How To Ground a Circuit Board: Different Ways To Place The Reference Layer

This article is about how to ground a circuit board.

A ground is the shared return path in a circuit that returns current to the source. Ground also functions as the voltage measurement reference point on different circuit sections. 

So it is a critical feature of any circuit and occupies a significant portion of any PCB. In this article, we’ll show you how to ground a circuit board and the grounding techniques to use. 

But first, here are the ground types you can find in PCBs.

Types of Grounds

You can have the following seven ground types in circuit boards.

Earth Ground

As the name suggests, this ground is a physical connection to the earth, usually via the power supply. It acts as a safe return path to drain excess current from the circuit.

Chassis Ground (Safety Ground)

A metal ground chassis usually creates a safe enclosure for the PCB. So it is an ideal safety measure. Also, most electronic components in a circuit board cannot connect to the earth-ground directly. So the chassis acts as an intermediary.

Signal Ground

Signal ground is a point where you can measure a signal’s voltage. Most boards with analog and digital signals have separate signal ground paths that connect to an internal ground plane.

Virtual Ground

A virtual ground does not connect to the ground plane. It is typical in negative feedback circuits on operational amplifier inverting ends.

Linking 0V to this non-inverting input will pull the 0V inverting inlet and hold the value constant through the feedback.

The ground creates an unstable node, so you cannot use it as a return path for other components.

AC Ground

An AC ground blocks DC by having a low impedance. It achieves this low impedance value by connecting a capacitor to the ground plane.

A radio decoupling capacitor

A radio decoupling capacitor

Floating Ground

Like virtual grounds, floating references don’t connect to the ground plane.

Instead, they arise from sizable reference conductors in isolated systems. Therefore the voltage on the conductors and the ground terminal is not known.

Sometimes, the unintentional system ground is a fault, but you can use it for safety.

The Importance of Circuit Board Grounding

Circuit board grounding has four primary benefits.

Voltage Recovery

Over 90% of a circuit board’s electrical components connect to the power net when operational. So their voltage appears on the ground net.

Boards with four layers or less must have wide traces, but those with over four layers must have a high-quality sheet ground plane.

This layer should create a reliable connection between the components and the ground.

Signal Recovery

Electromagnetic induction can cause electromagnetic interference when two signal traces have a parallel route.

This interference occurs because the signals lack a clear signal path.

A ground trace or plane creates a clear signal return path, preventing noise on other circuit parts.

Electrostatic discharge sparks on a radio frequency electronics component

Power Integrity

Circuit board components draw a lot of power, which can cause spikes.

Ground planes help smoothen these spikes, leading to better power integrity.

Minimizing Noise/Interference

Digital components or signals can create noise interference when shifting from low to high states or vice versa.

Ground planes can reduce or eliminate this noise when integrated into the circuit.

Circuit Board Grounding Techniques

There are four ways of creating the ground connection when designing or building the circuit board.

Ground Plane

A plane is a broad piece of something. So a ground plane is a large copper piece that returns current from different points on the PCB.

In most cases, it covers an entire layer, such as the bottom layer in a 2-layer circuit board.

But multilayer PCBs usually have an internal dedicated ground layer.

And since it covers a wide area, the plane doubles up as a heat sink to lower the board impedance.

The bottom layer of a PCB with a ground plane

The bottom layer of a PCB with a ground plane

But if it doesn’t cover an entire layer, ensure the ground plane has no closed rings to avoid electromagnetic interference.

Also, avoid placing traces between the return paths of two components, which will create a loop.

If using a chassis ground, avoid ground loops by placing ground section voids that link to the chassis.

These loops or closed rings act as inductors, making them capable of inducing voltage and current from external magnetic fields. 

Ground Vias

When dealing with multilayer boards, the ground planes in different layers connect using vias. These via holes give three benefits.

  • Minimize current/voltage-inducing ground loops.
  • Create a short return path via a low-impedance ground point
  • Enable ground plane access from anywhere on the board
Pads and vias on a PCB

Pads and vias on a PCB

Decoupling Capacitors

Connecting decoupling capacitors from the power to the ground trace eliminates interference between the two tracks.

Additionally, it reduces noise on the board and provides stable power to the integrated circuits.

Ground Connectors

High impedance in circuits can cause electrical current oscillations.

But multiple ground connectors reduce the high impedance, especially when connecting the board to another PCB.

How To Ground a Circuit Board

You can use one or more of these grounding solutions in your PCB.

Separate/Dedicated Ground Planes

A dedicated ground plane usually sits below the signal layer, allowing controlled impedance signal routing in striplines or microstrips.

