IEC 61249-2-53:2025

Overview

IEC 61249-2-53:2025 defines requirements for PTFE unfilled reinforced laminate sheets, copper-clad, intended for printed boards and other interconnecting structures. The standard covers copper-clad and unclad reinforced PTFE laminates with thicknesses from 0.05 mm to 10.0 mm and specifies defined flammability (vertical burning test) criteria (see clause 8.4). It is part of the IEC 61249 series addressing base materials for PCB substrates and was prepared by IEC TC 91 (Electronics assembly technology).

Key topics and requirements

The standard organizes technical requirements across material, electrical, mechanical and quality domains, including:

• Construction and materials: resin system, metal foil, reinforcement and layer construction for copper-clad PTFE unfilled laminate sheets.
• Electrical properties: dielectric and insulation characteristics specified in tabular form (see Table 1).
• Non‑electrical properties (copper-clad face): appearance (pits, dents, wrinkles, scratches, waviness), thickness tolerances, bow and twist, peel strength, heat shock and machining behaviour.
• Base material properties (after foil removal): flexural strength, water absorption, glass transition / cure factor, decomposition temperature, flammability (vertical burning), time-to-delamination (TMA), and thermal expansion (Z-axis and X/Y-axis).
• Dimensional controls: sheet and cut-panel sizes, tolerances and rectangularity.
• Quality assurance: qualification and conformance inspection regimes, sampling, inspection lots, certificates of conformance and required safety data sheets.
• Packaging, marking and ordering information: to support traceability and procurement.

Practical applications and who uses it

IEC 61249-2-53 is used by professionals who specify, produce, test or procure PTFE-based PCB materials:

• PCB designers and engineers who select substrate materials for signal integrity, thermal and mechanical performance while meeting flammability targets.
• Materials and laminate manufacturers for product design, quality control and documentation of copper-clad PTFE unfilled laminates.
• Test laboratories and QA teams performing qualification, conformance testing and issuing certificates of conformance.
• Purchasing and compliance personnel requiring defined specifications for procurement, safety data sheets and regulatory compliance.
• Typical applications include printed circuit boards and interconnecting structures where low-loss PTFE-based laminates and controlled flammability are required.

Related standards

• Other parts of the IEC 61249 series covering reinforced base materials for printed boards.
• Reference to normative documents listed in clause 2 and the broader IEC material and testing standards referenced within the standard (see normative references).

Keywords: IEC 61249-2-53, PTFE unfilled laminate, copper-clad, printed boards, vertical burning test, flammability, reinforced base materials, PCB materials, laminate specification.