Issue link: https://iconnect007.uberflip.com/i/1464168
28 DESIGN007 MAGAZINE I APRIL 2022 What is the maximum size of a dam between these two? Assuming that LDI technology is used, the dam size results from applying the state-of-the-art constraint of the technology. is 200 µm pitch decreases by the laser beam width plus the registration accuracy twice— one for each pad. erefore, it quickly comes down to 100 µm. Any more challenging a pad distance will also make it harder to define a dam. From this reasoning, the many requests to create 50 µm dams or less with traditional technology seem legitimate. So, what do we do with inkjet printing? Does it join the race to the last microm- eter? No, instead it challenges the ini- tial design choice, which already spurs debate 1 : Will it be solder mask defined (SMD) pad or NSMD pad? Neither of the two. Instead, it will be pad-defined solder mask (PDSM). Unfortunately, this acronym is not a thing yet, so there is no point in googling it. Inkjet is a volume- driven coating technology, which means that filling gaps is possible and, in this case, even encouraged. 4. Defining the Thickness The definition of thickness means that the spectrum between coating conformality (Figure 3) and topography- independent flatness can be seen (Figure 4). What is the best choice? What solution of thickness design would better fit the solder mask requirements? PCB designers know exactly what the tasks of the solder mask are 2 . Still, the "inkjet upgrade" reviews the basics: While copper without solder mask can oxidize, laminate does not. Copper traces with high voltage without solder mask could create short circuits while bare lami- nate does not. erefore, laminate does not need solder mask. e reasons for the solder Figure 2: The choices are depicted here as a sketch and as its resulting cross-section. Figure 3: Laminate and copper coating meet the target thickness of 23 µm ±5 µm. The thickness transition between the two levels is chosen to exceed the target thickness to ensure mechanical stability. (Source: ACB-Atlantec SAS)