For circuit board designers, manufacturers, test engineers and technicians, symbols and abbreviations help transfer necessary circuit data. One of the most well-known is the ground symbol. Actually, there are several ground symbols that signify various types of grounding. And the corresponding PCB grounding techniques that you utilize for your boards are important.
Why Is Your Grounding Technique So Important?
The short answer to this question is inherent in Kirchoff’s current (1st) law that says the sum of currents leaving a node must equal the sum of currents entering it. For this to be true, there must be a path by which a current can travel to and from a point of origin. Ground provides that path. Without this closed path, electrical and electronic circuits cannot operate.
PCB Grounding Types and Techniques
Today, many PCBAs are small and densely packed with components—and may contain complex routing schemes. Consequently, boards are multisignal and often require one or more of the types of ground listed below.
PCB Ground Types
- Signal ground
All circuit boards have signal ground, which is necessary for propagation between components and with external circuitry. Signal transmission may be single-ended or differential; signal types may be RF (analog), digital or DC. Their grounds, as well as circuitry, should be isolated as much as possible from other types to prevent noise and signal integrity issues.
- Power ground
Power is also a requirement for all electronic boards; therefore, a power ground is necessary. Typically, power is DC and must be grounded separately from signals.
- Protection ground
Some boards, especially high-voltage power supplies, must provide a means of dissipating unwanted energy to protect components and circuits. This is where protective grounds are utilized.
- Virtual ground
Virtual ground is a ground that does not connect to an actual earth ground. These are intentional in some cases (e.g., op amp circuits) to provide a reliable reference.
To accommodate the ground types listed above, three basic PCB grounding techniques are employed on circuit boards.
The Engineer's Guide to PCBA Manufacturing Complexity
PCB Grounding Techniques
- Ground plane(s)
Single-layer boards use a dedicated area or space for grounding. This can be helpful for thermal distribution.
- Ground layer(s)
This is the common method of using vias to connect to a dedicated copper plane in the stackup for multilayer PCBAs.
- Ground trace(s)
Here all grounds are connected to the same trace(s), providing an extended ground potential.
Because selecting the best grounding technique for your design is not always easy, a set of guidelines
can be helpful.
The Do’s and Don’ts of PCB Grounding Techniques
Although there is no single magic PCB grounding technique that should be applied to all designs, good practices—including the do’s and don’ts listed below—can guide you to the best grounding solution for your specific board layout.
PCB Grounding Technique Don’ts
🆇 Don’t create ground loops.
🆇 Don’t use star grounds, unless absolutely necessary.
🆇 Don’t stack ground layers next to each other.
🆇 Don’t use ground traces for different signal types.
PCB Grounding Technique Do’s
Do isolate the ground planes for different signal types.
Do use separate ground layers for different signal types, if possible.
Do use decoupling capacitors between power pins and ground layer.
Do keep ground traces as short as possible.
Following the guidelines above will aid you in devising the best PCB grounding technique for your specific case. However, these must be applied in conjunction with your CM’s DFM and DFA rules to optimize your design for operation and manufacturability.
Tempo Automation leads the industry in building fast, high-quality PCBA prototyping and on-demand manufacturing. Our software-based digital thread process can catch grounding issues during DFM and institute design changes for faster bringup. This means less iterations, getting your product to market faster.
To help you get started on the best path, we furnish information for your DFM checks and enable you to easily view and download DRC files. If you’re an Altium Designer or Cadence Allegro user, you can simply add these files to your PCB design software. For Mentor Pads or other design packages, we furnish DRC information in other CAD formats and Excel.
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