Dual air knife for hot air solder levelling

A dual air knife assembly for removing excess solder and leveling any remaining solder on a passing circuit board with a gas from a gas source in accordance with the present invention includes a first and second air knife. The first air knife has a first passage with a first inlet adapted to connect to the gas source and a first outlet adapted to be positioned adjacent the passing circuit board. The second air knife has a second passage with a second inlet connected to the gas source and a second outlet adapted to be positioned adjacent the passing circuit board. The first air knife is adapted to be positioned substantially perpendicular to the circuit board and the second air knife is adapted to be positioned at an angle less than 90 degrees and preferably between 20 and 60 degrees to the circuit board. The dual air knife assembly may include a spacer which separates the a first and second air knife and is recessed from the outlets of the a first and second air knife to create an expansion chamber. The distance the first and second outlets are from the passing circuit board and the temperature and pressure of the gas exiting from the a first and second air knife should all be substantially the same. Typically, the dual air knife assembly is used in a soldering system which includes a conveyor, a flux station, and a solder station. The dual air knife assembly is used in a process referred to as "hot air solder levelling" to remove excess solder and more evenly distribute any remaining solder. A pair of dual air knife assemblies may be used in another soldering system where excess solder is removed and any remaining solder is levelled on both sides of a circuit board.