Bigger Isn’t Always Better: When Is 2-Layer PCB Better Than 4-Layer PCB?

2-layer pcb

Generally speaking, a 2-layer PCB isn’t as advanced as a 4-layer one. However, that doesn’t necessarily mean that the 4-layer version is always a better choice.

However, before we jump into the nitty-gritty of the 2-layer PCB, we need to cover the basics. Although we’ve already covered the details of PCB in our previous blog post, we can’t help but give you some basic information before we jump into comparison mode.

So you’re on the fence between 2-layer and 4-layer PCBs? You’re not sure which one to pick? Don’t worry, here at MKTPCB, we make both. However, we understand (better than most) the need to get the perfect board.

You might think that the more layers you have, the better, but that’s not always the case. Depending on your board design and your needs, you might be better off with a 2-layer PCB than a 4- or 6-layer one.

PCBs and Technology

When it comes to technology, we wouldn’t really have any of it without PCBs, at least not in the size and shape we enjoy today. PCBs or printed circuit boards made it possible to downsize electronic equipment. More importantly, they also made the entire designing and manufacturing process of robust circuitry more affordable.

That’s precisely why today there are affordable yet tiny alarm clocks, powerful mobile devices, handy kitchen appliances, and various other pieces of technology people use every day and take for granted.

The 2-layer PCB is among the most commonly used ones out of all types of PCBs. They allow manufacturers to create more complex boards that can support the features of higher technology.

What Exactly Are PCBs?

Invented in 1936, PCB made a real boom in the industry of electrical engineering. Thanks to it, the mass production of electronic devices that is a given today is possible and affordable.

Before that historical moment in 1936, manufacturers used a unique technique to wire electronic circuits. They used the “point-to-point” wiring technique to connect the circuits onto a base. Furthermore, the base was more often than not no more than a wooden box.

Every vital component of each device was connected to that base and other components with copper wires. That was a challenging process that required a lot of working hours to complete.

And then came PCB. Because people could print them, PCBs reduced the number of necessary working hours for production, sped up the entire process, and made mass production possible.

PCB 101

PCB or the printed circuit board supports and connects both electrical and electronic components. It does so with various features that are composed of one or more sheet layers of copper.

Those layers are, in turn, laminated onto sheet layers of a non-conductive substrate (or in between two or several sheets of a non-conductive substrate).

The features in question are signal traces, pathways, and tracks, which are all conductive and etched onto the copper layer of the non-conductive substrate. The substrate doesn’t conduct electricity, but the etchings on its surface allow the current to flow. That’s what allows for electrical connections between the components.

When it comes to components, manufacturers solder them onto the board. That way, they can carry circuits that power the devices they are a part of.

Aside from home appliances and handy gadgets, PCBs are also vital parts of machinery and tools used in various industries, computer storage systems, medical equipment, as well as government and aerospace equipment.

Not All PCBs Are Equal

The physical characteristics of various PCBs vary drastically. They come in many shapes and forms, but their primary purpose and design is pretty much always the same. PCB types generally vary depending on the number of bottom layers they have.

Based on that, they have specific capabilities regarding creating electrical currents and conducting them. Single-layer PCBs only have one layer of substrate with one copper layer on top of it. Multi-layer PCBs have more than one layer of both substrate and copper.

Multiple layers allow for a higher density of components. That means they can be a part of more powerful devices. However, there’s another side to that coin. The number of layers a PCB design has dictates the level of maintenance it requires.

The Advantages of 2-Layer PCB

Honestly, there are plenty of advantages to 2-layer PCBs. They differ from single-layer ones because they have two-sided traces. That means that there are layers of conductive copper over both sides of the substrate. This allows for a higher density of circuits.

The two copper or signal layers are also called the top and bottom layers. Thanks to there being two of them, the traces can cross over each other and jump between the two layers. They do so thanks to the vias.

