May 23, 2018|Product Innovations and Design, Technological Advancements and Materials

Printed Circuit Boards or PCBs are the heart of many modern electronics and the cornerstone of numerous industries and products. Take apart a smartphone, computer, or video game console, and you will find a small green board constructed of staggering arrays of lines, grooves, and interconnections. This incredible little maze atop a green square is the PCB, and it enables different complex electronics to function as intended.

PCBs use copper conductors to create necessary electrical connections between components. They can also provide mechanical support for electronic components, and are comprised of alternating layers of conductive copper between layers of electrically insulating materials. These conductive features include pads, conductive planes, and copper traces. Once the structure of a PCB is plated and covered with a solder mask, the silk screen overly provides a legend for all electronic components. After fabrication, the bare PCB is sent to assembly where its components can be soldered and it can be tested.

PCBs are found almost everywhere, from household electronics to aerospace and defense technologies. Radar systems, laptop computers, and hybrid cars all contain a PCB. There are numerous different types of circuit boards made with varying layers and components, including single-sided, double-sided, and multilayer. The average PCB has between 4 and 12 layers, with varying degrees of complexity, integrity, flexibility, and size depending on its use. High-Frequency PCBs, Flexible and Rigid-Flex PCBs, and High-Density Interconnect PCBs all serve functions beyond the traditional circuit board and enable electronics to function in a wide variety of business and government sectors.

There are many different ways to produce a PCB. As consumer and industry demands change and technology evolves, PCB innovations must adapt for efficiency, quality, and durability. These demands and innovations have led PCB manufacturing companies to be even more creative, and come up with new ways to develop these circuit boards.

Let’s look more closely at how a board is made, what it’s made from, how it’s used, and why these tiny but powerful devices are so essential.

Overview of PCBs

A Printed Circuit Board (PCB) is what connects all the electrical components inside an electronic device. It is a small green board made out of precious metals that are essential to the function of electronics. You will find a PCB in most electronic devices.

What Does a PCB Do?

The PCB inside electronics is what allows them to function as they are intended too. Without PCBs, electronics would not work. Through the conductive tracks, pads and other portions of the PCB, it helps connect all the electronic components within the intended device.

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History of PCBs

There is a long history of a PCB. It goes back to 1943, developed by Australian scientist Dr. Paul Eisler. However, the development of PCBs goes back into the early 1900s when patents for what is known as “printed wire” were requested. It was an electrical path which was directly made onto an insulated surface. Many different scientists fiddled around with laminated conductors to an insulated board. In 1904 Thomas Edison used chemical methods to plate conductors to linen papers.

In 1925, US citizen Charles Ducas submitted a patent for creating an electrical path right on to an insulated surface. This was done through a printing a stencil with electrically conductive ink.

However, it was Eisler that created the first operational board to replace radio tube wiring. In 1936 he began work on a printed circuit for a radio set. In 1943 during World War II, the United States started to use technology to develop proximity fuses on a large scale.

Typically PCBs were made out of different materials, including Masonite and thin wooden planks. It wasn’t until the 1950s when other materials were used that they became common in household electronics. Before that, they were more intended for government usage.

As the years continued and PCB’s continued to evolve, new methods came to the front for developing the boards. Copper replaced the other materials involved in making the board because of it being an excellent way to carry electrical currents at a low cost. They also were required to be smaller in size as the demand for smaller electronics increased.

Manufacturing Process of PCBs

There are multiple steps included when manufacturing a PCB. To correctly assemble a PCB, the environment must be clean to keep all the components free from contamination. Here is an example of building a standard two-sided PCB:

  1. Start With the Design:

Using a PCB design software, the designer comes up with what the PCB will look like and how it will function. The designer should include information like the copper tracking layers, all components involved, drill drawing and anything else that contributes to the PCB. It is then sent for production.

  1. Creating a Film:

The design of the PCB is then printed using a special machine (plotters) that creates photo films of the PCB. These machines are specially made for this process to achieve precise printing and high details. You then have a plastic sheet with ink resembling different layers of the PCB.

  1. Printing the Inner Layers:

This step is when the physical creation of the PCB begins. The substrate level starts by using an epoxy resin mixed with a glass fibre (prepreg). Copper is then bonded to both sides and then whittled away to reveal the design of the board. A photosensitive film (resist) is then added to the panel.

  1. Remove Excess Copper:

Any unwanted copper left on the board is then removed. A chemical solution eats the excess copper away. The hardened photoresist protects the wanted copper.

  1. Aligning the Layers:

All the layers of the board need to be aligned and punched together. Holes on each layer are lined together and sent through an optical punch machine. From here on out, any errors found on the inner layers cannot be corrected.

  1. Layer Together:

Here is when the PCB takes its shape. The additional layers are fused together with the substrate. They are then bonded together to ensure they fit securely together.

