Low-silver lead-free solder and preparation method thereof

Abstract

The invention discloses a low-silver lead-free solder and a preparation method thereof. The low-silver lead-free solder consists of metal element components including, by weight, Ag 0.1%-1%, Cu 0.1%-1%, misch metal 0.01%-0.10% and the balance tin, wherein Ce accounts for 50%, La accounts for 25%, Nd accounts for 15% and Pr accounts for 10% in the misch metal. On the metal purity aspect, Ce >= 99.99%, La>= 99.99%, Nd >= 99.99%, Pr >= 99.99%, and Sn, Ag and Cu are industrial refined raw materials. The low-silver lead-free solder does not contain lead and can meet the lead-free welding requirement of electronic products. Branch-shaped primary-phase solid-liquid mixed slurry is crushed in an acute stirring mode in the low-silver hypo eutectic alloy solidification process, and a water-cooling casting forming mode is adopted to improve mechanical property, especially the plastic property. A rare earth alterant is adopted to achieve grain refinement, improve the wet performance of the solder and ensure long-term reliability of welding points.

Description

technical field [0001] The invention belongs to the field of new materials, and relates to a low-silver lead-free solder and a preparation method thereof. Background technique [0002] The eutectic alloy Sn96.5Ag3Cu0.5 (SAC305) has been widely used in the electronics industry as a substitute for tin-lead, but the content of Ag in the solder is high, and Ag is a noble metal, which accounts for almost 1 / 2 of the cost of the SAC305 alloy, and the cost greatly restricts it. Development of lead-free materials and techniques for electronic soldering. The hypoeutectic solder has a low silver content and has the best cost performance and has attracted widespread attention. However, the solid-liquidus range of the hypoeutectic solder is relatively large (8-10 ℃), and the alloy structure contains dendritic primary βSn phase and lamellar Ag 3 Sn metal compounds, resulting in poor solder wettability, mechanical properties and solder joint reliability. [0003] Patent No. CN102029479...

AI Technical Summary

Problems solved by technology

[0004] Aiming at the high cost of eutectic alloys and the shortage of low-silver alloys, the present invention provides a low-silver lead-free solder and its preparation method, which can obtain fine-grain uniform structure, improve the mechanical properties of the alloy, improve the wettability of the solder, and improve the reliability of solder joints. sex

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