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Jarnistech > HDI PCB > 6+N+6 HDI PCB

The advent of High-Density Interconnect (HDI) PCB technology has brought about a paradigm shift in the electronics industry, enabling the realization of smaller form factors and significantly increased circuit density. Among the various HDI configurations available, the 6+N+6 HDI PCB configuration emerges as an exceptional solution catering to the demands of highly sophisticated applications. Featuring a stack-up of 6 signal layers, N buried or blind via layers, and an additional 6 signal layers, this particular configuration strikes an ideal balance between complexity and functionality.

This article aims to delve into the challenges encountered when working with 6+N+6 HDI PCBs and explore the innovative solutions that render them an irresistible choice for cutting-edge electronic designs.

What is 6+N+6?

In the context of HDI PCB design, “6+N+6” refers to the layer configuration of a high-density interconnect (HDI) printed circuit board. It represents the arrangement of signal layers, power and ground layers, and additional signal layers within the PCB stackup.

Here’s what each component of “6+N+6” represents:

●The first “6” signifies the six signal layers. These layers are dedicated to carrying the electrical signals between different components and circuitry on the PCB.

●The “N” represents the multiple power and ground layers. The actual number of power and ground layers can vary depending on the specific design requirements. These layers are responsible for providing stable power distribution and ensuring proper grounding throughout the PCB.

●The second “6” indicates the additional signal layers. These are extra signal layers beyond the initial six signal layers. The additional signal layers provide more routing options and flexibility for complex circuit designs.

Overall, the “6+N+6” configuration in HDI PCBs offers a balanced combination of signal layers, power and ground layers, and additional signal layers. This arrangement enables higher circuit density, improved signal integrity, and enhanced functionality within a compact PCB design.

Key Features and Benefits 6+N+6 HDI PCB

6+N+6 HDI PCBs (High-Density Interconnect PCBs) have several key features and benefits that make them suitable for advanced electronic applications. Here are some of the key features and benefits:

High Density:

6+N+6 refers to the layer stackup of the PCB, where there are six signal layers, N number of inner layers (usually power and ground planes), and six more signal layers. This layer configuration allows for a high density of interconnections, making it suitable for complex and miniaturized electronic designs.

Increased Routing Capability:

The multiple signal layers in a 6+N+6 HDI PCB provide ample routing space, enabling the design of intricate and high-speed circuits. The additional inner layers can be utilized for power and ground planes, which helps in reducing noise and improving signal integrity.


HDI PCBs are known for their ability to accommodate miniaturized components and designs. With a high-density layer stackup, 6+N+6 HDI PCBs allow for the integration of smaller components and finer pitch devices, leading to more compact and lightweight electronic products.

Enhanced Signal Integrity:

The use of additional power and ground planes in HDI PCBs helps in reducing electromagnetic interference (EMI) and crosstalk, resulting in improved signal integrity. This is particularly important for high-frequency and high-speed applications.

Improved Electrical Performance:

HDI PCBs, including 6+N+6 configurations, often utilize advanced materials with excellent electrical properties. These materials offer low dielectric loss, controlled impedance, and high-frequency performance, making them suitable for high-speed and high-frequency applications.

Increased Reliability:

The multilayer structure and advanced manufacturing techniques used in HDI PCBs enhance their reliability. The reduced size and shorter signal paths minimize the chances of signal degradation and improve overall system performance.

Design Flexibility:

HDI PCBs offer greater design flexibility compared to traditional PCBs. The increased routing capability, smaller vias, and finer trace widths allow for more complex and innovative designs, enabling engineers to optimize the performance of their electronic systems.

Applications of 6+N+6 HDI PCBs

6+N+6 HDI PCBs (High-Density Interconnect PCBs) find applications in various industries and electronic devices that require high-density interconnections, miniaturization, and advanced electrical performance. Here are some common applications of 6+N+6 HDI PCBs:

Mobile Devices:

HDI PCBs are widely used in smartphones, tablets, and other mobile devices. The compact size and high-density interconnections of 6+N+6 HDI PCBs allow for the integration of multiple functionalities and miniaturized components, enabling thinner and lighter mobile devices.

