Advantages of A HDI Printed Circuit Board and Its Applications

Unlike a traditional PCB, HDI has high-density circuitry. It consists of different types of vias, including buried, blind, and micro-vias. Some other features of this PCB include:

• Surface to surface through vias
• HDI construction involves layer pairs
• Passive layers without electrical connection
• Minimum two layers having through vias

HDI PCBs are ideal for smart devices or electronics having less weight. You must hire an experienced manufacturer to have an HDI printed circuit board because it has very narrow tolerances. So, only experts can handle such a PCB, as a little defect can lead to serious issues.

What are the benefits of an HDI circuit board?

There are many advantages of the HDI printed circuit board, provided it is according to the design parameters. Your product can perform better with the HDI technology. Let’s study its benefits one by one.

It Needs Less Space

HDI circuit boards don’t take much space, so the overall weight of the final product is also less. You can have more components on a board’s both sides, getting a functional, small, and lighter device.

Better Electrical Function

You get an enhanced electrical performance through HDI because of a little distance between the components and more transistors. Such features involve less power consumption, resulting in better signals. The signal transmission becomes fast due to a smaller size, besides, there are lesser crossing delays and signal losses.

More Cost-Effective

Since an HDI PC Board is smaller than traditional boards, it needs fewer raw materials, hence its cost is also less. Instead of having multiple PCBs in one product, a single HDI PCB is enough for better performance through small size and minimum material.

Quick Production

The production time is also faster than the conventional boards. Your product gets ready for selling if its construction involves an HDI printed circuit board having minimum materials. It is easy to place the components on HDI boards, moreover, better electrical performance is there to reduce the troubleshooting and testing time.

More Reliable

The micro vias in the HDI PCB come up with small aspect ratios and involve high-quality manufacturing, making the board reliable. A reliable PCB is always cost-effective, so the end product is also reliable and satisfactory

What To Consider While Designing An HDI PCB

You have to consider certain factors and parameters while designing the HDI circuit board. The production of such a board is different from others that we will discuss below.

Lamination Process

High-density PC Board Fabrication involves sequential laminations where you have to combine the PCB layers or cores with copper and pre-set layers. It involves heat and pressure according to the type of the circuit board. Once the lamination is over, you need to drill vias several times, unlike a traditional PCB. So, such a sequential lamination process helps manufacturers have flawless drilling without any breaking or shifting.

Understanding The Via-In-Pad

The construction of the high-density PCB involves the via-in-pad process to help you to make vias on a flat surface of your PCB. You have to plate vias, filling them in different ways, capping them, and then plating over them. The process of via-in-pad consists of 10 to 12 steps, and it needs skilled workers and special tools. There are many benefits of using the via-in-pad for HDI boards, including reduced space, simple thermal management, and less time to bypass the capacitors, in the case of high-frequency layout designs.

Considering Via Fills

You should also consider the type of via fill as it has to be compatible with the PCB requirements and its application. Some common filling materials, in this case, include electrochemical plating, copper, silver, and conductive and non-conductive epoxy of which non-conductive epoxy is highly used. Moreover, via fill should be flushed with the flat surface of the PCB and should also be fully soldered.

The via fill helps develop the blind, buried, and drilled vias in the case of both standard and micro vias. Then comes via plating to hide it under the SMT surface. It involves several drill cycles at balanced depths to have precise drilling. Such well-controlled drilling needs special tools and more time.

Layout Options

You will see the HDI circuit boards having different layout designs, including

• 1-n-1 PCB
• 2-n-2 PCB

A 1-n-1 PCB is the simplest HDI circuit board as it is a single construction of multiple layers of high density. These layers are interconnected, and such a board needs sequential lamination on both sides of the core. Whereas the 2-n-2 PCB consists of two layers of high density to help you to stack micro vias around the layers. The micro vias have copper filling in the case of complex layout designs.

The HDI structure can reach high levels of X-n-X even though its complexity and cost limit the construction. There is also the any-layer HDI with a very dense layout where conductors can interconnect easily through laser micro vias. You will see such designs in CPU and GPU chips, like in many mobile devices and smartphones

Laser Drilling

When it comes to the any-layer HDI, you will have to apply the laser drills to create micro vias. In this process, the drill emits a laser of 20 microbe diameter which can easily cut the glass or metal, providing small and clean vias. You can also use the uniform glass to make very small holes, as such a glass type has a low dielectric constant.

Cost of High-Density PCBs

Various factors can affect the cost of an HDI PCB, making it high or low. Here, we will discuss certain things to help you have a budget-friendly circuit board.

1-Quantity and Type Of Vias

Whether you choose a through-hole or micro vias, it will affect the cost of the board. Likewise, the number of holes also influences the cost. Larger vias will cost you less than smaller vias, as smaller ones are hard to create with precision.

