IEC 61249-4-16:2009

Overview

IEC 61249-4-16:2009 specifies requirements for unclad prepreg materials used as bonding sheets in the manufacture of rigid multilayer printed boards (PCBs), specifically targeting materials suitable for lead-free assembly. The standard covers a multifunctional non‑halogenated epoxide resin system impregnated into woven E‑glass reinforcement, with defined flammability performance assessed by the vertical burning test. After supplier-recommended cure, the prepreg’s glass transition temperature (Tg) is specified at 150 °C and 200 °C (as applicable per product class).

Key topics and technical requirements

• Material construction
  • Woven E‑glass reinforcement impregnated with modified non‑halogenated epoxide resin (B‑stage prepreg).
  • Resin system limits: maximum total halogens 1500 ppm; max chlorine 900 ppm, max bromine 900 ppm.
  • Curing agent restriction: dicyandiamide is not permitted.
• Flammability
  • Defined flammability rating based on the vertical burning test; flame retardancy achieved as an integral part of the polymeric structure.
• B‑stage (uncured) properties
  • Typical characteristics used for qualification: resin content, treated weight, resin flow, scaled flow thickness, melting viscosity, gel time, volatile content.
• Post‑cure properties
  • Electrical strength, relative permittivity and dissipation factor, cured thickness, Tg, decomposition temperature, thermal resistance, Z‑axis expansion.
• Appearance and workmanship limits
  • Defect tolerances (examples): no dewetted areas >10 mm; up to 10 fish‑eye defects ≤10 mm per 300×300 mm; distortion of weave yarns ≤10% over 300 mm; edge resin loss due to cutting ≤2 mm.
• Supply, QA and logistics
  • Delivery forms: rolls, sheets, cut panels. Requirements include qualification inspection, quality conformance inspection, certificate of conformance, safety data sheet and shelf‑life/packaging provisions.

Applications and who uses the standard

IEC 61249-4-16 is intended for:

• PCB laminate and prepreg manufacturers qualifying materials for multilayer boards.
• PCB fabricators and EMS providers selecting bonding sheets for lead‑free assembly processes.
• OEMs, design engineers and procurement teams specifying material performance for high‑reliability multilayer PCBs.
• Quality, compliance and R&D engineers verifying flammability, thermal and electrical properties for product certification and process compatibility.

Practical benefits include consistent material selection for lead‑free assembly, reliable flammability performance, and standardized acceptance criteria for multilayer PCB production.

Related standards

• IEC 61249-2-37 (reinforced base materials/clad laminates for lead‑free assembly)
• IEC 62326-4 (rigid multilayer printed boards - sectional specification)
• IEC 61189-2 (test methods for electrical materials and printed boards)
• ISO 11014-1 (safety data sheet content)