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SMT007-Jan2021

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12 SMT007 MAGAZINE I JANUARY 2021 would be where you'd measure the volume of the stencil printed brick of solder paste for sta- tistical process control. That's a simple exam- ple of continuous improvement. There could be others that weren't so directly related to just improving quality. You could have issues where you look at the amount of time it takes from the receipt of the order until you start the job on the line because you've been losing customers who say, "Geez, we like the quality of your stuff, but you're two weeks longer than our other suppliers." Then, you would do a mapping of the process of when the order comes in. What happens to it? You go through all of those steps and find there's a lot of dead time. There is one that's not related to something like solder paste stencil printing quality but is related to the process itself. There's a common expres- sion in Lean called "mapping the process." The comical thing about all this is when you really think about it, it's common sense, but common sense is not so common. Barry Matties: Often, until the process is visible or mapped, the process inefficiencies remain invisible because it's "just the way you've always done it." Lasky: Yes. We had a student at Dartmouth that was getting a Master of Engineering Man- agement (MEM) degree where we taught Lean processes. He had a summer internship with a company, and they had about seven build- ings. This wasn't making electronics; this was making valves. At the time, in 2015, the com- pany had existed since 1890. It started with one building, and they continued adding until they had seven. Because technology changed, it was now a 30-step process where they would do different steps in different buildings. It was just the way it grew. However, they never thought to streamline it, and the student pointed out that they could reduce their costs by at least 10% because of the transportation between buildings. When- ever you transport something, you're going to break some of them. These are basic princi- ples that people should consider in continuous the list. Usually, you would want to attack the most significant defect mode. That was shorts. They started to look at what typically causes shorts. Two-thirds of end-of-line defects can be attributed to stencil printing, so that is good place to start. This mom-and-pop shop may hire a local college student as an intern, who has a Lean Six Sigma Green Belt, and they teach the intern about electronic assembly. The company may also have pictures of all 2,000 defects. They analyze those images and decide that the main reason they had too many shorts is that there's too much solder paste on the pads. When the component is placed, excess solder paste spills over the pad that occasionally, when it melts, creates a solder bridge to an adjacent pad. They do some more work and decide that maybe they should make all of their stencil apertures a little tighter, or maybe they should get a different solder paste. They call their cur- rent solder paste vendor and discuss some of these issues. Often, you have to do some designed exper- iments, which would be the improved part of the DMAIC process, and then the control part Ron Lasky

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