Directly heated negative temperature coefficient thermistors - Part 2: Sectional specification - Surface mount negative temperature coefficient thermistors (IEC 60539-2:2019); German version EN IEC 60539-2:2019 / Note: DIN EN 60539-2 (2011-04) remains ...
1Key Takeaways
This part of IEC 60539 applies to directly heated, surface-mount resistors with a negative temperature coefficient, typically made from transition metal oxide materials with semiconducting properties. These thermistors have metallized pads or solder strips and are intended for direct mounting on substrates of hybrid ci…
2Expert Interpretation
A comprehensive interpretation of the DIN EN IEC 60539-2:2020 standard for surface mount negative temperature coefficient thermistors, covering technical specifications, test methods, quality assessment systems, and implementation requirements, providing professional guidance for electronic component manufacturers and users.
Standard Overview and Technical Background
DIN EN IEC 60539-2:2020 is a professional standard for surface mount negative temperature coefficient thermistors (NTC) published by the German Institute for Standardization. This standard officially came into effect in December 2020, replacing the previous version, DIN EN 60539-2:2011-04. This standard applies to directly heated surface mount NTC thermistors, which are typically made of transition metal oxide materials with semiconductor properties.
Main technical changes and updates
Compared with the 2011 version, the 2020 version of the standard has undergone important technical updates:
| Change items | 2011 version | 2020 version | Technical significance |
|---|---|---|---|
| Standard structure | Based on the old version of the directive | Compliant with ISO/IEC Directives, Part 2:2016 | Improved international coordination |
| Temperature category | Up to 155°C | Newly added 175°C, 200°C, 250°C, 315°C, and 400°C | Expanded high temperature application range |
| Dimensions | Not including 0402M | Newly added 0402M size | Adapting to the trend of miniaturization |
| Harmonization | Partially harmonized | Fully harmonized with IEC 60539-1:2016 | Improved standard consistency |
Detailed explanation of key technical requirements
4.1 Dimensions and mechanical properties
Appendix A of the standard specifies in detail the size coding system for surface mount NTC thermistors, where the W dimension should not exceed the L1 dimension, and the H dimension should not exceed the W dimension. Typical dimensions include:
| Code | Length L1(mm) | Width W(mm) | L2(mm) | L3(mm) | L4 Min. Value(mm) |
|---|---|---|---|---|---|
| 0402M | 0.4±0.05 | 0.2±0.05 | 0.05 | 0.10 | - |
| 0603M | 0.6±0.05 | 0.3±0.05 | 0.1 | 0.15 | - |
| 3216M | 3.2±0.2 | 1.6±0.2 | 0.3 | 1.4 | - |
4.2 Zero-burden resistor tolerance
The standard specifies the preferred zero-burden resistor tolerance values: ±0.5%, ±1%, ±2%, ±3%, ±5%, and ±10%. These tolerance grades provide options for applications with different accuracy requirements.
Climate category and environmental adaptability
| Parameter type | Optional value | Test requirements |
|---|---|---|
| Lower category temperature | -55°C, -40°C, -25°C, -10°C, -5°C, +5°C | Compliant with IEC 60068-2-1 |
| Upper category temperature | 70°C, 85°C, 100°C, 105°C, 125°C, 150°C, 155°C, 175°C, 200°C, 250°C, 315°C, 400°C | Complies with IEC 60068-2-2 |
| Duration of constant damp heat | 21 days, 42 days, 56 days | Complies with IEC 60068-2-78 |
Test methods and quality requirements
7.3 Visual inspection and dimensional inspection
The standard requires visual inspection with a 10x magnifying glass, and has strict quality requirements for both the ceramic body and the metallization layer:
- Insulated devices: The length of glass encapsulation cracks shall not exceed 25% of the L4 dimension, and the area of glass encapsulation blistering on any surface shall not exceed 10% of the total area of that surface.
- Non-insulated devices: Interlayer separation or delamination is not allowed, and no exposure between electrodes is allowed.
- Metallization requirements: The maximum area of metallization defects on each major surface shall not exceed 15% of the surface area, and they shall not be concentrated in the same area.
7.6 Soldering heat resistance test
Tested in accordance with IEC 60068-2-58:2015, the zero-load resistance change after soldering shall not exceed ±5%, and the end face metallization peeling (leaching) shall not exceed 25% of the relevant edge length.
Quality Assessment System
Appendix B specifies the quality assessment procedures in detail, including:
| Assessment type | Sampling requirements | Acceptance criteria | Test cycle |
|---|---|---|---|
| Batch inspection (Group A, B) | Sampling according to IEC 61193-2 | 0 defect acceptance | Each batch |
| Periodic inspection (Group C) | Representative sampling | As per plan requirements | 3-6 months |
| Type approval | Full Range Sampling | EZ Grade | One-time Certification |
Implementation Recommendations and Industry Impact
Impact on Manufacturers
The implementation of the new standard requires manufacturers to:
- Update production processes to adapt to higher temperature category requirements
- Strengthen quality control systems, especially the detection capabilities of miniaturized components (such as 0402M)
- Re-evaluate material systems to meet the requirements of the extended temperature range
Selection Guidance for Users
When selecting surface mount NTC thermistors, users should:
- Clearly define the temperature range requirements of the application environment and select the appropriate temperature category
- Select the appropriate resistance tolerance grade based on the accuracy requirements
- Consider the impact of soldering process on component reliability
- Give priority to products that meet the latest standard requirements
Technological Development Trends
The development trends of NTC thermistor technology can be seen from the updated content of the standard:
| Technical Direction | Standard Reflection | Development Trend |
|---|---|---|
| High Temperature Applications | New 400°C Temperature Category | Expanding to Higher Temperature Fields |
| Miniaturization | Adding 0402M Size Specifications | Adapting to the Miniaturization Demand of Electronic Products |
| Improved Reliability | Strengthening Test Requirements | Increasing Product Service Life |
Transition Arrangements and Compliance Requirements
According to the standard, the transition period for DIN EN 60539-2:2011-04 is until August 23, 2022. Manufacturers and users should complete the transition to the new standard during this period. The following steps are recommended:
- Assess the compliance gap between existing products and the new standard
- Develop a product upgrade and technical transformation plan
- Update quality control documents and test procedures
- Conduct personnel training and technical exchanges
- Complete product recertification and standard version change
Fully implementing the new standard requirements will not only improve product quality and reliability, but also enhance product competitiveness in the international market, providing technical support for the healthy development of the electronic components industry.