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60 SMT Magazine • October 2017 by Stephen Las Marias I-CONNECT007 Voiding has become a big issue nowadays in electronics assembly. According to studies, voids reduce the life of the solder joint. In par- ticular, voids greater than 50% of the solder joint area decrease the mechanical robustness of the solder joints. To know more about voiding and its impact on solder joint reliability, I interviewed Jonas Sigfrid Sjoberg, technical manager for Asia at In- dium Corp., at the recent NEPCON South Chi- na event in Shenzhen. He discussed why void- ing has become an important issue in the SMT industry, and how manufacturers can address this issue. Stephen Las Marias: Why is voiding a such a big problem now in the industry? Jonas Sigfrid Sjoberg: In the past, the compo- nents are not running as often as they are today, so what's happening is that the components are getting much hotter while they are being used. The thermal pads, especially for the QFNs, are there to lead away heat. Many customers, around five years ago, are saying if it's less than 50%, it's okay. Now, they are starting to say they need to have better than 30%, or all the way to 15%. Even down to 10%. It's all about leading away the heat from the components. We can do things with the process to reduce voiding, but the solder paste that is being used is very critical. It's very important that we edu- cate our customers. We have different pastes for different applications. We don't want to recom- mend, say, for automotive, a solder paste that we use for mobile phones. It's important to pick the right paste. It also depends on how the flux is formulated. Some give more voids, some less. But the reason for this is they are leading away the heat, and that's why we need to work on the voiding. Las Marias: Are there market trends that are causing the voids? Sjoberg: I think it's always been present. It's just that people haven't really been looking for it so much. Now, they are starting to see functional failures or overheating problems. I've been in FEATURE INTERVIEW

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