HDI PCB

By utilizing advanced production technology and strict quality control system, we ensure that every piece of HDI PCB meets the actual needs of customers. We always adhere to the customer-oriented principle and provide the best service to customers.

HDI (Partial Technology Capability)
N/M/N	4～28L(6 Steps)
Interconnection of any layer	16L
Finished board thickness	200um～3200um
Copper Foil Type	VLP. SLP. SLP2
Min laser via/pad(um)	70/140um
Min buried via diameter/pad(um)	100/230um
Min PTH diameter/pad(um)	100/230um
Min trace/spacing(um）	35/35um
Min solder mask openging(um)	90um
Solder mask color
Surface Finish	HASL/ImmersionTin/ImmersionSilver /ImmersionGold/ENEPIG/OSP
Test	ICT, FCT, AOI, Flying probe test

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product details

HDI PCB: The Core Carrier of Electronic Circuits Under High-Density Interconnection

As electronic devices evolve rapidly towards miniaturization, thinness, and high integration, traditional printed circuit boards (PCBs) can no longer meet the high-density interconnection requirements brought by the surge in chip pin counts and the improvement of signal transmission rates. Against this backdrop, HDI PCB (High-Density Interconnect Printed Circuit Board), with its fine circuit layout, tiny hole diameters and spacing, and excellent signal performance, has become a key core component in high-end electronic fields such as smartphones, tablets, IoT devices, and medical electronics, driving technological innovation and product upgrading in the electronics industry.

1. Basic Concept and Structural Characteristics of HDI PCB

HDI PCB, or High-Density Interconnect Printed Circuit Board, is an advanced type of PCB that uses micro blind via and buried via technologies to achieve high-density electrical connections between circuit board layers. Its core definition lies in "high density" — by reducing line width and spacing, decreasing hole diameter, and increasing the number of layers, it enables more component mounting and higher-density circuit interconnection within a limited PCB area. According to IPC (Association Connecting Electronics Industries) standards, HDI PCBs typically meet key indicators such as line width/spacing ≤ 0.1mm and blind/buried via diameter ≤ 0.15mm.

The structure of HDI PCB is more complex than that of traditional PCB, and its typical structure includes:

Micro Blind Hole: A hole that only connects two adjacent layers and does not penetrate the entire circuit board, with a diameter usually between 0.1-0.15mm. This type of hole can effectively save PCB surface space, reduce parasitic parameters in the signal transmission path, and improve signal integrity.
Buried Hole: Hidden inside the circuit board, connecting two or more non-surface layers of circuits, which also does not occupy surface space and further improves the flexibility and density of circuit layout.
Fine Circuit Layer: The line width and spacing can reach 0.05-0.1mm or even thinner, which can accommodate more signal lines and component pads.
Stacked Structure: Common stacking methods include 1+N+1, 2+N+2, etc. (the numbers before and after "+" represent the number of outer HDI layers, and N represents the number of inner ordinary circuit layers), and multi-layer high-density interconnection is achieved through multiple build-up processes.

2. Core Manufacturing Processes of HDI PCB

The manufacturing process of HDI PCB is more precise and complex than that of traditional PCB, and the key processes include:

Laser Drilling Technology

Laser drilling is one of the core processes in HDI PCB manufacturing, used to make micro blind holes and buried holes. Common laser types include carbon dioxide (CO₂) lasers and ultraviolet (UV) lasers. CO₂ lasers are suitable for drilling resin and glass fiber substrates, with a hole diameter usually between 0.1-0.15mm; UV lasers can achieve smaller hole diameters (0.05-0.1mm) with higher drilling quality, suitable for high-precision HDI products. Laser drilling has the advantages of high efficiency, small hole diameter, and precise positioning, which can meet the high-density distribution requirements of micro blind holes.

Build-Up Process

The build-up process is the key to realizing the multi-layer structure of HDI PCB. First, the inner core board is made, then insulating layers and copper foils are sequentially stacked on both sides of the core board, and interlayer connections are realized through laser drilling and copper electroplating. Repeating this process can form a multi-layer HDI structure. According to the number of build-up layers, it can be divided into single-stage build-up, two-stage build-up, or even multi-stage build-up HDI PCBs. The more build-up layers, the higher the interconnection density.

Copper Electroplating Process

Copper electroplating is used to form a conductive layer on the inner walls of micro blind holes and buried holes to realize interlayer electrical connections. HDI PCB has extremely high requirements for the uniformity and density of electroplated copper. Advanced electroplating processes (such as pulse electroplating) need to be adopted to ensure uniform thickness of the copper layer in the holes, avoid defects such as voids and pinholes, and ensure connection reliability.

