IEC 61249-2-39:2012

Overview

IEC 61249-2-39:2012 is an international standard published by the International Electrotechnical Commission (IEC) that specifies the requirements for reinforced base materials used in printed boards and other interconnecting structures. This part of the IEC 61249 series focuses on high-performance woven E-glass laminate sheets, both epoxide and non-epoxide types, with defined flammability characteristics based on the vertical burning test. The sheets are copper-clad and designed specifically for lead-free assembly processes.

Key features of these base materials include:

• Thickness range from 0.05 mm to 3.2 mm
• Modified brominated epoxide resin systems
• Copper cladding suitable for lead-free soldering
• Minimum glass transition temperature (Tg) of 170 °C
• Defined flammability levels according to vertical burning tests

This standard is essential for manufacturers and designers of printed circuit boards (PCBs) aiming to ensure quality, safety, and performance consistency in environments where fire resistance and compatibility with lead-free assembly are critical.

Key Topics

IEC 61249-2-39:2012 covers a comprehensive range of specifications relevant to reinforced fiberglass laminate sheets used in electronics, including:

• Material Composition and Construction: Details on resin systems (modified brominated epoxide and non-epoxide), E-glass reinforcement, and copper foil application to create high-quality laminate sheets.
• Physical and Mechanical Properties: Specifications for laminate thickness, bow and twist tolerances, flexural strength, punching/machining capabilities, and dimensional stability essential for reliable PCB fabrication.
• Electrical Characteristics: Standard values for electrical properties vital for optimum signal integrity in PCB applications.
• Flammability and Safety: Defined flammability requirements via vertical burning tests to ensure materials meet fire safety standards suitable for electronic assemblies.
• Thermal Performance: Criteria for glass transition temperature, decomposition temperature, thermal resistance, and Z-axis expansion, supporting durability in high-temperature lead-free soldering processes.
• Quality Assurance: Guidance on qualification inspections, ongoing conformance testing, certificates of conformance, and safety data sheet requirements to maintain consistent production standards.
• Packaging and Marking: Standards for proper labeling and packaging for traceability and handling during distribution and fabrication.

Applications

IEC 61249-2-39:2012 materials are specifically designed for use in the manufacture of:

• Printed Circuit Boards (PCBs): Especially suited for high-performance and lead-free assembly PCBs, commonly used in sectors such as telecommunications, automotive electronics, industrial controls, and consumer electronics.
• Interconnecting Structures: Laminates for backplanes, connectors, and other interconnect products requiring stability and fire resistance.
• High-Temperature Environments: Electronics that operate under harsh thermal conditions benefit from the minimum Tg of 170 °C and robust thermal resistance features.
• Flame-Retardant Electronic Assemblies: Ensures compliance with safety standards wherever controlled combustibility is mandated.

Using IEC 61249-2-39 compliant laminates helps manufacturers meet stringent environmental and safety regulations while enhancing the reliability and longevity of electronic products.

Related Standards

To complement IEC 61249-2-39:2012, the following related IEC standards and publications are relevant for professionals working with printed board materials and assembly processes:

• IEC 61249 Series: A broad set of standards covering various types of laminated base materials and prepregs for electronic applications.
• IEC 60695 Series: Fire hazard testing for electrical and electronic products, providing additional guidelines on flammability.
• IPC Standards: Industry standards such as IPC-4101 provide specifications for base materials used in PCBs, often used in conjunction with IEC standards.
• IEC 60068 Series: Environmental testing standards that can complement material performance verification.
• ISO/IEC Directives Part 2: Guidelines on the preparation and structure of international standards relevant to compliance and conformance.

Compliance with IEC 61249-2-39 is vital for designers and manufacturers aiming to produce high-quality, reliable, and safe printed boards meeting modern technological and environmental requirements.

Keywords: IEC 61249-2-39, reinforced base materials, printed circuit board materials, woven E-glass laminates, copper-clad laminates, lead-free assembly, high-performance epoxide laminate, flammability, vertical burning test, glass transition temperature, PCB standards, electronic interconnecting structures.