SMT007 Magazine

SMT007-July2019

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8 SMT007 MAGAZINE I JULY 2019 Nolan's Notes by Nolan Johnson, I-CONNECT007 Reliability vs. Failure Summer is officially underway here in the Northern Hemisphere, and just like the tem- peratures, we're turning up the heat in this issue and getting technical. Enter "Reliability Man," the hero who must persevere against all the challenges thrown in his path. It should come as no surprise that solder and solder joints are often at the center of attention in electron- ics assembly when discuss- ing failures and reliability. Failed components aren't under the direct control of the assembly operation nor is a board failure. But the joining of the two? That's all you, contract manufacturers. Thankfully, there is a significant amount of ongoing research into the specialty of sol- der joint reliability. Lead-free initiatives continue to drive this research. Industry watch- ers might say that we're just now beginning to understand a few of the long-term effects of removing lead from sol- der. Some space and mil-aero applications con- tinue to specify tin-lead solder only. For these applications, one can argue that environmental impact is simply not a high-pri- ority concern; their products are not generally destined for the land- fill. But long-term reli- ability in an environment where repair is not an option and safety and survivability are critical is a high-priority concern. But the solder evolution isn't limited to electronics. My neigh- bor is a plumber. Every Monday, he stops by my house to pick up three dozen eggs—about a day's production when one's res- idence comes complete with 50 laying hens—so I asked him how he likes lead- free solder for pipefitting. "It works," he said, "but it's a completely different skill set to use lead-free solder. It doesn't behave the same." Readers who work in the assem- bly industry know exactly what he's talking about. Don't get me wrong; I'm not anti-RoHS. My point is that there is a great deal of ongo- ing research into materials, chemistries, ther- mal profiles, and precise process controls to create that completely different skill set my plumber neighbor had to teach himself. This is

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