PCB is used for permanently soldered circuits like small scale and large scale electronic accessories and gadgets production in different industries. The marketable courses or gadgets are always made with PCBs. PCB electronics component is an electrical or electronic device such as an inductor, resistor, capacitor, and IC etc., that processes the input electrical signal. Each component has a unique symbol that is maintained throughout from schematic drawing to PCB layout. The characters are made for electrical PCB assembly. The marks made for PCB layout are called component footprints that define the component’s to-the-scale shape and soldering point. The component symbols and component footprint may be of the same or different conditions.
The PCBs have conductive thin copper tracks on one side in single layer PCBs, or on both sides in double-layer boards, and on multiple layers embedded within the outermost two layers of the board. The tracks which are generally covered with masked coating propagate signals from one end to the other. Typically, for a single layer, double layer and multilayer PCB, the through-hole components are mounted on one side and soldered on the other side of the PCB. The SMT components are mounted and soldered on the same side of PCB. The component density over the multilayer PCBs is much higher than the single and double layer PCBs.
Generally, the PCB electronics components are categorised but not only limited to, following types.
Resistor: general-purpose fixed, single or multiturn variable, slider, temperature-dependent etc.
Switches: Push to ON, Push to off, rotary, toggle, limit etc.
Inductor: power supply inductors, high frequency and RF inductors, filter inductors etc.
Capacitor: polar and non-polar capacitors, high frequency, power supply etc.
Diode: General purpose power supply rectifier type, Zener, Schottky, transient voltage suppressor etc
Transistor: NPN and PNP BJT, N-channel and P-channel FETs, UJTs etc
ICs: Analog ICs like operational amplifiers and sensors, digital ICs like gates, microprocessors, comparators, memories, FPGAs and DSPs etc. FROM the PCB perspective, each has its unique symbol and pin names for drawing clarity.
Figure 1 shows the different resistor and capacitor footprints; figure 2 shows the 32-pin SMD IC schematic symbol and print, and figure 3 shows the placement of SMD package IC for soldering.
1: Different sizes and shapes of capacitor and resistor footprints.
2: IC footprint and schematic symbol
3: 8-pin SOIC footprint 3D PCB footprint model and soldering on PCB