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 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 a circuit board has enough space to accommodate their sophisticated designs. Multilayer PCB is made up of both single and double-sided on reading.

Multilayer PCB

1.1 Multilayer PCBs—What is a Multilayer PCB?

Multilayer printed circuit boards 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 located at the center 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 a 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 fulfill any ordinary circuit needs. You will realize that adding more layers without vital needs will only increase your expenses. Figure 1 shows a multilayer PCB.

1.2 Why do you need them?

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

Double-sided and single-sided PCBs have limited ability to balance functionality and size.  However, you can get that with multilayer PCBs. In the next sections, you will learn that there are also many disadvantages 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 using traditional boards, you can 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.

Designing the Multilayer PCB

2.1 Multilayer PCBs—How are they made?

Before jumping to the construction of multilayer PCB, you must know about Vias and their work. Let us briefly introduce these terms to 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 the 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 many layers you need, then size, how you should stack them up, or what kind of vias they should 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.

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 a lot of space.

So, these are a few 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.

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 needs 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 increase 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 use plane layers for separation and shielding of analog and digital or sensitive analog circuits. Figure 3 demonstrates the multilayer PCB being soldered by robotic soldering.

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

3.2 Multilayer PCBs—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 identifying their number from looking at the board. In the next section, we will point out the advantages of the multilayer PCB.

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 a 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 routine procedure. Figure 4 shows an example of how the final form of a PCB routing procedure may look like.

So, what do these benefits mean for you? Should you go for a 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 savior. However, if you are not worried about weight and size, other PCBs can be cheaper.

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

Limitations of Multilayer PCB

Well, few limitations 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.Multilayer PCBs—High cost. If you are a budget person, you should consider the total project cost before selecting a multilayer PCB.

2.More Manufacturing Time. If you are time conscious or have less time to complete the project, this is a major limitation.

3.Complex Repair. Multilayer PCB needs a more complicated mending procedure when you compare them 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 to you. Figure 5 demonstrates that a smartphone can be used to analyze the printed circuit boards. Is it 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.  

Multilayer PCBs–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.

You will also see multilayer PCBs in applications where the level of “cross-talks” is 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
• Fiber optic receptors
• Weather analysis
• Heart monitors
• Satellite systems

Conclusion

In conclusion, we would say that electronic designs are getting complicated day by day. Designers are looking for more wiring areas 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.