Ground noise is a blanket term for many types of signal interference that can occur on a PCB and all of those interference types can affect how a PCB works.
Ground noise can create signal integrity problems and performance problems that can eventually cause PCB failures.
A strategy for creating PCBs with a new type of substrate and copper connectors can dramatically reduce the amount of noise and electrical crosstalk.
PCB functionality depends on many different factors, including physical layout, materials used, and stress on components over time. Electrical interference between PCB components, also known as ground noise, can have a wide range of undesirable consequences during a PCB’s operation. These issues include loss of signal integrity, unexpected thermal variations, and component failures. Therefore, reducing ground noise is a primary concern for PCB designers. Read on for an in-depth discussion on how to reduce ground noise.
What is Ground Noise?
Ground noise goes by many names, including electrical interference and crosstalk. Circuits in a PCB rely on a certain amount of current and voltage to function properly. This means that every circuit must have the appropriate amount of power, and that power must be routed to the correct place. If unintentional connections happen between circuits, it can cause power to spill between circuits in unexpected ways, resulting in ground noise.
Analyzing Ground Noise
Analyzing ground noise, especially in high-speed PCBs, is critical to ensuring a PCB works properly. Although complex PCBs with many circuits are more prone to ground noise, even simple circuit layouts can generate noise if not designed correctly. PCB design software gives designers a concrete measure of how much ground noise their PCB generates using noise figures. Noise figures demonstrate how much ground noise comes from different sources, such as unintentional connections between traces or thermal noise.
The layout and energy demands of a PCB often mean that different PCBs have different sources of problematic ground noise. For example, long traces are more likely to have unintentional connections and high-power PCBs are more likely to have thermal problems. Reducing ground noise to zero is functionally impossible since there is always some noise from expected sources, however, it can be minimized.
The Importance of Learning How to Reduce Ground Noise
Designing a PCB with minimal ground noise ensures that the signal integrity of its circuits remains reliable. A loss in signal integrity can cause multiple PCB problems, from shorts to emissions of radiation. These problems build upon each other creating a cascading effect that increases ground noise over time. The closer two circuits are, the more likely they are to generate crosstalk between them when users apply current to a PCB. Simple geometry can often fix crosstalk problems like this.
Although reducing ground noise is only one part of ensuring high performance in PCBs, lowering noise is an effective way to circumvent nasty runtime problems like board failures. Performance problems can also show up as slow response times in digital networks, data loss, or spikes in power consumption.
Choose PCB Materials Carefully to Reduce Ground Noise
Different materials have different conductivities, so using a different combination of materials is one way to reduce ground noise. When planning the best way to reduce ground noise, it is important to note that there are two key material types in a PCB that influence ground noise the most: the substrate in which components are placed and the metal used for conductive traces.
A well-constructed PCB should have a substrate that is a strong insulator and traces that are highly conductive. The most common combination of substrate and traces in PCBs is glass epoxy and copper. Since glass epoxy is an insulator, it does a good job keeping current where it should be within copper traces in general applications.
High-speed and high-frequency PCBs are a challenge, however, because they naturally generate a lot of ground noise. This isn’t the materials’ fault; the design of PCBs that handle large amounts of current can strain even the strongest insulators and conductors. The materials often need to be structured differently than on other PCBs.
New models involving single-ended microstrips allow copper traces to function with an impedance that is lower than normal, increasing their conductivity and reducing ground noise overall. The highly conductive copper traces reduce multiple types of ground noise and crosstalk at once, increasing signal integrity and reliability in high-stress situations.
Since learning how to reduce ground noise can make such a positive impact on PCB functionality, designers should choose PCB analysis software that keeps this important concern in mind. The PCB Design and Analysis overview page at Cadence Design Systems provides tools ideal for analyzing PCB designs, including the Allegro PCB Editor. You can also use InspectAR to accurately assess and improve PCBs using augmented reality and intuitive interaction. Inspecting, debugging, reworking, and assembling PCBs has never been faster or easier.
If you’re looking to learn more about how Cadence has the solution for you, talk to us and our team of experts.