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74 SMT007 MAGAZINE I FEBRUARY 2018 demonstrate to management the result of his process improvement program. In calculating savings, the cost calculator considers the costs of rework, both simple and complex, the cost of wiper paper, and the cost of the solvent. Using the calculator, Crow could determine that the cost per board for simple rework was $2.30 per board compared with $34.50 per board for the cost of complex rework. In addition, the cost of paper was just $0.03 per board and the cost of solvent was $0.02 per board. By combining the rework savings along with the reduction in paper and solvent used due to less under-stencil wiping, the annual savings demonstrated from using the calcula- tor were considerable. In addition, as Crow's team was not changing wiper rolls as often, he was getting an extra 52 hours—over a full shift week—of additional production a year. For his investment, Crow produced an addi- tional 5,000 boards a year. With approximately 200 stencils at a cost of $25 an application, a total investment across all stencils is about $5,000—to save $395,000. Crow's management recognized the magnif- icent work by giving him a bonus and promo- tion. So, what can we say, but, 'Well done Jimmy!' Here's to a job well done. SMT007 Edward Hughes is the chairman and CEO Aculon. Ferroelectric materials have spontaneous electrical ordering that can be changed by applying an electric field. Where two domains of different polarizations meet, it is called a ferroelectric domain wall. These domain walls are promising for next-generation circuit elements due to their unusual electronic properties and because they can be formed, moved, and erased on demand. Scientists envision a transistor where the gate is a domain wall itself—and whether you can pass current through the domain wall is controlled by the charges in the domain wall. Now, scientists have found that they can reversibly switch domain walls between being resistive or conductive depending on the electric field they apply. Using atomic-resolution electron microscopy and spectroscopy, they found that the electrons that move to the wall were confined to just one to two repeating crys - talline unit cells in erbium manganite (ErMnO 3 ). When the polarizations of the two ferroelectric domains point at each other (head-to-head), there is nominally a buildup of positive charge at the domain wall. This positive charge was compensated by extra electrons that accu - mulated on the atoms within the domain wall. These elec- trons were stuck, shielding the local charges, and did not conduct. By applying an electric field, extra electrons flowed into the channel at the domain wall. When all the local charges were sufficiently shielded, the electrons in the channel were free to move within the domain wall, forming a 2-D conductive sheet. This conductive sheet could be used as a switch or transistor. The switch is "off" when current does not flow. Applying an electric field allows current to pass, turning the switch "on." This paves the way towards developing all-domain-wall electrical devices. Rewritable Wires Could Mean No More Obsolete Circuitry

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