Abstract: Reflow-soldering of electronic components with differing heat capacities onto electronic circuit boards is accomplished by conveying the printed circuit board assemblies through a preheating chamber and a soldering chamber by means of conveyors operating at independently controlled speeds. To ensure that solder for components of large heat capacity is properly melted and smaller heat capacity components are not overheated, the circuit board assembly and components are advanced through the heating chamber at a rate of speed sufficient to allow the larger heat capacity components to just attain a preheat temperature. The assembly is subsequently conveyed through the soldering chamber at a rate of speed sufficient to just finish melting the solder for the larger heat capacity components as the assembly reaches the end of the soldering chamber. The ambient temperature within the soldering chamber is maintained at approximately 170.degree. C.