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48 SMT007 MAGAZINE I DECEMBER 2019 Feature Interview by Barry Matties I-CONNECT007 Tom Forsythe, executive VP of KYZEN, dis- cusses what readers should know about clean- ing as reliability expectations continue to increase. He also explains what is driving the new interest in cleaning and why engineers from the no-clean generation may not even realize they need to learn more about cleaning. Barry Matties: Tom, why don't you start by tell- ing us about your new generation of stencil and misprinted board cleaner. Tom Forsythe: Absolutely. KYZEN E5631 has been under development for some time. The whole challenge for us, of course, is that con- taminants, fluxes, and pastes are constantly evolving. Many leading solder makers around the world are trying to improve their perfor- mance because our mutual customers are demanding improved performance from them. It trickles down to the cleaning folks to make sure we can remove those residues, whether it's uncured adhesives, uncured paste in a true stencil printing application, or anything down that road. That's the key, and it's an area that we've done a lot of research on over the last 5–10 years. It had been stagnant for a long time, but once you crack the egg and start working around, your development leads you in lots of different directions; that's how 5631 came to be. Matties: Is this driven by the finer features that are appearing? Forsythe: The finer features drive back to the stencils. The companies making the stencils have issues because they have to make aper- tures that are smaller and closer together and more well-defined. As those apertures get smaller, then it becomes a bit more difficult to get things out of those smaller apertures and have flow go through them. It all cascades. But it fundamentally comes down to the mate- rials. The bigger driver on the stencil side is the new materials. Remember, when you reflow paste, lots of volatiles come off. It goes through a state change and creates that hard encapsulant. When you're dealing with raw paste, all those goodies are still floating around. It's designed Clean vs. No-clean: A Generational Difference Tom Forsythe

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