PCBs, or Printed Circuit Boards, are an essential component in modern electronic devices. They are thin boards made up of an insulating material, often fiberglass reinforced with epoxy, that holds an array of components and interconnects them using conductive copper traces. PCBs come in different shapes and sizes, and they can be single-layered, double-layered, or multi-layered.
Multilayer PCBs are a type of PCB that contain multiple layers of conductive traces and insulating material, usually more than two. They can range from 4 to 50 or more layers, with the most common ones being 6-layer and 8-layer PCBs. They offer numerous advantages over monolayer or double-layer PCBs, including increased functionality, improved signal routing, and thermal management. Multilayer PCBs are best suited for applications that require intricate circuitry, high-speed communications, small form factor, and high density of components.
In multilayer PCBs, the conductive layers are separated by an insulating dielectric layer. One or more layers can also serve as power and ground planes. The different layers are interconnected through vias, small holes drilled into the board, or through-hole plated, chemically coated or laser-drilled connections. Advanced devices also utilize blind vias, which connect only a subset of layers, buried vias, which are hidden beneath the outer layers, and microvias, a tiny type of through-hole connection that can be made using lasers.
The fabrication of multilayer PCBs requires a complicated process that involves specialized equipment and expertise. The process includes layer stacking, lamination, via drilling, electroplating, solder masking, and surface finish. Quality control is an essential aspect of the manufacturing process to ensure the board’s reliability, functionality, and compliance with industry standards.
In addition, Multilayer 8 layer PCBs find extensive use in different industries that require advanced electronic circuitry, such as telecommunications, aerospace, automotive, medical devices, and industrial control systems, among others. Their capability to handle faster signals, more components, and high power density allows them to meet the demands of modern electronic applications
In this article, we’ll explore the features of an eight-layer PCB and the process of its manufacture, stack-up, design, advantages, disadvantages and applications.
What Is 8 Layer PCB ?
As a PCB layout engineer, it is essential to have a thorough understanding of the different types of printed circuit boards. One such PCB is the 8-layer PCB, which is distinct from the more commonly used single or double-layer PCBs. An 8-layer PCB comprises eight layers of conductive material with integrated dielectric material.
One of the key advantages of an 8-layer PCB is its capability to accommodate a large routing area, which enables it to support multiple applications and power isles. The design of 8-layer PCBs ensures a durable and strong connection between all layers and offers ample routing space to the prevailing power islands to enable a more complex arrangement. By utilizing the upswings of two planes, the stack-up configuration of 8-layer PCBs considerably improves the electromagnetic compatibility execution.
An 8-layer PCB is commonly used in small electronic devices such as cell phones, digital cameras, radios, and passive switch boxes. It can also be integrated into backplanes and motherboards as required. However, as a PCB layout engineer, it is crucial to be mindful of the potential hazards associated with 8-layer PCBs and emphasize the importance of proper design to ensure its safe operation. Although not as common as other PCB types, the 8-layer PCB continues to be widely used in numerous small devices.
Design Considerations for 8 Layer PCBs
The design considerations for 8 layer PCBs might include the following factors:
● Stackup and layer arrangement: The stackup and arrangement of the layers in an 8 layer PCB should be carefully planned to minimize noise, crosstalk, and signal integrity issues. The designer should consider the placement of power and ground planes, signal layers, and other components.
● Routing and trace width: Routing and trace widths must be optimized to ensure signal integrity and minimize signal loss. The designer should consider the impedance of the traces and the effects of via stubs.
● Power distribution: Power distribution and decoupling capacitors must be carefully designed to provide stable power to all components on the board. The designer should consider the placement of decoupling capacitors and the use of power planes for more efficient power distribution.
● Thermal management: Thermal management is crucial in high-density 8 layer PCBs. The designer should consider the placement of components and heat sinks, as well as the use of thermal vias to improve heat dissipation.
● Manufacturing constraints: The designer should consider manufacturing constraints such as minimum trace widths and clearance, minimum annular ring size, and the limitations of the fabrication process. The designer should also ensure that the design can be realistically manufactured within the budget.
● Signal integrity analysis: Signal integrity analysis should be performed to ensure that the design meets the required performance standards. The designer should consider the use of tools such as impedance calculators, signal simulators, and electromagnetic simulation software to optimize the design.
