Conformal coatings vary in their material-specific properties when used as protective films for electronic assemblies. Understanding the operational traits of different coating types and their interaction with assembly components is crucial for effective film application. Challenges in selecting and applying conformal coatings stem from possible post-application issues such as:
- Abrasion
- Corrosion
- Mismatched CTEs
- Outgassing
- Trapped moisture/residue
- Rework/repair
Stringent professional standards and specifications are in place to uphold quality control for the operational and material aspects of conformal coatings. Companies adhering to these top-tier industry standards receive quality certifications as a testament to their commitment. Certification denotes a conformal coating service provider’s unwavering dedication to delivering superior coatings, ensuring peak functionality, reliable performance and product longevity.
Listed below are a variety of standards and certifications that conformal coatings companies can comply with. Please note that this list is not exhaustive.
American National Standards Institute (ANSI), ESD S20-20 – Sets standards for protecting electrical/electronic parts, assemblies and equipment susceptible to ESD damage.
AS9100 – 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, AS9100 focuses on development/documentation and administration of QMS for conformal coating, with a commitment to customer support.
International Organization for Standardization (ISO) 9001: – An independent international, non-governmental organization, ISO provides world-class specifications for products, services and systems, to ensure quality, safety and efficiency. ISO 9001 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, IPC 9001 specifies QMS-guidelines for customer satisfaction through ongoing systemic improvement, while conforming to applicable statutory and regulatory requirements.
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
- Technological changes
- Customized to program applications
- For obtaining cost-effective, best-quality coating solutions
National Aerospace and Defense Contractors Accreditation Program (Nadcap®) accreditation for conformal coating of electronics – printed board assemblies – 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.
Surface Mount Technology Association (SMTA) – Provides instruction/accreditation for conformal coating application, masking and rework/removal processes, including those for microsystems and emerging technologies.
