PCB finishing processes are a common aspect of electronic assembly services. However, finishing processes vary and one of those processes is plating. In electronic assembly services, the plating process uses a chemical to fuse all of the different layers of the PCB together. PCB production knows four main types of plating: gold finger-plated plating, through-hole plating, reel linkage selective plating, and brushing plating. This article will discuss these four different methods in more detail.
1. Gold finger plating
Gold fingers are electroplated edge-connectors the are generally used to connect PCBs to a motherboard. Since gold fingers are mainly used for plugging, the gold thickness should be between 3u“ to 50u“. The expectant cycles of gold fingers are approximately 1,000 before any repair is needed, however, that is only if the correct thickness is used and if the gold fingers are applied correctly.
2. Through-hole plating
Through-hole plating is a crucial step in the manufacturing process for drilling. This method is beneficial as it allows both sides of the printed circuit board to be used and connect to other layers of the board. This method uses copper plating to allow electrical conductivity to travel through the board. The thicker the copper plating, the longer it can go through this thermal cycling without cracking. The life of the printed circuit board is dependant on the thickness of the copper plating of the through-hole.
Through-holes without the copper plating lack conductivity and electricity, and is unable to connect to the other side or other boards.
3. Selective plating
Selective plating is the ultimate method for corrosion resistance and good contact resistance. Selective plating is suitable for electronic components that use contact pins. The process of individually selecting the pins is extremely expensive so most electronic assembly services use batch welding. Selective plating only uses the portion of the metal copper foil plate that is selected, as the other part is coated with a resist film.
4. Brushing plating
Brushing plating is also a form of selective plating. It is a plating technique that only uses a select amount of parts of electrolyte during the plating process, thus only a limited portion gets plated. This plating method is commonly used by electronic assembly services when repairing waste boards.