Manufacturing Processes for 8 Layer PCBs
The manufacturing processes for 8 layer PCBs involve the following steps:
● Preparing the inner layer: The first step involves drilling or punching holes into the substrates and preparing copper-clad laminate sheets for the inner layer of the PCB.
● Applying the copper layers: The next step involves applying the copper foil to the inner layer substrate using a lamination process.
● Imaging and etching: After applying the copper layer, the next step is to print the circuit board pattern or layout onto the substrate using a photographic process. The board is then etched to remove the unwanted copper layer, leaving the circuit pattern on the substrate.
● Lamination: The inner layers of the PCB are then laminated together, along with any additional prepreg layers that may be required.
● Drilling: The next step is to drill holes or vias into the substrate to provide pathway for inter-layer connections.
● Plating: The holes or vias are then plated with copper to create electrical connections between the copper layers.
● Outer layer imaging and etching: The outer layers of the PCB are then printed and etched using the same process as the inner layers.
● Surface finish: The surface of the PCB is coated with a finish, such as lead-free solder, immersion gold, or HASL, depending on the intended application.
● Solder mask and legend printing: The PCB is then printed with a solder mask, which protects the copper traces from corrosion and short circuits, and with a legend, which labels the components and outlines their locations.
● Electrical testing: After the manufacturing is completed, the PCB is electrically tested to ensure that it conforms to the design specification and meets the quality standards.
This process is not exhaustive and can vary depending on specific manufacturing requirements and material considerations.
Testing and Quality Control Measures for 8 Layer PCBs
Testing and quality control measures for 8 layer PCBs are critical to ensure their reliability and functionality. Here are some of the common testings and measures:
● Electrical testing: The primary control measure for 8 layer PCBs involves electrical testing to ensure they meet the design specifications. The most common electrical tests include continuity testing, resistance testing, and impedance testing.
● Manufacturing process control: A good quality control program should include monitoring and controlling parameters throughout the manufacturing process to ensure that the PCBs are fabricated according to the design specifications. These parameters can include trace width, spacing, and alignment, drilling tolerance, and layer-to-layer registration.
● Visual inspection: Visual inspection is a key test for ensuring that the PCBs have no physical defects such as scratches, cracks, or damaged copper traces. This can include inspections during various stages of manufacturing, such as after etching and plating, before and after lamination, and before final testing.
● Microscopic inspection: Microscopic inspections can help identify physical defects that cannot be seen with the naked eye. This can include inspections of the PCB surface, metallization, and cross-sectional and thickness measurements.
● Reliability testing: Reliability testing involves exposing the PCB to various environmental conditions, such as temperature, humidity, and vibration, to assess its performance under stress and identify any potential weaknesses.
● Dynamic testing: Dynamic testing includes signal integrity tests to ensure signal transmission quality and timing, and susceptibility tests, which evaluate how the board responds to electromagnetic interference.
● Component verification and testing: The PCB designer should verify the quality and reliability of the components used on the board, and ensure that they are compatible with the PCB and the operating environment. Component testing can include resistance, temperature coefficient testing, and stability tests.
Applying these testing and quality control measures can help ensure high-quality 8 layer PCBs that provide reliable functionality to the intended application.
Advantages and Disadvantages of Using 8 Layer PCBs
Advantages of using 8 layer PCBs:
● High density: 8 layer PCBs offer high-density interconnects, enabling complex circuits and high-speed signal routing.
● Reduced noise and crosstalk: They provide better signal isolation and reduce noise and crosstalk between the layers.
● Improved thermal performance: The additional layers provide more space for power and ground planes, which enhances thermal distribution to meet the high thermal demands of advanced electronics devices.
● Flexibility: The additional layers offer increased flexibility in component placement and routing, which can improve performance and reduce system size.
● Reduced electromagnetic interference (EMI): 8 layer PCBs offer better EMI control since they separate the signal and power layers.
Disadvantages of using 8 layer PCBs:
● Costly: 8 layer PCBs are more complicated and expensive to fabricate than simpler PCB types, thereby increasing the overall cost for the end product.
● Difficult to fabricate: More layers mean more manufacturing steps and reduced manufacturability, particularly for PCBs with higher layer counts, which require advanced dicing, drilling, and plating techniques.
