Issue link: https://iconnect007.uberflip.com/i/1330321
62 PCB007 MAGAZINE I JANUARY 2021 the advantages to using inkjet? Why would you want to do direct or inkjet? They don't en- tirely overlap. Carignan: Very few people would go back to standard imaging because you don't have the advantage of being able to actively scale prod- ucts. For registration capabilities today, it's a major milestone. It's a major part because now you have image acquisition. You're able to en- sure a much tighter hold to pad and solder mask dam placement. These things have gone up exponentially at the expense of not having to train operators. There's no technique. It's analogous to the printing industry for quite a few years there in the computer-to-plate (CTP) market where you just go from a CAM file di- rectly to an imaging set without an intermedi- ary. On the inkjet side, the advantage is that it's additive. Instead of having to coat or spray coat an entire panel—and then going through a lot of pre-cure, imaging and development steps, which are all power and water consum- ers—you skip those because it's an additive technology. It eliminates a lot of process costs. And, it comes without the penalty of relying on operator technique. It's built into the soft- ware. It's another CTP-type process where you go from a CAM station directly to an inkjet sys- tem. There are progressions in the market. Feinberg: Once you get the image on there, how is it cured? Is it air-dried, baked, or photo- cured? What is the typical curing procedure for an inkjet image? Carignan: That's a good question. You may be more familiar with inkjet used in legend print- ers, which have been around for at least 10 years. Very similar to that technology, we're inkjetting small droplets down to the 2–3-pic- oliter droplet size, which makes this technolo- gy viable. Following the inkjet printhead in re- al-time is a UV cure unit. It's UV cure, but it's very similar to the inkjet system. It allows you to handle and take any of the solvent or tacki- ness out of it so that you can do both sides at the same time; but then it does need a fi- nal cure. There's a thermal component that re- mains, which is similar to how we do solder mask today, to get it fully cross-linked and cured. And you need to get up to a tempera- ture around 300°F for about an hour. Feinberg: It's kind of like a standard UV cure or a 360-nanometer cure. Carignan: And it's LED. Similar to direct imag- ing, it's all a UV LED area as opposed to vis- ible light. It looks a lot like an inkjet printer, except the interesting part is that you have a print strategy. There's a little bit of a learning curve for everyone regardless of the system of choice, but you have a print strategy. It isn't like you would picture a solder mask, and you put a droplet in one space representing one pixel. You would do many small coatings, and you could make decisions on how you want to build up the layers, what thickness you want to build layers that's best to surround features first, and then fill in between. In most com- panies, they call it a print strategy. What do you have to do in order to print the resolution you're looking for? The software is the enabler to decide on the best strategy. There are some canned routines, but it opens a lot of doors in terms of how you might apply it. The most pleasing part of it, from being in the board industry most of my career, is you no longer have to coat. You don't have to mix, coat, tack, expose, or de- velop. You just go from your Genesis or CAM station directly to start printing solder mask. The only peripheral step is going into a ther- mal cure oven at the end. Johnson: The ability to do this work becomes more process and less art, if you will, by mov- ing to direct imaging and then to inkjet and additive. Can inkjet just drop into a traditional prototype shop, or is this something that lines up more with mSAP/SAP type processes? Are there some restrictions as to where you can use inkjet? Carignan: There's a new type of ink that bears no formulation comparisons. It's probably 1%