Since the Industrial Revolution, printed circuit boards (PCBs) have been transforming the electronic industry. The role played by these devices is so big that it is almost impossible to think of any electronic without them. Owing to their indispensable part, the PCB industry is growing faster than projected.

This article provides every detail you should know about the different types of printed circuit boards.

What are the Different Types of Circuit Boards?

There are various types of PCBs, each with its unique design specifications, material types, and applications:

1. Single-layer PCB

A single-layer or single-layered board consists of one layer base material. One part of the material is treated with a thin layer of metal. Copper foil is the standard coating material because of its high electrical transmission properties. Once you treat a bare board with copper, you need to apply a protective solder mask, accompanied by the final silkscreen, to label your components.

Single-layer PCBs have their components soldered into one side, are easy to design and produce. These features make the prices of single-layer PCBs affordable when creating high-volume runs. Their cost-effective benefit makes them ideal for making calculators, digital cameras, radio talkies, stereo devices, printers, and power supplies.

2. Double-layer PCB

Double-layer or double-sided boards contain a base material with a small layer of the conductive substrate, like copper, smeared on both PCB sides. You need to drill holes through the board to link the components on both sides to each other.

Components in double-layered PCBs are connected using through-hole or surface mount technologies. In a through-hole connection, you insert leads/small wires into the drilled holes and solder the lead ends to their appropriate component.

On the other hand, the surface mount technology does not use wires. Instead, components are soldered directly into the board using a solder paste. This process allows devices to be mounted even in limited spaces, enabling the production of high-performing and miniaturized boards.

Double-layered circuits are popularly applied in use cases that require an average circuit complexity, like industrial controls, power supplies, instrumentation, HVAC systems, LED lighting, amplifiers, and vending machines.

3. Multilayered PCB

Multilayered boards have more than two layers. They are secured with a solder mask and stacked between insulation pieces to prevent excess heat from melting the components. There are several types of multilayered boards ranging from four to twelve layers.

The possibility of creating more than two PCB layers allows designers to create thick and complex designs to fit various application requirements. Multilayered PCBs are mostly used in file servers, data storage, GPS devices, satellite equipment, weather forecasting equipment, and medical machines.

4. Rigid PCB

Rigid circuits consist of solid materials that enable them to maintain their original shapes even in intense vibrations and high temperatures. These boards are widely applied in the computer world to create motherboards. A motherboard is basically a multilayered circuit that distributes electric current and signals from the source to the various computer parts, facilitating the functioning of the computer.

Out of all the printed circuit boards, rigid PCBs are the most produced. This is because they can be applied in almost every application that requires a circuit board to maintain its original shape. Rigid boards can be anything from a single PCB to a twelve-layer board – they can assume single-layer, double-layer, or multi-layer designs.

5. Flexible PCB

Unlike rigid boards made of stable substrates like fiberglass, flex PCBs are made of substrates that can flex and move efficiently, like plastics. Like their counterparts, flex PCBs can assume single, double, or multilayered designs. Since they are printed on flexible substrates, their manufacturing cost is a bit high.

Despite the cost aspect, flexible boards provide many benefits over rigid PCBs because of their elastic property. This implies that you can fold them over edges and wrap them around corners easily. Though this flexibility comes with a cost, you can apply just one flex PCB in applications that require several rigid PCBs.

Besides, you use flex circuits in applications that experience harsh environmental conditions. You can design flexible boards using waterproof, corrosion, and heat-resistant materials to meet demanding environmental conditions.

6. Rigid-Flex PCB

Rigid-flex PCB integrates rigid and flexible materials. They include several layers of flexible boards stacked on rigid board layers. These PCBs have unique benefits that you cannot find in rigid and flexible PCBs. For example, they contain fewer components than rigid or flex PCBs since they integrate mounting options of both boards. The integration of a flex PCB with a rigid PCB also creates a streamlined design, minimizing the board’s size and weight further.

Flex-rigid circuits are ideal for applications that factor in space and weight factors, like smartphones, wearables, automobiles, and pacemakers.

7. High-Frequency PCB

A High-frequency circuit denotes the overall board design instead of a board construction like the other types we have described earlier. These PCBs are designed to conduct signals of more than one gigahertz.

