Multilayer PCBs – How are they better or worse for you?

Multilayer PCBs are getting attention in the electronics industry, and their demand is on the rise. The craze is because designers are now looking for more powerful, faster and yet smaller circuit boards. Unfortunately, double and single-sided boards are unable to open up a world of possibilities like multilayer PCBs.


Engineers are lucky that there is a circuit board available that has enough space to accommodate their sophisticated designs. Multilayer PCB is made up of both single and double-sided PCBs. So, you will get higher assembly density and much more! This article is for explaining all the details related to Multilayer PCB. Just keep on reading.

1、Multilayer PCB

1.1 What is a Multilayer PCB?

Multilayer printed circuit board always have over two conductive material layers. In double-sided PCBs, you will only get two conductive material layers and not more than that. However, multilayer PCB’s conductive material layers start from three that are located at the centre of insulating material.


You will get more wiring area with multilayer PCBs. They are made by putting together several double-sided boards with an insulating material among them. Usually, you can design multilayer PCB as a rigid board as it is complicated to create it as a flexible PCB.


We would recommend you design between four to eight layers of conductive material. They are usually enough to fulfil any ordinary circuit needs. You will realize that adding more layers without vital need will only increase your expenses. Figure 1 shows a multilayer PCB.


A multilayer PCB.jpg


1.2 Why do you need them?

Nowadays, using multilayer PCBs is the latest industry trend. You will fall behind your colleagues or competitors if you do not evolve with what the market demands.  Electronics is moving towards a reduction in size along with multi-functional products.


Double-sided and single sided PCBs have limited ability to balance functionality and size.  However, you can get that with multilayer PCBs. You will learn in the next sections that there are also many disadvantaged of multilayer PCBs such as high cost. But, cunning people know that cost should not be the problem if you are getting high-quality products.


Moreover, the electronic components are getting smaller day by day, so they are demanding small PCBs. If you keep on using traditional boards, you can well imagine where you stand in this evolving technological world.


In this section, we introduced multilayer PCBs and their need. In the next section, we will tell you about their construction and designing rules. Stay tuned.

2、Designing the Multilayer PCB

2.1 How are they made?

Before jumping to the construction of multilayer PCB, you must know about Vias and their working. Let us briefly introduce these terms for you here. Vias exist in three main types, i.e. buried, blind, and through vias.


Buried vias are concealed within PCB layers, and you can never see them from the outside. They make connections between internal layers that through vias, cannot reach. On the contrary, blind vias do not travel through the whole circuit board. They only make connections between outside and internal layers.


Knowing the usage of these three types of vias is the key to effectively design a multilayer PCB. They will make PCB routing amazingly simpler. However, if you are worried about cost, you should use buried and blind vias when it is an ultimate necessity.


Multilayer PCBs with vias will allow electronics components to get their desired small space. Trace distance will also reduce, and thus signal integrity will be enhanced with these PCBs. The laser is mostly used to drill blind vias, and they are mostly about 0.1 mm. What does that mean? You can place them on pads of the multilayer PCB. Nonetheless, you should avoid placing vias on BGA pads.


2.2 Things-to-do before professionally designing the Multilayer PCB

Before creating the PCB layout of the multilayer PCB, you should investigate the following steps:


1.You should finish your circuit design and check its functionality.


2.You should complete your Part list, Netlist, and BOM.


3.You should know the size of the PCB that your project needs.


4.You should do homework on how much layers do you need, what should be their size, how you should stack them up, or what kind of vias should they incorporate. For instance, Eagle software uses the following notation:


5.p + q means that these layers and prepreg are stacked together.


6.P * q means that these layers are stacked together with a core.


7.() shows through and buried vias.


8.[a:… : b] illustrated blind vias.


A multilayer PCB setup in Eagle CAD software.jpg


9.You should make sure that you can comprehend the basic specifications of electronic components. For example, several components may have different values for standoff/ or EMI distance to other parts.


10.Furthermore, you should also decide upon the trace widths, ring sizes, vias sizes, clearances, and scoring. You should declare how much is required by the circuit board as these occupy much space.


So, these are a few of things that would lead you towards successfully designing a PCB multilayer. In the next section, we will answer the primary two complications related to this field.

3、Complications related to Multilayer PCB

3.1 What will happen if you keep on adding more layers?

If you keep on adding more layers, complications will arise in terms of cost. However, the value and addition of layers do not follow a linear relationship. Because the process of drilling, plating, solder masking, and silk screening only need to be done once. They are not dependent upon several layers. But, etching, photo-exposing, and lamination need to be performed once after every two layers.


Roughly, you will be increasing your expenses in the following manner: if you go from two layers to four or six layers, you are increasing your cost by 1.5 to 2 times, respectively. However, you will also get many benefits to balance the increased costs:


1.You will get a simplified routing procedure.


2.Board size will reduce because of the higher density of layout.


3.You will get ground planes or multiple ground planes.


