Estimated reading time: 2 minutes

The Shaughnessy Report: Are You Partial to Partial HDI?

Sometimes, a little technology is all you need. Star Trek’s Borg character only needs a funky eyepiece contraption to access all The Collective’s data, like an outer space Wi-Fi. Like the Borg’s eyepiece, we may only need a little bit of HDI in one corner of the board. We might only need partial HDI.

As the name suggests, partial HDI refers to the targeted use of HDI, usually on one section of one layer of the board. It offers designers an avenue for escape routing from BGAs with a pitch of 0.5 mm or less, when a mechanically drilled plated through-hole is impossible. With HDI relegated to one layer of the board, fabricators can avoid the expense of sequential lamination cycles.

This process doesn’t cost much, nor does it have a long learning curve. However, designers using partial HDI must navigate a variety of signal integrity and DFM trade-offs. The ultra-thin layer of laminate that this option demands is unreinforced, which can create challenges. Because of these trade-offs, designers really should work with their fabricator during the design cycle.

This process has entered the mainstream of PCB design because it’s a fairly simple way to solve escape routing problems with many of today’s tight-pitch BGAs. Any experienced PCB designer, which means most of our readers, can start using this approach right away. But you need to know a few tips, tricks, and techniques first.

In the October 2024 issue of Design007 Magazine, our expert contributors provide a complete, detailed view of partial HDI. We kick things off with a conversation with IPC’s Kris Moyer, who has been teaching partial HDI in his advanced PCB design classes. Next, we have a column by Vern Solberg, who focuses on designing with HDI and UHDI. We also have a column by Happy Holden, who discusses partial HDI and several other similar constructions.

Insulectro’s Chris Hunrath explains how mSAP can be used in partial HDI, and why most fabricators are capable of creating mSAP features with their existing equipment. Siemens’ Stephen Chavez breaks down the details of partial HDI from the viewpoint of designers and EDA companies. Joe Fjelstad provides an overview of high-density construction in his usual, unique way. We also have articles by Anaya Vardya and Dean Neuburger, as well as a column by Matt Stevenson.

It's show time! Look for our upcoming coverage of the Anaheim Electronics Manufacturing Show, PCB West, SMTA International, and PCB Carolina.

This column originally appeared in the October 2024 isue of Design007 Magazine.