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What are the plating methods for pcb circuit boards?

Release Time: 2021/10/29 18:04:21

Four methods of pcb circuit board electroplating

The first type: finger row electroplating

It is often required to plate rare metals on board edge connectors, excellent edge contacts or gold fingers to provide lower touch resistance and higher wear resistance. This technique is called finger row electroplating or outstanding partial electroplating. Gold is often plated on the outstanding contacts of the board edge connector with the inner plating layer of nickel. The gold finger or the outstanding part of the board edge is selected by technology or active plating technology. At present, the gold plating on the touch plug or gold finger has been plated or lead-plated , Instead of plated buttons. The process is as follows:

1) Strip the coating to remove tin or tin-lead coating on outstanding contacts 2) Rinse with washing water 3) Wipe with abrasives 4) Activate and diffuse in 10% sulfuric acid 5) Plating on outstanding contacts Nickel thickness is 4 -5μm 6) Washing and demineralizing water 7) Gold soaking solution treatment 8) Gold plating 9) Washing 10) Drying

The second type: through-hole plating

There are many ways to establish a layer of electroplating layer that meets the requirements on the hole wall of the substrate drilled hole. This is called hole wall activation in industrial use. The commercial production process of its printed circuit requires multiple central storage tanks. The tank has its own control and maintenance requirements. Through-hole plating is a necessary subsequent manufacturing process of the drilling manufacturing process. When the drill bit drills through the copper foil and the substrate underneath, the heat generated melts the insulating synthetic resin that constitutes most of the substrate matrix, the molten resin and other drilling debris It accumulates around the hole and is coated on the newly exposed hole wall in the copper foil. In fact, this is harmful to the subsequent electroplating surface. The molten resin will also leave a layer of hot shaft on the hole wall of the substrate, which exhibits poor adhesion to most activators. This requires the development of a class of similar decontamination and etch-back chemistry skills.

A method that is more suitable for printed circuit board prototype manufacturing is to use a specially designed low-viscosity ink to form a high-adhesion, high-conductivity film on the inner wall of each through hole. In this way, there is no need to use multiple chemical treatment processes, only one use process, followed by thermal curing, can form a continuous film on the inner side of all the hole walls, and it can be directly electroplated without further processing. This ink is a resin-based substance that has a very strong adhesion and can be easily bonded to the walls of most thermally polished holes, thus eliminating the process of etchback.

The third type: reel linkage type selective plating

The pins and pins of electronic components, such as connectors, integrated circuits, transistors, and flexible printed circuits, are all selected for plating to obtain outstanding touch resistance and corrosion resistance. This kind of electroplating method can choose the technical method or the active method. It is very expensive to select and plate each pin individually, so it is necessary to choose batch welding. Generally, the two ends of the metal foil that is rolled to the required thickness are punched and cleaned by chemical or mechanical methods, and then there are selected options such as nickel, gold, silver, rhodium, button or tin-nickel alloy, copper-nickel alloy , Nickel-lead alloy, etc. for successive electroplating. When selecting the plating method, first coat a layer of resist film on the part of the metal copper foil board that does not need to be electroplated, and only conduct electroplating on the selected part of the copper foil.

The fourth type: brush plating

Another method of selecting plating is called "brush plating". It 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 it has no effect on other parts. Generally, rare metals are plated on selected parts of the printed circuit board, such as areas 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 required.

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