There are four main electroplating methods in the circuit board: finger-row electroplating, through-hole electroplating, rolling wheel selective electroplating and brush electroplating.
Here is a brief introduction:
Finger row plating
Rare metals need to be plated on plate edge connectors, plate edge protruding contacts, or gold fingers to provide lower contact resistance and higher wear resistance. This technique is called finger row or protruding plating. Gold plating is often the inner layer of nickel plate edge connector protruding contact head, gold finger or plate edge protruding part using manual or automatic electroplating technology, the current contact plug or gold finger on the gold plating has been basking, lead, button replacement.
Finger-row electroplating process is as follows:
Remove tin or tin-lead coating from protruding contacts
Rinse with rinse water
Scrub with an abrasive
Activated in 10% sulfuric acid
The nickel plating thickness on the protruding contact is 4 to 5 microns
Clean and remove mineral water
Gold osmosis solution treatment
Gold plated
cleaning
drying
Through hole plating
There are many ways to establish a suitable electroplating layer on the hole wall of substrate drilling, which is called hole wall activation in industrial application, and the commercial production process of printed circuit requires multiple intermediate storage tanks, each of which has its own control and maintenance requirements. Hole drilling process of follow-up is necessary electroplating production process, when the drill through the copper foil and the substrate, the heat generated by the most to make plate substrate the insulation of the synthetic resin melt, the molten resin drilling and other debris piled up around the holes, coated in copper foil newly exposed the hole wall, in fact it is harmful to the subsequent plating surface. The melted resin will also leave a layer of heat axis on the hole wall of the substrate, which shows poor adhesion to most activators, requiring the development of a technology similar to stain removal and reerosion chemistry.
A more suitable way to prototype printed circuit boards is to use a specially designed low viscosity ink to form a highly adhesive, highly conductive film on the inner wall of each through-hole. This eliminates the need for multiple chemical processes and requires only one application step, followed by thermal curing, to form a continuous film coating on the inside of all pore walls, which can be electroplated without further treatment. The ink is a resin-based material that has a strong adhesion and can be easily adhered to most of the hole walls that are thermally polished, thus eliminating the reverse erosion step.
Roller tandem selective plating
Pins and pins of electronic components, such as connectors, integrated circuits, transistors and flexible printed circuits, are selectively plated to obtain good contact resistance and corrosion resistance. This electroplating method can be either manual or automatic. It is very expensive to select and plate each pin individually, so batch welding must be used. Usually, the two ends of the foil rolled to the desired thickness are blanched, cleaned by chemical or mechanical means, and then selectively electroplated in a continuous manner such as nickel, gold, silver, rhodium, button or tin-nickel alloy, copper-nickel alloy, nickel-lead alloy, etc. In the selection of the plating method, first in the metal copper foil plate does not need the plating of a layer of resistance film, only in the selected copper foil plating.
Brush plating
Another alternative plating method is called brush plating. It is an electrodeposition technique in which not all parts of the electroplating process are immersed in the electrolyte. In this electroplating technique, only a limited area is electroplated without any effect on the rest. In general, rare metals are plated on selected parts of a printed circuit board, such as areas such as the board edge connector. Brush plating is used more often in electronic assembly shop to repair discarded circuit boards. A special anode (a chemically inactive anode, such as graphite) is wrapped in a absorbent material (cotton swab), which is used to carry the plating solution to where it is needed.