Printed circuit boards (PCBs) are the core of most electronics today, determining basic functions through combinations of components and wiring mechanisms. Most PCBs of the past were relatively simple and limited by manufacturing techniques, while today's PCBs are much more complex. From advanced flexible options to odd-shaped varieties, PCBs are much more varied in nowadays' world of electronics. Of particular popularity, however, are multilayered PCBs.
While PCBs for simple electronics with limited functions are usually composed of a single layer, more sophisticated electronics, like computer motherboards, consist of multiple layers. These are what are called multilayer PCBs. With the increasing complexity of modern electronics, these multilayer PCBs have become more widespread than ever before, while manufacturing techniques have enabled them to size down significantly.
Read on to learn more about multilayer PCBs, their uses and advantages in the world of modern electronics.
What Is a Multilayer PCB?
The definition of multilayer PCB is a PCB that is made with three or more conductive copper foil layers. These appear as several layers of double-sided circuit boards, laminated and glued together with layers of heat-protective insulation between them. The entire construction is arranged so that two layers are placed on the surface sides of the PCB to connect to the environment. All electrical connections between the layers are achieved with vias such as plating through holes, blind and buried vias. Application of this method then leads to the generation of highly complex PCBs of varying sizes.
The multilayer PCB came into being due to the evolving changes in the electronics industry. The functions of electronics have become progressively more sophisticated over time, requiring more complex PCBs. Unfortunately, PCBs were limited by problems like noise, stray capacitance and crosstalk, and therefore needed to follow certain design constraints. These design considerations made it difficult to get a satisfactory level of performance from a single or even double-sided PCB - thus the multilayer PCB was born.
Packing the power of a double-layer PCB into a format that's a fraction of the size, multilayer PCBs are becoming increasingly popular in electronics. They come in a wide range of sizes and thicknesses to accommodate the needs of their expanding applications, with variants ranging anywhere from four to twelve layers. Layers most often come in even numbers, since odd numbers of layers can cause issues in the circuit like warping, and are no more cost-effective to produce. Most applications require between four and eight layers, though applications like mobile devices and smartphones tend to use around twelve layers, and some professional PCB manufacturers boast the ability to produce multilayer PCBs with nearly 100 layers. Multilayer PCBs with that many layers are rare to see, however, as they are extremely cost-inefficient.
While they do tend to be more expensive and labor-intensive to produce, multilayer PCBs are becoming an essential part of modern technology. This is primarily due to the host of benefits they offer, particularly in comparison to single and double-layer varieties.
Multilayer PCB Benefits
From a technical point of view, multilayer PCBs present several advantages in design. These benefits multilayer PCBs present include:
• Small Size: One of the most prominent and lauded benefits of using multilayer PCBs lies in their size. Because of their layered design, multilayer PCBs are inherently smaller than other PCBs with similar functionality. This presents a major benefit to modern electronics, as the current trend is working toward smaller, more compact yet more powerful gadgets like smartphones, laptops, tablets and wearables.
• Lightweight Construction: With smaller PCBs comes less weight, especially as the multiple connectors required to interlink separate single and double-layered PCBs are eliminated in favor of a multilayered design. This, again, is beneficial for modern electronics, which are geared more toward mobility.
• High-Quality: Due to the amount of work and planning that must go into the creation of multilayer PCBs, these types of PCBs tend to be better in quality than single and double-layer PCBs. They also tend to be more reliable as a result.
• Increased Durability: Multilayer PCBs tend to be durable by their nature. Not only do these multilayer PCBs have to withstand their own weight, but they must also be able to handle the heat and pressure used to bind them together. On top of these factors, multilayer PCBs use multiple layers of insulation between circuit layers, binding it all together with prepreg bonding agent and protective materials.
• Enhanced Flexibility: Though this does not apply to all multilayer PCB assemblies, some do use flexible construction techniques, resulting in a flexible multilayer PCB. This can be a highly desirable trait for applications where mild bending and flexing may occur on a semi-regular basis. Again, this does not apply to all multilayer PCBs, and the more layers incorporated into a flexible PCB, the less flexible the PCB becomes.
• More Powerful: Multilayer PCBs are extremely high-density assemblies, incorporating multiple layers into a single PCB. These close-quarters enable boards to be more connective, and their innate electrical properties allow them to achieve greater capacity and speed despite their smaller size.
• Single Connection Point: Multilayer PCBs are designed to work as a singular unit, rather than in tandem with other PCB components. As a result, they have a single connection point, rather than the multiple connection points required to use multiple single layer PCBs. This proves to be a benefit in electronic product design as well since they only need to include a single connection point in the final product. This is particularly beneficial for small electronics and gadgets designed to minimize size and weight.
These benefits make multilayer PCBs highly useful in a variety of applications, particularly mobile devices and high-functioning electronics. In turn, with so many industries turning to mobile solutions, multilayer PCBs are finding a place in an increasing number of industry-specific applications.
