Brazing sheet for flux-free brazing, method for flux-free brazing and method for manufacturing heat exchanger

A brazing sheet for flux-free brazing, comprising:

• an outermost surface brazing filler metal layer, consisting of an Al—Si-based alloy comprising 2 to 13% Si in mass %;
• and
• an intermediate brazing filler metal layer consisting of an Al—Si—Mg-based alloy containing 4 to 13% Si and 0.1 to 5.0% Mg in mass %,
• wherein the outermost surface brazing filler metal layer and the intermediate brazing filler metal layer are cladded on one or both sides of a core material,
• wherein, in the outermost surface brazing filler metal layer, a number of Si particles having a circle equivalent diameter of 1.75 μm or more is 10% or more of a number of Si particles having a circle equivalent diameter of 0.8 μm or more, as observed in a direction of a surface layer, and
• wherein the intermediate brazing filler metal layer contains less than 3000 per 10000 μm2 of Si particles having a circle equivalent diameter of 0.25 μm or more, as observed in a cross section of the intermediate brazing filler metal layer.