Benefits of using precious metals such as gold and silver on PCBs?

When some manufacturers advertise their products, they will specifically mention that their products use special techniques such as gold plating and silver plating. What is the use of this process?

The surface of the PCB needs to be soldered, requiring a portion of the copper layer to be exposed for soldering. These exposed copper layers are called pads. The pads are generally rectangular or round and have a small area. We know that the copper used in the PCB is extremely susceptible to oxidation. Therefore, after soldering the solder mask, the only copper that is exposed in the air is the pad. If the copper on the pad is oxidized, not only is it difficult to solder, but also the resistivity greatly increases, seriously affecting the final product performance. So, engineers have come up with a variety of ways to protect the pad. For example, it is coated with inert metal gold, or a layer of silver is covered by a chemical process on the surface, or a special chemical film is used to cover the copper layer to prevent the contact between the pad and the air.

From this point of view, whether it is gold or silver, the purpose of the process itself is to prevent oxidation, protect the pad, and ensure the product yield rate in the next soldering process. However, the use of different metals will impose requirements on the storage time and storage conditions of PCBs used by production plants. Therefore, the PCB factory will generally use the vacuum plastic packaging machine to pack the PCB before the PCB is produced and delivered to the customer to ensure that the PCB is not oxidized. Before the final component is machine soldered, the board manufacturer also tests the degree of oxidation of the PCB, rejects the oxidized PCB, and guarantees the product yield rate. In the end, the board that consumer gets, has passed all kinds of tests, even if the oxidation occur after long time use that also will only happen in the connection part of inserting and drawing almost, and have no effect on the pad and already soldered component.

Since the resistance of silver and gold is lower, will the use of special metals such as silver and gold reduce the amount of heat generated by the PCB?

We know that the biggest factor that affects heat is resistance. The resistance is related to the material of the conductor itself, the cross-sectional area and the length of the conductor. The thickness of the metal material on the surface of the pad is much lower than 0.01 mm. If the pad processed by the OST (organic protective film) method is used, there will be no excess thickness at all. The electrical resistance exhibited by such a tiny thickness is almost equal to zero, and even cannot be calculated, certainly not affecting the amount of heat generated.