Abstract: A solder reflow oven for the processing of ball grid array substrates bearing solder balls is described, comprising: input means for introducing substrates into the oven, a processing chamber within which the substrates are subject to a solder reflow process, and output means for discharging substrates from the oven for further processing or handling, and means for transferring the substrates through the processing chamber in a first direction towards the output means. The processing chamber comprises a plurality of heating and cooling zones arranged with a constant pitch in the first direction, and the transferring means is adapted to move the substrates in the first direction in stages, with each component moving a distance equal to the pitch between two zones in each stage, whereby the components are moved from zone to zone in stages.