Needless to say, PCB is the support body of electronic components and the carrier of electrical connection of electronic components, which mainly plays the role of support and interconnection. Now printed circuit board (PCB) is widely used in various electronic and related products. There are three main colors on the external layer, such as gold, silver, and light red. They are classified by price: gold is the highest price, silver is second, and light red is the cheapest. But there is mainly pure copper that is bare copper in the internal of printed circuit board.
Why are there precious metals on the PCB?
Why are there precious metals on the PCB?
PCB as a support for electronic components, its surface needs to be soldering components, so there is a part of copper layer requiring to be exposed for soldering. These exposed layers of copper are called pads, which are usually rectangular or round, and they are very small in size, so the only copper exposed on the pad is exposed to the air after applying the solder resist.
The copper layer is directly exposed in the external where the exposed pad on the PCB. It needs to protect the parts from being oxidized.
What’s more, it’s easy to oxidize the copper used in the PCB. If the copper on the pad is oxidized, it will be not only hard to solder but also greatly increasing the resistivity, which makes a serious effect on the performance of the final product. So the soldering pad is plated with inert metal gold, or the surface is covered with silver by chemical process, or the copper layer is covered with a special chemical film to prevent the contact between the soldering pad and the air. Prevent oxidation and protect pad to make sure good yield in subsequent soldering process.
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