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30 DESIGN007 MAGAZINE I APRIL 2022 • e cross-section of a narrow solder mask feature resembles a dome (Figure 2). e traditional rectangular cross-section is no longer present. Instead, an edge-less, cavity-less profile replaces it that increases mechanical stability and chemical inertness. • e structuring of the solder mask is based on layers. is means that additional geometrical features on top of the solder mask for mechanical support of compo- nents or confinement of dispensed coatings are also possible. As mentioned, today's CAM solutions cope with the details mentioned above: solder mask thickness, copper thickness and holes. How- ever, it is not yet the right place for defining it. Eventually, it should be something inte- grated in the CAM soware for manufactur- ing or, even better, already in the designing tool. e final dream is that the components themselves would impose on each location the desired solder mask thickness. is would make it all come together. Designers will put components to rest in peace, this time without a tombstone. DESIGN007 References 1. "Solder Mask Defined and Non-Solder Mask Defined in PAD," TechForum Digi-Key, November 2018. 2. "What is Soldermask (SM)?" Eurocircuits, 2021. Luca Gautero is product manager at SUSS MicroTec (Netherlands) B.V. and an I-Connect007 columnist. To read past columns or contact Gautero, click here. Feature Column by Michael Carano Is seems the operative word today is additive cir- cuit board manufacturing, or for that matter, additive for everything. It is true that the use of additive man- ufacturing technology has found its way into differ- ent industries. While there may be several advan- tages to adopting additive technology in various industries, one should take a step back and truly assess where we are today in relation to conven- tional and advanced printed circuit board technol- ogy. It makes sense to understand the differences between fully additive, semi-additive, modified semi-additive (mSAP) and subtractive. In the end, there are several options available to the fabrica- tor and OEM to achieve high density and ultra-den- sity circuitry to support higher end technologies, including IC substrates. Overview In my opinion, there is much confusion with respect to additive fabrication for printed circuit boards. Well over 45 years ago, there was full build (or "fully additive) circuit technology. One could employ a special pre-catalyzed substrate and build up the circuity with an electroless copper process. However, the circuitry would still need to be formed via subtractive process. Predating the full build electroless process was the CC4 technology. A microroughened substrate was coated with a metal catalyst, then plated to 25-plus microns over a 24-hour or so period. To read this entire column, which appeared in the February 2022 issue of PCB007 Magazine, click here. Trouble in Your Tank Additive, Semi-Additive and Subtractive Fabrication

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