What is HDI PCB and HDI PCB Applications

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An electronics product has many parts. Among them, the printed circuit board, more often known as PCB, is critical to the product's functionality. As with any other product that requires assembly, PCB is often the central part of electronic devices, yet it is just a flat layer with components mounted on it.

Like everything, PCBs have developed new technology in the past few years, using different materials. High density interconnects (HDI) is a unique material concept that has been showing up as a printed circuit board option in the industry for a couple of years now. While traditionally, the PCB media goes by FR4/glass-resin-based materials, HDI is the densification of microvia technology and brings an opportunity for engineers to rethink the simple aspects of their boards they sometimes overlook when dealing with more costly printed circuit board technologies.

It is not an exaggeration to say that HDI PCB technology is revolutionizing the manufacturing world for many industries. If you are not yet aware of HDI PCB and its potential, this guide will familiarize you with what HDI PCB technology is all about.

Introduction to HDI PCB

HDI stands for high-density interconnect. It is a multi-layer printed circuit board developed to provide better performance than traditional FR-4 boards or glass epoxy boards. The process uses thin copper foil layers and multiple metallization levels to create a multi-layer circuit board with plated-through holes. These holes allow the copper foil layers to be connected without the need for wires or vias, reducing the required space on the board and allowing for more components to be placed on a single board.

It is a printed circuit board designed to allow for extremely dense signal routing, usually in the form of multiple layers. This makes HDI PCBs ideal for applications such as microprocessors, graphics cards, and other electronics where many signals need to be routed quickly and efficiently.

Advantages of HDI PCB

Flex PCBs have many advantages over conventional PCBs, making them desirable in many applications. The main benefits are:

High Reliability

Copper pillars improve reliability by reducing the impedance mismatch between different metals used in the board stack-up due to their different thermal expansion coefficients. In addition, HDI boards are less sensitive to environmental factors such as humidity and temperature compared with conventional printed circuit boards due to their increased mechanical robustness.

High Density Interconnects

Using copper pillars allows high density interconnects to be achieved without increasing the number of layers on the board. This provides more flexibility in routing signals from one side of the board to another without using costly plated through-holes or blind microvias. The presence of copper pillars also helps reduce crosstalk between signals routed on different layers by providing an additional electrical connection point at each layer interface.

Smaller Size

High Density Interconnects are made by placing components closer together than traditional circuit boards; this reduces the overall size of the board while maintaining the same performance level as conventional circuit boards.

Reduced Weight

A reduction in overall build volume allows for thinner boards without compromising performance or reliability. This also reduces the amount of material used during production, which results in lower material costs and less waste disposal costs.

Lower Capacitance and Inductance

The interconnects have lower capacitance and inductance than traditional PCBs, which helps to improve signal integrity, reduce noise and increase bandwidth. This translates into better circuit performance and higher reliability.

Higher Performance

HDI boards provide better thermal dissipation and signal integrity than conventional PCBs. The higher density allows for smaller components and thinner layers while maintaining the desired impedance characteristics. This leads to improved performance over traditional PCBs in digital and analog circuits, particularly concerning noise immunity and signal integrity.

Highly Customizable

The ability to customize not only the size and thickness of an HDI circuit but also its shape means that more complex designs can be built into smaller packages. This is especially useful for wireless devices such as smartphones and tablets, where space is at a premium.

Lower Cost

Since HDI PCBs require fewer layers of copper per square inch than traditional boards, they cost less to produce. Additionally, since they do not require expensive through-hole components, they cost less to manufacture than conventional boards.

HDI PCB Applications

HDI printed circuit boards are commonly used in the industrial and military sectors. This is since they are manufactured using high-quality materials, making them suitable for use in harsh environments. Here are some of the HDI PCB applications:

Military Applications

Military applications include aviation equipment, tanks, and missiles. The harsh weather conditions of many military bases can cause damage to electronic components if they are not installed in HDI PCBs. The components on an HDI printed circuit board have a higher resistance to shock and vibration than those installed on conventional PCBs. Therefore, they make up a significant portion of the military's aircraft electronics system.

Aircraft Applications

HDI printed circuit boards are used extensively in aircraft manufacturing industries due to their durability and resistance to electromagnetic interference (EMI) from other components in an aircraft system, such as radar systems and transponders. In addition, these boards can withstand strong vibrations caused by turbulence during flight without affecting their performance or functionality.

Power Supplies

The main reason HDI PCBs are used in power supplies is their high reliability, making them ideal for equipment such as motors or transformers. This is especially true when they are used in applications with a lot of heat generated by the components on the board.

Auxiliary Systems

In addition to being used in power supplies, HDI printed circuit boards are also used in auxiliary systems such as pumps and compressors. This is because they have higher resistance to vibrations compared to conventional PCBs. This makes them ideal for use in applications with large amounts of vibration generated by moving parts such as motors and gears.

Medical Applications

HDI printed circuit boards are also widely used in medical devices such as pacemakers, defibrillators, and other life-saving medical devices. In fact, these devices often require extremely high levels of reliability and durability, which is why HDI PCBs are so popular here.

Industrial Control Systems

Another common application for HDI printed circuit boards is industrial control systems. These systems consist of various components such as sensors, actuators, and controllers working together to efficiently control machines or processes. The advantage of using HDI PCBs over traditional ones is that they offer increased reliability, resulting in lower maintenance costs over time.

HDI PCB Crucial Design Considerations

The main design considerations for an HDI PCB are:

  • Materials for HDI PCBs include FR4 glass-reinforced epoxy laminate, polyimide film, and epoxy laminates. The choice depends on the application. For example, if a part requires high reliability and has a long life expectancy, then FR4 is usually preferred because it can withstand heat better than polyimide films.
  • The electrical performance of the HDI design should be analyzed carefully to ensure that signal integrity is not compromised by excessive impedance or reflections caused by discontinuities in the ground plane or other layers.
  • Power planes must be placed as close as possible and connected with microvias near each through-hole. This helps reduce noise from switching transients caused by current flowing through different areas of the power plane at different times in each cycle of operation.
  • Since HDI boards have fewer layers, there is less routing space available for signals than conventional layers. This means you will need to be extra careful about optimizing your design for routing efficiency before sending it off for fabrication. Any mistakes at this stage could lead to costly rework and delays in getting your product out the door.
  • Due to the increased surface area of an HDI PCB, it has a higher chance of emitting electromagnetic interference (EMI). To reduce this risk, designers can use shielded wires or plates at critical circuit board points.
  • Thermal management is critical in HDI designs because heat cannot be dissipated through the substrate as easily as it can with a conventional method. This means thicker layers and more copper should be used within the board stack-up when possible.

Key Takeaway

With the increased use of PCBs in electronics manufacturing, HDI boards are now being used more and more. The use of HDI boards is currently low but is expected to grow. It is great to see that both big and small manufacturers are adopting this technology to satisfy the needs of their customers. Many people now have taken an interest in learning more about the components and design guidelines regarding HDI PCB. This can be very familiar, especially for those experienced with wiring and how it functions.

To know more about this, you must check Hemeixin's Microvia HDI PCBs section, which discusses it. We hope this guide was helpful and gave you new insights into what HDI PCB is and what value it can add to your next project.

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