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Jarnistech > HDI PCB > 7+N+7 HDI PCB

The demand for high-density interconnect (HDI) printed circuit boards (PCBs) has been steadily increasing in recent years. HDI technology allows for the integration of more components and circuitry in a smaller footprint, enabling the development of compact and high-performance electronic devices. One of the advanced HDI PCB designs is the 7+N+7 configuration, which offers enhanced functionality and reliability.

This article explores the design, fabrication,features and benefits of 7+N+7 HDI PCB circuit boards and their applications in various industries.

Definition of HDI PCB

HDI PCB stands for High-Density Interconnect Printed Circuit Board. It is a type of circuit board that is designed to accommodate a higher density of components and interconnections within a smaller footprint. HDI PCBs are characterized by their advanced interconnect structures, such as microvias, buried vias, and blind vias, which allow for more complex routing and increased circuit density.

Compared to traditional PCBs, HDI PCBs offer several advantages. They provide shorter signal paths, reduced parasitic capacitance and inductance, and controlled impedance characteristics, which improve signal integrity and electrical performance. HDI PCBs also enable the use of smaller components with finer pitch, allowing for higher component counts and more compact designs.

HDI PCBs are widely used in various industries, including consumer electronics, telecommunications, automotive, aerospace, and medical devices. They are particularly suitable for applications that require miniaturization, high-speed signal transmission, and increased functionality within limited space.

Overall, HDI PCBs are an essential technology for achieving higher circuit density, improved signal integrity, and enhanced design flexibility in modern electronic devices.

Understanding 7+N+7 HDI PCBs

7+N+7 HDI PCBs are a specific type of high-density interconnect (HDI) technology that offers even higher circuit density and design flexibility compared to traditional HDI PCBs. Let’s break down the components of the term:

1. The “7” represents the number of layers in the core of the PCB. These layers typically consist of signal and power planes, allowing for the routing of signals and power distribution throughout the board.

2. The “N” represents the number of stacked microvia layers. Microvias are small drilled holes that connect different layers of the PCB. Stacking microvia layers allows for increased routing density and more efficient use of space.

3. The second “7” represents the number of additional layers in the build-up layers. Build-up layers are used to create complex interconnect structures, such as blind vias and buried vias, which further enhance the circuit density and routing capabilities of the PCB.

In summary, 7+N+7 HDI PCBs consist of a core with seven layers, stacked microvia layers (represented by “N”), and an additional seven layers in the build-up layers. This configuration enables designers to achieve higher levels of integration, increased routing density, and improved signal integrity in a compact form factor.

The use of 7+N+7 HDI technology is particularly beneficial in applications that require miniaturization, high-speed signal transmission, and advanced functionality. It allows for the design of complex electronic systems with reduced footprint, improved electrical performance, and enhanced reliability.

Benefits and Applications of 7+N+7 HDI PCBs

Benefits of 7+N+7 HDI PCBs:

1. Increased Circuit Density: The stacked microvia layers and build-up layers in 7+N+7 HDI PCBs allow for a higher circuit density compared to traditional PCBs. This means more components can be integrated into a smaller space, enabling the design of compact and lightweight electronic devices.

2. Enhanced Signal Integrity: The use of microvias and advanced interconnect structures in 7+N+7 HDI PCBs helps to minimize signal degradation and improve signal integrity. This is especially important in high-speed applications where maintaining the integrity of high-frequency signals is crucial.

3. Improved Thermal Management: The compact design of 7+N+7 HDI PCBs allows for more efficient heat dissipation. The shorter signal paths and reduced layer count help to minimize thermal resistance, ensuring better thermal management and overall system reliability.

4. Design Flexibility: 7+N+7 HDI PCBs offer greater design flexibility due to the increased routing density and finer pitch capabilities. Designers can achieve intricate routing patterns, closer component placement, and more complex circuitry, enabling innovative and space-saving designs.

5. Reliability and Cost Savings: The advanced interconnect structures and optimized routing in 7+N+7 HDI PCBs result in improved reliability. The reduced layer count and smaller form factor also contribute to cost savings in terms of material usage, manufacturing complexity, and assembly time.

Applications of 7+N+7 HDI PCBs:

1. Mobile Devices: The compact size and high circuit density of 7+N+7 HDI PCBs make them ideal for mobile devices such as smartphones, tablets, and wearable devices. These PCBs enable the integration of multiple functions and features in a small form factor.

2. High-Speed Data Communication: 7+N+7 HDI PCBs are well-suited for applications that require high-speed data transmission, such as network switches, routers, and data center equipment. The improved signal integrity and reduced signal distortion help ensure reliable and high-performance data communication.

3. Aerospace and Defense: The miniaturization and high reliability of 7+N+7 HDI PCBs make them suitable for aerospace and defense applications. These PCBs can be used in avionics systems, radar systems, communication systems, and other electronic components in aircraft and military equipment.

4. Medical Devices: Medical devices often require compact and reliable PCB solutions. 7+N+7 HDI PCBs can be utilized in various medical devices, including implantable devices, diagnostic equipment, monitoring devices, and medical imaging systems.

5. Automotive Electronics: The automotive industry is increasingly incorporating advanced electronics for safety, infotainment, and autonomous driving systems. 7+N+7 HDI PCBs can be used in automotive applications where space is limited, and high reliability and signal integrity are essential.

How to Design and Manufacturing a 7+N+7 HDI Printed Circuit Boards?

Designing and manufacturing a 7+N+7 HDI (High-Density Interconnect) PCB involves several steps and considerations. Here is an overview of the process:

1.Requirements Gathering:

Begin by understanding the project requirements, including the system specifications, electrical performance requirements, size constraints, and any specific design guidelines or standards to follow.

2.Schematic Design:

Create a schematic diagram of the circuit, including the placement of components, signal paths, and connections. Ensure proper signal integrity considerations, such as impedance matching and controlled impedance requirements.

3.PCB Layout Design:

Use a PCB design software tool to create the layout of the PCB. Start by defining the layer stackup, including the number and arrangement of signal, power, and ground layers. Place components, considering factors like signal paths, thermal management, and manufacturability. Utilize design rules and guidelines for trace width, spacing, and impedance control.

4.Microvia Planning:

Determine the microvia structure required for the design. Consider the aspect ratio, pad size, annular ring, and via pitch. Ensure that the microvia design meets the signal integrity requirements and can be manufactured reliably.


Optimize the routing paths to accommodate the high-density interconnections. Use the available routing resources efficiently, considering signal integrity, power distribution, and thermal management. Follow design rules for trace width, spacing, and impedance control.

6.Power and Ground Planes:

Allocate sufficient space for power and ground planes, ensuring low impedance paths for power distribution. Implement proper decoupling capacitors and ground stitching vias for noise reduction and power integrity.

7.Design Verification:

Perform design rule checks (DRC) and electrical rule checks (ERC) to ensure that the design meets the specified guidelines and requirements. Use simulation and analysis tools to verify signal integrity, thermal performance, and power distribution.

8.Design for Manufacturability (DFM):

Collaborate with your PCB manufacturer to ensure that the design is manufacturable. Address any manufacturing constraints or limitations early in the design process. Consider panelization, solder mask requirements, and other manufacturing considerations.

9.Design for Testability (DFT):

Incorporate test points, access points, and other features that aid in testing and troubleshooting. Ensure that the design is testable and can be efficiently tested during manufacturing.

10.Gerber File Generation:

Generate the necessary Gerber files, which contain the manufacturing information for the PCB fabrication process. These files include the PCB layers, solder mask, silkscreen, and drill files.

11.PCB Manufacturing:

Send the Gerber files to a reliable PCB manufacturer. Choose a manufacturer with experience in producing high-density PCBs and who can meet your specific requirements. Work closely with the manufacturer to address any manufacturing-related questions or concerns.

12.Assembly and Testing:

Once the PCBs are manufactured, they can be assembled with the required components. Collaborate with an experienced assembly partner who can handle the high-density assembly and perform necessary testing and inspection to ensure quality.

How to Selection PCB Laminates for 7+N+7 HDI PCB Stackups?

Selecting the right PCB laminates for a 7+N+7 HDI (High-Density Interconnect) PCB stackup is crucial for achieving optimal electrical performance and reliability. Here are some factors to consider when selecting laminates for your stackup:

1.Dielectric Material:

Choose a dielectric material with suitable electrical properties for high-frequency applications. The dielectric constant (Dk) and dissipation factor (Df) are important parameters to consider. Lower Dk values are generally preferred for high-speed designs to minimize signal loss and maintain signal integrity. Additionally, a low Df value helps reduce signal attenuation and maintain good signal quality.


Determine the appropriate laminate thickness based on your design requirements. Thinner laminates allow for tighter trace spacing and smaller vias, enabling higher circuit density. However, thinner laminates may have higher signal losses and may require additional considerations for power distribution and thermal management.

3.Copper Foil:

Consider the type and thickness of the copper foil used in the laminate. Thicker copper foils provide better current-carrying capacity and can help manage heat dissipation. Choose the appropriate copper weight based on your power requirements and thermal considerations.

4.Glass Transition Temperature (Tg):

Tg is the temperature at which the laminate material transitions from a glassy state to a rubbery state. Select a laminate with a Tg that exceeds the expected operating temperature of your PCB to ensure dimensional stability and reliability.

5.Thermal Conductivity:

For designs with high power dissipation or thermal management requirements, consider laminates with higher thermal conductivity. These laminates can help efficiently transfer heat away from critical components and improve overall thermal performance.

6.Material Supplier and Quality:

Choose a reputable laminate supplier known for producing high-quality materials. Consider factors such as material consistency, reliability, and availability. It’s important to ensure that the laminate materials meet industry standards and have the necessary certifications.

7.Compatibility with Fabrication Processes:

Verify that the selected laminates are compatible with the fabrication processes required for your design. Consider factors such as drillability, etchability, and adhesion properties to ensure smooth manufacturing and good quality control.

8.Cost Considerations:

Evaluate the cost of the selected laminates and consider your budgetary constraints. Balancing performance requirements with cost-effectiveness is important, but it’s crucial not to compromise on quality and reliability.

It is recommended to consult with your PCB manufacturer or laminate supplier for specific recommendations based on your design requirements. They can provide valuable insights and assist you in selecting the most suitable laminates for your 7+N+7 HDI PCB stackup. Additionally, they can provide information on material data sheets, electrical properties, and any specific design guidelines for the chosen laminates.

What is the Standard 7+N+7 HDI PCB Board Thickness?

The standard thickness for a 7+N+7 HDI PCB board can vary depending on the specific design requirements and application. However, there is no universally defined standard thickness for this type of PCB stackup. The thickness will depend on factors such as the number of layers, the type of materials used, the desired electrical performance, and any specific mechanical constraints.

In general, HDI PCBs are known for their high circuit density and compactness, which often leads to thinner PCBs. The overall thickness of a 7+N+7 HDI PCB stackup typically ranges from 0.6mm to 1.6mm (24mil to 63mil), but it can go beyond this range depending on the specific design needs.

It’s important to consider the electrical and mechanical requirements of your design when determining the appropriate thickness. Factors such as impedance control, thermal management, structural integrity, and assembly considerations will influence the selection of the PCB thickness.

When designing a 7+N+7 HDI PCB, it is recommended to work closely with your PCB manufacturer or a qualified PCB designer. They can provide guidance and help determine the optimal thickness based on your specific design requirements, taking into account the capabilities and limitations of the manufacturing processes and materials available.

Future Prospects and Challenges in 7+N+7 HDI PCBs

7+N+7 HDI PCBs (High-Density Interconnect PCBs) refer to printed circuit boards with multiple layers of high-density interconnects, typically consisting of microvias, buried vias, and blind vias. These PCBs offer increased routing density, reduced size, and improved signal integrity, making them suitable for various advanced electronic applications. When considering the future prospects and challenges of 7+N+7 HDI PCBs, several factors come into play:

Miniaturization and Increased Functionality:

The demand for smaller and more feature-rich electronic devices continues to grow. 7+N+7 HDI PCBs enable designers to pack more functionality into a smaller footprint, making them ideal for applications such as smartphones, wearables, IoT devices, and medical equipment.

High-Speed and High-Frequency Applications:

With the increasing need for high-speed data transmission and high-frequency signal processing, 7+N+7 HDI PCBs provide the necessary interconnect density and controlled impedance characteristics. They are suitable for applications like telecommunications, data centers, high-speed computing, and wireless communication systems.

Advanced Packaging Technologies:

7+N+7 HDI PCBs are often used in advanced packaging technologies like flip-chip, chip-on-board (COB), and system-in-package (SiP). These technologies enable the integration of multiple components and subsystems into a single package, enhancing performance, reducing size, and improving reliability.

Manufacturing Challenges:

As the complexity of 7+N+7 HDI PCBs increases, manufacturing challenges arise. The fabrication processes for microvias, buried vias, and blind vias require precise control and alignment. Achieving high yield and reliability in manufacturing can be a challenge, especially when dealing with smaller feature sizes and higher layer counts.

Signal Integrity and Power Integrity:

With the higher density of interconnects, signal integrity and power integrity become critical considerations. Proper design techniques, such as controlled impedance routing, decoupling capacitors, and power plane distribution, are essential to maintain signal integrity and prevent noise interference.

Cost and Time-to-Market:

The advanced technologies and manufacturing processes involved in 7+N+7 HDI PCBs can lead to higher production costs. Additionally, the complexity of design and manufacturing may increase the development time, affecting the time-to-market for new products.

Materials and Reliability:

Selecting suitable materials with appropriate dielectric properties, thermal characteristics, and reliability is crucial for 7+N+7 HDI PCBs. Ensuring the long-term reliability of these PCBs under various operating conditions is a challenge that requires careful material selection and testing.

Despite these challenges, the future prospects for 7+N+7 HDI PCBs are promising. As the demand for smaller, faster, and more powerful electronic devices continues to rise, the need for advanced PCB technologies like 7+N+7 HDI will grow. Advances in manufacturing processes, materials, and design techniques will help address the challenges and enable the widespread adoption of these PCBs in various industries.


7+N+7 HDI PCB circuit boards have emerged as a key technology in the field of electronic design and manufacturing. Their ability to accommodate complex and high-density circuitry, coupled with improved signal integrity and reliability, makes them ideal for a wide range of applications. From consumer electronics to automotive, aerospace, and defense industries, the demand for compact and high-performance devices is driving the adoption of 7+N+7 HDI PCBs. As technology continues to advance, we can expect further innovations and advancements in HDI PCB designs, enabling the development of even more sophisticated electronic devices in the future.

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