BS EN 61249 - 3-4-1999 Standard Introduction BS EN 61249 - 3-4-1999 is a European standard on materials for flexible printed boards, specifying performance requirements and test methods for coated and uncoated non-reinforced substrates such as adhesive-coated flexible polyimide films. The standard applies to materials for the manufacture of flexible printed boards and focuses on the mechanical, electrical and chemical properties of materials to ensure their Reliability and durability in electronic devices. The standard also addresses key indicators such as Appearance, dimensional tolerances, adhesion, heat resistance and chemical resistance of materials, providing manufacturers and users with a clear basis for quality control.