HDI PCB -The Ultimate Guide on How To Achieve A Perfect HDI

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HDI PCBs are so popular and in-demand nowadays because they follow the current technology trend of miniaturizing devices and electronic gadgets without compromising on efficiency and performance. HDI PCBs are different from traditional PCBs and can be used for high pin count and finer pitch devices. That’s why its design and manufacturing process is complex but cost-effective as less material and fewer layers are used.

If you are designing an HDI PCB for your project, check out the complete guide below and create the perfect HDI PCB.


What Is HDI PCB?


Before we move on to the fabrication process, let’s discuss what HDI PCBs are. A high-density interconnector is a type of PCB that packs more components on a smaller circuit board without affecting the performance.

The reduced layers and signal length increases the signal integrity and makes it perfect for almost all electronic gadgets such as smartphones, automobiles, defense systems, and much more.

HDI PCBs provide higher wiring density while further reducing the size of conventional circuit boards. The resulting electronic gadgets are smaller, lighter, and more efficient. The shorter signal path also increases the data transmission speed.

HDI PCB is constructed using smaller lines and spaces, micro vias, and connection pads, all of which play a crucial role in its miniaturization, as you will see when you read ahead.


How to Achieve the Perfect HDI PCB


There are a lot of steps involved in creating the perfect HDI PCB. Let’s look at them in detail.


Material


Proper material selection is essential as it will determine the performance efficiency of your HDI PCB. Generally, materials are chosen depending on your project requirements and how the HDI PCB will be manufactured, but there are a few key questions you need to ask yourself. For example, will the material be able to withstand heat? Is it suitable for sequential lamination? What’s the dielectric constant and loss of the material?

If you are creating a high-speed data transmission device, you need a dielectric material that does well with thermal expansion, glass transition, high temperature, and more. But such materials are costlier.

Ideally, you need a material that has low loss and high speed, but since the cost will build up and complexity will increase, the most commonly used material is the FR-4 family. These materials offer average loss and speed and are ideal for analog and digital devices.


HDI PCB Structure


HDI PCBs are designed in multiple ways. Manufacturers use the following 3 formulas to build up layers as required.


1. 1+n+1
There is only one high-density interconnection layer in this type of HDI PCB structure.


2. i+n+i
In this type, there are 2 or more HDI layers on PCB. And the microvias are stacked or staggered on one or both sides of the circuit board.


3. Any Layer
In this type of HDI PCB, all the layers are HDI layers and easily connected. This is ideal for devices with higher complexity and stronger signal integrity demands such as smartphones, computer chips, etc.


Via Type
Next up is via type. There are a total of 8 via types used for HDI PCBs, such as blind, buried, through-hole, stack, staggered, micro via, etc. The choice between these can determine the final cost of your project and the manufacturing method and tools that will be used.

The most popular choice for HDI PCBs is micro vias. They help reduce the number of layers and size of the circuit board. Moreover, they can either be used as blind or buried vias, depending on how they are drilled and electrocuted.


Stackup Type
Based on how many layers you have, the order in which you stack them with blind holes is called stackup type. There are 6 stackup types, but only types I, II, and III are suitable for HDI PCBs.


Type I
In this type of HDI PCB, the micro vias are placed on one or both sides of the circuit board. The manufacturers first laminate the core and then use a mechanical drilling method. Then micro vias are drilled using laser technology due to higher accuracy and precision.

In this stackup type, you cannot use buried vias, although blind and through-hole vias are used. This stackup type is susceptible to heat damage and can lead to delamination.


Type II
This stackup type is a type of sequential lamination. There is one layer on both sides of the core. Manufacturers create an inner layer by mechanical plating and then laminate the inner layer with two extra layers, creating buried vias. More vias can be added with laser drilling. Here you can use blind, buried, and micro vias, although it has the same limitations as type I stackup.


Type III
In this type of HDI PCB, two layers on both sides of the core are drilled and laminated like above. In the end, there are a total of 6 layers in the HDI PCB. You need to put two or more micro vias on one or both sides in this type. This stackup type is generally recommended for devices with multiple layers, a higher number of BGAs, and a finer pitch.

The extra layers are helpful and make the HDI PCB more reliable and insusceptible to heat damage, but it also increases the manufacturing cost.
Prototype Testing


An HDI PCB prototype is a simplified version of your HDI PCB that you can test and analyze. Professional HDI PCB manufacturers create prototypes to check different designs and test the performance and efficiency of each. The prototypes consist of stacked, staggered, micro via, blind, and buried vias, so you can create any combination and see which works best.

There are multiple applications of HDI PCBs, from the healthcare industry to aerospace. HDI PCBs can be used on almost all electronic devices to manufacture gadgets with limitless capabilities. It's best to hire professional HDI manufacturers, like Hemeixin, for consultation on HDI design, layout, and manufacture. We hope this article helped!

 

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