I am unfamiliar with an additive called ao100c, but in general solder additives are intended to minimize dross formation from the reaction of tin with oxygen in a solder wave.There is a surfactant type additive that will float over the solder, forming an oxygen barrier and actually eliminating dross formed by the wave through a chemical reaction. There are also nitrogen systems to keep oxygen away from the solder. The advantage of eliminating dross is cleaner, more consistent solder joints and minimizing the waste of solder. The biggest disadvantage of this surfactant material is that the surfactant is a high cost material that also needs to be replenished as it is consumed.
Sn100c is sometimes used as a lead-free alternative for wave solder equipment. There is the initial solder placed in the pot, and as it processes joints, a certain amount of copper will be dissolved in the solder wave. There is another solder called Sn100ce that is used to replace the amount of solder that is carried off on the processed boards which will keep the copper content lower. If the copper content creeps up, it will lead to bridging.
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