A flux containing 0.1 to 20 wt % of 2-hydroxyisobutyric acid as an activator, 10 to 60 wt % of a cationic surfactant and 5 to 60 wt % of a nonionic surfactant. A solder paste contains a flux containing 0.1 to 20 wt % of 2-hydroxyisobutyric acid as an activator, 10 to 60 wt % of a cationic surfactant, and 5 to 60 wt % of a nonionic surfactant and a metal powder.

The present invention employs a flux-coated ball 100 having a core part 110 and a shell part 120 with which the core part 110 is coated. The flux-coated ball 100 is characterized in that the core part 110 is made of a solder ball or a copper core ball, that the shell part 120 is made of a flux layer containing at least one selected from the group consisting of an activator and a resin component, and that an oxide film thickness in the flux-coated ball 100 is 3 nm or less.

Provided is a flux which is rosin-free and contains 50% by mass or more and 90% by mass or less of 2,4-diethyl-1,5-pentanediol, more than 0% by mass and less than 50% by mass of a solvent, 1% by mass or more and 15% by mass or less of an organic acid, wherein the total amount of the 2,4-diethyl-1,5-pentanediol and the solvent is 83% by mass or more and 99% by mass or less. This flux does not require washing with an organic detergent when transferred to solder balls is provided.

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.

Provided is flux that can be discharged using an inkjet method and that is capable of bonding to an adherend after application. This flux includes 5-50 mass % of a solid solvent having a melting point of 60° C. or less, 50-80 mass % of a solvent, 5-10 mass % of an organic acid, 10-30 mass % of an amine, and 0-5 mass % of a halide, the flux forming a liquid having a high viscosity of 5 Pa.Math.s or higher at 25° C., and forming a liquid having a low viscosity of 50 mPa.Math.s or less at 100° C.

A method for fabricating a semiconductor device with a heterogeneous solder joint includes: providing a semiconductor die; providing a coupled element; and soldering the semiconductor die to the coupled element with a first solder joint. The first solder joint includes: a solder material including a first metal composition; and a coating including a second metal composition, different from the first metal composition, the coating at least partially covering the solder material. The second metal composition has a greater stiffness and/or a higher melting point than the first metal composition.

Provided are: a flux that is for a solder paste and that can inhibit occurrence of voids; and a solder paste using the flux. This flux for a solder paste contains rosin, an imidazole compound, and a solvent, wherein the contained amount of the imidazole compound is 25-35 mass %. The flux also contains 0-20 mass % of a block organic acid and 0-3 mass % of an activator.

Thermally conductive adhesive materials having a first metallic component with a high melting point metal; a second metallic component having a low melting point metal; a fatty acid, an optional amine, an optional triglyceride and optional additives. Also provided are methods of making the same and uses thereof for adhering electronic components to substrates.

The present invention employs a flux which contains rosin, a solvent, a thixotropic agent and an activator. The thixotropic agent contains a polyamide (PA2). The PA2 is a condensation product of an aliphatic carboxylic acid, a hydroxy group-containing aliphatic carboxylic acid and an aliphatic amine having from 3 to 10 carbon atoms; and the aliphatic carboxylic acid includes an aliphatic dicarboxylic acid having from 11 to 20 carbon atoms. With respect to the endothermic amount calculated from the peak area of the differential scanning calorimetry curve of PA2 as obtained by differential scanning calorimetry measurement, the ratio of the endothermic amount within the range of from 50° C. to 190° C. to the total endothermic amount within the range of from 50° C. to 200° C. is 90% or more.

A flux according to the present invention is a flux for soldering, the flux including: an unsaturated aliphatic alcohol having one unsaturated bond, a thixotropic agent, and a solvent, in which the unsaturated aliphatic alcohol includes oleyl alcohol, and a content of the oleyl alcohol is 2.0 mass % or more and 12.0 mass % or less based on the entire flux.