Overview
IEC 61189-5-503:2017 - Test methods for electrical materials, printed board and other interconnection structures and assemblies - Part 5-503 defines a general test method for Conductive Anodic Filament (CAF) testing of circuit boards. The standard specifies test types and conditions used to provoke and detect CAF growth in multilayer printed circuit boards (PCBs), including steady-state temperature/humidity, temperature–humidity cyclic tests, and an unsaturated pressurized vapor test (HAST). It provides guidance on test specimen design, measurement methods and test procedures to assess insulation degradation caused by CAF.
Key topics and technical requirements
- CAF definition and scope: Describes conductive anodic filament formation and the environmental stresses that encourage CAF in PCBs.
- Test methods: Specifies three principal tests:
- Steady‑state temperature and humidity
- Temperature–humidity cyclic test (including 12 h + 12 h cycles)
- Steady‑state high temperature and high humidity (unsaturated pressurized vapour / HAST)
- Specimen and test vehicle design: Guidance for CAF test board layouts, including evaluation patterns for glass cloth direction and plated-through via arrangements (examples A and B).
- Measurement and instrumentation: Insulation resistance measurement methods (manual and automatic), required equipment (environmental chambers, power supplies, current‑limiting resistors, wiring and fixtures).
- Test procedure and judgment: Pre-screening (opens/shorts), cleaning, preconditioning, set-up, test voltages, measurement intervals, visual inspection criteria and end-of-test judgment states.
- Documentation and repeatability: Number of specimens, test conditions and cycle counts, and example figures/tables to ensure consistent implementation.
Practical applications
- Qualifying PCB materials and stackups for reliability in humid or high‑temperature environments.
- Identifying susceptibility to CAF for high‑reliability sectors such as automotive, telecommunications, aerospace, medical devices and industrial electronics.
- Supporting failure analysis and root‑cause investigations where insulation breakdown or intermittent electrical leakage is suspected.
- Informing material selection and process controls for PCB laminates, surface treatments and via fabrication.
Who should use this standard
- PCB manufacturers and fabricators performing reliability qualification
- Electronics reliability and quality engineers
- Materials suppliers and laminate manufacturers
- Independent test laboratories and R&D teams conducting CAF susceptibility testing
- Design engineers specifying PCB stackups for harsh environments
Related standards
- IEC 61189 series (other test methods for electrical materials and printed boards)
- Environmental test standards such as IEC 60068‑2‑66 (temperature and humidity test methods)
Keywords: IEC 61189-5-503, Conductive anodic filament, CAF testing, circuit boards, PCB reliability, HAST, temperature-humidity cycling, insulation resistance testing.
Open preview (PDF)Test methods for electrical materials, printed board and other interconnection structures and assemblies - Part 5-503: General test method for materials and assemblies - Conductive anodic filaments (CAF) testing of circuit boards
