IEC 60664-3:2016

Overview

IEC 60664-3:2016 - "Insulation coordination for equipment within low-voltage systems - Part 3: Use of coating, potting or moulding for protection against pollution" specifies how coating, potting, or moulding can be used as permanent pollution protection to allow reductions in required clearance and creepage distances (as referenced in IEC 60664-1 / IEC 60664-5). The standard defines two protection types: type 1 (improves the micro-environment) and type 2 (treated as similar to solid insulation). It also establishes test methods, conditioning procedures and acceptance criteria for protected assemblies such as PCBs, substrates and multi-layer boards.

Key Topics

• Scope and application: Applies to permanent protective systems on printed wiring boards, terminals and rigid assemblies; excludes assemblies after repair.
• Protection types:
  • Type 1: Improves microenvironment under the protective layer (less stringent than solid insulation).
  • Type 2: Considered equivalent to solid insulation - enables greater reduction of creepage/clearance.
• Design and dimensioning: Rules that permit reduced spacing only when appropriate protection and testing are applied; reference to minimum spacings (see standard Table 1 for type 2).
• Testing requirements:
  • Visual examination and scratch-resistance test (scratch test applies to type 2 protection only).
  • Environmental conditioning: cold, dry-heat, rapid temperature change, damp heat with polarizing voltage, and electromigration conditioning.
  • Electrical/mechanical tests after conditioning: adhesion, insulation resistance, AC withstand voltage, and partial discharge extinction voltage.
  • Additional tests: resistance to soldering heat, flammability, solvent resistance, where applicable.
• Specimens and test boards: Guidance for preparing coated/potted/moulded specimens and printed wiring board configurations for testing.
• Notable updates in 2016 edition: interpolation guidance added; scratch test limited to type 2 and renumbered; Annex A tables separated for clarity.

Applications

• Use by electrical designers, safety engineers, and PCB manufacturers to justify reduced creepage/clearance with permanent encapsulation.
• Reference for component suppliers and assembly houses when specifying coatings, potting compounds or moulding processes for low-voltage equipment.
• Essential for test laboratories and certification bodies performing environmental and electrical testing on protected assemblies.
• Useful to standards committees defining product-specific insulation requirements.

Related Standards

• IEC 60664-1 and IEC 60664-5 - overall insulation coordination and clearance/creepage rules.
• IEC 60068 series - environmental test methods referenced for conditioning procedures.

This standard helps ensure safe, reliable pollution protection in low-voltage systems while allowing optimized PCB and assembly designs when coating, potting or moulding are applied.