All printed circuit boards essentially perform similar functions, but there are three main types — rigid, rigid-flex, and flex — which all differ in terms of design and construction.
Your Guide to PCB Design Basics & Steps
Your time is valuable, which is why you want to design your printed circuit board correctly from the start. In our comprehensive guide, we cover everything you need to know, including PCB design basics and steps, materials and composition, best practices, and more so that you’re prepared to design the best possible printed circuit board.
PCB and Flex Design Basics
A printed circuit board (PCB) is a flat plate or base of insulating materials that contains a pattern of conducting material and components, and some projects can be quite complex. But all PCBs have to start somewhere — and that’s with design.
Why are PCB design basics so important? Multiple extensive revisions can seriously delay the completion of your project — costing you time and money. It’s important to work with engineering experts from the beginning so that you can design for manufacturability and ensure a final, cost-effective product that works efficiently and effectively.
Step-by-Step PCB Design Guide
From the initial drawings to the final files, here are the 9 steps toward designing a printed circuit board:
1. Understand the electrical parameters.
Before starting a PCB design, you should know and understand the electrical parameters of the system, including:
- Current maximums
- Signal types
- Capacitance limitations
- Impedance characteristics
- Shielding considerations
- Type and location of circuit components and connectors
- Detailed net wire listing and schematic
2. Creating the schematic.
One of the first steps is always creating a schematic, which refers to the design at the electrical level of the board’s purpose and function. At this point, it’s not yet a mechanical representation.
3. Use a schematic capture tool to create your PCB layout.
The right PCB provider will work with principal engineers to develop a schematic with a software platform such as Mentor PADS®, Allegro, or Altium, which shows you exactly how your board will operate and where the components will be placed. After you create your schematic, the mechanical engineer will load the design and determine how it will fit in the intended device.
4. Design your PCB stackup.
This is important to consider early on in the PCB design stage due to impedance, which refers to how much and how quickly electricity can travel down a trace. The stackup plays a role in how the mechanical engineer can design and fit the PCB into the device.
5. Define design rules and requirements.
This step is largely dictated by standards and acceptability criteria from the IPC, which is the industry association for PCB and electronics manufacturing. These standards tell you everything you need to know regarding PCB manufacturing. An important tip: Find a PCB layout provider who is extremely familiar with IPC standards; this can help you avoid major revisions and project delays.
6. Place your components.
In many cases, the customer and PCB provider will discuss design and layout guidelines when it comes to the placement of components. For example, there may be standards indicating that certain components cannot be placed near others because they create electrical noise in the circuit. The PCB provider will have data sheets on every component (in most cases these are connectors), which will then be placed in the mechanical layout and sent to the customer for approval.
7. Insert drill holes.
This step is driven by the components and a connection. About half of the flex circuits on the market are double-sided, which means they have connection to the drill hole on the bottom layer.
8. Route the traces.
After you’ve placed the components and drill holes, you’re ready to route the traces, which means connecting segments of the path.
9. Add labels and identifiers.
Now is the time to add any labels, identifiers, markings, or reference designators to the layout. Reference designators are helpful in showing where specific components will go on the board.
10. Generate design/layout files.
This is the final step in the layout process. These files contain all the information pertaining to your printed circuit board, and once they have been generated, your PCB is now ready for fabrication and manufacturing and assembly.
PCB Design Best Practices
It’s important to communicate with the PCB or flex application engineer during the beginning of any PCB design job and discuss everything you need or require for your project. Open and constant communication with your PCB provider ensures that you’re both on the same page, which can reduce the need for multiple extensive revisions.
While it is rare that a printed circuit board is 100% perfectly designed on the first try, communication will help ensure that your PCB is properly designed from the start and that any revisions are not major ones that will derail your project and timeline.
When you submit a design, you also need to have the right board size, trace width, materials, component placement, and tolerances. Plus, in the case of flex, you’ll need to determine whether the design is static, partly flexible, or dynamic.
It’s also important to consider the environment in which the product has to function. Is the printed circuit board or flex circuit designed for a non-extreme environment, such as your cell phone, or the highest of extremes, such as an explosion?
You’ll likely have questions about the PCB design and layout process, which means it’s best to find a reputable PCB provider with extensive engineering experience who can answer your questions and ensure a smooth project from start to finish.
PCB Composition & Materials
A copper-clad substrate or polyimide-based film is often used for flex circuits, and FR4 (or an FR4 stiffener) is used for rigid-flex. FR4 allows you to build up the layers as the technology content is created.
A solder mask is also used, which is a technique where everything on the circuit board is coated with an epoxy-based LPI or cover coat for flex, except the contacts to be soldered, the gold-plated terminals of any card-edge connectors, and fiducial marks.
PCBs also include a legend application, which are the decals and reference designators in epoxy ink on a board. The name refers to the method of application in which the ink is automatically applied similar to ink jet printers
PCB Layout Capabilities
Cirexx can configure digital, analog, mixed signal technology, controlled impedance, matched length pairs DDR, RF layout, and high speed signals up to 100+ GHz for all of the following PCB structures:
- Flex circuits
- Rigid-flex circuits
- Rigid circuits
- Hybrid circuits
- BGA/micro BGA
- Blind vias
- Buried vias
- Surface mount/thru-hole/chip (die)
- High-Density Interconnect (HDI)
Are you looking for help with your next PCB design? Contact us today to learn more about our capabilities or to consult with one of our engineering experts on your next project.