Multilayer PCB Disadvantages
The benefits of multilayer PCBs are numerous, making them applicable to a wide variety of advanced technologies. However, these types of PCBs aren't appropriate for all applications. In fact, several drawbacks can outweigh multilayer PCB advantages, especially for electronics of lower cost and complexity. These disadvantages include the following:
• Higher Cost: Multilayer PCBs are significantly more expensive than single and double layer PCBs at every stage of the manufacturing process. They are difficult to design, taking an extensive amount of time to work out any potential problems. They also require a highly complex manufacturing process to produce, which takes a great deal of time and labor on the part of assembly personnel. Additionally, due to the nature of these PCBs, any mistake in the manufacturing or assembly process is prohibitively difficult to rework, resulting in either additional labor costs or scrap material expenses. On top of it all, the equipment used to produce multilayer PCBs is quite expensive because it is still a relatively new technology. For all those reasons, unless small size is an absolute necessity for the application, cheaper alternatives may be a better choice overall.
• Complicated Production: Multilayer PCBs are more difficult to produce, requiring much more design time and careful manufacturing techniques than other PCB types. This is because even small flaws in the PCB's design or manufacture could render it useless.
• Limited Availability: One of the largest issues with multilayer PCBs is the expenses of the machinery needed to produce them. Not all PCB manufacturers have the funds or the necessity for this machinery, so not all PCB manufacturers carry it. This limits the number of PCB manufacturers available to produce multilayer PCBs for clients. Thus, it's best to carefully inquire a PCB manufacturer's capability in terms of multilayer PCBs prior to deciding it as your contract manufacturer.
• Skilled Designer Required: As previously discussed, multilayer PCBs require extensive design beforehand. Without previous experience, this can be problematic. Multilayer boards require interconnection between layers, but must simultaneously mitigate crosstalk and impedance issues. A single problem in the design can result in a non-functioning board.
• Production Time: With increased complexity comes more manufacturing requirements. This plays into a key issue with multilayer PCBs' turnover rate – each board requires a significant amount of time to produce, resulting in more labor costs. Additionally, it possibly leads to longer periods between when an order is placed and when the product is received, which can be a problem in some circumstances.
However, these issues do not diminish from the utility of multilayer PCBs. While they tend to cost more than a single layer PCB, a multilayer PCB claims many advantages over this type of printed circuit board.
Advantages of Multilayer PCBs over Single Layer Alternatives
When compared to single layer alternatives, the advantages of multilayer PCBs become even more pronounced. Some of the key improvements multilayer PCBs offer include the following:
• Higher Assembly Density: While single layer PCBs' density is limited by their surface area, multilayer PCBs multiply their density through layering. This increased density allows greater functionality, improving capacity and speed despite the smaller PCB size.
• Smaller Size: Overall, multilayer PCBs are smaller in size than single layer PCBs. While single layer PCBs must increase the surface area of the circuit by increasing size, multilayer PCBs increase surface area through the addition of layers, decreasing overall size. This allows for higher-capacity multilayer PCBs to be used in smaller devices, while high-capacity single layer PCBs must be installed into larger products.
• Lighter Weight: The integration of components in a multilayer PCB means less of a need for connectors and other components, resulting in a lightweight solution for complex electrical applications. Multilayer PCBs can accomplish the same amount of work as multiple single-layer PCBs, but does so at a smaller size and with fewer connecting components, reducing weight. This is an essential consideration for smaller electronics where weight is a concern.
• Enhanced Design Functionality: Overall, multilayer PCBs are capable of being more than the average single layer PCB. With more incorporation of controlled impedance features, greater EMI shielding and overall improved design quality, multilayer PCBs can accomplish more despite their smaller size and lesser weight.
So, what do these factors mean when deciding between a multilayer and single layer construction? Essentially, if you're looking to produce a small, lightweight and complex device where quality is essential, a multilayer PCB is likely your best choice. However, if size and weight are not primary factors in your product design, then a single or double layer PCB design may be more cost-effective.
Multilayer PCB Applications
The advantages and comparisons discussed above beg the question: what's the use of multilayer PCBs in real world? The answer is just about any use.
For numerous industries, multilayer PCBs have become the preferred option for a variety of applications. Much of this preference derives from the continuous push across all technology toward mobility and functionality. Multilayer PCBs are the logical step in this progression, achieving greater functionality while reducing size. As such, they've become fairly ubiquitous, used in many technologies including:
• Consumer Electronics: Consumer electronics is a broad term used to cover a wide range of products used by the general public. This tends to include products used on a daily basis, such as smartphones and microwaves. Each of these consumer electronics contains a PCB, but an increasing proportion of them are using multilayer PCBs instead of standard single layers. Why? Most of the reason lies in consumer trends. People in the modern world tend to prefer multi-function gadgets and smart devices that integrate with the rest of their lives. From universal remotes to smartwatches, these types of devices are fairly common in the modern world. They also tend to use multilayer PCBs for their increased functionality and smaller size.
