What are the differences between the gold plating and silver plating processes on a PCB board?

 What are the benefits of using precious metals such as gold and silver on PCBs?


The color has been clearly explained. Now let’s talk about the precious metals on the PCB. Some manufacturers, when promoting their products, will specifically mention that their products adopt special processes such as gold plating or silver plating. So, what are the uses of these processes?

The surface of a PCB needs to have components soldered onto it, which requires a portion of the copper layer to be exposed for soldering. These exposed copper layers are called pads, and they are usually rectangular or circular in shape, with a very small area. We know that the copper used in PCBs is highly prone to oxidation. Therefore, after applying soldering resist paint, the only thing exposed to the air is the copper on the pads.

If the copper on the pads is oxidized, not only is it difficult to solder, but the resistivity also increases significantly, seriously affecting the performance of the final product. Therefore, engineers came up with various methods to protect the pads. For example, they can coat the pads with inert metal gold, or cover the surface with a layer of silver through a chemical process, or use a special chemical film to cover the copper layer to prevent the pads from coming into contact with the air.

The exposed pads on the PCB, with the copper layer exposed directly. This part needs to be protected to prevent it from being oxidized. From this perspective, whether it is gold or silver, the purpose of the process is to prevent oxidation, protect the pads, and ensure the yield rate in the subsequent welding process.

However, using different metals will require specific requirements for the storage time and conditions of the PCBs used by the production factory. Therefore, PCB factories usually package the PCBs with a vacuum encapsulation machine before the PCB production is completed and delivered to the customers for use. This ensures that the PCBs are protected from oxidation damage to the greatest extent.

Before the final component is mounted on the board, the board manufacturer also needs to test the degree of oxidation of the PCB once, eliminate the oxidized PCBs, and ensure the yield rate. The final board card that the consumer receives has undergone various tests. Even after long-term use, oxidation is almost only likely to occur at the connection points and has no significant impact on the pads and the already welded components.

Since silver and gold have lower resistivity, then after using special metals such as silver and gold, will the heat generated during the use of PCB be reduced?

We know that the biggest factor affecting heat generation is resistance. Resistance is related to the material of the conductor itself, the cross-sectional area of the conductor, and its length. The thickness of the metal material on the pad surface is even lower than 0.01 millimeters. If the pads are treated with OST (organic protective film) method, there will be no additional thickness at all. Such a tiny thickness results in a resistance almost equal to 0, which cannot be calculated, and of course, it will not affect the heat generation.
If you would like to know more about the production issues of PCB&PCBA products, please contact Sandy via email: sales9@hitechpcb.com

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