In electronic circuit design, a resistor may seem simple but plays a vital role. It is used for voltage division, current limiting, biasing, signal conditioning, and circuit protection. However, after long-term operation or under specific electrical stress, a resistor may experience a subtle yet performance-impacting phenomenon known as resistor body degradation. Many distributors offer a wide range of electronic components to cater to diverse application needs, like BAV70
Definition and Characteristics of Resistor Body Degradation
Resistor body degradation refers to a fault condition caused by instantaneous overloads, excessive electrostatic discharge (ESD), or strong surge pulses, which lead to internal material changes and result in a drop in resistance value.
This issue is common in thick film resistors, as their internal structure contains glass components that are prone to breakdown and difficult to recover.
In actual failure cases, resistor degradation often shows the following characteristics:
The resistance value decreases by approximately 5% to 30%.
The resistor still shows measurable resistance but cannot return to its nominal value.
The resistive film appears visually normal even after removing the protective coating.
This “no visible damage but degraded performance” condition poses significant challenges for quality analysis and may easily be mistaken for material or soldering issues during customer feedback.
Mechanism of Resistor Body Degradation
The main conductive layer of a resistor is made of resistor paste, which is a composite of conductive materials (such as ruthenium oxide) and glass glaze.
Under normal operating conditions, the glass component helps distribute current evenly and maintains resistance stability.
However, when subjected to transient high voltage or ESD, the internal glass matrix can undergo latent dielectric breakdown, reducing its resistivity and altering current paths.
Since current naturally flows through the path of least resistance, this breakdown creates localized conduction areas. As a result, the overall resistance value decreases and cannot recover to its original state.
Prevention and Mitigation Measures
To reduce the risk of resistor degradation, several design and component-level strategies can be implemented:
Optimize circuit design
Improve layout and minimize overloads and surge generation.
Use surge-resistant or high-voltage resistors
These resistors use specially formulated pastes with higher dielectric strength to maintain stability under voltage stress.
Upgrade resistor ratings
For high-voltage applications, choose models rated for greater working voltage. For example, resistors in the 2512 package can withstand up to 3000V.
Enhance ESD protection
In sensitive circuits, add components such as TVS diodes or varistors to absorb transient energy and reduce stress on resistors.
Conclusion
Resistor body degradation is a typical hidden failure mode in thick film resistors under high stress. The main risk lies in its invisible nature, which can cause circuit drift, signal distortion, or even equipment malfunction while appearing normal externally.
Therefore, understanding the mechanism of resistor degradation and applying targeted preventive measures during circuit design and component selection is essential for ensuring long-term system reliability.
By choosing high-voltage, surge-resistant resistor products and incorporating proper ESD and surge suppression designs, engineers can significantly improve the reliability and service life of electronic devices.