PCBs

Printed circuit boards (PCBs) are rigid or flexible boards used to mechanically support and electrically connect electronic components. They consist of a non-conductive substrate with patterned copper conductors formed by etching or deposition. The substrate is typically fiberglass-reinforced epoxy resin (FR-4), though ceramic and polyimide materials are used for specialty boards. Copper thickness is often 1 oz/ft² (about 35 μm); boards can use heavier copper for higher current capacity. A soldermask insulates the copper traces, while a silkscreen layer provides component labels.

PCBs come in single-sided, double-sided, and multilayer configurations. Multilayer boards stack multiple copper-clad laminates separated by insulating prepregs to realize dense circuits. Design files are produced with electronic design automation (EDA) tools and drive the manufacturing steps, including drilling vias and applying finishes. Common board thicknesses range around 1.6 mm, with variations for flexible or high-density boards.

Manufacturing uses photolithography and chemical or laser processes to define traces, drills for through-holes and vias, plating, and lamination. Finishes such as HASL (hot-air solder leveling), ENIG (electroless nickel–immersion gold), and ENEPIG (electroless nickel–electroless palladium–immersion gold) protect copper and improve solderability. Components are mounted by through-hole or surface-mount technology; surface-mount parts are typically attached by solder reflow, while through-hole parts may be wave soldered.

PCBs enable a wide range of electronics, including computers, consumer devices, automotive systems, and medical equipment. Design considerations include signal integrity, power distribution, thermal management, and manufacturability. Standards and guidelines from IPC and related bodies govern design rules, tolerances, and testing. Environmental and regulatory aspects, such as RoHS and REACH, restrict hazardous substances and influence recycling and disposal.