inner layers of copper alternating with pcb insulating layers). Among the multi-layer PCBs, the most common are the four-layer ones. The four-layer board has many more routing options in the internal layers compared to the two-layer board, and often part of the internal layers are used as a
for passing connections between layers of copper as solid conductive areas for electromagnetic shielding or other purposes. Each pcb of the conductive layers is designed with copper tracks (similar to wires on a flat surface) that provide electrical connections on that conductive layer. Another manufacturing process adds plated or metallized
copper from corrosion and reduces the chances of solder shorting between traces or unwanted electrical contact with possible loose wires. For its function of helping to prevent solder pcb shorts, the coating is called a solder mask. Soldermask is generally green in color but can have