Solder alloy, solder paste, solder ball, solder preform, solder joint, and circuit

A solder alloy having an alloy composition comprising, by mass %, 2.8% to 4% of Ag, 1.5% to 6% of Bi, 0.8% to 1.2% of Cu, 0.0040% to 0.025% of As, and a balance of Sn, the solder alloy comprising:

• an As-concentrated layer,
• wherein the presence of the As-concentrated layer is confirmed by determination criteria as below,
• wherein the As-concentrated layer is a region from an outermost surface of the solder alloy to a depth of 2×D1 (nm) in terms of SiO2, and
• wherein a thickness of the As-concentrated layer in terms of SiO2 is 0.5 to 8.0 nm,
• wherein the Determination Criteria comprises:
• selecting an arbitrary area of 700 μm×300 μm in three samples, each sample having a size of 5.0 mm×5.0 mm;
• performing an XPS analysis in combination with ion sputtering for each of three samples, for a total of three analyses where S1>S2 in all of the three analyses indicates that an As-concentrated layer has been formed, and where
• S1 is Integrated value of a detection intensity of As in a region from a depth of 0 to 2×D1 (nm) in terms of SiO2 in a chart of XPS analysis;
• S2 is Integrated value of a detection intensity of As in a region from a depth of 2×D1 to 4×D1 (nm) in terms of SiO2 in a chart of XPS analysis;
• D1 is Initial depth (nm) in terms of SiO2 at which a detection intensity of O atoms is ½ a maximum detection intensity (intensity at Do·max) in a portion deeper than the depth (Do·max (nm)) in terms of SiO2 at which a detection intensity of O atoms is a maximum in a chart of XPS analysis, and the depth in terms of SiO2 is calculated from the sputtering time using a sputter-etching rate of an SiO2 standard sample.