The thermistor, as a nonlinear electronic component that is highly sensitive to temperature, utilizes the resistance temperature effect of semiconductor materials to achieve its function. Its temperature coefficient of resistance is much higher than that of metal, which makes it play an important role in measuring temperature, humidity, air pressure and microwave power. It is widely used especially in the field of industrial automatic control. Thermistors' small size, fast response and excellent performance make them an indispensable part of measurement and control systems.
Among many thermistor types, NTC thermistors are widely used due to their unique operating characteristics. However, NTC thermistors may encounter some problems during use, the most serious of which is the phenomenon of sparking and exploding at the moment of power-on. This phenomenon not only affects the normal operation of the equipment, but may also cause safety hazards. In response to this problem, we conducted an in-depth analysis and proposed corresponding solutions.
First of all, there are three main reasons why NTC thermistor ignites and explodes:
The sintering temperature of NTC thermistor is low. This causes the porcelain body to be incompletely sintered and the grain size is uneven, thus forming local high-resistance areas inside. These high-resistance areas are prone to local overheating when current passes through, which can lead to melting and fragmentation of the porcelain body.
There is insufficient margin between the electrodes of the NTC thermistor and the porcelain body. Insufficient margins make the electrode edges prone to defects, which may cause explosions under the action of high current.
Abnormally large currents appear in the lines. This situation exceeds the surge current range that the resistor itself can withstand, triggering sparking and explosion events.
In response to the above problems, we propose the following improvement measures:
Optimize the sintering process of thermistors. By controlling the sintering temperature within a more appropriate range, uniformity of grain size and uniform distribution of current can be ensured, thereby improving the resistor's surge resistance and reducing melting and fragmentation caused by local high resistance.
Increase the margin between the electrode and the porcelain body. In this way, defects at the edges are reduced, thereby reducing the risk of bursting.
When using NTC thermistors, users should ensure that abnormally large currents do not appear in the circuit. This can be achieved through proper circuit design and appropriate protection measures.