Various embodiments include a solder preform for establishing a diffusion solder connection comprising: a microstructure including a solder material and a metallic material; a first joining surface for a first joining partner and a second joining surface for a second joining partner; and a diffusion zone comprising an intermetallic compound of at least some of the solder material and at least some of the metallic material. The first joining surface and the second joining surface include at least some solder material.

A brazing sheet brazing suitable for brazing performed in an inert gas atmosphere or in a vacuum without using a flux has a three-layer composition. An aluminum alloy core material contains Mg: 1.3 mass % or less. An aluminum alloy intermediate material is layered on the core material and contains Mg: 0.40-6.0 mass %. An aluminum alloy filler material is layered on the intermediate material and contains Si: 6.0-13.0 mass %, Bi: 0.0040-0.070 mass %, and Mg: 0.050-0.10 mass %.

An object of the present invention is to provide an electrically conductive paste having excellent bonding strength when bonded to an electronic substrate and the like, a laminated body, and a method for bonding a Cu substrate or Cu electrode to an electrical conductor. An electrically conductive paste comprising: a flake-like silver powder A having a particle size in the range of 1 μm or more and 15 μm or less and having a median diameter D50 of 2 μm or more and 5 μm or less; a silver powder B having a particle size in the range of 25 μm or more and 100 μm or less and having a median diameter D50 of 30 μm or more and 40 μm or less; a silver powder C having a particle size in the range of 10 nm or more and 190 nm or less and having a median diameter D50 of 50 nm or more and 150 nm or less; and a solvent, wherein the content of the silver powder C is more than 5.0 parts by mass and less than 90.0 parts by mass based on 100 parts by mass in total of the flake-like silver powder A, the silver powder B, and the silver powder C.

A novel spot welding method for steel sheets and an aluminum alloy sheet, includes stacked sheet materials from a pair of opposing electrodes to join the sheet materials by resistance heating. The pair of opposing electrodes are in pressure contact with both outer surfaces of the sheet sets. The sheet sets include at least a first and second steel sheet, and an aluminum alloy sheet stacked in this order. A first energization step forms a molten pool between facing surfaces of the first and second steel sheets without melting the aluminum alloy sheet. A second energization step causes a melting reaction between facing surfaces of the second steel sheet and the aluminum alloy sheet. The first and second steel sheets are joined via a first nugget. The second steel sheet and the aluminum alloy sheet are joined via a second nugget including an intermetallic compound generated by the melting reaction.

Brazing strip or sheet comprising: a core layer made of aluminum alloy; a brazing layer made of aluminum alloy, clad on at least one face of the core layer; optionally an intermediate layer made of aluminum alloy, clad on at least one face either between the core layer and the brazing layer or the core layer without any other layer on top; characterized in that the brazing layer alloy comprises, in mass percentages:
from 7 to 13% Si, at most 0.8% Fe, at most 0.45% Cu, at most 0.20% Mn, at most 0.15% Mg, at most 0.20% Zn, at most 0.20% Ti, at most 0.04% Bi, from 0.01 to 0.10% Y, from 0.01 to 0.10% Sn, remainder aluminum and impurities.

An aluminum alloy for flux-free brazing provided for brazing performed via an Al-Si-based brazing material without a flux in a non-oxidizing atmosphere without depressurization, includes: by mass %, 0.01% to 2.0% of Mg; and 0.005% to 1.5% of Bi, wherein in the aluminum alloy, there are more than 10 Mg-Bi-based compounds having a diameter of 0.01 μm or more and less than 5.0 μm in terms of equivalent circle diameter per 10,000-μm.sup.2 visual field and there are less than 2 Mg-Bi-based compounds having a diameter of 5.0 μm or more per 10,000-μm.sup.2 visual field in a cross section parallel to a rolling direction, and in the aluminum alloy, there are less than 5 Bi particles having a diameter of 5.0 μm or more in terms of equivalent circle diameter per 10,000-μm.sup.2 visual field in the cross section parallel to the rolling direction.

An aluminum brazing sheet has a multilayer structure of two or more layers of at least a core material and a brazing material, wherein an Al—Si—Mg—Bi-based brazing material containing, by mass %, 0.01% to 2.0% of Mg, 1.5% to 14.0% of Si, and 0.005% to 1.5% of Bi is clad on one surface or both surfaces of the core material to be located at an outermost surface of the aluminum brazing sheet, in the Al—Si—Mg—Bi based brazing material, there are more than 10 Mg—Bi-based compounds having a diameter of 0.01 μm or more and less than 5.0 μm when observed in a surface layer plane direction and there are less than 2 Mg—Bi-based compounds having a diameter of 5.0 μm or more, and in the brazing material, there are less than 5 Bi particles having a diameter of 5.0 μm or more when observed in the surface layer plane direction.

An aluminum alloy brazing sheet used for brazing in an inert gas atmosphere without using a flux includes an intermediate material and a brazing material cladded onto at least one side surface of a core material in this order from the core material side. An oxide is formed on a surface of the aluminum alloy brazing sheet by brazing heating, the oxide including any one or two or more of Mg, Li, and Ca and having a volume change ratio of 0.990 or less to a surface oxide film formed before brazing heating, and an atomic molar ratio of Mg, Li, and Ca to Al in the oxide formed on the surface of the aluminum alloy brazing sheet before brazing heating is 0.5 or less. The present invention provides an aluminum alloy brazing sheet having excellent brazability in brazing in an inert gas atmosphere without using a flux, and a method for manufacturing the same.

A flux-free brazing aluminum alloy brazing sheet includes: a core material formed of aluminum alloy comprising Si of 0.50 to 0.90 mass %, Cu of 0.30 to 2.50 mass %, and Mn of 1.40 to 1.80 mass %, with a Mg content limited to 0.05 mass % or less, and with the balance being Al and inevitable impurities; an intermediate material being formed of aluminum alloy comprising Mg of 0.40 to 1.00 mass %, and Zn of 2.00 to 6.00 mass %, with the balance being Al and inevitable impurities; and a brazing material being formed of aluminum alloy comprising Si of 6.00 to 13.00 mass %, Mg of 0.05 to 0.40 mass %, and Bi of 0.010 to 0.050 mass %, with the balance being Al and inevitable impurities.

An object of the present invention is to provide an electrically conductive paste having excellent bonding strength when bonded to an electronic substrate and the like, a laminated body, and a method for bonding a Cu substrate or Cu electrode to an electrical conductor.

An electrically conductive paste comprising: a flake-like silver powder A having a particle size in the range of 1 μm or more and 15 μm or less and having a median diameter D50 of 2 μm or more and 5 μm or less; a silver powder B having a particle size in the range of 25 μm or more and 100 μm or less and having a median diameter D50 of 30 μm or more and 40 μm or less; a silver powder C having a particle size in the range of 10 nm or more and 190 nm or less and having a median diameter D50 of 50 nm or more and 150 nm or less; and a solvent, wherein the content of the silver powder C is more than 5.0 parts by mass and less than 90.0 parts by mass based on 100 parts by mass in total of the flake-like silver powder A, the silver powder B, and the silver powder C.