Circuit components: In order to improve the functionality of printed boards, there are now more and more printed components. In high-frequency digital circuits, wires are transmission lines with impedance requirements and are not simply conductive. There are also inductors, resistors, capacitors, etc. printed on the board surface or buried inside the board.

　　(2) Reliability: withstands certain environmental conditions and has a certain service life.

　　Environmental conditions: The product will definitely be used under certain temperature, humidity, air pressure, and environmental gas conditions. The indoor temperature of the TV, the gas in the refrigerator and kitchen, the electronic instruments of the car are exposed to ice and snow (negative 45 degrees Celsius) and the scorching heat of the desert (positive 60 degrees Celsius), and the communication equipment of the ship is affected by dampness and salt mist in harsh weather conditions. Printed boards may be subjected to these environmental conditions, as well as conditions such as welding, baking, cleaning, and handling during assembly.