The most common substrate/substrate material for PCBs is FR-4.FR-4 based PCBs are commonly found in many electronic devices and their manufacturing is common. Single-sided and double-sided PCBs are easy to manufacture compared to multilayer PCBs.
FR-4
PCBs are made of glass fibers and epoxy resin combined with laminated copper cladding. Some prime examples of complex multilayer (up to 12 layers) PCBs are computer graphics cards, motherboards, microprocessor boards, FPGAs, CPLDs, hard disk drives, RF
LNAs, satcom antenna feeds, switched-mode power supplies, Android phones, and more. There are also many examples where simple single and double layer PCBs are used, such as CRT TVs, analog oscilloscopes, handheld calculators, computer mice, FM radio circuits.
Applications of PCB:
1. Medical Devices:
Today's advancement in medical science is entirely due to the rapid growth of the electronics industry. Most of the medical devices such as pH meters, heartbeat sensors, temperature measurement, ECG/EEG machines, MR*** vibration imagers, X-rays, CT scans, blood pressure machines, glucose level measurement devices, incubators, microbiology devices and many others are individually based on electronic PCBs. these PCBs are usually dense and have small form factors. Denser means smaller SMT components placed in smaller sized PCBs. These medical devices are made smaller, portable, lightweight and easy to maneuver.
2. Industrial equipment.
PCBs are also widely used in manufacturing, factories, and looming factories. These industries have high-power machinery and equipment that are driven by circuits that run at high power and require high current. For this reason, a thick layer of copper is laminated on the PCBs, which, unlike complex electronic PCBs, draw up to 100 amps of current in these high-power PCBs. This is particularly important in applications such as arc welding, large servo motor drives, lead-acid battery chargers, the military industry, and garment cotton looming machines.
3. Lighting.
When it comes to lighting, the world is moving towards energy efficient solutions. These halogen bulbs are now rarely found but now we see LED lights and high intensity LEDs around.These small LEDs provide high brightness light and are mounted on PCBs based on aluminum substrates. Aluminum has the property of absorbing heat and dissipating it in the air. Hence, due to high power, these aluminum PCBs are commonly used in LED light circuits for medium and high power LED circuits.
4. automotive and aerospace industries.
Another application of PCBs is in the automotive and aerospace industry. A common factor here is the reverberation that occurs when an airplane or car is in motion. Therefore, to cater to these high force vibrations, PCBs become flexible. Hence a type of PCB called Flex
PCB is used. flexible PCBs can withstand high vibrations and are light in weight, which reduces the total weight of the spacecraft. These flexible PCBs can also be adjusted in tight spaces which is also a great advantage. These flexible PCBs are used as connectors, interfaces and can be assembled in compact spaces such as behind panels, under instrument panels etc. A combination of rigid and flexible PCBs is also used.
Types of PCBs:
Printed circuit boards (PCBs) are categorized into 8 major groups. They are
Single Sided PCB:
Single sided PCBs have components mounted on one side only and the other side is used for copper wires. A thin layer of copper foil is applied to the RF-4 substrate on one side, and then a solder mask is applied to provide insulation. Finally, screen printing is applied to provide component marking information such as C1, R1, etc. on the PCB. These single layer PCBs are very easy to design and manufacture on a large scale, have a high market demand and are cheap to buy. Very commonly used in household products such as juicers/blenders, rechargeable fans, calculators, small battery chargers, toys, TV remote controls etc.
Double Layer PCB:
Double Sided PCB is applying copper layer of PCB on both sides of the board. Holes are drilled and THT components with leads are mounted in these holes. These holes connect one side component to the other through copper tracks. The component leads are passed through the holes, the excess leads are cut by a cutter and the leads are soldered to the holes. This is all done manually. There can also be SMT components as well as THT components for 2 layer PCBs.
SMT components do not require holes, but pads are made on the PCB and the SMT parts are fixed to the PCB by reflow soldering.
