A printed circuit board (PCB), also known as a printed wiring board (PWB), is a medium used to connect electronic components in a circuit. It is made up of conductive and insulating layers that are laminated together in a sandwich structure. The conductive layers are designed with a pattern of traces, planes, and other features, similar to wires on a flat surface, which are etched from one or more sheet layers of copper laminated onto and/or between sheet layers of a non-conductive substrate. Electrical components are fixed to conductive pads on the outer layers in a shape designed to accept the component's terminals, generally by soldering, to both electrically connect and mechanically fasten them to the board. Another manufacturing process adds vias, which are plated-through holes that allow interconnections between layers.
Paul Eisler, an Austrian engineer, invented the printed circuit while working in the UK around 1936 as part of a radio set. In 1941, a multi-layer printed circuit was used in German magnetic influence naval mines. The USA began to use the technology on a large scale around 1943 to make proximity fuzes for use in World War II. These fuzes required an electronic circuit that could withstand being fired from a gun and could be produced in quantity. The Centralab Division of Globe Union submitted a proposal that met the requirements, which involved screenprinting a ceramic plate with metallic paint for conductors and carbon material for resistors, with ceramic disc capacitors and subminiature vacuum tubes soldered in place. The technique proved viable, and the resulting patent on the process, which was classified by the U.S. Army, was assigned to Globe Union. This invention also represents a step in the development of integrated circuit technology, as not only wiring but also passive components were fabricated on the ceramic substrate. Harry W. Rubinstein was awarded the Cledo Brunetti Award by the Institute of Electrical and Electronics Engineers (IEEE) in 1984 for his early key contributions to the development of printed components and conductors on a common insulating substrate. Rubinstein was also honored in 1984 by his alma mater, the University of Wisconsin-Madison, for his innovations in the technology of printed electronic circuits and the fabrication of capacitors.
A basic printed circuit board (PCB) is made up of an insulating material that is flat and a layer of copper foil that is laminated onto the substrate. The copper is divided into separate conducting lines, which are called tracks or circuit traces, as well as pads for connections, vias to pass connections between layers of copper, and features such as solid conductive areas for electromagnetic shielding or other purposes. The tracks act as wires that are fixed in place and are insulated from each other by air and the board substrate material. The surface of a PCB may be coated to protect the copper from corrosion and to reduce the chances of solder shorts between traces or undesired electrical contact with stray bare wires. This coating is called solder resist or solder mask because it helps to prevent solder shorts.
Components that are "through hole" are mounted by passing their wire leads through the board and soldering them to traces on the opposite side. On the other hand, "surface mount" components are attached by their leads to copper traces on the same side of the board. It is possible for a board to use both methods for mounting components. PCBs that exclusively use through-hole mounted components are now rare. Surface mounting is commonly used for transistors, diodes, IC chips, resistors, and capacitors. However, through-hole mounting may still be used for some larger components such as electrolytic capacitors and connectors.
Resistors are among the most frequently used components in printed circuit boards (PCBs) and are likely the easiest to comprehend. Their purpose is to impede the flow of current by converting electrical energy into heat. They are available in various types, made from a variety of materials, but the most common type of resistor known to hobbyists is the "axial" style resistor, which has leads on both ends and colored rings inscribed on the body.
Capacitors are one of the most commonly found components on a PCB, second only to resistors in terms of prevalence. Their primary function is to temporarily store electric charge and release it when additional power is required elsewhere in the circuit. This is typically accomplished by collecting opposite charges on two conductive layers that are separated by an insulating or dielectric material. Capacitors are often classified based on the conductor or dielectric material used, resulting in a wide range of types with varying characteristics, from high-capacitance electrolytic capacitors to diverse polymer capacitors and more stable ceramic disc capacitors. While some may resemble axial resistors in appearance, the classic capacitor is a radial style with two leads protruding from the same end.
Inductors belong to the family of linear passive components, which also includes resistors and capacitors. Similar to capacitors, they have the ability to store energy. However, instead of storing electrostatic energy, inductors store energy in the form of a magnetic field that is generated when current flows through them. The most basic form of an inductor is a coil of wire, and the strength of the magnetic field and inductance increases with the number of windings. Inductors are often wrapped around a magnetic core of various shapes to amplify the magnetic field and store more energy.
Inductors are commonly used to filter out or block specific signals, such as blocking interference in radio equipment. They can also be used in conjunction with capacitors to manipulate AC signals in switched mode power supplies.
