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OCTOBER 2024 I DESIGN007 MAGAZINE 73 conductor fabrication and packaging technologies allowed for the design and manufacture of ever more complex MCM designs. Microprocessor makers such as Intel began exploring MCMs for their potential to combine multiple processors or memory chips into a single module to improve performance and efficiency. It was also a period when flip-chip interconnec- tion methods took off. ey originally used solder bumps and many still do, but hybrid diffusion/copper-copper bonding is being used more by high-end assemblers, espe- cially in the heterogeneous realm. e late '90s saw a change in terminology. e term high density interconnect (HDI) technol- ogy entered the industry lexicon and PCB fab- rication tools and techniques were draed for the fabrication of advanced packages required to keep pace with the relentless advances in semiconductor integrated circuit technology as they sought to continue to deliver on Gor- don Moore's prophecy that transistor count on leading-edge semiconductor chips would dou- ble every 18–24 months. e result was that feature sizes on the mod- ules continued to shrink. Today, HDI packages commonly have line and space measurements of 50–75 microns (2–3 mils) and microvias have similar sizes. On the heels of HDI is ultra high-density interconnection (UHDI), where bleeding edge features are heading toward single digits. To participate in the manufactur- ing of these leading-edge interconnections, the facility must employ tools and technologies that just a couple of decades earlier were used to make semiconductor chips. ese advances have put pressure on designers and develop- ers to deal with the inevitable impact of greater density and higher speeds, the challenges asso- ciated with greater heat dissipation, and more critical signal integrity. Today (and for the past decade), Asia has been manufacturing most of the bleeding-edge HDI and UHDI-enabled IC packaging sub- strates. However, there is a concerted effort in the U.S. to ensure that native capacity exists on native soil. e CHIPS Act provides fund- ing for improvements in America, and there is expressed intent to build a facility for demon- strations and training to build up a workforce. e Department of Defense Executive Agent for Printed Circuit Board and Interconnect Technology has been championing this effort for several years. With over 50 years in the electronics manu- facturing industry, I find it fascinating how oen technologies are recycled and given new names by those driving the next trend. What is next? Arti- ficial Intelligence (AI) is upon us and its impact will be huge in terms of speed, bandwidth, and energy consumption. One thing appears certain: While we wait for the photonic synaptic transis- tor to be fully commercialized, we will continue to push electrons through copper for many years to come and can expect to be challenged by those charged with making the next generation of elec- tronic devices. So, have fun. DESIGN007 Joe Fjelstad is founder and CEO of Verdant Electronics and an international authority and innova- tor in the field of electronic inter- connection and packaging tech- nologies with more than 185 pat- ents issued or pending. To read past columns or contact Fjelstad, click here. Down- load your free copy of Fjelstad's book Flexible Cir- cuit Technology, 4th Edition, and watch his in-depth workshop series "Flexible Circuit Technology."