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18 SMT Magazine • October 2017 cess variables heading into forming that solder joint that we get the most questions for," says Roush. "There's just been such a trend in the industry for products to become denser, with more components in such a small amount of area that the boards and the thermal loads have just dramatically shifted over the years, and they're looking for more performance to be able to give off thermal energy into the joint to form something strong and reliable in a reasonable time. We get many re- quests for trying to optimize the tip geometries or temperature se- lection or one of the other fac- tors going into it to really im- prove that process. There's only so much control they have over it. The tip geometry selection and solder, type of materials they're soldering to, and then the train- ing of the operator all goes into this big mix. In the end, they're hoping that they're getting a good solder joint. So that's really what they're looking for. "Probably the second most asked about trend is traceability. There's been a huge push in the last couple of years, especially among con- tract manufacturers (CM), to be able to provide traceability information to their customers for those solder joints. So, it's really that next gen- eration of how to collect this data and do some- thing with it." One of the soldering trends nowadays is the move towards automated hand soldering. So, is this a method for improving joints? Roush says with all the variables associated with just the id- iosyncrasies of operators—variation on the skill and experience level—a robot levels that play- ing field. "What you can't replicate on a robot, at this point, is knowing when something is go- ing wrong or there's an activity or a problem that crops up," he explains. "The robot is rela- tively dumb in that respect and it's just going to do exactly what you program in it. If its condi- tions change, for example, there's a bad batch of boards or there's something wrong with a component that's being put down, the robot won't know any better and will just continue to execute the program. So, I don't think they're going to totally replace it, but I see it more of a complement and a way to increase through- put." But on whether automated hand soldering provides a better solder joint, there are definite- ly tradeoffs, according to Roush. "There's some fantastic operators out there that are like machines, and they do a fantastic job of soldering. But I think that the challenge with robotic solder- ing is that for 99% of what's out there in the market, you have to program it on the safe side, and your tendency is to give it more time on the joints than may be necessary because you want to make sure that the joint is formed properly, because no one's watch- ing it. So, the time on joint may be four or five seconds and you only need it to be there three; that increases the amount of time it takes to produce the board, and you're putting more thermal en- ergy into the joint than you really need to, which can then impact IMC formation," says Roush. One of the latest technologies from Metcal, the Connection Validation soldering station, provides operators with real-time, closed loop feedback to indicate intermetallic compound formation—the key to a good solder joint. With the CV, Roush says the power supplies are at- tached to a robot and have an application, and whether it's a hand soldering or robotic solder- ing application, the feedback from the unit will basically indicate to the operator or to the ro- bot to move on to the next joint as the IMC is formed. "So, there's no real danger there of stay- ing on the joint too long or dwelling too long on a single joint," he says. From a contract manufacturers' standpoint, MC Assembly's Nunenkamp says there are pros and cons for all product development using ro- botic soldering irons and hand soldering irons. "Lack of a one-size-fits-all solution is part of the challenge. What Robert was referencing is spot on from the idiosyncrasies of the impact of an operator to the robot," he explains. "I have cer- ACHIEVING THE PERFECT SOLDER JOINT: THE MANY PERSPECTIVES ON SOLDERING Brook Sandy-Smith

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