  1. Drill:

Holes are then drilled to keep the layers from being plated.

  1. Plating:

The PCB then goes into the plating process to fuse everything together. The board is immersed in copper, after being thoroughly cleaned, to create a thin plate.

  1. Outer Layer Resist:

Once again, a photoresist layer is added to the out layers, and the board is ran under UV lights.

  1. Second Plating:

There is another step of plating needed with a layer of copper. From the previous copper plating, a layer of tin is applied to prevent any of the wanted copper from being etched off.

  1. Final Etching:

The same chemical solution again removes unwanted copper from the board. This establishes the proper conducting areas and required connections.

  1. Solder Mask Application:

The cleaned board is covered with an epoxy solder mask and blasted with a UV light.

  1. Finishing Touches:

The board is then plated with either gold or silver to add solder quality to it. Then the board goes through an ink-jet writing process onto the surface which holds critical information for the board. It is then coated and cured for the last time.

How Does a PCB Work?

Fibreglass layers are stacked on top of each other and treated with a resin to keep them together. They are then covered with a copper layer on either side and then coated with a photoresist. It is then covered with the design that ultimately holds the controls of the board. They look like tracks on a PCB. Those tracks are the electrical connections that power the electrical device.
What is the Material Used in a PCB?

PCB’s tend to have a copper layer and an insulating layer that is laminated to the substrate. The substrate is typically made out of a fibreglass epoxy resin and bonded with copper foil. There is also the use of tin for layering the copper circuits to prevent oxidation. You will also find materials like gold, silver, nickel, aluminium and palladium during certain aspects of the PCB development.

What are the Components of a PCB?

Each component is vital to the overall board. They all have their own task for the PCB to function correctly. Typically you would find the following elements on a standard Printed Circuit Board:

  • Battery – provides the voltage to the board.
  • Inductor – stops and changes in the current.
  • Diode – what makes the current flow in one direction.
  • Switches – depending on if they are opened or closed, they will block or allow current.
  • Resistors – they are color coded to determine how much current passes through.
  • LEDs – (light emitting diode) lights that illuminate when current is flowing and allows only enables the flow of one current in one direction.
  • Capacitors – holds an electrical charge.

What is a PCB Layout Software?

A PCB Layout Software is what is used during the initial design step of developing the board. The software is what generates the design of the board which is then taken into the production steps. Depending on the type of board you are developing, and what the intent is, that will determine which software you use.

What is the Use of a Printed Circuit Board?

A PCB is used for electronic devices, no matter the size. The small board not only powers the components in the device, but it also powers the whole device itself. Without the PCB the electronic machine would not function to its full intention.

A PCB also makes the development process of electronics a little more simplified. Before the invention of a PCB, the inside of an electronic device would be scrambled with wires and connections. This meant the device needed to be fairly large to hold all of the wires. Now a PCB simplifies the connection which allows for devices to be much smaller in size.

PCB Terminology

There is a lot of different terminologies used to describe what a Printed Circuit Board is. Here are some of those terms:

  • Pad – the exposed metal on the surface of the board which has a component soldered to.
  • Substrate – this is physical structure that holds the components.
  • Single-Sided – all the components are on one side of the substrate.
  • Double-Sided PCBs – when there are too many components for a single-sided PCB, a double-sided board is used.
  • Multi-Layered – the substrate is separated by layers of insulation with components connected through plated holes.
  • Flexible PCBs – boards made with flexible materials when special constraints limit the use of a rigid circuit board.
  • Buried Vias – the vias make the connection between the layers of a PCB. Buried vias connect multiple inner layers without going through the outer layer.
  • Thick Printed PCB – the thickness level of the board influences the functionality of the board.

Advanced PCB Technologies

High-Frequency PCBs

The demands of modern telecommunications industries have put immense pressure on the continued growth of High-Frequency circuit boards. By facilitiating the smooth transmission of data, voice, and video signals across various networks, High-Frequency PCBs guarantee that products and innovations guarantee dependable and effective communication in the modern age.

High-Frequency Printed Circuit Boards or HFPCBs are fabricated out of unique materials that allow them to transmit high-frequency signals above 500MHz. Applications include aerospace, military, RF microwave, and telecommunications, and these boards must be designed with several special considerations and parameters that help them to meet specific signal requirements of the particular high-frequency application. 

High-Frequency PCB parameters include:

  • Dielectric Constant (Dk)
  • Temperature Coefficient of Dielectric Constant (TCDk)
  • Dissipation Factor (Df)
  • Thermal Conductivity
  • Coefficient of Thermal Expansion (CTE)

Flexible and Rigid-Flex PCBs

With the advent of revolutionary consumer electronics such as compact computers, smartphones, and video game consoles, Flexible PCBs allow for new and exciting innovations. Fitness trackers, foldable touch screens, and more ergonomic products utilize Flexible and Rigid-Flex PCBs in order to conform to design trends and push enhanced comfort and functionality.

