Printed circuit boards (PCBs) are the backbone of modern electronics. They route electrical signals between all of the attached electronic components, bringing them to life.
Electronic devices or components can only function as intended with high-quality PCBs. As technology continues to evolve and consumers demand more from their electronics, manufacturers benefit from understanding how printed circuit boards are manufactured. The global PCB market is expected to reach $107.6 billion by 2030 as more organizations are manufacturing circuit boards.
A printed circuit board, or PCB, is a non-conductive material with conductive lines, also called traces, printed or etched into the base. Electrical components are mounted on the board, with traces connecting the components to form a working circuit. Most electrical devices use PCBs to provide physical and mechanical support.
The industrial PCB manufacturing process comprises many steps, checks, and balances to ensure the finished product performs as intended. Circuit boards can be single, double, or multilayered, but their construction only differs after producing the first layer. Many PCBs differ in their core structure, and could require more than 20 manufacturing steps to complete.
Designers classify various PCB types based on design specifications, manufacturing processes, and applications. The most common types of PCBs include:
The most common type of PCB is single-sided. It has a conductive copper layer above the substrate, and the electrical components are placed on one side of the board, leaving the entire etched circuit visible on the other. Because these boards have a single conductive layer, the conductive paths cannot overlap, which takes up additional space.
These PCBs are best suited to low-density design requirements and are often used for basic and low-cost electronic instruments. They are cost-effective and relatively easy to design, manufacture and repair.
Double-sided PCBs feature a thin layer of conducting material on the top and bottom sides of the board. Holes in the board allow the traces and component pins to be connected from one side to the other. Manufacturers can use two mounting methods to connect the circuits on either side.
This type of PCB has several advantages, including reduced size for more compact circuits, cost-effectiveness, and increased circuit density, making it suitable for advanced electronic systems.
These PCBs have more than two copper layers. Their design resembles a sandwich, with several conductive layers divided by insulating material sheets. The layers must be bonded and laminated together under high pressure and temperatures to remove air gaps and keep the PCB assembly stable. They are suitable for high-speed circuits as they are more compact than single or double-sided options and have high design flexibility and complexity.
Rigid PCBs have a solid substrate material, which gives the board rigidity and strength, and prevents twisting or folding. They consist of multiple layers, including:
These layers are bonded together with a mixture of adhesive and heat. Rigid PCBs are easy to diagnose, repair, and absorb vibrations, making them ideal for various applications, from medical equipment to laptops.
Flex PCBs comprise multiple printed circuits and components arranged on a flexible substrate such as polyamide, polyether ether ketone (PEEK), or a transparent conductive polyester film. Their design allows them to flex to the desired form during application. They’re available in single-sided, double-sided, and multilayer options. In addition to their flexibility, these boards are compact, highly reliable, and repeatable, making them suitable for high signal trace density applications.
German inventor Albert Hansen filed the first patent for a rudimentary PCB in 1903, and more complex patents followed. In the past half-century alone, we’ve experienced increased functionality on a micro level, allowing smaller devices to perform better than ever before.
The military played a massive role in transforming printed circuit board production. The U.S. Army Signal Corps devised methods to speed up the PCB production process with auto assembly, making it more efficient and economical to mass produce PCBs in consumer electronics.
The last 50 years have culminated in singular, lightweight PCB units suitable for multiple functions, allowing consumers to enjoy various media types on the same device. We’re entering a new world of innovation, and PCBs will enable many innovations, from driverless cars to smart homes.
A PCB has four principal parts, including:
The steps of the PCB design process start with design and verification and continue through the fabrication of the circuit boards. Many steps require computer guidance and machine-driven tools to ensure accuracy and prevent short circuits or incomplete circuits. The completed boards must undergo strict testing before they are packaged and delivered to customers.
Design is the first step in circuit board manufacturing. It acts as a plan for PCB manufacture and design — the designer lays out a blueprint for the PCB that fulfills all the outlined requirements. The most commonly used design exporting software used by PCB designers is a software called Extended Gerber — also known as IX274X.
Extended Gerber is an excellent PCB design software solution as it also works in an output format.It generates all the information that the designers and PCB manufacturers need,such as the number of copper layers, the number of solder masks needed,and the other pieces of component notation. Once a design blueprint for the PCB is encoded by the Gerber Extended software, all the different parts and aspects of the design are checked over to make sure that there are no errors.
Once the examination by the designer is complete, the finished PCB design is sent off to a PCB fabrication house so that the PCB can be built.Once there, a fabricator checks the design in a process known as a Design for Manufacture (DFM) check. An effective DFM check ensures that the design is manufacturable,given the manufacturing processes’ capabilities, and will not require excess resources or time to complete.
Progressive engineers may include the PCB manufacturer in a DFM process while in the PCB design phase instead of waiting until the design is completed. This way, they can make the necessary changes before order placement, saving time and money. If critical attributes are missing from the design, it can impact the manufacturer’s ability to produce the PC board with high yields.
Another key step of the printed circuit board fabrication process involves checking the design for potential errors, flaws, or manufacturability issues. An engineer performs a design review and goes over every part of the PCB design to ensure there are no missing components or incorrect structures.The design moves to the printing phase after getting clearance from an engineer and the client. Clients may want to approve any working files and verify array construction, tooling holes, multi-up array orientation, scoring, and snap tabs.
PCB plans follow a unique printing process. Unlike other plans, the process requires a specialized plotter printer to make a PCB film. Once printed, this film is essentially a photo negative of the PCB itself.
The plotter prints the PCB’s inside layers in two distinct ink colors:
On the outer layers of the PCB design, this trend is reversed — clear ink refers to the line of copper pathways, but black ink also refers to areas where the copper will be removed.
Each PCB layer and the accompanying solder mask gets its own film, so a simple two-layer PCB needs four sheets — one for each layer and one each for the accompanying solder mask.
Once the films for each layer of the PCB are printed, they’re lined up, and the printers use a punch machine to punch a hole through them, known as a registration hole. This hole is an alignment guide, allowing technicians to align the films throughout the manufacturing process.
In step four,the manufacturer begins construction of the PCB.The laminate panel is covered by a type of photo-sensitive film called the resist. The resist is made of a layer of photo-reactive chemicals that harden after they’re exposed to ultraviolet light. The resist allows technicians to get a perfect match between the photos of the blueprint and what’s printed to the photoresist.
Once the resist and the laminate are lined up — using the holes from earlier — they receive a blast of UV light.
The UV light passes through the translucent parts of the film, hardening the photoresist. This indicates areas of copper that are meant to be kept as pathways. In contrast, the black ink prevents any light from getting to the areas that aren’t meant to harden so that they can later be removed.
After the PCB design is printed onto a piece of laminate material, a copper foil layer or copper coating is applied.The copper is then pre-bonded to that same piece of laminate, which serves as the base for the PCB. The copper is then etched away to reveal the traces as designed on the blueprint from earlier.
The inner layers are part of a core, which has two layers of copper with dielectric material between them. The inner layers are treated with etch resist to protect the copper from etching away. The treatment is done before the core goes through the etching process. After etching, the only copper that remains is the copper intended by the designer.
Once technicians have prepared the board, they wash it with an alkaline solution or use a similar process to remove any remaining photoresists.They then pressure wash it to remove any debris or particles left on the surface and leave it to dry. Once dry, the only resist remaining on the PCB is on top of the copper. The technician then inspects the PCB for errors.
After drying, the only resist that should be left on the PCB is on top of the copper that remains as part of the PCB when it’s finally popped free. A technician looks over the PCBs to make sure that there are no errors. If no errors are present, then it’s on to the next step.
