Abstract: A heat exchanger assembly is formed of spaced parallel headers connected by an array of spaced flat tubes each in a plane perpendicular to the headers. The header and tube material is clad with a brazing alloy which melts at a temperature slightly below the melting point of the base material. Sinuous metallic ribbons fill the spaces between the flat tubes. The assembly is induction heated by a low frequency alternating magnetic field having its flux lines extending transversely of the tubes and headers and at oblique angles thereto, the angles being selected to cause equal heating thereof for obtaining a uniform temperature throughout the assembly to effect the melting of the alloy and the brazing of the joints. Heat panels heated by the magnetic field to a temperature near that of the assembly are placed opposite outer surfaces of the assembly as required to avoid a radiation loss which would cause a significant temperature differential.