The first type is finger row plating.
Rare metals are often required to be plated on board edge connectors, board edge protruding contacts or gold fingers to provide low contact resistance and high wear resistance, which is called finger-row plating or protruding partial plating technique. It usually plates gold in the inner layer of the nickel-plated plate edge connector protruding contact head and the G/F or the protruding part of the plate edge adopts manual or automatic plating technology. At present, the gold plating on the contact plug or the G/F has been replaced by plating, lead and knob.The process is described as below:
1) Strip the coating to remove the tin or tin-lead coating on the protruding contacts
2) Rinse with washing water
3) Scrubbing with abrasives
4) Activation is diffused in 10% sulfuric acid
5) The thickness of nickel plating on the protruding contacts is 4 -5μm
6) Cleaning and demineralizing water
7) Gold penetration solution treatment
8) gold-plated
9) Cleaning
10) Drying
The second type is through-hole plating.
There are many ways to build a layer of electroplating layer that meets the requirements on the hole wall of the substrate drilled hole, which is called hole wall activation in industrial applications. The commercial production process of its printed circuit requires multiple intermediate storage tanks and every tank has its own control and maintenance requirements. Through-hole plating is a necessary follow-up process of the drilling process. When the drill drills through the copper foil and the substrate underneath, the heat generated melts the insulating synthetic resin that constitutes most of the substrate matrix. As a consequence, the molten resin and other drilling debris piled up around the hole and coated on the newly exposed hole wall of the copper foil, which in fact is harmful to the subsequent electroplating surface. What’s more, the melted resin will also leave a layer of hot axis on the pore walls of the substrate, which exhibits poor adhesion to most activators, requiring the development of a class of techniques such as stain removal and erosion-back chemistry.
A more suitable method for prototyping printed circuit boards is to use a specially designed low-viscosity ink to form a highly adhesive, highly conductive film covering on the inner wall of each through hole. In this way, instead of using multiple chemical treatments, we need only a single application step, followed by thermal curing, can form a continuous coating on the inner side of all the hole walls. In this way, only using a single application step can we form a continuous coating on the inner side of all the hole walls, rather than using multiple chemical treatment processes,which can be directly plated without further treatment. This ink is a resin-based material that is highly adhesive and can be effortlessly bonded to most heat-polished hole walls, thus eliminating the step of back erosion.
The third type is reel linkage type selective plating.
The pins and pins of electronic components, such as connectors, integrated circuits, transistors, and flexible printed circuits, are all selectively plated to obtain good contact resistance and corrosion resistance. This kind of electroplating method can be manual or automatic and it is very expensive to selectively plate each pin individually, so batch welding must be used. Usually, the ends of the metal foil that is rolled to the required thickness are punched, cleaned by chemical or mechanical methods, and then selectively used such as nickel, gold, silver, rhodium. Usually, the ends of the foil of the desired thickness are punched, cleaned chemically or mechanically, and then, optionally, plated continuously with such metals as nickel, gold, silver, rhodium, or tin-nickel, copper-nickel, or nickel-lead for continuous electroplating. In the electroplating method of selective plating, we only need to plate in the selected part of the copper foil, so we must first coat a layer of resist film on the part of the metal copper foil board that does not need to be electroplated.
The fourth type is brush plating.
Another selective plating method is called "brush plating"which is an electrodeposition technique, and not all parts are immersed in the electrolyte during the electroplating process. In this kind of electroplating technology, only a limited area is electroplated and there is no effect on the rest. Usually, rare metals are plated on selected parts of the printed circuit board, such as board edge connectors. Brush plating is used more when repairing discarded circuit boards in electronic assembly workshops. Wrap a special anode (a chemically inactive anode , such as graphite) in an absorbent material (cotton swab), and use it to bring the electroplating solution to the place where electroplating is needed.
