FLUX-FREE SOLDERING BLAZING SHEET, FLUX-FREE SOLDERING METHOD AND HEAT EXCHANGER MANUFACTURING METHOD

摘要

PROBLEM TO BE SOLVED: To provide a flux-free, aluminum member soldering blazing sheet, and a soldering method.SOLUTION: Provided is a flux-free soldering sheet 1, in which one face or both faces of a core material 3 are clad with an outermost surface soldering material layer 3b of Al-Si based alloy containing 2-13 mass% Si and an intermediate soldering layer 3a of Al-Si-Mg based alloy containing 4-13 mass% Si and 0.1-5.0 mass% Mg. Si particles contained in the outermost surface soldering material layer 3b, in surface layer direction observation of the soldering material layer, has a numeral percentage of 10% or more in the number of diameters of 1.75 μm or more, out of diameters of equivalent circle diameter of 0.8 μm or more, and the number of Si particles of an equivalent circle diameter of 0.25 μm or more contained in the intermediate layer 3a, in cros-sectional observation, is less than 3,000 pcs. per 10,000 μm. A flux-free method for junction of aluminum members in a no-oxidative gas atmosphere under a normal pressure with an oxygen concentration of 100 ppm or less using the flux-free soldering sheet 1 is also provided.SELECTED DRAWING: Figure 1