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<p><br></p><p>• Significance of <a href="https://www.atechpcb.com/pcb-manufacturing" rel="noopener noreferrer" target="_blank"><strong>PCB</strong></a> surface coating</p><p><br></p><p><br></p><p>In order to prevent the copper surface of<a href="https://www.atechpcb.com/pcb-manufacturing" target="_blank"> PCB</a> pads from being oxidized and contaminated before solderability, surface protection (also called surface treatment) of copper is of great significance.</p><p><br></p><p><br></p><p>Copper has the second best electrical conductivity and physical properties (the best is silver), as well as abundant storage and low cost, so copper is selected as the conductive material for PCBs. However, as an active metal, copper is easily oxidized, so that an oxide layer (copper oxide or cuprous oxide) is easily formed on the surface, which leads to defects in solder joints, thereby reducing product reliability and shortening the shelf life.</p><p><br></p><p><br></p><p>According to statistics, 70% of the defects on the <a href="https://www.atechpcb.com/pcb-manufacturing" rel="noopener noreferrer" target="_blank">PCB board</a> come from solder joints due to the following two reasons:</p><p><br></p><p><br></p><p>Reason 1: Pollution and oxidation on the PCB pads are likely to cause incomplete soldering and cold solder joints.</p><p><br></p><p><br></p><p>Reason 2: Due to the diffusion between silver and copper, it is easy to produce a diffusion layer, and between tin and copper, it is easy to produce intermetallic compound (IMC), which leads to loose and fragile interfaces.</p><p><br></p><p><br></p><p>Therefore, a protective layer with solderability or isolation function should be formed on the copper surface to be soldered to reduce or avoid defects.</p>
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