On the printed circuit board, copper is used to interconnect the components on the substrate. Although it is a good conductor material for forming the conductive path pattern of the printed circuit board, if it is exposed to the air for a long time, it will also It is easy to tarnish due to oxidation and lose weldability due to corrosion. Therefore, copper traces, vias, and plated-through holes must be protected using a variety of techniques, including organic paint, oxide films, and electroplating.

Organic paint is very simple to apply, but it is not suitable for long-term use due to changes in its concentration, composition and curing cycle, and it can even lead to unpredictable deviations in weldability. The oxide film protects the circuit from corrosion, but it does not maintain solderability. Electroplating or metallization processes are standard operations to ensure solderability and protect circuits from corrosion and play an important role in the manufacture of single-sided, double-sided and multi-layer printed circuit boards. In particular, plating a layer of solderable metal on the trace has become a standard practice to provide a solderable protective layer for copper traces.

The interconnection of various modules in electronic equipment often requires the use of printed circuit board headers with spring contacts and printed circuit boards with connecting contacts of matching design. These contacts should have high wear resistance and low contact resistance, which requires a layer of rare metal plating on them, the most commonly used metal is gold. In addition, other coating metals can also be used on the printed lines, such as tin plating, plated ballast, and sometimes copper plating in some printed line areas.

Another coating on copper traces is an organic, usually a solder mask, which is screen printed with a thin epoxy film where soldering is not required. This process of coating with an organic flux does not require electron exchange, and when the board is immersed in an electroless plating solution, a nitrogen-tolerant compound can adhere to the exposed metal surface without being absorbed by the substrate .

The technical sophistication required for electronics and the stringent requirements for environmental and safety adaptability have led to significant advances in electroplating practices, evident in the fabrication of high-complexity, high-resolution, multi-substrate technologies. In electroplating, electroplating technology has reached a high s level.

There are two standard methods for growing metal build-up layers on circuit board traces and vias: wire plating and full board copper plating.

1. Circuit plating

The process accepts copper layer generation and etch resist metal plating only where circuit patterns and vias are designed. During line plating, the increased width on each side of the lines and pads is roughly equivalent to the increased thickness of the plated surface, so a margin on the original negative is required.

In circuit electroplating, most of the copper surfaces are basically masked with resist, and electroplating is only performed where there are circuit patterns such as lines and pads. Due to the reduced surface area to be plated, the required supply current capacity is often greatly reduced, and the negative negative is often Can be made with relatively inexpensive laser printers or drawing pens. The anode consumes less copper in line plating and less copper needs to be removed during the etching process, thus reducing the cost of analysis and maintenance of the electrolyzer. The disadvantage of this technique is that the circuit pattern needs to be plated with tin/lead or an electrophoresis resist material before etching, which is removed before the solder resist is applied. This adds complexity and an additional wet chemical solution processing process.

2. Full board copper plating

The entire surface area and drilled holes are copper plated in this process, some resist is poured over the unwanted copper surfaces, and then the etch resist metal is plated. Even for a medium-sized printed circuit board, this requires a power source capable of delivering a considerable amount of current to produce an easy-to-clean, smooth, bright copper surface for subsequent processing. If you don't have a photoplotter, you'll need to use a negative film to expose the circuit graphics, making it the more common contrast reversal dry film photoresist. Etching a fully copper-plated circuit board will remove most of the material plated on the circuit board again. Due to the increase in the copper carrier liquid in the etchant, the burden of additional corrosion on the anode is greatly increased.

The electroplating process of PCB boards can also provide metal plating with high electrical conductivity, good solderability, high mechanical strength and ductility required to withstand component terminal paneling and copper filling into plated through holes from the board surface .