6-layer HDI PCB

Description

6-layer 1st order immersion gold HDI PCB is a high-density interconnect (HDI) printed circuit board that employs ENIG (Electroless Nickel/Immersion Gold) surface treatment technology and uses a combination of micro-blind vias and micro-vias for high-density interconnection between multiple layers. This board consists of six layers, with “1st-order” indicating the use of micro-blind vias and micro-vias to optimize the wiring density and reduce signal interference in the transmission.
ENIG (Electroless Nickel/Immersion Gold) is a widely used surface treatment method that forms a nickel-gold alloy layer on the PCB surface through electroless nickel plating and immersion gold processes. This layer enhances the reliability, solderability, and corrosion resistance of the PCB. ENIG-treated HDI PCBs offer superior electrical performance, high-frequency capability, and reliability, making them ideal for applications that require high speed, high frequency, and high integration.
This article provides a detailed introduction to the structure, design principles, manufacturing process, advantages of ENIG surface treatment, and major applications of 6-layer 1st order immersion gold HDI PCB.
1. Basic Concept of 6-layer 1st Order Immersion Gold HDI PCB
A 6-layer 1st order immersion gold HDI PCB consists of six layers of circuits, including signal layers, power layers, and ground layers. The term “1st-order” refers to the use of a combination of micro-blind vias (which connect part of the layers) and micro-vias (which go through all the layers), enabling precise and high-density interconnections between different layers.
ENIG is a surface treatment process that uses electroless nickel plating followed by immersion gold plating. The gold layer offers superior soldering properties, corrosion resistance, and electrical performance. The ENIG process is particularly suited for high-frequency circuits where fine pitch and stable signal transmission are critical.
Differences Between HDI and Traditional PCB
Compared to traditional PCBs, HDI technology allows the use of finer traces and smaller hole diameters, resulting in higher density and integration on the same footprint. Key differences include:
Higher Line Density: HDI PCBs use micro-blind vias and micro-vias to pack more circuits and components into a smaller area, meeting the demand for compact, high-functionality devices.
Lower Signal Attenuation: The short and efficient signal paths achieved by using micro-blind vias and micro-vias reduce signal loss and improve transmission stability.
Better EMI Performance: With optimized power and ground layers, HDI boards effectively reduce electromagnetic interference (EMI), making them more suitable for high-speed, high-frequency applications.
2. Structure of 6-layer 1st Order Immersion Gold HDI PCB
The structure of a 6-layer 1st order immersion gold HDI PCB includes six primary layers, each with a specific function:
Top Signal Layer: Located at the top of the PCB, it is used for high-frequency signals and key power/ground connections. Careful design is crucial to reduce interference in this layer.
Inner Layer 1: The first inner signal layer, interconnected with the top signal layer via micro-blind vias or micro-vias. This layer is used for signal routing.
Inner Layer 2: The second inner signal layer, positioned between the power and ground layers. It helps to further route signals and provide additional interconnections.
Power Layer: Dedicated to distributing power to various components on the PCB. The power layer helps stabilize the voltage supply for the entire circuit.
Ground Layer: Provides a common reference ground for the entire PCB. This layer reduces noise and EMI and ensures signal integrity, especially for high-speed signals.
Bottom Signal Layer: The bottom signal layer mirrors the top signal layer and is responsible for signal routing on the bottom side of the PCB.
The 1st-order HDI design uses micro-blind vias and micro-vias to connect the different layers, optimizing the layout and achieving higher circuit density and more precise signal routing.
3. Manufacturing Process of 6-layer 1st Order Immersion Gold HDI PCB
The manufacturing process of a 6-layer 1st order immersion gold HDI PCB involves multiple steps to ensure high density, precision, and reliability. Key steps include material selection, lamination, drilling, surface treatment, copper plating, etching, and surface treatment.
Material Selection: HDI PCBs are typically made from high-performance substrates such as FR4 or PTFE (Teflon), which offer good electrical performance and thermal stability, meeting the demands for high-speed, high-frequency signal transmission.
