What is HDI in PCB?

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“The smaller, the better.” This appears to be the slogan for tech companies nowadays. As technology advances, all your hardware is getting smaller, from a PC that used to take up the whole desk, fast-forwarding to now when your entire business can now be managed on a smartphone in your hand. Similarly, other devices are also being miniaturized with the help of HDI printed circuit boards (PCB). HDI PCB is one of the fastest-growing technologies as it enables you to add more components in a smaller area.

But if you are not aware of what HDI PCBs are and how they have changed the outlook of the electronic devices being used today, read on to learn more about them.

What is HDI PCB?

HDI PCB stands for High Interconnector Density Printed Circuit Board. HDI PCBs are different from your conventional circuit boards because they have a higher wiring density per unit, which means they can pack more advanced technological components in less space with fewer layers.

How is this beneficial? Despite being small in size, HDI PCBs enhance your electrical performance by increasing speed and frequency. They are perfect for devices that are being created for portability. The HDI printed circuit boards are used in computers, mobile phones, game consoles, and other devices.

HDI PCBs are designed to incorporate capture pads, smaller vias, and higher density connections. But there are many design technicalities manufacturers face when creating an HDI PCB. Their designs have advanced features like microvia PCB, via-in-pad, buried and blind vias, etc. All of this helps in minimizing the area of the circuit board but increasing the efficiency of signal transmission.

With their growing use, HDI PCBs are also being used in electronic medical devices.

Types of HDI PCB

The variations in HDI PCBs are dependent on the arrangement of the microvias in PCB. The connection between the layers in a circuit board is created using vias. Based on this, there are six types of HDI PCBs.

Via in Pad

The via in-pad technology is used to reduce the size of PCB further and introduce higher density connections. This technology involves placing a via in the copper landing of the pad by drilling a hole inside the pad.

There are a few concerns with this method, such as leaving the via exposed, which could result in a poor joint if the solder paste wick into the barrel. To prevent this, we recommend capping the via by using conductive epoxy and covering it with a copper plate.

Via in pad improves thermal dissipation, applies a high voltage, and can be applied to fine pitch BGA (ball grid array).

Stacked Vias

A stacked via is precisely what the name suggests. Multiple vias are stacked on top of each other, thus reducing the space occupied and offering flexibility in layer connectivity. All vias are first drilled and then metalized, creating a ring at the top and bottom to provide an electrical connection.

Stacked vias offer greater flexibility in routing, although their manufacture requires more steps and greater precision.

Stacked Microvias

Before we talk about stacked microvias, let’s see what microvias are. Microvias are conductive holes that create connections between HDI layers in a 1:1 ratio. Stacked microvia PCB is used to span between multiple layers.

Simply put, Stacked microvias are stacks of buried vias or blind microvia stacked on buried microvias. Since multiple vias are being placed on top of each other and maintaining a strong connection is important, the buried microvias inside are filled with a conductive paste and plated.

Staggered Vias

Staggered vias, although complex in their manufacturing, are lower in cost. In staggered vias, the multiple PCB layers are connected but not stacked on top of each other, giving a staggered look.

Since the layers do not have the same center, they do not require precision in their design and making. They also take up more space than stacked vias.
Staggered Mircovias

Another type of HDI PCB is staggered microvias. It is a set of microvias formed on 2 or 3 different layers and do not share the same center, resulting in the pad diameter being greater or tangential.

Skipped Microvias

Skipped microvias go through multiple PCB layers and create a connection between the top and bottom microvia PCB. A skipped via can connect through multiple layers and can be a blind, buried, or overlapping via.

Advantages of HDI PCB

There is a reason HDI PCB manufacturing demand has increased in the last few years. Take a look at the benefits HDI PCB offers:

• It reduces the circuit board size and increases the number of components that can be placed on both sides of a raw PCB.
• The smaller size aids in increasing signal transmission and decreasing signal loss and delay.
• The micro via and via-in-pad technology helps in placing components close to each other and improving efficiency and signal quality.
• The decreased size does not affect the quality and reduces inductance interference and capacitance effects.
• Provides faster routing, high speed, and better frequency.
• You can put all functions in one circuit board rather than using multiple boards for a single device.

Final Words

The HDI PCB technology is growing steadily and is already being implemented in various industries, such as healthcare, consumer devices, aircraft, and defense applications. An HDI PCB is great for companies that do not have the equipment to implement advanced features in their day-to-day work. The minimum space of the board, along with the advanced features, makes it possible for companies to increase their performance and efficiency without investing a lot of money.

At Hemexinpcb, you can get all types of PCBs, such as Rigid PCBs, Rigid-Flex, etc. Their experts design, manufacture, assemble, and deliver them right at your doorstep.

If you are looking to implement high-density interconnector PCBs in your business, contact Hemexinpcb for consultation or send specifications for a HDI PCB quote.


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