A solder composition of the invention includes: a flux composition containing a component (A) in a form of a rosin-based resin, a component (B) in a form of an activator, a component (C) in a form of a solvent and a component (D) in a form of a thixotropic agent; and a component (E) in a form of a solder powder. The component (C) in a form of the solvent contains a component (C1) in a form of a isobornyl cyclohexanol and a component (C2) in a form of a solvent whose viscosity at 20 degrees C. is 10 mPa.Math.s or less and whose boiling point ranges from 220 degrees C. to 245 degrees C.

One aspect of the present invention is a method for manufacturing an electronic component, the method including: a first step of applying a metal paste containing metal particles onto a polymer compact in a prescribed pattern to form a metal paste layer; a second step of sintering the metal particles to form metal wiring; a third step of applying a solder paste containing solder particles and a resin component onto the metal wiring to form a solder paste layer; a fourth step of disposing an electronic element on the solder paste layer; and a fifth step of heating the solder paste layer so as to form a solder layer bonding the metal wiring and the electronic element, and so as to form a resin layer covering at least a portion of the solder layer.

A lead-free solder ball is provided which suppresses interfacial peeling in a bonding interface of a solder ball, fusion defects which develop between the solder ball and solder paste, and which can be used both with Ni electrodes plated with Au or the like and Cu electrodes having a water-soluble preflux applied atop Cu. The lead-free solder ball for electrodes of BGAs or CSPs consists of 1.6-2.9 mass % of Ag, 0.7-0.8 mass % of Cu, 0.05-0.08 mass % of Ni, and a remainder of Sn. It has excellent resistance to thermal fatigue and to drop impacts regardless of the type of electrodes of a printed circuit board to which it is bonded, which are Cu electrodes or Ni electrodes having Au plating or Au/Pd plating as surface treatment. The composition may include at least one element selected from Fe, Co, and Pt in a total amount of 0.003-0.1 mass % or at least one element selected from Bi, In, Sb, P, and Ge in a total amount of 0.003-0.1 mass %.

Provided is a lead-free solder alloy for terminal preliminary plating, by which the separation property when pulling up the terminals from molten solder is improved. The lead-free solder alloy for terminal preliminary plating contains 4 mass % or more and 6 mass % or less of Cu, 0.1 mass % or more and 0.2 mass % or less of Ni, 0.01 mass % or more and 0.04 mass % or less of Ga, 0.004 mass % or more and 0.03 mass % or less of P, and a remainder of Sn, a total amount of Ga and P being 0.05 mass % or less. Its tension in a melted condition by heating in soldering temperature is 200 dyn/cm or less.

A solder-coated ball (10A) includes a spherical core containing Ni and P; and a solder layer (12) formed to coat the core (11). A solder-coated ball (10B) further includes a Cu plating layer (13) formed between the core (11) and the solder layer (12). A solder-coated ball (10C) further includes an Ni plating layer (14) formed between the Cu plating layer (13) and the solder layer (12).

In a solder alloy consisting essentially of tin, silver, copper, bismuth, antimony, indium, and nickel, the content ratio of the silver is 0.05 mass % or more and below 0.2 mass %; the content ratio of the copper is 0.1 mass % or more and 1 mass % or less; the content ratio of the bismuth is above 4.0 mass % and 10 mass % or less; the content ratio of the antimony is 0.005 mass % or more and 8 mass % or less; the content ratio of the indium is 0.005 mass % or more and 2 mass % or less; the content ratio of the nickel is 0.003 mass % or more and 0.4 mass % or less; and the content ratio of the tin is the remaining ratio and the mass ratio (Bi/Ni) of the bismuth content with respect to the nickel content is 35 or more and 1500 or less.

The present invention provides a solder alloy, a solder paste, a solder ball, a resin flux-cored solder and a solder joint, both of which has the low-melting point to suppress the occurrence of the fusion failure, improves the ductility and the shear strength, and has excellent heat-cycle resistance. The solder alloy comprises an alloy composition composed of 35 to 68 mass % of Bi, 0.1 to 2.0 mass % of Sb, 0.01 to 0.10 mass % of Ni, and a balance of Sn. The alloy composition may contain at least one of Co, Ti, Al and Mn in total amount of 0.1 mass % or less. The solder alloy may be suitably used for a solder paste, a solder ball, a resin flux-cored solder and a solder joint.

An approach to provide an electronic assembly process that includes receiving at least one electronic assembly after a solder reflow process using a Sn-containing solder and a water-soluble flux. The approach includes baking the at least one electronic assembly in an oxygen containing environment and, then cleaning the at least one electronic assembly in an aqueous cleaning process.

There is a problem that contact resistance increases due to formation of an oxide film on a contact interface or biting of abrasion powder caused by micro-sliding when a contact connecting portion of a connection terminal including non-noble metal members is exposed to high temperature environment or a repetitious temperature cycle. An object of the present invention is to provide an in-vehicle electronic module that has connection reliability equivalent to that of the conventional in-vehicle electronic module even when being placed in the environment of an engine compartment and can achieve cost reduction by reducing the number of parts and assembly steps. The electronic module includes a mounting board having a circuit board on which an electronic component is mounted, and a case member for accommodating and protecting the mounting board from surrounding environment, The electronic module has a connection structure in which a portion of the circuit board is protruded to the outside through an opening of the case and inserts a board terminal into an external female connector to obtain electrical continuity, and a portion of the case member forms a connector housing that receives the female connector and isolates a space in which the board terminal is present from surrounding environment and an insulating resin member for fixing the circuit board in the case is integrally molded or joined with the circuit board.

A lead-free solder alloy having a low melting temperature and low yield strength is disclosed. The solder alloy includes 5.0-20.0 wt. % of indium (In), 1.0-5.0 wt. % of silver (Ag), 0.25-2.0 wt. % of copper (Cu), 0.1-0.5 wt. % of zinc (Zn), and a remainder of tin (Sn). In implementations, a sulfur compound may be included in a concentration of 100 ppm to 500 ppm in the alloy to prevent oxidation of zinc and indium on the surface of the alloy. The solder alloy is particularly useful for but not limited to solder on pad applications in first level interconnect semiconductor device packaging.