Overview
IEC 61189-2-809:2024 specifies a standardized test method for determining the X/Y coefficient of thermal expansion (CTE) in thick electrical insulating base materials using thermomechanical analysis (TMA). Published by the International Electrotechnical Commission (IEC), this standard addresses quality and reliability needs in the electronics and printed circuit board (PCB) industries. Its methodology ensures precise, repeatable measurements of how insulating materials expand or contract across temperature changes, which is critical for designing durable circuit boards and interconnection structures.
Key Topics
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Scope and Purpose
IEC 61189-2-809:2024 defines procedures for assessing the X/Y CTE of solid, rigid electrical insulating materials over specified temperature ranges using a TMA. Only materials maintaining their solid, hard, and rigid nature throughout the temperature range are suitable for testing.
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Test Specimens
- Specimens are typically 0.5 mm to 7.5 mm thick, and between 5 mm to 12 mm long and 5 mm to 10 mm wide.
- Samples must be prepared in both the X (weft/fill) and Y (warp/machine) directions to account for any anisotropic properties inherent to composite materials like fiberglass laminates.
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Apparatus
- Thermomechanical analyzer (TMA) capable of detecting small dimensional changes (0.001 mm).
- Circulating air oven for preconditioning and drying test specimens.
- Desiccator or low-humidity drying cabinet to ensure specimen stability before testing.
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Test Procedure
- Clean, dry, and prepare specimens as per defined dimensions.
- Calibrate TMA according to manufacturer instructions.
- Apply controlled load on the specimen and conduct the temperature ramp (commonly from 30 °C to 260 °C).
- Record dimensional changes for both X and Y directions.
- Calculate CTE based on changes in specimen length/width over the temperature interval using standard formulas.
- Report results, including test method, material identification, environmental conditions, test data, and any deviations.
Applications
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Printed Circuit Board Manufacturing
Accurate measurement of the CTE in both X and Y axes is essential for predicting dimensional stability and compatibility during multilayer PCB fabrication, assembly, and operation.
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Material Selection and Quality Control
The standard supports engineers in verifying that insulating materials exhibit stable thermal behavior, thus reducing failures due to thermal stress, delamination, or warping.
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Product Reliability in Electronics
By establishing reliable material properties, IEC 61189-2-809 helps ensure that electronic assemblies can withstand thermal cycling experienced in service, improving lifespan and performance.
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Supplier Qualification and Incoming Inspection
Consistent CTE testing is a foundational step in qualifying new materials or suppliers and in maintaining high-quality standards in electronic manufacturing.
Related Standards
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IEC 61189 Series
The parent series covers methods for testing electrical materials and assemblies, contributing to comprehensive quality assurance in electronics.
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IEC 60194-1 & IEC 60194-2
Vocabulary standards that provide essential terminology for printed board and electronic assembly technologies.
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ASTM E831
U.S. standard for linear thermal expansion via thermomechanical analysis, referenced for similar methodologies.
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IPC-TM-650 Method 2.4.41
Industry-recognized test method for determining the coefficient of linear thermal expansion in electrical insulating materials.
IEC 61189-2-809:2024 offers a reliable framework for measuring and assuring the thermal expansion properties of thick base materials in electronics manufacturing, playing a vital role in ensuring consistent product performance and reliability across global supply chains.
Open preview (PDF)Test methods for electrical materials, circuit boards and other interconnection structures and assemblies – Part 2-809: X/Y coefficient of thermal expansion (CTE) test for thick base materials by TMA
