IEC 61189-2-805:2024

Overview

IEC 61189-2-805:2024 is an International Electrotechnical Commission (IEC) standard that specifies the test method for determining the X/Y coefficient of thermal expansion (CTE) of thin electrical insulating materials. The measurement is performed using a thermomechanical analyzer (TMA). This method is primarily applicable to solid insulating base materials used in printed circuit boards and other electrical interconnection structures that remain sufficiently rigid over the test temperature range to prevent permanent indentation by the measuring probe.

This standardized approach provides essential data on material dimensional stability, which is critical for the performance and reliability of modern electronics.

Key Topics

• Coefficient of Thermal Expansion (CTE): IEC 61189-2-805 focuses on the X and Y directional thermal expansion characteristics of thin insulating materials, helping manufacturers understand how materials will behave under thermal stress.
• Thin Base Materials: Applicable to samples with thicknesses between 0.01 mm and 0.5 mm, commonly found in advanced electronic assemblies.
• TMA Measurement: Employs a thermomechanical analyzer to record dimensional changes as a function of temperature, with the method requiring careful specimen preparation and pre-conditioning.
• Test Reproducibility: Guidelines on sample conditioning, test environment, and apparatus calibration are included to ensure reliable and repeatable results.
• Reporting Requirements: Detailed documentation of specimen characteristics, test conditions, and calculated CTE values is mandated.

Applications

The standardized test method described in IEC 61189-2-805 is vital in several areas:

• Printed Circuit Board (PCB) Manufacturing: Accurate knowledge of the CTE in the X and Y directions helps PCB designers and fabricators optimize materials for dimensional stability, reducing failure risk from expansion or contraction during temperature changes.
• Material Qualification: Suppliers and end users of electrical insulating materials use the standard to certify material consistency and suitability for specific electronic applications, especially where thin substrates are required.
• Quality Assurance: Provides a consistent framework for assessing and comparing thermal expansion among different material lots, ensuring uniformity across production batches.
• Electronic Assembly Reliability: Minimizing CTE mismatch between different materials in assemblies helps prevent stress-induced defects, such as warping, delamination, or cracking, during thermal cycling or soldering processes.

Related Standards

For a comprehensive approach to insulation material and PCB testing, consider the following related standards:

• IEC 60194-1: Vocabulary for design, manufacture, and assembly of printed boards and electronic assemblies.
• IPC-TM-650, Test Method 2.4.24.5: Test method for measuring glass transition temperature and thermal expansion using TMA, commonly referenced for high density interconnect (HDI) materials.
• Other parts in the IEC 61189 series: Cover additional test methods for electrical materials, printed boards, and interconnection assemblies.

These standards, when used alongside IEC 61189-2-805, support robust quality assurance and facilitate international comparability in the electronics industry.

Utilizing IEC 61189-2-805:2024 ensures that manufacturers, material suppliers, and assembly houses can effectively assess and validate the thermal expansion performance of thin insulating materials, thereby supporting the reliability and longevity of modern electronic devices. For those seeking current and authoritative guidance on X/Y CTE testing in electronics, this standard is an essential resource.