● Signal integrity challenges: While 8 layer PCBs offer superior signal integrity due to their improved isolation and reduced crosstalk, they also require greater attention to signal routing and impedance control.
● Design complexity: 8 layer PCBs require more complex design tools and processes that may result in increased design complexity, reduced flexibility, and a more time-consuming design process.
● Testing overhead: Testing becomes more complicated when dealing with such a high layer count board, which adds an extra overhead in terms of test setup, costs and debug.
Applications of 8 Layer PCBs in Different Industries
8 layer PCBs are widely used in various industries that require advanced electronic circuitry and high-level functionality. Here are some of the common applications of 8 layer PCBs in different industries:
● Telecommunications: 8 layer PCBs are commonly used in the telecommunications industry for building base stations, routers, telephone exchange systems, and other advanced communication equipment. The high-density interconnects and signal precision are well suited for this industry.
● Military and aerospace: 8 layer PCBs are commonly used in the military and aerospace industries for building complex electronics equipment, including avionics systems, navigation equipment, and missile guidance systems. These applications require high functionality and reliability, and 8 layer PCBs can deliver both.
● Medical devices: 8 layer PCBs are used in the medical device industry for various advanced equipment, including diagnostic equipment, imaging devices, and patient monitoring devices. The high-density interconnects and better control over signal integrity provide precision and accuracy in this industry.
● Automotive: 8 layer PCBs are used in automotive systems for building sensors, control modules, and other complex electronic devices. The reliability and automotive-grade component requirements to thrive in harsh environments require high-performance PCBs with excellent signal stability.
● Industrial equipment: 8 layer PCBs are also used in industrial equipment for building control and monitoring systems, automation equipment, and other electronic devices. High-density interconnects and precision signal integrity is well suited to provide correct control and feedback in industrial control processes.
JarnisTech Factory: Multilayer PCB Manufacturing Capabilities
|Specifications||Multilayer PCB Capabilities|
|PCB layers||4 to 60 Layers|
|Delivery Time||1 Day To 2weeks|
|Final board thickness||0.4MM-6.0MM|
|Materials||FR4, polyimide, aluminum, ceramics, PTFE|
|Tg (FR4 multilayer PCB)||135°C~185°C|
|HDI stackup||1+N+1, 2+N+2, 3+N+3,4+N+4|
|Surface Finish||ENIG,Immersion Silver, Plated Gold, Immersion Tin,etc….|
|Solder mask Color||Gree, Blue,Red,Yellow,White, black..|
|Silk Screen Color||Gree, Blue,Red,Yellow,White, black..|
|Quality/Test||ISO/CE/UL/IPC Class2 /IPC Class3|
Why Use A Standard 8-Layer PCB Stack Up
In the realm of PCB design, single-layer and double-layer PCBs are the most frequently used types. Often, double-layer PCBs are sufficient to meet the project requirements. To minimize the risk of unnecessary problems, it is advisable to keep the PCB design uncomplicated. However, there are circumstances when a multilayer PCB design is essential, with 8-layer stack-ups being a good practice for certain applications.
Multilayer PCBs usually consist of three or more conductive layers sandwiched between the insulating core and prepregs as per the PCB stack-up configuration. The prepregs, which are raw insulation materials, typically FR4, are placed over copper layers attached to the core.
As the size of electronic components reduces and the signal speed of electronic devices increases, multilayer PCBs are becoming more feasible. A standard PCB stack-up has at least four copper layers, providing sufficient room between the components and outer layers to facilitate functionality.
PCB designers implement multilayer PCBs to improve signal integrity. In a standard 8-layer PCB stack-up configuration, the signal layers are separated by ground and power planes, which minimize crosstalk among signal layers, hence improving the overall signal integrity.
Benefits of Using 8-Layer PCB Stack Up
Employing 8-layer printed circuit board stack-ups presents numerous advantages, as highlighted below:
● Adequate space for routing: The 8-layer stack-up provides sufficient space for routing signals, which is particularly crucial for boards with a high pin density.
● Improved signal integrity: The 8-layer stack-up enables designers to isolate signals, ensuring minimal interference between different signal types and higher signal integrity.
● Enhanced thermal performance: The 8-layer PCB stack-up provides more comprehensive ground planes, which can help dissipate heat more efficiently, enhancing the board’s thermal performance.
