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Gold, Silver and Copper in PCB

by: Sep 19,2019 916 Views 0 Comments Posted in PCB Basic Information

Immersion Silver Immersion Gold PCB CCL

The PCB is support for electronic components and is a carrier for electrical connection of electronic components, mainly for supporting and interconnecting. From the outside, the outer layer of the board has three main colors: gold, silver, and light red. Classified by price: gold is the most expensive, silver is second, light red is the cheapest. However, the circuit inside the board is mainly pure copper, which is bare copper.


Why are there precious metals on the PCB?


PCB as a support for electronic components, the surface of which requires soldering components, requires a portion of the copper layer to be exposed for soldering. These exposed copper layers are called pads. The pads are generally rectangular or circular, and the area is small. Therefore, after the solder resist is applied, the only copper exposed on the pad is exposed to the air.

The exposed pad on the PCB, the copper layer is directly exposed. This part needs protection to prevent it from being oxidized.

The copper used in the PCB is easily oxidized. If the copper on the pad is oxidized, it is not only difficult to solder, but also the resistivity is greatly increased, which seriously affects the performance of the final product. Therefore, the pad is plated with inert metal gold, or a layer of silver is chemically coated on its surface, or a special chemical film is used to cover the copper layer to prevent contact between the pad and the air. Prevents oxidation and protects the pad from ensuring yield during the next soldering process.


Gold, silver and copper on the PCB


1, PCB CCL

The copper-clad laminate is a plate-like material which is obtained by immersing a glass fiber cloth or other reinforcing material on one side of the resin or double-sided coated with a copper foil and hot pressing.

Taking glass fiber-based copper-clad laminates as an example, the main raw materials are copper foil, glass fiber cloth, and epoxy resin, which account for about 32%, 29% and 26% of the product cost respectively.

CCL is the basic material of printed circuit boards, and printed circuit boards are the indispensable main components of most electronic products to achieve circuit interconnection. With the continuous improvement of technology, some special electronic CCLs can be used in direct manufacturing of printed electronic components in recent years. Conductors for printed circuit boards are generally made of thin foil-like refined copper, that is, copper foil in a narrow sense.


2, PCB immersion gold circuit board