A PCB assembly is the most crucial element in the functioning of several electronic and electromechanical devices. Hence, it must not only be carefully designed but also be secured from exposure to dirt, heat, moisture, oxidation, and other damaging factors. To avoid damage, the PCB plating process is performed. It also offers a plain surface despite the mounted components, wires, solder joints, and more. It is an electrochemical process wherein a coat of metal is applied onto the board. Most PCB assembly services providers offer a number of PCB plating processes. Plating is usually done using conductive metals, copper being the most widely used metal. This post discusses various plating methods, their significance, and more.

PCB Plating Process in Brief

The PCB plating process typically begins after the bare boards are manufactured and ready with drilled holes and vias. After the hole drilling processes, the board needs to be made free of any particles and residues, and hence is cleaned with abrasive chemicals which eliminate rough edges, burrs, and contaminants. Plating a PCB improves the aesthetic appeal of the boards aside from making it easy for component mounting and soldering because of a flat and smooth surface finish. As mentioned, this is an electrochemical process in which a layer of a conductive metal is applied on the board. In this electroless process, a thin layer of conductive metal such as copper is deposited on the board surface as well as into the holes that are drilled for components. This ensures the entire area of the board is free of dirt, contaminants, or any other hindrances which may negatively impact the component mounting and soldering processes. This layering also increases the copper thickness. So, this process, in a way, prepares the board for next steps of PCB assembling.

pcb plating methods

Types of PCB Plating Processes

There are four widely used methods of PCB plating, which may be either automated or manual. Here are some of them.

  1. Through-hole plating: Thru-hole technology is commonly used for component mounting on boards, wherein holes are drilled onto the board and pad soldered to the opposite side. This hole drilling process generates heat which may melt some of the board insulating materials such as plastic resins or fiber. This residue may gather or surround the holes. Hence, the board surface becomes uneven. Through-hole plating is an electroplating technique to smooth and even out the board surface, and helps the components adhere well and stay in place.
  2. Finger plating: This is also partial or specific-portion plating done for components made of rare metals, edge connectors, and so on. The plating metals used in this are gold and nickel which increase the abrasion resistance of the board. This can be done for already tin-plated boards where the metal is removed and the boards are rinsed in sulfuric acid. The cleaned and activated boards are then plated starting from the protruding contact head. After this, excess water and minerals are removed and gold plating is done.
  3. Brush plating: Sometimes, it is essential to immerse certain portions of board in electrolytic solution than the others. This is done for components made of specific metals, which may need a thicker coat or plating than others. Here, brush plating is required to selectively coat the board portions. It is also used in cases where boards need to be opened and some components removed for repairs. When reassembling repaired boards, brush plating is useful as it can coat specific portions or components that were opened or removed. Often, gold is used as a plating metal in this method.
  4. Reel linkage selective plating: This is selective plating done for integrated circuits, transistors, connectors, and so on. This method is tedious and expensive as each pin needs to be selected for plating. However, plating here can be done in batches too. This plating involves a metal foil which is flattened, die-cut, and cleaned, and then plated onto the selected portions of the board. This makes it possible to deposit appropriate amounts of metal plating on ICs, transistors, and so on.

Plating or coating for a proper surface finish is necessary, and choosing the right method that fits your requirements and budget is all the more crucial. If you are a manufacturer of electrical, electronic, or mechanical products with automated or digital functioning, you will need to partner with PCB assembly services provider. Ensure your partner has good enough experience of PCB manufacturing and assembling, particularly in your segment. Do check out the PCB plating processes they offer, among many other factors. Also, they must understand your requirements well. This is because your PCBA directly impacts the functioning of the end product. Suntronic Inc. has several years of market presence and a strong experience in PCB manufacturing, and assembling of even the most complex PCBAs.