PCB and PCBA: Boards, Traces, Pads and Vias

Learn the difference between a bare PCB and a PCBA, what traces, pads and vias do, and how surface-mount and through-hole connections differ.

A printed circuit board (PCB) provides mechanical support and electrical connections for electronic components. A bare PCB has its board structure and conductive features, before the components are mounted. A printed circuit board assembly (PCBA) is the board with components assembled onto it. Fabricating the board and assembling its components are different tasks. Eurocircuits definitions · Altium fabrication and assembly

PCB versus PCBA

In manufacturing discussions, distinguishing the bare board from the populated assembly makes the intended object clearer. PCB is also used informally for an assembled board, so the acronym alone can be ambiguous. PCA, meaning printed circuit assembly, is another name used for the populated object. Eurocircuits naming context

For example, a bare board can contain copper connections and mounting areas without the resistors or capacitors being fitted. Adding those components produces an assembly. The board and the component set therefore describe different parts of the product. Altium board and assembly explanation

What are traces, pads and vias?

These are conductive features of the PCB, rather than names for the mounted electronic components.

Feature	Basic role
Trace	Routes a connection along a layer
Pad	Provides a connection area
Via	Connects different conductor layers

A trace, also called a track in PCB routing, is a patterned conductive path. It connects features such as pads and vias along a conductor layer. A pad is a conductive area used as a connection point; component pads provide the interface between a component’s terminals and board routing. Altium trace terminology · Altium track and pad objects

A via makes an electrical connection between conductor layers. A plated hole is a common implementation. Its defining task is the interlayer connection, whereas a component pad provides a terminal connection. A via does not necessarily extend from the top to the bottom of the board. Altium via terminology · Altium interlayer connections

Conductors, insulation and solder mask

Conventional PCBs combine copper conductors with electrically insulating material. Conductive features carry the circuit connections; insulation separates them where a connection is not intended. This overview does not prescribe one material or stack of layers for every PCB technology. Altium conventional board construction

Solder mask is a protective coating over selected board areas. Its functions include protecting copper features and helping prevent unintended solder connections during assembly. It is distinct from the copper routing itself. Altium solder-mask terminology · Würth Elektronik protection explanation

Surface-mount and through-hole connections

With surface-mount technology (SMT), component terminals connect to pads on the board surface. In through-hole mounting, component leads enter holes and are soldered to their board connections. These describe component mounting arrangements, rather than alternative names for PCB and PCBA. Altium mounting terminology

The term PCBA identifies an assembled object; it does not by itself state which tests have been performed or passed. Testing is a separate activity following assembly in the manufacturing sequence described by Altium. Altium assembly and testing

For the mounted devices themselves, see resistor basics and capacitor basics. Explore related board concepts in PCB & PCBA.