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12 SMT Magazine • March 2016 by mB allen KIC ThErMAl A clear industry trend now spreading be- yond the traditional North American and Euro- pean markets is characterized by short produc- tion runs and frequent production line change- over. Improved technologies for line balancing, production planning, smart feeders, MES and more are being used more effectively to allow for faster production line changeover and less downtime. One obstacle tends to be the reflow oven. Having a $2 million production line sitting for 30+ minutes while waiting for a $40,000+ oven to stabilize on a new recipe will wreak havoc on profits. The goal should be instant oven changeover, and that goal is achievable in the majority of applications. First, a few observations on the purpose of a reflow oven. I always ask process engineers the following question: What is the main job per- formed by the reflow oven? The answers tend to be to melt solder, solder the components onto the board and create a strong solder joint. All of that is true, but there is more to it. Clearly, we do not want a strong solder joint that cracked the component in order to achieve it. So the re- flow oven needs to solder the assembly within the tolerances/process window set by the rel- evant solder paste, components and substrate. Instant Reflow Oven Changeover in a World of Short Production Runs fEatu rE Figure 1 (above): There are predictive software that are fast enough to do exhaustive search on the recipes, and to select the optimal oven setup that will produce an acceptable profile for a wide range of different assemblies.