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Four special plating methods in circuit board plating

The first, finger plating

Rare metals often need to be plated on board edge connectors, board edge contacts or gold fingers to provide lower contact resistance and higher wear resistance. This technique is called finger row plating or bump plating. Gold is usually plated on the protruding contacts of the board edge connector where the inner layer is nickel-plated. The gold finger or the protruding part of the board is manually or automatically plated. The gold plating on the contact plug or gold finger has been plated and lead-plated. , plating button instead. The process is as follows:

1) Strip coating to remove tin or tin-lead coating on protruding contacts

2) Washing water rinsing

3) Scrubbing with abrasives

4) The activation is not in the 10% sulfuric acid

5) Nickel plating thickness 4 - 5μm on protruding contacts

6) Cleaning to remove mineral water

7) Gold penetration solution treatment

8) Gold plating

9) Cleaning

10) Drying

Second, through-hole plating There are several ways to create a layer of plating that meets requirements on the walls of a hole drilled in a substrate. This is known as hole wall activation in industrial applications. The commercial production process of a printed circuit requires multiple intermediate storage tanks. Slots have their own control and maintenance requirements. Through hole electroplating is a necessary follow-up process for 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's substrate, melts the resin, and other borehole fragments. Accumulation around the holes, applied to newly exposed hole walls in the copper foil, is actually detrimental to subsequent plating surfaces. The molten resin also leaves a thermal axis on the walls of the substrate, which exhibits poor adhesion to most activators. This requires the development of a class of techniques similar to stain removal and etchback chemistry. One method that is more suitable for the prototyping of printed circuit boards is to use a specially designed low-viscosity ink to form a high-adhesion, high-conductivity coating on the inner wall of each through-hole. This eliminates the need for multiple chemical treatments and requires only one application step, followed by thermal curing to form a continuous coating on the inside of all pore walls, which can be plated directly without further treatment. This type of ink is a resin-based material that has a very strong tack and can be easily bonded to most thermally polished cell walls, eliminating the step of etch back.
The third type, reel-to-roller type selection plating Pins and pins of electronic components, such as connectors, integrated circuits, transistors, and flexible printed circuits, are all selected for good contact resistance and corrosion resistance. This electroplating method can be carried out by hand or automatically. Selective plating of each pin individually is very expensive, so batch welding must be used. Usually, both ends of a metal foil having a desired thickness are punched out, cleaned chemically or mechanically, and then selectively used like nickel, gold, silver, tantalum, button or tin-nickel alloy, copper-nickel alloy. Continuous plating of nickel-lead alloys, etc. In the electroplating method of selective plating, first, a portion of the resist film is coated on the portion of the copper foil plate that is not to be electroplated, and only the selected portion of the copper foil is electroplated.

Fourth, brush plating Another method of selective plating is called "brush plating." It is an electrodeposition technique and not all parts are immersed in the electrolyte during plating. In this electroplating technique, only limited areas are plated without any effect on the rest. Typically, rare metals are plated on selected portions of the printed circuit board, such as areas such as board edge connectors. Brush plating is used more often in the repair of discarded circuit boards in electronics assembly shops. A special anode (chemically reactive anode, such as graphite) is wrapped in an absorbent material (cotton swab) and used to carry the plating solution to the place where plating is required.