Some implementations of the disclosure are directed to a thermal interface material. In some implementations, a method comprises: applying a solder paste between a surface of a heat generating device and a surface of a heat transferring device to form an assembly; and reflow soldering the assembly to form a solder composite, wherein the solder composite provides a thermal interface between the heat generating device and the heat transferring device, wherein the solder paste comprises: a solder powder; particles having a higher melting temperature than a soldering temperature of the solder paste, wherein the solder paste has a volume ratio of solder powder to high melting temperature particles between 5:1 and 1:1.5; and flux.

A lead-free solder alloy may comprise tin, silver, copper, bismuth, cobalt, and antimony. The alloy may further comprise nickel. The silver may be present in an amount from about 2.0% to 2.8% by weight of the solder. The copper may be present in an amount from about 0.2% to 1.2% by weight of the solder. The bismuth may be present in an amount from about 0.0% to about 5.0% by weight of the solder. In some embodiments, the bismuth may be present in an amount from about 1.5% to 3.2% by weight of the solder. The cobalt may be present in an amount from about 0.001% to about 0.2% by weight of the solder. The antimony may be present in an amount between about 0.0% to about 0.1% by weight of the solder. The balance of the solder is tin.

A semiconductor device includes: a package including: a lower surface, at least one first metal surface at an outer periphery of the lower surface, and at least one second metal surface at the lower surface at a location different from the at least one first metal surface; a mounting substrate disposed below the package and including: an upper surface, at least one first metal pattern disposed at the upper surface below the at least one first metal surface, and at least one second metal pattern disposed at the upper surface below the at least one second metal surface; a first bonding member containing a metal material and bonding the at least one first metal surface and the at least one first metal pattern; and a second bonding member containing a metal material and bonding the at least one second metal surface and the at least one second metal pattern.

A solder alloy has an alloy composition consisting of, in mass %, Ag: 0 to 4%, Cu: 0.1 to 1.0%, Ni: 0.01 to 0.3%, Sb: 5.1 to 7.5%, Bi: 0.1 to 4.5%, Co: 0.001 to 0.3%, P: 0.001 to 0.2%, and the balance being Sn.

In a layered bonding material 10, a coefficient of linear expansion of a base material 11 is 5.5 to 15.5 ppm/K and a first surface and a second surface of the base material 11 are coated with pieces of lead-free solder 12a and 12b.

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.

Provided is a lead-free solder alloy that has excellent tensile strength and ductility, does not deform after heat cycles, and does not crack. The In and Bi content are optimized and the Sb and Ni content are adjusted. As a result, this solder alloy has an alloy composition including, by mass, 1.0 to 7.0% of In, 1.5 to 5.5% of Bi, 1.0 to 4.0% of Ag, 0.01 to 0.2% of Ni, and 0.01 to 0.15% of Sb, with the remainder made up by Sn.

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.

PROBLEM: To provide a multi-layer preform sheet capable of forming a highly reliable and high-quality electric interconnect, an electro-conductive bonding portion and so forth that are less likely to produce the Kirkendall void.

SOLUTION: A multi-layer preform sheet having at least a first layer and a second layer, the first layer being composed of a solder material that contains an intermetallic compound, and the second layer containing a first metal having a melting point of 300° C. or above, and a second metal capable of forming an intermetallic compound with the first metal.

Solder paste consisting of 85 to 92% by weight of a tin-based solder and 8 to 15% by weight of a flux, wherein the flux comprises i) 30 to 50% by weight, based on its total weight, of a combination of at least two optionally modified natural resins, ii) 5 to 20% by weight, based on its total weight, of at least one low-molecular carboxylic acid; and iii) 0.4 to 10% by weight, based on its total weight, of at least one amine, and wherein the combination of the optionally modified natural resins has an integral molecular weight distribution of 45 to 70% by area in the molecular weight range of 150 to 550 and of 30 to 55% by area in the molecular weight range of >550 to 10,000 in the combined GPC.