to ongoing additions, deletions and modifications.

QPL Rated Dimer - Worth the Investment

While non-QPL rated Parylene dimers may be sufficient for routine, non-critical coating tasks, there is no assurance that they meet the performance level required for the most demanding coating applications since they have not been subject to QPL testing. There may be no apparent difference in appearance between dimers of various suppliers, nor in their functionality for routine vacuum coating. Dimer performance can, in fact, only be determined by means of the thorough, sophisticated laboratory analysis involved in QPL testing. Higher performance, QPL-qualified Parylene raw material may be more expensive than non-conforming dimers, but substitution of an inferior, non-QPL material compromises the performance of sophisticated, mission-critical components, with potentially severe and costly consequences.

Therefore it is crucial for system specifiers and subcontracting decision makers to insist on the documented use of a QPL-listed Parylene dimer, along with optimal substrate cleaning, surface preparation and coating deposition procedure, in order to meet governing regulations.

The QPL program is a valuable resource for manufacturers as they identify and select a Parylene coating resource, as well as to those companies with in-house Parylene coating operations. Para Tech Coating (Para Tech) supplies QPL-rated Parylene raw materials that are approved per QPL-46058, as specified for products under MIL-I-46058. Para Tech is one of only a few U.S. providers of QPL-rated Parylene dimer to both coating service customers and in-house Parylene coating operations, as well as to other Parylene coating suppliers.

The QPL Process

Para Tech has continuously met the stringent demands of periodic QPL testing. Para Tech Quality Control Manager Patricia Langraphi explains that the QPL listing process begins with coating of test coupons using the dimer under review, and submitting them to an authorized third party laboratory for detailed analysis of physical and chemical properties, in accordance with MIL-I-46058C Standard guidelines. The results of these tests are submitted to the Defense Logistics Agency (DLA) for review and approval, and with DLA authorization, the material is listed on the QML/QPL database (see: QML/QPL database)

Associated Quality Issues

The QPL rating program for dimer supports the broader electronic manufacturing quality requirements of customers following the AS9100 standard. This standard incorporates the full scope of the original ISO 9000 program, along with additional requirements specifically related to aerospace and defense industries. As QPL approval is an essential requirement for raw material used on defense projects, QMS certification based on aerospace standard AS9100 is an essential requirement for companies doing business with aerospace and defense organizations.

Para Tech - The Certification Pace Setter

In 2008, Para Tech’s Aliso Viejo, California, headquarters became the first Parylene coating service facility in the country to achieve AS9000 QMS certification, and was subsequently upgraded to AS9100 Rev. C in 2011. In May, 2012, Para Tech’s Middletown, Connecticut, facility also achieved QMS certification based on AS9100 Rev. C.

According to Quality Assurance Manager Langraphi, maintaining AS9100 certification is a complex and continual process. “Our quality management system is based on a robust system, where AS9100 Rev. C requirements and quality principles are the foundation for all of our processes. Every aspect of our operation has been adjusted and refined to conform to the latest standard," Langraphi notes.

“We maintain certification based on a three-year cycle that involves verification of every individual process and of the entire system. A certification authority conducts periodic on-site audits to verify conformance of the QMS. The inability to demonstrate compliance to the standard requirements can result in major or minor non-conformance findings, and the possibility of suspension of certificate," she said.

“The results of periodic AS9100 audits are published in the Oasis database, which is open to review by coating service customers and prospects. Both our East Coast and West Coast Parylene coating facilities must operate on the basis on constant attentiveness to every aspect of quality in order to maintain the highest level of quality assurance. This is the standard of daily performance at Para Tech," Langraphi concludes.


The QPL rating of Para Tech dimer completes the circle of AS9100 requirements for fully competent vacuum deposition coating of electronic systems for the highest level of performance and customer peace of mind. This is a process that few providers are equipped to provide.

Well-meaning, established and otherwise competent companies may inadvertently use counterfeit materials or processes, and it is imperative that every link the supply chain pays close attention to detail to ensure compliance with both materials and methods requirements. If the quoted cost for a system element seems too good to be true, investigate the supplier closely to make sure that the quotation covers and verifies QPL listings, along with every other aspect of production quality.



Contact Curtiss-Wright Parylene Services with questions related to Parylene use in industrial and commercial coating applications, or for assistance with process development and full coating services for your products.


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We are ready to assist with your Parylene conformal coating needs and answer any questions about your specific product requirements.