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High-Density Interconnect PCBs

Your Valued HDI Printed Circuit Board Supplier

high density interconnect boardHigh-density interconnect (HDI) printed circuit boards are the rising star of the PCB industry. HDI PCBs use a combination of buried and/or blind vias plus microvias — those of 0.006″ or less in diameter. As a leading HDI printed circuit board supplier, we’re able to work with and deliver boards that have a significantly higher circuitry density than your traditional PCB.

Most high-density circuit boards fall into one of six different categories. They are PCBs with:

  1. Buried vias and through vias
  2. Coreless construction using layer pairs
  3. Alternative constructions of coreless builds that use layer pairs
  4. Passive substrate constructions with no electrical connection
  5. Through vias from surface to surface
  6. Two or more HDI layers with through vias

HDI technology in printed circuit boards and other areas has been a key driver for developing many of the electronics we use today, especially those whose form factors have significantly decreased in size and weight in recent years.

The smaller the equipment gets, the more likely HDI plays a role in its function. That means you need to work with an excellent HDI printed circuit board supplier, because even a small defect or layout mishap can cause major problems in those tight tolerances.

Benefits of Using HDI Technology

One of the biggest benefits of high-density circuit boards is that you can secure more components on both sides of the raw PCB, expanding the overall capabilities of the PCB and equipment. This efficient use of the landscape is done through processes including via-in-pad and blind via technology.

The better your partner is at using these techniques, the closer components can be placed together, decreasing overall component size and pitch to allow for an overall smaller form factor. Smaller sizes correlate to quicker signal transmissions and greater reductions in overall signal losses, as well as crossing delays.

Design Considerations for High Density Interconnect PCBs 

awesome-brain-vector-mc-dl [Converted]What to Take Into Account?

HDI PCBs require a much higher pad connection and wiring density than your traditional PCB, so you’re working with smaller capture pads and often extremely small vias. These boards can handle high-speed signals but need tight tolerance controls to ensure that they reduce signal loss.

Lamination and Materials

Via in Pad Process

The via in pad production process allows vias to be placed within a surface of the flat lands on your PCB. The via is plated and then filled with a variety of fill types. Then, it can be capped and plated over. It’s typically a 10 to 12-step process and requires specialty equipment and technicians to prevent things like sucking solder off of the pad or your ball grid array.

Via in pad is a smart choice for HDI PCBs, because it can help with thermal management, reduces space requirements and can provide one of the shortest ways to bypass capacitors for high-frequency designs.

Via Fill Types

Via fill types should always be matched to your specific application and PCB requirements. Via fill materials that we work with on a regular basis include electrochemical plating, silver-filled, copper-filled, conductive epoxy and nonconductive epoxy.

The main thing your via fill should leave is a via that’s flush within the flat land and will solder completely, just like normal lands. Fills must support the ability for microvias and standard vias to be blind, buried or drilled, followed by plating to hide it beneath SMT lands.

We often use multiple drill cycles at precisely controlled depths to ensure that the drilling process is done right each time, but this level of control does require specialty equipment and a longer development time.

HDI Structures

High Density Interconnect PCBs come in a few different layout and construction options, but some of the most common include 1-n-1 PCB and 2-n-2 PCB.

A 1-n-1 PCB contains a single build-up of high-density interconnected layers, so it’s essentially the “simplest” form of HDI printed circuit board. For the 2-n-2 PCB, you’re looking at two HDI layers, where microvias on different layers can be staggered or stacked. You’ll usually see some copper-filled stacked microvia structures if you’re working with a complex design.

Structures can climb to very high X-n-X levels, though the complexity and cost usually limit the buildup.

Another important option is the “any layer HDI.” This involves an extremely dense HDI layout so that conductors on any given layer of the PCB can interconnect freely with the laser microvia structures. These are common devices with large pin counts, such as your GPU and CPU chips in smartphones and other mobiles.

Laser Drill Technology

Any layer HDI designs often require laser microvias that must be created with laser drills. This means using a special piece of equipment that generates a laser at up to 20 microns in diameter. That may sound small, but it can cut through both metal and glass with ease, generating very tiny but very clean holes. You can get even smaller holes by using modern materials such as uniform glass that has a low dielectric constant.

LDI and Contact Imagery

Being a leading HDI printed circuit board supplier means pushing the envelope. MCL is able to deliver finer lines with leading development technology and clean rooms that ensure safe and secure processing. When it comes to these fine details, repairs aren’t possible, so it must be done right and extremely precisely the first time.

We alternate between contact imaging and LDI imagery based on what’s needed for verifying your equipment. LDI is the go-to for fine lines and minute spacing, because it can verify even the most demanding processes, continually expanding our capabilities and driving the HDI market smaller and smaller.
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Industries and Applications

Some of the most common devices and industries that we’ve seen HDI printed circuit boards used in include:

  • Automotive electronics and engine controls
  • Computers, including laptops, tablets and wearables
  • Connected and “smart” devices for the home and industrial settings
  • Digital cameras
  • Digital video and audio
  • GPS
  • IoT manufacturing and warehousing equipment
  • Personal communications
  • Routers, switches and modules

Why MCL?

Millennium Circuits Limited has been delivering engineered HDI printed circuit boards for more than 10 years, and we believe that no order is too small and no tolerance is too tight. Our customers leave satisfied, and have rated our work at an excellent quality 98% of the time, and we’ve delivered more than 99% on-time performance.

Pair that with competitive pricing, quick quotes and response times, domestic and offshore manufacturing and an unprecedented level of flexibility, and you have a winning combination for all of your High-Density Interconnect PCB needs.

Learn how much we can help you achieve and save by getting your quote today.

See MCL’s other products: High Speed Digital, Heavy Copper Boards, Flex Circuits and Other PCB Products