About Multilayer PCB, How to Determine Your Product

Multilayer PCB production and design pose a considerable challenge to us because many things can go wrong.  Without a proper plan in place, designing a multilayer printed circuit board can be complicated. At present, multilayer PCB is extensive, and it is becoming more and more important in various industries. We all need to work hard to produce high-quality multilayer PCBs.

Here, you will learn a lot to do with multilayer PCBs, from its advantages, disadvantages, applications, and composition, among others. As a result, you will have a Such will enable you to have an easy process when choosing between single, double, or multilayer PCBs.

1. PCB Structure Type

Before you choose a circuit board, you need to make a sound decision. So, decide which type of layered PCB your project suits whether your project is suitable for a single layer, double layer, or multilayer PCB.

You’ll understand the merits and demerits of single, double, and multilayer PCBs in the table below.

(An image depicting different types of PCBs)

2. What Is a Multilayer PCB?

A multilayer PCB is a board consisting of more than a single layer of conductive material. Single and double-sided printed circuit boards have one and two layers, respectively. However, multilayer PCB consists of three layers of conductive material or more. You can find these materials buried at the center of the material.

Multilayer PCBs came into existence based on rapid changes across the electronics industry. With the functions of electronics also becoming complex, so is the need for more complex PCBs. Multilayer PCBs came to fix most of these issues. Issues to do with stray capacitance, noise, and cross-talk were now things of the past. 

3. Why do PCBs Have Multiple layers? / Why do you Need Multilayer PCB?

As you may be well aware, PCBs can be single, double, or multilayered. There are some applications where available, favor, and double-sided PCBs do best. However, with rapid changes across the electronics industry, multilayer PCBs are essential.

So, what's the need for multilayer circuit boards? The reasons are many, but mainly multilayer PCBs come with higher operating capacity. Additionally, they can run at high speeds, not forgetting that they are durable. The following are the merits of multilayer PCBs.

3.1 Advantages of Multilayer PCB

• Useful for more complex projects – Complex circuitry requires a multilayer PCB. Complex projects that need advanced equipment must-have tools with multilayer PCBs in them. Luckily enough, this is an easy thing for multilayer boards.
• High quality. – Unlike single and double-layered PCBs, multilayer boards require intense planning and production. Therefore, it means that they are of the highest quality compared to other boards.
• Increased power. – Based on increased circuit density that is characteristic of multilayer PCBs, this means that they are more powerful. Additionally, they run at very high speeds bringing about enhanced performance in equipment.
• Higher durability – Multilayer PCBs are highly durable, partly due to their stack up.
• Smaller in size and lighter in weight – More layers in a board mean thicker, hence durable. With more layers, such panels can effectively function in harsh conditions.
• Single connection point. – If you use several PCB components, you would need several connection points. But this isn't the case with multilayer PCBs. Their design is to work with a single point of contact. With such, the system becomes simple, and the weight also reduces.

3.2 Disadvantages of Multilayer PCB

• Higher power – Multilayer PCBs require high and constant power at all times. In other words, you have to be prepared to handle high electricity costs. Its because multilayer boards tend to consume much energy. 
• Higher cost - Designing and manufacturing multilayer PCBs is a costly affair. Here, there's the use of more resources, a majority of which tend to be expensive. If you happen to be on a budget, then you may be disadvantaged.
• Complex design and production. – Unlike single and double layer boards whose design, prototype, and production is fast, multilayer PCBs are unique. Designing and producing them requires time and the need to look at intricate details. That may consume much time.
• Limited availability. - According to a wide range of professional fields, multilayer PCBs tend to be always out of stock. Much worse, there are a few companies that can manufacture high-quality multilayer PCBs. Again, this is a reason why they are so limited.
• Longer delivery time – Designing and manufacturing multilayer PCBs is a lengthy process. There are many processes to consider, a factor that amounts to increased lead times. Based on their high demand, you may have to wait for a while for your order to arrive. 
• Repair is complicated – Repairing multilayer PCBs is quite a complex task. A slight mistake may render the whole exercise useless. 

3.3 Applications of Multilayer PCBs

There are several application areas where multilayer PCBs find much use. They include the following areas:

• Industry –A majority of industrial equipment operates in temperatures and high vibrations. Luckily enough, that's not an issue as such with multilayer PCBs. They can withstand high temperatures and rigorous vibrations for a long time.
• Telecommunications –Telecommunication equipment mostly relies on multilayer PCBs. You'll find them in outdoor towers, mobile devices, satellite, and GPS applications.
• Computer electronics. – A lot of computer electronics rely on multilayer PCBs. It is because of their speeds and space-saving characteristics. You'll find them on many computer electronics.
• Consumer electronics – Consumer electronics are almost everywhere. These are day to day products that we use, such as microwaves, fridges, and smartphones. While all of these have PCBs in them, many of them have multilayer boards in them.
• Military and defense – Cherished for their functionality, durability, and low-weight, almost all military and defense equipment have multilayer boards. They also favor military applications as they can withstand severe conditions during wars.
• Aerospace – Rockets, jets, and airplanes rely on PCBs. But not any PCB, but mostly multilayer PCBs. Multilayer boards can effectively handle atmospheric journey stress, unlike their counterparts.
• Automobile industry. – More and more multilayer PCBs are finding much use in the automotive industry. Engine sensors, headlight switches, and onboard computers mostly rely on multilayer PCBs.
• Other areas – That's not all. There are plenty of other industries that rely on multilayer PCBs. The medical field is one of them. Lately, science, research, security, and many home appliances also rely on multilayer PCBs.