The vias are plated through holes, and they allow for a connection between the two layers. To make vias, manufacturers put a copper pad on each side of the board and drill holes through them. These holes are non-conductive in the inner part and have conductive plating in the outer part. That plating is what connects the two layers of copper.

But why is this so important?

Size Always Matters

As mentioned, the 2-layer boards allow for a higher density of components. There’s more space on the board and, thus, more room for components.

That means that a double-layer board is an excellent choice for devices of higher technology that require more components than a single-layer board can offer.

Furthermore, the 2-layer PCB allows for more flexibility in design. The connections don’t have to be as rigid as they do with single-layer PCBs because there’s plenty of room for them. What’s more, 2-layer PCBs also usually have a more complex circuitry because there’s more room for it.

Finally, because you can use both sides of the board, the board itself doesn’t have to be as big. That means that you can use it even for advanced technology (that usually implies tiny devices).

Due to its size, a single-layer board just wouldn’t be a good fit for those devices, which is why a 2-layer PCB is. When it comes to potential applications, they are practically endless. You can find them in:

  1. cars
  2. lighting systems 
  3. hard drives and printers
  4. phone systems
  5. UPS systems
  6. test equipment
  7. converters
  8. amplifiers
  9. industrial controls
  10. vending machines, etc.

2-Layer PCB vs. 4-layer PCB

Now that you know everything about the 2-layer PCB and PCB in general, let’s take a look at the differences between the 2-layer PCB and the 4-layer PCB.

Structure

The stack-up of a 2-layer PCB differs significantly from the one of a 4-layer PCB. The 2-layer version has the top layer or signal layer that’s made of one ounce of copper, as is the bottom layer.

Unlike the 2-layer stack-up, the 4-layer one also has two layers between the top and the bottom one. What’s more, there’s also a prepreg layer that serves as insulation between the top, signal layer, and the inner layer (the plane layer).

As you can see, the stack-up of the 4-layer PCB is much more complicated.

Design and Functionality

The conductor pattern of a 2-layer PCB can be much more complicated than the one of a single-layer PCB simply because there’s more room. However, following the same logic, the 4-layer PCB has even more room, given that it has four layers of copper.

The boards also differ in shape — the board with four layers is more symmetrical.

When it comes to functionality, both boards have their own advantages and disadvantages. A 2-layer PCB has no issues or propagation delays. You won’t get those results with a 4-layer PCB.

On the other hand, a 4-layer PCB with a ground plane and a VCC plane performs at a higher level and has higher signal integrity levels. However, it also has issues with impedance.

Cost

Of course, when you consider the complexity of the design and the cost of the overall materials, it’s logical that the board with four layers is more expensive than the one with two layers.

When You Should Choose 2-Layer PCB Over 4-Layer PCB

Depending on the project you’re working on, several types of PCBs might be a good choice for you. For example, if you’re trying to make something extra small with a lot of functionality, maybe you should go for the 4-layer PCB.

However, if you’re on a tight budget and space isn’t your main concern, then the 2-layer PCB should be your top pick.

Furthermore, while a 4-layer PCB might be more durable, a 2-layer PCB is easier to make and lead. So depending on how fast you need it, the 2-layer PCB might be the board for you.

A Few Parting Words

When it comes to PCBs, there’s no doubt that the 2-layer ones are most common. With over ten years of experience in the industry, we at MKTPCB can attest to that. People prefer them due to their affordability and flexibility.

Of course, there’s a lot to be said about some minor disadvantages. Compared to other, more advanced boards, the 2-layered PCB boards are less effective when it comes to signal integrity. What’s more, other boards with more layers will probably come on top when it comes to interference levels as well.

Still, that doesn’t mean that a 2-layer PCB isn’t a functional board. In fact, it has the best ratio of cost and functionality, which probably explains why its use is so wide-spread.

Contact Us!

If you need help deciding which PCB is the perfect choice for you, or you have any questions about our products, we’re here to help! Contact us, and we’ll guide you through the entire process.

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