PCB Grounding Techniques
PCB Grounding is an unavoidable concept while designing a Printed Circuit Board and electric current. If you check out, every single equipment or circuit board has a ground and ensures proper functioning without causing any damage.
But what is grounding or a ground terminal?
A ground is a point of zero voltage which acts as a common return for electric current. Proper grounding is necessary is all circuits to maintain efficiency and keep up the performance. Proper routing and fitting of conductors, the use of differential signal management
and the use of field insulation methods regulates the undesired voltages.
Moving onto the techniques, there are various PCB grounding techniques and let us take a few approaches that are most commonly used in today's world.
1. Common Ground Plane: This is one of the most commonly used techniques and as the name suggests, it involves the use of a ground plane which is mostly a copper piece. It is made on the point that every region of the PCB that does not have a component or a trace. There are a few rules to be followed while grounding and will jump right into it.
It is always recommended to place the ground plane on the bottom and components on the top of the board. This way, we can avoid the creation of a ring of conductive material formed by the ground plane and thereby increase the susceptibility to EMI. As a preventive measure, the traces could be made as small as possible to avoid the formation of a conductive ring.
Sometimes the ground plane is added on both the sides of the board where one side is kept at the supply voltage and the other side being grounded.
2. Ground Plane Vias: Two ground planes are added on both sides of the PCB and are interconnected using vias at different places of the board. They are holes that connect each side and allows to access the ground plane from anywhere.
The vias mainly connect the components directly through low impedance to all of the circuit’s other ground points. The common practice adopted is most scenarios is placing ground vias at one-eighth of a wavelength. This is because a stub on a trace only starts to become an issue at one-eighth of a wavelength.
The vias of a PCB are insulated to minimize the length of return loops and the process is known as tenting. Carrying out this process enables the designer to eliminate ground loops as they directly connect the ground points connected through a low impedance.
3. Connector Grounds: There are multiple components in the PCB. The idea behind connector grounds is that all the connectors must be connected to the ground and the signal lines form a parallel connection. PCBs containing a single connector pin leading to the ground are
associated with impedance mismatch, a factor which contributes significantly to oscillations.
It is always ideal to use multiple ground pins to prevent the rise of resistance in connectors overtime.
To keep the signal level constant at all times, it should be ensured that the S pin is leading to the ground and pins of the connector are either in parallel or at right angles.
4. Decoupling: You might have figured out by now that there are multiple connectors and ICs in the PCB that work on power. Some of these grounds pins are used to connect them to the ground plane.
But let us hold that thought for a second and think about what decoupling defines. The process of implementing an Inductor - Capacitor network next to the IC to give a transient switching current is known as decoupling.
In between the ground and supply pins, there is decoupling capacitors to improve the functionality and enhance performance and can act as a storage device whenever necessary. They play a vital role in noise reduction generated by the power supplies and to provide an inductive path.
Much care must be taken while placing the decoupling capacitors and to keep it distributed across the board near the ICs. The number of decoupling capacitors must be chosen depending on the purpose and a combination of ESRs are also recommended.
So there they are!! You have taken a peek into the most common methods used for PCB grounding.
Bonus!! A few information be kept in mind while grounding.
#1 Make sure that all the connections are proper and no attachments are left unattended.
#2 There should be a common ground point!
#3 This time, the lesser the merrier. Yes, talking about the series vias.
#4 Know the currents and their flow.
#5 Keep it grounded. (Can be applied as a life hack too!)
Keeping all these in mind, start working!!