Today, the world is so full of electronic devices that most people don’t realize how many printed circuit boards they encounter daily. Kitchen appliances, voice-activated home assistants, mobile devices, entertainment systems, toys, work-stations, and the family car are just a few examples. Providing the world with all of these electronics requires skilled manufacturers and precisely created printed circuit board designs. Yet many of these fundamental designs have frequent problems that delay or derail their manufacturing.
In this first of a multi-article series on circuit board problems, we will look at some of the common issues associated with a PCB design. Later articles will explore the different issues related to printed circuit boards in various aspects of their manufacturing. However, a circuit board begins with its design and layout. Therefore, here are some common printed circuit board problems in design to know to avoid manufacturing delays.
Common Problems before PCB Design Begins
Before circuit board design begins, designers should take some basic steps to ensure that the project can be completed successfully, for instance, management and scheduling. Time and resources have to be allocated for the project, and this includes a buffer for design changes or errors that require altering the schematic and the layout. Too often, PCB designers are pushed to their limits to get a project done, resulting in missed schedules, errors, or incomplete work.
Another area to focus on is the PCB design tools that will be used. Are your users proficient in the necessary tools? Do you have the appropriate CAD libraries in place? Are your company design and drafting standards incorporated into the tools to streamline the design process? These may seem like nit-picky points, but a design department will run more efficiently if all these pieces are in place before work begins. Now let’s look at six of the most common problems in PCB design that can impact manufacturing.
Six Common Printed Circuit Board Problems in Design
The six most common problems in PCB design include:
1. Component issues
We will examine component problems more in-depth in a later article in this series on common printed circuit board problems in this series. However, during the design phase, one of the main issues with components is choosing incorrect parts for their convenience. It can be straightforward for designers to reuse existing circuitry or choose a library part because it’s familiar. The problem is when those parts are no longer viable because of price, availability, or they have become obsolete. Designers need to keep their libraries current and check the components they are using to avoid this problem.
2. Physical parameters
The layout team often will go with a board outline, material selection, or layer stackup configuration because it’s familiar. But material availability and pricing can change, and the design requirements may favor a different substrate. Board outlines can also change or require changing due to manufacturing limitations. To avoid problems like these, it is always best to confirm the circuit board’s parameters with the manufacturer before the layout begins.
3. Part placement
PCB component footprints must be placed in a circuit board design to reduce or eliminate any manufacturability problems. This process is known as design for manufacturing, or DFM, and if ignored, can cause production yields to drop precipitously while overall costs skyrocket. Some of the DFM requirements that designers need to be aware of are the spacings between components, between components and the edge of the board, and between components and other board features. Enough room also needs to be left around testpoints to ensure that the board can be automatically tested. The placement of components that run hot should be considered to prevent thermal issues from impacting the board’s performance, and high-speed parts need to be placed for the best signal integrity performance.
4. Trace routing
One of the most common design problems is improper trace widths and spacing. Not only should designers work together with their manufacturers to determine the correct trace width and copper weight for their routing, but these values must be entered into the CAD design rules. A complete set of design rules and constraints will help avoid problems with controlled impedance routing, traces burning through due to insufficient copper for higher currents, poor signal integrity, and improper copper balancing on the board layers.
5. Power and ground planes
It is prevalent for PCB designers to treat their power delivery network as an afterthought or not give it the necessary consideration. However, the board may have noisy signal integrity problems and radiate undesirable EMI without an adequately designed ground plane. Again the answer is to work ahead with the manufacturer to determine the correct configuration and placement of the planes in the board layer stackup. It is also essential to design these planes so that signal return paths are not blocked and areas of different circuitry such as analog and ground do not interfere with each other.
6. Full system design
It’s common for designers to be so focused on their PCB design that they forget that their circuit board is often part of a larger system. This lack of integration can lead to future problems when all of the system components are assembled together. Wire harnesses may not match the corresponding connector on the board, switches and other human interfaces may not be accessible, and technicians won’t have the room they need for debugging and rework. Therefore it is imperative that engineers design for the entire system, and not just the PCB in front of them.
Now that we’ve seen some of the most common printed circuit board problems in design let’s check out some helpful resources.
Who to Turn to For PCB Design Resources
There are many resources out there that can help you overcome some of these common design problems. From online blogs like this one to industry design conferences, there is a plethora of information that you can get for answers to design-related questions. Another helpful resource is to work with the PCB contract manufacturer that will be building your circuit boards. These companies can usually provide engineering and design services in addition to component and manufacturing expertise to answer your design questions or provide additional design help.
At VSE, we have been helping our customers with design-specific questions for over 30 years. We provide electronics engineering and manufacturing services to customers within and beyond the San Francisco Bay Area. We can aid in all aspects of your design, from component selection to adequate testpoint coverage, so your design is production-ready.