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JULY 2018 I SMT007 MAGAZINE 75 Splash back is most commonly due to the wave height being too high or excessive turbulence in the wave. About 95% of applica- tions, if designed appropriately, can be soldered with laminar flow only and is recommended to help avoid occurrences. Best practice is to utilize tools such as the Fluxometer and WaveRIDER to check for parallel- ism and proper flux optimization to minimize such occurrences. Tooling Considerations Areas of entrapment in the wave pallet can also contribute to solder balls. Reviewing pallet designs for solder flow to ensure there is sufficient flow channels or vents to allow outgassing during soldering can help minimize the occurrences of solder balls and spatter. Icicles, Flags and Excessive Solder Icicles and flags (horns) and excessive solder occur when a PCB passing through a solder- ing process either collects too much solder or develops an undesirable protrusion of solder from the joint. The most common contributor is process. Process Considerations By far, the most common reason is the wave solder pot temperature is too low or there is insufficient dwell on the solder pot. Best prac- tice of 3–5 seconds of dwell is recommended for a proper joint formation. Tools such as oven- riders can provide an indication of solder pot temperature drift. It is always recommended to measure the solder pot temperature regularly to ensure proper temperature. Wave solder pot temperature readings from the machine do not always translate to actual and must be moni- tored. Defect prevention is best performed through applying best practices through formalized design reviews and implementing process controls around key wave parameters such as solder pot temperature, pre-heat, dwell, paral- lelism and flux optimization. Activities such as design for manufactur- ing (DFM) or design for assembly (DFA) can save significant time in applying design rules to ensure PCB design considerations, thermal requirements, manufacturing compatibility and related contributors are identified early in the design cycle where changes can be imple- mented at a fraction of the cost. It is important to align with strategic manu- facturing partners early on to provide relevant design feedback on all aspects on the design as the design decisions made early on can affect the long-term viability and cost of the product for the total lifecycle. SMT007 Brian Morrison, VP of Engineering for Vexos, is directly responsible for process, test, and development, focused on new customer and new product introduction. Morrison aided in the development of the company's corporate technology roadmap, systems and processes, value engineering, environmental management, and manufacturing initiatives to drive lower cost, flexible solutions, and manufacturing innovation. Figure 4: Vexos Production Lines.

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