High-Speed Data Communication Systems:

With their enhanced signal integrity and routing capabilities, 6+N+6 HDI PCBs are suitable for high-speed data communication systems such as network switches, routers, and servers. These PCBs can handle the high-frequency signals and provide reliable performance in data-intensive applications.

Aerospace and Defense Electronics:

The aerospace and defense industries often require PCBs with high reliability, miniaturization, and advanced electrical performance. 6+N+6 HDI PCBs can be found in avionics systems, radar systems, communication equipment, and other defense electronics, where space is limited, and high performance is crucial.

Automotive Electronics:

The automotive industry utilizes HDI PCBs for various applications, including advanced driver-assistance systems (ADAS), infotainment systems, engine control units (ECUs), and sensors. The small form factor and high-density interconnections of 6+N+6 HDI PCBs are beneficial for automotive electronics, where space optimization is important.

Medical Devices:

Medical devices often require compact and reliable PCB solutions. 6+N+6 HDI PCBs are used in medical imaging equipment, patient monitoring systems, implantable devices, and other medical electronics. The high-density interconnections and miniaturization capabilities of HDI PCBs contribute to the development of smaller and more portable medical devices.

Industrial Electronics:

Industrial applications such as automation systems, robotics, and control systems benefit from the high-density interconnects and advanced electrical performance of 6+N+6 HDI PCBs. These PCBs enable the integration of complex circuitry in industrial equipment, improving efficiency and reliability.

Test and Measurement Equipment:

Test and measurement devices require high-speed and high-precision PCBs for accurate measurements and data processing. 6+N+6 HDI PCBs are suitable for applications like oscilloscopes, spectrum analyzers, network analyzers, and other test and measurement equipment.

Design a 6+N+6 HDI PCB Steps

Designing a 6+N+6 HDI PCB involves several steps to ensure a successful layout that meets the desired specifications. Here are the general steps involved in designing a 6+N+6 HDI PCB:

1. Requirements Analysis: Understand the project requirements, including the functionality, performance, size constraints, and electrical specifications of the PCB.

2. Schematic Design: Create a schematic diagram of the circuit, ensuring proper connections, component selection, and signal integrity considerations.

3. Component Placement: Place the components on the PCB layout software, considering factors such as signal flow, thermal management, and mechanical constraints. Optimize component placement for signal routing and minimize trace lengths.

4. Layer Stackup: Define the layer stackup based on the design requirements and available manufacturing capabilities. Determine the number and arrangement of signal layers, power and ground planes, and additional signal layers (N) for the HDI section.

5. Routing: Route the signal traces and power/ground connections. Pay attention to signal integrity, controlled impedance, differential pair routing, and high-speed signal requirements. Use microvias and blind vias for interconnections within the HDI section.

6. Power and Ground Planes: Create power and ground planes to ensure proper power distribution and return paths. Consider the placement of decoupling capacitors to minimize noise and voltage fluctuations.

7. Signal Integrity Analysis: Perform signal integrity analysis, including checking for impedance mismatches, crosstalk, and signal reflections. Use simulation tools to validate the design and make necessary adjustments.

8. Design Rule Check (DRC): Run a DRC to ensure compliance with manufacturing and assembly guidelines, including clearances, minimum trace widths, and annular ring sizes.

9. Design for Manufacturability (DFM): Optimize the design for manufacturability by considering the capabilities and limitations of the chosen fabrication and assembly processes. Ensure that the design is manufacturable within the desired cost and timeline.

10. Gerber File Generation: Generate the Gerber files, which are the industry-standard format for PCB fabrication. Include all necessary layers, solder mask, silkscreen, and drill files.

11. Prototype and Testing: Fabricate a prototype of the PCB and perform thorough testing to validate its functionality and performance. Identify any issues or areas for improvement.

12. Iterative Refinement: Based on the results of testing and feedback, refine the design if necessary, addressing any identified issues or optimizations.

