What is the difference between 2-layer and 4-layer PCB?

By Mer-Mar Electronics Date posted: Last updated: November 12, 2022
2 layer vs 4 layer pcb

When it comes to efficacy of circuit boards, a number of parameters become important. These range from signal integrity to lack of interference, from complexity of design to cost. While PCBs can range from 2 to multiple layers, each of these come with their own set of strengths. Let us analyze 2-layer vs 4-layer PCB on several parameters of efficiency and efficacy.

2-Layer VS 4-layer PCB

2-Layer PCBs also referred to as double-sided boards have two copper layers with a substrate material sandwiched between them.

The advantage of multilayer PCBs; specially 2-layer PCBs is that they can connect components on both sides. They have holes, also referred to as vias that help connect the circuits. It also has room for a ground grid. In turn, this goes a long way in reducing electrical noise.

4-Layer PCBs have four layers of copper, with the top & bottom layers being signal layers and the inner layers being ground and supply planes. The 4-layer boards also have vias. With the presence of the ground & supply layers, electromagnetic interference is greatly reduced. What it also offers is a short return signal path.

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1. Difference in terms of stack-up

Largely this comprises of the top layer that is referred to as a signal layer. The layer is 0.0014-inch thick and is made of copper material amounting to about 1 oz.

The 4-layer PCB comprises of the top and bottom layer as also two inner layers. The top or the signal layer made of copper which is 0.0014 inch in width, is followed by a prepeg layer that has a thickness of 0.0091 inch and a dielectric constant of 4.2. The prepeg layer, in turn, is followed by an inner layer, referred to as plane. A core sublayer comprises the inner layer 1 and has a width of 0.037 inch. This is followed by the inner layer 2 which is made of 1oz copper and has a thickness of 0.0014 inch. The inner layer 2 is constituted of another prepeg sublayer that comprises of 2 sheets. Finally, comes to the bottom layer, which is a signal layer as well. Its thickness is 0.0014 inch. When it comes to the interconnects, they are soldered on the top and bottom layers.

2. Difference in terms of Design

As opposed to a single layer PCB, the 2 layered PCB offers a higher surface area. This PCB uses vias to create electrical connections that enable the routing of the traces.

The 4-layered PCB has an even higher surface area than 2-layer PCB. Their design involves having a prepeg layer that can bond 2 or more double-sided boards. The prepeg also functions as a dielectric between layers.

3. Difference in terms of functionality

The 2-layer PCB is known to deliver a high degree of functionality as such PCBs do not suffer from propagation delays. Of course, a 4-layer PCB is preferred with its design comprising of ground & VCC plane layers as well as two signal layers. It’s added functionality, therefore, comes in extremely handy when it comes to complex functions.

4. Cost difference between 2 layer and 4-layer PCB

The complexity of design renders the 4-layer PCB to be more expensive than a 2-layer one. The higher cost of 4-layer PCBs is also on account of the fact that it offers superior signal quality with less distortion.

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5. Difference in terms of lending themselves to prototyping

Needless to mention, that a 4-layer prototype is more complex than a 2-layered one. However, with the use of automated software like Gerber an accurate prototype can be created. The software offers the choice of a number of parameters such as:

  • Thickness of the board
  • Hole thickness
  • Minimum pitch
  • Board finish

It also works well if the prototyping job is outsourced to an experienced contract manufacturer who specializes in creating prototypes.

How to choose between 2-layer & 4-layer PCBs?

Some of the aspects to consider in making the choice, include:

1. Complexity of the circuit

For complex circuits that feature RF circuitry, long digital buses, complex components and connections, 4-layer circuit boards are highly preferred. In such cases, using 2-layer boards would lead to compromise of the signal integrity.

2. Density of the circuit

In terms of circuit density, you could choose any of the boards as both allow for components to be mounted on both sides of the board.

3. Cost

If budget is a constraint, 2-layer boards work better as 4-layer boards that offer high functionality are also higher in terms of cost.

To sum up

The 2-layer and 4-layer boards offer different levels of functionality & work well for different types of projects. Therefore, the complexity of the project determines the choice of the right PCB.

If you are still confused, then contact Mer-Mar Electronics. Mer-Mar Electronics is an ISO 9001:2015 certified company who provides multilayer PCB assembly and fabrication. With the help of a team of experts, Mer-Mar Electronics provides highly durable and reliable PCBs. Request a quote for PCB assembly now to know more about our services.

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