Abstract: The invention relates to an oven for reflow soldering objects such as printed circuit boards. A temperature differential is established between the top and bottom surfaces of the board to allow gases liberated from solder paste within through-holes to escape, thereby preventing the formation of voids. The oven provides a flow of gas at a first temperature from an upper gas supplying means to the top side of the board. A flow of gas at a second temperature is directed at the bottom side of the board by a lower gas supplying means. According to one aspect of the invention, a portion of the gas supplied by the upper gas supplying means is captured by the lower gas supply means and is heated or cooled to the second temperature. According to another aspect of the invention, a number of pairs of independantly controllable upper and lower gas supplying means are arranged along a conveyor to provide a temperature profile to perform reflow soldering.