The purpose of copper plating
Deposit a thin layer of copper on the entire printed circuit board (especially on the hole wall) for subsequent hole plating, to make the hole metalized (with copper inside for conductivity), and achieve interlayer conductance.
As for the sub-processes of copper plating, there are usually three
Pre-plating treatment (grinding the board)
Before copper plating, the China PCB board is ground to remove burrs, scratches, and dust from the surface and inside the holes.
Copper plating
Using the board material itself to catalyze the oxidation-reduction reaction, a thin layer of copper is deposited on the holes and surface of the printed circuit board, acting as a conducting lead for subsequent plating to achieve hole metallization.
Backlight level testing
By making hole wall sections and observing them with a metallographic microscope, the coverage of deposited copper on the hole walls is confirmed. (Note: Backlight level is generally divided into 10 levels. The higher the level, the better the coverage of deposited copper on the hole walls. The industry standard is usually ≥8.5 levels.)
The purpose of this PCB copper plate process is mainly for inspection, which will not affect the quality of the product. However, since this inspection is very important, it is often separated from the production line and listed as one of the daily tasks in the laboratory. Therefore, if you find that some PCB manufacturers do not have corresponding inspection stations around their copper plating lines, don't be surprised. It is probably done in the laboratory.
In addition, copper plating is not the only process that can be used as a preparation for plating. Black hole and black mask can also be used. As for the specific differences among the three.
