IEC 61249-3-6:2026

Overview

IEC 61249-3-6:2026 is an international standard developed by the International Electrotechnical Commission (IEC) for materials used in circuit boards and other interconnecting structures. This document sets out the requirements for unreinforced base materials consisting of polytetrafluoroethylene (PTFE) filled laminate sheets of defined flammability (as determined by the vertical burning test) that are copper-clad. Applicable to PTFE filled unreinforced laminated sheets with thicknesses from 0.02 mm to 3.2 mm, the standard addresses the needs of designers, manufacturers, and users of printed circuit boards (PCBs) requiring high-performance flame-resistant materials.

Key aspects such as construction, material properties, electrical performance, mechanical tolerances, and conformity assessment are covered, ensuring consistency and safety in the application of these specialized laminates.

Key Topics

• Material Composition

  • PTFE or modified PTFE as base resin
  • Inorganic fillers (e.g., silicon dioxide, titanium dioxide, aluminium oxide, boron nitride) may be used
  • Copper-clad layers as per IEC 61249-5-1
  • No reinforcement (unreinforced base materials)

• Flammability Requirements

  • Defined by a vertical burning test according to IEC 61189-2
  • V-0 flammability (default unless otherwise specified)
  • Resist dripping and burning after flame application, ensuring the highest safety within electronic assemblies

• Electrical and Mechanical Properties

  • Surface and volume resistivity
  • Relative permittivity and dissipation factor
  • Electric strength, arc resistance, and dielectric breakdown
  • Peel strength of copper foil
  • Dimensional stability, thickness, and tolerance
  • Thermal properties such as decomposition temperature, Z-axis and X/Y-axis coefficient of thermal expansion

• Appearance and Quality Control

  • Visual inspection parameters for copper-clad and unclad faces
  • Permissible defect levels for indentations, scratches, wrinkles, and raised areas
  • Inspection and qualification procedures as defined in the standard

Applications

Materials that comply with IEC 61249-3-6:2026 are primarily used in the fabrication of printed circuit boards (PCBs) and other interconnecting structures in advanced electronics. The unique properties of PTFE-based copper-clad laminates make them well-suited for:

• High-frequency and RF electronic circuits
  PTFE laminates offer low dielectric loss and stable electrical properties at microwave frequencies, making them ideal for RF PCBs used in telecom, aerospace, and defense industries.

• Environments Requiring Enhanced Flame Resistance
  Ensuring compliance with strict flammability criteria is vital for power electronics, industrial controls, and safety-critical systems.

• Precision Electronic Applications
  The dimensional stability and defined tolerances support high-density interconnections and multilayer PCB construction.

• Custom and High-Performance PCBs
  As customization is supported (by agreement between user and supplier), this standard addresses specialized industry needs where specific performance or safety attributes are required.

Related Standards

• IEC 61189-2 Series: These documents detail the test methods for electrical materials, including those used for flammability, resistivity, and mechanical properties.
• IEC 61249-5-1: Specifies requirements for copper foils used in copper-clad laminates.
• ISO 11014: Pertains to the safety data sheets for chemical products, relevant for safe handling and material safety compliance.
• IPC-TM-650: Includes test methods widely referenced in PCB industry for measuring dielectric properties.

Practical Value

Adopting IEC 61249-3-6:2026 helps manufacturers, designers, and end-users to:

• Select high-quality, flame-resistant PTFE laminate materials for PCBs
• Comply with international requirements for electrical and flammability performance
• Facilitate quality control, procurement, and inspection processes
• Achieve safety and reliability in electronic device manufacturing

For more information or to obtain the standard, visit the IEC webstore.