3.4 Why do We Apply Multilayer Widely?

There’s more than what meets the eye when it comes to the applicability of multilayer boards. The above is just the tip of the iceberg. We continue to apply multilayer boards due to changes in the electronics industry. With space and weight becoming an issue, there's a need to embrace multilayer boards. Also, with the need for speed, nothing satisfies such thirst that multilayer PCBs.

(Image of a multilayer PCB on an isolated white background)

4. Do you Need Single-layer or Multilayer PCBs?

The choice between single and multilayer PCBs depends on several issues, as discussed below:

4.1 What level of functionality do I need?

If the functionality you need is involved, you'll find multilayer PCBs perfect for you.

4.2 What is the maximum size of the board?

A board that's too large may compel you to use single-sided PCBs. Multilayer boards are small and compact.

4.3 Is durability a priority?

How long do you want your boards to last? Longer projects must ensure that they use multilayer PCBs. Since these PCBs can endure a very long time while functioning well.

4.4 What is my budget?

Are you operating on a budget? If finances aren't a problem, then go for multilayer PCBs. With them, you will enjoy the best quality and durability.

4.5 How soon do I need a PCB?

Do you need your PCBs within the shortest time possible, or you have the patience to wait? So, if you urgently need a circuit board within the shortest period, a single-sided PCB could work best.

(A multilayer PCB)

5. Determine the Number of Layers of your Multilayer PCB

The number of layers on your multilayer PCB depends on the functionality that you desire. Depending on your project, you may need the following:

5.1 Four-layer PCB

A four-layered PCB consists of four layers of the conductive substrate material.

5.1.1. Composition of four-layer PCB

A four-layered PCB consists of a top, bottom, and outer layers. Inner layers 1 and 2 are in the core, typically acting as power planes or signal routing. Therefore, the composition of a four-layer PCB is three signal layers and GND (ground) layer.

   5.1.2 Relative advantages of four-layer PCB

• Durability – Four-layered PCBs are highly durable compared to single and double-layered ones.
• Compact size – Being small in size, a four-layered PCB can easily fit in plenty of devices.
• Flexibility – It can adequately work on several electronic devices. It is regardless of whether they are involved or not.
• Safety – four-layered PCBs have an excellent alignment of ground layers and power. It Makes makes the four-layered PCBs very safe.
• Lightweight – Four-layered PCBs have a little need for internal wiring. They are light in weight.

5.1.3. Typical application areas of four-layer PCBs

The design and manufacture of four-layered PCBs are tasking and expensive. But, these boards payback based on their broad application areas. You can find four-layered PCBs in satellite systems and space probe tools. They are also ideal in X-ray equipment,four-layered PCBs’CAT scanners, and file servers.

5.2 Six-layer PCB

Again, a six-layer PCB is a board that has six layers of substrate material in it. Since they first hit the market, they've never stepped on the reverse gear.

5.2.1 Composition of Six-layer PCB

It's like a four-layered PCB, made of two extra rows of dielectric material and two additional copper layers. In a six-layer stack up, the "core" is the second and fourth dielectric row. The first and third is prepreg.

 5.2.2 Relative advantages of six-layer PCB

• Strength – They are thicker, meaning that they are healthy.
• Compactness – Being thick, they have increased technological capacity and can consume little width.
• High capacity – These PCBs offer electronic devices optimal power, significantly minimizing electromagnetic interference and cross-talk.

5.2.3 Common application areas of six-layer PCB

Six-layer PCBs find applicability in several areas. For instance, they find use in computers, data storage, and fire alarm systems.

5.3 Complex multilayer PCBs

As mentioned earlier, trends across the electronics industry change almost daily. Miniaturization and the need for speed calls for the development of complex PCBs. It's no wonder we now have complex multilayer PCBs consisting of more than 30 layers.

(Part of a complex PCB)

6. How to Identify Multilayer PCB

For novices, it might be a little bit difficult identifying a multilayer board. So, how do you tell that your board has more than a single layer? Read below to understand:

• Observe the PCB edge. – If you want to know whether your PCB is multilayered or not easily, observe its boundaries. The advantage of a multilayered PCB is slightly thicker.
• View the copper surface under the flash. – The copper surface under the second layer in multilayer PCBs is thicker than those you can find in single-layered PCBs.
• Use intense light to analyze the inner layer – If you use a bright light, you'll see if your board has some inner layers.
• Observe the traces and paths. – The trails and tracks of single-layered PCBs differ from multilayer PCBs. For multilayer PCBs, you'll most definitely spot return signal paths.

