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44 DESIGN007 MAGAZINE I JUNE 2021 Mirror Mirror Let's start with reviewing the main forces that have driven PCB technology in the recent decades—and most likely will keep driving it for years to come. Miniaturization Star Trek technology has always focused on miniaturization; the original series featured tiny cathode ray tubes on portable scanners. Over the run of the show, communicators shrank from hand-held devices to pins worn on your clothing. Miniaturization has been so ubiquitous within our society that it has been reflected within the series reboots. In the Kelvin time- line (alternate reality), Hikaru Sulu, for exam- ple, carries a folding sword, a gadget that he likely keeps on hand in case of an impromptu polywater intoxication. Since the early 2000s, every one of us has owned a handheld device that would outper- form the most powerful supercomputer of the 1960s. Under the hood, smartphones hide multilayer, high-density boards with hundreds of components under severe physical size and weight restriction. Computational Power At the same time we see miniaturization of hand-held technology within the universe, we have also seen examples of the opposite hap- pening—each iteration of the Enterprise is a little bigger, many of the ships larger. A good comparison might be looking at the size of the Doomsday machine in the original series to the Dyson Sphere in Star Trek: e Next Genera- tion. e second is orders of magnitude larger than the first. When relaunching the series, there has always been some element of super- power present. Whether it is V 'Ger in the Star Trek: e Motion Picture, or the Narada, Nero's ship from the 2009 movie, size, power, and complexity are always present. In reality, autonomous cars, electric vehi- cles, medical electronic instruments, internet- of-things devices—all these and more require complex and powerfully interconnected elec- tronics. Industry is moving toward a more collaborative manufacturing experience, with cloud-based DFM tools like PCBflow enabling and streamlining this collaboration, your fabri- cation partner's manufacturing constraints are instantly available to you. The Trouble with Tribbles Interesting enough, while these trends can look quite contradictory one to another, they result in the same trends in PCBs: high density. While there are many definitions for high-den- sity interconnect (HDI) boards, they all agree that they contain fine traces, small spacings and laser vias. On HDI boards, real-estate is expensive. It is advisable to use every 0.1 mil available to make fine trace spacing larger in order to increase the fabrication yield. Setting differ- ent target spacing values for different features with respect to their functionality can make all the difference. Under no density constraints, it is quite com- mon to route different traces using the same width. With HDI boards containing fine traces and tough spacing constraints, it is helpful if mission-critical traces are slightly wider when spacing allows. Even 0.1 mil can make a tan- gible difference in fabrication yield. Perhaps surprisingly, these fine traces are produced in the same fashion as larger traces, Since the early 2000s, every one of us has owned a handheld device that would outperform the most powerful supercomputer of the 1960s.