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JUNE 2021 I SMT007 MAGAZINE 47 Discussion on possible solutions to the improper process condition setting defect e main area to focus on would be to review and adjust solder paste printing settings. Conclusions e case studies discussed gave examples of the causes of solder de-wetting which were based on inferior board plating/surface finish quality, contaminated plating, foreign object debris (FOD), damaged plating, and improper process condition setting. e causes of the defects were determined using a variety of anal- ysis techniques including optical microscopy, SEM/EDX, X-ray, and FT-IR analysis along with using company experience and knowl- edge with soldering defects, soldering materi- als and processes and background/experience with failure analysis work. SMT007 Kentaro Asai is manager of the Analytic Service Team, Research & Development Division, Koki Company Limited. Jasbir Bath is a support advisory engineer for Koki Solder America. Shantanu Joshi is an engineering sales manager for Koki Solder America. Roberto Segura is a general manager for Koki Solder America. When you save an image to your smartphone, those data are written onto tiny transistors that are electrically switched on or off in a pattern of "bits" to represent and encode that image. Most transistors today are made from silicon, an element that scien- tists have managed to switch at ever-smaller scales, enabling billions of bits, and therefore large libraries of images and other files, to be packed onto a sin- gle memory chip. But growing demand for data, and the means to store them, is driving scientists to search beyond silicon for materials that can push memory devices to higher densities, speeds, and security. Now MIT physicists have shown preliminary evi- dence that data might be stored as faster, denser, and more secure bits made from antiferromagnets. Antiferromagnetic, or AFM materials are the lesser-known cousins to ferromagnets, or conven- tional magnetic materi- als. Where the electrons in ferromagnets spin in syn- chrony—a property that allows a compass needle to point north, collectively following the Earth's mag- netic field—electrons in an antiferromagnet prefer the opposite spin to their neighbor, in an "antialign- ment" that effectively quenches magnetization even at the smallest scales. The absence of net magnetization in an antifer- romagnet makes it impervious to any external mag- netic field. If they were made into memory devices, antiferromagnetic bits could protect any encoded data from being magnetically erased. They could also be made into smaller transistors and packed in greater numbers per chip than traditional silicon. Now the MIT team has found that by doping extra electrons into an antifer- romagnetic material, they can turn its collective anti- aligned arrangement on and off, in a controllable way. They found this mag- netic transition is revers- ible, and sufficiently sharp, similar to switching a tran- sistor's state from 0 to 1. (Source: MIT News Office) Physicists Find Novel Way to Switch Antiferromagnetism On and Off

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