It is important to note that designing a 6+N+6 HDI PCB requires expertise in high-density design techniques, knowledge of advanced fabrication processes, and familiarity with the chosen PCB layout software. Working closely with experienced PCB designers and manufacturers can greatly help in ensuring a successful design.

Manufacturing a 6+N+6 HDI Printed Circuit Boards Steps

Manufacturing a 6+N+6 HDI (High-Density Interconnect) printed circuit board involves several steps. Here is a general outline of the process:

1. Design: Create a detailed PCB design using computer-aided design (CAD) software. Consider the layer stackup, component placement, routing, and signal integrity.

2. Material Selection: Choose the appropriate materials for your PCB, including the substrate, copper foils, and prepregs. For HDI boards, specialized materials with thin dielectrics and high-density interconnect features may be required.

3. Preprocessing: Clean and prepare the base materials, such as the substrate and copper foils, to ensure good adhesion during lamination.

4. Layer Stackup: Assemble the layers according to the design requirements. In the case of a 6+N+6 HDI board, this typically involves stacking multiple inner layers with high-density interconnects between them.

5. Drilling: Precisely drill the required holes for vias, through-holes, and component mounting. HDI boards often include microvias, blind vias, and buried vias to achieve high-density interconnects.

6. Electroless Copper Deposition: Apply a thin layer of electroless copper to the drilled holes and exposed copper surfaces to create conductive pathways.

7. Imaging: Transfer the PCB design onto the outer layers using a process called photolithography. This involves applying a photosensitive resist, exposing it to UV light through a photomask, and developing it to create the circuit pattern.

8. Plating: Electroplate the exposed copper surfaces with additional copper to increase the trace thickness and ensure good conductivity.

9. Lamination: Use heat and pressure to bond the layers together, including the inner layers and outer copper foils. This step helps create a solid multilayer structure.

10. Etching: Remove the excess copper from the outer layers using an etching process. This leaves behind the desired copper traces and pads.

11. Soldermask Application: Apply a soldermask to protect the copper traces and define the soldering areas. This helps prevent short circuits and provides insulation.

12. Surface Finish: Apply a surface finish to protect the exposed copper surfaces and facilitate soldering. Common surface finishes include HASL (Hot Air Solder Leveling), ENIG (Electroless Nickel Immersion Gold), and OSP (Organic Solderability Preservative).

13. Silkscreen Printing: Add component designators, logos, and other markings to the PCB using a silkscreen printing process. This helps with component placement and identification.

14. Testing: Perform electrical testing to ensure the integrity of the circuit connections, including continuity, impedance, and signal quality.

15. Inspection: Inspect the assembled PCB for any defects, such as soldering issues, component misalignment, or shorts.

16. Final Testing: Conduct functional testing to verify the performance of the completed PCB.

17. Packaging: Package the finished PCBs appropriately for transportation and delivery.

It’s important to note that the specific steps and processes may vary depending on the manufacturer, equipment used, and the complexity of the HDI board design. Working with an experienced PCB manufacturer is recommended to ensure the successful production of your 6+N+6 HDI printed circuit boards.

Challenges and Solutions in 6+N+6 HDI PCBs

The 6+N+6 HDI PCB technology presents certain challenges during design and manufacturing due to its higher layer count and complexity. Here are some common challenges and their corresponding solutions:

Signal Integrity:

With increasing circuit density, signal integrity becomes crucial. Challenges such as signal crosstalk, impedance control, and power integrity can arise. Solutions include careful placement and routing of high-speed signal traces, the use of proper ground and power planes, controlled impedance routing, and simulation techniques to analyze and optimize signal integrity.

Vias and Layer Stacking:

The presence of buried and blind vias in the 6+N+6 HDI stack-up adds complexity to the manufacturing process. Challenges can include achieving reliable and precise via drilling, alignment, and plating. Solutions involve using advanced PCB fabrication techniques, such as laser drilling and precise registration systems, to ensure accurate placement and alignment of vias.