Lamination: Multiple layers are laminated together under high temperature and pressure, ensuring strong bonding between the layers and stable electrical performance.
Drilling and Hole Processing: Laser or mechanical drilling is used to create micro-vias and micro-blind vias, which are critical for layer-to-layer interconnections.
Copper Plating and ENIG Treatment: Copper is plated into the vias to ensure electrical connectivity. The ENIG process is then applied to the PCB surface, forming a layer of nickel and gold. This enhances the solderability and corrosion resistance of the board.
Chemical Etching: Excess copper is etched away, leaving only the necessary circuit traces.
Surface Treatment: In addition to ENIG, surface treatments like HASL (Hot Air Solder Leveling) or OSP (Organic Solderability Preservative) may be applied to further improve the solderability and reliability of the PCB.
4. Advantages of ENIG Surface Treatment
ENIG surface treatment offers several advantages, particularly for high-speed and high-frequency applications:
Superior Solderability: The smooth and even gold layer provides excellent soldering performance, reducing defects such as cold solder joints or solder bridges.
Corrosion Resistance: The gold layer protects the PCB from oxidation, ensuring a longer lifespan and reliable performance in harsh environments.
Stable Electrical Performance: ENIG-treated surfaces exhibit low contact resistance, which ensures stable signal transmission, especially in high-frequency circuits.
Enhanced Reliability: The nickel-gold layer improves the PCB’s resistance to mechanical stress and environmental factors, increasing the reliability of the circuit over time.
5. Advantages of 6-layer 1st Order Immersion Gold HDI PCB
A 6-layer 1st order immersion gold HDI PCB combines the benefits of HDI technology and ENIG surface treatment, making it an excellent choice for a wide range of demanding applications. Its advantages include:
High Circuit Density: By utilizing micro-blind vias and micro-vias, these PCBs allow more components and circuits to be packed into a smaller area, increasing functionality without increasing the size of the PCB.
Improved Electrical Performance: With the use of ENIG, signal transmission is stable, and the signal loss is minimized, making this board ideal for high-speed and high-frequency applications.
Compact Design: HDI PCB are perfect for space-constrained applications, such as mobile devices, wearable technology, and automotive electronics.
High Reliability: ENIG surface treatment provides excellent resistance to corrosion and oxidation, ensuring long-term stability even in harsh environments.
Better EMI Performance: The combination of optimized power and ground layers helps reduce electromagnetic interference, improving signal integrity and reducing noise in high-frequency circuits.
6. Applications of 6-layer 1st Order Immersion Gold HDI PCB
The 6-layer 1st order immersion gold HDI PCB is widely used in various fields that require high-performance and reliable circuit boards. Some of its key applications include:
Telecommunications: ENIG HDI PCB are commonly used in devices such as smartphones, 5G base stations, Wi-Fi routers, and other communication equipment. With the advent of 5G technology, the demand for HDI PCB has surged.
Consumer Electronics: Devices such as smartwatches, wireless earbuds, tablets, and other consumer gadgets rely on HDI PCBs to meet their high-performance and compact size requirements.
Automotive Electronics: In the automotive industry, especially in autonomous vehicles and electric vehicles, these PCBs are used in control units, radar sensors, and infotainment systems.
Medical Devices: Medical equipment such as portable monitors, ultrasound systems, and diagnostic devices require the high signal integrity and reliability offered by HDI PCBs.
Computer Hardware: HDI PCB are used in computer motherboards, graphics cards, and storage devices where high-density, fast signal processing, and minimal signal loss are crucial.
With their high density, speed, integration, and reliability, 6-layer 1st order immersion gold HDI PCBs have become an indispensable component in many advanced electronic products. As technology continues to evolve, particularly in 5G, IoT, and autonomous driving, the demand for these PCBs is expected to grow across various industries, including telecommunications, consumer electronics, automotive, medical devices, and more. The ongoing development of HDI technology will continue to push the boundaries of what is possible, enabling the next generation of high-performance, compact, and reliable electronic devices.