Reflow oven

A reflow oven comprising:

• a furnace chamber;
• several heating units disposed side-by-side in the furnace chamber along a first direction, the several heating units comprising at least one negative pressure heating unit, each negative pressure heating unit comprising a negative pressure heating unit upper portion and a negative pressure heating unit lower portion;
• and
• a delivery channel extending through the plurality of heating units along the first direction and comprising a plurality of delivery channel sub-regions respectively located between the negative pressure heating unit upper portion and the negative pressure heating unit lower portion of each negative pressure heating unit, the delivery channel sub-regions comprises in a second direction perpendicular to the first direction a middle region for passing a processing element through and side regions located on opposite sides of the middle region;
• wherein the negative pressure heating unit upper portion comprises an upper fan, an upper suction channel, and an upper exhaust channel, the upper fan having an upper fan suction port and an upper fan exhaust port;
• the negative pressure heating unit lower portion comprises a lower fan, a lower suction channel, and a lower exhaust channel, the lower fan having a lower fan suction port and a lower fan exhaust port;
• wherein the upper suction channel, the upper exhaust channel, the lower suction channel, and the lower exhaust channel are configured such that gas discharged from the lower fan exhaust port flows through the lower exhaust channel and blows to the middle region of the delivery channel sub-region, then is sucked by the upper suction channel and delivered to the upper fan suction port, and the gas discharged from the upper fan exhaust port sequentially flows through the upper exhaust channel, the side regions of the delivery channel sub-region and the lower suction channel, and is then received by the lower fan suction port.