2-Layers And Stack Up Height

The number of layers also affects the PCB cost. Likewise, you have to consider the height of the stack up to determine your budget. According to engineers, the 2-n-2 high-density circuit board’s design is more complex than the 1-n-1, so it costs you more. Moreover, extra layers also increase the PCB cost, so design your board carefully with a suitable number of layers.

3-HDI PCB Materials

The material you choose for your PCB also determines its cost. Some common core or base materials, in this case, include metal, fiberglass, FR4, etc. Whereas the finishing materials can be ENIG, immersion tin, HASL, gold, immersion silver, and many others.  Most manufacturers use the ENIG as it is smooth and easy to solder. You also have to consider the application of the board while choosing its material.

4-Quantity Of Sequential Layers

The number or quantity of the sequential lamination also affects the cost. The number of holes and the number of layers help determine the number of sequential laminations needed for HDI. Though more lamination means high cost and construction time, it ensures a reliable product that performs faster.

5-Type Of Setup

The type of setup also affects the PCB cost, like it is either stacked or staggered.  You can fill the stacked vias with copper, but it is not so with staggered vias. Via filling means you need additional materials and more time to produce your product or device.

6-Size of the Pad

You can decrease the cost by considering the pad size in the early stages. The HDI PCB design will be cost-effective if you choose the pad size wisely.

7-Less Turnaround Time

If you need your HDI board urgently, it would also increase its overall cost. An urgent order is always costly, so plan your project to avoid urgent construction and have a cost-effective project.

8-PCB Manufacturer

The PCB supplier or manufacturer should have competitive prices, or it will become costly for you. The supplier should offer a high-quality product at an affordable cost. Poor quality can end up in multiple repairs in the future, so select your HDI supplier wisely.

Applications of HDI PCB

HDI printed circuit boards are getting popular these days because of smart devices. High-density boards are not only cost-effective but they ensure high performance and reliable products.

• The HDI PCBs are used in multiple industries, including consumer electronics, such as smartwatches, smartphones, tablets, laptops, digital cameras, as well as many GPS devices. The high-density circuit boards are also essential for IoT devices that you need at homes, such as refrigerators and smart thermostats. All such devices have made HDI technology more in demand.
• HDI PCBs are also used in communication equipment that runs smart devices, such as routers, semiconductors, switches, and modules. Where there are radio waves in a gadget, means it has an HDI PCB. You will also see such circuit boards in digital audio and video equipment. From personal to network devices, all digital products come up with HDI PCBs.
• Another application of the HDI board is in the automotive industry. Likewise, you will see it in aerospace where devices and equipment have to be lightweight to perform better. The latest cars also come up with computerized equipment. Like, you will see cars with boards having 50 microprocessors to handle engines, diagnostics, and safety features.
• Similarly, the onboard Wi-Fi, GPS, backup sensors, and review cameras also depend on HDI printed circuit boards. HDI technology is constantly growing with the advanced automotive industry.
• These days, you will see advanced medical equipment and devices which also depend on HDI circuit boards. Such equipment is used for monitoring, scanning, x-ray, and lab tests. The high-density PCBs make medical devices more reliable, functional, and cost-effective. Doctors can get reliable test results for their patients with advanced equipment.

Hence, you can’t imagine advanced gadgets, devices, and equipment without HDI PCBs due to their smart components. Would like to know more about HDI PCBs or printed circuit board assembly? Email us at sales@pnconline.com

Written by Sam Sangani

Sam Sangani is the President & CEO of PNC Inc., a Nutley, NJ based Printed Circuit Board manufacturer. Sam graduated from L. D. Engineering College with a BS Degree in Mechanical Engineering. He also continued his education and graduated from Steven’s Institute of Technology where he acquired a Master’s degree in Computer Science.

After completion of his BS, Sam worked as a QC Manager, for Xerox, Romania and London. He was responsible for the Quality Control of Cable and Wire Harness imports from Romania. After completing his Master’s Degree, he worked as a Senior Programmer with IBM, Tucson, Arizona. Sam was responsible for leading the Mainframe System Programming Team.

In 1997, Sam acquired PNC INC., a Nutley, NJ based PC Board fabrication Shop. From 1997-2013, Sam has made tremendous improvements and changes within PNC INC., as he added many new Products and Technologies in PNC’s portfolio. With his proven track record and leadership, PNC has never had an unprofitable year and has continued its growth yearly since 1997.

His current responsibilities are Strategic Planning, Corporate Management, New Business Ventures, Sales & Marketing, Trade Shows, Professional Services and leading productive teams to achieve peak potential. He has also utilized Lean Management techniques which have built a foundation for PNC’s high-paced growth. Sam also enjoys real-estate investing, web design & SEO, trading stocks, options, futures and Forex markets.