7 Common PCB Process Design Mistakes to Avoid

PCB process design is not only about making a circuit work. It is about making the board manufacturable, assemblable, testable, and reliable in real production. Many designers focus on schematic correctness and software DRC results, but still run into low yield, assembly defects, and long-term reliability problems.

In daily engineering review, we often see the same process design mistakes repeated. The following seven issues are among the most common. Each one includes the problem, the risk, and the correct approach.

Mistake 1: Changing the Design Freely to Save Space Without Considering Production Capability

Many designers assume that if the design software passes the rule check, the board can be produced. To make the product smaller or fit a mechanical structure, they push the design to extreme limits.

This is a serious mistake. Every manufacturer has equipment and process limits. If the design is too aggressive, such as traces that are too thin or holes that are too small, production problems will appear. Etching defects may cause shorts, drilling may break tools, and the final yield may drop sharply. Rework cost increases, and in severe cases, an entire batch may be scrapped.

The correct approach is to confirm the manufacturer’s process capability before design. Ask for the minimum trace width, minimum hole size, minimum annular ring, and other critical limits. Do not pursue miniaturization blindly. Balance mechanical requirements with PCB manufacturability. If necessary, work with the mechanical engineer to optimize the structure.

For teams that need flexible production support from prototype to volume, PCB assembly services can help align design decisions with actual manufacturing capability.

Mistake 2: Using 90-Degree Right-Angle Traces and Assuming They Do Not Matter

Some designers believe that a right-angle trace is only a cosmetic issue and will not affect the circuit or production.

This is not correct. Right-angle traces create two major problems. First, during etching, chemicals can remain trapped at the right angle, which may corrode the copper over time. The trace may become thinner or even break. Second, right angles affect signal transmission. In high-speed circuits, they can cause signal reflection and increased interference, leading to product failures.

The correct approach is to use 45-degree angles or arcs for trace turns. Avoid right angles whenever possible. If space is limited, add a chamfer at the corner to reduce chemical residue and signal disturbance. Always review the layout for sharp-angle traces before release.

For complex designs, PCB design for manufacturing support can help identify these issues early in the layout stage.

Mistake 3: Using Default Software Pads Without Adjustment

Many designers use the default pad library in the design software for convenience, assuming it works for all components.

This is not correct. Default pads often do not consider actual placement accuracy and soldering requirements. For small components, incorrect pad dimensions can cause tombstoning, also known as the Manhattan effect. This leads to weak solder joints, poor contact, and intermittent failures in the field.

The correct approach is to adjust pad size and spacing according to the component datasheet and the manufacturer’s placement process. For high-power or high-frequency components, thermal management must also be considered. Add thermal pads and vias when necessary.

For projects that require both fabrication and assembly, PCB fabrication and assembly teams should review pad designs together before production.

Mistake 4: Choosing Surface Finish Only by Cost Without Considering the Application Environment

Some designers think surface finish is only for preventing copper oxidation and choose the cheapest option without considering whether the product will be used in a humid environment or a high-frequency circuit.

This is a major mistake. Different surface finishes perform very differently. For example, using cheap hot air solder leveling on a high-frequency circuit can degrade signal transmission. Using ordinary organic solderability preservative in a humid environment can cause oxidation and poor soldering, leading to early product failure.

The correct approach is to choose the surface finish based on the product’s application and requirements. For high-frequency circuits, choose immersion gold. For humid environments, choose immersion gold or nickel-palladium-gold. For ordinary low-frequency circuits, hot air solder leveling may be sufficient while balancing cost and quality.

For products that require additional protection, conformal coating can be considered after assembly to improve environmental resistance.

Mistake 5: Placing Vias Randomly and Treating Them Only as Layer Connections

Many designers think vias are only used to connect different layers and that size and position do not require much attention.

In reality, poor via design causes many problems. If the hole is too small or the wall is too thin, drilling may break the tool, copper plating may be unreliable, and layer-to-layer open circuits may occur. If a via is too close to a trace or pad, short circuits may happen. In high-speed circuits, vias also affect signal quality, and too many vias increase cost.

The correct approach is to define via dimensions according to production requirements. Do not make them too small or too large. Position vias away from trace corners and pad edges. For high-speed circuits, use blind or buried vias to reduce signal impact. Control the number of vias and avoid unnecessary placement.

For high-density and high-reliability products, PCB assembly partners can provide feedback on via design and stencil requirements.

Mistake 6: Relying Entirely on Automatic Routing Because It Seems Fast and Error-Free

Some designers believe automatic routing is efficient and error-free and can completely replace manual routing.

This is not true. Automatic routing follows algorithms and cannot consider every detail. It often creates redundant traces, insufficient spacing, and signal mismatches. For critical high-frequency signals and differential pairs, automatic routing cannot provide precise control, which affects transmission quality and leads to rework.

The correct approach is to use manual routing as the primary method and automatic routing as a supplement. Critical signals such as high-frequency, differential, and power traces must be routed manually. Ordinary low-frequency signals can use automatic routing as an aid. After routing, perform a manual review and correct any unreasonable areas.

For designs that must move quickly from concept to prototype, PCB assembly and prototyping support can help reduce iteration time.

Mistake 7: Focusing Only on the PCB Design Without Considering Production and Assembly

Many designers believe that as long as the board functions electrically, production and assembly convenience do not matter and can be adjusted later.

This is a mistake. If production and assembly are not considered during design, many problems will appear later. For example, if components are too close to the board edge, pick-and-place equipment may not reach them. If test points are not reserved, product testing becomes difficult. If silkscreen markings are unclear, workers may place components incorrectly, and yield will drop directly.

The correct approach is to consider production, assembly, and testing requirements during design. Keep components away from the board edge and reserve enough test points. Make silkscreen markings clear and accurate, consistent with the bill of materials and drawings. Communicate with production and assembly teams in advance to confirm that the design can be manufactured and assembled smoothly, avoiding later rework.

For turnkey projects, PCB assembly services can help coordinate fabrication, component procurement, assembly, and testing.

Conclusion

The core principle of PCB process design is that design must serve production. Avoiding these seven common mistakes can reduce detours, improve production yield, and increase product reliability. Whether you are designing or manufacturing, pay attention to details and communicate with relevant teams early. This is how to achieve better PCB process results.