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70 SMT007 MAGAZINE I MARCH 2023 to see a film, Andy and Sue would both get dis- tracted reading the Spanish and then, if the translations were off, would let out a sigh. At dinner, they discussed how the work was going at Castellanos Electronics, as they had only a little over a week to wrap things up. "With José and some of his team, we have implemented the process improvement oppor- tunities that Chuck and José identified. e new solder paste that has excellent response- to-pause has really helped improve productiv- ity," Andy began. Sue asked, before taking a bite of her meal, "You were also working on line balancing, right?" "Yes, surprisingly, their uptime wasn't too bad, but the lines were almost never time bal- anced for the component placement machines," Andy replied. "By time balancing the placement machines, production improved 8%. ere was one case where the chip shooter was taking 55 seconds and the flexible placer only 26 seconds, meaning cycle time was 55 seconds. By mov- ing some components off the chip shooter to the flexible placer, each machine needed only 47 seconds—a time savings of about 15%." He then shied the conversation to ask Sue about her progress. "How's it going on the Pareto chart?" (Figure 1) "We've made significant progress on grap- ing, head-in-pillow (HIP), voiding, and insuf- ficients, and we have only tombstoning le to work on. In all cases so far, we have reduced defects by 90% or more," Sue said excitedly. "So, what is your plan for tombstoning? I'm interested, since I don't know much about it," Andy said. "Tombstoning occurs in the reflow oven when one side of a passive solder paste deposit melts before the other side and the surface tension of the melted solder pulls the passive upright like a tombstone," she said. (Figure 2) "So, we either have to prevent the one side from melting too rapidly or reduce the surface tension forces?" Andy asked. Figure 1: A Pareto chart of defects at Castellanos Electronics.

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