10 Ways To Improve PCB Design For Manufacture

2. Add Fiducial Markers

Fiducial markers are tiny copper dots enabling accurate alignment on the pick and place machine. At least 3
fiducial markers need to be placed on the edge of the PCB or tooling strips for precise alignment and placement.
These are called global fiducials.

If your PCB is considerably large and there are small-pitched (< 1.0mm) SMT ICs, you’ll need to add local
fiducial markers diagonally along the edge of the component’s footprint.

3. Precise and Visible Component Designators

Do not underestimate the importance of component designators regardless of whether the PCB is manually or
machine assembled. Component designators aid the assembly process and are equally important for rework or
repair.

Ensure that component designators are of the right dimension. They should also be placed systematically and near
the respective components. You don’t want assemblers having trouble matching components to the designators or
technicians fixing the wrong parts.

4. Standardized IC Orientation

All semiconductor ICs have an orientation mark. It could be a printed dot on pin one or a notch on the package.
Either way, it’s essential to keep all ICs aligned in the same direction. Doing so prevents confusion when
assembling the ICs on the PCB and also improves efficiency.

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5. Single Side Component Placement (If Possible)

Component placement can determine the complexity of the assembly process and hence, production cost. Sometimes,
it’s tempting to reduce board size by placing components on both sides of the PCB.

However, doing so means doubling the component placement process, including producing two solder paste stencils.
By populating all the components on the same surface, you’ll enjoy a noticeable reduction in the assembly cost
per unit.

7. Avoid Via In Pads

This is another classic DFM issue that happens when designers attempt to minimize PCB size. It’s common for SMT
ICs to be fanned out with vias. However, shifting the via to an overlapping position with the pad brews trouble.
It leads to a weakened solder joint, which affects the mechanical and electrical stability of the component.

8. Ensure Sufficient Annular Ring Size

Whether it’s a through-hole pad or via, they go through the same fabrication process. Both require a minimum
annular ring size to prevent drilling complications. For example, the drilling process may not be 100% accurate,
and an undersized annular ring may result in the hole overlapping with an adjacent conductive trace.

Preferably, you’ll want to have an annular ring size of at least 6 mil.

9. Prevent Acid Traps

The negative effect of acid traps only materializes after a while. An acid trap is caused by awkward copper
geometry that results in the entrapped etching solution. This is often the case when you have narrow angled
(<90°) copper traces, which prevents the etching solution from being properly washed off.

While some manufacturers have adopted alkaline etching, it’s still a good DFM practice for your design to ensure
traces are bent at 45°.

10. Check For Copper Slivers

Copper slivers are tiny strips of copper extending from a copper pour and forming a connection with a via or
pad. They are commonly seen in ground planes where thin strips of copper join ground pads to a large polygon
pour.

You’ll want to run a check for copper slivers and increase their size as the etching process may remove
overly-thin copper from the PCB. This results in disconnectivity between the pads and the larger copper plane.