● Decreased electromagnetic interference (EMI): The 8-layer stack-up allows designers to implant power and ground planes, minimizing EMI and other signal interference issues.
● Design flexibility: The extra layers in the 8-layer stack-up offer additional design flexibility, allowing designers to incorporate more complex and intricate traces.
As a result, the 8-layer PCB stack-up offers a range of benefits, including adequate space for routing, improved signal integrity, enhanced thermal performance, decreased EMI, and more design flexibility. These benefits make 8-layer PCB stack-ups a preferred choice for numerous applications in various industries.
Choose JarnisTech to Meet Your PCB Layer Stacking-up Needs
The following picture shows how to make an 8-layer PCB stack-up:
Standard 8L Stacks Up To 1.0MM Standard 8L Stacks Up 1.60MM
Standard 8L Stacks Up To 2.0MM Standard 8L Stacks Up 2.4mm.
Standard 8L Stacks Up 3.0mm.
The above-described 8-layer PCB stack-up is designed with the best manufacturing features in mind to ensure optimal product quality while keeping production costs reasonable. To prevent potential quality issues during the PCB assembly process for circuits with 8 or more layers, it is advisable to use Tg170 laminate material.
The 8-layer standard layer build-up comprises copper thickness of 1/1/1/1/1/1/1/1 oz, which is the most suitable manufacturing feature for producing multilayer PCBs.
We also offer customers the option of a custom stack-up or an impedance-controlled 8-layer circuit board. Additionally, customers can request a stack-up with copper thickness of 2oz or more by sending an email to [email protected].
Our aim is to provide customers with quality PCB products that meet their unique requirements and specifications. Please feel free to reach out to us with any inquiries, and we will be happy to assist you in selecting the best PCB stack-up for your specific needs.
Raw Materials Choices for 8 Layer PCBs
In PCB manufacturing, raw laminate is one of the most crucial and expensive materials required for multilayer boards. The price and delivery times of PCBs depend largely on raw laminate availability and cost. As boards require a significant amount of materials, optimizing the size of designs is essential, as even slight variations in size can significantly affect the overall cost.
When comparing the properties of different laminates, it is important to consider several characteristics. These include the glass transition temperature (Tg), temperature of decomposition (Td), Dielectric Constant (Dk), and Dissipation Factor (Df).
● The Tg suggests the temperature at which the material transitions from its hard, glassy state to a soft, rubber-like state.
● The Td is the temperature at which the laminate chemically decomposes. In contrast, Dk is a measure of the relative permittivity of an insulating material, indicating its ability to store energy in an electrical field.
● Lower Dk values are preferred for insulation purposes, although higher Dk values may be more desirable for RF applications.
● Finally, Df indicates material efficiency by displaying energy loss for specific modes of oscillation, such as electromechanical, mechanical, or electrical.
Since our fabrication facilities are located in China, we recommend using high-quality, locally sourced laminates to reduce shipping costs and time. For high-performance, mid-Tg laminates, we generally prefer Shengyi S1000-H (Tg 150) laminates. This laminate brand is of similar quality to Isola FR406 (Tg 150), one of the standard North American laminates. FR406 may offer slightly better efficiency in terms of Dk and Df, although clients are welcome to negotiate price and lead time to find a more suitable option.
|S1141||FR406||S 1000-H||FR406||S1000-2||FR406||IT1 80A||370HR|
|Td (TGA @ 5% weight loss )||N/A||300||N/A||300||N/A||300||350||340|
|Dk (50% resin @ 2 GHz)||4.2||3.93||4.38||3.93||4.28||3.93||4.3||4.04|
|Df (50% resin @ 2 GHz) RoHS||0.015||0.0167||0.015||0.0167||0.017||0.0167||0.015||0.21|
If the specific material required for PCB production, such as Rogers, Teflon, Isola, YENYO, Taconic, Panasonic, or Ceramic, is not in stock, we can still obtain it for our clients. However, there may be a slight delay in delivering the laminate. Alternatively, clients can choose to provide the materials themselves, and only the manufacturing costs will be charged.
If clients have any questions or need clarification regarding the materials used in PCB production, they are encouraged to contact our team. We are always available to provide support and assist with any inquiries clients may have.
Our priority is to provide our clients with high-quality PCBs that meet their unique requirements and specifications. We are committed to ensuring that our clients have access to a wide range of materials for their PCB production process. Contact us today for more information or to discuss any questions you may have.
