IEC 61249-4-2:2005

Overview

IEC 61249-4-2:2005 defines requirements for multifunctional epoxide woven E-glass prepreg of defined flammability used mainly as bonding sheets in multilayer printed circuit board (PCB) manufacture. The standard covers material construction (woven E-glass impregnated with multifunctional epoxide resin, partially cured to B-stage), flammability control (vertical burning test), and key performance requirements such as a glass transition temperature (Tg) ≥ 150 °C after proper cure. Flame retardancy is achieved by brominated fire retardants incorporated into the polymer matrix.

Key Topics and Requirements

• Material construction: Woven E-glass reinforcement (per IEC 61249-6-3) impregnated with a multifunctional epoxide resin system; B-stage prepreg condition.
• Flammability: Defined flammability rating on fully cured prepreg-verified by a vertical burning test (test method referenced in IEC 61189-2).
• Thermal performance: Minimum cured Tg of 150 °C (per supplier curing instructions).
• Electrical properties: Minimum electric strength of 25 V/µm (measured on cured plies).
• B-stage controls: Key B-stage parameters include resin content, treated weight, resin flow, scaled flow thickness, melt viscosity, gel time and volatile content (≤ 0.5%).
• Dimensional and visual quality: Limits on defects (e.g., dewetted areas, broken filaments, distortion, creases, edge resin loss).
• Delivery and QA: Specified delivery forms (rolls, sheets, cut panels), quality assurance, certification of conformance and safety data sheets, packaging and shelf life requirements.

Applications

• Bonding sheets for multilayer PCBs manufactured to IEC 62326-4 and base laminates per IEC 61249-2-8.
• Bonding other laminate types where controlled flame retardancy and high Tg are required.
• Typical users: PCB fabricators, laminate suppliers, electronic manufacturing services (EMS), material engineers and procurement teams specifying prepreg for high-reliability electronic assemblies.

Who Should Use This Standard

• Design and process engineers specifying bonding materials for multilayer boards.
• Quality, compliance and procurement professionals selecting prepreg with controlled flammability and thermal performance.
• Suppliers and manufacturers of prepreg and copper-clad laminates to ensure material conformance and interoperability.

Related Standards

• IEC 61189-2 (test methods for materials)
• IEC 61249-2-8 (reinforced base materials, modified brominated epoxide laminate)
• IEC 61249-6-3 (woven E-glass reinforcement)
• IEC 62326-4 (rigid multilayer printed boards)
• ISO 9000, ISO 11014-1, ISO 14001 (quality, SDS and environmental management)

Keywords: IEC 61249-4-2:2005, prepreg, multifunctional epoxide, woven E-glass, Tg 150°C, flammability, brominated fire retardant, B-stage prepreg, multilayer PCB bonding.