The first type is finger plating
Rare metals often need to be plated on board edge connectors, protruding contacts, or gold fingers to provide lower contact resistance and higher wear resistance. This technology is called finger plating or protruding part plating. Gold is often plated on the protruding contacts of board edge connectors with nickel inner layer coating. The gold fingers or protruding parts of the board edge are plated manually or automatically. Currently, the gold plating on contact plugs or gold fingers has been replaced by electroplating, lead plating, and button plating. The process is as follows:
1) Peel off the coating to remove tin or tin lead coating on protruding contacts
2) Rinse with cleaning water
3) Scrubbing with abrasives
4) Activated in 10% sulfuric acid
5) Nickel plating with a thickness of 4-5 μ m on the protruding contact
6) Clean and remove mineral water
7) Gold infiltration solution treatment
8) Gold plating
9) Cleaning
10) Drying
The second method is through-hole electroplating
There are multiple methods to establish a compliant electroplating layer on the hole wall of the substrate drilling, which is called hole wall activation in industrial applications. The commercial production process of printed circuits requires multiple intermediate storage tanks, each with its own control and maintenance requirements. Through hole electroplating is a necessary subsequent manufacturing process in the drilling process. When the drill bit passes through the copper foil and the substrate below it, the heat generated melts the insulating synthetic resin that makes up most of the substrate matrix. The melted resin and other drilling debris accumulate around the holes and are coated on the newly exposed hole walls in the copper foil. In fact, this is harmful to the subsequent electroplating surface. The melted resin will also leave a layer of thermal axis on the substrate hole wall, which exhibits poor adhesion to most activators. This requires the development of a technology similar to stain removal and etching chemistry.
A more suitable method for prototyping printed circuit boards is to use a specially designed low viscosity ink to form a highly adhesive and conductive coating on the inner walls of each through-hole. This eliminates the need for multiple chemical treatment processes, requiring only one application step followed by thermal curing to form a continuous coating on the inside of all hole walls, which can be directly electroplated without further treatment. This ink is a resin based substance that has strong adhesiveness and can effortlessly adhere to most hot polished hole walls, eliminating the step of etching back.
The third type is the roller linked selective plating
The pins and pins of electronic components, such as connectors, integrated circuits, transistors, and flexible printed circuits, are selectively plated to achieve good contact resistance and corrosion resistance. This electroplating method can be done manually or automatically. It is very expensive to select plating for each pin separately, so batch welding must be used. Usually, the two ends of a metal foil that has been flattened to the desired thickness are punched, cleaned using chemical or mechanical methods, and then selectively electroplated continuously using materials such as nickel, gold, silver, rhodium, nickel or tin nickel alloys, copper nickel alloys, nickel lead alloys, etc. When choosing this electroplating method, first apply a layer of resist film on the parts of the metal copper foil that do not require electroplating, and only electroplate on the selected copper foil parts.
The fourth type is brush plating
Another method of choosing plating is called “brush plating”. It is an electrodeposition technique where not all parts are submerged in the electrolyte during the electroplating process. In this electroplating technique, only a limited area is electroplated without any impact on the rest. Usually, rare metals are plated on selected parts of printed circuit boards, such as areas like board edge connectors. Brush plating is more commonly used in electronic assembly workshops for repairing discarded circuit boards. Wrap a special anode (chemically inactive anode, such as graphite) in an absorbent material (cotton swab) and use it to bring the electroplating solution to the desired location for electroplating.
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