2-Layer vs. 4-Layer Printed Circuit Boards: What’s the Difference?
To understand the differences between 2-layer and 4-layer printed circuit boards, let's first consider what printed circuit boards are made of and how they function.
Circuit boards typically consist of an insulating material called a substrate and a thin layer of copper. A chemical etching process separates the copper layer into circuit traces.
This allows the components of the circuit to be electrically linked. In most cases, the circuit pattern and components that a printed circuit board is expected to carry are known before the patterns are printed.
Components are usually soldered to the board.
Additionally, bare boards and prototyping boards, which are not customized to a particular circuit, are available. Printed circuit boards may also include a protective coating to prevent corrosion of the copper layer and minimize the risk of solder shorts.
In a printed circuit board, what is a layer?
Engineers usually refer to ‘layers’ as the copper layers on a printed circuit board. There are always two layers on a printed circuit board. You will need to increase the layer count by two if your board is more complex and thus requires more electricity to flow through it. Layers are typically added in groups of two, so if 4 layers are not enough, your board will need 6. Most boards have between 4 and 8 layers of copper.
Circuit Boards Consisting of a Single-Layer
The single-layer PCB is used in simple applications, such as printers, cameras and power supplies. Their low cost makes them ideal for mass production. A single-layer printed circuit board only has one conductive layer, so its components are spread out more.
Printed Circuit Board With Two Layers (Double-Sided)
Two copper layers are present on a 2-layer printed circuit board. The copper layers on double-sided boards are sandwiched between the two substrate materials in this order:
- Solder mask| copper layer | core | copper layer | solder mask
Components on both sides of double-sided printed circuit boards can be mechanically supported and electrically connected. There are copper-lined holes in the board referred to as vias. This lets you connect circuits on one side of the board to circuits on the other. You can create high-density circuit boards using this feature.
Providing a ground grid on a 2-layer PCB greatly reduces the potential for electrical noise. There is a small price difference between double-sided and single-sided PCBs, plus they offer more space for components and are easier to route than single-sided boards.
A 4-Layer Printed Circuit Board
Four copper layers are found on 4-layer printed circuit boards. They are laminated together with alternating substrate layers. 4-layer printed circuit boards feature four layers of copper. These layers are laminated together with alternating layers of substrates. A 4-layer printed circuit board comprises, in order:
- Solder mask | copper layer | substrate | copper layer | substrate | copper layer | substrate | copper layer | solder mask
Signal layers are on top and bottom, and ground and supply planes are on the inner two layers. The fourth layer also includes vias. In circuits with RF components, ground and supply layers prevent electromagnetic interference (EMI). As well as providing a low resistance power supply, it also provides a short return signal path and reduces loop impedance.
How to Choose Between 2-Layer and 4-Layer Printed Circuit Boards
Printed circuit boards require a certain number of layers based on the complexity of your circuit. We strongly recommend 4-layer printed circuit boards for the complex circuitry that incorporates RF circuitry, switched-mode power supplies, long digital buses and other complex components and connections. For these kinds of circuits, 2-layer boards would cause excessive radiation and interference, as well as compromising the signal integrity. Printed circuit boards with two layers are recommended for simple circuits.
The Density of Circuits
Both 2-layer and 4-layer printed circuit boards offer equivalent mounting space since components can be mounted on either side. If circuit density is the only factor, any one of them would suffice.
In addition to their functionality, 4-layer printed circuit boards are more expensive than 2-layer boards. In particular, hobby and DIY projects have seen a significant increase in price. Therefore, if budget is an issue, go for 2-layer boards, unless your board requires complex circuitry. You should consider all of these factors before choosing the type of printed circuit board for your project.
When designing a PCB, you should also consider:
- Minimizing space requirements while maximizing functionality
- The number of layers on your printed circuit board (the higher the layer count, the more durable the PCB)
- Cost and affordability of both the PCB itself and your finished product
- Manufacturing turnaround time
Comparing the cost and functionality of 2-layer and 4-layer PCB designs can help you decide which design to use. It’s often difficult to know exactly which option is best, and creating multiple designs will help you discern the differences.
2-Layer PCB Advantages and Disadvantages
The cost difference between a double-sided PCB and a 4-layer PCB can be considerable depending on your anticipated order volume. Getting a printed circuit board faster requires simple design and production. The more simple your design, the less vulnerable it is to costly errors in manufacturing or design. It is inherently easier to repair double-sided printed circuit boards than more complex 4-layer PCBs in certain applications.
High volume - Eliminating unnecessary layers is crucial to any project that involves mass production. High-volume orders usually require 2-layer boards to maximize manufacturing speed, cost and efficiency.
Smaller lead times - Often needed to quickly make prototypes for large and small projects. Due to their fast production time, 2-layer printed circuit boards have an edge over other multilayer boards.
Choosing double-sided circuit boards can often mean sacrificing some bells and whistles. In a 4-layer PCB, there is more space and options for routing components, whereas a 2-layer PCB is typically simple and smaller design.
Low Operating Capacity and Slower Speed -The more layers, the faster your board will perform. Your application may not allow you to get the necessary speed and capacity with just two layers. By going from two layers to four layers, the speed and computing capacity are greatly increased.
Double-sided PCBs are usually quite large and heavy in comparison to 4-layer printed circuit boards, due to the extra layers required for components and leads. Adding more layers to a printed circuit board is often the best choice when limited space.
Should you choose a 2-layer or 4-layer circuit board?
Despite their differences in functionality, both 2-layer and 4-layer printed circuit boards are beneficial for various types of projects.
As a result, the choice between a 2-layer and a 4-layer board is largely determined by the specifications of your project and the complexity of the circuit, as well as your budget.