IEC 61249-4-14:2009

Overview

IEC 61249-4-14:2009 is an IEC sectional specification for epoxide woven E‑glass prepreg used as unclad bonding sheets in the manufacture of multilayer printed circuit boards (PCBs). The standard defines material, construction and performance requirements for B‑stage prepreg that is suitable for lead‑free assembly processes and has defined flammability assessed by the vertical burning test. Key material features include a di‑ and multi‑functional epoxide resin system (brominated into the polymer) and a cured glass transition temperature (Tg) of ≥ 120 °C when cured per supplier instructions.

Key Topics

• Material construction
  • Woven E‑glass reinforcement impregnated with epoxide resin and partially cured to B‑stage.
  • Brominated flame retardants chemically integrated into the polymeric structure.
• Flammability
  • Defined by the vertical burning test (see the standard’s flammability table).
• Thermal and mechanical properties
  • Minimum Tg = 120 °C after cure.
  • Requirements include decomposition temperature, thermal resistance and Z‑axis expansion.
• Electrical and dielectric properties
  • Electric strength, relative permittivity and dissipation factor specified for cured prepreg.
• B‑stage characteristics and processability
  • Typical parameters for ordering and qualification: resin content, treated weight, resin flow, scaled flow thickness, melt viscosity, cured thickness; optional: volatile content and gel time.
• Appearance and defects
  • Limits on defects such as dewetted areas (“fish eyes”), broken filaments, creases and edge resin loss (e.g., no dewetted areas >10 mm; ≤10 fish eyes per 300×300 mm allowed).
• Quality & logistics
  • Delivery forms (rolls, sheets, cut panels), quality assurance, certificates of conformance, safety data sheets, packaging and shelf life information.

Applications

• Used by PCB manufacturers and laminate suppliers to produce rigid multilayer boards for electronics requiring lead‑free assembly (e.g., consumer electronics, telecommunications, automotive electronics).
• Employed as bonding sheets to join copper‑clad or other laminates (compatible with laminates per IEC 61249‑2‑36 and multilayer manufacturing per IEC 62326‑4).
• Relevant to materials engineers, procurement/specification teams, process engineers and test laboratories focused on prepreg materials, flame performance, and high‑temperature assembly reliability.

Related Standards

• IEC 61189‑2 - test methods for materials and interconnection structures
• IEC 61249‑2‑36 - epoxide E‑glass copper‑clad laminates for lead‑free assembly
• IEC 62326‑4 - rigid multilayer printed boards (sectional specification)
• ISO 11014‑1 - safety data sheet content

Keywords: IEC 61249-4-14, prepreg materials, epoxide woven E‑glass, lead‑free assembly, vertical burning test, glass transition temperature, brominated flame retardants, multilayer boards.