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SEPTEMBER 2020 I SMT007 MAGAZINE 39 layout. We have thermal challenges in terms of solderability that need to be addressed because, in the end, we need to get that Class 3 solder joint, every time. Holden: Up to what thickness of copper do you sometimes have to use on your inner layers? Steiner: Four ounces is a common inner layer for us. But on the external, we start with one- ounce foil, plate that two ounces, and plate heavy vias and heavy barrel plating. I often require double the normal via barrel plating. Instead of one mil, we're sometimes at two mils, and all of those things add up together to get us the thermal conduction performance that we need. Johnson: Any parting observations? Steiner: We're having success. The biggest thing that you need to do is write things down so that you can share that knowledge and point to a document that's legible. When the indus- try standards are lacking for your needs, cre- ate your own. I do that as needed, and these become CASCO standards. It's worth the effort. You reap benefits by doing things in manufac- turing the same ways, consistently. Johnson: Any team, any size should be follow- ing that practice. Thank you for your time. Steiner: Absolutely. SMT007 Light waves oscillate far faster than most sensors can respond. Essentially all commercial light sensors act like a microphone that can tell what a crowd of people saying but can't make out any of the individual words. Scientists and engineers have been devising clever techniques to sense the light field itself, not just the total energy it delivers. This is difficult because the required timing precision is so short—just a few femtoseconds. As a result, work has been limited to a few specialized research laboratories. What is needed is an approach that is compact, manu- facturable, and easy to use. MIT postdoc Yujia Yang and col- laborators at MIT, the University of California at Davis, the Deutsches Elektronen-Synchrotron, and the University of Hamburg in Ger- many, demonstrated a microchip with nanometer-length-scale cir- cuit elements that act like anten- nas to collect the electric field of light oscillating at nearly one qua- drillion times per second. The chip is small, self-contained, and requires only inexpensive elec- tronics for readout. "We see a wide range of new optical and electronic devices that could be based on this technology," says Karl Berggren, MIT professor of electrical engineering and co-author of the work. "For example, this technique could have a future impact on applications, such as determin- ing the distance to remote astronomical objects, optical clocks critical to GPS technology, and chemical analysis of gases." (Source: MIT News) Integrated Lightwave Electronics

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