Designing a PCB for the first time – or even the tenth time – comes with a learning curve that no amount of reading fully prepares you for. Some lessons only sink in after you’ve ordered a batch of boards, waited two weeks for them to arrive, and discovered that something fundamental went wrong. The good news is that most common PCB design mistakes are well-documented, entirely avoidable, and a lot less painful to learn about before you hit submit on that Gerber upload.
Here are the mistakes that catch designers out most often, and how to avoid them.
Ignoring the Manufacturer’s Design Rules
Every PCB manufacturer publishes a set of design rules – minimum trace widths, minimum spacing, minimum drill sizes, copper-to-edge clearances, and so on. These aren’t suggestions. They’re the boundaries of what that manufacturer can reliably produce.
Designing outside those rules is one of the most common and easily avoided mistakes in PCB design. A trace that’s slightly narrower than the minimum might make it through fabrication fine, or it might not – and at that point you’ve paid for boards you can’t use and lost whatever time was in your lead time.
Before you start laying out your board, download your manufacturer’s design rule file (DRC file) and load it into your EDA software. Run the design rule check before you generate Gerbers, not after. Make it a habit to check the manufacturer’s capabilities page any time you’re doing something non-standard – unusual layer counts, fine-pitch components, or tight tolerances all warrant a quick check.
Poor Ground Plane Design
The ground plane is one of the most important elements of a well-performing PCB, and it’s also one of the most commonly mishandled – especially by designers coming from schematic-first backgrounds who haven’t fully internalised how much the physical layout matters.
The most common ground plane mistake is splits and interruptions. A ground plane that looks solid in your layout software but has traces routed through it, cutouts in the wrong places, or incomplete copper pours can behave very differently from a truly solid plane. High-frequency return currents follow the path of least inductance – which on a solid ground plane means directly beneath the signal trace. Force those return currents to take a longer route around an interruption and you create a loop that radiates noise and degrades signal integrity.
On 2 layer boards, use a ground pour on the bottom layer and stitch it together with vias. On 4 layer boards, dedicate an entire inner layer to ground and keep it as uninterrupted as possible. Route signals over the ground plane, not through it.
Not Decoupling Power Pins Properly
Every IC on your board needs decoupling capacitors placed close to its power pins – and close really does mean close. The job of a decoupling capacitor is to supply instantaneous current to the IC when it switches, compensating for the inductance of the power trace between the capacitor and the pin. If the capacitor is on the other side of the board connected by a long trace, it can’t do that job effectively.
The rule of thumb is to place decoupling caps as close to the power pin as physically possible, with the shortest possible trace between the cap and the pin. Via-in-pad or placing the cap immediately adjacent to the pin with the via after it – not between the cap and the pin – is the right approach for high-speed designs.
Use the values recommended in the IC’s datasheet. A 100nF ceramic capacitor handles high-frequency transients well; a larger bulk capacitor (10µF or more) nearby handles lower-frequency demands. Many designs use both.
Trace Width and Current Capacity Mistakes
Traces carry current, and current generates heat. A trace that’s too narrow for the current it carries will heat up, potentially to the point of failure – and it can do so gradually enough that the board appears to work fine initially before problems develop under load.
This is particularly common on power traces that designers treat as just another signal connection. Use an online trace width calculator or the IPC-2221 standard to work out the minimum trace width for the current you expect, with a safety margin. For anything carrying more than a few hundred milliamps, verify the trace width explicitly rather than eyeballing it.
The environment matters too. A board running in an enclosed, poorly ventilated enclosure will run hotter than one in open air, which means trace temperature rises faster under the same current load. Factor that in.
Silkscreen Over Pads
This one seems minor but causes real assembly headaches. Silkscreen ink printed over solder pads can interfere with soldering – either preventing solder from wetting the pad properly or creating a bump that stops a component from sitting flush. Most EDA tools will flag silkscreen-over-pad violations in the DRC, but not all do by default.
Check your silkscreen layer carefully before generating Gerbers, particularly around fine-pitch components where reference designators often get pushed close to pads. If a label won’t fit without overlapping a pad, move it, shrink it, or drop it entirely. A missing reference designator is a minor inconvenience. A pad that won’t solder properly is a manufacturing defect.
Incorrect Footprints
Incorrect or mismatched component footprints are one of the most frustrating mistakes because they’re only discovered when you have physical boards in hand and components that don’t fit.
Always verify footprints against the actual component datasheet – not just the manufacturer’s suggested land pattern in the part library, which may be outdated or adapted from a different version of the component. Pay particular attention to pin pitch, pad size, courtyard dimensions, and the orientation of pin 1 on polarised or asymmetric packages.
For critical components, order the physical part before you finalise the board layout and check the footprint against it with a ruler or calipers if you have any doubt. An extra day of verification before you order saves you a week of waiting for a respin.
Missing or Incorrect Net Ties
Net tie errors – connections that are missing from the schematic and therefore absent from the PCB, or connections that are present on the schematic but wrong – are insidious because they often don’t trigger obvious errors during DRC. The board fabricates and assembles fine and then doesn’t work, which sends you into a debugging spiral before you eventually discover the schematic error.
Review your schematic carefully before moving to layout. Check power and ground connections on every component – missing power pins on ICs are a particularly common source of this problem, especially with multi-part schematic symbols where the power pins are on a separate hidden unit. Make sure every net that should be connected is connected, and that no unintended connections exist.
Not Leaving Enough Clearance for Manufacturing and Assembly
Minimum clearances in PCB design aren’t just about electrical isolation – they’re also about whether a board can be physically manufactured and assembled reliably.
Components placed too close to the board edge can be damaged during depanelisation. Components placed too close to each other may be unreachable by standard pick-and-place nozzles or soldering equipment. Vias placed too close to SMD pads can wick solder away from the pad during reflow. Tall through-hole components placed near SMD components on the same side can shadow nearby pads from solder paste stencil contact.
If you’re planning to have your board assembled professionally, check your assembly house’s courtyard clearance requirements and design to them. If you’re hand-soldering, think practically about whether you’ll actually be able to get a soldering iron tip to each joint without disturbing adjacent components.
Skipping the Design Review
The single most reliably mistake-catching step in PCB design is also the one most commonly skipped when schedules are tight – a proper design review before ordering.
Step away from the design for at least a day, then come back and go through it systematically. Check the schematic against your requirements. Run the DRC. Review the layout visually layer by layer. Check every footprint against its datasheet. Verify power and ground connections. Look at the board in 3D if your EDA tool supports it.
Better still, have someone else review it. A fresh pair of eyes catches things the original designer’s brain has learned to overlook. This is true whether you’re a first-time hobbyist or an experienced engineer – familiarity with your own design is a genuine blind spot.
The Bottom Line
Most PCB design mistakes come down to one of two things – moving too fast and skipping verification steps, or not fully understanding how the physical board will behave compared to the schematic. Both are fixable.
Slow down at the critical checkpoints. Load the manufacturer’s design rules before you start. Verify footprints against datasheets. Check your ground plane, your decoupling, and your trace widths. Do a thorough review before you order. The boards that come back working first time aren’t lucky – they’re the result of a process that catches problems on screen rather than in hardware.
Looking for more information about PCB’s? Take a look at this in-depth PCB Glossary.