Comparison of 8 Layer PCBs With other Types of PCBs
8 layer PCBs offer some unique advantages over other types of PCBs, but they also have some disadvantages. Here’s a comparison of 8 layer PCBs with other common types of PCBs:
● Single-layer PCB: Single-layer PCBs are the simplest and cheapest option, but they have limited routing options, signal integrity issues, and are not suitable for complex circuits.
● Double-layer PCB: Double-layer PCBs offer more routing options but can suffer from signal integrity issues with high-frequency signals or high-density designs.
● Four-layer PCB: Four-layer PCBs can accommodate more complex circuits and better signal integrity performance than double-layer PCBs, but are less flexible and less efficient than 8 layer PCBs.
● 10+ layer PCB: PCBs with more than 10 layers provide even greater functionality, but require more expensive materials, advanced manufacturing techniques, and additional design considerations.
● Flex PCB: Flex PCBs offer greater flexibility and can be bent and shaped to fit specific applications or assemblies. They can have fewer layers but may have specific flexure requirements that add complexity and cost.
● Rigid-flex PCB: Rigid-flex PCBs combine the benefits of rigid PCBs in terms of durability and strength with the flexibility of a flex PCB. They can have 3 or more layers and may be more expensive than 8 layer PCBs.
Prototype Multilayer 8 layer Printed Circuit Boards Prices and Delivery Time
At JarnisTech, we offer rapid, low-cost, high-quality PCB prototyping services. We are committed to adhering to ISO9001 quality management systems and have an in-house quality control department that ensures all of our work meets rigorous standards.
Our prototyping services can deliver your PCB within 3-7 days, depending on your specific requirements. This is a marked improvement over the standard service time of 6-12 days commonly offered by other providers.
Our team of experts is dedicated to providing our clients with the highest level of service quality, speed, and accuracy. We utilize state-of-the-art prototyping technologies and techniques to ensure that our clients’ PCBs meet their specifications and requirements.
Our rapid PCB prototyping services offer exceptional value, with a focus on affordability and delivery speed. For clients seeking dependable, cost-effective, and timely PCB prototyping solutions, JarnisTech is the ideal partner. Please contact our team today to learn more about our services and to discuss your specific requirements.
Future Outlook for 8 Layer PCB Technology
● The use of 8 layer PCBs is expected to grow in various industries, including telecommunications, consumer electronics, aerospace, and medical devices.
● As the demand for higher circuit density and faster data transfer rates increases, the use of more layers in PCB design will become more common.
● Future developments in 8 layer PCB technology may involve the use of advanced materials, such as high-speed laminates and embedded passive components, as well as more sophisticated design tools and simulation software.
● The challenge for PCB designers and manufacturers will be to balance the benefits of multilayer PCBs with the costs and complexity of fabrication and testing.
Therefore, 8 layer PCBs are a crucial technology enabling the development of more advanced and complex electronic devices, and they will continue to play a significant role in the electronics industry in the years to come.
8 layer PCBs offer several advantages that suit demanding applications in electronics, including high-density designs, improved signal integrity, efficient thermal management, and miniaturization of devices. The use of additional layers in multilayer PCBs allows for more complex and high-performance circuitry, answering the growing demand for lighter, faster, smaller, and more powerful electronics.
While the cost of manufacturing and designing 8 layer PCBs is higher compared to lower layer counts, it remains a reasonable price for high-end design applications. The ongoing trends in IoT, Industry 4.0, telecommunication, and automation will continue to demand sophisticated electronic systems that can handle more complex data, faster communication, and power requirements than before, pushing the PCB industry to innovate and optimize their production processes.
At JarnisTech, we are a team of seasoned professionals who specialize in the manufacture of 8-layer PCBs. With years of experience in the industry, we possess the necessary expertise to create top-notch 8-layer PCBs that satisfy our clients’ requirements.
We are committed to delivering top-quality products on-time, every time, as we understand the value of timely delivery for our clients. Our commitment to excellence is reflected in every order we fulfill, and our clients can expect nothing short of the highest standards from us.
Visit us to learn more about our services and to begin your next printed circuit board project. Our experienced team is always ready to assist you and ensure that your experience with us is a positive one. We look forward to serving you and building a lasting relationship.