Low-silver-content solder alloy and solder paste composition

Abstract

This low-silver-content solder alloy comprises 0.05-2.0 mass% of silver, 1.0 mass% or less of copper, 3.0 mass% or less of antimony, 2.0 mass% or less of bismuth, 4.0 mass% or less of indium, 0.2 mass% or less of nickel, 0.1 mass% or less of germanium and 0.5 mass% or less of cobalt (wherein the content of each of the above-mentioned elements copper, antimony, bismuth, indium, nickel, germanium and cobalt is not 0 mass%), with the remainder being tin. According to the present invention, it becomes possible to provide a low-silver-content solder alloy which has a reduced Ag content and therefore can be produced at reduced cost, has excellent stretching properties, an excellent melting point, excellent strength and the like, and also has high fatigue resistance (cold thermal fatigue resistance) and long-lasting reliability.

Description

technical field [0001] The present invention relates to a low-silver solder alloy, in particular, to Sn-Ag-Cu (tin-silver-copper) used for solder bonding of circuit elements and the like to circuit substrates such as printed circuit substrates of electronic devices. ) are solder alloys and solder paste compositions. Background technique [0002] Generally, as a solder alloy used for metal bonding of electric or electronic devices, a solder alloy containing Pb (lead) (for example, a solder alloy containing 63% by mass Sn and 37% by mass Pb) is generally used. However, the impact of lead on the environment is a matter of concern. [0003] Recently, various lead-free solder alloys have been considered, such as Sn-Cu-based alloys, Sn-Ag-Cu-based alloys (Patent Documents 1-3), Sn-Bi (bismuth)-based alloys, Sn-Zn (zinc)-based alloy (Patent Document 4), each of which does not contain lead. [0004] Patent Document 1 discloses a solder ball in which one, two or more selected from...

AI Technical Summary

Problems solved by technology

However, Ag contained in Sn-Ag-Cu-based alloys is expensive and increases the cost, thus constituting a major obstacle to the promotion of Sn-Ag-Cu-based alloys (lead-free solders)

[0009] Although it is possible to reduce the Ag content, the fatigue resistance (in particular, thermal fatigue resistance) deteriorates due to a small reduction in the Ag content, causing poor connection and the like

Attempts to further increase the strength of Sn-Ag-Cu-based alloys cause problems, namely, deteriorated elongation, increase in melting point, etc.

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