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There are 7 special requirements that need to be paid attention to in the varistor in PCBA design
2024-01-10
The special requirements for varistors in PCBA design, the following is for you to sort out and introduce what are the requirements for varistors in PCBA design?
1. Operating temperature/storage temperature:
The operating temperature of the attached circuit is kept within the operating temperature range indicated in the product specification sheet. After mounting, the storage temperature when the circuit is not in operation is kept within the operating temperature range specified in the product specification. Do not use at high temperatures that exceed the specified maximum operating temperature.
2. Use voltage
The voltage applied to the varistor terminals should be kept below the maximum allowable circuit voltage. If used incorrectly, the product will malfunction, short circuit, and heat may occur. When using a voltage below the rated voltage, it is important to consider the reliability of the varistor when using it in a circuit where a high-frequency voltage or impulse voltage is continuously applied.
3. The component is heated
The surface temperature of the varistor should be kept below the maximum operating temperature specified in the product specification (consider the temperature rise caused by the heating of the component itself). If the temperature of the varistor rises due to the circuit conditions in use, check the operating condition of the equipment actually in use.
4. The use of the place is restricted, and the varistor cannot be used in the following places:
1) Places with water or salt water;
2) Places prone to condensation;
3) Places with corrosive gases (hydrogen sulfide, sulfurous acid, ammonia, etc.);
4) The vibration or impact conditions of the place of use shall not exceed the range specified in the product specification;
5. The circuit board is selected
The performance of alumina circuit boards may deteriorate due to thermal shock (temperature cycling). When using it, it is necessary to check whether the board has any effect on the quality.
6. Set the pad size
The higher the amount of soldering, the greater the pressure on the varistor, which can cause quality problems such as cracks on the surface of the component, so it is necessary to set the appropriate shape and size according to the amount of soldering when designing the pads of the board.
When designing, keep the size of the pads evenly balanced. If the amount of solder on the left and right pads is different, the curing of the one with the more solder will be delayed when the solder is cooled, and the other side may be stressed and cracks may appear in the part.
7. Configuration of parts
Since the varistor is soldered to a circuit board or the circuit board is bent during operation, the varistor may break, so it is necessary to fully consider the bending strength of the circuit board when placing the components and not to apply excessive pressure.
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