In current printed circuit boards, copper is used especially to interconnect the components in the substrate. Traditionally, copper is used as a material to form a pattern of electric connectivity tracking; Whenever copper is exposed without an adequate coating and exposed to air for a long period of time, copper will easily tarnish due to oxidation. Then it will corrode and lose its weldability. Due to this problem, multiple techniques are used to protect copper tracks, through holes and through holes (PTH).
One method is coated with organic coating, oxide coating and the coating method that many manufacturers used long ago. The organic coating of PCB, although it is simple in its application, is not recommended for long-term use due to the ability of the manufacturer to control the thickness process, the composition and also the curing cycles. It can also cause an unpredictable deviation in weldability. However, with the lead-free application, it is now widely used in consumer PCBs by PCB China manufacturers.
The oxide coating can protect the circuit from corrosion, however, it does not preserve the weldability of the PCB. The most standard long-standing method for PCB China manufacturers is the metal coating process, which was standard practice to ensure weldability and protect the circuit from corrosion before the period of application of the lead-free era. Therefore, it was a key factor and plays an important role in the manufacture of double-sided and multi-layer (PTH) plates for PCBs in the past.
In particular, placing a weldable metal over the tracks was a standard practice for providing weldable protection to copper tracks. In addition, the edge connectors added with spring contacts that are coupled with connector tabs suitably designed on printed circuit boards, are used for the interconnection of several modules in electronic equipment. These electrical contacts are expected to have a high degree of wear resistance and low contact resistance. This will ensure a precious metal in these contacts and the most commonly used metal is gold. Other metals used for the coating are tin-plating of the tracks, nickel-plating and, in some cases, copper-plating to build some of the tracking areas.