Overview
IEC TR 61760-5-1:2024, published by the International Electrotechnical Commission (IEC), focuses on the measurement of surface strain on circuit boards using electrical strain gauges. This technical report provides practical examples of methodologies to identify mechanical stresses during electronic assembly processes, particularly those that can lead to “bending cracks” in chip-type ceramic components. The use of strain gauges is essential for ensuring high reliability in surface mounting technology, as stress-induced damage can compromise both the performance and longevity of electronic circuits. Area-array components are explicitly excluded from this standard’s scope.
Key Topics
- Damage Mechanisms:
- Explains how surface strain due to board bending can produce critical mechanical stress in chip-type ceramic components.
- Illustrates common cracking modes such as longitudinal and diagonal cracks and their relationship to mechanical loading.
- Strain Gauge Measurement Techniques:
- Covers the use of 1-axis, 2-axis, and especially 3-axes electrical strain gauges for quantifying local strain states during assembly.
- Addresses the theory and practicalities of implementing strain measurement using Wheatstone bridge circuits.
- Crack Prevention Strategies:
- Details essential measures for strain control on printed circuit boards (PCBs), including the importance of substrate bending tests and safety margins.
- Critical Design and Process Considerations:
- Identifies design factors (e.g., component placement relative to cutting or screw positions, orientation, board warpage) that influence mechanical strain.
- Describes various stages in the assembly process where stress can occur, such as circuit board singulation, housing assembly, screwing, and manual handling.
- Best Practices for Strain Measurement:
- Provides guidance on sample preparation, strain gauge positioning, and attachment techniques.
- Highlights common mistakes, such as poor gauge attachment, use of the wrong type of strain gauge, and conducting measurements on unpopulated PCBs.
Applications
IEC TR 61760-5-1:2024 is highly relevant for:
- Electronics Manufacturers: To assess and mitigate risks related to mechanical strain during the assembly of surface mounted devices (SMDs).
- Quality Assurance Engineers: To implement standardized testing and monitoring procedures that prevent mechanical damage to ceramic chip components.
- Research and Design Teams: To validate both board layouts and manufacturing practices, especially when working with increasingly thin and compact PCBs.
- Failure Analysis: Offers methodologies for investigating the root cause of cracks and defects, facilitating better communication between suppliers and customers regarding critical stress points during assembly.
Typical industry applications include automotive electronics, consumer devices, industrial control units, and any sector where SMDs are used and mechanical reliability is crucial.
Related Standards
- IEC 60194-2: Refers to related terminology essential for understanding and using this technical report effectively.
- IEC 60068-2-21: Describes substrate bending tests, a referenced method for determining component bending strength.
- Additional guidance can be found in the bibliography and other parts of the IEC 61760 series on surface mounting technology.
Practical Value
By following the guidance offered in IEC TR 61760-5-1:2024, organizations can proactively address risks associated with mechanical strain on chip components. The use of strain gauge measurement as described helps pinpoint critical areas for design improvement, process refinement, and ongoing quality control. Integrating these practices supports product reliability, lowers the risk of failure, and streamlines communication in supply chains for electronics manufacturing.
For the most accurate and up-to-date information, always consult the official IEC publication and related standards.