• Computer Electronics: Everything from servers to motherboards uses multilayer PCBs, primarily for their space-saving attributes and high functionality. With these applications, performance is one of the most essential characteristics of a PCB, whereas cost is relatively low on the list of priorities. As such, multilayer PCBs are an ideal solution for many technologies in this industry.
• Telecommunications: Telecommunication devices often use multilayer PCBs in numerous general applications, such as signal transmission, GPS and satellite applications. The reason for this lies primarily in their durability and functionality. PCBs for telecommunications applications are often either used in mobile devices or towers outdoors. In such applications, durability is essential while still maintaining a high level of functionality.
• Industrial: Multilayer PCBs do prove more durable than several other options currently on the market, making them a good choice for applications where rough handling may be a daily occurrence. As such, multilayer PCBs have become popular in several industrial applications, most notable of which are industrial controls. From industrial computers to control systems, multilayer PCBs are used throughout manufacturing and industrial applications to run machinery, favored for their durability as well as their small size and functionality.
• Medical Devices: Electronics is becoming an increasingly essential part of the healthcare industry, functioning in every corner of the industry from treatment to diagnosis. Multilayer PCBs are particularly favored in Medical industry for their small size, lightweight nature and impressive functionality compared to single-layer alternatives. These benefits have led to multilayer PCBs being used in modern X-ray equipment, heart monitors, CAT scan equipment and medical testing devices etc.
• Military and Defense: Favored for their durability, functionality and low weight, multilayer PCBs are useful in high-speed circuits, which is becoming an increasing priority for military applications. They're also favored due to the defense industry's increased movement toward highly compact engineering designs, as the small size of multilayer PCBs leaves more room for other components to flourish existing functions.
• Automotive: Cars are relying on electronic components more and more in the modern era, especially with the rise of electric cars. With everything from GPS's and onboard computers to headlight switches and engine sensors controlled by electronics, using the right kinds of components becomes increasingly essential in automotive design. This's why many auto manufacturers start to favor multilayer PCBs over other alternatives. While they are small and durable, multilayer PCBs are also highly functional and relatively heat-resistant, making them a good fit for the internal environment of an automobile.
• Aerospace: Like cars, jets and rockets rely heavily on electronics in the modern era, all of which must be extremely precise. From the computers used on the ground to those used in the cockpit, aerospace PCB applications must be reliable, able to handle the stresses of atmospheric journeys while simultaneously making enough room for the rest of the surrounding equipment. Multilayer PCBs present an ideal solution in this case, with plenty of protective layers to keep heat and outside stress from damaging the connections, as well as the ability to be made from flexible materials. Their higher quality and functionality also contributes to this utility in the aerospace industry, as aerospace companies prefer to use the best materials possible to keep their personnel and equipment safe.
• And Many More! Multilayer PCBs are used in a wide variety of other industries, including the science and research industry and even home appliances and security. Everything from alarm systems and fiber optic sensors to atomic accelerators and weather analysis equipment uses multilayer PCBs, taking advantage of the space and weight savings offered by this PCB format, as well as their heightened functionality.
Why Are Multilayer PCBs So Widely Used?
The specific applications listed above represent only a fraction of multilayer PCBs applied throughout the industry. But why are they used so widely?
Much of the favoritism toward multilayer PCBs lies in industry trends. With electronics progressing ever toward miniaturization yet multi-functional options, the internal components of those electronics must follow the same trend. While single and double-sided PCBs have proven limited in their ability to balance size and functionality, multilayer PCBs provide a comprehensive solution.
While there are several drawbacks to using multilayer PCBs over single and double-layer options, such as increased costs, design times and production inputs, these costs are becoming more accepted in today's world. Functionality is largely favored over cost, and people are willing to pay more for high capacity electronics. Additionally, as the technology becomes increasingly mainstream, production techniques and machinery will eventually become less expensive, especially as new techniques arrive in the industry.
With those irreversible trends and continuing progress of technology, many expect to see multilayer PCBs become even more abundant in the future.
Multilayer PCB Manufacturing and Assembly at Favorable Prices with PCBCart
With technology continuing to progress and the number of multilayer PCB uses expected to expand, your company needs to invest in those trends and increase your focus on multilayer solutions. Part of this increased focus should include partnering with a quality multilayer PCB manufacturer and assembler. With such a solution, your company will be perfectly poised to handle any multilayer PCB project that comes your way. PCBCart can help you get there.
PCBCart is a custom PCB solutions provider, serving companies across the world in PCB manufacturing and assembly services. We help companies from parts sourcing to testing, all the while remaining compliant with IPC Class 3, RoHS and ISO9001:2008 standards. We'll be with you every step of the way throughout the process of producing your multilayer PCB, providing expertise and advice when needed. Our experienced team has produced thousands of multilayer PCBs varying in design and complexity. No matter how intricate the design or how extensive your needs, PCBCart can help.
Learn more about PCBCart and our manufacturing and assembly capabilities by exploring our manufacturing and assembly capabilities by clicking following page links. If you want to learn more about how we can help you individually, feel free to contact us directly with questions.
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