PCB Design Steps Using KiCad

When designing a PCB with KiCad, the typical process generally follows these steps:

1. First, create the schematic in Eeschema.
2. Next, assign footprints to each component in the schematic.
3. Then, use Pcbnew to arrange and route the footprints, designing the actual PCB layout.

This is the general workflow for designing a PCB with KiCad.

Common Scenarios for Adding Pads in PCB Design

While following this workflow to design a PCB, there are many instances where you may need to add extra soldering pads.

Some common examples include:

• Adding a pad for a test point, such as an oscilloscope or multimeter probe, on the trace.
• Placing extra pads in case the component lead spacing is unknown at the design stage, allowing for flexibility in mounting different components.
• Designating a section of the PCB, such as an unused area, for a “universal” grid of pads to facilitate future modifications or prototyping.

These are just a few examples, and many other situations can arise where additional pads may be needed.

Traditional Method for Adding Pads in KiCad (Cumbersome Approach)

When adding pads in Pcbnew, the traditional method requires adding a corresponding component in Eeschema that represents the pad.

For instance, you might add a single-pin connector and assign it a footprint, such as a Soldering Pad footprint, to create the desired pad.

However, this method can be cumbersome, as you must add a new component every time you want to place a pad. This becomes especially impractical if you need to add dozens or even hundreds of pads, as you might in a “universal” PCB design.

Now, let’s explore a simpler and more efficient way to add pads directly within Pcbnew.

Adding Pads Easily in Pcbnew Using Vias

One simple solution is to use vias, which can be converted into pads.

Both vias and pads are essentially circular pads with drill holes in the center. The main difference is that vias are typically covered by resist layers on both the F.Cu and B.Cu layers, preventing soldering, whereas pads expose copper on both layers for soldering.

Let’s walk through the process.

In the example below, I have added three vias: GND, Vref, and +12V, enclosed in rectangular borders.

After placing the vias, you can expose the copper on the F.Cu or B.Cu layers by adding a mask around the via, effectively turning it into a solderable pad.

To expose the copper on the F.Cu layer, simply draw a circular mask in the F.Mask layer (as shown in the diagram below).

Once the mask is placed, the copper area that overlaps with the mask will be exposed, creating a usable solder pad (as shown below).

If needed, you can also add a mask on the B.Mask layer to create a solderable pad on the back side as well.

Here’s an example where the mask was slightly shifted on the F.Mask layer (right diagram), showing how the copper area also moves in sync with the mask.

This method helps visualize how the copper areas are exposed and how the F.Mask layer affects the design.

This technique offers several advantages, which we’ll discuss next.

Advantages of Converting Vias to Pads

Converting vias to pads offers numerous benefits:

Let’s look at the specific advantages:

First, vias can be placed anywhere on the PCB in Pcbnew, eliminating the need to add components in Eeschema just to create pads.

Vias are also flexible; you can edit their diameter and drill size, making them adaptable for different use cases. If you’re using vias as pads, it’s recommended to start with a larger via, then add the circular mask as described earlier.

Moreover, when you update footprints in Pcbnew, footprints that are not present in Eeschema are automatically removed. However, vias are not automatically deleted, offering a more stable design environment.

This technique allows you to freely add solder pads anywhere on the PCB. If you want to add a large number of pads, such as in a universal grid pattern, you can simply copy and paste the via-mask setup as needed.

Overall, this method is highly recommended for its ease of use and flexibility in PCB design.

We highly encourage you to give this method a try!

For any questions regarding PCB design or assembly, feel free to contact me at info@wellcircuits.com.