Notes for PCB Design Setting

1. Trace

This Gold Phoenix PCB Knowledge Center article explains practical PCB design setting considerations while keeping manufacturing constraints in view. When designing a PCB, it is important to consider not only the precision and ideal requirements of the design but also the manufacturing constraints. It is possible that the finished product differs from the original design.

Designers should consider fabrication-related constraints when defining trace width, spacing, via diameter, and copper thickness. Other factors such as the number of PCB layers, board thickness, board material, and surface plating should also be taken into account. It is possible that the finished product differs from the original design due to manufacturing limitations.

Regarding design precision, the minimum trace width and spacing and the minimum via diameter are among the most important specifications to consider. If the trace width in the design is too narrow, it may not be fabricated successfully. The trace and spacing precision will also affect whether the text and patterns in the silkscreen are clear. If the via diameter in the design is too small, a suitable drill may not be available. The minimum drill size can also impact the mechanical holes, mounting holes, and the precision of outline slotting.

In PCB design, for example, if the minimum trace and spacing is 4 mil, this means the trace width in the design must be more than 4 mil, and the space between traces must also be more than 4 mil. This defines the minimum trace and spacing. In actual design, traces need to be of different widths. For example, the power network trace should be wider than the signal trace.

These different requirements can be defined in the design rules. Different trace width values can be set for different nets, and the priority of rule applications can be set based on the importance of each net. The same applies to trace spacing — the electrical clearance between different nets can be defined in the rule page: Design → Rules → Electrical → Clearance.

There is a special situation. For high-density pin components, the clearance between pads will be very narrow, such as 6 mil. Even if it satisfies the technological requirement for minimum trace and spacing, it may not meet the design rule.

If the minimum safety clearance for the entire PCB is set to 8 mil, then the clearance of the component pads will apparently violate the rule. Violations will always be highlighted in green during rule checking or online editing. However, this type of violation does not need to be addressed. In older versions of design software, it was necessary to use the Query language to define a different safe spacing rule for the component and set it to high priority. In newer versions of software, it is much more convenient — simply check the option “Ignore Pad to Pad clearance within a footprint.”

2. Via

As a general design reference, the original guideline uses a minimum via diameter of 6 mil, a minimum via annular ring of 8 mil, and a minimum clearance between vias of 6 mil.

The minimum via diameter and minimum clearance between vias are very important design rule parameters and should be given careful attention.

3. Pad

4. Solder Mask

According to the original design guideline, the SMD solder mask opening should not be less than 0.1 mm (4 mil) on one side.

5. Silkscreen

The original guideline states that the width of the silkscreen should not be less than 6 mil.

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