The reasons why the circuit board is burned are as follows:
1. The voltage is too high. When the voltage the circuit board withstands exceeds its rated voltage, various components will be burned out.
2. Environmental factors. When assembling electronic components, it is important to control environmental conditions. For example, humidity in a room can cause all kinds of problems. Likewise, dust and heat can affect PCB boards.
3. Human factors. Improperly manufactured or placed components can cause many problems. Examples include improper welding, chemical leakage, poor connectivity between layers, loose components, etc.