HDI Technology - Flex Circuits

Reading time ( words)

High density interconnect (HDI) is the process of leveraging manufacturing capabilities and materials to create very small interconnect solutions. Small interconnects are required for some of the new applications and dense components on the market. It is the next generation of etched circuitry.

Benefits of HDI

• Higher density and smaller size
  • Use of advanced component packaging
  • More design options and flexibility
  • Improved electrical performance and signal integrity
  • Improved thermal performance and reliability

HDI Applications

Wearable technology is one of the new applications we are seeing where dense packaging is required. Imagine wearing a sensor device that can monitor all of your vitals and connect to the internet via Bluetooth so your doctor can monitor you remotely. The solution has to be bendable, stretchable, and dense. We will talk more about this in upcoming columns, but this is the type of application that drives density.

Equipment

Gone are the days of plants with rooms full of noisy drilling equipment. HDI requires smaller holes and blind and buried vias that are best done with laser technology. Lasers provide a faster, more cost effective solution over drilling (after you get over the sticker shock cost of the equipment).

Materials

Very thin copper materials are essential to creating high density solutions. Nine-micron copper is what is used in many cases to create HDI solutions. Thinner materials are on the horizon. New higher speed materials—coverlays and adhesives—are being qualified on a daily basis to meet the challenges of higher speeds and impedance requirements.

HDI Lines, Spaces and Hole Sizes

Smaller lines and spaces are required for HDI. Today, 50-micron (2-mil) lines and spaces in production and 37.5 microns (1.75 mils) line and spaces are being provided in prototypes. The laser drill enables smaller hole diameter (50-micron hole diameters) and enables blind and buried vias for even denser packaging.

Resources

HDI requirements and equipment push flex vendors to invest in better educated human resources. The complexity of the circuits and the software for the equipment to make the circuits is driving circuit vendors towards a better educated work force.

HDI Assembly

Many industry flex circuit gurus discuss HDI with regard to the density of the package—the circuit itself. However, in addition to the package, an HDI flex requires HDI assembly—the need to place 1005 components and 12-mil pitch BGAs.

The flex circuit industry in North America is moving rather quickly. The packaging densities are moving to smaller and the electrical requirements much faster. In order to keep pace with the industry requirements of HDI, North American flex vendors need to invest in equipment, resources and R&D. 

Mike Morando is VP of sales and marketing for PFC Flexible Circuits LTD.

 

 

12/16/2019 | Pete Starkey, I-Connect007

Since 2016, the Institute of Circuit Technology (ICT) has held its northern area Christmas seminar at the Majestic Hotel in Harrogate—the elegant and historic English spa town in North Yorkshire. Pete Starkey provides an overview of this popular ICT event.

12/02/2019 | Nolan Johnson, PCB007

Nolan Johnson talks with Brian Hess of Calumet Electronics and Mike Vinson of Averatek about the new, insertable additive processes that the companies are working on together to help factories running primarily subtractive processes to quickly convert to very high-density interconnect (HDI) features, including trace and space from 2.5-mil line and space to 1-mil line and space and below.

11/22/2019 | Kelsey Smith, All Flex

Many of the issues that arise when using a flex circuit come from a lack of knowledge about how to properly design one, especially when the circuit is required to bend. Many novices will design a circuit that calls for bending the flex in too tight of a bend radius, which can cause damage to the circuit and lower the reliability of the end product. This series of articles will focus on the seven key aspects to consider when designing for maximum durability and maximum “flexibility.”