The theoretical part of diploma thesis „Selection of a suitable type of flux for wave soldering”, is devoted to problematic of fluxes, flux residues and wave soldering. It introduces reader with requirements of company HC electronics and with selection of a suitable types of fluxes for testing. It also contains theoretical comparison and design of flux testing methodologies. The practical part of the diploma thesis is focused on the selection of a suitable flux for the company HC electronics by performing practical tests according to the previously proposed methodologies, which include wetting balance test method, surface insulation resistance measurement, copper mirror test, soldering test of PCB and ROSE method