Conformal Coating Quality Standards
Posted by Sean Horn
Friday, September 15, 2017 8:18
@ 8:18 AM
Conformal coatings differ in their material-specific performance properties as protective films for electronic assemblies. Knowing the operational characteristics of various coating-types and their functional association with assembly components supports successful film application. Issues that confound conformal coating selection and application result from potential post-application problems like:
· mismatched CTEs,
· trapped moisture/residue, and
To this end, a range of professional standards and specifications have been created for conformal coatings to assure quality control of operational and material conditions.
Quality certifications are awarded firms that meet industry-best standards/specifications. Receiving certification represents a firm’s commitment to providing customers superior conformal coatings, ensuring optimal function, performance reliability and product-life.
These certificates are awarded conformal coating firms with appropriately implemented quality management systems (QMS) for their products and processes:
American National Standards Institute (ANSI), ESD S20-20 – Sets standards for protecting electrical/electronic parts, assemblies and equipment susceptible to ESD damage.
AS9100C – A widely accepted quality management system released by the Society of Automotive Engineers and the European Association of Aerospace Industries for aviation, space and defense applications, AS9100C focuses on development/documentation and administration of QMS for conformal coating, with a commitment to customer support.
International Organization for Standardization (ISO) 9001:2015 – An independent international, non-governmental organization, ISO provides world-class specifications for products, services and systems, to ensure quality, safety and efficiency. 9001:2015 is awarded firms that consistently provide products/services meeting customer satisfaction and applicable statutory/regulatory requirements, through QMS.
IPC 9001 — The Association Connecting Electronics Industries, IPC is a global trade organization accredited by ANSI for developing classification-standards pertinent to the conformal coating industry. IPC’s Class 3 Standard for Coating Requirements provides guidelines for maintaining reliable performance under challenging operational conditions. Like ISO 9001:2015, IPC 9001 specifies QMS-guidelines for customer satisfaction through ongoing systemic improvement, while conforming to applicable statutory and regulatory requirements. As an industry leader, Diamond MT has been a member of the IPC since January 2012. Other IPC standards applicable to provision of conformal coating services include:
IPC CLASS 3 Standard for Coating Requirements – Class 3 — High Performance Electronic Products — Includes products where continued high performance-on-demand is critical, minimal equipment downtime, and uncommonly harsh end-use environments, as for life-support or other critical systems.
IPC-7711/7721: Rework and Repair – Delineates appropriate processes for removing and replacing conformal coating; also stipulated are procedures for modification/repair of laminate material, conductors, solder, and plated through-holes.
IPC-A-610 Acceptability Standard – Provides illustrations of quality-acceptance requirements for PCB/assembly performance, that exceed minimal end-item operation criteria. Coating thickness requirements are set by IPC-A-610, according to the coating material and assembly function. Also provided are product classifications, according to function, in three categories. More explicitly:
· CLASS 1 — General Electronic Products, those whose primary requirement is efficient assembly function.
· CLASS 2 — Dedicated Service Electronic Products, focuses on extended PCB life and performance, where uninterrupted service is preferred but not critical, and end-use conditions are insufficient to cause assembly failure.
· CLASS 3 — High Performance/Harsh Environment Electronic Products, where minimal equipment-downtime and consistent performance-on-demand is required in harsh end-use environments, including aerospace, military, fire-control, life-support, or similar critical-system functions.
IPC-CC-830: Dictates appropriate qualification and conformance requirements for conformal coatings, delineating optimal-confidence criteria, and minimum test-redundancy for all conformal coatings types, encompassing three categories:
· Testing each product batch for quality of processes/materials for the specific coating assignment.
· Assuring quality-retention for a specified performance-duration, tested every two years.
· Coating quality conformance under these conditions, tested every year.
IPC-CC-830B — Qualification and Performance of Electrical Insulating Compound for Printed Wiring Assemblies – sets standards for maximal confidence in conformal coating performance under military-grade/ruggedized performance conditions.
National Aeronautics and Space Administration (NASA)-STD-8739.1 — An independent agency of the executive branch/U.S. federal government responsible for aeronautics/aerospace research and the civilian space program. Sets practice/documentation requirements for reliable conformal coating of PCBs and related electronic assemblies, including fabrication/inspection procedures for:
- NASA-generated assignments,
- specialized coating processes,
- supplier innovations, or
- technological changes
- customized to program applications,
- for obtaining cost-effective, best-quality coating solutions.
National Aerospace and Defense Contractors Accreditation Program (NADCAP) Audit Criteria for Circuit Card Assemblies AC7120 Rev A – NADCAP provides QMS accreditation for firms doing business with the aerospace industry. For conformal coatings:
- AC7120 Rev A sets test guidelines/performance criteria for conformal coating use on aerospace/defense PCBs/assemblies. Section 14, Coating and Encapsulation provides specific auditing standards for conformal coating.
- AC7109 provides audit criteria for liquid conformal coatings.
- AC7109/2/Audit Criteria for Vapor Deposited Coatings Physical Vapor Deposition (PVD)-Chemical Vapor Deposition (CVD) covers audits for coatings like parylene, using vapor rather than liquid application methods.
Unfortunately NADCAP does not have a conformal coating specific specification, so it is impossible for a conformal coating company like Diamond-MT to become NADCAP certified.
Surface Mount Technology Association (SMTA) – Provides instruction/accreditation for conformal coating application, masking and rework/removal processes, including those for microsystems and emerging technologies.
To learn more about conformal coating application methods and the specifications that govern them, download our whitepaper now: