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Jarnistech > HDI PCB > 2+N+2 HDI PCB

HDI (High-Density Interconnect) PCBs have become increasingly popular in the electronics industry due to their ability to accommodate complex designs with high component density. Among the various HDI PCB configurations, the 2+N+2 structure stands out as a versatile and efficient option. In this article, we will explore the key features, advantages, application, design and manufacturing of 2+N+2 HDI PCBs, highlighting their significance in modern electronic applications.

HDI PCB 2+N+2: Moderate Complex HDI

HDI PCB 2+n+2 is classified as a Type III construction, which employs resin-filled holes, vias, and plated microvias for interconnection purposes. This type follows a sequential buildup denoted as X+n+X.

In the case of a 2+n+2 buildup, a minimum of two, and potentially more, high-density interconnection layers are incorporated on at least one side of the substrate core during the HDI PCB design phase. The substrate core itself can comprise multiple layers and incorporates buried vias to facilitate interconnection. The manufacturing process adheres to established PCB guidelines, and the choice between a flexible or rigid substrate depends on the specific requirements of the intended application.

Microvias play a crucial role in this design, as they can be stacked or staggered across different layers. This arrangement enables seamless signal transmission between the layers through these microvias. Due to the small drill diameters and aspect ratio requirements of the vias, the manufacturing process involves a sequential lamination approach. However, the utilization of stacked microvias technology allows designers to effectively route fine-pitch components using buried or blind vias.

Challenging designs that incorporate copper-filled stacked microvias are commonly implemented in applications demanding high-level signal transmission performance. The HDI PCB 2+n+2 design offers notable advantages in appliances that require increased routing density while maintaining a thin finished thickness of the printed circuit board.

Furthermore, HDI PCB 2+n+2 designs are highly suitable for Ball Grid Arrays (BGAs) due to their ability to accommodate high I/O counts and smaller ball pitch. Consequently, there has been a substantial surge in demand for such designs in the manufacturing of game consoles, cameras, and cell phones.

It is important to note that while the commonly adopted design model for an X+n+X buildup is 2+n+2, structures can extend beyond higher numbers depending on the mechanical and electrical requirements of a given appliance.

Design Considerations for 2+N+2 HDI PCB

When designing a 2+N+2 HDI (High-Density Interconnect) PCB, there are several important considerations to keep in mind. Here are some key design considerations:

Layer Stackup:

The layer stackup is crucial in HDI PCB design. It determines the routing density, impedance control, and signal integrity. The stackup should be carefully planned to accommodate the required number of signal layers, power planes, and ground planes while ensuring controlled impedance for high-speed signals.

Routing and Signal Integrity:

HDI PCBs are often used for high-speed and high-frequency applications. Proper routing techniques, such as controlled impedance routing, differential pairs, and length matching, should be employed to maintain signal integrity and minimize signal degradation.

Via Types and Placement:

HDI PCBs utilize various via types, including microvias, buried vias, and blind vias, to achieve high routing density. Microvias are small in diameter and provide a high level of density. Careful placement of vias is important to optimize signal paths and minimize crosstalk and interference.

Power and Ground Planes:

Adequate power and ground planes are essential for HDI PCBs to provide stable power distribution and minimize noise. The power and ground planes should be properly connected using vias and stitched together to ensure low impedance paths.

Component Placement:

Component placement plays a crucial role in HDI PCB design. Placing high-speed components close to each other and minimizing trace lengths can help reduce signal propagation delays and improve signal integrity. Proper thermal management should also be considered to ensure components operate within their temperature limits.

Manufacturing Constraints:

HDI PCBs often involve advanced manufacturing techniques, such as laser drilling and sequential lamination. It’s important to consider the manufacturing capabilities and constraints of your chosen PCB manufacturer to ensure the design can be successfully fabricated.

Design for Testability:

Implementing test points and access for test probes is important for efficient testing and debugging of HDI PCBs. Designing in test pads and vias for boundary scan testing or other test methodologies can help streamline the manufacturing and testing process.

Thermal Management:

HDI PCBs with high component density may generate significant heat. Proper thermal management techniques, such as thermal vias, heat sinks, and thermal pads, should be employed to dissipate heat effectively and prevent overheating of components.

These are some of the key considerations when designing a 2+N+2 HDI PCB. It’s important to work closely with experienced PCB designers and manufacturers to ensure your design meets the required performance and reliability standards.

Manufacturing Process of 2+N+2 HDI PCB

The manufacturing process of a 2+N+2 HDI (High-Density Interconnect) PCB involves several steps that are specific to the complexity and density of the design. Here is a general overview of the manufacturing process:

Design and Layout:

The PCB design is created using PCB design software, taking into consideration the specific requirements of the 2+N+2 HDI design, including layer stackup, routing, and component placement. The design is then converted into Gerber files or other manufacturing file formats.

Material Selection:

The choice of materials is crucial for HDI PCBs. High-performance materials with excellent electrical properties, such as specialized laminates and prepregs, are selected to meet the design requirements. The choice of materials also depends on factors like impedance control, signal integrity, and thermal management.

Layer Stackup and Prepreg Preparation:

The layer stackup is determined based on the design requirements, including the number of signal layers, power planes, and ground planes. The prepregs (resin-impregnated fiberglass sheets) are prepared by cutting them to the required size and applying copper foil to both sides.


HDI PCBs use microvias, buried vias, and blind vias to achieve high routing density. The drilling process involves using laser drilling machines to create small-diameter holes for the vias. Laser drilling provides high precision and allows for smaller via sizes.

Electroless Copper Deposition:

After drilling, the PCB panels undergo an electroless copper deposition process. This involves depositing a thin layer of copper on the walls of the drilled holes, including the microvias, to create conductive pathways.

Imaging and Plating:

The PCB panels are coated with a photosensitive material called a photoresist. The Gerber files are used to create a photomask, which is then used to expose the panels to UV light. The exposed areas of the photoresist are hardened, while the unexposed areas remain soft. The panels are then chemically treated to remove the soft areas, leaving behind the pattern for the inner layers. Copper is plated onto the exposed areas to form the conductive traces.

Lamination and Pressing:

The inner layers are stacked together with the prepregs and copper foil layers, forming a multilayer structure. The stack is then pressed and heated in a lamination press to bond the layers together, forming a solid panel.

Outer Layer Imaging and Plating:

The outer layers of the panel are coated with photoresist, exposed to UV light using the appropriate photomasks, and chemically treated to remove the unexposed areas. The exposed copper areas are then plated to create the outer layer conductive traces.

Solder Mask Application:

A solder mask layer is applied to the entire surface of the PCB, except for the areas where components will be soldered. The solder mask protects the PCB from environmental factors and prevents solder bridging during assembly.

Surface Finish:

The PCB’s exposed copper surfaces are typically plated with a surface finish to protect them from oxidation and facilitate soldering. Common surface finishes include HASL (Hot Air Solder Leveling), ENIG (Electroless Nickel Immersion Gold), and OSP (Organic Solderability Preservatives).

Routing and Vias:

The PCB panels are routed to separate individual boards, and vias are drilled and plated to provide electrical connections between different layers.

Testing and Inspection:

The finished HDI PCBs undergo various testing and inspection processes to ensure they meet the required quality standards. This includes electrical testing, visual inspection, and sometimes automated optical inspection (AOI) or X-ray inspection for more complex designs.

Industries Benefiting from 2+N+2 HDI PCB

The 2+N+2 HDI PCB technology has gained significant traction across various industries, enabling advancements and providing numerous benefits. Some of the industries that greatly benefit from the implementation of 2+N+2 HDI PCBs include:

Aerospace and Defense:

The aerospace and defense industry demands high-performance, reliable, and compact electronic systems. 2+N+2 HDI PCBs are well-suited for applications such as avionics, radar systems, satellite communication, and military-grade equipment. The increased routing density and improved signal transmission capabilities of 2+N+2 HDI PCBs make them ideal for meeting the stringent requirements of this industry.


The telecommunications industry relies on high-speed and high-bandwidth communication systems. 2+N+2 HDI PCBs enable the design and manufacturing of advanced networking equipment, routers, switches, and telecommunications infrastructure components. Their ability to accommodate fine-pitch components and ensure efficient signal transmission makes them vital for meeting the demands of modern communication networks.

Consumer Electronics:

The consumer electronics industry thrives on compact and feature-rich devices such as smartphones, tablets, wearables, and portable gadgets. 2+N+2 HDI PCBs allow for thin and lightweight designs, enabling manufacturers to create sleek and powerful electronic devices. The increased routing density and design flexibility offered by 2+N+2 HDI PCBs are crucial in meeting the miniaturization requirements of consumer electronics.

Medical Devices:

The medical industry requires high-performance and reliable electronic systems for various applications, including diagnostic equipment, patient monitoring devices, implantable devices, and imaging systems. 2+N+2 HDI PCBs facilitate the integration of complex circuitry and miniaturized components, enabling the development of advanced medical devices with enhanced functionality and precision.


The automotive industry relies on electronics for various applications, including advanced driver assistance systems (ADAS), infotainment systems, engine management, and vehicle connectivity. 2+N+2 HDI PCBs play a vital role in enabling the compact and reliable integration of electronics in vehicles, ensuring efficient signal transmission and robust performance in demanding automotive environments.

Industrial and Manufacturing:

Industries such as industrial automation, robotics, and manufacturing equipment benefit from 2+N+2 HDI PCBs’ ability to handle complex control systems and high-speed data processing. These PCBs enable the creation of compact and reliable electronic solutions that optimize manufacturing processes and enhance automation capabilities.

These industries represent a fraction of the sectors that benefit from the implementation of 2+N+2 HDI PCB technology. As electronic systems continue to evolve and demand higher performance, the significance of 2+N+2 HDI PCBs will only continue to grow across a wide range of applications and industries.

Significance of 2+N+2 HDI PCB Buildup

The 2+N+2 HDI PCB buildup holds significant importance in the realm of printed circuit board technology. Its significance stems from several key factors:

Increased Routing Density:

The 2+N+2 HDI PCB structure allows for a higher routing density compared to traditional PCB designs. By incorporating multiple high-density interconnection layers on at least one side of the substrate core, it enables more efficient routing of signals and power, accommodating complex circuitry and miniaturized components.

Improved Signal Transmission:

With the utilization of stacked and staggered microvias technology, the 2+N+2 HDI PCB facilitates unhindered signal transmission between different layers. This ensures reliable and efficient communication between components, especially in high-speed applications where signal integrity is crucial.

Enhanced Design Flexibility:

The 2+N+2 HDI PCB offers greater flexibility in design due to the availability of multiple interconnection layers. Designers can optimize the placement and routing of components, leading to improved functionality and performance of the overall system.

Compatibility with Fine-Pitch Components:

The stacked microvias technology in 2+N+2 HDI PCBs enables the use of buried or blind vias, allowing for the routing of fine-pitch components. This capability is particularly advantageous when working with advanced semiconductor devices, such as Ball Grid Arrays (BGAs), which have high I/O counts and smaller ball pitch.

Thin Profile and Space Savings:

The 2+N+2 HDI PCB structure allows for the creation of thinner and more compact circuit boards. This is especially beneficial in applications where space is limited, such as portable electronic devices. The reduced thickness and smaller form factor contribute to lightweight and sleek designs.

Application Versatility:

The 2+N+2 HDI PCB buildup finds extensive application across various industries. It is particularly well-suited for aerospace, military, telecommunications, consumer electronics, and other sectors that demand high-performance and miniaturized electronic solutions.

By harnessing the advantages offered by the 2+N+2 HDI PCB buildup, manufacturers can achieve superior functionality, reliability, and miniaturization in their products. This type of PCB structure empowers the development of advanced electronic systems that meet the ever-increasing demands of modern technology.

How to Choose the Right HDI PCB 2+N+2 Manufacturer?

When choosing the right HDI (High-Density Interconnect) PCB 2+N+2 manufacturer, there are several factors to consider. Here are some important considerations:

Experience and Expertise: Look for a manufacturer with a proven track record in producing HDI PCBs. They should have experience with complex designs and advanced manufacturing techniques.

Technology and Capabilities: Ensure that the manufacturer has the necessary technology and capabilities to meet your specific requirements. This includes their ability to handle high layer counts, fine line and space requirements, microvias, and other advanced features.

Quality and Reliability: Check the manufacturer’s quality control processes and certifications. Look for adherence to industry standards such as IPC (Institute for Printed Circuits) and ISO (International Organization for Standardization). Ask for their quality control procedures, inspection methods, and reliability testing processes.

Manufacturing Facilities: Visit or inquire about the manufacturer’s facilities. Assess their production capabilities, equipment, and cleanliness. A well-equipped facility with modern machinery can ensure better quality and efficiency.

Prototyping and Production Capabilities: Determine if the manufacturer can handle both prototyping and high-volume production. It’s beneficial to work with a company that can support your project from initial design to final production.

Communication and Support: Evaluate the manufacturer’s communication channels and responsiveness. It’s important to have clear and open lines of communication to address any concerns or changes throughout the manufacturing process.

Cost and Lead Time: Consider the manufacturer’s pricing structure and lead times. While cost is a factor, it should not be the sole determining factor. Balancing cost with quality and reliability is crucial to ensure a successful outcome.

Customer Reviews and References: Research the manufacturer’s reputation by checking customer reviews and asking for references. This can provide valuable insights into their past performance and customer satisfaction.

By considering these factors, you can make an informed decision when choosing the right HDI PCB 2+N+2 manufacturer that aligns with your specific requirements and quality expectations.

Why Choose Us

JarnisTech Provide the Top HDI PCB 2+N+2 Manufacturing Technology

JarnisTech introduces a significant advancement in PCB technology with Our PCB 2+N+2 HDI circuit board, surpassing the capabilities of the previous 1+N+1 HDI PCB board. This cutting-edge high-speed PCB circuit board is meticulously printed and processed using Rogers RO4350B+TUC mixed pressure technology, ensuring exceptional performance.

The 2+N+2 HDI high-speed PCB circuit board, a notable addition to JarnisTech’s Type II HDI PCB board series, undergoes rigorous proofing and mass production processes. It is specifically manufactured utilizing Rogers RO4350B+TUC TU872SLK, a top-of-the-line material known for its superior quality and reliability.

This particular type of HDI high-speed PCB circuit board finds extensive application in critical industries such as aerospace and military, where stringent performance requirements are paramount. By leveraging JarnisTech’s expertise and the advanced capabilities of the 2+N+2 HDI technology, aerospace and military applications can benefit from enhanced functionality and reliability.

JarnisTech remains committed to pushing the boundaries of PCB manufacturing, delivering state-of-the-art solutions that meet the ever-evolving demands of high-speed circuitry. The 2+N+2 HDI high-speed PCB circuit board stands as a testament to their dedication to excellence and their ability to provide cutting-edge solutions for sophisticated industries.


We trust that you have gained valuable insights into the various types of HDI PCB structures, particularly the significance of the HDI PCB 2+n+2 buildup. This type of PCB has gained widespread popularity due to the utilization of stacked and staggered microvias technology, enabling enhanced routing capabilities.

Considering the inherent complexities associated with designs featuring increased wire density and layer requirements, we strongly recommend engaging the services of reputable PCB manufacturing experts such as JarnisTech.

As a prominent manufacturer of printed circuit boards, JarnisTech has established itself as a leader in the industry. We take pride in offering cost-effective solutions tailored to the electrical appliances sector, while upholding unwavering standards of quality. Our commitment to state-of-the-art PCB technology and unwavering customer satisfaction sets us apart.

We invite you to visit JarnisTech today and explore our comprehensive range of services. Our team of experts is readily available to provide personalized assistance and promptly provide you with a quote for your custom HDI PCB 2+n+2 designs. Experience the JarnisTech difference and unlock the full potential of your PCB projects.

Call us to get a free quote now