As electronic equipment has become smaller in size, printed circuit boards which cannot be subjected to cleaning have been developed, and a no-clean lead-free solder paste is becoming necessary. In order for a solder paste not to require cleaning, it is necessary that the color of the residue be transparent and that the residue be non-tacky. A maleated rosin, which is a rosin suited for no-clean paste, has a high acid value so it is not suitable for a flux for lead-free solder. As a means of suppressing a reaction between a flux containing a maleated rosin and a Sn—Ag—Cu based solder alloy powder, a Sn—Ag—Cu—Sb based solder alloy powder is used which adds 1-8 mass % of Sb to a Sn—Ag—Cu based solder alloy. As a result, it is possible to provide a solder paste which has the excellent effect that the solder paste does not easily undergo changes over time and has a long pot life.

The invention relates to a paste, preferably for joining components of power electronics modules, the paste comprising a solder powder, a metal powder and a binder, wherein the binder binds solder powder and metal powder before a first heating. According to the invention, the binder is free of flux or is a flux having only low activation. In this way, a joining layer which exhibits only few included voids and good mechanical and electrical stability can be provided between a first and a second component.

The present invention is directed to flux compositions and uses thereof. One composition comprises an activator and a solvent being a glycerol ethoxylate with a molecular weight of 200-500. Another composition comprises an activator, a solvent being a glycerol ethoxylate with a molecular weight of 200-500 and an amine. A soldering method for joining objects is also provided, comprising the steps of applying a flux composition to at least a portion of one or more of the objects, and joining the objects.

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 lead—free solder wire includes a core wire with a first alloy and a shell coating layer with a second alloy. The first alloy may be composed of Bi—Ag, Bi—Cu, Bi—Ag—Cu, or Bi—Sb; and the second alloy may be composed of Sn, In Sn—Ag, Sn—Cu, Sn—Ag—Cu, Sn—Zn, Bi—Sn, Sn—In, Sn—Sb or Bi—In, such that the shell coating layer is applied to a surface of the core wire. In another implementation, the lead free solder wire may include a first wire with a first alloy and a second wire with a second alloy. The first alloy may be composed of Bi—Ag, Bi—Cu, Bi—Ag—Cu, or Bi—Sb; and the second alloy may be composed of Sn, Sn—Ag, Sn—Cu, Sn—Ag—Cu, Sn—Zn, Bi—Sn, Sn—In, Sn—Sb or Bi—In, such that the first alloy of the first wire and the second alloy of the second wire are braided together.

A solder alloy has an alloy composition containing Zn of 3 through 25 mass %, Ti of 0.002 through 0.25 mass %, Al of 0.002 through 0.25 mass % and balance of Sn, a solder joint made of the solder alloy, and a jointing method using the solder alloy.

Provided are a lead-free solder alloy which consists of Sb in an amount of more than 3.0% but 10% or less by mass, and the balance including Sn, and others.

In a lead-free solder bump, diffusion of Cu from intermetallic compound layers, which are respectively formed at joining interfaces with Cu electrodes is suppressed, so that the in metallic compound layers are not likely to disappear. Correspondingly, with the use of the intermetallic compound layers, Cu is not likely to diffuse from the Cu electrodes into the lead-free solder bump. Even when an electric current flows continuously between a first electronic member and a second electronic member through the lead-free solder bump, the occurrences of the electromigration phemenon and the thermomigration phenomenon are suppressed. Thus, the present invention provides a lead-free solder bump joining structure capable of suppressing the disconnection failure caused by the synergistic effect of the electromigration phenomenon and the thermomigration phenomenon.

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.