There are four primary electroplating methods used in circuit boards: finger row electroplating, through-hole electroplating, reel-linked selective plating, and brush plating.

Here’s a brief overview:

**Finger Row Electroplating:**

Rare metals are plated on the edge connectors of the board, the protruding contacts, or gold fingers to achieve lower contact resistance and enhanced wear resistance. This process is known as finger row electroplating or protruding part electroplating. Typically, gold is plated onto the protruding contacts of the board edge connector over a nickel underlayer. The gold fingers or protruding sections of the board edge can be plated either manually or automatically. Currently, gold plating is commonly used for the contact plug or gold finger, as opposed to plated buttons.

The process for finger row electroplating is as follows:

1. Strip coating to remove tin or tin-lead coatings from the protruding contacts.

2. Rinse with washing water.

3. Scrub with abrasives.

4. Activate in a 10% sulfuric acid solution.

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This retains the original meaning while enhancing clarity and flow.


1. The thickness of nickel plating on the protruding contacts ranges from 4 to 5 μm.

2. Clean and demineralize water.

3. Treatment with a gold penetration solution.

4. Gold plating.

5. Cleaning.

6. Drying.

7. Through-hole plating:

8. There are various methods to create an electroplating layer that meets the specifications on the walls of drilled holes in the substrate. This process is referred to as hole wall activation in industrial contexts. The commercial production of printed circuits necessitates multiple intermediate storage tanks, each with its own control and maintenance protocols. Through-hole plating is an essential follow-up to the drilling process. When the drill bit penetrates the copper foil and the underlying substrate, the heat generated melts the insulating synthetic resin that makes up most of the substrate matrix. The molten resin, along with other drilling debris, accumulates around the hole and coats the newly exposed hole wall of the copper foil. This accumulation is detrimental to the subsequent electroplating surface. The molten resin also leaves a layer of hot shaft on the hole wall, exhibiting poor adhesion to most activators, which necessitates the development of specialized decontamination and etch-back chemical technologies.

9. A method that is more suitable for PCB prototyping involves using a specially designed low-viscosity ink to form a high-adhesion, high-conductivity film on the inner wall of each through hole. This approach eliminates the need for multiple chemical treatments; a single application followed by thermal curing results in a continuous film on the inner surfaces of all hole walls, allowing for direct electroplating without additional treatment. This resin-based ink adheres strongly and can be easily applied to the walls of most thermally polished holes, thereby removing the etch-back step.

10. Reel linkage selective plating:

11. The pins and connectors of electronic components—such as connectors, integrated circuits, transistors, and flexible printed circuits—utilize selective plating to achieve optimal contact resistance and corrosion resistance. This electroplating method can be performed manually or automatically. Selectively plating each pin individually is quite costly, thus batch welding is employed. Typically, the two ends of the metal foil, rolled to the desired thickness, are punched, cleaned using chemical or mechanical methods, and then selectively plated with materials like nickel, gold, silver, rhodium, tin-nickel alloy, copper-nickel alloy, or nickel-lead alloy for continuous electroplating. In the selective plating method, a resist film is first applied to the areas of the copper foil board that do not require electroplating, allowing electroplating only on the selected portions.

12. Brush plating:

13. Another technique for selective plating is known as “brush plating.” This is an electrodeposition method in which not all parts are immersed in the electrolyte during the plating process. In this PCB electroplating technology, only specific areas are electroplated, leaving the rest unaffected. Rare metals are typically plated onto selected areas of the printed circuit board, such as board edge connectors. Brush plating is frequently used when repairing discarded circuit boards in PCB assembly workshops. A special anode (a chemically inert anode, such as graphite) is wrapped in an absorbent material (like a cotton swab) and used to deliver the electroplating solution to the targeted areas.

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