Provided is a solder paste which uses a conventional flux, and for which long-term preservation is made possible and an easy preservation method can be realized by suppressing changes in the viscosity of the paste over time. This solder paste is provided with a solder powder, a zirconium oxide powder, and a flux, and changes in the viscosity of the paste over time are suppressed.

Provided are a solder alloy and a solder joint which have high tensile strength, can suppress Ni leaching and can suppress generation of voids at a bonded interface. The solder alloy has an alloy composition consisting of, by mass %, Ag: 1.0 to 4.0%, Cu: 0.1 to 1.0%, Ni: 0.005 to 0.3%, Co: 0.003 to 0.1%, and Ge: 0.001 to 0.015% with the balance being Sn The alloy composition satisfies the following relation (1):

0.00030<(Ni/Co)×(1/Ag)×Ge<0.05   (1) Co, Ag, and Ge in the relation (1) each represent the contents (mass %) in the alloy composition.

A lead-free solder alloy comprising: from 2.5 to 5 wt. % silver; from 0.01 to 5 wt. % bismuth; from 1 to 7 wt. % antimony; from 0.01 to 2 wt. % copper; one or more of: up to 6 wt. % indium, up to 0.5 wt. % titanium, up to 0.5 wt. % germanium, up to 0.5 wt. % rare earths, up to 0.5 wt. % cobalt, up to 5.0 wt. % aluminium, up to 5.0 wt. % silicon, up to 0.5 wt. % manganese, up to 0.5 wt. % chromium, up to 0.5 wt. % iron, up to 0.5 wt. % phosphorus, up to 0.5 wt. % gold, up to 1 wt. % gallium, up to 0.5 wt. % tellurium, up to 0.5 wt. % selenium, up to 0.5 wt. % calcium, up to 0.5 wt. % vanadium, up to 0.5 wt. % molybdenum, up to 0.5 wt. % platinum, and up 0 to 0.5 wt. % magnesium; optionally up to 0.5 wt. % nickel; and the balance tin together with any unavoidable impurities.

Provided are a lead-free and antimony-free solder alloy, a solder ball, and a solder joint that have improved shear strength obtained by grain minuteness at a bonded interface and can suppress fusion failure. The lead-free and antimony-free solder alloy having an alloy composition consisting of, by mass%, 0.1 to 4.5% of Ag, 0.20 to 0.85% of Cu, 0.2 to 5.00% of Bi, 0.005 to 0.09% of Ni, and 0.0005 to 0.0090% of Ge with the balance being Sn, and the alloy composition satisfies the following relations (1) and (2): 0.013 ≤ (Ag + Cu + Ni + Bi) x Ge ≤ 0.027 (1), Sn x Cu x Ni ≤ 5.0 (2). Ag, Cu, Ni, Bi, Ge, and Sn in the relations (1) and (2) each represent the contents (mass%) in the alloy composition.

Provided are a lead-free and antimony-free solder alloy, a solder ball, and a solder joint, which have improved shear strength obtained by grain minuteness at a bonded interface and can suppress fusion failure. The lead-free and antimony-free solder alloy has an alloy composition consisting of, by mass %, 0.1 to 4.5% of Ag, 0.20 to 0.85% of Cu, 0.005 to 0.090% of Ni, and 0.0005 to 0.0090% of Ge with the balance being Sn, and the alloy composition satisfies the following relations (1) and (2): 0.006≤(Ag+Cu+Ni)×Ge<0.023 (1), (Sn/Cu)×(Ni×Ge)/(Ni +Ge)<0.89 (2). Ag, Cu, Ni, Ge, and Sn in the relations (1) and (2) each represent the contents (mass %) in the alloy composition.

Provided is a metal particle for adhesive paste. The metal particle may include a core including at least one metal; and a shell on at least one surface of the core and including at least one metal and nanoparticles. The metal particle may be a transient liquid phase particle and the at least one metal of the core may have a higher melting point than a melting point of the at least one metal of the shell. In addition, provided are a method of preparing the metal particle for adhesive paste, a composite bonding structure formed from the metal particle for adhesive paste, and a semiconductor device including the composite bonding structure.

Provided is a metal particle for adhesive paste. The metal particle may include a core including at least one metal; and a shell on at least one surface of the core and including at least one metal and nanoparticles. The metal particle may be a transient liquid phase particle and the at least one metal of the core may have a higher melting point than a melting point of the at least one metal of the shell. In addition, provided are a method of preparing the metal particle for adhesive paste, a composite bonding structure formed from the metal particle for adhesive paste, and a semiconductor device including the composite bonding structure.

Provided is a solder composition containing Sn. The composition comprises: 1.0% by mass or more and 5.0% by mass or less of Cu; 0.1% by mass or more and 0.5% by mass or less of Ni; and more than 0.01% by mass and 0.5% by mass or less of Ge.

Provided is a solder composition containing Sn. The composition comprises: 1.0% by mass or more and 5.0% by mass or less of Cu; 0.1% by mass or more and 0.5% by mass or less of Ni; and more than 0.01% by mass and 0.5% by mass or less of Ge.

A method of soldering includes providing a substrate having a first metal joining surface, providing a semiconductor die having a second metal joining surface, providing a solder preform having a first interface surface and a second interface surface, arranging the solder preform between the substrate and the semiconductor die such that the first interface surface faces the first metal joining surface and such that the second interface surface faces the second metal joining surface, and performing a mechanical pressure-free diffusion soldering process that forms a soldered joint between the substrate and the semiconductor die by melting the solder preform and forming intermetallic phases in the solder. One or both of the first interface surface and the second interface surface has a varying surface profile that creates voids between the solder preform and one or both of the substrate and the semiconductor die before the melting of the solder preform.