PCB refers to the insulating material comprised of printed circuit, printed components, or a combination of both conductive graphics, according to a preset design. By function, PCBs can be classified as single-sided PCBs, double-sided PCBs, multilayer PCBs, aluminum-based circuit boards, impedance circuit boards, FPC flexible circuit boards, and so on.
What Is a Multilayer PCB?
A multilayer PCB is one that is comprised of three or more conductive copper foil layers. Multiple layers of double-sided circuit boards are laminated and glued together with layers of heat-resistant insulation in between. Two layers are positioned on the surface sides of the PCB in order to connect to the environment. Using vias such as plating through holes, blind and buried vias, all electrical connections between the layers are made. The application of this technology then generates PCBs of various complexity and size.
Why Are Multilayer PCB So Widely Used?
The applications listed above represent only a small portion of the multilayer PCBs used in the industry. But why are they so popular?
Multiple substrates are now required as a result of the increased density of integrated circuit packages, which has led to a high concentration of interconnecting lines. In the configuration of the printed circuit, unanticipated design difficulties including noise, stray capacitance, and crosstalk develop. Therefore, the design of the printed circuit board must prioritize lowering signal line length and avoiding parallel paths, etc. Due to the restricted number of crossings that may be performed in a single or even double panel, it is obvious that these requirements cannot be met adequately. In the event of a large number of interconnections and crossover needs, the board must be stretched to more than two layers in order to reach a reasonable level of performance, resulting in the emergence of multilayer boards.
Multilayer circuit boards consist of numerous alignment layers with a very thin dielectric layer between each pair of layers. At least three conductive layers are present on multilayer circuit boards, of which two are on the exterior surface and one is created within the insulating board. Typically, the electrical connection between them is established by plating through holes in the board’s cross-section.
The Benefits of Multilayer PCB
1.The density of the multilayer PCB assembly is high and compact.
2.Multilayer PCB wiring convenience, shortened wiring length and component connections, favourable to enhancing signal transmission speed.
3.For high-frequency circuits, the addition of ground layer causes the signal line to form a constant low impedance with the ground layer, therefore reducing circuit impedance and enhancing the shielding effect.
4.For the high need for heat dissipation function of electronic devices, multilayer PCBs can be designed with a metal core heat dissipation layer to meet the requirements of shielding, heat dissipation, and other unique characteristics.
5.Multilayer PCB is superior than single and double panels in terms of performance, but the more the number of layers, the higher the production cost, the longer the processing time, and the more complex the quality testing.
6.Multilayer PCBs typically consist of four or six layers; the difference between four-layer and six-layer boards is the presence of a ground layer and power layer between two more internal signal layers on the six-layer board, which is also thicker.
Due to its design versatility, economic superiority, electrical performance stability and dependability, etc., multilayer PCB is currently widely used in the production of electronic devices.
Tips for Disadvantages of Multilayer PCB
1. More expensive
Due to the complexity of the design and manufacturing process, multilayer circuit boards are more expensive than single-layer circuit boards.
2. Extended lead time
So that each layer may be turned into a separate circuit board, the production process for multilayer boards is complex and lengthy.
3.Maintenance can be challenging
It is difficult to repair a multilayer printed circuit board if it develops a defect. Certain internal.Some internal layers may not be seen from the exterior, making it more challenging to determine what caused the component or physical board’s damage.The reason for the component or board damage. Additionally, the amount of integrated components on the board must be considered.
What is Difference Between Single-Layer and Multi-layer PCB?
Printed circuit board Ordinary circuit boards are divided into single-sided alignment and double-sided alignment, commonly known as single-sided and double-sided, but high-end electronic products, due to the constraints of product space design factors, in addition to surface wiring, the internal can be stacked with multiple layers of lines, the production process, the production of each layer of lines After each layer is created, it is positioned and pressed together by optical equipment, allowing numerous layers of circuits to be superimposed on a single board. Also known as a multilayer circuit board. A multilayer circuit board is any circuit board with more than or equal to two layers. Multilayer circuit boards are classified as rigid circuit boards, soft and rigid circuit boards, and multilayer soft and rigid combination circuit boards.
How do you differentiate between multilayer and singlelayer PCB?
1.Hold up to the light; if the inner core is opaque, i.e., entirely black, it is a multilayer board; if it is transparent, it is a single double-sided board; and if it is a single-sided board, there is no copper inside the hole. The front and back sides of the copper guide through the hole are double-sided.
