Failure mode refers to various failure phenomena and their observable characteristics. Failure mechanism, on the other hand, refers to the physical, chemical, thermodynamic, or other processes that lead to failure.
1. **Main failure modes and mechanisms of resistors**
- **Open Circuit**: The primary cause is the burning out or peeling of the resistive film, breakage of the matrix, or detachment between the lead cap and resistor body.
- **Resistance Drift Beyond Standard**: This occurs when the resistive film is defective or degraded, or when there are mobile sodium ions in the substrate, along with poor protective coating.
- **Lead Breakage**: Often due to defects in the resistance welding process, contamination at the solder joint, or mechanical stress on the lead.
- **Short Circuit**: Caused by silver migration or corona discharge.
2. **Proportion of failure modes among total failures**
- **Wirewound Resistors**
| Failure Mode | Proportion of Total Failures |
|-------------------|------------------------------|
| Open Circuit | 90% |
| Resistance Drift | 2% |
| Lead Break | 7% |
| Other | 1% |
- **Non-Wirewound Resistors**
| Failure Mode | Proportion of Total Failures |
|-------------------|------------------------------|
| Open Circuit | 49% |
| Resistance Drift | 22% |
| Lead Break | 17% |
| Other | 7% |
3. **Failure Mechanism Analysis**
The failure mechanism of a resistor is multifaceted, involving various physical and chemical processes that occur under operational or environmental conditions. These processes contribute to the aging of the resistor over time.
**(1) Structural Changes in Conductive Materials**
Thin-film resistors typically have an amorphous structure in their conductive layers. According to thermodynamics, this structure tends to crystallize over time. As crystallization progresses, the internal structure becomes denser, which may lead to a decrease in resistance. The rate of crystallization increases with temperature.
During manufacturing, mechanical stress can distort the internal structure of the resistor. Smaller wire diameters or thinner film layers are more susceptible to this effect. Heat treatment can help reduce internal stress, and over time, residual stress may gradually dissipate, causing changes in resistance.
Both crystallization and stress relaxation processes slow down over time but do not stop during normal use. They generally occur at a relatively constant rate, leading to small resistance changes—typically a few thousandths of the original value.
**Electrical Load and High-Temperature Aging**
Electrical load accelerates the aging of resistors, often more significantly than elevated temperature alone. The contact area between the resistor and the lead cap experiences higher temperatures, which can reduce the resistor's lifespan. For example, a 10°C increase in temperature can halve the resistor's life. If the temperature rises by 50°C, the life may be reduced to just 1/32 of the normal value. A four-month accelerated life test can predict the stability of a resistor over ten years.
**DC Load – Electrolysis**
Under DC load, electrolysis can occur in groove resistors, causing ion movement between grooves. This is more intense in the presence of moisture. Depending on the type of resistive film, it may lead to oxidation or reduction. In high-resistance thin-film resistors, electrolysis can increase resistance and even damage the film. Testing under hot and humid conditions helps evaluate the material’s resistance to oxidation, reduction, and moisture.
**(2) Vulcanization**
In one case, resistors used in a chemical plant failed after one year. Analysis showed that the thick-film chip had increased resistance and became open-circuited. Microscopic examination revealed black crystalline material—silver sulfide—on the electrode edges, indicating sulfur corrosion from the air.
**(3) Gas Adsorption and Desorption**
Film resistors may adsorb small amounts of gas at grain boundaries or between conductive particles and binders. This affects conductivity and resistance. When working under vacuum, desorption can improve contact between particles and lower resistance. Conversely, when operating under normal pressure, gas adsorption may increase resistance. Temperature and pressure are key factors influencing this process, with resistance changes reaching up to 1–2%.
**(4) Oxidation**
Oxidation is a long-term process that starts from the surface and progresses inward. Most materials are affected by oxygen, leading to increased resistance. Thinner films are more vulnerable. Sealing with inorganic materials like metals or ceramics offers better protection than organic coatings, though they may introduce new aging factors.
**(5) Impact of Organic Protective Layers**
During the formation of organic protective layers, volatile substances may diffuse into the resistor, increasing resistance. This effect is most significant in the first 2–8 months. To ensure stability, it is advisable to store finished products for a period before shipment.
**(6) Mechanical Damage**
Mechanical strength is crucial for resistor reliability. Defects in the base, damage to the lead cap, or broken leads can all lead to failure. Ensuring robust construction is essential for long-term performance.
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Digital Amplifier Module​
The Digital Amplifier Module is a crucial component in the field of audio, delivering exceptional audio amplification for various audio devices. Leveraging digital signal processing technology, it enables precise manipulation of audio signals, achieving performance enhancements that are difficult to match with traditional analog Power Amplifiers.​
Working Principle​
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