Printed circuit boards can be configured in several different ways according to the needs of the final product. Whether a small surface mount technology board is made for use in a handheld device or a multilayered board is designed for a larger machine, the options for construction are only limited by the ambition of the designer.
The problem with such variable options is that very few standard safety controls can be planned for every design. Each type of construction comes with its own design flaws and solutions for them.
(Henryphoto / pixabay)
One such solution works for multilayer boards and power planes, and here we will take an in-depth look at the best ways to utilize this construction method.
What are Power Plane PCBs?
The more layers you add to a PCB, the more power it will require to run. A simple single-layer or double-layered board can be easily accomplished with an average power source with a ground plane between them. However, the average power supply will not be sufficient for boards with more than two layers.
The common practice when building multilayer PCBs is to add pairs of layers each time. This is because an even number of layers provides greater stability to the board, reducing the risk of warping or twisting. This means that the power supply needed will be enough to cover two more layers for every extra layer added; even as few as four or six layers will drastically increase the power necessary to power the PCB.
For this reason, when building a PCB of four or more layers, a power plane is installed in place of a ground plane. A power plane is connected directly to the power supply and will provide an additional source of electricity to installed components. A trace is threaded through the board’s surface to connect directly between the power plane and the component, creating an alternate source of power to it.
Benefits of Power Planes
Compared to using a regular power supply through circuit traces, power planes offer a few benefits for multilayer boards. For a single- or double-layer board, a single circuit of traces will sufficiently power every component, but this will not work on four or more layers. The following benefits are provided by power planes:
- Better capacity for current – standard traces are limited in the amount of power they can carry, and the amount is limited the more is used. The entire surface is powered by a power plane simultaneously, and each component can be separately connected to it to draw power.
- Shorter return paths – vias drilled through the surface of each layer provide a short, direct path for the power to travel through. These shorter paths will improve power return while improving electromagnetic compatibility (EMC) performance, reducing the risk of damage or disruption caused by electromagnetic interference (EMI).
- Improved circuit decoupling – power place surfaces can act as a decoupling capacitor between PCB layers. The plane itself will decrease or prevent noise from passing between layers and causing disruption amongst parallel circuits.
Best Practices for Designing Power Planes
With the benefits of power planes in mind, we’ll now look at the best ways to utilize them in the designs of PCBs.
Ensure Proper Symmetry
As mentioned before, multilayer boards are built with pairs of layers as more are added. This is because the symmetry provided will increase the board’s strength and prevent potential serious damage.
For each pair of boards, it is best to provide a single power plane. This will ensure enough current goes to each layer. So, for a four-layered board, there should be two power planes.
Provide Multiple Domains
It stands to reason that a single-layer PCB will only require a single power source. All the components upon it will run from the same type of supply. As more layers are added, the need for multiple different types of power supply rises.
Fortunately, power planes allow you the freedom to provide these different types of power. By splitting the power plane into multiple domains, each domain provides the required power to each type of component.
When designing a multi-domain power plane, it is important to understand and follow the best practices for EMI/EMC construction, such as separating the different types of circuits used. This approach allows the designer to save space within the layout of the board but also has its risks. Multiple domains bring a higher risk of issues such as crosstalk and higher noise levels.
Use Cross-Team Layout Software and Tools
When it comes to PCB manufacturing, it is critical to use all available resources. This applies to designing multilayer boards with power planes.
Using layout software can help in a few different areas that will improve the overall performance of a PCB. The correct software will provide the best layer dimensions for building the most effective power planes. A strong component layout will further improve current flow and heat dissipation amongst chips and help mitigate or control the amount of EMI produced. Layout software can also help pick out the best components and materials to use in production and create the ideal sizes, numbers, and locations of vias to provide the best power routing.
The benefits of using design software can help reduce production time, errors, and costs across the board while ensuring that all power planes are put to the most effective use. With test solutions, the potential errors that may occur during the designing stages can be resolved before a board is even put into production. What’s more, PCB design software will also provide a series of virtual testing options to run simulations on these designs.
Conclusion
Power planes are a fantastic way to make more powerful and effective multilayer boards. Not only will they provide better power distribution and better current movement, but they can also help ensure larger machines can run better and stronger. Take the time to carefully consider the implementation of power planes and build towards a better production future.
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