ZnSn-base high-temperature lead-free soft solder and preparation method thereof

Abstract

The invention belongs to the technical field of braze soldering flux for electronic packaging and assembly, and discloses a ZnSn-base high-temperature lead-free soft solder and a preparation method thereof. The ZnSn-base high-temperature lead-free soft solder consists of the following components in percentage by weight: 15 to 40 percent of tin, 0.5 to 8 percent of copper, 0.1 to 1 percent of lanthanum and neodymium mixed rare earth, 0.1 to 3 percent of magnesium and/or 0.1 to 2 percent of bismuth and the balance of zinc. The ZnSn-base high-temperature lead-free soft solder has the advantages of no toxicity and no pollution, is high in wetting spreadability and high in tensile strength and mechanical property, and can meet the using requirement of brazing and replace high-lead solders which are applied widely at present or Au-base solders with high price to meet the requirements of the fields of electronic packaging and assembly; and a melting point is between 250 and 450 DEG C.

Description

technical field [0001] The invention relates to the technical field of brazing solder for electronic packaging and assembly, in particular to a ZnSn-based high-temperature lead-free solder and a preparation method thereof. Background technique [0002] SnPb solder has the advantages of relatively low melting point, low price, beautiful shape and rich raw materials. It is the most widely used in electronic packaging and assembly. However, Pb is poisonous. Countries around the world have legislated to restrict the use of Pb-containing solder. On February 13, 2003, the European Union officially passed the ROSH Directive and the Waste Electrical and Electronic Equipment (WEEE), which clearly stipulated that the use of lead in the electronics industry should be gradually restricted, and lead-containing solders should be banned from January 1, 2006. The Ministry of Trade of Japan will completely exclude six harmful substances including lead from electronic equipment from July 1, 2...

AI Technical Summary

Problems solved by technology

[0003] At present, high-temperature solders mainly use traditional lead-based solders and gold-based solders, but lead-based solders have poor mechanical properties and cannot meet the use requirements in places with high connection strength requirements.

Gold-based solders such as Au-20Sn, Au-30Si and Au-26Ge are easy to form brittle AuSn 4 Intermetallic compounds seriously affect the reliability of its service, and the cost of solder is extremely high, so it is imperative to research and develop low-cost and high-strength lead-free high-temperature solder products

European patent EP1705258 proposes a kind of Bi-Ag-X alloy solder to replace high Pb solder at present, and its composition is as follows: the weight percent content of Ag is 2-18%, and the weight percentage content of Bi is 98~82% , and the trace elements Au, Cu, Sb, Zn, Sn, Ni and Ge with a weight percentage content of 0.1-5.0%. The disadvantages of this Bi-Ag-X alloy solder are high brittleness and poor processability

Chinese patent CN1221216 proposes a kind of Sn-Sb solder containing Sb5-15%, but when Sb content is low such as less than 10% in this solder, the melting point of Sn-Sb binary alloy solder is relatively low, high temperature Poor reliability, and Cu or Ni base pads have corrosion problems

Chinese patent CN1954958 also proposes a kind of SnSbCu solder, is made up of 8-20% Sb, 3-7% Cu and 5% Sn, and this SnSbCu solder alloy has poor oxidation resistance, and will be damaged during high-temperature welding process. generate a lot of dross

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