- Jun 15, 2017 -
What are the special requirements for varistor in PCBA design?
1, the use of temperature/preservation temperature
Keep the working temperature of the SMT circuit within the range of the use temperature indicated in the product specification. After mounting, the storage temperature of the circuit when not working is kept in the range of the use temperature specified in the product specification book. The PCBA shall not be used at a high temperature exceeding the specified maximum operating temperature.
2, the use of voltage
The voltage between the varistor terminals should be kept below the permissible circuit voltage. If the wrong use, will lead to product failure, short circuit, may produce fever phenomenon. The voltage is below the rated voltage, but in the continuous application of high-frequency voltage or pulse voltage of the circuit, we must fully discuss the reliability of Varistor.
3. Element heating
The surface temperature of the varistor should be kept below the maximum operating temperature specified in the product specification (the temperature rise due to the heating of the component itself). The use of circuit conditions caused by temperature rise in the Varistor, PCBA please in the actual use of equipment working state to confirm.
4, the use of place restrictions, varistor can not be used in the following places
1 A place with water or brine;
2 The place of easy condensation;
3 The corrosive gas (hydrogen sulfide, sulfurous acid, * *, ammonia, etc.) places;
4 the vibration or impact condition of the use place shall not exceed the scope of the product specification specification;
5, circuit board designated
The performance of the Alumina circuit board may deteriorate due to thermal shock (temperature cycling). When PCBA is used, it is necessary to confirm whether the PCB has an effect on the quantity.
6, the size of the pad set
The more welding volume, pressure-sensitive resistance will also increase the pressure, and will cause the component surface cracks and other quality problems, so in the circuit board design, according to the welding volume set appropriate shape and size.
Please keep the size of the pad equal when designing. PCBA if the solder volume of the left and right solder plate is different, welding cooling when the side of the solder more than the curing will be delayed, the other side may be stress caused by the parts crack.
7. Configuration of spare parts
Pressure-sensitive resistance welding installed in the circuit board after the project, or the circuit board in the process of bending, may lead to pressure-sensitive resistance rupture, so the configuration of components should fully consider the bending strength of the circuit board, not to exert too much pressure.