The exposed metal tip of the strike end of an SMAW welding electrode is covered with a protective coating formed from a binder and metal particles. Because metal particles rather than graphite particles are used to provide electrical conductivity to this protective coating, flare-up of the arc when initially struck is eliminated substantially completely. In addition, the potential for weld porosity problems is also eliminated, because the metal particles of the inventive electrode do not produce CO.sub.2 as a reaction by-product which can ultimately lead to improper welding technique.

Undercooled liquid metallic core-shell particles, whose core is stable against solidification at ambient conditions, i.e. under near ambient temperature and pressure conditions, are used to join or repair metallic non-particulate components. The undercooled-shell particles in the form of nano-size or micro-size particles comprise an undercooled stable liquid metallic core encapsulated inside an outer shell, which can comprise an oxide or other stabilizer shell typically formed in-situ on the undercooled liquid metallic core. The shell is ruptured to release the liquid phase core material to join or repair a component(s).

The present invention relates to a solder paste containing solder powder and a flux, wherein the solder powder is a lead-free solder alloy having a solidus temperature of 150? C. or less, the flux contains: a rosin; a solvent; a thixotropic agent; and an organic acid and an imidazole as an activator, the organic acid includes one or more kinds of dicarboxylic acids having 4 to 6 carbon atoms, and the imidazole includes one or more kinds among imidazole compounds having 3 to 6 carbon atoms and derivatives thereof.

A lead-free solder alloy includes bismuth (Bi), content of which is equal to or greater than 56 wt % and equal to or less than 57.5 wt %, indium (In), content of which is equal to or greater than 0.05 wt % and equal to or less than 1.0 wt %, and the balance of tin (Sn) and another unavoidable impurity. The lead-free solder alloy of the disclosure may enable bonding with improved ductility and thermal shock reliability while not having a large melting point change compared to an Sn-58Bi alloy.

An object of the invention is to provide a lead-free solder for die bonding having a high heat resistance temperature and an improved wetting property. Provided are a solder alloy for die bonding which contains 0.05% by mass to 3.0% by mass of antimony and the remainder consisting of bismuth and inevitable impurities, and a solder alloy for die bonding which contains 0.01% by mass to 2.0% by mass of germanium and the remainder consisting of bismuth and inevitable impurities.

A bonding sheet according to the present invention contains a matrix resin; solder particles; and a fluxing agent. In the bonding sheet, the solder particles are dispersed in the matrix resin, and the fluxing agent is unevenly distributed around the solder particles in the matrix resin. The method for producing the bonding sheet of the present invention includes a first step of dissolving a fluxing agent in a first solvent to prepare a fluxing agent solution; a second step of mixing a second solvent, a matrix resin component, solder particles, and the fluxing agent solution to prepare a mixed composition; and a third step of applying the mixed composition onto a substrate to form a coated film, and then drying the coated film to form a bonding sheet.

A solder wire composition may include 85 to 95 weight percent bismuth, and at least 5 weight percent copper. The solder wire composition may have a diameter of less than about 1 millimeter, and an elongation at break of at least 20%.

A solder alloy includes 18 wt % to 28 wt % of indium, 44.5 wt % to 54.5 wt % of bismuth, greater than 0 wt % and not more than 1.45 wt % of zirconium, and the balance being tin, based on 100 wt % of the solder alloy.

A solder paste consists of an amount of a first solder alloy powder between 60 wt % to 92 wt %; an amount of a second solder alloy powder greater than 0 wt % and less than 12 wt %; and a flux; wherein the first solder alloy powder comprises a first solder alloy that has a solidus temperature above 260 C.; and wherein the second solder alloy powder comprises a second solder alloy that has a solidus temperature that is less than 250 C.

Certain examples disclosed herein are directed to materials that are designed for use in interconnects of electrical devices such as, for example, printed circuit boards and solar cells. In certain examples, a two-step solder may be used to reduce stresses on the materials used in the production of the electrical devices.