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54 SMT Magazine • August 2017 Flux-coated preforms are also increasing- ly being utilized as part of a voiding mitiga- tion strategy for certain die attach and bottom termination component (BTC) soldering ap- plications where thermal management is crit- ical. Void reduction in these joints means in- creased thermal conduction away from the die resulting in better die performance and longer lifetimes. Recent studies have shown that flux coated preforms used in conjunction with sol- der paste can give voiding levels below 5% on BTC components¹. In some die attach applica- tions, flux coated preforms can be used in con- junction with dispensed paste flux, totally elim- inating the need to print solder paste. Pick and place equipment is also now available on the market where dispensing of solder paste or flux material and component mounting can be al- ternately performed. This means that no sepa- rate dispensing equipment would be needed for such a process. In the case of die attach and BTC solder- ing applications, the drivers leading to pro- cess elimination are improved product reliabil- ity and improved assembly process yields, but these are only made possible due to the materi- als and process development work done by sol- der materials suppliers. SMT References 1. Lifton, Anna; Sidone, Jerry; Salerno, Paul; Khaselev, Oscar; Marzi, Mike;. s.l. Void Reduction Strategy for Bottom Termination Components (BTC) Using Flux Coated Preforms. SMTAi 2017. Westin Bent is a senior process engineer, R&D, at Alpha Assembly Solutions. PROCESS STEP ELIMINATION by Neha Agarwal, MARKETSANDMARKETS The acousto-optic (AO) methods of optical beams work on the principle of light diffraction of ultrasonic waves in crystals. These methods of modulation of optical beams have several uses in optics, spectroscopy, and laser technology. AO devices are suitable for various laser appli- cations in scientific research and the medical field for scientific purposes. They are used in barcode scanners, three-dimensional holography, micros- copy, spectroscopy, and laser-based medical diag- nostics and surgery. For spectroscopy, lasers can be used to make extremely sensitive detectors for various molecules, which can measure molecular concentrations up to parts per trillion (ppt) level. AO devices are also used in laser microscopy applications. AO tunable filters (AOTF), on the oth- er hand, are used in fluo- rescence spectroscopy and medical applications, which can access wavelengths from 0.4 µm to 5 µm (up to 25 mm). The demand for AO devices has increased due to the research conducted in various fields such as imaging cytometry, photoacoustic imaging, opti- cal coherence tomography, and multiphoton mi- croscopy for biomedical imaging and scanning applications. Also, using AO devices for control- ling laser beams for cutting materials enables the manufacturing of miniature components such as stents and surgical tools at micron tolerances. Furthermore, scientists are also using acousto- optic devices with laser technology for research in areas such as femtosecond micromachining, two- photon polymerization, and semiconductor me- trology. In the life science and scientific research segments, various acousto-optic devices such as modulators, deflectors, and tunable filters are widely used to modulate the frequency and inten- sity of laser beams for laser scanning applications. Despite strong demand for AO devices, how- ever, a significant challenge for the market is the high initial cost and the increasing R&D expenses on this technology. Acousto-Optic Devices: Finding New Horizons Neha Agarwal

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