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November 2017 • The PCB Design Magazine 53 Shaughnessy: What trends are you seeing in HDI? Wu: The emergence of HDI technology is re- sponsible for the recent growth of the PCB industry. HDI allows the PCB to be populated with denser BGA and QFP parts. With the de- velopment of high-speed serial bus technology, signal transmission rates continue to increase, and the impact of the parasitic parameters has drawn more and more attention. Engineers are studying ways to reduce the effects of parasit- ics in vias. Due to the design requirements of vias-in-pads, you can reduce the parasitic sur- face device parameters. Therefore, HDI is also gradually applied to high-speed PCB designs to avoid having high-speed signal stubs that are too long. We believe that line width and spac- ing will transition from the current mainstream of 3/3 to 2/2 in the future. The current main- stream HDI stack-up, 2 + n +2, will transition to stack-ups of any order for HDI carrier boards. The traditional market for HDI boards has been mobile phones. At present, nearly all this generation's intelligent machines use HDI for the motherboards, and the expansion rate has been improving at a slow rate. However, HDI may be replaced by higher process-level carrier boards in some of the next generation's mod- els. Now that the market is being saturated with smartphones, market growth will continue to slow down. In addition to the advantages of high wir- ing density and high signal integration, HDI also provides better electrical performance and signal integrity in data communications, so fu- ture opportunities will be emerging in automo- tive electronics and communications base sta- tions. In the automotive electronics industry, modules for navigation, Bluetooth communi- cation and data require the use of HDI boards. Car electronics, communications base stations, medical equipment and other emerging prod- uct areas continue to rise in terms of incremen- tal growth rate, far beyond the traditional 3C products. This area is projected to overtake the smartphone market as the main growth point for HDI technology. Shaughnessy: Thank you for your time, Bruce. Wu: Thank you, Andy. PCBDESIGN EDADOC DISCUSSES HDI DESIGN AND MANUFACTURING Fraunhofer researchers have developed a new technology that enables biochemical reactions to be monitored from start to finish at the single- molecule level. All that is needed to perform such tests are tiny sample droplets of the re- agent solution. "The ingenious feature of our system is that for the first time we can observe the details of how the two droplets interact at the single-molecule level—thus allowing us to monitor the entire chain of events," says Lorenz Sparrenberg from the Fraunhofer Institute for Applied Information Technology FIT. The electrowetting system devel- oped by Sparrenberg and his team con- sists of an array of electrodes on a chip, hence the name electrowetting-on-dielectric (EWOD) sys- tem. Depending on the switching state of the elec- trodes, the droplets can be manipulated to move further apart or closer together, and be brought together to merge in a predefined spot. This process is monitored using a confocal micro- scope, enabling high-resolution measurements to be recorded. "Until now, we have concentrated on proof-of-concept, demonstrating that the combination of our EWOD de- vice with confocal microscopy is capable of providing information at the single-molecule level. We are now looking for industry partners to help us develop concrete applications," says Sparrenberg. A Powerful Duo