High-frequency boards mostly contain FR4-grade glass-reinforced epoxy laminate, polyphenylene oxide (PPO) resin, and Teflon. However, Teflon is a bit expensive because of its low and stable Dk value, minimal dielectric loss, and low-moisture absorption capacity.

You must factor in various factors when designing high-frequency circuits, like the Dk value, dissipation loss, and dielectric thickness. The DK value of the substrate is the essential factor to remember. Substrates with high chances for alteration of Dk values often experience impedance changes, affecting the harmonics that constitute electrical signals, resulting in low signal integrity.

The other things you should remember when selecting PCBs and connector types in high-frequency boards are:

• Dielectric loss (DF): It influences the integrity of signals. A small DF value results in minimal signal wastage.

• Thermal expansion: If the heat expansion rates of the PCB substrates do not match, the stacked materials will separate from each other because of temperature changes.

• Water absorption: High amounts of moisture or water intake hinder a board’s DK and DF properties, especially if you are using it in humid environments, like agricultural sensors.

• Other resistances: The materials you use to design a high-frequency board should have higher ratings of temperature resistance, impact tolerance, and resistance to hazardous materials.

8. Aluminum-Backed PCB

Aluminum-backed circuits are designed uniquely like copper-based PCBs. But instead of the standard fiberglass applied in most circuits, aluminum-backed PCBs contain aluminum metal as their substrate material.

The aluminum layer is reinforced with a heat-insulating material with minimal heat resistance, implying less heat from the insulating material to the backing. After applying the insulation layer, you also need to use another layer of copper. Below are the benefits of aluminum-backed boards over fiberglass backing:

• Cost-effective. Aluminum is a readily available mineral, and it is easy to extract. This lowers its cost; hence, producing aluminum-based PCBs is a cost-effective process.

• Eco-friendly. Aluminum is a non-toxic mineral, and it is easily recycled. Because of its ease of assembly, making PCBs using aluminum is also an environmentally friendly approach.

• Heat conduction. Aluminum is one of the best metals of conducting heat away from the primary PCB components, like the CPU. Instead of distributing the heat to other parts of the PCB, it dissipates heat into the environment. Besides, aluminum-backed boards cool faster than copper-backed boards.

9. High-Density Interconnect (HDI) PCB

HDI PCB is a circuit with multiple interconnections occupying little space. HDI components are mounted close to each other, minimizing the PCB space while maintaining high functionality. A board containing 120-160 pins per square inch is classified as an HDI PCB.

HDI designs integrate dense device mounting and multipurpose routing. A compact circuitry is made with the help of microvias, buried vias, and blind vias, minimizing the drill-to-copper. Regarding the electrical requirements of high-speed signals, the HDI PCB must have high-frequency conduction ability, impedance control, and minimal redundant radiation.

10. Thick Copper PCB

Thick copper PCB is also known as Heavy Copper PCB. Basically, it contains more than 2 ounces of copper on the inner and outer layers of the board. Heavy copper transmitters significantly raise the general board thickness; hence, designers should consider the copper thickness during the design stage. Thick copper boards are known for backing frequency to high current, temperatures, and periodic thermal recycling, damaging the PCB easily.

11. High-TG PCB

A high-Tg PCB is a board designed to operate in high temperatures. The Glass Transition Temperature (Tg) is an essential element of any epoxy. It is basically the temperature point where the polymer changes from a hard, glass substrate to a soft, rubbery substrate. The substrates for making High-Tg boards must be flame-resistant, meaning they soften instead of burning at the glass transition point (Tg).

The higher the Tg value, the higher the temperature requirement during lamination. The PCB becomes hard and crisp in such conditions, affecting the hole size and related electrical properties. Standard board materials soften, deform and melt at such conditions, and their mechanical and electrical properties deteriorate significantly.

The standard FR-4 Tg is between 130-1400C, medium Tg is between 150-1600C, while high-Tg is more than 1700C. The higher the Tg value, the excellent the board’s performance to heat, moisture, and chemical resistance.

Conclusion

Whether you need a single-layer board or a custom 22-layer PCB, we can make your idea a reality. We provide manufacturing and assembly services for all types of PCB. Please contact us immediately to discuss your PCB requirements.

Whether you require a one-layered board or a custom 22-layered PCB, MKTPCB can turn your ideas into reality. We provide manufacturing and assembling services for all types of PCBs. Kindly contact us today to discuss your PCB needs.