Imagine a world without the technologies we have come to take for granted today, like the mobile phone, computer, television, radio, automobile, or airplane. Without the printed circuit board (PCB), it would be impossible to affix electronic components in specific locations on devices or reliably connect the components’ terminals in an organized manner. The fact is, most devices would not function without a proper PCB layout.
Creating a printed circuit board (PCB) layout is the same as completing a piece of art. Engineers may spend days, weeks, or even months designing these patterns to develop something unique. However, it’s not just engineers who can create a correct PCB layout; you can too.
If you don’t know where to start, we have created this article for you. The piece will help you understand a few things concerning the PCB layout process. While developing a PCB layout may look overwhelming initially, you will realize that you will soon be a pro if you start with simple designs and give yourself time to practice.
What Is PCB Layout?
Generally, a layout denotes the way the parts of a specific item are laid out or arranged. In the same vein, a PCB layout is a broad term indicating several processes required in designing a PCB. It involves making traces, mounting holes cutouts, labeling, and specifying component locations, among others.
One of the most important concepts in PCB design is wire routing. For instance, the design software maker, Autodesk.com, says, “PCB design is 90% placement and 10% routing.”
Routing is a follow-up step after placement. Placement involves determining the location of various components on the PCB. Routing involves adding wires to connect the components based on the design rules.
Creating a PCB layout can be done in two ways: manually or automatically. Almost all PCB design software has the auto-router feature. Because the auto-router function saves time and makes the process simpler, many designers use it.
Even though the auto-router function of PCB design is the easier path, it’s not always the best. This is because it’s not always as precise and symmetrical as it should be. To ensure that automatic routing produces the best results, you need to use proper parameters because they enable the automatic feature to calculate the routes correctly.
Be Clear about Producer Demands
Before you can begin placing components, you need to consult your producer first. It’s important to be clear about their demands, such as the number of layers they can handle. Other requirements may include things such as minimum trace widths and trace spacing.
Manage the Spacing of Originals in the Layout
When electricity passes through the copper traces, it will generate heat. This heat needs to be managed so that it doesn’t increase past a safe threshold. You can control this heat by managing the width of the marks and ensuring that there is adequate space between them, a process called PCB line spacing.
When dealing with a high-density interconnect PBC, line spacing can be a challenge. To determine what you need to do in line spacing in such situations, it’s vital to understand some important parameters. However, this can be tedious and time-consuming. The good news is that most PCB design software is designed based on the important parameters that need to be observed in specific situations.
Avoid Using a 90-Degree Angle
In PCB design, your most important goal is to incorporate all the components needed in your PCB. To do this, you need to determine spacing and the angle that your lines will take.
Most designers use either a 90-degree or a 45-degree angle. However, there is often disagreement as to whether a 90-degree angle works better than a 45-degree one.
Autodesk.com suggests that you should avoid using 90-degree trace angles? This is because “When you have a bunch of traces that have a sharp, right-angle turn on your board, the outside corner of that 90-degree angle has the likelihood of being etched narrower than your standard trace width.”
Instead of using 90-degree angles, rather use 45-degree tracing aspects because they prevent short circuits.
Always Create a Ground Plane
It’s always important to have a common ground terminal in the circuit schematics. It is essential for a PCB layout as it provides traces with the same reference point for measuring voltages. Problems arise when you attempt utilizing traces rather than ground planes to route to ground.
The software, hardware, and IP provider Cadence.com identifies the three crucial roles played by the ground plane in PCB design:
- Voltage return: Most, if not all, of the components in the PCB connect to a power net, and the ground net provides a pathway for the returning voltage.
- Signal return: Provides a pathway for returning signals so that they do not generate too much interference.
- Noise and interference reduction: A ground plane’s huge conducting area helps lower disturbance because it has a lower impedance than when traces are used to route the ground net.
In mixed-signal PCB layouts, one of the challenges is overlapping planes. A mixed-signal PCB layout has digital circuits and analog circuits on one board. If not properly managed, this overlapping could introduce the problem of interference between the digital and analog signals.
Therefore, at all costs, you will need to ensure that you avoid issues to do with overlapping when it comes to PCB layouts. Autodesk suggests that you should “always leave room between components at all times.”
PCB Layout Guidelines
Even though PCB layout is akin to art, it’s important to approach it in an organized manner. To come up with the best design, the three steps below are crucial:
- Turn your schematics into a form of a PCB layout.
- Add and subsequently rotate the components to reduce the air wires’ lengths and crossing.
- Adjust the layout size for routing.
PCB designers often struggle with issues related to electromagnetic interference (EMI). Cadence.com defines EMI as the “electromagnetic energy that disrupts the signaling in an electronic device through radiation or induction.” Adding, “From the static on your radio to that buzz you hear when you bring a cell phone near audio equipment, EMI is all around us.”
Let’s take a deeper look at the three types of EMI:
- Conducted Coupling: This happens if the noise from the energy source is conducted to all circuits.
- Electric field coupling: This is a situation where energy is coupled from one circuit to the other via an electric field, usually when the sources circuit impedance is high.
- Magnetic field coupling: Is the coupling energized or driven by the current; it’s equivalent to the source’s flow.
Cadence.com lists some common methods of dealing with EMI:
- Use a multi-layer board so that you can have more options for handling high-speed traces.
- Only use ground planes when required.
- Connect split ground planes to one point.
- Connect bypass of decoupling capacitors to the ground plane.
- Avoid bends that turn at sharp right angles.
- Ensure that high-speed signals are separate from low-speed signals and analog signals are separate from digital signals.
- Make return paths as short as possible.
- Route differential traces as close as you can.
- Be careful when using vias and avoid the use of vias in differential traces.
- Separate analog and digital circuits.
- Isolate high-speed components.
