Open the electronic device and you may find that there are some boards printed with complex patterns, these are PCBs, also known as printed circuit boards). PCB is the carrier of electronic components, which connects various components through conductive lines to realize the function of the circuit. The circuits of the PCB are generally made of copper because of the good conductivity and cheap cost of copper. However, if you look closely, you will see that the circuitry of the PCB is not copper, but yellow or gold, why is that?Today, Jetobang is here to answer this puzzle for you.
Surface treatment of PCBs.
In fact, the circuit of the PCB is not really yellow or gold, but a protective layer is applied to the surface of the copper, which is called PCB surface treatment. The purpose of PCB surface treatment is as follows:
1.Prevents oxidation of copper. Although copper is not as easy to rust as iron, it will gradually oxidize in the air, forming a layer of dark red copper oxide, which will reduce the conductivity of copper and affect the performance of the circuit. Therefore, it is necessary to coat the surface of the copper with a protective layer that can isolate the air and prevent the oxidation of the copper.
2.Improve welding performance. In the process of PCB production, various components need to be fixed on the PCB by soldering, which requires the circuit of the PCB to have good soldering performance, that is, it can be firmly combined with the solder. If the circuit surface of the PCB is oxidized, it will affect the welding effect, and even cause problems such as virtual soldering and missing soldering. Therefore, it is necessary to coat the surface of the copper with a protective layer that can improve the welding performance and make the welding smoother.
3.Increase aesthetics. If the circuit of the PCB is 8990 copper, it may appear monotonous and boring, and it is easy to be reflected by light, which affects observation and detection. Therefore, it is necessary to coat the surface of the copper with a protective layer that can increase the aesthetics, so that the circuit of the PCB presents different colors, such as yellow, gold, green, blue, etc.
The method of surface treatment of PCB.
There are many ways to treat the surface of PCB, different methods have different characteristics and applications, here are the two most common methods: gold plating and immersion gold.
Gild. Gold plating is a method of coating the surface of copper with a layer of gold through an electrochemical reaction. Gold is a very stable metal, does not oxidize, and has high conductivity and solderability, so gold plating can effectively protect the copper wiring and improve the performance and life of the PCB. The advantages of gold plating are:
1.Gold-plated PCBs can be stored for a long time without discoloration or deterioration, making them suitable for long-term use or stockpiling.
2.The gold-plated PCB can withstand high temperatures without falling off or deforming, and is suitable for high-temperature soldering or high-temperature working environments.
3.Gold-plated PCB can improve the transmission quality of signals, reduce signal loss and interference, and are suitable for high-frequency, high-speed, and high-precision circuits.
Immersion gold. Immersion gold is a method of depositing a layer of gold on the surface of copper through a chemical reaction. The difference between immersion gold and gold plating is that immersion gold only deposits gold on the pads, whereas gold plating is gold plating on the entire circuit. The advantages of immersion gold are:
1.The immersion gold PCB has smooth circuits with no protrusions or depressions, making it suitable for surface mount technology and the installation of miniature components.
2.The soldering performance of immersion gold PCB is good, because the crystal structure of immersion gold is finer than that of gold plating, which is easier to combine with solder, and the hardness of immersion gold is lower than that of gold plating, which is not easy to cause brittleness of solder joints.
3.Signal transmission of immersion gold PCB*** Because immersion gold only immerses gold on the pad, it will not affect the impedance of the line, and the immersion gold line will not produce gold wires, which reduces the risk of failure.
Therefore, the reason why the circuits of the PCB are yellow or gold is because the surface of the copper is treated with gold plating or immersion gold to protect the copper circuits and improve the performance and aesthetics of the PCB. What else do you want to know about PCBs?You can leave a message to Jetobang!