Joining method by Au-Sn brazing material

A method of joining members to be joined by use of an Au—Sn brazing material, said method comprising the steps of:

• applying a gold plating of 0.05 μm to 3 μm in thickness onto joint surfaces of the members to be joined, prior to a joining of the members;
• and performing a joining of the members, at a temperature ranging from 300° C. to 320° C., under an inert atmosphere of nitrogen, hydrogen or vacuum, with an Au—Sn brazing material consisting of an Sn content of 23 wt % to 25 wt % and the balance being Au;
• adjusting a thickness of the Au—Sn brazing material so that the following relationships hold among a composition and the thickness of the Au—Sn brazing material and the thickness of a gold plating;
• and
• adjusting the Sn content of a joint after joining to be 20.65 wt % to 23.5 wt %;
• thereby providing joints having either a eutectic structure or a structure containing an Sn rich phase in a eutectic structures:
• At 22 wt % of Sn
• y ≦ 0.0480 x
• At 23 wt % of Sn
• y ≦ 0.0825 x
• At 24 wt % of Sn
• 0.0152 x ≦ y ≦ 0.1163 x
• At 25 wt % of Sn
• 0.0452 x ≦ y ≦ 0.1492 x
• where x is the thickness of the brazing material in μm, and y is the thickness of the gold plating in μm, and where 0.05 ≦ y ≦ 3.