Issue link: https://iconnect007.uberflip.com/i/911509
20 SMT Magazine • December 2017 Equipment Perspective Manncorp often deals with a lot of OEMs and companies that are just getting into their first SMT line and developing their own in-house ca- pability. "It's our job to suggest the appropriate equipment to be able to build the boards that the customer is looking to do," says Stone. Because of the nature of the customers and economics—wanting to save money where they can—they always feel that the stencil printer is not that important, and that they'd rather put the money into the pick-and-place machine. "Yet, if you have a pick-and-place with ca- pability to do 0201 or 01005 in ultra-fine pitch, and you buy the cheapest manual printer that you can get, you're not going to be able to bene- fit from all that capability. And that's something that you really must explain to the customer, and make sure that you're advising the correct equipment for the job at hand," says Stone. "In my opinion, a good manual printer for a start- up company is a good way to start. I mean, it's a good tool to have in your toolbox, but is it going to be able to do the most challenging devices out there? No, probably not. I would say, as far challeng- es that have been around more re- cently, we're see- ing a lot of activity in very large board printing, especial- ly for the LED in- dustry. We're see- ing circuit boards that are between 1,200 mm and 1,500 mm long. That's four to five feet—excep- tionally large com- pared to what we were used to. It used to be if you had a board that was 16" x 18", that was a really big board. Now, we're seeing boards that are really long, and you need specialized equipment to handle it. Those types of print- ers have to be super accurate, especially in the adjusting of the axis when it's aligning the sten- cil to the board. Because it is so long, your X-Y rotation is extremely critical. When it moves just a tiny little bit, when you're out there on the fringes, it's moving quite a lot. We're also seeing a lot of people getting into the 01005 printing, which has its own set of challenges. Again, you're going to need a good automatic printer, vision system, and all these program- mable parameters that you'd expect in any high-end printer. That's not something that you're going to be doing on a simple tabletop device." When looking at equipment for a given ap- plication, you need to make sure that all of the pieces are going to match, according to Stone. "That would be your stencil printer, your pick- and-place, and your reflow oven. It doesn't re- ally make sense if your application is to do the smallest, most challenging and most fine- pitched components to not buy a printer that would match. When you get into the more chal- lenging type of components, you're going to want something with fully programmable pa- rameters, your squeegee speed, down pressure, snap-off speed and so on and so forth. Also, very important is to have something that has an underside stencil cleaning ability to regulate the process and keep it uniform," says Stone. Choosing the Right Solder There are different parameters to consid- er when selecting the right solder paste for an application. According to O'Neill, the most im- portant thing to consider is whether you would use no-clean, or you anticipate washing. "Solder paste selection goes from there. Generally speaking, EMS providers like to wash their stuff because the customer's perception of quality is driven largely by visual, even if it's not accurate. As contract manufacturers are be- ing judged by the aesthetics of their final goods, washing is more common in the EMS world," says O'Neill. "On the other hand, OEM man- ufacturers traditionally go with no-cleans be- cause it's their products. Many times, it's sealed up in a box or an enclosure of some sort. No- body sees it. They perform the requisite reliabil- ity testing to ensure that their product's reliabil- ity meets their requirements, with the residues in situ. Leaving the residues in place is a much more cost-effective model. I would say that the EQUIPMENT MATTERS IN SOLDER PASTE PRINTING Edward Stone