Design007 Magazine


Issue link:

Contents of this Issue


Page 25 of 125

26 DESIGN007 MAGAZINE I APRIL 2022 Feature Article by Luca Gautero SUSS MICROTEC Although I am not a designer by trade, I want to share my thoughts on what additive manu- facturing means for designers, especially how it relates to solder mask. e following are the topics I feel are most important to address. 1. Definition of Solder Mask By its nature, the definition provided by any EDA tool is a negative one; the CAM vector files specify what goes away from an assumed continuous surface. Until now, solder mask has always presented itself as subtractive. SUSS MicroTec developed a front end, JETxSMFE, that can operate at the CAM station to smooth out manufacturing. e soware understands all of this, managing the details correctly on the incoming files. 2. The Advantage of Inkjet Solder Mask One advantage of inkjet solder mask is to avoid any filling of holes or vias. Another way, maybe an annoyance to some, is to say that "tenting" is not possible. Still, the consensus is that solder mask-free vias improve a board's reliability (Figure 1). e JETxSMFE removes solder mask at declared holes. Undeclared drills, which might still exist depending on the manufacturing convention on the production floor, will result in ink on the print table. is is not a big issue as a scraper easily removes excess solder mask, and alterna- tively, replacing the table or its liner (if present) gets the job done. How- ever, both solutions lead to a small downtime. Long story short, if you want friends on the shop floor, be sure to have all the drills in your design. 3. The Dam Dogma ese small solder mask traces on laminate are supposed to separate two nearby copper pads. Such a pat- tern indicates the non-solder mask defined (NSMD) pad design choice. However, this choice involves sev- eral constraints, and these create an artificial need for narrow dams. From my earlier example, this time with numbers: Imagine two pads, 200 µm apart, nothing extreme. Additive Manufacturing Requires Additive Design Techniques Figure 1: A cross-section of a via after solder mask coating. The trace connecting the pad extends further on the right side and is covered by solder mask. (Source: ACB-Atlantec SAS)

Articles in this issue

Archives of this issue

view archives of Design007 Magazine - Design007-Apr2022