Provided are: a resin composition for soldering use, which has excellent compatibility with a rosin-based resin and excellent temperature cycle reliability and is therefore suitable for a flux for soldering use; and a soldering composition and a flux cored solder, in each of which the resin composition for soldering use is used. The resin composition for soldering use comprises: an acrylic resin having a number average molecular weight of 500 or more and less than 2000 as determined by mass spectrometry using a time-of-flight mass spectrometer; and a rosin-based resin, a polyethylene-based resin or a polypropylene-based resin. Alternatively, the resin composition for soldering use comprises: an acrylic resin having a weight average molecular weight of 500 or more and less than 2000 as determined by mass spectrometry using a time-of-flight mass spectrometer; and a rosin-based resin, a polyethylene-based resin or a polypropylene-based resin.

Solder pastes comprise a high temperature solder powder, a low temperature solder powder and flux. The melting temperature of the low temperature solder powder is lower than that of the high temperature solder powder. The high temperature solder powder and the low temperature solder powder are both capable of wetting upon heating.

A flux containing 1 to 10 wt % of an organic sulfonic acid activator, 10 to 40 wt % of a high-molecular-weight nonionic surfactant that is a nonionic surfactant having a mass-average molecular weight Mw of more than 1200 and 5 to 75 wt % of a low-molecular-weight nonionic surfactant that is a nonionic surfactant having a mass-average molecular weight Mw of 1200 or less, in which the content of the low-molecular-weight nonionic surfactant is equal to or larger than the content of the organic sulfonic acid activator. This flux contains no cationic surfactant or contains more than 0 wt % and 5 wt % or less of the cationic surfactant. A solder paste containing this flux and a Sn-based solder metal.

A solder includes a Sn alloy phase and a particle. The particle has a higher Young's modulus than the Sn alloy phase. The particle has a lower linear expansion coefficient than the Sn alloy phase. An electronic component includes a metal terminal joined thereto with the solder.

A solder product 20 includes: a lead-free solder part 21 containing tin as a main component and a metal element other than lead as a secondary component; and a carboxylic acid having 10 to 20 carbons, the carboxylic acid being mainly distributed over the surface of the solder product 20 to form a surface layer 22. The carboxylic acid is preferably a fatty acid having 12 to 16 carbons, and more preferably a palmitic acid.

A SnAgCuSb-based Pb-free solder alloy is disclosed. The disclosed solder alloy is particularly suitable for, but not limited to, producing solder joints, in the form of solder preforms, solder balls, solder powder, or solder paste (a mixture of solder powder and flux), for harsh environment electronics. An additive selected from 0.1-2.5 wt. % of Bi and/or 0.1-4.5 wt. % of In may be included in the solder alloy.

A lead-free solder alloy consisting essentially of: 32 mass % or more and 40 mass % or less of Bi; 0.1 mass % or more and 1.0 mass % or less of Sb; 0.1 mass % or more and 1.0 mass % or less of Cu; 0.001 parts by mass or more and 0.1 parts by mass or less of Ni; and a remainder of Sn with unavoidable impurities. The lead-free solder alloy further contains specific elements in amounts in predetermined ranges.

Photonic devices include a photonic assembly and a substrate coupled to the photonic assembly. The photonic assembly includes a photonic die and an optical device coupled to the photonic die with an adhesive to form an optical connection between the optical device and the photonic die. The photonic assembly is coupled to the photonic assembly by reflowing a plurality of solder connections at temperature that is less than a cure temperature of the adhesive.

A conductive path can be formed using metal material coated with a layer that is controllably activated to release the metal material downhole in the wellbore. The conductive path can be used to communicate signals or power downhole in the wellbore.

A resin flux solder paste includes a solder powder, and a flux, in which the flux contains at least an epoxy resin, a curing agent, a curing accelerator, and an activator, the epoxy resin contains 10% to 90% by weight of one or more of a biphenyl aralkyl type epoxy resin, a naphthalene type epoxy resin, and a dicyclopentadiene type epoxy resin, having an epoxy equivalent of 200 to 400, with respect to a total amount of the epoxy resin, and the curing agent contains 30% to 95% by weight of a biphenyl aralkyl phenol resin having a hydroxyl group equivalent of 150 to 350 with respect to a total amount of the curing agent, and 5% to 70% by weight of a phenol novolac resin having an allyl group having a hydroxyl group equivalent of 100 to 200 with respect to the total amount of the curing agent.