This paper describes a method of flux-flee brazing aluminum in an inert gas atmosphere using unique brazing sheets (EB sheets) with thin aluminum layers several micrometers thick on Al–Si–Mg filler metal. The effects of thin aluminum layers and the composition of filler metal of the EB sheets were investigated by joint clearance filling test. The EB sheets showed higher brazeability than that of conventional brazing sheets without the thin aluminum layers. The increase of magnesium content in filler metal improved brazeability. The addition of bismuth to filler metal also showed the positive effect. The behavior of the oxide film of brazing sheets during brazing was investigated by auger electron spectroscopy (AES) analysis. The oxide film of the conventional brazing sheets thickened during brazing heating. Contrarily, the oxide film of the EB sheets got thin at a temperature 848 to 863 K. The brazing mechanism of the EB sheets has been discussed based on this result.
