Multilayer PCBA

FS Technology is an expert in fabricating different circuit boards, including multi-layer PCBA. By reading this article, you will better understand FS Technology's manufacturing capabilities.

Catalog of PCB Types

Definition of Multilayer Circuit Boards

PCBs are an essential hardware component of almost all electronic & electrical devices, as it allows for a complete (closed) circuit to be made between electronic components. Predominantly with the use of conductive copper tracks & traces on a PCB, an electrical connection can then be made from one point to another. Typically, you will find that many PCBA are two-layer boards, meaning that there is an inner core layer (substrate) in the center of the board that is sandwiched between first a solder mask on the outermost layer (giving it its color) and a copper coating on the subsequent bottom layer, giving the traces its conductive properties. Differentiating from the standard two-layer PCBA, multilayer PCBs are made up of four or more layers that are laminated together and insulated by a greater series of prepreg and copper that are stacked on top of each other. With multilayer PCBA, there is a repeated pattern of prepreg and core (substrate) material in between the outermost top & bottom layers, offering several advantages to both through-hole and surface mount designs.

Among different types of PCBA, the manufacturing process of multi-layer printed circuit boards is more complicated, and it is mainly composed of the following layers:

Signal layer: mainly used to place PCBA components or for wiring and soldering. It is divided into top layer, middle layer and bottom layer.

Internal power supply: Usually we also call it the internal electrical layer, which is specially used to arrange power lines and ground lines.

Mechanical layer: Place physical dimension lines, data, via information and other indicative information for manufacturing PCBA boards.

Solder Mask: A copper-free area used to place pads or other objects, including top and bottom layers.

Silk screen layer: used to mark the outline, number, and other text information of components.

System Work Layer: Used to display information that violates the multi-layer PCB design rule check.

Quality assurance of multi-layer PCBA

Quality is the foundation of FS Technology, and it is also the hard cornerstone of development. The quality of different types of multi-layer boards varies greatly. In order to avoid difficulties in the subsequent assembly of finished products, we need to ensure the quality of the produced products. Professionals can easily judge the quality of the printed circuit board after receiving the product, but this will undoubtedly slow down the progress of the entire project. FS Technology is here to show you our quality control standards through advanced PCBA manufacturing methods and strict testing.

Multilayer PCB Manufacturing Process

To start with, the base of a standard two-layer PCB is the substrate material (core), which is oftentimes fiberglass epoxy resin. The next layer is the copper which is laminated onto both sides of the substrate to establish electrical conductivity and finally, the solder mask is laminated onto both sides of the copper to protect the copper layer against oxidation and to help make soldering easier. If we take a four-layer PCB for example, it is manufactured by essentially combining two standard two-layer PCB boards together, oftentimes with lamination under high heat and pressure (compression) with a hydraulic press. Of course, there will be multiple layers of prepreg, copper, and core material that will be stacked on top of each other in between the two outermost layers (making up the multiple layers), which will all then be compressed together to make a multilayer PCB. FS Technology’s PCB manufacturing process is nowadays all done by high-tech machinery which, through the use of software, can be done effortlessly and with close to zero inaccuracies, making it suitable for mass production.

FS Technology’s testing standards

As a turnkey PCBA company that prioritizes quality, FS Technology controls the quality of PCBA from the source. In our opinion, the quality of raw materials is the premise to ensure the production of high-quality PCBA, so strict incoming inspection is the first step of service. We maintain a zero-tolerance attitude towards product defect issues. Once a problem is found, it will immediately register a report and develop a solution. If the quality of the raw materials of the circuit board cannot be guaranteed, the produced PCBA may have various issues, such as blistering, delamination, cracking, board warpage, and uneven thickness.

In addition to the concern of raw materials, the production process of multi-layer PCBA also needs to be strictly controlled. In the production workshop of FS Technology, each production process is equipped with a special quality inspection post to ensure that each process has the implementation of operating procedures, to facilitate the overall control of PCBA quality.

No matter how strict the PCB testing process is before or during the production process, FS Technology will strictly implement the sampling testing standards according to the customer’s requirements after the production of the circuit board is completed. If the qualified rate of product sampling inspection is up to standard, it will be approved to leave the factory, otherwise, comprehensive inspection and maintenance will be carried out.

