Printed circuit board (PCBS) are boards used as substrates in most electronic devices – both as physical supports and as wiring areas for surface mount and socket assemblies. PCBS are usually made of fiberglass, composite epoxy resin, or other composite materials.

PCB type introduction

Most PCBS for simple electronic devices are simple and consist of only a single layer. More complex hardware such as computer graphics cards or motherboards can have multiple layers, sometimes as many as 12.

Although PCBS are usually associated with computers, they can be found in many other electronic devices, such as televisions, radios, digital cameras and cell phones. In addition to being used in consumer electronics and computers, different types of PCBS are used in a variety of other areas, including:

• Medical equipment. Electronics are now more dense and consume less power than previous products, so new and exciting medical technologies can be tested. Most medical devices use high-density PCBS for creating the smallest and most dense designs. This helps to alleviate some of the unique limitations involved in developing devices for use in the medical field due to the need for small size and light weight. PCBS have made inroads into everything from small devices (like pacemakers) to large ones (like X-ray equipment or CAT scanners).

• Industrial machinery. PCBS are commonly used in high-power industrial machinery. Thick copper PCBS can be used where current one-ounce copper PCBS do not meet requirements. Thicker copper PCBS are beneficial in cases including motor controllers, high-current battery chargers and industrial load testers.

• lighting. Because LED-based lighting solutions are popular because of their low power consumption and high efficiency, so are the aluminum backplane PCBS used to make them. These PCBS serve as radiators and allow for higher levels of heat transfer than standard PCBS. These same aluminum backboard PCBS form the basis of high lumen LED applications and basic lighting solutions.

• Automotive and aerospace industries. The automotive and aerospace industries use flexible PCBS designed to withstand the high vibration environments common in both fields. Depending on specification and design, they can also be very lightweight, which is necessary for manufacturing parts in the transportation industry. They can also fit into tight Spaces that may exist in these applications, such as inside the dashboard or behind the instruments on the dashboard.

There are many types of PCB boards, each with its own unique manufacturing specifications, material types and uses: single layer PCB, double layer PCB, multi-layer PCB, rigid PCB, flexible PCB, rigid flexible PCB, high frequency PCB, aluminum back PCB.

A single layer PCB

Single – or single-sided PCB is a PCB or substrate made from a single substrate. One side of the substrate is coated with a thin metal layer. Copper is the most common coating because of its good electrical conductivity. Once a copper-based coating is applied, a protective welding mask is usually used, followed by the use of all elements on the last screen printing plate.

PCB type introduction

Single-layer/single-side PCBS are easy to design and manufacture because they weld the various circuits and components on only one side. This ubiquity means they can be purchased at low cost, especially for high-volume orders. Low-cost, high-capacity models mean they are commonly used in a variety of applications, including calculators, cameras, radios and stereo equipment, solid-state drives, printers and power supplies.

Double-layer printed circuit board

The substrate material for a double – or double-sided printed circuit board has a thin layer of conductive metal, such as copper, applied to both sides of the board. Holes drilled through the board allow circuits on one side of the board to connect to circuits on the other side.

PCB type introduction

Components of a circuit and a double-layer PCB board are usually connected in one of two ways: using a through-hole or using a surface mount. A through-hole connection means that small wires called leads are fed through the hole, with each end of the leads welded to the right-hand component.

Surface mount PCBS cannot use wires as connectors. Instead, many of the small leads are welded directly to the board, meaning that the board itself is used as a wiring surface for the different components. This allows the circuit to be completed with less space, freeing up space to enable the board to perform more functions, often faster and weighing less than the through-hole board would allow.

Double side PCBS are commonly used in applications that require intermediate levels of circuit complexity, such as industrial controls, power supplies, instrumentation, HVAC systems, LED lighting, car dashboards, amplifiers, and vending machines.

Multilayer PCB

Multi-layer PCB consists of a series of three or more layers of double-layer PCBS. These plates are then held together with special glue and clamped between the insulation pieces to ensure that excess heat does not melt any of the components. Multi-layer PCBS come in a variety of sizes, as small as four layers or as large as ten or twelve. The largest multilayer PCB ever built is 50 layers thick.

PCB type introduction

For multilayer printed circuit boards, designers can produce very thick, complex designs suitable for a variety of complex electrical tasks. Beneficial applications for multilayer PCBS include file servers, data storage, GPS technology, satellite systems, weather analysis and medical devices.

Rigid PCB

Rigid printed circuit boards are printed circuit boards made of a strong substrate material that prevents the board from twisting. Probably the most common example of a rigid PCB is a computer motherboard. The motherboard is a multi-layer PCB designed to distribute power from the power supply while allowing all parts of the computer to communicate with each other, such as the CPU, GPU and RAM.

Rigid PCB composition is perhaps the largest number of PCBS manufactured. These PCBS can be used anywhere the PCB itself needs to be set to a shape and remain so for the rest of the life of the device. Rigid PCBS can be simple single-layer PCBS, or 8-layer or 10-layer PCBS.

PCB type introduction

All rigid PCBS have single, double, or multilayer structures, so they share the same application.

Flexible PCB

Unlike rigid PCBS, which use non-stick materials such as glass fiber, flexible PCBS are made of materials that can be bent and moved, such as plastic. Similar to rigid PCBS, flexible PCBS come in single, double, or multi-layer formats. Because they need to be printed on flexible materials, they tend to be more expensive to manufacture.

