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AUGUST 2019 I PCB007 MAGAZINE 55 The methods used to achieve these charac- teristics of water are beyond the scope of this series. Most resin and equipment suppliers rec- ommend (or require) the use of softened water for this final (and sometimes every) washing stage. The requirement for soft water implies that the incoming unused process water must be processed to remove the hardness (calcium and magnesium ions) before it can be used for the final rinse in an exchange column. PCB007 References 1. A. Stepinski, "21 st Century PCB Fab Factory Design, Which Eliminates Regional Cost Advantages," IPC APEX EXPO Proceedings, 2017. 2. C.F. Coombs Jr., Printed Circuits Handbook: Sixth Edi- tion, McGraw-Hill, 2008. 3. K.H. Dietz, "Probing the Limits of Dry-Film Resist," Printed Circuit Fabrication, Vol. 16, No. 6, June 1993, p. 24. 4. K.H. Dietz, "Fine-Line Imaging: Trends in Exposure and Development Technology," Printed Circuit Fabrication, Vol. 18, No. 10, October 1995, p. 32. Pete Moleux is a chemical, environmental, health, and safety engineering advisor who has served industrial clients and law and expert witness search firms since 1988. Happy Holden has worked in printed circuit technology since 1970 with Hewlett-Packard, NanYa/Westwood, Merix, Foxconn and Gentex. He is currently a contributing technical editor with I-Connect007. To read past columns or to contact Holden, click here. "The innovation lies in the advanced materials devel- opment using molecular beam epitaxy (MBE) to 'grow' the compound semiconductor crystal in an atom-by-atom re- gime. This particular material is rather complex and chal- lenging to synthesize as it combines four different atoms requiring a new MBE methodology," said Professor Huf- faker. "The Sêr Cymru MBE facility, partly funded by HE- FCW, is designed specifically to realize an entire family of challenging materials targeting future sensing solutions." Dr. Shiyu Xie, Sêr Cymru Cofund Fellow, said, "The re- sults we are reporting are significant as they operate in a very low-signal environment, at room temperature, and very importantly, are compatible with the current InP op- toelectronic platform used by most commercial communi- cation vendors. The APDs have a wide range of applications. In LIDAR, or 3D laser mapping, they are used to produce high-resolution maps with applications in geomorphology, seismology, and in the control and navigation of some autonomous cars. The findings can change the global field of research in APDs. The material developed can be a direct substi- tute in the current existing APDs, yielding a higher data transmission rate or enabling a much longer transmis- sion distance. (Source: Cardiff University) Cardiff University researchers have developed a com- pound semiconductor (CS) technology that can drive fu- ture high-speed data communications. A team from the Institute for Compound Semiconductors (ICS) worked with collaborators to innovate an ultrafast and highly sensitive avalanche photodiode (APD) that creates less electronic noise than its silicon rivals. A paper outlining the breakthrough in creating extreme- ly low excess noise and high sensitivity APDs is published in Nature Photonics. Cardiff researchers led by Sêr Cymru Professor Diana Huffaker, scientific director of ICS and Sêr Cymru Chair in Advanced Engineering and Materials, partnered with the University of Sheffield and the California NanoSystems Institute, University of California, Los Angeles (UCLA), to develop the technology. Cardiff Delivers Compound Semiconductor Breakthrough