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68 PCB007 MAGAZINE I NOVEMBER 2018 Let's say you live in Phoenix, Arizona. You grab the kids in the morning and take them to school. Then, you pick them up, take them out to the soccer game, park the car in the sun, and when the soccer game is over, you turn the air conditioning up full blast and drive them off to an ice cream place. You take them in for some ice cream and a hamburger while the car sits in the sun and gets all hot. You come back out, throw on the AC on full blast again, drive to the grocery store—you see where I'm going with this. There's no longer a gentle one-per-day cy- cle; The cycles occur at an extremely rapid rate with multiple cycles—four, five, six, or seven— per day for the electronics inside the cabin of an automobile. It's not a smooth ramp rate; it's very jagged, which exercises the solder joints even more. What we've been able to show in our modeling work is that modest changes in the X and Y CTEs of the circuit board—for ex- ample, going from a 16 to a 13—can double the life of solder joints for certain BGA parts. Holden: Would you call this intuition a skill? Brown: It's to be aware that your intuition, for example, would realize that a modest change in X, Y, and CTE of a board wouldn't make all that much a difference in the life of a sol- der joint. In fact, it makes two times the dif- ference. For an infotainment automobile man- ufacturer, that could mean the difference be- tween meeting the requirements of the top au- tomotive customer and failing. Holden: I'm interested in the essential skills that you have to develop after college, or the things that they don't teach you in college but are still essential. If we step back into something more basic, how would you define the skill of intu- ition of the artistic part of engineering? Brown: I'll leave you with this final thought, which is rules versus tools. In the old days, we had design rules. We had a separate set of design rules for medical, avionics, industrial, automotive, and consumer products. Those worked very well when the change of pace was more sedate; today, with shrinking geom- etries and shorter development lifetimes, we need to make the transition from rules to tools. There's a variety of tools out there—our Sher- lock reliability physics modeling software is only one—but it's up to design engineers to know what rule and tool to apply under differ- ent circumstances. Holden: I think I've found another skill—rules versus tools. Matties: Thank you so much for spending time sharing your wisdom with us, Dock. We great- ly appreciate that. Brown: My pleasure. PCB007 neering by Alloying for Photonics" was recently featured in the journal Advanced Optical Materials. The research focused on combining experimen- tal and theoretical efforts to elucidate the alloyed ma- terial's electronic structure with direct implications for the optical behavior. According to the researchers, the insights gained enable one to tune the optical disper- sion and light-harvesting capability of these materials, which can outperform systems made of individual elements like gold. (Source: U.S. Army Research Laboratory) Scientists Dr. David Baker and Dr. Joshua McClure from the U.S. Army Research Laboratory (ARL)—in collabora- tion with Professor Marina Leite and Dr. Chen Gong at the University of Maryland and Professor Alexandre Rocha at the Universidade Estadual Paulista in Brazil—have devel- oped new designer materials with a broad range of capa- bilities to enhance the power of soldier devices used on the battlefield. Focused on the control of optical and plasmonic prop- erties of gold and silver alloys by changing alloy chemical composition, their research titled "Band Structure Engi- Army Research Paves the Way for Designer Materials

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