IEC 61249-2-31:2009

Overview

IEC 61249-2-31:2009 is an international standard published by the International Electrotechnical Commission (IEC) that defines the specifications for reinforced base materials used in printed boards and other interconnecting structures. This standard focuses on halogenated modified or unmodified resin systems combined with woven E-glass laminate sheets. These base materials are copper-clad and engineered for specific electrical and physical properties, ensuring high reliability and performance in electronic applications.

The standard applies to laminate sheets with thicknesses ranging from 0.05 mm up to 3.2 mm, requiring a minimum glass transition temperature of 150 °C. It strictly specifies key electrical characteristics such as a relative permittivity equal to or less than 4.1 at 1 GHz and a dissipation factor not exceeding 0.0120 at the same frequency. These parameters ensure the controlled dielectric behavior essential for high-frequency electronic circuits.

Key Topics

• Material Composition

  • Halogenated, modified or unmodified epoxide resin system
  • Woven E-glass fabric reinforcement for mechanical strength
  • Copper cladding on one or both sides for conductive circuit formation

• Electrical Properties

  • Relative permittivity ≤ 4.1 at 1 GHz, suitable for RF and high-speed digital applications
  • Dissipation factor ≤ 0.0120 at 1 GHz for minimal signal loss
  • Defined glass transition temperature (Tg) ≥ 150 °C for thermal stability

• Physical and Mechanical Characteristics

  • Thickness tolerance from 0.05 mm to 3.2 mm, meeting dimensional stability requirements
  • Surface quality criteria including absence of indentations, wrinkles, scratches, and surface waviness
  • Bow and twist limits to ensure flatness critical for multilayer PCB fabrication
  • Copper foil bond strength, punching, machining, and water absorption standards

• Flammability and Safety Testing

  • Vertical burning test to classify flame resistance of the laminate materials
  • Halogenated resins to comply with specific fire retardancy requirements

• Quality Assurance and Compliance

  • Procedures for qualification, conformance inspection, and certification of materials
  • Clear marking and labeling for traceability and identification

Applications

IEC 61249-2-31 compliant materials are widely used in the manufacturing of:

• High-frequency and microwave printed circuit boards requiring controlled dielectric properties
• Rigid and multilayer PCB substrates for telecommunications, aerospace, and automotive electronics
• Interconnecting structures in devices where thermal stability and flame retardancy are critical
• Electronic assemblies that demand consistent performance under mechanical and environmental stress

By adhering to this standard, manufacturers ensure that the base materials possess the reliability and performance needed for complex electronics, helping to reduce the risk of failure and improve end-product longevity.

Related Standards

IEC 61249-2-31:2009 is part of the broader IEC 61249 series which covers:

• Other reinforced base materials, clad and unclad, with different resin systems and fabric reinforcements
• Specifications addressing materials for flexible printed boards and interconnects
• Testing methods and quality control measures for laminated materials

Additional relevant standards include:

• IEC 60335 series on safety requirements for electrical appliances and materials
• IEC 61189 series defining test methods for electronic components
• ISO/IEC Directives that govern the development and maintenance of international standards

For professionals involved in PCB design, materials procurement, and electronics manufacturing, familiarity with IEC 61249-2-31:2009 and related standards is vital to ensure compliance, optimal material selection, and enhanced product performance.

Keywords: IEC 61249-2-31, reinforced base materials, copper-clad laminate, woven E-glass, halogenated resin, printed circuit boards, relative permittivity, dissipation factor, flammability, glass transition temperature, PCB materials standard, electronic interconnecting structures, vertical burning test.