Method for manufacturing SnAgCu lead-free solder

Abstract

The invention discloses a method for manufacturing SnAgCu lead-free solder, which comprises the following steps of: mixing raw materials according to proportions, heating to 500 DEG C under the protection of a covering agent and nitrogen gas or under the vacuum condition, smelting for 0.5-1h to obtain alloy melt; heating the alloy melt to a temperature not lower than a temperature range that the alloy melt generates liquid-state structure transformation, and preserving heat for 15-30min; cooling to 500 DEG C, preserving heat for 0.5h, and then casting and solidifying to obtain a lead-free solder alloy ingot; and finally machining the alloy ingot into lead-free solder by adopting a transmission machining way. According to the lead-free solder prepared by adopting the method disclosed by the invention, solidification tissues are remarkably thinned and evenly distributed; in the welding process, a reaction layer at the joint part is remarkably thinned and the roughness is reduced; the solder is easy to melt, and the expandability of the solder and the wettability of the solder with a copper substrate are remarkably improved; besides, the thermal stability of welding joint tissues is remarkably improved, and therefore the operation reliability of related products in the service process is improved.

Description

1. Technical field [0001] The invention relates to a preparation method of lead-free solder, in particular to a preparation method of SnAgCu ternary alloy lead-free solder. 2. Background technology [0002] Tin-lead (Sn-Pb) metal solder (welding rod, welding wire, solder paste, etc.) has been widely used in various countries due to its superior performance, good process performance and low cost, such as various electronics (computers, monitors, Color TVs, mobile phones, etc.), electrical appliances and instrument products, microelectronic packaging, printed circuit board (PCB) assembly, including plug-in (THT) and surface mount (SMT). However, because e-waste containing harmful substances such as lead has great harm to human beings, and lead poisoning can induce diseases such as leukemia, kidney disease, heart disease, and mental disorders, it has become the consensus of all mankind to ban lead. The EU WEEE and RoHS directives (6 hazardous substances such as Pb banned in el...

AI Technical Summary

Problems solved by technology

In this way, the melt structure in the droplet has a significant impact on the growth of the weld reaction layer. The size of the clusters in the solder droplet by the conventional smelting preparation method is relatively large, especially the adhesion of the Sn-Cu solid clusters to the substrate is beneficial to the intermetallic formation. Compound Cu 6 sn 5 The nucleation grows, and the reactant growth interface appears rough, which further promotes the thickening of the reaction layer; at the same time, the viscosity of the droplet is larger due to the larger cluster size, which is not conducive to the flow and spreading on the rough reactant interface

In conclusion, on the one hand, the spreading and wettability of the solder prepared by the conventional method needs to be further improved; on the other hand, the weld reaction layer is relatively thick, and the interface with the solder is relatively rough, and structural defects are prone to occur, which is unfavorable to the reliability of the weld.

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