IEC 61249-2-52:2025

Overview

IEC 61249-2-52:2025 specifies requirements for thermosetting hydrocarbon resin system, woven E‑glass reinforced laminate sheets with defined flammability (vertical burning test), copper‑clad and supplied unclad, in thicknesses from 0.05 mm to 3.20 mm. Part of the IEC 61249 series for materials used in printed boards and other interconnecting structures, this standard defines material composition, performance tests, inspection and documentation needed to ensure reliable printed circuit board (PCB) base materials.

Key topics and requirements

The standard covers both material construction and measurable performance characteristics, including:

• Materials and construction: resin system, metal foil (copper‑clad), and woven E‑glass reinforcement.
• Electrical properties: standardized test methods and tabulated electrical performance expectations for PCB base materials.
• Non‑electrical properties: appearance, laminate thickness tolerances, bow & twist, peel strength (copper bond), thermal stress, solderability, punching and machining suitability, and dimensional stability.
• Mechanical and thermal properties: flexural strength, glass transition temperature (Tg) and cure factor, decomposition temperature, time to delamination (TMA), Z‑axis and X/Y‑axis expansion, and thermal conductivity.
• Flammability: defined criteria based on the vertical burning test to classify material behavior under fire conditions.
• Durability tests: water absorption, measling (visual defects), surface finish criteria and thermal aging behaviors.
• Quality assurance and inspection: qualification inspection, conformance inspection plans, sampling, judgment rules, certificate of conformance, and safety data sheet (SDS) requirements.
• Logistics and traceability: internal marking, packaging, marking, sheet/cut panel sizes and ordering information.

Applications and who uses it

IEC 61249-2-52:2025 is directly applicable to stakeholders in the electronics supply chain:

• PCB laminate and copper‑clad manufacturers - to define product specifications and quality control.
• PCB fabricators and assemblers - to select materials that meet solderability, dimensional and thermal requirements.
• OEMs in consumer electronics, automotive, aerospace and industrial sectors - to ensure material safety (flammability) and reliability.
• Procurement, quality and compliance engineers - for supplier qualification, incoming inspection and regulatory documentation.
• R&D and materials engineers - to compare laminate formulations and to design PCBs for thermal/mechanical performance.

Related standards

• IEC 61189‑2 (test methods for electrical materials and printed boards) - normative test references.
• IEC 61249‑5‑1 (sectional specification set for conductive materials) - related materials guidance.
• Other parts of the IEC 61249 series for broader materials and construction requirements.

Keywords: IEC 61249-2-52:2025, copper-clad laminate, thermosetting hydrocarbon resin, woven E-glass, vertical burning test, PCB base material, flammability, Tg, Z-axis expansion, solderability.