Potentiometers are a type of variable resistor that come in both rotary and linear forms. In a rotary potentiometer, the resistance is adjusted by rotating the knob, which moves the slider contact over a semi-circular resistor. This type of potentiometer is commonly used in volume controllers for radios, where it controls the amount of current sent to the amplifier. Linear potentiometers work in a similar way, but the resistance is adjusted by moving the slider contact linearly along the resistor. These potentiometers are particularly useful when precise adjustments are needed in the field.
Transformers serve the purpose of transferring electrical energy from one circuit to another, while either increasing or decreasing the voltage. This process is commonly referred to as voltage transformation. Similar to inductors, transformers are composed of a soft iron core with at least two wire coils wound around it. The primary coil is used for the source circuit, while the secondary coil is used for the circuit where energy is being transferred to. Large industrial transformers can often be seen on telegraph poles, where they step-down the voltage from overhead transmission lines, which typically carry several hundred thousand volts, to the few hundred volts required for household use.
A diode is a device that allows current to flow in only one direction, similar to a one-way street. It achieves this by having zero resistance in one direction and high resistance in the other. This property can be utilized to prevent current from flowing in the wrong direction, which could result in damage. The light-emitting diode (LED) is the most popular diode among hobbyists. As the name suggests, it emits light, but it is also a diode, so it is crucial to ensure the correct orientation when soldering, or else the LED will not light up.
Transistors are widely regarded as the fundamental building blocks of modern electronics, with a single IC chip containing several billions of them. Essentially, transistors function as amplifiers and electronic switches, and come in various types, with the bipolar transistor being the most prevalent. These can be further classified into NPN and PNP versions, each having three pins - the base, collector, and emitter. In the case of an NPN type, a small current flowing from the base to the emitter activates another circuit, causing a much larger current to flow from the collector to the emitter. The directions are reversed for a PNP transistor. Field effect transistors, or FETs, are another type of transistor that use an electric field to activate the other circuit.
Silicon Controlled Rectifiers (SCR), also referred to as thyristors, share similarities with transistors and diodes. Essentially, they are composed of two transistors working in tandem and possess three leads. However, they differ in that they consist of four silicon layers instead of three and are solely designed to function as switches, not amplifiers. An important distinction is that only a single pulse is necessary to activate the switch, unlike a single transistor that requires a continuous application of current. As a result, SCR is better suited for switching larger amounts of power.
Integrated circuits, commonly referred to as ICs, are circuits and components that have been miniaturized and placed onto semiconductor wafers. The ability to fit a large number of components onto a single chip has led to the development of calculators, smartphones, and even supercomputers. Typically, ICs serve as the central processing unit of a larger circuit. They are often encased in black plastic housing, which can vary in shape and size and may have visible contacts, such as leads extending from the body or contact pads located directly underneath, as seen in BGA chips.
Crystal oscillators are widely used in circuits that require precise and stable timing elements. They generate a periodic electronic signal by causing a piezoelectric material, known as the crystal, to oscillate. Each crystal oscillator is designed to vibrate at a specific frequency and is more stable, cost-effective, and compact compared to other timing methods. As a result, they are frequently used as precise timers for microcontrollers and are commonly found in quartz wristwatches.
The switch is a fundamental component that is often overlooked, but it serves a crucial role in controlling the flow of current in a circuit. It achieves this by switching between an open or closed circuit, and comes in various physical forms such as slider, rotary, push button, lever, toggle, key switches, and more.
Similarly, a relay is an electromagnetic switch that operates through a solenoid. When current flows through the solenoid, it becomes a temporary magnet and activates the relay. Relays function as switches and can also amplify small currents to larger ones.
Sensors are devices designed to detect changes in environmental conditions and produce an electrical signal that corresponds to the detected change. This signal is then transmitted to other electronic components in the circuit. Essentially, sensors are transducers that convert energy from a physical phenomenon into electrical energy. They can take on many forms, ranging from resistors in a resistance temperature detector (RTD) to LEDs that detect infrared signals, as seen in television remotes. There is a wide range of sensors available for detecting various environmental stimuli, such as humidity, light, air quality, touch, sound, moisture, and motion.
Now that you know some basic electronic components of Circuit Board, you can start exploring the world of electronics with confidence. Understanding Circuit Board Components is essential for anyone interested in building or repairing electronic devices. By knowing the function of each component, you can troubleshoot problems and design circuits that meet your specific needs.
Whether you're a hobbyist or a professional, Circuit Board Components are the building blocks of all electronic devices. From resistors and capacitors to transistors and diodes, each component plays a crucial role in the overall function of the circuit. By mastering the basics of Circuit Board Components, you can take your electronics skills to the next level and create innovative and exciting projects.
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