Issue link: https://iconnect007.uberflip.com/i/1243344
MAY 2020 I SMT007 MAGAZINE 41 follow that tells you within 30 prints and only five hours of assembly line time, you're going to be able to gauge about 25 different paste properties and how they affect your line—not some lab's line, but your assembly line with your heat and humidity levels with your typ- ical placement forces and reflow profiles. That's a lot different from what we see in the lab. The delta from the lab to the line is huge in PCB assembly. That's why we like to test on the line, but we have to make it fast and economical. What used to take two weeks can now be done in about five hours if you use the test vehicle and follow the step-by-step instructions. Johnson: Am I right to assume, then, that when I order up the test board, there's a packet of 30 test boards and maybe even some compo- nents? Shea: I created a simple spreadsheet so that the users can look at the sample size and costs and determine what's best for them. Then they order directly from Practical. When we first decided to commercialize the board, we decided Practical would be the ones to take care of all the supply chain and order fulfillment. Shea Engineering and Henkel are out of the picture on that now; it's strictly Johnson: That makes a common benchmark test board all that more important. Shea: Exactly. We're running so much leaner. As we recover from the pandemic, we're going to have a lot of catch up to do. We don't have a lot of time to wait. Johnson: Walk me through how the board gets used then in the field. Shea: Typically, if you were using this to eval- uate a solder paste, you would take this board to run the top side and the bottom side, and we have nested some DOEs in there. The user does 10 prints top side, and populates three of the boards, and then sets that stencil aside and run the bottom side. While the top side stencil and paste are doing an idle time, the user prints five boards on the bottom side and then shears the solder paste on the bot- tom side for a couple of hours to mimic a reg- ular stencil life test and how it would per- form on the assembly line before printing five more. The user reflows some boards, rein- stalls the top side stencil, and then runs 10 boards again, to see the impact of idle time on printability. There's a flow chart you can follow. There's also a step-by-step Excel spreadsheet you can Bill of materials cost and sample size calculator.