Working with ultra-thin substrates requires tools that are not commonly found in every PCB shop but once you have those tools at your disposal you can achieve results that are hard to match. Think of a finished circuit board that is just .002” (50 micron) thick, think of .001” (25 um) diameter holes, think of delivering dozens of high speed signals within a package that weighs less than 2 grams. We build boards like that every day at Circuits.