Zn (zinc) based high-temperature lead-free soft solder and preparation method for same

Abstract

The invention belongs to the technical field of soldering such as electronic package, assembly and the like of soldering fluxes, and particularly discloses Zn (zinc) based high-temperature lead-free soft solder and a preparation method for the same. In weight percent, components of the Zn based high-temperature lead-free soft solder include 2-30% of aluminum, 1-20% of tin, 0.1-8% of copper, 0.01-3.0% of titanium, 0.1-1.0% manganese and / or 0.1-1.0% of lanthanum-cerium rare earth and the balance zinc. The melting point of the Zn based high-temperature lead-free soft solder ranges from 250 DEG C to 450 DEG C, and the Zn based high-temperature lead-free soft solder has the advantages of fine wetting spreadability and high in tensile strength. The mechanical property of the Zn based high-temperature lead-free soft solder is superior to corresponding high-lead solder, the spreadability of the Zn based high-temperature lead-free soft solder meets the use requirement of soldering, and the Zn based high-temperature lead-free soft solder can replace the high-lead solder widely applied at present and meets the requirements of soldering such as high-temperature electronic package, assembly and the like.

Description

technical field [0001] The invention relates to the technical field of brazing such as electronic packaging and assembly, in particular to a Zn-based high-temperature lead-free solder and a preparation method thereof. Background technique [0002] At present, the high-temperature solder mainly uses the traditional lead-based solder and gold-based solder. Lead-based solder alloy is a eutectic alloy formed of lead and tin, gold, silver, antimony and other metals, and its melting point is 250-360 °C. Lead-based solders are softer and can absorb strain due to thermal expansion mismatch between the chip and substrate, but are less strong. If the lead-based solder brazing joint is subjected to multiple thermal cycles, strain accumulation will occur at the grain boundaries of the solder, microcracks will occur, and eventually fatigue failure will be caused. Therefore, lead-based solder cannot be used in occasions that require high connection strength. Gold-based solder is mainly ...

AI Technical Summary

Problems solved by technology

Gold-based solder usually uses the eutectic system of Au-20Sn, Au-30Si and Au-26Ge as the solder, but because Au-Sn will form AuSn 4 Intermetallic compounds, which are very brittle, seriously affect the reliability of gold-based solder in service, and the cost of gold-based solder is also too high

European patent EP1705258A2 has proposed a kind of Ag containing 2%-18wt%, Bi is 98-82wt%, and contains 0.1-5.0wt% trace element Au, Cu, yt, Sb, Zn, Sn, Ni and Ge Bi -Ag-X alloy solder to replace high-lead solder. The Bi-Ag-X alloy solder has a suitable melting point and a solidus temperature greater than 262.5°C, but the alloy solder has high brittleness, poor processability, and bonding strength with the substrate. A series of problems such as weak, wide solid-liquid phase interval and poor wettability on Cu and Ni substrates

Chinese patent CN1221216A proposes a Sn-Sb binary alloy solder containing 5-15% Sb to coat the lead frame to ensure that it can withstand the subsequent higher temperature sealing process, but the Sn-Sb binary alloy When the Sb content of the solder is low, for example, less than 10%, the melting point of the Sn-Sb binary alloy solder is relatively low, which is unfavorable for the reliability of the solder joints that need to withstand high temperature packaging processes, and the alloy solder exists to Cu or Ni The problem of fast dissolution of the base pad

US Patent 20040241039 proposes a solder containing at least 5% Sn, 0.5-7% Cu, and 0.05-18% Sb. Chinese patent CN1954958A also proposes a solder containing 8-20% Sb. 3-7% Cu, and the rest is 5% Sn. Although these two patent applications all propose to use the ternary alloy of SnSbCu as high-temperature lead-free solder, this series of alloys has poor oxidation resistance. A large amount of tin slag will be produced in the alloy, and the alloy still has the problem of fast dissolution of the Cu or Ni substrate pad