What Is a PCB? Layers, Materials, Types and How to Order

A board’s green surface is typically solder mask, not the insulating core itself. A copper pad may appear gold or silver because a surface finish protects the exposed copper before assembly.

A single-sided board has one copper circuit layer; a double-sided board has copper on both sides, often interconnected through plated holes. A multilayer board includes internal copper layers as well. Layer count refers to conductive layers, not the number of visible colors or the number of component sides.

More layers can make routing and return-path control easier, but they add stackup decisions and cost. An internal plane may distribute power or provide a signal reference. Choose layer count from routing density, noise, power and mechanical requirements rather than assuming that more layers always means a better board.

Rigid FR-4 boards are common for general electronics. FR-4 describes a family of glass-reinforced epoxy material systems, not one universal electrical or thermal specification. High-frequency or demanding thermal applications may require a different laminate or construction.

A flex PCB uses a flexible dielectric structure; rigid-flex combines rigid regions with flex sections. Metal-core constructions provide a different thermal path for some applications. Material selection must consider temperature, dielectric properties, mechanical use, assembly and availability—not just a familiar material name.

A schematic defines electrical intent. Layout assigns component locations and turns connections into copper geometry within a stackup. Manufacturing output then defines copper, mask, drills, outline and fabrication requirements. The fabrication process produces the bare board.

Assembly adds components and solder joints, producing a PCBA. Programming, functional testing, enclosure integration and product approval are additional activities when required. The PCB versus PCBA comparison explains how to keep those scopes clear in a quote.

At minimum, prepare the manufacturing files, drill data, outline, layer order, material requirement, finished thickness, copper, finish, quantity and revision. Include impedance, via treatment, special dimensions or inspection requirements when they apply. A screenshot of the layout is useful for discussion but is not a manufacturing package.

For an assembled prototype, also supply a BOM with manufacturer part numbers, placement data, assembly drawing, polarity and DNP notes. Ask the supplier to resolve missing requirements before tooling. Use the Gerber preparation checklist and start with a prototype sized to answer the design questions you need to test.