SMT components take up very little space on the PCB, so more free space can be used on the board for more functions. Double-sided PCBs are used for power supplies, amplifiers, DC motor drivers, instrumentation circuits, and more.
Multilayer PCBs:
Multilayer PCBs are made of multiple layers of 2-layer PCBs sandwiched between dielectric insulation to ensure that neither the board nor the components are damaged by overheating. Multilayer PCBs come in a variety of form factors and different layers, from 4-layer PCBs to 12-layer PCBs. the more layers, the more complex the circuit, the more complex the PCB layout design.
Multilayer PCBs typically have separate ground layers, power supply layers, high-speed signal layers, signal integrity considerations, and thermal management. Common applications are military requirements, aerospace and aerospace electronics, satellite communications, navigation electronics, GPS tracking, radar, digital signal processing and image processing.
Rigid PCB:
All of the PCB types discussed above fall into the rigid PCB category. Rigid PCBs have solid substrates such as FR-4, Rogers, phenolic and epoxy resins. These boards do not bend and twist, but can maintain their shape for years up to 10 or 20 years. This is why many electronic devices have a long lifespan because of the rigidity, sturdiness and stiffness of rigid PCBs. Computers and laptops have rigid PCB's and many TV's, LCD's, LED TV's commonly used in homes are made from rigid PCB's. All the above single sided, double sided and multilayer PCB applications are also suitable for rigid PCBs.
Flex PCB:
Flexible PCBs or Flex PCBs are not rigid but they are flexible and can be bent easily. They are flexible and have high heat resistance and excellent electrical characteristics. The substrate material for Flex PCBs depends on performance and cost.
Common substrate materials for Flex PCBs are polyamide (PI) film, polyester (PET) film, PEN, and PTFE.
Flex
PCBs are more costly to manufacture than just rigid PCBs. they can be folded or wrapped around corners. They take up less space than their rigid PCB counterparts. They are lightweight but have very low tear strength.
Rigid-Flex PCBs:
The combination of rigid and flexible PCBs is important in many space and weight constrained applications. For example, in cameras, the circuitry is complex, but a combination of rigid and flexible PCBs will reduce the number of parts and minimize PCB size. The wiring of two PCBs can also be combined on a single PCB. Common applications are digital cameras, cell phones, automobiles, laptops, and those devices with moving parts
High-speed PCBs:
High-speed or high-frequency PCBs are PCBs used in applications involving signal communication at frequencies higher than 1 GHz. in this case, signal integrity issues come into play. Materials for high frequency PCB substrates should be carefully selected to meet design requirements.
Commonly used materials are polyphenylene (PPO) and polytetrafluoroethylene. It has stable dielectric constant and small dielectric loss. They have low water absorption but high cost.
Many other dielectric materials have variable dielectric constants, resulting in impedance variations that distort harmonics and digital signal loss as well as loss of signal integrity
Aluminum PCB:
Aluminum-based PCBs substrate materials have the property of efficiently dissipating thermal energy. Due to low thermal resistance, aluminum-based PCBs cool more efficiently than their copper-based counterparts. It dissipates heat in the air as well as in the thermal junction areas of the PCB.
Many LED light circuits with high-brightness LEDs are made from aluminum-backed PCBs.
Aluminum is an abundant metal and its mining is inexpensive, so PCB costs are low. Aluminum is recyclable and non-toxic, so it is environmentally friendly. Aluminum is rugged and therefore reduces damage during manufacturing, shipping and assembly
All of these properties make aluminum-based PCBs beneficial for high-current applications such as motor controllers, heavy-duty battery chargers and high-brightness LED lights.
Conclusion:
In recent years, PCBs have evolved from simple to single-layer versions suitable for more complex systems, such as high-frequency Teflon PCBs.
PCBs are now found in virtually every area of modern technology and evolving science. Microbiology, microelectronics, nanoscience and technology, aerospace industry, military, avionics, robotics, artificial intelligence and other fields are all based on various forms of printed circuit boards (PCBs) as building blocks.