The printed circuit board (PCB) assembly process begins with the most fundamental unit of the PCB: the substrate. The substrate consists of four distinct layers of material, each playing a critical role in enabling the final functionality of the printed circuit board.
Substrate: This constitutes the foundational material of the PCB, providing the board with its structural rigidity.
Copper: A thin layer of conductive copper foil is applied to every functional surface of the PCB. For single-sided PCBs, the copper foil is present on one side; for double-sided PCBs, it is distributed across both sides. These layers collectively form the copper traces.
Solder Mask: Situated atop the copper layer is the solder mask, which gives every PCB its signature green appearance. The primary function of the solder mask is to insulate the copper traces from conductive materials, thereby preventing short circuits. In other words, the solder mask acts as the medium that secures all components in their designated positions via solder. The openings within the solder mask allow solder to pass through and connect components to the board; this is a critical stage in the PCB assembly process, as it prevents unintended soldering on unnecessary areas, effectively averting short-circuiting issues.
Silkscreen: The white silkscreen layer is the final layer applied to the PCB. This layer adds markings-in the form of characters and symbols-to the board, serving to identify the function of each individual component on the PCB.
