To provide a Ni ball having a low α dose and high sphericity even when it contains impurity elements other than Ni in certain amounts. The Ni ball contains an element U, a content thereof being 5 ppb or less, and an element Th, a content thereof being 5 ppb or less, wherein a purity of the Ni ball is 99.9% or more but 99.995% or less, an α dose thereof is 0.0200 cph/cm.sup.2 or less, a content of either Pb or Bi, or a total content of both Pb and Bi is 1 ppm or more, and a sphericity thereof is 0.90 or more, in order to prevent any software errors and reduce connection failure.

Provided is a flux for soldering that can suppress a crack in a flux residue even if the flux for soldering is exposed to a cooling and heating cycle at the highest temperature of 150° C. such as the inside of an engine room of automobiles for a long period of time, and a soldering paste composition including the flux for soldering. The flux for soldering includes a synthetic resin, an activator, an organic solvent, and a thixotropic agent, in which synthetic resin contains a triblock copolymer of methacrylic acid ester with acrylic acid ester configured of a linear alkyl moiety having 3 to 6 carbon atoms. In addition, a soldering paste composition including the flux for soldering is used.

A method of welding including: applying a flux having at least a majority weight percent boron to a surface of a superalloy base material; forming a weldment on the surface wherein boron is melted onto the surface and is incorporated into a resulting weld pool and heat affected zone, and wherein incipient melted inter-dendritic material resulting from presence of the boron is available to flow into a crack formed during cooling of the weldment; and heat treating the weldment to diffuse a remaining concentration of the boron in the weldment and heat affected zone to a desired value.

A secondary cell manufacturing method includes placing a current collector terminal on a plurality of laminated current collector foils from a lamination direction of the current collector foils. The current collector terminal has a first end portion, and a second end portion forming a cutout with the first end portion. The second end portion includes a base part, and a thin-walled part having a smaller thickness than the base part. The secondary cell manufacturing method includes welding the plurality of current collector foils to the current collector terminal by scanning the plurality of current collector foils disposed in the cutout with a laser beam along the first extension direction toward the second end portion while irradiating the plurality of current collector foils with the laser beam.

An object of the present invention is to provide a method for producing a conductive material that allows a low electric resistance to be generated, and that is obtained by using an inexpensive and stable conductive material composition containing no adhesive. The conductive material can be provided by a producing method that includes the step of sintering a first conductive material composition that contains silver particles having an average particle diameter (median diameter) of 0.1 μm to 15 μm, and a metal oxide, so as to obtain a conductive material. The conductive material can be provided also by a method that includes the step of sintering a second conductive material composition that contains silver particles having an average particle diameter (median diameter) of 0.1 μm to 15 μm in an atmosphere of oxygen or ozone, or ambient atmosphere, at a temperature in a range of 150° C. to 320° C., so as to obtain a conductive material.

A method for making a firmly-bonded connection involves a) providing an electronic component and a substrate having surfaces to be connected; b) applying a copper paste onto at least one of the surfaces and drying the layer of copper paste; c1) applying a solder agent onto the copper paste and arranging the component and the substrate in contact via the combination of copper paste and solder agent; or c2) arranging the component and the substrate in contact via the dried copper paste, and applying a solder agent next to the layer of dried copper paste; and d) soldering the arrangement. The copper paste contains (i) particles of copper, copper-rich copper/zinc alloy, and/or copper-rich copper/tin alloy containing a phosphorus fraction of 0 to ≦500 wt-ppm, (ii) solder particles which are tin, tin-rich tin/copper alloy, tin-rich tin/silver alloy, and/or tin-rich tin/copper/silver alloy, and (iii) vehicle.

A solder paste that contains or consists of (i) 10-30% by weight of at least one type of particles that each contain a phosphorus fraction of >0 to ≦500 wt-ppm and are selected from copper particles, copper-rich copper/zinc alloy particles, and copper-rich copper/tin alloy particles, (ii) 60-80% by weight of at least one type of particles selected from tin particles, tin-rich tin/copper alloy particles, tin-rich tin/silver alloy particles, and tin-rich tin/copper/silver alloy particles, and (iii) 3-30% by weight solder flux, in which the mean particle diameter of metallic particles (i) and (ii) is ≦15 μm.

A method for brazing is provided, in which an amorphous or partially amorphous brazing foil, having a composition with a metalloid content of 10 to 30 at. %, is arranged at a joining point of two or more parts. The brazing foil is in the form of a wound ring-shaped strip which has a short-circuited current path between at least two layers lying one on top of the other. The brazing foil inductively heated, melted and a brazed connection of the parts is produced.

A soldering alloy includes an alloy composition consisting of 13-22 mass % of In, 0.5-2.8 mass % of Ag, 0.5-5.0 mass % of Bi, 0.002-0.05 mass % of Ni, and a balance Sn. A soldering alloy, a soldering paste, a preform solder, a soldering ball, a wire solder, a resin flux cored solder and a solder joint, each of which is composed of the soldering alloy. An electronic circuit board and a multi-layer electronic circuit board joined by using the solder joint.

Provided is a solder alloy, a solder paste, a solder preform, and a solder joint which suppress chip cracking during cooling, improve the heat dissipation characteristics of the solder joint, and exhibit high joint strength at high temperatures.

The solder alloy has an alloy composition of, by mass: Sb: 9.0 to 33.0%; Ag: more than 4.0% and less than 11.0%; and Cu: more than 2.0% and less than 6.0%, with the balance of Sn.

Moreover, the solder paste, the solder preform, and the solder joint all contain said solder alloy.