In electronics, the use of Printed Circuit Boards (PCBs) is vitally important because they act as the platforms for almost all electronics. In power electronics applications, PCB stackup decides the performance, reliability and thermal issues of the power circuit. While multi-layer PCBs are common in complex designs, many power electronics applications can be adequately served by a more cost-effective, efficient solution: the 2-layer PCB. A 2-layer PCB has just adequate flexibility and design potential as a printed circuit board to accommodate low to medium power needs, depending on how both signal and power planes are routed, thermal issues, and EMI.
In this article, we will consider the most utilized basic structure of the 2 layer PCB stackup for power PCB and discuss its benefits and major specifications to achieve the desired efficiency of power electronic devices.
What is a 2 Layer PCB Stackup for Power PCB?
A 2 layer PCB stackup is a combination of two layers of copper separated by a dielectric material. They are generally called the upper layer and lower layer with dielectric material separating them. The stackup can be optimized for both power and signal routing as needed for different power systems.
Basic Structure of a 2 Layer PCB Stackup for Power PCB
- Top Layer (Copper Layer): Power and signal trace in the two layer PCB stackup comprise the bulk of the top layer that sports copper traces and pads and large copper planes. This layer can be used for high-current power plane, high-speed signal routing and component positioning
- Dielectric Core (Substrate): The heart of the standard 2 layer PCB stackup is a dielectric material, which in most cases is FR4, this acts as the insulating region between the copper layers. It is possible to select the thickness and type of substrate that will be appropriate from the thermal and electrical point of view.
- Bottom Layer (Copper Layer): The bottom layer is also engraved with copper traces and is most commonly utilized for the ground plane, power net along other signal layers.
- Solder Mask: The upper and lower layers of copper are covered with a layer of solder intended to shield the copper from damage. This layer protects copper from oxidation and during the soldering process keeps only those parts of Copper that are to be used for mounting components.
- Silkscreen: The silkscreen is used to mark the PCB to write the names of the components, logos of the company etc.
The most common power two layer PCB stackup integrates the top layer to accommodate signal traces and power layers while the bottom layer is used to provide a ground plane or extra power plane. This basic structure offers enough flexibility to direct both power and signal lines appropriately.
Key Benefits of a 2 Layer PCB
1. Cost-Effectiveness
A 2-layer PCB is cheaper to produce when compared to multi-layer boards due to the lack of many layers of copper and the general complex procedures. This makes it a favourable power electronic component in applications that are sensitive to cost and in products that are produced in large quantities.
2. Simple Design Process
Designing a 2 layer PCB stackup is easy compared to other circuits with more layers where many more design rules have to be followed. Due to this, there is considerable ease when it comes to designing and redesigning to arrive at the final product faster.
3. Adequate for Low-to-Medium Power Applications
In many low to medium-power applications, it is possible to get enough routing space in the two layer PCB stackup to handle the required current and voltage levels without excessive heat buildup or signal interference
4. Flexibility in Routing
Nevertheless, compared to a Multilayer PCB, even a two-layer PCB can route power, grounds and signal paths with some degree of freedom. At least where the arrangements of space are concerned, it can be made device-specific and channelled to allow efficient power distribution and offer protection from noise.
Configurations of Standard 2 Layer PCB Stackup
Power PCB design for the two-layer PCB concerns power and ground plane layering, signal integrity, and thermal management. Below are the most common stack-up configurations:
1. Power on-Top-layer, Ground on-Bottom-layer
This is one of the most popular standard 2 layer PCB stackup layout styles used in power PCBs, although it is more used in low-power mode circuits.
- Top Layer (Power Plane and Signals): It further pointed out that in this instantiation of the structure, the upper layer is mainly reserved for power traces as well as signals. Copper lines called copper traces bear high currents, and special attention is paid while placing power devices such as voltage regulators, inductors, or power transistors.
- Bottom Layer (Ground Plane): As for the 2 layer PCB stackup, the whole layer is employed as the ground plane. This approach makes PTH and SMT easier for packed components, cuts EMI, and enhances signal integrity because of improved signal ground return path.
Benefits :
- Reduced Noise and EMI: An arrangement for a good tough ground plane eliminates the influence of electromagnetic interferences and also works as a reference area that decreases noise. It’s an essential part of the configuration concerning the two layer PCB stackup.
- Efficient Power Distribution: Designers make wide traces or copper pours on the top layer of the 2 layer PCB stackup so that power can be delivered to the entire component without much voltage drop or heat production.
- Thermal Management: The large ground copper areas on both layers of two layer PCB stackup contribute to heat removal of power dissipation high current components.
2 . Split Power and Ground on Both Layers
Some of the standard 2 layer PCB stackup designs have power and grounds in both layers making the routing easier and minimizing the use of vias.
- Top Layer (Power and Signals): The top layer of 2 layer PCB stackup may also include both power and signal traces as shown in the figure below. Copper pours are used to distribute power, but for routing signals, only smaller parts of the layer are provided
- Bottom Layer (Ground and Power): An additional layer of 2 layer stackup can be applied for the second layer of the ground as well as any additional power rail needed in the design of the circuit. It also means that the high current power routes and signal lines can be routed separately hence minimizing interferences.
Benefits:
- Reduced Vias: When power and ground are separated through both layers in the 2 layer PCB stackup, fewer vias are needed to join different parts which result in a cheaper and more manageable product.
- Improved Routing Flexibility: This configuration concerning the two layer PCB stackup provides greater freedom in the path that complex circuits can follow, as power and ground planes can be further separated on both sides of the plane.
3. Signal Routing with Power Planes on Both Layers
While many signals run parallel on a single operating layer, designs with heavy signal interconnection like mixed-signal or power control circuits are employed on both layers; the upper layer of two layer PCB stackup acts as a gesture to the lower layer which acts as a signal distribution or power distribution layer.
- Top Layer (Signals and Power): The upper routing layer of standard 2 layer PCB stackup is mainly used for signal routing, but power routing is also done where needed. Therefore the design becomes critical to manage and crosstalk, signal integrity problems are likely to occur during high-speed transmission.
- Bottom Layer (Ground and Power): The bottom layer of two layer PCB stackup for power PCB is subdivided into a ground plane for signal flow and supplementary power-layering as necessary. Some sensitive signal lines are located a reasonable distance from the noisy power traces.
Benefits:
- Better Signal Integrity: One should avoid having signal lines near the power traces especially where the frequency content of a design is going to be high when designing the 2 layer stackup.
- Reduced EMI: Since the first layer of this standard 2 layer PCB stackup is the ground plane, it reduces EMI and gives sensitive signals a firm reference point.
Conclusion
A 2 layer PCB stackup is one of the most economical solutions in many power electronics applications as it affords flexibility in routing, heat dissipation, and low to medium-power applications. Even though some power PCB design methods have been known to be challenging, following these approaches to copper pours, wide traces, and proper grounding helps the designers develop more effective circuits.
It should also be noted that there are several common stackup configurations used in system design, with most designers avoiding running power and ground planes on the same layer, using wide traces for high current paths, and providing adequate thermal management via copper pours and thermal via. When employing these strategies, a 2 layer PCB stackup design can elicit a high level of performance for different micro and power electronics devices.