Thermal Management:

Higher circuit density can lead to increased heat generation, which poses challenges for thermal management. Solutions include careful placement of heat-generating components, use of thermal vias and conductive pads for heat dissipation, and incorporation of thermal relief structures and heatsinks where necessary.

Manufacturing Complexity:

The increased number of layers, vias, and smaller features in 6+N+6 HDI PCBs can make the manufacturing process more complex. Challenges include precise layer alignment, registration, and lamination. Solutions involve leveraging advanced manufacturing technologies like laser direct imaging (LDI) for precise layer alignment, automated optical inspection (AOI) systems for quality assurance, and strict process control to ensure consistent fabrication quality.

Cost Considerations:

The complexity and higher layer count of 6+N+6 HDI PCBs can result in increased manufacturing costs compared to traditional PCB technologies. Solutions include optimizing the design for cost efficiency by minimizing unnecessary layers and vias, utilizing standard materials and processes where possible, and working closely with PCB manufacturers to identify cost-saving opportunities without compromising functionality.

Design for Manufacturability (DFM):

The complex nature of 6+N+6 HDI PCBs requires careful consideration of DFM principles to ensure manufacturability and yield. Solutions involve close collaboration between designers and manufacturers, early DFM analysis and feedback, adherence to design rules and guidelines provided by the manufacturer, and iterative design improvements based on manufacturing feedback.

6+N+6 HDI Comparison with Other HDI PCB Technologies

When comparing the 6+N+6 HDI PCB technology with other HDI PCB technologies, it’s important to consider factors such as layer count, signal integrity, manufacturing complexity, and cost. Here’s a comparison with some other common HDI PCB technologies:

4+N+4 HDI: This type of HDI PCB has 4 signal layers, N buried or blind via layers, and another 4 signal layers. It offers moderate circuit density and is relatively simpler to manufacture compared to 6+N+6 HDI. It is often used in applications where moderate density and cost-effectiveness are important.

8+N+8 HDI: This type of HDI PCB has 8 signal layers, N buried or blind via layers, and another 8 signal layers. It provides higher circuit density compared to 6+N+6 HDI and is suitable for more complex designs with tighter space constraints. However, it also increases the manufacturing complexity and cost.

Microvia Technology: Microvia technology is a type of HDI PCB technology that uses microvias, which are smaller in diameter compared to traditional plated-through vias. This allows for increased routing density and finer trace/space requirements. Microvias can be stacked to achieve multiple layers, and the number of layers can vary depending on the specific design requirements. Microvia technology can be used in conjunction with the 6+N+6 or other HDI configurations to further enhance circuit density.

Sequential Build-Up (SBU) Technology: SBU technology involves building up the HDI PCB in multiple sequential steps, adding layers and vias as needed. It allows for higher layer counts and complex interconnect structures. The number of layers and vias can be customized based on the design requirements, making it a versatile option for achieving high circuit density.

Therefore, the choice of HDI PCB technology depends on the specific design requirements, including circuit density, cost considerations, and manufacturing complexity. The 6+N+6 HDI configuration offers a balance between density and complexity, while other configurations like 4+N+4, 8+N+8, microvia technology, and SBU technology provide alternatives for different design needs.

Final Thoughts

In conclusion, the realm of high-density interconnect technology has been forever altered by the advent of 6+N+6 HDI PCBs, which effectively address the challenges associated with circuit density and complexity. Meticulous attention to signal integrity, layer stacking, thermal management, manufacturing intricacies, cost considerations, and design for manufacturability has paved the way for these advanced PCBs to deliver exceptional performance in modern electronic devices. The ability of 6+N+6 HDI PCBs to meet the demands of intricate designs while upholding reliability and efficiency renders them an exceedingly attractive choice across industries such as telecommunications, automotive, consumer electronics, and beyond.

As technology continues to evolve, the continued prominence of 6+N+6 HDI PCBs is all but guaranteed, shaping the future of electronics by enabling the development of smaller, more intelligent, and immensely powerful devices.

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