Fine Circuit Fabrication Process

Fine circuits are fabricated through processes such as photolithography and etching, with line width and spacing controllable below 0.05mm. To ensure the precision and integrity of the circuits, high-resolution photoresist, high-precision exposure equipment, and optimized etching parameters need to be used to reduce circuit deformation and side etching.

3. Core Advantages of HDI PCB

Compared with traditional PCBs, HDI PCBs exhibit significant advantages in various aspects due to their unique structure and processes:

High-Density Interconnection, Reducing PCB Volume

Through micro blind holes, buried holes, and fine circuit technology, HDI PCBs can realize more component mounting and circuit connections per unit area. For example, the area of a smartphone motherboard using HDI PCB can be reduced by 30%-50% compared with traditional PCB, which is crucial for mobile devices pursuing thinness and lightness.

Improving Signal Integrity, Reducing Electromagnetic Interference

Micro blind holes and buried holes shorten the signal transmission path, reducing signal delay and crosstalk; at the same time, the fine circuit layout can optimize the signal direction and reduce electromagnetic radiation (EMI). This enables HDI PCBs to meet the strict requirements for signal performance in scenarios such as 5G communication and high-speed data transmission.

Enhancing Heat Dissipation Performance, Improving Equipment Reliability

The multi-layer structure and optimized layout of HDI PCB can distribute heat dissipation paths more reasonably, quickly conducting the heat generated by high-power components to the heat dissipation area. In addition, some HDI PCBs can be combined with metal substrates or thermally conductive materials to further improve heat dissipation capacity and extend the service life of electronic equipment.

Simplifying Assembly Process, Reducing Production Cost

The high-density characteristic of HDI PCB allows components to be laid out more centrally, reducing the length and number of wires as well as the number of solder joints during the assembly process. At the same time, its thin and light feature also simplifies the overall assembly process of electronic equipment, indirectly reducing the production cost of the equipment.

4. Main Types and Application Scenarios of HDI PCB

According to the number of build-up layers and structural complexity, HDI PCBs can be divided into different types, suitable for different application scenarios:

Single-Stage HDI PCB

Adopting a single build-up process, the structure is usually 1+N+1, suitable for products with medium and low-density interconnection requirements, such as tablets, routers, digital cameras, etc. These products have certain requirements for PCB volume and signal performance but do not need extreme high density.

Two-Stage HDI PCB

After two build-up processes, the structure can reach 2+N+2 or more complex, with higher interconnection density. It is suitable for products with high requirements for high density and high signal performance, such as smartphones, high-end servers, medical diagnostic equipment, etc. For example, the motherboards of mainstream smartphones mostly use two-stage HDI PCBs.

Three-Stage and Above HDI PCB

Realized through multiple build-up processes, it has a complex structure and extremely high interconnection density. It is mainly used in ultra-high-end electronic equipment, such as aerospace electronics, precision medical instruments, high-performance computing equipment, etc. These products have extreme requirements for PCB reliability, stability, and signal performance, and the manufacturing cost is relatively high.

In addition to the above scenarios, HDI PCBs are also widely used in IoT sensors, automotive electronics (such as autonomous driving systems, in-vehicle entertainment systems), industrial control equipment and other fields, becoming key basic components driving the technological development of these fields.

5. Development Trends of HDI PCB

With the continuous progress of electronic technology, HDI PCB is developing rapidly in the following directions:

Higher Density: The line width and spacing develop below 0.03mm, and the hole diameter is reduced to below 0.05mm. Higher interconnection density is achieved through more precise processes to meet the development needs of chip packaging technologies (such as SiP, CoWoS).
Multi-Layering and Integration: The number of layers continues to increase, and at the same time, passive components (such as resistors, capacitors) are embedded into the PCB to realize the integrated integration of "PCB + components", further reducing the volume and improving the integration level.
Material Upgrade: High-frequency and high-speed substrates with low dielectric constant (Dk) and low loss factor (Df), such as high-speed FR-4 and polyimide (PI), are adopted to meet the higher requirements for signal performance in 5G, 6G communication and high-speed data transmission.
Green Manufacturing and Cost Optimization: Develop environmentally friendly manufacturing processes to reduce the use of chemical agents and waste emissions; at the same time, reduce the manufacturing cost of HDI PCB through process optimization and large-scale production, and promote its popularization in mid-to-low-end electronic equipment.
Integration with Advanced Packaging Technologies: HDI PCB is increasingly closely combined with advanced packaging technologies such as Chip Scale Packaging (CSP) and Flip Chip, forming a "packaging-PCB" collaborative design model to further improve the performance and reliability of electronic equipment.