Structure containing Sn layer or Sn alloy layer

A structure including an Sn layer or an Sn alloy layer, comprising:

• a substrate;
• the Sn layer or the Sn alloy layer formed above the substrate;
• and
• an under barrier single layer formed between the substrate and the Sn layer or the Sn alloy layer, wherein:
• the Sn layer or the Sn alloy layer is a surface layer of the structure,
• the under barrier single layer is formed on a surface of the substrate that is a bottom layer of the structure,
• the under barrier single layer and the Sn layer or the Sn alloy layer are successively formed, and
• the under barrier single layer is an Ni alloy single layer consisting of:
• Ni and at least one selected from the group consisting of W, Ir, Pt, Au, and Bi,
• wherein the substrate has an exposed lower surface and is either a metal substrate of Cu or Ni or is a non-metal substrate comprising a metal thin film of Cu or Ni or an alloy of Cu or Ni on a top surface of the non-metal substrate, and
• wherein the under barrier single layer is directly formed either on the top surface of the metal substrate or on a top surface of the metal thin film on the non-metal substrate and the Sn layer or the Sn alloy layer is directly formed on the under barrier single layer, such that when the structure is subjected to a heat treatment at 180° C. for 150 hours, a thickness of an intermetallic compound generated under the Sn layer or the Sn alloy layer is 88.1% or less of the thickness of an intermetallic compound generated for an otherwise identical structure having a Sn—Ag alloy layer as the surface layer and in which the under barrier single layer is formed of Ni alone, wherein the Ni alloy single layer has 75% to 95% Ni by mass.