CPC B23K 35/262 (2013.01) [B23K 35/025 (2013.01); B23K 35/264 (2013.01); C22C 12/00 (2013.01); C22C 13/02 (2013.01); H05K 3/3457 (2013.01); B23K 2101/36 (2018.08)] | 4 Claims |
1. A solder alloy having an alloy composition consisting of, by mass %, 31% to 59% of Bi, 0.3% to 1.0% of Cu, 0.01% to 0.06% of Ni, 0.0040% to less than 0.01% of As, optionally at least one of P and Ge in a total amount of 0.003% to 0.05%, 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 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.
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