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14 SMT Magazine • April 2016 The way Etratech traditionally determined printing quality was to have the operators audit the boards coming out of the printer. But, that is a subjective process, because while one oper- ator may believe quality is good, another may think otherwise. "You're using a certain amount of time to conduct an inspection, and it's not really ef- fective," Clarke says. "Beyond that, our exist- ing practice was to wait until the product came out of our inline AOI (automated optical in- spection) machine. But by the time the product comes out of our AOI machine, we're looking at about 20–30 panels in process on the line, which is typically a little bit too late for us to really start making corrections." That, he says, was the impetus to move to a new process. "It's all to do with having the inspection early, so we're getting the informa- tion in real-time as opposed to 30 panels later," Clarke says. The basic culture at Etratech is one that strives for zero defects, which in SMT all starts at the solder paste screening operation. "If you want zero defects further down the line, you have to make sure that your solder paste screen- ing process is as close to perfect as possible," says Renneboog. Of course, no process is ever perfect. The team became very adept at chasing defects down the line. The process allowed them to do a good job of catching defects, but at the cost of downtime, lost productivity and wasted labor. "Once we realized the process was ineffi- cient and that we needed to catch these defects immediately so they didn't cascade down the line causing a knock-on effect of other issues— then we were on the road to a new way of look- ing at the process, a better, more efficient way," notes Renneboog. "A process can work, and still be inefficient, but an inefficient process will get the job done at a premium. We got to the point where we didn't want to pay that premium any- more." The importance of process and End Quality "If the process is right—and when I speak of process I'm speaking specifically about screen printing—if that is right, it just means that we're looking at zero defects or ppm levels that are very low," says Clarke. "We would do rework on the boards which were coming off the line, so we were basically saying 'we know we're not going to build it right' even though our phil- osophy should have been build it right the first time." Clarke and his team knew that the process wasn't perfect, so to combat the problem they had rework stations set up that could handle the defects that had been seen. However, with the new process, the company has seen its ppm levels literally slashed in half. According to Renneboog, once the SJ Inno Tech screen printer was introduced into the mix, Etratech's manufacturing team went from receiving process indicators at the end of the line—which the team would then use to ad- just the printer—to the new printer actually being able to make adjustments on-the-fly in real-time. There is feedback from the internal solder paste inspection (SPI) to the screen print- er, so it can fine-tune the appropriate param- eters while it's running, which everyone agrees is a big improvement. That greatly improved both the quality and the cycle time of the process. "In terms of how it improves what we do, it's the difference be- tween having to call over a maintenance tech- nician, who might take anywhere from ten to 30 minutes to get the issue resolved on the line versus the line running continuously without interruption with the new printer," says Renne- boog. "Right now the system is self-correcting, in a culTurE of conTinuous imProvEmEnT, ProcEssEs conTinuallY imProvE If you want zero defects further down the line, you have to make sure that your solder paste screen- ing process is as close to perfect as possible.

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