Significance of Multilayer PCB Fabrication

The core of Moore’s Law states that the number of transistors that can be accommodated on an integrated circuit doubles every 18 months. As the packaging density of integrated circuits increases year by year, the demand for electronic products develops in the direction of multi-function and miniaturization, and the use of multi-layer boards becomes necessary. In the layout of printed circuit boards, unforeseen design problems such as noise, stray capacitance, crosstalk, etc. appear. Therefore, minimizing the length of the signal lines and avoiding parallel routes has become a difficulty that the circuit board design must face. Sadly, no matter whether it is a single or double layer, the designers are not able to deliver a satisfactory answer due to the limitation of the number of crossovers that can be achieved. The manufacture of multilayer circuit boards has become imperative in an environment of massive interconnection and crossover requirements. The original intention of multi-layer PCBA fabrication is to provide more freedom for the circuit layout of complex electronic products. FS Technology has sorted out the advantages and disadvantages of this type of circuit board:

Advantages of multilayer PCBA

The biggest advantage of multilayer circuit boards is definitely their small form factor, light weight, and increased capabilities for more complex electrical routing. Due to the generally reduced size and compactness of multilayer circuit boards, they are commonly found alongside surface mount components (SMT) and in many micro/nano consumer devices (e.g., cellphones). One common industrial application of multilayer PCBA which showcases its advantages is with mobile phones. As technology improves over the generations, common devices such as mobile phones are becoming increasingly slimmer in width (a much smaller footprint), all thanks to more multilayer PCB layers being used in their design. Plus, although the size of multilayer circuit boards may seem much smaller, their functionality as a PCB is not compromised but instead improved, as multilayer circuit boards still allow for high speed & high capacity electronics in such a tight surface area. Therefore, during mass industrial production, a higher volume of designs can be produced and manufactured, in turn, increasing the production efficiency of a product. Compared to using multiple two-layer PCBA for example, a multilayer PCBA can also offer higher durability as it eliminates the need for external hardware and connectors that may be susceptible to higher maintenance and replacement in the long run. With electronics in this era, simplicity is key, and if we can eliminate the need for excessive hardware being used in a project as well as encourage a minimalistic design, it will always be favorable in regard to cost & troubleshooting. Hence, multilayer PCBs may fill that gap and provide a small yet reliable solution for bringing down that aspect of PCBA construction & production.

Disadvantages of multilayer PCBA

Even though multilayer circuit boards present themselves with many enticing advantages for an electronic hobbyist or even an avid designer, there are certainly a few drawbacks that you should keep in mind when considering multilayer PCBA. Right from the start of the design and fabrication process, there definitely is a learning curve involved in designing a multilayer PCB compared to an ordinary PCB that you may have made in the past, as it involves more complex routing & design features to keep in mind. Errors are likely to come up if your boards are not checked properly and many designers usually work in a team to cross-verify their designs before sending them to production as troubleshooting faults may be very time-consuming and costly. In addition, multilayer PCBA are typically more expensive when it comes to professionally manufacturing and ordering the boards and will take more time to manufacture than ordinary two-layer PCBA. This may be due to the extensive functional checking & tests that need to be performed on the boards before they are ready to be produced, as correcting errors post-production is simply not feasible. Therefore, it is advisable that, before you order a multilayer PCBA, a thorough check of the manufacturer is performed to ensure that the requirements set by the company match the requirements for your order.

As mentioned briefly above, multilayer PCBA are extremely common in many consumer electronic devices, from mobile phones to graphic cards to even state-of-the-art medical equipment. The sheer compactness, reliability & durability of multilayer PCBA make them considerably more suitable for these applications compared to traditional single or double-layer boards, especially in an industrial setting where versatility, consistency & high performance is needed. Furthermore, some other applications of multilayer PCBA include aerospace technology, navigation equipment (GPS), communications (radios), automotive machinery, and military-grade equipment. All of these industrial applications of multilayer PCBA do not necessarily mean that you should not use them for your own electronic project, but before you proceed with selecting the route of multilayer PCBA, you should be aware of both the pros and cons of them before choosing the most appropriate option. It is also necessary to be well-informed of both your design & the manufacturer of your PCBA. Nevertheless, single or double-layer PCB certainly still do have a place in electronics today and may also be perfect for various types of applications that do not require the use of multilayer PCB.

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