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 PCB 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.
However, the development of microelectronics is like a torrent that is out of control, and complex multilayer printed circuit boards have also become hot electronic components. Differentiating from the standard two-layer PCB, multilayer PCBs are made up of more layers that are laminated together and insulated by a greater series of prepreg and copper that are stacked on top of each other. Generally, We call a circuit board with more than 4 circuit layers a multilayer PCB, which means that designers can design more circuits inside the PCB. With multi-layer PCB, 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. Usually a 4-layer circuit structure can give PCB good electrical performance and is suitable for most electronic products, but we are still happy to increase its number of layers to obtain higher pressure-bearing capacity.
Why Get a Multilayer PCB Quote from FS Technology
FS Technology is a one-stop PCBA manufacturer, providing PCB manufacturing and PCB assembly services that meet the needs of a large number of engineers. Partnering with FS Technology will get you a great value and fun trip. We produce multi-layer circuit boards from 1-58L for our customers in simpler steps: structuring, lamination and through-hole plating. Most of the time, various unexpected things will happen with the increase in the number of board layers, but we can avoid the risks that customers need to face through strict quality control and commitment. The following are the multi-layer PCB samples produced by FS Technology:
High-quality multi-layer PCB manufacturing
Quality is the foundation of FS Technology, and it is also the hard cornerstone of development. As a turnkey PCBA company that prioritizes quality, we control the quality of PCB from the source. If the quality of the raw materials of the circuit board cannot be guaranteed, the produced PCB may have various issues, such as blistering, delamination, cracking, board warpage, and uneven thickness. So, the quality of raw materials is the premise to ensure the production of high quality multilayer PCB, 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.
In past manufacturing experience, it was found that the quality of different types of multilayer boards varies greatly. For example, ceramic multilayer PCB, metal core multilayer PCB, HDI multilayer PCB are much more difficult and risky to manufacture than ordinary multilayer boards. In order to ensure the quality of production and avoid errors in the subsequent assembly process, we need to ensure the quality of the products produced. 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 PCB manufacturing methods and strict testing.
Perfect Manufacturing Process
The manufacturing process of multilayer PCB is rough as follows:
- Create Inner Image
- Inner Layer Etching
- Multilayer PCB Stackup
- Through Holes and Mounting Holes
- Outer Layer Etching
- Plated Through Hole
- Add Solder Mask
- Draw the Silkscreen Layer
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 4-layer multilayer board 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.
Multilayer PCB Testing
We provide a variety of PCB testing services, including but not limited to the following:
- ICT Test
- Flying Probe Test
- Function Test
- X-ray Test
- Laser Detection
- AOI Inspection
Testing circuit boards is an important part of the production process, whether it is a PCB or a PCBA, especially for a multi layer PCB with a more complex circuit structure. The number of layers of the circuit board is realized by stacking technology. When the number of these layers increases, the manufacturer will face greater manufacturing risks. For this reason, the testing process of multilayer PCB board should be paid attention to.
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 PCB quality. FS Technology promises that no matter how strict the testing process these boards have gone through during production, we will strictly implement the sampling standards provided by customers after the production 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.
Application market for multilayer circuits
Almost all complex electronic devices are inseparable from the presence of multilayer PCBs. In the past operations, FS Technology’s customers are located in more than 70 countries around the world, and their fields are also different. The same thing is that they rely on our strong manufacturing capabilities to gain advantages in their respective fields. Here are some of the industries we have served:
Top-notch multilayer PCB manufacturing capabilities
| Features | Standard |
| Manufacturable layers | Rigid multilayer boards up to 58 layers |
Types of Multilayer PCBs |
|
Surface Treatment Technology |
|
Rich PCB testing |
|
The necessity or not of multilayer PCB
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 multilayer PCB fabrication is to provide more freedom for the circuit layout of complex electronic products. So does your electronic project really need more layers of PCB, let us judge by its advantages and disadvantages:
Multilayer PCB Advantages
Small Size
The reasons for the smaller size of multilayer boards are twofold: reduced surface area and assembly techniques.
Increase the board surface area by increasing the number of layers:
It is easy to understand that large-sized PCBA boards cannot be loaded into electronic equipment. The unfolded quilt is not easy to put in the box, but it is very easy to fold. The principle of multi-layer PCB to obtain more wiring under the same size by increasing the number of layers is similar to this.
Assembling multi-layer PCBA boards by SMT technology:
High precision multilayer PCB are mostly used in cutting-edge applications, and they often appear together with SMT assembly. Traditional plug-in components are difficult to meet micro/nano consumer devices and are replaced by SMD components, which means that we can complete assembly on smaller-sized PCBs.
High Density
The most common application demonstrating the high-density benefits of multilayer PCBs is mobile phones. With the iterative update of the production process, the size of the mobile phone is getting smaller and smaller, but the function has not been affected but improved, thanks to the high-density interconnected (HID) multi-layer PCB used in its design. When we increase the number of layers of the PCB, although its size remains the same at this time, the multilayer HDI PCB increases the wiring density through layering, so that it has more functions, speed and capacity.
More Lightweight
A multi-layer board can do the work of multiple PCBs, while at the same time providing greater durability because it eliminates the need for external hardware and connectors. Those removed connectors reduce the weight of electronics, making them a consideration for small appliances. This hardware and connectors may be susceptible to higher maintenance and replacement in the long run.
In general, the biggest advantage of multilayer circuit boards is definitely their small form factor, lightweight, and increased capabilities for more complex electrical routing. With electronics in this era, simplicity is key, and if we can eliminate some unnecessary parts in a project, it will always be favorable in regard to cost & troubleshooting. In the process of large-scale industrial production, it is difficult to produce and manufacture more designs and then improve the production efficiency of products. Hence, multilayer PCBs may fill that gap and provide a small yet reliable solution for bringing down that aspect of PCBA construction & production.
Multilayer PCB Disadvantages
Design Difficulty
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 complexities of the design that you should keep in mind when considering multilayer PCB.
Right from the start of the design 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. The layers that make up a multilayer PCB are listed below:
- Signal layer: mainly used to place PCBA components or for wiring and soldering. It is divided into the 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.
- Silkscreen 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.
Manufacturing Difficulty
- Alignment between layers
Due to more layers, the difficulty of alignment between layers of multilayer boards becomes higher, and the alignment tolerance between layers is usually controlled at ±75μm. This is due to a variety of factors such as size, substrate material, ambient temperature difference, positioning method, etc.
- Inner layer manufacturing
Usually, when customers are looking for a multilayer circuit board manufacturer, they will observe the materials that the manufacturer can provide. Most of the time they require these materials to have the characteristics of high TG, high speed, high frequency, thick copper, and thin dielectric layer. Higher-end materials will increase the difficulty for manufacturers in inner layer circuit production and graphic size control, such as: low pass rate; open circuit or short circuit; inner layer AOI missing test; poor exposure, etc.
- Lamination
When multiple inner core boards and semi-cured sheets are stacked, manufacturing defects such as slippage, delamination, resin voids and air bubble residue are easily generated during lamination production. To avoid this problem, we need to consider the heat resistance and voltage resistance of the material and set a reasonable multi-layer PCB lamination program.
Delivery and Cost
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 PCB is typically more expensive when it comes to professional manufacturing and ordering the boards and will take more time to manufacture than ordinary two-layer PCB.
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 PCB, a thorough check of the manufacturer is performed to ensure that the requirements set by the company match the requirements for your order.
Summarize
As mentioned briefly above, multilayer PCBA board is 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 PCB 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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