So you can minimize crosstalk using dedicated ground planes for low and high-voltage board sections.

These planes should have separate connections to the power supply.

And if using a chassis ground around the ground plane, place a void to avoid creating a ground loop antenna.

If the electrical circuit returns to the wall outlet (earth ground), connect the ground plane to the chassis using a capacitor.

This decoupling capacitor isolates DC signals and creates a bypass for high-frequency AC noise.

But the capacitor should have high-voltage ratings and low ESR.

Here are some tips to use when designing the ground plane.

  • Ensure the plane has zero splits. Keep it uniform. And use ground fill to make the plane uniform.
  • Position this plane directly underneath the signal plane to shorten the return path.
  • Install separate grounds for regulated & unregulated DC and AC for isolation purposes.
  • Use stitching capacitors for signals changing the reference plane.
  • Avoid placing power planes on the board edges (causes interference).
  • When routing nets, avoid intersecting them.
  • Use a common ground on the board’s free spaces.
  • Ensure split planes have carefully placed power and ground nets to avoid blocking/ruining signal return paths.

Ground Traces (Prevents Ground Loops)

Ground loops occur when the board has several return paths with varying potentials.

So try to maintain the same ground voltage by linking component and connector ground pins independently to the ground.

And the best way to achieve this connection is using short traces or dedicated vias.

The design creates multi-point grounding that is suitable for high-frequency circuits.

PCB traces with vias

PCB traces with vias

This setup also requires thermal relief pads for linking through-hole components to any PCB plane.

The extra surface area conserves heat during soldering to create a solid bond while providing sufficient metal-to-metal contact.

However, all boards must have a shared ground where all return paths converge, usually a dedicated ground layer or chassis.

And the traces must be wide enough to reduce ground impedance and overheating in high-current circuit boards.

Also, maintain enough creepage distance between the tracks to avoid arcing in high-voltage boards.

You can use guard traces on both sides of sensitive signal lines and ground them on either end.

But these tracks are not ideal for high-density boards because they consume a lot of space.

Separate High and Low Voltage Areas (Galvanic Isolation)

Galvanic isolation is necessary when two circuit sections operate at different potential levels, and you must transfer a signal between them.

The goal is to prevent unwanted DC and AC coupling between the two sections.

For instance, with a step-up/step-down transformer, you must use capacitors, fuses, and EMI filters for power isolation.

You’ll also need hall sensors, optocouplers, and relays to exchange information.

An AC/DC power supply with a transformer on a PCB

An AC/DC power supply with a transformer on a PCB

Distinct Analog and Digital Sections

You can use either of these solutions when having separate digital and analog sections.

  • Tie down the grounds using zero-ohm resistors, net ties, or ferrite beads
  • Use a shared return path between the two

The latter is better because it ensures the drained current does not enter or interfere with the other plane.

And you can install analog-to-digital converters or other mixed-signal components in the center gap.

Analog-to-digital integrated circuits

Analog-to-digital integrated circuits

Ground Plane Vias with Via Stitching

As stated earlier, vias shorten the return path to the ground plane and minimize ground loops.

In multilayer boards, via-stitching at specific intervals shortens the return path further.

Generally, try placing ground vias at most ⅛ of the wavelength from the relevant conductor to avoid resonance.

Keep in mind that power planes near the PCB edge can cause interference.

But you can prevent this noise using 50-100 mil via stitching along the edge, which creates a Faraday’s cage.

However, the spacing can affect the board’s stability by causing depanelization and board breaking.

Other things to consider include: using ground grids on flex boards and via fencing on RF boards.

Use Decoupling Capacitors to Prevent Ground Bouncing/Decoupling

If using a power rail between several board components, active circuit components can create ringing or ground bounce effects.

The best way to solve this issue is to place a bypass capacitor near the power supply pin.

Connect these capacitors to the ground plane using short traces or separate vias to prevent inductance-causing daisy-chain ground connections.

Electrolytic decoupling radial capacitor

Ground Wires for Safe Running

Lastly, you can make high-voltage, high-current, and HDI boards safer by minimizing leakage currents using the following.

  • Grounding wires (creates a low-impedance path for return currents)
  • Surge and lightning protection (routing voltage spikes away from components and into the ground plane)

Wrap Up

As you can see, ground paths are critical in circuit boards because they help with the following.

  • Voltage & signal recovery
  • Noise reduction
  • Power integrity

So it is essential to know how to ground PCBs, and you can use the solutions explained above.

We hope the article has been insightful. But if you find the information overwhelming, contact us. We’ll be happy to help.