PCB type introduction

Still, flexible PCBS offer many advantages over rigid PCBS. The most striking of these advantages is their flexibility. This means they can be folded around the edges and wound around the corners. Their flexibility saves on cost and weight by using a single flexible PCB to cover areas that might need multiple rigid PCBS.

Flexible PCBS can also be used in areas that may be affected by multiple rigid PCBS. Environmental hazards. To this end, they are manufactured only from materials that may be waterproof, shockproof, corrosion-resistant or high-temperature oil-an option that traditional rigid PCBS may not have.

Flexible rigid PCB

When it comes to the two most important overall PCBS, flexible rigid PCBS combine the best of both. The flexible rigid board is composed of multiple flexible PCB layers attached to multiple rigid PCB layers.

Flexible rigid PCBS have many advantages over using rigid or flexible PCBS only in certain applications. For example, rigid-flexible plates have a smaller number of parts than traditional rigid or flexible plates because the wiring options for both can be combined into a single plate. Combining rigid and flexible boards into a single rigid-flexible board also allows for a more streamlined design that reduces overall board size and package weight.

PCB type introduction

Flexible rigid PCBS are most often found in applications where space or weight is of greatest concern, including mobile phones, digital cameras, pacemakers and cars.

High-frequency PCB

Hf PCBS refer to general PCB design elements rather than PCB construction as in previous models. Hf PCBS are circuit boards designed to transmit signals in excess of 1 gigahertz.

PCB type introduction

Hf PCB materials typically include FR4 grade glass fiber reinforced epoxy laminate, polyphenylene ether (PPO) resin and teflon. Teflon is one of the most expensive options because of its small and stable dielectric constant, small dielectric loss and overall low water absorption.

Many aspects of the PCB board and its corresponding type of PCB connector need to be considered when selecting high frequency, including dielectric constant (DK), dissipation, loss, and dielectric thickness.

The most important of these is the Dk of the material in question. Materials with a high probability of dielectric constant change often produce impedance changes that disrupt the harmonics that make up the digital signal and lead to an overall loss of digital signal integrity — a factor that hf PCBS are designed to prevent.

Other considerations when choosing the type of circuit board and PC connector to use when designing hf PCBS include:

• Dielectric loss (DF), which affects the quality of signal transmission. Small dielectric loss may result in a small amount of signal waste.

• Thermal expansion. If the materials used to build the PCB, such as copper foil, have different thermal expansion rates, the materials may separate from each other due to temperature changes.

• Water absorption. High water intake can affect the dielectric constant and dielectric loss of a PCB, especially when used in wet environments.

• Other resistors. Materials used to construct HF PCBS shall be rated as required for heat resistance, impact resistance and hazardous chemicals.

Aluminum backing PCB

The design of an aluminum backed PCB is roughly the same as that of a copper backed PCB. However, instead of using fiberglass, which is common in most PCB board types, aluminum backplane PCBS use aluminum or copper substrates.

PCB type introduction

The aluminum backing is lined with insulation and is designed to have low thermal resistance, meaning less heat is transferred from the insulation to the backing. Once insulation is applied, layers of copper circuit from 1 ounce to 10 inches thick are applied.

Aluminum backed PCBS have a number of advantages over fiberglass backed PCBS, including:

• Low cost. Aluminum is one of the most abundant metals on Earth, accounting for 8.23% of the earth’s weight. Mining aluminum is easy and cheap, which helps reduce costs in the manufacturing process. As a result, it is cheaper to make products out of aluminum.

• environmental protection. Aluminum is non-toxic and easy to recycle. Making printed circuit boards from aluminium is also a good way to save energy because it is easy to assemble.

• heat dissipation. Aluminum is one of the best materials that can be used to dissipate heat from key components of a circuit board. It does not radiate heat to the rest of the plate, but to the open air. Aluminum PCBS cool faster than copper PCBS of the same size.

• Material durability. Aluminum is more durable than materials like fiberglass or ceramic and is especially good for drop tests. Using stronger substrates helps reduce damage during manufacturing, transportation and installation.

All of these advantages make aluminum PCBS an excellent choice for applications requiring high output power within very tight tolerances, including traffic headlights, automotive lighting, power supplies, motor controllers and high current circuits.

In addition to their main areas of use, aluminum-backed PCBS can also be used where a high degree of mechanical stability is required or where the PCB may withstand high levels of mechanical stress. They are less susceptible to thermal expansion than fiberglass panels, which means that other materials on the board, such as copper foil and insulation, are less likely to peel off, further extending the life of the product.

Over the years, PCBS have evolved from simple single-layer PCBS such as calculators for electronic devices to more complex systems such as high-frequency Teflon designs. PCBS have found their way into almost every industry on earth, from simple electronics like lighting solutions all the way to more complex industries like medical or aerospace technology.

The development of PCBS has also led to the development of PCB building materials: no longer just PCBS made of copper foil backed by fiberglass. New building materials include aluminum, teflon and even bendable plastics. Bendable plastics and aluminum in particular have facilitated the creation of products such as rigid-flexible and aluminum-backed PCBS to solve common problems associated with many industries.