4.You will have the additional heat-sinking capability.


5.You will be able to use plane layers for separation and shielding of analogue and digital or sensitive analogue circuits. Figure 3 demonstrates the multilayer PCB being soldered by robotic soldering.


Soldering of a multilayer PCB.jpg


6.There will be solid plane layers for controlled and constant impedance line.


3.2 How to identify Multilayer PCB?

If you feel cynical and want to know the total number of layers laminated in the multilayer PCB in your hand, we can help you with that. Simple, follow the following steps:


1.Shine a light on the board edge to see the copper planes. You will be able to see signal traces more thoroughly.


2.Use bright light to examine the inner layers of the multilayer PCB.


3.The best area to look for inner layers is where you cannot see paths or lines on the outer layer.


4.You can also look around the edge to read the number of layers. Some manufacturers print the total number of layers on the board.


In this section, we told you about the consequences of adding a higher number of layers and how to identify their number from looking at the board. In the next section, we will point out the advantages of the multilayer PCB.

4、Advantages of Multilayer PCB

Multilayer PCBs offer many advantages when compared with single or double-sided layer PCBs. Some of them are:

1.You will get higher assembly density because of layering. That will, in turn, provide enhanced capacity, more functionality, and speed.


2.You are getting smaller sized PCB. Multilayer PCBs increase their surface area and not size by adding a greater number of layers.


3.Multilayer PCBs are also lighter in weight. There is a need for a smaller number of wires, connectors, and related stuff.


4.You will get enhanced design functionality. That is because of more excellent EMI shielding, controlled impedance attributes, and better quality of design. Furthermore, you are getting a simple routing procedure. Figure 4 shows an example of how the final form of a PCB routing procedure may look like.


PCB layout routing.jpg


So, what do these benefits mean for you? Should you go for multilayer PCB or not? Let us help you with that. Fundamentally, if you want lightweight, small, and high quality, you should go for a multilayer PCB. Also, if your design is complicated, multilayer PCB will be your saviour. However, if you are not worried about weight and size, then other PCBs can be a cheaper solution.

In this section, we discussed the advantages of the multilayer PCB. In the next section, we will list down its limitations.

5、Limitations of Multilayer PCB

Well, there are also few limitations that come when you are dealing with multilayer PCB. It is essential to consider them before finalizing whether you should go for them or not.


1.High cost. If you are a budget person, you should take into account the total project cost before selecting a multilayer PCB.


2.More Manufacturing Time. If you are time conscious or have less time for completion of the project, then this is a major limitation.


3.Complex Repair. Multilayer PCB needs more complicated mending procedure when you compare it with other types of PCBs.


So, these are the only main limitations that should bother you before making a choice. Tell us in the comments below if they matter for you. Figure 5 demonstrates that a smartphone can be used to analyze the printed circuit boards. Is not that amazing?


In this section, we discussed the limitations of the multilayer PCB. In the next section, we will tell you about its major applications.  


A cell phone is examining a printed circuit board.jpg

6、Applications of Multilayer PCB

In the world of Aerospace, multilayer PCBs are particularly valuable because of their space and weight advantages. Figure 6 shows a close view of the rotor of a helicopter.


Rotor of a helicopter incorporating PCBs.jpg


You will also see multilayer PCBs in applications where the level of “cross-talks” are vital. Apart from these, the following areas are using multilayer PCBs:

•  Data storage


•  Signal transmission


•  Computers


•  File servers


•  GPS technology


•  Industrial controls


•  Test equipment


•  X-ray equipment


•  Cell phone transmission


•  Central fire alarm systems


•  Cat scan technology


•  Cell phone repeaters


•  Handheld devices


•  Atomic accelerators


•  Nuclear detection systems


•  Space probe equipment


•  Fibre optic receptors


•  Weather analysis


•  Heart monitors


•  Satellite systems


In conclusion, we would say that electronics designs are getting complicated day by day. Designers are looking for more wiring area and need PCBs that are small in size. Furthermore, they also need higher assembly density and want to incorporate their design functionality fully. And, single- and double-sided PCBs are not fulfilling your needs. So, in this case, multilayer PCBs are your solution.


We have added all the necessary information related to multilayer PCBs. This article will help you decide whether you need to use them over other types. We, here at WellPCB, can manufacture your multilayer PCBs with high quality. All you need to do is to go to our website and place an order.


You will need to fill in some specifications that you need in your PCB while placing the order. After that, our Engineers will check your order and soon an instant quote will also appear. And then in no time, your multilayer PCB will be at your doorstep as we also offer quick deliveries.


Still, do you need more information? You can contact us right away! Do not hesitate even for a second.

Do You Have Any Question About PCB Manufacturing Or PCB Assembly?

Order or no order, I am always happy to make friends and provide a Free consultant for you.

Any questions about PCB Manufacturing and PCB Assembly Process in your projects, Feel free to consult us online or through email, we will try our best to help you and try to meet your requirements!