(A multilayered PCB on a red background)

7. Design Multilayer PCB Rules

The following are design rules you need to follow when designing multilayer PCBs:

7.1 The thickness of copper should be higher than the average. – Multilayer PCBs require extra copper, unlike single-sided ones. 

7.2 Increase the width of the trace accordingly. – Based on its functionality, you have to increase the width trace based on the number of layers.

7.3 Avoid 90-degree wiring to avoid EMI (electromagnetic induction) problems. – At all costs, avoid 90-degree wiring and instead resort to 45-degree wiring to cases of EMI.

7.4 Overcome the magnetic field’s influence and increase the return path or ground plane. – Ensure that you block the magnetic force by re-routing the magnetic field lines. 

7.5 We need to separate the analog and digital parts of the circuit from the ground plane, and they need some connection at one point. – It's as simple as that. For the best design, make sure to separate the circuit’s digital and analog parts from the ground plane. They should not be in contact with the ground plane at any given moment. 

7.6 Avoid noise coupling and avoid long traces containing analog and digital signals – – you can reduce noise using bandwidth reduction. You have to layout your printed board to ensure that you avoid instances of noise coupling. 

7.7 Decoupling capacitors to solve stray inductance. – Decoupling capacitors have to connect to low impedance ground plane to be effective. Using the correct connection of the decoupling capacitor influential site, you can avoid a lot of trouble.

(Robotic soldering of a multilayer PCB)

8. Multilayer PCB Production

The manufacture of multilayer PCBs is a bit detailed. To produce multilayer PCBs, alternate some layers of epoxy-infused fiberglass sheet known as prepreg. You'll have to ensure that you laminate the conductive core materials under high pressure and temperature using a hydraulic press. After cooling, the resulting component undergoes the same process as a double-sided PCB.

8.1 Make the inner layer of the PCB the core

When manufacturing multilayer PCBs, ensure that you make inner layers of the PCB the heart. This way, you'll ensure that all the layers stay in the intended position.

8.2 Multilayer PCB lamination

Never forget to laminate the layers of your multilayer PCBs. By laminating, you are increasing the functionality and capabilities of your circuit board.

(Multilayer PCB production plant)

9. Common Problems in Multilayer PCB Production

The manufacture of a multilayer printed circuit board is not an easy process as such. As you may be well aware, multilayer PCBs have some problems during their production. There are several problems manufacturers encounter when producing multilayer printed circuit boards. However, some of the most common ones include the following:

Layer alignment

As you may be aware by now, multilayer PCBs consist of several layers. Unlike single-sided PCBs, multilayer PCBs have more than a single layer. The problem comes in when trying to align them properly during assembly. Poor layer alignment is one area that many manufacturers find challenging.

Selection of substrate material

The type of substrate material you choose to use will affect your board’s functionality. Again, many designers fail when it comes to selecting the best choice material to use.

Stratification

During PCB production, it can be challenging to different group parts of the board into one group. Such is a problem, especially in high volume production.

Moisture and pollution

Many multilayer PCB makers don't understand how to prevent humidity and corrosion. However, the solution to such is by use of the best surface finish and proper storage.

Drilling accuracy

Poor drilling leads to poor board functionality. These could be as a result of the wrong equipment or wrong measurements.

Through-hole selection

Here, the section of proper through-hole is another big challenge facing manufacturers. Manufacturers can avoid such issues by using the latest through-hole technology.

(A damaged multilayer board)

10. Customize Your Multilayer PCB

If you so wish, you can customize your multilayer PCB. There are plenty of experts with the ability to create a multilayer PCB the way you want. However, there are a few things to note, as briefly discussed below:

10.1 Precautions for custom multilayer PCB

Before you choose to customize your PCBs, it is essential to pay attention to some precautions. Here, expect high customization costs, long waiting times, and plenty of reworks. 

10.2 How to reduce customization costs

PCB customization costs are always enormous. But you can cut such costs by reducing the size and the material selection of your PCB. Firstly, you may also have to sacrifice on a PCB with complex shapes, which may end up being expensive on your end. 

10.3 Choose the right multilayer PCB supplier

Having an inexperienced multilayer PCB supplier is disastrous. If you deal with the wrong supplier, expect delays. These delays will, in turn, negatively impact your business reputation. Go for established ones with decades of experience in the field to get the best service.  

(A custom-made PCB)

Summary

We have a passion for electronics. It enables us to become the best multilayer manufacturers around. We are a company that you can trust for multilayer circuits for use in advanced applications.

We have a team of experts who use state-of-the-art multilayer manufacturing equipment to ensure that our boards fit the project. Talk to us to cut your multilayer production costs. Call us today for a fast and accurate multilayer PCB quote.