Soldering Technology for 3D PCB Assemblies with Microwave Heating

This paper is showing results from a joint research project "MICROFLOW", funded by the German Department for Education and Research (BMBF). Usual simultaneous reflow soldering processes like convection soldering or vapor phase soldering were optimized in the past for a minimum of temperature difference between small and large or heavy components on electronic assemblies. Especially the increasing demands for 3D PCB-modules, polymer electronics or electrical- optical assemblies require are further development of soldering processes. Such a process should allow a direct heating of the solder joints up to soldering temperature also for hidden structures and have to save sensitive components at the same time. Today this is possible only by application of sequential working selective soldering processes like hot bar soldering or laser soldering. But for a cost effective industrial application it is necessary to realize a selective and as well simultaneous soldering process, which is indeed not available at present.