used as a ground plane HASL or power plane, to achieve better signal integrity, higher signaling frequencies, and better power supply decoupling. In multilayer boards, layers of material are laminated together in an alternating sandwich: copper, substrate, copper, substrate, copper, etc.; each layer of copper is etched and
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 shorts, HASL the coating is called a solder mask. Soldermask is generally green in color but can have different colors: green, red, blue,
on the other side. "SMD" components are soldered on the same side of the board. A board can use both methods for soldering components. Today PCBs with components mounted only through holes are now less common. Surface mount is used for components like transistors, HASL diodes,