On a PCB, synchronous digital circuits are commonly the most reliable signals. Therefore, at narrow bands, it is possible to observe radiated emissions. Also, these peaks tend to take place at the harmonics of the frequency of the clock.
Clocks are vital for differentiating between pulses defining received or transmitted information. Plenty of PCBs don’t have clock signals but rather have some useful digital information.
Power Switch Circuit
Paying attention to the switching power circuit is important in PCB design because a defective power supply could result in a considerable failure even if the circuit is designed correctly.
Switch-mode power supplies and DC converters provide several voltage levels by rapidly switching voltage levels in a transformer. The switch circuit is designed to use an ON and OFF feature based on a specified power range.
Elements of a PCB Layout
In its basic form, a PCB layout means transferring a circuit from a breadboard into a permanent and stable physical form.
Creating a PCB layout involves the following elements:
A schematic is a diagram of components, circuits, and connections laid out in a way that’s easy to follow. When designing PCB layouts, it’s always necessary to begin with schematics. Schematics help with constructing and understanding the system of circuits.
PCBs supporting high-frequency signals demand special requirements. Many of the interfaces used today operate at more than 50 MHz, meaning that some knowledge on how to avoid issues with high-speed signals is essential. At high frequencies, PCB layouts are all about understanding the physics of electron flow.
With technology continuing to advance at unprecedented speeds, the frequency of signals has become blazing fast. Therefore, the need to understand signal propagation is a big necessity. Also, there’s a need to close the gap between analog and digital designs.
The Routing of Signal and Placement of Components
When it comes to signal routing and the placement of components, all you need to know is the direction in which the signal and currents will flow on your PCB. You need to keep your digital signals as far away from the analog signals as possible. Analog circuits tend to be sensitive to digital signals, which can introduce noise on the analog side.
Radio Frequency PCB Layout
Radio Frequency (RF) PCBs are an exciting and growing sector across the PCB industry. Autodesk.com speculates that the popularity of this type of design is being driven by the “proliferation of IoT sensors, wireless electronics, and smartphones.”
In the PCB industry, any board that operates at frequencies above 100MHz is deemed an RF PCB. The microwave PCB frequency is about 2GHz.
The RF PCB design is usually a 2-layer or 4-layer board. Component arrangement requirements will be more stringent with RF PCBs, so professional PCB layout design knowledge is needed.
Issues with PCB Design and Layout
When it comes to the design and manufacture of almost everything, having a functional layout is essential. Likewise, in PCB production, having a good structure in place brings about the desired results. However, there are a few issues that concern the PCB layouts.
Wrong Designing Tools
As you would expect in any situation, using the wrong tools will produce the wrong results. In some cases, PCB designers use the wrong tools because they don’t know any better. However, there are situations where designers use the wrong tools because they believe that this will save them money.
If you select the cheapest tools because you want to save money, you could end up paying a lot more to remedy the situation. You can circumvent this challenge by ensuring that you do your homework to identify the best hardware and software for your PCB design project.
Lack of Preparation
Producing a PCB is not an easy process. Some of the basic PCB design and layout considerations include the shape and size of the PCB. Complex PCB layouts preparation problems are related to creating the best layout between traces, trace widths, and other factors that may affect board functionality.
Solving layout preparation problems is usually accomplished through employing sophisticated software. Using PCB layout services is another way of leveraging the experience of companies that have been in the field for many years.
PCB Layout Software
In any industry, software programs reduce the effort and time required to produce goods and services. Like in most industries, PCB design and layout have come to depend on programs that automate processes.
Some of the best PCB layout software in the market include:
Autodesk Eagle: Comes with a schematic editor for designing diagrams and also has a PCB layout editor.
KiCad: This is a cross-platform and open-source electronics automation suite. It includes a PCB editor for producing professional PCBs and a schematic editor for editing and creating schematic designs.
Fritzing: Has several features, including a schematic, a breadboard layout, and a PCB view.
DesignSpark PCB: Provides an easy-to-learn environment consisting of schematics capture and a PCB layout tool.
EasyEDA: Delivers a library designer, a PCB editor, and a project management tool.
UpVerter: Has similar features to EasyEDA and enables hardware engineers to create, share, and review PCBs and schematics.
ExpressPCB Plus: Is EDA software for designing and creating electronics circuitry.
TinyCAD: This is an open-source software project that supports custom and standard symbol libraries. It also supports PCB layout programs consisting of several formats.
Osmond PCB: This is the only MAC-based EDA tool that supports schematic capture and PCB layout design.
PCB Layout Services
Even though you could do your own PCB layout, using a PCB layout service could deliver several advantages. These layout services can be of great assistance, particularly if you are a beginner in this field.
PCB layout services are available for existing and new PCBs. Some advantages of using PCB layout services include:
Technical competency: Having access to an expert is a significant advantage when designing PCBs.
Streamlined process: With PCB layout services, errors can be detected and fixed early, allowing you to improve products before marketing.
Better quality: Layout services come with better quality because every service wants to be better than the competition.
Fast turnaround: With the services of a specialist, PCBs can be designed on time based on careful planning.
Cheap: Due to economies of scale, using PCB layout services could be cheaper than doing your own PCB designs.
Standard PCB Layout Designer Deliverables
Credible PCB designers meet a minimum set of deliverables, including:
- Bill of Materials list (BOM)
- Fabrication files
- PCB layer stack diagrams
- Complete schematics
- Full Gerber files
- Plenty of software
- 3D PDF files
- Route and drill files
PCB layouts are essential for proper board functionality. Suppose you are having a tough time undertaking your board layout. In that case, you can always look for assistance from a company that manufactures PCBs under the best layout plans. Ensure that the company understands the importance of PCB layouts so that your boards will function as intended.