There are four main types of electroplating methods in the circuit board: finger-plated electroplating, through-hole electroplating, reel-selective plating, and brush plating.
Here’s a brief introduction:
1. Finger-plated electroplating
Rare metals need to be plated on board edge connectors, board edge bumps or gold fingers to provide lower contact resistance and higher wear resistance. This technique is known as finger-plated or protruding partial plating. Gold is often plated on the inner side of the plate-side connector protruding from nickel. The gold finger or the edge of the plate is manually or automatically plated. The gold plating on the contact plug or gold finger has been plated and plated. Replace with a plated button.
The process of finger-plating plating is as follows:
Stripping the coating to remove tin or tin-lead coating on the protruding contacts
- Washing water rinse
- Scrub scrub with abrasive
- Activation is not in 10% sulfuric acid
- Nickel plating on the protruding contacts is 4-5μm
- Cleaning and removing mineral water
- Gold permeation solution treatment
- Gold plating
2. Through-hole electroplating
There are a number of ways to create a desirable layer of plating on the walls of the substrate borehole. This is known as hole wall activation in industrial applications. The printed circuit commercial production process requires multiple intermediate tanks, each of which is stored. The tank has its own control and maintenance requirements. Through-hole plating is a necessary PCB manufacturing process for the drilling process. When the drill bit is drilled through the copper foil and the substrate below it, the heat generated causes the insulating synthetic resin constituting most of the substrate to melt, the molten resin and other drilled fragments. It builds up around the holes and is applied to the newly exposed walls of the copper foil, which is in fact detrimental to the subsequent plating surface. The molten resin also leaves a hot layer on the walls of the substrate, which exhibits poor adhesion to most activators, which requires the development of a technique similar to stain removal and etch-back chemistry.
One method that is more suitable for prototype PCB production is to use a specially designed low viscosity ink to form a highly adherent, highly conductive film on the inner wall of each via. This eliminates the need for multiple chemical treatments, requires only one application step, followed by thermal curing to form a continuous film on the inside of all the walls of the hole, which can be directly electroplated without further processing. This ink is a resin-based material that has a very strong adhesion and can be easily bonded to most thermally polished holes, thus eliminating the etch-back step.
3. Reel-selective plating
Pins and pins for electronic components, such as connectors, integrated circuits, transistors, and flexible printed circuits, are selectively plated for good contact resistance and corrosion resistance. This plating method can be either manual or automatic, and it is very expensive to individually select each of the pins, so batch welding must be used. Usually, the ends of the metal foil which are flattened to the required thickness are die-cut, chemically or mechanically cleaned, and then selectively used like nickel, gold, silver, iridium, button or tin-nickel alloy, copper-nickel alloy Continuous plating of nickel-lead alloys, etc. In the selective plating method, first, a portion of the metal copper foil plate which is not required to be plated is coated with a resist film, and plating is performed only on the selected copper foil portion.
4. Brush plating
Another method of selecting plating is called “brush plating”. It is an electrodeposition technique in which not all parts are immersed in the electrolyte during the plating process. In this plating technique, only a limited area is 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 edge connectors. Brush plating is used more often in the electronics assembly shop to repair waste boards. A special anode (chemically reactive anode, such as graphite) is wrapped in an absorbent material (cotton stick) that is used to bring the plating solution to where it is needed.