Abstract: A solder reflow oven with horizontal cyclonic convection air flow for enhancing equalized heating of printed circuit boards conveyed therethrough. Air circulation apparatus can include a first air movement fan for urging air to move horizontally laterally from the first side wall of the oven toward the second side wall of the oven across and above printed circuit boards being conveyed therethrough. A second air fan is positioned below and laterally displaced from the conveying means for directing a second air stream below the first air stream and oppositely oriented in order to urge movement of heated air across the undersurface of the conveyor for enhancing equalization of heating of the printed circuits boards thereupon. Preferably, both blowers are oriented to move air approximately perpendicularly with respect to the direction of movement of the conveyed printed circuit boards in opposite respective directions thereabove and therebelow.