The Impact of HDI on PCB Power Distribution


Reading time ( words)

High-density interconnect (HDI) technology is often used to meet the requirements of today’s complex designs. Smaller component pitches, larger ASICs and FPGAs with more I/O, and higher frequencies with shrinking rise-times all require smaller PCB features, driving the need for HDI. Beyond some of the more obvious electrical effects of the microvias used on HDI designs, there is also an impact to the power integrity the PCB. This includes different effects of mounted inductances of decoupling capacitors, changes in plane performance due to reduction in perforation from chip pinouts, and the inherent plane-capacitance changes from using dielectrics of various thicknesses.

HDI Primer

HDI can be a confusing topic, especially for new engineers and designers, or those not well versed in the subject matter. Although this article is not intended to be an in-depth tutorial on HDI technology, a quick review of the key aspects is appropriate.

HDI is a technology that, through a combination of high density attributes, allows for a higher wiring density per unit area as compared to traditional PCB technology. In general, HDI PCBs contain one or more of the following: reduced trace width and spacing, microvias including blind and buried, and sequential lamination.

Current generation HDI designs are typically found in mobile phones, digital cameras, laptops and wearables to name just a few. Basically, whenever a product needs to be compact and/or lightweight, then HDI technology will most likely be applied. The benefits of HDI technology include:

  • Reduced space requirement using smaller vias, reduced trace width and reduced trace spacing, all of which allow components to be placed in closer proximity
  • Reduced layer count as a result of increased routing channels on internal layers
  • Improved signal integrity due to shorter distance connections and lower power requirements
  • Improved power integrity due to ground planes closer to the surface parts and improved distribution of capacitance
  • Potential to lower fabrication and assembly costs by consolidating multiple PCB’s into a single PCB

When utilizing HDI technology, two basic HDI structures exist:

  1. Build-up or sequential build-up (SBU) structures
  2. Any-layer structures

A key aspect of HDI technology is the use of microvias. For reference, the IPC HDI Design Committee has identified microvias as any hole equal to or less than 150 microns. Multiple types of HDI stack-ups associated with blind and buried microvias can be used to meet the density and cost requirements for today’s products. Design teams should develop stack-ups in conjunction with the board fabricator to minimize cost and meet signal integrity requirements. There may also be additional requirements related to plating and specific materials. As a rule, the vendor will adjust all the stack-up variables as needed during their process to meet the end-product requirements.

To read this entire article, which appeared in the November 2017 issue of The PCB Design Magazine, click here.

Share

Print


Suggested Items

Project MARCH Students’ Exoskeleton Helps Paraplegics Walk Again

04/10/2019 | Andy Shaughnessy, Design007 Magazine
Project MARCH student volunteers design and build futuristic exoskeletons that can help paraplegics walk. The students do most of the work themselves, including designing the various PCBs. I saw their latest exoskeleton up close at AltiumLive in Munich, and I had to find out more about this program. Delft Students Martijn van der Marel and Roy Arriens sat down with me to discuss their work on the exoskeleton, including their PCB design experience, and whether they plan to pursue PCB design as a career.

Kelly Dack at IPC APEX EXPO: The Attendees Speak!

04/04/2019 | Kelly Dack, CID+, EPTAC
During IPC APEX EXPO, Guest Editor Kelly Dack and the I-Connect team roamed the show floor, recorders in hand. They asked various attendees for their impressions of the show, and any new tools and technology that may have caught their attention. These are their stories.

SimplifyDA: Time for a New Autorouter Paradigm?

03/28/2019 | Andy Shaughnessy, Design007 Magazine
At DesignCon, I spoke with SimplifyDA CEO Zen Liao and Director of Sales and Marketing Dale Hanzelka. SimplifyDA is putting a new twist on the old autorouter by utilizing topological technology. I asked them to discuss their approach to autorouting, and how they plan to entice more PCB designers to use routers. Is it time for a paradigm shift in autorouting?



Copyright © 2019 I-Connect007. All rights reserved.