The manufacturing process of multilayer printed circuit boards is a straightforward process, yet it requires careful attention to detail in all the stages involved in the process. PCB manufacturers must ensure all the layers are carefully connected to the drilled holes despite the deformation stresses during this process. Also, the buildup of multilayer board requires high-quality materials and the build sequence must be followed.
What is a MLB PCB?
MLB PCB is a type of printed circuit board that features more than two layers. In this type of circuit board, there is a minimum of three conductive layers or copper layer. The bottom and top layers of a multi layer PCB is similar to that of a double-sided PCB. However, MLB PCBs have more layers of conductive material on both sides of the core.
Also, these copper layers are attached with copper-plated holes. Multilayer board also known as MLB PCB can feature as many layers as 40 layers. In these boards, the electronic components are on the bottom and top layers of the multilayer circuit. The inner stacked layers function as the routing layer. Multilayer boards have been commonly used in compact and complex electrical appliances since they can house more electronic components such as diodes, transistors, resistors, etc.
Smart devices use between four layers to eight layers circuit boards. In most cases, designers use an even number of layers for multilayer boards. It is rare to see a multi layer PCB with odd number of layers. This is because the use of odd number of layers like 3 layer PCB or 9 layer PCB makes the circuit complex. This can make the cost of manufacturing higher.
More on MLB PCB
It is important to space the signal layers and place them very close to the planes in a four-layer stack up. This helps to enhance electromagnetic compatibility (EMC) performance. Also, integrate a large core between the ground plane and power plane. There should be a tight coupling between ground plane and signal trace. This helps in minimizing the plane impedance which in return reduces the common-mode radiation. Also, the crosstalk between traces will decrease if there is a close trace to plane coupling.
For multilayer printed circuit boards with a layer count as high as 12, the boards will need thin dielectric. Therefore, these boards will have tight coupling between the layers. Also, a multi layer PCB is often integrated for high-speed electronics as this PCB enhances signal integrity and EMI performance.
Advantages of Multilayer Boards
High quality
Multilayer boards offer high quality. These boards are often integrated in high performance applications. The manufacturing process of multilayer boards require a huge amount of work done in to provide multifunctionality in the small form factor PCB. These boards offer several functionalities. These functionalities are not usually provided by single layer PCBs.
Reduced form factor
Multilayer boards integrate advanced design rules and manufacturing processes to minimize their size while still maintaining high performance. This is the reason these boards are used in highly complex devices. Also, multilayer boards are widely integrated in compact electronic gadgets and smartphones and electronic gadgets. Therefore, they are widely used for electronic wearables.
Single connection point
Multilayer circuit boards can work on a single connection point. This works much better than the several connection points used in multiple single layer circuits.
Lightweight
Due to the integration of advanced manufacturing techniques in multilayer board production, this results in the production of lightweight boards. Their lightweight nature makes them ideal for use in wearable smart devices. Multilayer boards don’t have multiple connectors. This is one of the reasons for their lightweight. Multiple connectors are usually required to interconnect separate double-sided circuit boards.
More durability and flexibility
PCB manufacturers design a multilayer printed circuit board to withstand more weight. Also, this board is engineered to resist the pressure and heat used in binding the layers together. Furthermore, multilayer boards offer the required flexibility based on the applications. These boards don’t require a complete re-design.
Disadvantages of MLB PCBs
Although multilayer boards have a wide range of benefits they also have their downsides. It is important to know the drawbacks of the designing and manufacturing process of this PCB. The disadvantages of multilayer boards include
High cost of production
MLB PCB production cost more than single layer or double layer PCB production. Every stage of the manufacturing process consumes time and effort and as such more money is spent. Furthermore, there is more labour work involved in the production process. Multi layer PCB production requires advanced hdi design along with very expensive machinery.
Complex design process
The manufacturing process of a MLB PCB is a complex one. Also, the designing of these boards require an increased amount of hours. The designer must follow several design rules to achieve a functional board. Also, the type of substrate used also depends on application requirement.
Required domain expertise
The production of MLB PCBs requires great expertise and experience. PCB manufacturers who have acquired knowledge and skills pay more attention to details. Multilayer board assembly requires experience in CAD tools. Also, it requires the understanding of several design rule checks. Domain expertise is very crucial in the production process of this board due to challenges involved.
Applications of MLB PCBs
Modern-day consumer electronic
Consumer electronics such as smartphones and smart devices feature MLB PCBs. These boards are often integrated in these devices because of their multifunctionality and small form factor.
Telecommunication industry
Multilayer boards are widely used in transmission devices and telecommunication appliances. This is because of the flexibility and durability of these boards. Multilayer boards are ideal for use in both outdoor and indoor environments. Telecommunication devices such as cell phone transmission, hand held devices, and GPS technology among others feature multilayer boards.
Manufacturing industry and production line
The durability of these boards results in their capability to be integrated in extreme and harsh industrial setups. These boards can withstand extreme temperature, and pressure. Also, they are widely used in the manufacturing industry due to their multifunctionality.
Medical industry
In the medical industry, medical devices are needed for diagnosis of diseases, monitoring of patient’s health, and treatment of diseases. These medical devices need to be functional enough to diagnose and treat health conditions. Since multilayer boards offer great functionalities and less weight, these circuit boards are widely integrated in the medical industry. CAT scan machine, X-ray equipment, heart monitors, and more feature multilayer circuit boards.
Military and defense
The lightweight and durability provided by multilayer boards make it an ideal circuit board for the production of military and defense equipment. Also, multilayer circuit boards provide the compactness needed by military devices. These boards accommodate more components and offer multifunctionality.
Automotive and aerospace systems
Devices used in the automotive and aerospace industry are usually exposed to varying degrees of temperature. Multilayer circuits are built to resist extreme operating conditions. These boards still maintain their quality and functionality even under extreme environmental conditions. Therefore, they are a great option for automotive and aerospace systems.
Factors to Consider when Planning a Board Layer Stackup
There are several factors you need to put into consideration when planning a board layer stackup.
Routing density
This factor determines your circuit board layer stack-up’s configuration. You don’t want to go through the stress of you going back and including more layers to your design after the layout has been created. Also, you will need to make some changes to the layout. Therefore, it is important you consider the routing density of your multilayer board.
Cost
The materials used in MLB PCB production will have an impact on the overall production cost. Therefore, you will need to consider your options when choosing materials.
Performance
The performance and operating environment of your circuit board will determine a lot. When planning your layer stack up, it is important you consider the environment your circuit board will be operating. This will determine the quality of the materials to use and the number of layers your should have.
Circuitry
Also, you should design your circuitry according to its requirement. This will help you to create the most optimized layer configuration. In some cases, you may need a stripline layer configuration for sensitive signals to ensure their best performance. Also, this will mean including more ground planes. Digital and analog circuitry areas will require separation and there will be a need to isolate onboard power supplies.
MLB PCB Layout
The number of layers integrated in a MLB PCB has no limit. However, the thickness of the PCB will increase as the number of layer increases. The increased board thickness helps in accommodating the minimum thickness of materials integrated.
There are several factors that could impact the bottom and top of your multilayer boards.
Conclusion
MLB PCBs are electrical boards that comprise multiple layers. The designing and production of MLB PCBs are complex tasks. Therefore, these processes require domain expertise. Multilayer boards are known to offer enhanced electrical performance and minimize external noise. There are several advantages of integrating multilayer boards. Some of these advantages include flexibility, multiple functions, and small form factor.
