What is HDI PCB? And its Characteristics, Microvias and Advantages

Today’s advanced technology is trying to reduce product sizes like smart watches, mobile phones and portable devices. The compact design with decreased component size and pitch allows for more I/O in smaller geometries, bringing faster transmission of signal and significantly reducing signal loss and crossing delays. So HDI PCB is coming into being and widely used in medical equipment, automotive electronics, notebook computers and other digital products. In this article, i will show you an overview of HDI PCBs, hoping it will assist you in understanding the information to do with HDI printed circuit boards.

What is HDI PCB?

HDI stands for high-density interconnections. The circuit board which contains the limited workplace, uses smaller components with tight spacing and advanced trace route by using micro blind vias and buried vias called HDI PCB. The HDI PCB boards provide efficient space on boards for component placement to achieve multiple functions for electronic applications. By using advanced technology like fine lines, micro blind vias and buried vias create a compact board PCB size. 

Several Parameters for HDI PCB:

• Trace width and space: <= 0.10mm
• Smaller vias (<0.10 mm) and respected pad <0.40mm
• Blind vias and buried vias, micro vias
• High connection pad density

Main Characteristics of HDI PCBs

HDI printed circuit boards may need advanced manufacturing techniques due to the complexity of the boards which involves fine line and packing, laser drilling for micorvias and a special stack-up generation process before build. This manufacturing requires a process for LDI (Laser Direct Imaging) for accurate alignment and imaging. HDI boards have a thin dielectric material and prepag to minimize the board thickness So it is used advanced lamination techniques to bond the multiple layers.

Fine lines and spaces: As multiple functions need to be compacted in a small area, the copper traces and spacing need to be designed as small as possible. Normally the trace width and space should be less than 4mil and even as small as 2mils. 

Micovias are used: HDI PCB boards involve advanced design and routing techniques which can violate normal design rules by the advanced PCB Design software. An HDI printed circuit board contains the reduced via size called microvias and reduced trace and spacing which make the PCB fit a large number of components in smaller areas. Microvias may be through vias, blind vias or buried vias.

Sequential stack up: HDI PCBs have a sequential special stack up, complex design and high-density areas. The multiple conductor layers are connected through blind microvias and buried microvia. Using of microvias and highly dense designs makes the compact board size and reduces the component footprint. 

Different Types of Microvias in HDI PCBs

The old techniques for via formation are mechanical drilling for through holes and sequential build up process for blind and buried vias. However , the micro vias technology using laser drilling is the most popular in HDI technology.

The microvias can help to get better signal integrity, reduce the routing path and provide compact board size. You can see the HDI board structure in the below image by using the microvias. 

There are several types of microvias used in HDI printed circuit boards, such as blind vias, buried vias, staggered vias and stacked vias. 

Blind vias: A blind via connects an outer layer of the board to the inner layers and does not go through the entire board.

Buried vias: A buried via is a via between at least two inner layers, which is not visible from the outer layers.

Through-hole vias: A through-hole via is a copper-plated hole traverses the printed circuit board from top to bottom.

Staggered vias: Staggered vias connect different layers of the board but do not come in direct contact with each other.

Stacked vias: A stacked via consists of multiple vias layered directly on top of each other. 

Advantages of HDI PCBs

By making the board compact the various parameters like signal integrit and noise interferences make the boards advanced for the high frequency operations. This makes HDI printed circuit boards suitable for high-innovation electronics applications that require high-speed signal transmissions such as advanced telecommunication equipment, computing systems and high-performance electronics. Some of their main advantages are as follows:

• More complex functions
• High interconnection density
• High reliability
• Smaller board size
• Reduced weight
• Improved signal integrity
• Suitable for high innovation electronic devices
• Lower noise and crosstalk
• Cost optimization

Conclusion

Each of our products reflects Viasion’s commitment to quality and professionalism. We offer reliable, high-quality, one-stop PCB services designed to meet your exact needs. As an experienced HDI PCB manufacturer, we invite you to choose our solutions and move forward together toward exceptional HDI PCB manufacturing results.