by Kerstin
November 1, 2022
PCB knowledge
(0)
05 mins

Answers to all your questions regarding HDI PCB

Are you considering making all your circuit boards lightweight and for your company to use? Or have you been trying to increase the electrical efficiency of circuits?

If yes, you should integrate the HDI PCB for better integrity. But, there are chances that you may get confused about the material, benefits, types, and advantages of HDI PCBs.

The following guide is all about helping you understand the detailed background. So, let’s start reading without wasting time.

What is HDI PCB?

An HDI PCB refers to High-Density Interconnector Printed Board Circuit. It is known for having higher wiring density per unit area.

These high-density interconnector printed board circuits provide finer spaces and lines. So, the availability of minor vias and capture pads in the circuits is apparent.

These factors significantly contribute to the increased/higher connection pad density in HDI PCB. If you’re looking for a high-layer count and expensive laminated boards, HDI PCBs are the best choice.

However, the overall board of an HDI PCB comes with a large number of demanding properties. It includes high-frequency transmission capacity and greater impedance control.

It is the miniaturization of the electronic part arrays that makes the increased density of the board.

What is HDI material?

Common HDI material is RCC (resin-coated copper). However, three major RCC types are used in producing HDI PCBs.

They are polyimide metalized film, pure polyimide film, and cast polyimide film. The primary reason behind this material in constructing HDI PCBs is its lightweight and fantastic flexibility.

All these types of RCC are mounted on the board with the help of SMT (Surface Mount Technology), CSP (Chip Scale Package), and mechanical drilling.

That is why increased durability with fine inner spaces in HDI PCBs is ensured.

What is HDI PCB stackup?

As stated earlier, HDI PCB is related to using buried, blind, and micro vias to make the integrated boards more compact. However, the HDI PCB stack contains a list of components/parts. Some of these components are:

Microvias

Compared to normal vias, Microvias are defined as small or mostly laser-drilled vias integrated into the board with a ratio of 1:1. These are connected with the external layer to a single inner layer. They don’t penetrate the entire board when connecting with internal and outer layers.

Buried vias

They are used to connect single or more inner layers. It is done without any connection to the outer layer of the circuit board.

ELIC

It includes the use of stacked copper-filled Microvias in the circuit. It is connected to multiple layers of the PCB.

Lamination process and different types of HDI PCB stack-ups

Read the following section for the lamination process of HDI PCBs:

The lamination of HDI PCB is a very intricate process. It involves inserting dielectric between two different layers of copper and already present/laminated sub-composite.

It is a sequential lamination for building up on the PCB by stacking up layers of dielectric material and copper.

All these layers are built on the sub-composites. However, this isn’t a typical process. Almost all industries use sequential lamination to reduce the challenges during the process.

Some essential practices you need to consider during the lamination of HDI PCB include:
●Decreasing the layer count;
●Lowering the weight of copper in layers;
●Selecting a high-profile glass transition temperature material;
●Considering resin material for making the copper surface.

Some different types of HDI PCB stackups are given as under:
●Standard lamination with vas or plated through holes;
●Sequential lamination with plated through, blind, and buried vias;
●Lamination buildup, including microvias.

What are the differences between HDI and standard PCBs?

Some common differences between HDI and standard PCBs are given as under:

●HDI PCBs are made up of high-quality gum copper foil, whereas standard PCBs are made up of FR4 material;
●Materials in HDI PCBs are integrated through laser drilling, but in standard PCBs, materials are joined together with electronic-grade glass-pressed cloth;
●HDI PCBs are known for providing better integrity as compared to standard PCBs;
●HDI PCBs also have higher layer density as compared to standard PCBs;
●The density of HDI PCBs is more significant than standard PCB.

What are the benefits of HDI PCBs?

Some demanded benefits of HDI PCBs are given as under:

●Helps users to attach/ incorporate a large number of components on a circuit board;
●It is populated on both sides of the board;
●It decreases the usage of power in circuits;
●Supports extended battery life;
●Easily integrated into other types of battery-powered devices;
●They are excellent and robust, so the durability of HDI PCBs is impressive;
●It decreases thermal degradation, which in turn increases the durability of the device.

What are the applications of HDI PCB?

Typical applications of HDI PCB are described below:

●Mobile/cell phones
●All types of touchscreen devices
●Laptops
●Computers
●Digital cameras
●4/5G network devices
●Communication devices
●Applications used in military
●Smart monitors
●Avionics

Design and manufacturing processes of HDI PCB

Some basics that you must consider while designing an HDI PCB are given as under:

●Make sure to trace the width with spacing limits.
●Ensure the right ratio between annular rings and the aspect of the board.
●The overall material of the PCB must be available with a controlled impedance.
●Check the impedance profiles before designing the PCB stackup.

When you’re done designing the HDI PCB, follow the following types for manufacturing it:

●Estimate the layer count that you want to integrate into the board.
●You can do this by using a big BGA component on the board or by using the best interface + direction.
●Check up on the fabrication house to get a rough idea about the type of materials you need to integrate.
●Now observe the dielectric data of the material.
●When you’re done checking the dielectric, try to pick a style based on the layer count and thickness of the board.
●This style will route the signals to the inner layers of the board.
●Now, it’s time to perform a reliability assessment. It is necessary to evaluate the proper functioning of the HDI PCB.

Conclusion

We understand the complexity of designing and manufacturing HDI PCB. But, in the above guide, we have explained anything in detail. For more information and the right assistance, you can visit IBE PCB & PCBA.

Our experts are always ready to help you. Also, you will have the opportunity to get the best HDI PCB.