Issue link: https://iconnect007.uberflip.com/i/1309864
92 PCB007 MAGAZINE I NOVEMBER 2020 a simple test using the stylus method to run profilometry and report the roughness value. The stylus method simply does not have the capability to adequately measure the surface roughness on these smoother and smoother foils. IPC recently released a new non-contact method for measuring surface roughness that was published this summer. We believe that this new method will cre- ate some greater consistency in the market. But we still find that not everybody mea- sures their foils in the same way. And there's a lot of discrepancy between copper-clad laminators and foil suppliers on how they're marketing these very low-profile foils and the nomenclature they're using to describe them. It has created a tremendous amount of confusion in the industry as to when a call out states the foil needs to be an ultra- low profile or HVLP, what does that actual- ly mean? One of the tasks that we're trying to work through in IPC right now is com- ing up with the nomenclature for these su- per smooth foils that aligns with test meth- ods. Our goal is to take out some of that con- fusion and ambiguity when describing the copper foil roughness. People are also starting to understand that there are all sorts of different things being done to the foil in order to get those nodules to actually stick to the copper surface for ad- hesion promotion. And there are different types of metals and inorganic materials that are used to passivate and protect the cop- per from oxidizing and chemical attack dur- ing PCB fabrication. There is a wide range of chemical adhesion promoters available that people are using to help find the right combi- nation for adhesion to the endless resin sys- tem types that the copper-clad laminators are using. None of these items are new, but now peo- ple are far more sensitive to the influence of copper foil on signal integrity. What do those passivation metals and inorganic materials do to the copper foil, and how do they interact with the dielectric material? Questions regard- ing the fundamental understanding of the cop- per process and the impact on signal integrity have become routine. Working with customer A manufacturing operator oversees the slitting operations at Denkai America.