2.The number of line layers is the most significant distinction between 2 and 3.Single-layer PCB only one layer of lines (copper layer), no metallization in the holes, and no plating procedure.Double-layer PCB consists of two layers of lines (copper layer), with metallized and non-metallized holes, and plating procedure.
3.PCBs are subdivided into single-sided PCBs, double-sided PCBs, and multilayer PCBs, with the latter referring to PCBs with three or more layers. The multilayer PCB production process will be based on a single double-sided panel plus the inner layer lamination production process. Additionally, the utilization of slicing distraction can be studied.
Applications for Multilayer board
The printing industry
From a conventional standpoint, industrial electronic equipment should concentrate on preventing corrosion. Tri-proof paint is frequently used as a coating layer on the surface of PCBs. It is a particular coating layer that, in addition to the aforementioned properties, is shock-resistant and insulated. Multi-layer PCBPCB stable performance, strong protection, suited for the board process, can effectively meet the printing industry’s mechanical performance requirements for ongoing high-speed operation.
The electronic equipment sector
Electronic packaging technology is essentially a higher hardness and brittleness of the semiconductor chip through a specific plastic sealing method to help the chip to better achieve its requirements for protection, heat dissipation and wiring to meet the chip for power distribution, system integration, and other performance requirements, so that it can better play an important role in so many applications. These electrical components require a pretty high level of protection for their packaging. In order to complete the packaging of various electronic components, which have somewhat complex functional and material requirements, multilayer PCBPCB is preferable for the aforementioned goals.
The field of intelligent house design
The use of printed circuit boards (PCBs) to the field of home design is a result of the emergence of smart home thinking; people anticipate a more intelligent effect of the home space environment. To achieve this objective, a variety of walls, floors, and other locations must be utilized to guide the smart device PCB. Multilayer PCB with its own improved reaction, to facilitate the development of smart home spaces.
Multilayer PCB elies on its own improvement of typical PCB performance transformation, deriving little new performance from the former. Create a more sophisticated and detailed product structure is the current consensus of the Chinese machinery industry. In order to reach this aim as soon as possible, it is required to continue to steer the renewal of technology and product replacement.
Manufacturing process of Multilayer PCB
1.Material choice
With the development of high-performance, multi-functional electronic components, as well as the high-frequency, high-speed development of signal transmission, the requirements of electronic circuit materials, dielectric constant and dielectric loss are relatively low, along with low CTE, low water absorption, and better high-performance copper clad materials to meet the processing and reliability requirements of multilayer boards.
2.Design for a laminated laminated structure
In the design of the laminated structure, the heat resistance of the material, the voltage resistance, the amount of adhesive filling, the thickness of the dielectric layer, etc. are the primary considerations. The following guidelines should be adhered to.
(1) The manufacturer of the semi-cured sheet and the core board must be consistent.
(2) When the client requests a high TG sheet, both the core board and the semi-cured sheet must be fabricated from a material with a correspondingly high TG.
(3) For interior substrates of 3OZ or more, use semi-cured, high-resin-content sheeting.
(4) If the client has no specific requirements, the interlayer media layer thickness tolerance is typically managed by +/-10 percent. For impedance boards, the media layer thickness tolerance is governed by the IPC-4101 C/M level tolerance.
3.Layer alignment management
Inner layer core board size compensation accuracy and production size control, the need for a specific period of time in the production of historical data, the graphic size of each layer of the high-level board for accurate compensation to ensure that the core board of each layer up and down consistency.
4.Inner layer line method
Laser direct imaging machine (LDI) can be utilized to enhance the graphical resolution of high-level board fabrication. In order to improve the line etching capability, it is necessary to account for the line’s width and pad in the engineering design, and to confirm that the inner layer line width, line distance, isolation ring size, independent line, and hole to line distance design compensation is reasonable; if not, the engineering design must be revised.
5.Pressing method
Presently, the interlayer positioning method prior to pressing together consists mostly of four slot positioning (Pin LAM), hot melt, rivet, and a combination of hot melt and rivet, as well as various product structures employing various positioning methods.
6.Drilling method
Due to the super-thickness of the plate and copper layer caused by the stacked layers, the drill bit is badly worn and prone to breaking; therefore, the number of holes, drop speed, and rotation speed must be adjusted downward.
Conculsion
It is of the utmost importance, when searching for a fabricator for multilayer printed circuit boards (PCBs), to acquire the manufacturer’s capabilities and standard tolerances for these complex boards. Additionally, it is essential to use design for manufacturing (DFM) techniques in order to accommodate those standards. This goes a long way toward generating confidence that the end result will fulfill all of the expectations regarding its functionality, reliability, and performance.
