A PCBA is a complex assembly composed of multiple components that work together to realize specific electronic functions, and its main components can be divided into four categories: PCB substrate, electronic components, solder joints, and auxiliary materials, each of which plays an indispensable role in the normal operation of the PCBA. The PCB substrate is the core carrier of all components, usually made of copper-clad laminate (CCL) with different materials such as FR-4 (flame-retardant epoxy resin), aluminum-based, or flexible materials. The PCB provides mechanical support and electrical connection paths for components through its pre-designed circuit patterns, holes, and pads, and its quality directly affects the stability, heat dissipation, and service life of the entire PCBA.

Electronic components are the functional core of PCBA, which can be further divided into surface mount components (SMDs) and through-hole components (THTs) according to the mounting method. SMDs are widely used due to their small size, light weight, and high integration, including resistors (chip resistors, variable resistors), capacitors (chip capacitors, electrolytic capacitors), inductors, diodes, transistors, integrated circuits (ICs), and microcontrollers (MCUs). THTs, on the other hand, are mainly used for components that require higher mechanical strength or larger current carrying capacity, such as power connectors, terminals, relays, and fuses. Solder joints are the key connection parts between components and the PCB, formed by melting solder paste or solder wire during the soldering process, which ensure the electrical conductivity and mechanical stability of the connection. Auxiliary materials include solder paste, flux, solder wire, stencil paper, and adhesive, which are essential for the assembly process: solder paste is used for SMT soldering, flux removes oxide layers to improve solderability, and adhesive fixes components to prevent displacement during soldering.