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58 SMT Magazine • March 2016 air Knife cleaning An air knife is used for removing excess flux by blowing it off the bottom of the board before entering the wave. It is usually used with foam fluxing methods but can also be used with spray fluxing. • Pros: Eliminates most post-wave cleaning; returns excess back to the flux reservoir to conserve material • Cons: Adds a little cost but saves on post-wave manual cleaning • Typical cost range: Usually runs less than $1,000 as an add-on to a wave solder system recirculating cleaning System This is a cleaning system for finger-type or board edge conveyors. It sprays a solution onto the conveyor just before new boards are loaded. The system includes an alcohol detergent solu- tion along with brushes. • Pros: Reduces maintenance labor and downtime caused by flux residue buildup. Flux is a fairly sticky substance and can cause production problems if not dealt with regularly. • Typical cost range: Usually adds between $1,000–2,000 to a wave machine purchase. Inerting Systems Inerting systems are used to introduce ni- trogen during the soldering process. Nitrogen is contained within the solder pot by a hood, to reduce oxidation in the pot and in the critical moments while soldering the boards. Nitrogen inerting is recommended for lead-free solder, which will oxidize rather quickly otherwise and can adversely affect joint quality. Nitrogen is by far the most commonly used gas in an SMT ap- plication. • Pros: Ensures high quality joints to meet IPC standards when required • Cons: Adds significant cost • Typical cost range: Can add up to $4,000 to a wave solder system rollout Solder Pot On larger wave solder systems, the solder pot itself, when full, can weigh up to several hun- dred pounds. A rollout option simplifies main- SElECtIng a wavE SoldErIng SyStEM, Part 4 Figure 1: Flux air knife. Figure 3: Finger cleaner. Figure 2: Diagram of flux air knife.