Definition of a High-Density Interconnect (HDI) Printed Circuit Board

High-density interconnect, or HDI, circuit boards are printed circuit boards with a higher wiring density per unit area than traditional printed circuit boards. In general, HDI PCBs are defined as PCBs with one or all of the following: microvias; blind and buried vias; built-up laminations and high signal performance considerations. Printed circuit board technology has been evolving with changing technology that calls for smaller and faster products. HDI boards are more compact and have smaller vias, pads, copper traces and spaces. As a result, HDIs have denser wiring resulting in lighter weight, more compact, lower layer count PCBs. Rather than using a few PCBs in a device, one HDI board can house the functionality of the previous boards used.

PCB International and High-Density Interconnect PCBs

At PCB International, we strive to provide the best quality printed circuit boards with wide variety of design characteristics to suit all your project needs; we can supply printed circuit boards up to 36 layers, and copper weight up to 20oz. PCB International’ Instant Online Quote Engine can provide quotes for boards requiring copper weight up to 2oz, and up to 24 layers; printed circuit boards requiring copper weight of 3 - 20oz and/or layer count 25 – 36 layers require custom quoting. For HDI PCBs with blind and buried vias, custom quoting is required; you can do so by emailing your requirements and/or Gerber files to support@pcbinternational.com.

Benefits of HDI Printed Circuit Boards

The primary benefit of HDI printed circuit boards is the capability to “do more with less”; with copper-etching technology continuously refined for better precision, it became possible to combine functionalities of multiple PCBs into one HDI PCB.

Shortening the distance between devices and trace spaces, HDI PCBs allow for deployment of a large number of transistors for better performance in electronics while lowering power consumption. Signal integrity is also improved due to the shorter distance connections and lower power requirements. Other performance improvements over conventional PCBs include stable voltage rail, minimal stubs, lower RFI/EMI, and closer ground planes and distributed capacitance.

Additionally, consider using a HDI printed circuit board for the following benefits:

  • Cost-effectiveness: when properly planned out, overall costs are reduced due to the lower number of necessary layers and smaller sizes/fewer number of needed boards when compared to standard PCBs.
  • Faster time-to-market: Design efficiencies in HDI PCB production mean faster time-to-market. Because of the easy placement of components and vias and electrical performance, it takes a shorter amount of time to go through the design and testing process for HDI PCBs.
  • Better reliability: Microvias have much better reliability than typical through holes due to the use of a smaller aspect ratio; they are more dependable than through holes, granting HDIs outstanding performance with better materials and parts.
Common Usage of High-Density Interconnect Printed Circuit Boards

A HDI PCB is usually found in complex electronic devices that demand excellent performance while conserving space. Applications include mobile /cellular phones, touch-screen devices, laptop computers, digital cameras, 4/5G network communications, and military applications such as avionics and smart munitions.

Automotive and aerospace industries, where lower weight can mean more efficient operation, have been utilizing HDI PCBs at an increasing rate. Like almost everything else, cars are becoming more connected and computerized. Today’s cars have around 50 microprocessors on board that play a role in engine controls, diagnostics, safety features and other conveniences. Many advanced features such as onboard WiFi and GPS, rearview cameras and backup sensors rely on HDI PCBs. As automotive technology continues to advance, HDI tech will likely play an increasingly important role.

HDI PCBs are also prominently featured in medical devices; advanced electronic medical devices such as equipment for monitoring, imaging, surgical procedures, laboratory analysis etc., incorporate HDI boards. The high-density technology promotes improved performance and smaller, more cost-effective devices, potentially improving the accuracy of monitoring and medical testing.

Industrial automation requires abundant computerization, and IoT devices are becoming more common in manufacturing, warehousing, and other industrial settings. Many of these advanced equipment employ HDI technology. Today, businesses use electronic tools to keep track of inventory and monitor equipment performance. Increasingly, machinery includes smart sensors that collect usage data and connect to the internet to communicate with other smart devices, as well as to relay information to management and help optimize operations.

High-Density Interconnect Printed Circuit Board Structures

Depending on the design requirements, HDI Printed Circuit Boards can utilize different layering methods to achieve the desired performance.

PCB International strongly recommends sending us the Board Stackup to support@pcbinternational.com so we may confirm your desired HDI board design can be successfully manufactured.

HDI PCB (1+N+1): Simplest HDI

  • This structure of HDI PCB contains 1 “build-up” of high-density interconnection layers, suitable for BGA with lower I/O counts.
  • It has fine lines, microvia and registration technologies capable of 0.4 mm ball pitch, excellent mounting stability and reliability, and may contain copper filled via.
  • Applications: Cell phone, MP3 Player, GPS, Memory Card.

Fig.1: HDI PCB (1+N+1)

Simple HDI PCB
HDI PCB (2+N+2): Moderate Complex HDI

  • This structure of HDI PCB contains 2 or more “build-up” of high-density interconnection layers; microvias on different layers can be staggered or stacked; Copper filled stacked microvia structures are commonly seen in challenging designs that demand high level signal transmission performance.
  • These are suitable for BGA with smaller ball pitch and higher I/O counts and can be used to increase routing density in a complicated design while maintaining a thin finished board thickness.
  • Applications: Cell phone, PDA, game console, portable video recording devices.

Fig.2: HDI PCB (2+N+2)

Moderate Complex HDI PCB
ELIC (Every Layer Interconnection): Most Complex HDI

  • In this HDI PCB structure, all the layers are high-density interconnection layers which allow the conductors on any layer of the PCB to be interconnected freely with copper filled stacked microvia structures.
  • This provides a reliable interconnect solution for highly complex large pin-count devices, such as CPU and GPU chips utilized on handheld and mobile devices while producing superior electrical characteristics.
  • Applications: Cell phone, ultra-mobile PC, MP3, GPS, Memory cards, small computer devices.

Fig.3: ELIC (Every Layer Interconnection)

Every Layer Interconnection HDI PCB

Further design guidelines/recommendations for High-Density Interconnect Printed Circuit Boards are available upon request; contact PCB International at support@pcbinternational.com or your Account Representative to inquire more!

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