Lead free solder paste and application thereof

Abstract

A solder paste composed of solder alloy powder and flux, the volume expansion rate of which is 0.5% or less when the solder alloy is melted, and the flux contains bisphenol A type epoxy resin and a hardening agent selected from carboxylic anhydrides and dicarboxylic acids agent, the solder paste can be used for high temperature solder applications. In terms of mass%, the solder alloy has the following alloy composition: 70-98 mass% of Bi; 0-0.5% of Ag, Cu, Sb, In, Zn, Ni, Cr, Fe, Mo, P, Ge and One or more elements selected from Ga; the balance is composed of Sn.

Description

technical field [0001] The invention relates to a lead-free solder paste suitable for soldering electronic components. Although the solder alloy used has a low melting point itself, the solder paste of the present invention can also be used in applications where existing high-temperature solders are suitable. Moreover, this invention also relates to the soldering method of the electronic component using this solder paste, and an electronic component. Background technique [0002] Conventionally, Pb-63Sn alloy (in this specification, the meaning of the number indicating the alloy composition means mass %), that is, eutectic solder, has been mainly used for soldering of electronic components. The melting point of eutectic solder (because it is eutectic solder, the solidus temperature and liquidus temperature are the same) is low at 183°C. Generally, the liquidus temperature of the solder +20-50°C is considered to be a reasonable brazing temperature, so the brazing temperatur...

AI Technical Summary

Problems solved by technology

Usually it needs to be heated at 130-160°C for about 30 minutes to harden the resin, which seriously hinders the production efficiency due to the long time spent

[0018] In addition, the solder alloys in the composition range of Sn-30 to 57Bi used in the examples of Patent Document 4 have temperatures close to the solidus and liquidus Therefore, when remelting in secondary soldering, if force is applied, not only the primary soldering part is easily damaged, but also the primary soldering part may be completely melted due to the heat of the electronic device.

Furthermore, compared with 63Sn-Pb eutectic solder, the silver plating layer or Ag-Pd plating layer covering the Cu electrode of the electronic component of this solder alloy is easily melted into the solder, so that the Cu electrode will be corroded during the current conduction.