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What factors affect the damage of SMT varistors?

2018-12-04 16:33

The main material of SMT varistors is semiconductors, which are varieties of semiconductor resistors. When the SMT varistor malfunctions or is damaged, it is mainly affected by the following factors.

1. Insufficient voltage resistance

This situation can actually be well understood. If the working voltage of a product is 220 volts and the varistor you are using is 180 volts, then it will definitely break down and be damaged. 2. Excessive current and surge

The application in the product is to insert and remove devices, which can damage the rheostat. There is a significant surge during product insertion and removal (the devices at both ends are not grounded). At this point, the withstand voltage of the varistor will weaken the protective ability of the product itself and the TV, resulting in a high damage rate.

Recommend these methods for thermistor overheating protection:

1. Using springs to pull low melting point soldering technology

This method is currently the method chosen by most manufacturers. A low melting point solder joint has been added to the pins of the variable resistor. Secondly, use springs to pull the welding points. When the leakage current of the varistor is high and the temperature is high, the solder at the welding point melts. Under the tension of the spring, the solder joint quickly separates, the rheostat is removed from the circuit, and at the same time, the alarm contact linkage sends an alarm signal.

2. Sealing method

In order to solve the problem of smoke, fire, and explosion when varistors malfunction, some manufacturers will use this method to package varistors. Considering that internal arcs may occur when it fails, leading to the failure of sealing materials and carbon, thereby maintaining the arc, this usually leads to internal short circuits and blackening of the equipment.

3. Isolation technology

In this method, the varistor is installed in a closed box and isolated from other circuits to solve the problem of smoke and flame propagation in the varistor. In the event of various backup protection failures, isolation technology is undoubtedly a very simple and effective method, occupying a large amount of equipment space and solving the problem of smoke and flames emitted from the lead holes of the box.

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