“Rigid” PCBs are the most common type of Printed Circuit Board. Flexible and Rigid-Flex PCBs have many similarities to traditional circuit boards, such as conductive tracks on a non-conductive substrate. Still, these flexible models use base materials like polyimide to add a dimension of flexible circuits that can better dissipate heat, withstand vibration, and fold into various shapes. 

There are a few notable differences between traditional PCBs and flex circuits, such as:

  • Conductive Materials – Flex circuits have to bend, and manufacturers use rolled annealed copper instead of rigid electro-deposited copper.
  • Manufacturing – Flexible PCBs are created with overlay or coverlay, which protects a flexible PCB’s more exposed circuitry.
  • Costs – Flex circuits cost more to develop, but their ability to fit into compact spaces allows engineers to shrink product size, indirectly leading to other savings.

When considering your application’s demands, it’s important to choose between rigid and flexible PCBs and consider your industry’s preferred circuit board type. Efficacy, profit, and design will all factor into whether your product should use Rigid, Flex, or Rigid-Flex PCBs.

HDI (High-Density Interconnect) PCBs

We live in an age of continual electronic advancement, with new technologic innovations that allow for state of the art electronic devices. As consumer demands and industry needs grow, products and devices are more tightly packed with miniaturized components and intricate circuitry than ever. High-Density Interconnect PCBs have pushed various electronics industries forward by enabling advancements in miniaturization without a loss of quality.

High-Density Interconnect PCBs or HDI PCBs are designed with a greater wiring density, making them more attractive than conventional PCBs for specific applications. Their higher connection pad density, multilayer board design, finer lines, smaller via holes, and capture pads allow micro vias to penetrate specific, select layers. HDI boards are also more compact, and their denser wiring results in a lighter weight, and lower layer count PCB. As PCB technology evolves, this changing technology allows for smaller and faster products. 

HDI-printed PCBs have several benefits, including:

  • Cost – Overall costs of HDI PCBs are reduced because of the necessary layers and smaller sizes, especially compared to standard PCBs.
  • Time-to-Market – Production efficiencies mean better production and development, which means a shorter time through the design and testing process.
  • Reliability – Micro vias are more reliable than typical through holes, granting HDI PCBs improved performance with better parts and materials.

Future Trends in PCB Manufacturing

PCB manufacturing is an ever-changing industry where technology and innovation lead to incredible advancements. As the demand for high-speed, compact, and performance-driven electronic devices increases, so does the demand for complex, innovative PCBs. Circuit boards are an integral component of electronic devices, and advancements have positively impacted industry after industry. New research, innovation, and development must be continuously considered as products and innovations evolve. 

Enhancements and emerging trends have affected every application sector, including medicine, aerospace, defense, 3D printing, AI-driven quality control, IoT integration, and flexible PCB technologies. PCB manufacturers and engineers are embracing these new trends and meeting challenges to produce effective circuit boards for years to come. These trends drive growth and innovation in the industry, and set the stage for a bright future of products and technologies. 

Emerging PCB trends include:

  • Cutting-edge materials that enable PCBs to handle high-frequency signals for 5G and high-speed transmission. 
  • Improved signal integrity that reduces signal loss for mission-critical applications in military and government communication.
  • Miniaturization allows for PCBs with reduced size and components that enhance the integration of high-density interconnections. 
  • Technological advancements that allow the creation of complex, space-efficient PCBs that don’t compromise quality.
  • Robotic automation that improves speed, precision, and efficiency. 
  • Machine learning and AI integration that optimizes the PCB manufacturing process.
  • Improved design, testing, and quality control via intelligent decision-making and predictive maintenance technologies. 
  • IoT’s massive expansion, including sensors and connected machines, improves production efficiency and collects real-time data across multiple parameters such as temperature and machine performance.
  • Energy-efficient machinery that allows companies to reduce their footprint.
  • Enhanced cybersecurity measures that reduce vulnerability to cyber threats.
  • Better testing and inspection technologies allow manufacturers to focus more on overall PCB quality.
  • Automated optical inspections that help identify defects and faults at every stage and prevent production errors.

PCB Solutions

PCBs are the backbone of electronic technology and continue to evolve industry after industry. As the leader in PCB manufacturing and design, Candor Industry’s expertise in advanced circuit board development has created innovations in aerospace, military, and consumer products globally. Contact us today and request a custom quote or learn more about Candor’s innovative circuit board solutions. 

Author Profile

Sunny Patel
Sunny Patel is the Engineering and Sales Manager at Candor Industries. Sunny is trained as a IPC-A-600 trainer, AS9100 Lead auditor, IPC CID and got his Engineering degree at the University of Toronto.

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